Papers for Wednesday, Sep 24 2025

In this study, we classify the magnetic chirality of solar filaments from H-Alpha observations using state-of-the-art image classification models. We establish the first reproducible baseline for solar filament chirality classification on the MAGFiLO dataset. The MAGFiLO dataset contains over 10,000 manually-annotated filaments from GONG H-Alpha observations, making it the largest dataset for filament detection and classification to date. Prior studies relied on much smaller datasets, which limited their generalizability and comparability. We fine-tuned several pre-trained, image classification architectures, including ResNet, WideResNet, ResNeXt, and ConvNeXt, and also applied data augmentation and per-class loss weights to optimize the models. Our best model, ConvNeXtBase, achieves a per-class accuracy of 0.69 for left chirality filaments and $0.73$ for right chirality filaments.

The Trinity Neutrino Observatory aims to detect tau neutrinos in the energy range of 1 PeV to 10 EeV. We are developing the observatory in three stages. The first stage, known as the Trinity Demonstrator, was deployed in Fall 2023. The Demonstrator serves as a pathfinder for the full observatory and will inform the design of the first Trinity Telescope. We discuss the status and initial results of the Trinity Demonstrator. In 346 hours of observations with the Demonstrator, we do not identify a neutrino candidate event.

Following the Trinity Demonstrator, Trinity One will be the first of the 18 Cherenkov telescopes that make up the Trinity PeV-Neutrino Observatory. Located on Frisco Peak in Utah, Trinity One can observe 64\% of the sky, allowing it to detect potential neutrino point sources with unprecedented sensitivity, ranging from 1 PeV to 10 EeV. We outline the design of Trinity One, which features a 60 m$^2$ light-collection surface and the ability to rotate in azimuth. It has a field of view measuring $5^\circ$ by $60^\circ$, which is equipped with a silicon photomultiplier camera with a resolution of $0.3^\circ$. Utilizing the design of Trinity One, we present performance calculations in relation to various source classes.

The $\gamma$-ray emission from active galactic nuclei (AGN), including both beamed blazars and misaligned-AGN, dominates the extragalactic $\gamma$-ray point-source population count and flux. While multi-wavelength studies have detected an increasing number of AGN within dwarf galaxies in the local Universe, $\gamma$-ray emission has so far only been associated with systems hosting supermassive black holes (SMBHs). Dwarf-galaxy AGN are of particular interest because their central black holes fall in the intermediate-mass black hole (IMBH) regime, offering insight into the early evolution of SMBHs. Using 15~years of \textit{Fermi}-LAT data, we present the first search for $\gamma$-ray emission from dwarf-galaxy AGN. In the sample of 74 X-ray-selected dwarf-galaxy AGN, we find no sources that exceed the \textit{Fermi}-LAT detection threshold. However, a joint-likelihood analysis reveals a modest, trials-corrected population-level excess ($\sim2\sigma$) above blank-field expectations at very soft photon indices $\Gamma \gtrsim 3.8$ above 500~MeV. This hint is most pronounced when source contributions are weighed by $M^\alpha_{{\rm IMBH},i}/d_i^2$, with $\alpha\simeq1$--$1.5$, suggesting -- but not confirming -- that $\gamma$-ray emission could scale with the central black hole mass or a property correlated with it (e.g., accretion rate), but with a markedly softer spectrum than in SMBH-hosted AGN.

Galaxy clusters, the most massive, dark-matter-dominated, and most recently assembled structures in the Universe, are key tools for probing cosmology. However, uncertainties in scaling relations that connect cluster mass to observables like X-ray luminosity and temperature remain a significant challenge. In this paper, we present the results of an extensive investigation of 329 simulated clusters from Illustris TNG300 cosmological simulations. Our analysis involves cross-correlating dark matter and the hot X-ray-emitting gas, considering both the 3D and 2D projected distributions to account for projection effects. We demonstrate that this approach is highly effective in evaluating the dynamical state of these systems and validating the often-utilized assumption of hydrostatic equilibrium, which is key for inferring cluster masses and constructing scaling relations. Our study revisits both the X-ray luminosity-mass and X-ray temperature-mass scaling relations, and demonstrates how the scatter in these relations correlates with the clusters' dynamical state. We demonstrate that matter-gas coherence enables the identification of an optimal set of relaxed clusters, reducing scatter in scaling relations by up to 40%. This innovative approach, which integrates higher-dimensional insights into scaling relations, might offer a new path to further reduce uncertainties in determining cosmological parameters from galaxy clusters.

OJ 287 is the best-known supermassive black hole binary candidate in the nanohertz gravitational wave band. It exhibits periodic flares every $\sim$ 12 years, likely caused by collisions of a smaller-mass secondary with the accretion disk surrounding a larger-mass primary. It is therefore an important benchmark for understanding black hole binary accretion in the approaching era of space-based gravitational wave detectors and large electromagnetic surveys. Because the electromagnetic emission of the system is determined by a complex interplay of plasma, accretion, and radiation physics in strong gravity, numerical simulations are required for realistic modeling. We present the first global, three-dimensional, general relativistic magnetohydrodynamic (GRMHD) simulations of OJ 287-like systems; namely, smaller-mass secondaries colliding with a radiatively-cooled (thin) disk surrounding a larger-mass primary. We focus on disks with scale heights that are 10\% of the distance from the primary and binary mass ratios of $q = 0.1,0.05$, and $0.025$ using an optically-thin cooling prescription. We confirm the basic paradigm that impacts of the secondary on the disk can generate enough power to outshine the quiescent emission. The secondary also causes spiral shocks to form in the disk, enhanced accretion events, overall heating of the flow, and stochastic tilting of the disk, though these effects are small for $q<0.05$. Our results can be extrapolated to the parameters of OJ 287 and similar systems, an important step on the path toward fully realistic simulations of accretion onto small-mass-ratio black hole binaries and predicting electromagnetic counterparts to low-frequency gravitational wave detections.

Finding low-mass planets around solar-type stars requires to understand the physical variability of the host star, which greatly exceeds the planet-induced radial-velocity modulation. This project aims at analyzing - observationally and theoretically - the character and physical origins of fluctuations in solar photospheric absorption lines. Observationally, photospheric equivalent-width variations were measured in 1000 selected spectra from three years of HARPS-N data of the Sun-as-a-star, showing changes that largely shadow the chromospheric CaII H&K activity-cycle signal, but with much smaller amplitudes on sub-percent levels. Among iron lines, the greatest are for FeII in the blue, while the trends change sign among lines in the green MgI triplet and between Balmer lines. No variation was seen in the semi-forbidden MgI 457.1 nm. Theoretically, hydrodynamic 3D modeling of solar surface convection produced time sequences of synthetic high-resolution spectral atlases. Radial velocities averaged over small simulation areas jitter by some +-150 m/s, scaling to 2 m/s for the full solar disk on timescales of granular convection. Among different lines, jittering is in phase, but amplitudes differ by about one tenth of their values: greater for stronger and for ionized lines, decreasing at longer wavelengths.

Gravitational wave observations can be combined with galaxy catalogs to constrain cosmology and test modified gravity theories using the standard siren method. However, galaxy catalogs are intrinsically incomplete due to observational limitations, potentially leaving host galaxies undetected and thereby weakening constraints or potentially introducing systematic errors. In this work, we present a self-consistent framework to study catalog incompleteness and host weighting effects, implemented in the publicly available CHIMERA pipeline. We obtain joint cosmological and astrophysical population constraints from 100 binary black hole (BBH) events in a LIGO-Virgo-KAGRA O5-like configuration, using spectroscopic galaxy catalogs with varying completeness levels and stellar-mass host weighting schemes. We find percent-level constraints on $H_0$ with complete catalogs, reaching precision of 1.6%, 1.3%, and 0.9% for constant, linear, and quadratic mass weighting, respectively. As completeness decreases, the precision degrades following a sigmoid trend, with a threshold and steepness that increase for stronger weightings. Simultaneously, the correlation between $H_0$ and the BBH population mass scale also increases, making results more sensitive to assumptions about the astrophysical population. Remarkably, 2% precision remains achievable when catalogs contain only 50% of the potential host galaxies within the gravitational wave detection horizon, while 1% precision requires host probabilities scaling with stellar mass squared. The results are robust against host weighting mismodeling, even at moderate completeness levels. This work further highlights the importance of spectroscopic galaxy surveys in standard siren cosmology and provides a pathway for developing the science case of future facilities.

Internal Gravity Waves (IGWs) are thought to cause mixing in stellar interiors, a process that has been widely studied both theoretically and numerically. Our aim is to determine the physical mechanism responsible for the wave-induced mixing in stellar interiors. We compare the mixing profiles obtained from two-dimensional (2D) equatorial hydrodynamical and tracer particle simulations with theoretical predictions from R. J. Garcia Lopez & H. C. Spruit (1991) and J. P. Zahn (1992) on wave mixing due to wave-induced shear turbulence. Our results show that, despite not satisfying the vertical shear instability threshold, the mixing profiles from the simulations agree remarkably well with the theoretical predictions of both prescriptions, strongly suggesting that shear from IGWs plays an important role in mixing even at low shear rates. This agreement remains robust across different stellar masses, ages, rotation and simulation parameters. This provides an important step in providing realistic parameterisations for wave mixing in stellar structure and evolution models.

Recent advancements in small-scale observations of the cosmic microwave background (CMB) have provided a unique opportunity to characterize the distribution of baryons in the outskirts of galaxies via stacking-based analyses of the kinetic Sunyaev-Zel'dovich (kSZ) effect. Such measurements, mathematically equivalent to probing the galaxy-electron cross-correlation, have revealed that gas is more extended than dark matter and that the strength of baryonic feedback may vary with halo mass and redshift. However, because these analyses are conditioned on galaxy positions, the inferred electron distributions remain biased by uncertain galaxy-halo modeling on small scales. In this work, we present a novel kSZ$\times$galaxy four-point estimator that directly probes the full ionized electron field, extending beyond the gas traced by luminous galaxies. This method exploits large-scale velocity reconstruction from galaxy surveys to characterize the electron distribution unbiased by small-scale galaxy clustering. We forecast that the proposed signal can be measured with a signal-to-noise ratio of $\sim3$ ($\sim13$) for a configuration corresponding to Atacama Cosmology Telescope DR6 (Simons Observatory) CMB data combined with spectroscopic galaxy samples from DESI. This approach will enable the first tomographic measurements of the electron auto-power spectrum, providing new constraints on baryonic feedback and its role in shaping cosmic structure.

We demonstrate the formation of magnetically arrested minidisks (MAM) around equal-mass, nonspinning binary black holes with magnetohydrodynamic simulations of circumbinary disk accretion in full 3+1 general relativity. The initial separation of $d\sim 30\,M$ allows the black holes to host large minidisks that suppress the total rest-mass accretion rate variability, which is modulated primarily at $\sim 1.6 \, f_{\rm orb}$. Each black hole horizon saturates with dimensionless magnetic flux $\phi \sim 30$. Magnetic reconnection near the horizons drives recurrent eruptions which are expected to drive flaring in the infrared and X-ray bands. Our results establish MAMs as a new outcome of circumbinary disk accretion, and a promising source of novel electromagnetic counterparts to gravitational waves from binary black holes.

Galaxies at Cosmic Noon (z$\sim$2-3) are characterized by rapid star formation that will lead to significant metal enrichment in the interstellar medium (ISM). While much observational evidence suggests that these galaxies are chemically distinct from those in the local Universe, directly measuring the ISM chemistry in large samples of high-z galaxies is only now possible with the observational capabilities of JWST. In this first key paper of the CECILIA program, we present the direct-method physical conditions and multi-element abundances in twenty galaxies at Cosmic Noon. Using a combination of archival Keck/MOSFIRE and new $\sim$30-hr NIRSpec spectroscopy, we measure multiple electron gas densities and the temperature structure from the O$^+$ and S$^{2+}$ ions. We find that n$_e$[O II] and n$_e$[S II] are comparable but elevated with respect to n$_e$ in local star-forming galaxies, and the simultaneous T$_e$[O II] and T$_e$[S III] generally agree with photoionization model T$_e$ scaling relations. The O abundances in the CECILIA galaxies range from 12+log(O/H)$=$7.76-8.78 (12-123% solar O/H), representing some of the highest direct-method metallicities and lowest T$_e$ measured with JWST to date. The CECILIA galaxies exhibit significantly sub-solar S/O and Ar/O, in agreement with emerging results from other high-z studies and a signature of predominant enrichment from core collapse supernovae. The N/O-O/H trends in the CECILIA galaxies generally agree with the abundance trends in local nebulae, but the large scatter in N/O could be sensitive to the star-formation history. The CECILIA observations underscore the need for exceptionally deep spectroscopy to unveil the ISM abundance patterns in high-z galaxies.

Previous studies of galaxy clusters have focused extensively on the effects of active galactic nuclei (AGN) feedback on the chemical evolution of the intra-cluster medium (ICM). However, similar studies on the atmospheres of lower mass systems, such as galaxy groups and giant ellipticals, remain limited. In this work, we present a systematic analysis of the chemical and multi-temperature structure of the intra-group medium (IGrM), using a subsample of nearby galaxy groups and ellipticals from the CHEERS catalogue. By comparing areas with and without AGN feedback related features, such as cavities or extended radio lobes, we find clear evidence of an excess of multi-phase gas along the path of recent AGN feedback. However, its distribution exceeds the length of the radio lobes, since we recover a non-negligible amount of multi-phase gas at larger radii. In contrast to the clear asymmetry in the thermal structure, we find no directional enhancement in the distribution of Fe, with little to no differences in the Fe abundances of the on- and off-lobe directions. Our analysis suggests that the metals in the IGrM of our targets are well-mixed and decoupled from the effects of recent AGN feedback, as indicated by radio-lobes and cavities.

We study the effects of varying different Active Galactic Nuclei (AGN) feedback parameters on the Lyman-$\alpha$ (Ly$\alpha$) forest 1D transmitted flux power spectrum (P1D). We use the Cosmological and Astrophysics with Machine Learning Simulations (CAMELS) suite to explore variations on the Simba simulation AGN feedback model. The parameters explored include AGN momentum flux, AGN jet speed, supermassive black hole (SMBH) radiative efficiency, jet velocity threshold, and minimum SMBH mass needed to produce jet feedback. Although all parameters affect the P1D, this work explores the radiative efficiency, jet velocity threshold, and minimum SMBH mass in this context for the first time and finds the following results: Primarily, the most massive SMBHs impact the Ly$\alpha$ forest through the jet feedback mode. While heating AGN jets to the virial temperature at injection aids in the removal of neutral hydrogen from the Ly$\alpha$ forest, this heating also inhibits further jet feedback. Similar behaviors are seen when varying the SMBH radiative efficiency, with higher values resulting in a suppression of SMBH growth and thus a later reduction in AGN feedback and lower values directly reducing the impact of AGN feedback on the Ly$\alpha$ forest P1D. These results imply that increasing the AGN feedback strength in the Simba simulation model suppresses the Ly$\alpha$ forest P1D, but only if the feedback does not impact the number of massive jet producing BHs. Future studies of AGN feedback models will require careful exploration of the unique aspects of the specific subgrid model, and how they interact with one another, for a complete understanding of the potential astrophysical impacts of SMBH feedback.

We present a novel, GPU-optimized algorithm for particle-mesh interactions in grid-based hydrodynamics simulations, designed for massively parallel architectures. This approach overcomes the inefficiency of particle neighbour searches or sorts across multiple GPU nodes by using a new ``particle-mesh-particle'' interaction scheme, which extends the particle-mesh method for self-gravity. The algorithm proceeds in two main stages: first, quantities exchanged between particles and the mesh -- such as mass, energy, and momentum added by stellar feedback or removed by accretion onto a sink -- are deposited into a buffer mesh equipped with ghost zones, where multiple contributions per cell are accumulated using atomic additions and then communicated across distributed memory ranks. In the second stage, the buffer states are applied to real mesh states, incorporating cell-wise limiters to enforce physical constraints such as positive density. We implement this scheme in the GPU-native radiation-magnetohydrodynamics code QUOKKA, demonstrating its application to both supernova feedback and sink particle accretion. We demonstrate that the former scheme converges in the terminal radial momentum from multiple supernovae across varying spatial resolutions, while for the latter simulations of accretion in several configurations show excellent agreement with analytic solutions. This scheme enables efficient, scalable particle-mesh coupling for GPU-optimized simulations.

We implement an outlier detection model, an Isolation Foest (iForest), to uncover anomalous objects in the Galaxy and Mass Assembly Fourth Data Release (GAMA DR4). The iForest algorithm is an unsupervise Machine Learning (ML) technique. The data used is the spectroscopic and photometric data from GAMA DR4, which compiless information for over 300000 objects. We select two samples of galaxies to isolate, high signal-to-noise galaxies, to analyse the iForest's robustness, and E+A galaxies, to study the extremes of their population. This results in six-subsamples of spectroscopic, photometric and combined data isolations, finding 101 anomalous objects, half of which have not been identified as outliers in other works. We also find a number of fringing errors and false emission lines, displaying the iForest's potential in detecting these errors. Finding anomalous E+A galaxies, that although selected in a normal manner, using low [OII] and strong H{\delta} absorption, are still star-forming, with strong H{\alpha} emission. We propose two solutions to why these E+A galaxies are still star-forming but also question if these galaxies can be truly classified as E+A galaxies. We suggest that small-scale interactions on the galaxies causes small star bursts. The radiative pressure when forming high mass stars form expels the accreting material quicker than it can be accreted. We also suggest that the Jeans limit in our anomalous E+A galaxies is so low that it is simply not possible to form O and B class stars, but not low enough to fully prevent star-formation.

A combination of JWST observations at z~12-14 and ALMA observations of extremely dust-rich systems at z~6 has demonstrated that dust grows extremely fast in the early Universe, with galaxies amassing up to 10^7 Msun of dust in just 500 Myr between z=12->6. In this paper we demonstrate, via a series of numerical experiments conducted in cosmological zoom-in simulations, that a likely pathway for this dust accumulation in the first formed galaxies is through production at early times via supernovae, followed by the rapid growth on ultrasmall dust grains. Our main results follow. The stellar production of dust dominates until z ~ 10-11 at which point galaxies transition to a growth-dominated regime. We employ a Shapley analysis to demonstrate that the local density is the dominant factor driving dust growth, followed by the grain size distribution. A rapid rise in the small-to-large grain ratio with decreasing redshift (owing to grain-grain shattering) drives growth through increased dust surface area per unit mass. Growth models are necessary to match the dust content of ALMA detected sources at z ~ 6. Finally, we demonstrate that ``blue monsters'', massive, UV-bright galaxies at $z>10$ with extremely blue continuum slopes likely have dust-to stellar mass ratios 10^-4-10^-3, but their top-heavy grain size distributions render them optically thin in the UV, providing a natural explanation for their observed properties without requiring exotic dust geometries.

Reconstructing the formation history of the Milky Way is hindered by stellar migration, which erases kinematic birth signatures. In contrast, stellar chemical abundances remain stable and can be used to trace stars back to their birth environments through chemical tagging. This study aims to improve chemical tagging by developing a method that leverages kinematic and age information to enhance clustering in chemical space, while remaining grounded in chemistry. We implement a graph attention auto-encoder that encodes stars as nodes with chemical features and connects them via edges based on orbital similarity and age. The network learns an ``informed'' chemical space that accentuates coherent this http URL to $\sim$47,000 APOGEE thin disk stars, the method identifies 282 stellar groups. Among them, five out of six open clusters are successfully recovered. Other groups align with the known moving groups Arch/Hat, Sirius, Hyades, and Hercules. Our approach enables chemically grounded yet kinematically and age informed chemical tagging. It significantly improves the identification of coherent stellar populations, offering a framework for future large-scale stellar archaeology efforts.

The streaming instability (SI) is a leading mechanism for planetesimal formation, driving the aerodynamic concentration of solids in protoplanetary disks. The SI triggers strong clumping (i.e., strong enough for clumps to collapse) when the solid-to-gas column density ratio, $Z$, exceeds a threshold, $\Zcrit$. This threshold depends on the dimensionless stopping time, $\tau_s$. Although the strong-clumping threshold has been explored over the last decade, it has been determined largely through 2D axisymmetric simulations. In this work, we perform a suite of 3D, vertically stratified simulations to establish a clumping threshold across $10^{-3} \leq \tau_s \leq 1.0$. Additionally, we study SI-driven concentration that is unique to 3D. We find that $\Zcrit$ is as low as $\approx 0.002$ at $\tau_s=0.1$ and exceeds $\approx 0.03$ at $\tau_s=10^{-3}$. Compared to 2D, our 3D results yield lower $\Zcrit$ for $\tau_s > 0.02$, but higher for $\tau_s \leq 0.02$, with a sharp transition between $\tau_s = 0.02$ and 0.03. This transition correlates with midplane density ratio ($\epsilon$): $\epsilon < 1$ where 3D gives lower thresholds, and $\epsilon > 1$ where 3D gives higher thresholds. We also find a filaments-in-filaments structure when $\epsilon < 1$, which enhances clumping compared to 2D. By contrast, when $\epsilon > 1$ and $\tau_s \leq 0.03$, dust filaments in 3D do not drift inward, suppressing filament mergers and strong clumping. In 2D, filaments drift inward regardless of $\epsilon$, triggering strong clumping easier in this regime. Our results underscore the necessity of 3D simulations for accurately capturing SI-driven concentration and building the strong-clumping threshold.

We present a new cosmological analysis of the small-scale Lyman alpha forest 1D flux power spectrum (P1D) using high-resolution quasar spectra from XQ100 and KODIAQ-SQUAD, interpreted through the PRIYA emulator. PRIYA is a suite of galaxy formation simulations spanning a range of cosmological and inhomogeneous HeII reionization parameters, enabling few-percent-level predictions of the P1D. These datasets, probing down to $k \sim 6\,h\,\mathrm{Mpc}^{-1}$ at $z = 2-5$, offer access to non-linear scales inaccessible to large-volume surveys like eBOSS. We find that the XQ100 P1D yields constraints on the primordial power spectrum parameters $(A_P, n_P)$ at pivot scale $k_0 = 0.78\,\mathrm{Mpc}^{-1}$ that are consistent with PRIYA results from eBOSS DR14 and Planck CMB, albeit with broader uncertainties. Notably, this is achieved without external IGM temperature data, showing that XQ100 alone provides stronger constraints on thermal history than eBOSS DR14. In contrast, the KODIAQ-SQUAD P1D favors a significantly higher $A_P$ value, driven by the selection bias toward high-column density absorbers (HCDs). We also find that the P1D at $k > 0.045\,\mathrm{s/km}$ is more sensitive to Lyman limit system contamination and thermal history. When imposing a prior on $(A_P, n_P)$, the reduced $\chi^2$ remains unchanged and the inferred mean IGM temperature is unaffected, suggesting that cosmological and thermal parameters are largely sensitive to different scales. The XQ100 P1D therefore provides complementary information on thermal nuisance parameters, which can be jointly fit with eBOSS or DESI P1D measurements to improve cosmological constraints.

We use a combination of self-supervised machine learning and visual classification to identify tidal features in a sample of 34,331 galaxies with stellar masses $\log_{10}(M_{*}/\rm{M}_{\odot})\geq9.5$ and redshift $z\leq0.4$, drawn from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) optical imaging survey. We assemble the largest sample of 1646 galaxies with confirmed tidal features, finding a tidal feature fraction $f=0.06^{+0.05}_{-0.01}$. We analyse how the incidences of tidal features and the various classes of tidal features vary with host galaxy stellar mass, photometric redshift, and colour, as well as halo mass. We find an increasing relationship between tidal feature fraction and host galaxy stellar mass, and a decreasing relationship with redshift. We find more tidal features occurring in group environments with $12.0<\log_{10}(M_{200}/\rm{M}_{\odot})<14.0$ than in the field or in denser, cluster environments. We also find that the central galaxies of the most massive ($\log_{10}(M_{200}/\rm{M}_{\odot})>14.1$) groups and clusters exhibit higher rates of tidal features than the satellite galaxies. We find good agreement between the trends we observe and the results obtained from purely visual or other automated methods, confirming the validity of our methodology and that using machine learning can drastically reduce the workload of visual classifiers, having needed to visually classify less than 30 per cent of our sample. Such methods will be instrumental in classifying the millions of suitable galaxies to be observed by large upcoming imaging surveys such as the Vera C. Rubin Observatory's Legacy Survey of Space and Time.

We present a comprehensive analysis of five eclipsing binary systems containing $\beta$ Cephei-type pulsating components. These systems were identified using the high-precision Transiting Exoplanet Survey Satellite (TESS) photometry and complemented by high-resolution spectroscopic data from multiple instruments (e.g., HARPS, FEROS, UVES). For each target, we derived fundamental parameters including masses, radii, effective temperatures, and metallicities through a combined analysis of light curves and radial velocity data. The atmospheric parameters were determined via spectral disentangling and MCMC-based fitting techniques. Absolute parameters were used to position components on the HR diagram, and evolutionary status was assessed using MESA/MIST stellar tracks. Frequency analysis revealed multiple significant pulsation modes in all systems. Our study increases the number of well-characterized $\beta$ Cephei pulsators in binaries and provides high-precision benchmarks for stellar evolution and asteroseismology.

We study 24 massive quiescent galaxies with $\log \textrm{M}_*/\textrm{M}_\odot > 10$ at $1 < z < 3$ with JWST/NIRSpec medium-resolution observations from the Early eXtragalactic Continuum and Emission Line Survey (EXCELS). We reconstruct their star formation histories and find that they have large bursts ($100\textrm{ M}_{\odot} \textrm{yr}^{-1} -1000 \textrm{ M}_{\odot} \textrm{yr}^{-1}$), followed by a rapid truncation of star formation. The number densities of the quenched galaxies in our sample that we predict underwent a submillimeter phase are consistent with submillimeter galaxies being the progenitors of our quenched population. The median post-starburst visibility time is $\sim600$ Myr, with more massive galaxies ($\log \textrm{M}_*/\textrm{M}_\odot > 10.7$) exhibiting shorter visibility times than lower mass galaxies. The range of quenching times -- defined as the time from the peak starburst to the time of quiescence -- found in this sample ($0.06-1.75$ Gyr) suggests multiple quenching pathways, consistent with previous studies. We do not see evidence for quenching mechanisms varying with redshift between $1<z<3$. We detect evidence for weak AGN activity in 4 out of the 8 galaxies with robust emission line detections, based on line ratio diagnostics. Our findings suggest that there are a diverse range of quenching mechanisms at cosmic noon, and support a scenario in which the primary quenching mechanisms are rapid ($<500$ Myr) following a starburst.

With JWST, it is now possible to use Lyman-Alpha (Ly$\alpha$) emission from galaxies beyond z>8 to trace neutral hydrogen in the intergalactic medium (IGM) as the Universe became reionized. However, observed Ly$\alpha$ emission is scattered by neutral hydrogen in the IGM and the interstellar and circum-galactic medium, necessitating `baseline' models of Ly$\alpha$ properties in the ionized IGM to disentangle their impacts. In this work, we characterize Ly$\alpha$ properties at the end of reionization, z~5-6, providing a baseline that can be applied to z>6 observations. We targeted GOODS-N with MMT/Binospec, obtaining R~4360 rest-frame UV spectra of 236 galaxies at z~5-6, selected from HST/CANDELS, finding 62 Ly$\alpha$ detections. We use JWST observations from JADES and FRESCO for a subset of our sources to characterize Ly$\alpha$ properties as a function of UV continuum and H$\alpha$ emission. We present the first statistical measurements of the Ly$\alpha$ FWHM distribution at z~5-6, and produce empirical baseline models of Ly$\alpha$ equivalent width (EWLy$\alpha$) and escape fraction (f$_{esc}^{Ly\alpha}$) conditional on UV magnitude and slope. We find our EWLy$\alpha$ and f$_{esc}^{Ly\alpha}$ models depend on UV magnitude, and infer 45$\pm$5$\%$ and <62$\pm$8$\%$ of MUV=-19.5 galaxies have EWLy$\alpha$>25$Å$ and f$_{esc}^{Ly\alpha}$>0.2, respectively. We find a mean Ly$\alpha$ FWHM of 245km/s and median Ly$\alpha$ velocity offset of 258km/s, both correlating with higher UV luminosity. Our median observed Ly$\alpha$ line profile is broader and has higher velocity offset compared to pre-JWST models based on z~2 lines, which may reflect resonant scattering by residual neutral hydrogen in the IGM at z~5-6 and increasing ISM/CGM densities. Our median line profile predicts higher Ly$\alpha$ transmission in a fully neutral IGM, providing insight into recent z>10 Ly$\alpha$ detections.

When coherent light propagates through a multimode optical fiber, the modes interfere at the fiber exit boundary, producing a high-contrast speckle interference pattern called modal noise. This non-uniform interference pattern introduces systematic errors in fiber-fed precision radial velocity (RV) spectrographs which are detrimental to exoplanet mass measurement. Modal noise can be mitigated by a device called a fiber mode scrambler or fiber agitator, which dynamically perturbs the fiber to change the interference pattern over time, smoothing it over long exposures. In this paper, we present a prototype optical fiber mode scrambler based on a four-bar linkage crank-rocker mechanism, developed for the GMT-Consortium Large Earth Finder (G-CLEF). G-CLEF is a fiber-fed, high-resolution, precision RV spectrograph for the Magellan Clay Telescope and Giant Magellan Telescope (GMT). To support this effort, we developed a fiber testing setup capable of imaging the near-field and far-field output of fibers and measuring focal ratio degradation. We designed, built, and tested the mode scrambler, using our setup, on step-index multimode optical fibers with various shapes, including octagonal, square, and rectangular core cross-sections. We developed custom software utilizing alpha shapes to identify the boundary of an arbitrarily shaped fiber and to compute a signal-to-noise ratio metric for quantifying modal noise. We investigated the effects of different mode scrambler parameters, such as agitation frequency, on mitigating modal noise. Our results offer valuable insights into optimizing fiber mode scrambling for precision RV spectrographs.

The presence of molecular isomers in interstellar environments has become a topic of growing interest within the astrochemical community. Contrary to predictions based on thermodynamic equilibrium, recent observations reveal a diverse array of high-energy isomers and conformers. One of the most iconic molecular isomers detected in space, formic acid (HCOOH, FA), has been the focus of extensive theoretical research aimed at understanding its speciation into cis and trans conformers in dark clouds and photodissociation regions. In this work, we report the detection of c-FA, the higher-energy conformer, using ultrasensitive observations of TMC-1. This detection adds to previous findings in the Barnard-5 and L483 dark clouds. The derived trans-to-cis isomer ratio in TMC-1, 17.5, closely matches those observed in other sources, suggesting that the same chemical processes are at play across these environments. To investigate this, we conducted detailed astrochemical gas-grain models tailored to formic acid isomerism to explain the observed ratios. Our models successfully reproduce the observed trans/cis ratios and indicate that the presence of cis-formic acid can be attributed to the release of c-FA from grains, followed by isomerization driven by the excess energy released during the desorption process, a process that we name as isomerization upon desorption. The models also show that the isomerization of t-FA to c-FA in the gas phase is negligible at 10 K, meaning the observed ratios are a direct consequence of the formation pathways of both isomers on the surface of dust grains. However, at higher temperatures, quantum tunneling mediated direct isomerization in the gas becomes significant, and the ratios converge toward the thermodynamic equilibrium value.

Star formation occurs within dusty molecular clouds that are then disrupted by stellar feedback. However, the timing and physical mechanisms that govern the transition from deeply embedded to exposed stars remain uncertain. Using the STARFORGE simulations, we analyze the evolution of ``embeddedness'', identifying what drives emergence. We find the transition from embedded to exposed is fast for individual stars, within 1.3 Myr after the star reaches its maximum mass. This rapid transition is dominated by massive stars, which accrete while remaining highly obscured until their feedback eventually balances, then overcomes, the local accretion. For these massive stars, their maximum mass is reached simultaneously with their emergence. Once these stars are revealed, their localized, pre-supernova feedback then impacts the cloud, driving gas clearance. Because massive stars dominate the luminosity, their fast, local evolution dominates the light emergence from the dust. We calculate the dependence of these processes on the mass of the cloud and find that emergence always depends on when massive stars form, which scales with the cloud's free-fall time. We also examine the evolution of dust emission and H$\alpha$ luminosity. We find that dust dominates the luminosity for roughly 2 Myrs before stellar luminosity becomes more luminous. These results suggest that deeply embedded star-forming clusters tend to be rare compared to those partially exposed. Thus, because the initial embedding of the most luminous stars is highly local, the emergence of stars is a faster, earlier, more local event than the overall disruption of the cloud by gas expulsion.

Resolved high-redshift galaxy gas kinematics is a rapidly evolving field driven by increasingly powerful instrumentation. However, the resolution and sensitivity still impose constraints on interpretation. We investigate the uncertainties inherent to high-$z$ galaxy kinematical analysis by modelling a suite of rotating disk galaxies, generating synthetic interferometric ALMA observations, and fitting them with the 3D-kinematical tools 3DBarolo, GalPaK3D, and Qubefit. We present the recovered 3D-fitted kinematical parameters to assess their reliability, quantify the range of values possible for individual source studies, and establish the systematic biases present for observed samples. The $V/\sigma_{\rm V}$ ratio, which indicates how dynamically cold a system is, is of particular importance and depends on the choice of 3D-fitting tool. On average, 3DBarolo and Qubefit slightly overestimates $V/\sigma_{\rm V}$ ($<1\sigma$) and GalPaK3D underestimates it ($<2\sigma$). Therefore, all three tools are reliable for kinematical studies of averages of high-redshift galaxy samples. The value range possible for individual sources is significant, however, even more so for samples of not purely rotation dominated sources. To determine whether an observed galaxy is rotation dominated enough to be fitted with a 3D-kinematical tool, $V/\sigma_{\rm V}$ can be extracted directly from the observed data cube, with some caveats. We recommend that the median offsets, value ranges, and tool-dependent biases presented in this paper are taken into account when interpreting 3D-fitted kinematics of observed high-redshift galaxies.

The Surface Detector (SD) of the Pierre Auger Observatory is a 3000 km$^2$ array of stations, whose main components are Water-Cherenkov Detectors (WCDs) recording ground-level signals from extensive air showers (EASs) initiated by Ultra-High-Energy Cosmic Rays (UHECRs). Understanding the physics of UHECRs requires knowledge of their mass composition, for which the number of ground muons is a key probe. Isolating the muon component is difficult, as different types of particles contribute to the SD signal. We apply a recurrent neural network to estimate the muon content of the SD signals, showing small bias in simulations and weak dependence on selected hadronic interaction model.

We present observations and analyses of three high-magnification microlensing events: KMT-2022-BLG-0954, KMT-2024-BLG-0697, and MOA-2024-BLG-018. All three exhibit the "Planet/Binary" degeneracy, with planetary solutions corresponding to mass ratios in the range $-3.7 < \log q < -2.2$, while the binary solutions yield $\log q > -2.0$. For KMT-2022-BLG-0954, we identify a previously unrecognized degeneracy among planetary solutions, involving different mass ratios and normalized source radii. In all three cases, single-lens binary-source models are excluded. Bayesian analyses suggest that the planetary solutions correspond to gas giants orbiting M/K dwarfs beyond the snow line, while KMT-2022-BLG-0954 also admits an alternative interpretation as a super-Earth orbiting a late-type M dwarf. The binary solutions imply a diverse set of systems, including M-dwarf pairs and M-dwarf--brown-dwarf binaries. A review of known events subject to the "Planet/Binary" degeneracy shows that in most cases the degeneracy cannot be resolved through follow-up high-resolution imaging, particularly in the presence of the newly identified degeneracy.

The Milky Way's galactic center is a highly dynamical, crowded environment. Gamma ray observations of this region, such as the excess of GeV scale gamma rays observed by Fermi LAT, have been of tremendous interest to both the high energy astrophysics and particle physics communities. However, nearly all past studies of gamma ray emission make simplifying assumptions about cosmic ray (CR) propagation that may not be valid in the galactic center. Recent numerical breakthroughs now enable fully time dependent dynamical evolution of CRs in magnetohydrodynamic simulations with resolved, multi phase small scale structure in the interstellar medium (ISM), allowing self consistent comparisons to the Milky Way cosmic ray spectrum. We model diffuse gamma ray emission from cosmic ray interactions for a set of Feedback in Realistic Environments (FIRE) simulations of Milky Way mass galaxies run with spectrally resolved cosmic ray spectra for multiple species at MeV to TeV energies. We find that the galactic center gamma ray spectrum can vary by order of magnitude amounts in normalization, and by approx. 10 percent in spectral slope at high energies, driven by both injection from highly variable star formation and losses from variable structure in the turbulent ISM. Gamma ray emission from inverse Compton scattering and relativistic nonthermal Bremsstrahlung is particularly variable on Myr timescales. We argue that features of the observed Milky Way gamma ray spectrum may arise from such transient phenomena in gamma rays produced from CR interactions.

Under the assumptions of General Relativity (GR), gravitational waves propagate at the speed of light and their mediation can be represented as a particle through a massless graviton. We investigate the impact and observability of the presence of a massive graviton, how such a modification to GR would also modify the propagation of observed gravitational waves from astrophysical sources, and how this effect can be used as an independent measurement of cosmological parameters, focusing on the Hubble parameter $H_0$ and matter energy $\Omega_m$. We simulate the impact of a massive graviton on compact binary coalescence observations in a near-future LIGO-Virgo-KAGRA interferometer network through a modification to the gravitational wave phase in the post-Newtonian framework. Our analysis finds that if we assume the presence of a graviton with a Compton wavelength of $\lambda_G \approx 5 \times 10^{16}$m, corresponding to a mass $m_G \leq 2.3 \times 10^{-23}$eV/c$^2$, we can utilize a simulated population of 60 binary black hole observations to constrain $H_0$ to a similar precision as current gravitational wave constraints without electromagnetic counterparts (at $90\%$ credible intervals): $H_0 = 58^{+34}_{-19}\,\mathrm{km\; s^{-1}\; Mpc^{-1}}$ and $\Omega_m=0.29^{+0.10}_{-0.08}$. More sensitive observatories will be necessary to probe lower values in the graviton mass range and fully exploit this method.

The Askaryan Radio Array (ARA) has been operating at the South Pole for over a decade, searching for ultra-high energy astrophysical and cosmogenic neutrinos using the Askaryan effect. ARA has consistently served as a testbed for innovative trigger designs and advancing electronic upgrades, with ongoing data acquisition (DAQ) improvements over the past 2-3 years and a long-term plan to transition to Radio Frequency System on Chip (RFSoC) technology. This upgrade enables real-time data processing and sophisticated triggers, enhancing efficiency by identifying double pulses from in-ice neutrino interactions, using templates for cosmic rays, searching for real-time coincidences with the IceCube detector observations, and filtering anthropogenic noise through directional analysis. In 2024, two of the five ARA stations received DAQ upgrades, improving the existing electronics, with RFSoC-based DAQ foreseen in the coming years. In this proceedings contribution, recent ARA activities are presented, with emphasis on the planned ARA-Next trigger strategies involving RFSoC technology and the 2024-2025 season upgrades of the existing ATRI-based DAQ system to its revised version.

Collisionless, turbulent plasmas surround the Earth, from the magnetosphere to the intergalactic medium, and the fluctuations within them affect nearly every field in the space sciences, from space weather forecasts to theories of galaxy formation. Where turbulent motions become supersonic, their interactions can lead to the formation of shocks, which are known to efficiently energize ions to cosmic-ray energies. We present 2.5-dimensional, hybrid-kinetic simulations of decaying, supersonic, non-relativistic turbulence in a collisionless plasma using the code dHybridR. Turbulence within these simulations is highly compressible; after accounting for this compression by taking the omni-directional power-spectrum of the density weighted velocity field, we find turbulent spectra with power-law slopes of $\alpha \approx -\frac{5}{3}$ for low Mach numbers, in the inertial range, and $\alpha \approx -2$ for high Mach numbers. Ions embedded in the highly supersonic simulations are accelerated to non-thermal energies at efficiencies similar to those seen in shocks, despite being in a non-relativistic regime and lacking the large scale structure of a shock. We observe that particles are accelerated into a power-law spectrum, with a slope of $q \approx 2.5$ in (non-relativistic) energy. We compare these results to those obtained from the theory and simulations of diffusive shock acceleration, and discuss the astrophysical implications of this theoretical work.

We present high resolution (subarcsecond) observations at 6.2 and 19.6 GHz made with the Karl G. Jansky Very Large Array of 113 radio-loud quasars that form a complete flux limited sample (> 70 mJy at 1.4 GHz), with spectroscopic redshifts between 2.5 and 5.28. These redshifts correspond to ages since the big bang of 1.1 to 2.6 Gyr, or more colloquially, from Cosmic Dawn to Cosmic High Noon. This is when large scale structure formation and galaxy formation were proceeding at an ever increasing pace, and this sample appears to be unique (for now) for spanning this era. We show images of the significantly resolved sources, and list structural properties of all of them.

Stellar mergers are responsible for a large variety of astrophysical phenomena. They form blue straggler stars, give rise to spectacular transients, and produce some of the most massive stars in the Universe. Here, we focus on mergers from binary evolution and stellar collisions but do not cover mergers involving compact objects. We review how mergers come about, explain the physics and outcome of the merger process, discuss the evolution and ultimate fates of merged stars, and relate to observations. Our main conclusions are: (i) Mergers of main-sequence stars often fully rejuvenate and have interior structures similar to genuine single stars. (ii) Contrarily, mergers involving post-main-sequence stars can have interior structures that cannot be achieved by single-star evolution. Such merged stars may become long-lived blue supergiants that can explode in SN1987A-like events, interacting and superluminous supernovae, ultra-long gamma-ray bursts or collapse into very massive black holes. These black holes may even populate the pair-instability-supernova black-hole mass gap. (iii) Strong magnetic fields are produced in stellar mergers. Merged stars may thus be at the origin of some magnetic OBA stars and their descendants, highly magnetic white dwarfs and neutron stars. (iv) Initially, stellar merger products rotate rapidly, but there are several mechanisms that can quickly spin them down. Hence, merged stars may be rather slow rotators for most of their evolution.

Context. A key property of massive stars is their high degree of multiplicity, which can impact their evolution and end-of-life products. The Southern Massive Stars at High Angular Resolution survey (smash+) use interferometric and high-angular resolution techniques to detect companions at intermediate separations, from about 1 milli-arsec to 8"), a domain that so far has remained largely unexplored. Aims. In this paper, we convert the angular separations and magnitude contrasts into physical units, i.e. projected physical separations and mass ratios. We also derive the sensitivity of the survey for various physical and orbital parameters. Methods. We develop a spectral-type/luminosity class -- H-band luminosity -- mass calibration based on existing grids of physical parameters of OBA stars and we use these to obtain the photometric distance to each system, correcting for all known companions within the 2MASS point-spread function. We also derive the individual masses of the primaries and of each detected companion. Results The probability of detecting companions is very uniform within the sensitivity limits of the \smash\ survey. The projected separations follow a flat power-law distribution in log-separation. The obtained mass ratios are compatible with the power-law distributions derived for spectroscopic binaries. Finally, we find a uniform mass-ratio distribution up to ~100 AU. Beyond ~100 AU, we observe a lack of equal-mass companions, with an upper mass-ratio limit declining towards larger separations.

The spatiotemporal inhomogeneous-homogeneous transition in the dynamics and structures of solar photospheric turbulence is studied by applying the complexity-entropy analysis to Hinode images of a vortical region of supergranular junctions in the quiet Sun. During a period of supergranular vortex expansion of 37.5 min, the spatiotemporal dynamics of the line-of-sight magnetic field and the horizontal electromagnetic energy flux display the characteristics of inverse turbulent cascade, evidenced by the formation of a large magnetic coherent structure via the merger of two small magnetic elements trapped by a long-duration vortex. Both magnetic and Poynting fluxes exhibit an admixture of chaos and stochasticity in the complexity-entropy plane, involving a temporal transition from low to high complexity and a temporal transition from high to low entropy during the period of vortex expansion, consistent with Hinode observations.

Super-Earths exist around subsolar-metallicity host stars with a frequency comparable to that around solar-metallicity stars, suggesting efficient assembly of dust grains even in metal-deficient environments. In this study, we propose a pathway for the formation of multiple dust rings that will promote planetesimal formation in a subsolar-metallicity disk. We investigate the long-term evolution of a circumstellar disk with 0.1 $Z_{\odot}$ over 750 kyr from its formation stage using two-dimensional thin-disk hydrodynamic simulations. The motion of dust grains is solved separately from the gas, incorporating dust growth and self-consistent radial drift. The disk is initially gravitationally unstable and undergoes intense fragmentation. By 300 kyr, it tends toward a stable state, leaving a single gravitationally bound clump. This clump generates tightly wound spiral arms through its orbital motion. After the clump dissipates at $\sim$410 kyr, the spiral arms transition into axisymmetric substructures under the influence of viscosity. These axisymmetric substructures create local gas pressure bumps that halt the inward radial drift of dust grains, resulting in the formation of multiple-ring-shaped dust distributions. We observe several rings within $\simeq$200 au of the central star, with separations between them on the order of $\sim$10 au, and dust surface density contrasts with inter-ring gaps by factors of $\sim$10-100. We also demonstrate that turbulent viscosities at observationally suggested levels are essential for converting spiral arms into axisymmetric substructures. We speculate that the physical conditions in the dust rings may be conducive to the development of streaming instability and planetesimal formation.

We present the redesign of the fiber feed for the High Resolution Spectrograph (HRS) at the Hobby Eberly Telescope (HET). The upgrade incorporates a static atmospheric dispersion corrector (ADC) using Ohara i-line glasses (BAL15Y and S-FPL51Y), carefully selected for high internal transmission (> 99\%), and optimized to improve throughput and image quality across the 360 - 1000 nm band. The ADC consists of two identical Amici prisms, fixed at an orientation optimized for the HET's nominal zenith angle (35\textdegree), correcting dispersion over the HET zenith range of 26.5\textdegree to 43.5\textdegree. Relay optics were optimized to improve blue end sensitivity and maintain substantially sub-fiber-core RMS spot radii across the full field of view. Simulations, including atmospheric dispersion modeling in ZEMAX show residual dispersion $\le$ 0.42" considering the entire range of wavelengths and zenith distances, with transmission efficiency of 91 to 94\%. We also discuss how the mechanical design integrates all optical elements, including the ADC, in a rigid, modular input head assembly mounted in the HET Prime Focus Instrument Package (PFIP). This optimized fiber feed enhances coupling efficiency, improves S/N in the blue, and enables higher radial velocity precision , maintaining HET - HRS as a leading facility for high - resolution spectroscopy.

Gravity plays important roles at multiple scales in the universe. An important, yet often neglected, role of gravity is its ability in driving anisotropic fragmentation through tides. When tides dominate, fragmentation becomes anisotropic, and the Jeans length along the short axis, $l_{\rm tidal, Jeans}$, is approximately $\sigma_{\rm v}/\sqrt{G \rho_{\rm mean}}$, determined by the external tides through the mean density $\rho_{\rm mean}$. We compare predictions of $l_{\rm tidal, Jeans}$ against observational results in massive star-forming clumps, the Circumnuclear Disk (CND) around the supermassive black hole Sgr A* at the center of the Galaxy, the Central Molecular Zone in the Galactic Center, a hub-filament system, and a streamer around a young star. We find that the observed widths of these filamentary structures match theoretical predictions from tidally-controlled Jeans fragmentation. The formation of filaments can potentially shield cold gas against radiation pressure and photoevaporation, as well as hydrodynamical interaction with the ambient medium, potentially enabling the cold gas to survive. Thus, tidal forces are major players regulating gas transport around massive objects.

Kinematic information is crucial for understanding the evolution of complex systems, such as interstellar gas. Obtaining full 3D kinematic information is a crucial final step for modeling and interpretation. Molecular clouds are nurseries where stars are born. Stars at a very early stage, like young stellar objects (YSOs), inherit the spatial and kinematic structure of the gas patches they originate from. In this paper, we combine measurements of radial velocities towards the gas and the kinematic information of YSOs from Gaia DR3 to derive 3D velocities of a sample of YSO (Young Stellar Object)-MC (Molecular Cloud) complexes at d$\lesssim$3.5kpc from the Sun. We find that the molecular interstellar medium traced by the YSO-MC complexes generally follows Galactic rotation, with an additional peculiar velocity of 8.6 km s$^{-1}$. The random motion of these complexes in the Galactic XY plane is more energetic than motion along the Z direction. A catalogue containing the 3D velocities of the YSO-MC complexes at different reference frames is available, and the distances and 3D velocities of well-known molecular clouds are presented. Our results set the foundation for exploring the interplay between the Galaxy, the molecular ISM, and star formation. Data available at this https URL.

We present TOI-2155 b, a high-mass transiting brown dwarf discovered using data from NASA's Transiting Exoplanet Survey Satellite (TESS) mission and confirmed with ground-based radial velocity measurements from the Tillinghast Reflector Echelle Spectrograph (TRES). We also analyze ground-based follow-up photometric data from the Wendelstein Observatory (WST), Las Cumbres Observatory Global Telescope (LCOGT), and Wild Boar Remote Observatory (WBR). TOI-2155 b is a short-period brown dwarf with a period of 3.7246950 +0.0000029/-0.0000028 days. The radius and mass of TOI-2155 b are found to be 0.975 +/- 0.008 Jupiter radii and 81.1 +/- 1.1 Jupiter masses, respectively, corresponding to a density of 110 +/- 3 g/cm3. The effective temperature of the subgiant host star is estimated at 6085 +/- 78 K, which identifies it as an F-type star with a radius of 1.705 +0.066/-0.064 solar radii and a mass of 1.33 +/- 0.008 solar masses. With a mass close to the hydrogen-burning limit, TOI-2155 b occupies a high-mass regime in the brown dwarf mass-radius diagram, making it a valuable benchmark system for testing models of substellar structure and evolution.

Robotic and human activities in the cislunar space are expected to rapidly increase in the future. Modeling, jointly analysis and sharing of time measurements made in the vicinity of the Moon might indispensably demand calculating a lunar time scale and transforming it into other time scales. For users, we present a ready-to-use software package of Lunar Time Ephemeris $\texttt{LTE440}$ that can calculate the Lunar Coordinate Time (TCL) and its relations with the Barycentric Coordinate Time (TCB) and the Barycentric Dynamical Time (TDB). According to the International Astronomical Union Resolutions on relativistic time scales, we numerically calculate the relativistic time-dilation integral in the transformation between TCL and TCB/TDB with the JPL ephemeris DE440 including the gravitational contributions from the Sun, all planets, the main belt asteroids and the Kuiper belt objects, and export data files in the SPICE format. At a conservative estimate, $\texttt{LTE440}$ has an accuracy better than 0.15 ns before 2050 and a numerical precision at the level of 1 ps over its entire time span. The secular drifts between the coordinate times in $\texttt{LTE440}$ are respectively estimated as $\langle \mathrm{d}\,\mathrm{TCL}/\mathrm{d}\,\mathrm{TCB}\rangle=1-1.482\,536\,216\,7\times10^{-8}$ and $\langle \mathrm{d}\,\mathrm{TCL}/\mathrm{d}\,\mathrm{TDB}\rangle=1+6.798\,355\,24\times10^{-10}$. Its most significant periodic variations are an annual term with amplitude of 1.65 ms and a monthly term with amplitude of 126 $\mu$s. $\texttt{LTE440}$ might satisfy most of current needs and is publicly available.

The low-density region of the interstellar medium (ISM) where the Sun is located is known as the Local Bubble, a cavity filled with high-temperature and low-density plasma that may be created by a series of supernova (SN) explosions over the past 14 Myr. However, the effects of these SN explosions on the formation and evolution of the Local Bubble, as well as on nearby star formation, remain not fully understood. To study the expansion history of the Local Bubble, we use the kinematic data of the young stars obtained by cross-matching the pre-main-sequence (PMS) star catalog of \citet{Zari2018} with the high-precision astrometric and photometric data from the {\it Gaia} DR3 database. We perform a three-dimensional spatial clustering analysis on these young stars to identify star associations. We discover three unique star associations that exhibit a wiggle-like velocity pattern. The distances of these star associations are 108.5308, 141.5284, and 176.0318 pc, respectively. Their radial velocities in the Local Standard of Rest (LSR) are 10.0622, 5.4982, and 9.0581 km/s, showing a pattern of decreasing and then increasing. This velocity pattern, as predicted by \citet{Krause&Diehl2014}, is caused by a recent re-acceleration affected by the SN explosion, reinforcing the picture of the Local Bubble as an evolving entity.

Although the dependence of convective core overshooting on mass has attracted much attention, no corresponding work exists for overshooting below a convective envelope. We aim to quantify this relationship for pre-main sequence stars of intermediate mass ranging from $1.2 M_{\mathsf{sun}}$ to $6 M_{\mathsf{sun}}$. These stars have a similar thermal and density structure, making this a suitable choice to isolate the effect of changing mass. We produce a series of two-dimensional global simulations of stars using MUSIC, a fully compressible, time-implicit hydrodynamics code. The stars that we select for this study are near the end of the pre-main sequence and are convectively unstable above 80% of their stellar radius; they thus have a convective envelope that is shallower than the current sun. For this series of stellar models, a simple scaling with luminosity, with a scaling exponent of 1/4, accounts for the increasing overshooting with stellar mass. This result has interesting similarities with the scaling found by Baraffe et al. [2023] for a range of intermediate mass and massive stars at the zero-age main sequence (ZAMS) that have convective cores.

NASA's Nancy Grace Roman Space Telescope (Roman) will provide an opportunity to study dark energy with unprecedented precision using several techniques, including measurements of Type Ia Supernovae (SNe Ia). Here, we present `phrosty` (PHotometry for ROman with SFFT for tYpe Ia supernovae): a difference imaging pipeline for measuring the brightness of transient point sources in the sky, primarily SNe Ia, using Roman data. `phrosty` is written in Python. We implement a GPU-accelerated version of the Saccadic Fast Fourier Transform (SFFT) method for difference imaging.

Near-ultraviolet (NUV) radiation from dwarf stars plays a critical role in shaping the habitability of planetary systems, yet its long-term evolution across different spectral types remains poorly investigated. Based on GALEX NUV observations, we study the evolution of stellar NUV emission for a sample of 386,500 A- to M-type dwarfs spanning ages from 3 Myr to 10 Gyr, drawn from both open clusters and the field. The normalized NUV emission ($f_{\rm NUV}/f_{\rm J}$) is used to trace the evolutionary trends. Our results reveal distinct evolutionary pathways after considering the distance completeness: A and early-F dwarfs show a weak decline in NUV emission during the main-sequence phase; late-F to G dwarfs exhibit a clear decrease, consistent with continuous spin-down driven by magnetic braking; late-K and M-dwarfs undergo a rapid decline in NUV emission when they evolve from young stellar objects to main-sequence stars. Furthermore, we construct the evolutionary tracks of stellar ultraviolet habitable zone (UHZ). By comparing stellar circumstellar habitable zone (CHZ) and UHZ, we find that G- and K-type stars offer the most stable overlap between thermal and UV habitability over long-term evolution.

Within 20 pc of the Sun there are currently 29 known cold brown dwarfs, sources with measured distances and an estimated effective temperature between that of Jupiter (170K) and ~500K. These sources are almost all isolated and are the closest laboratories we have for detailed atmospheric studies of giant planets formed outside the solar system. Here we report JWST observations of one such source, WISEA J153429.75-104303.3 (W1534), which we confirm is a substellar mass member of the Galactic halo with a metallicity <0.01xsolar. Its spectrum reveals methane (CH4), water (H2O), and silane (SiH4) gas. Although SiH4 is expected to serve as a key reservoir for the cloud-forming element Si in gas giant worlds, it eluded detection until now because it is removed from observable atmospheres by the formation of silicate clouds at depth. These condensates are favored with increasing metallicity, explaining why SiH4 remains undetected on well studied, metal-rich solar system worlds like Jupiter and Saturn. On the metal-poor world W1534, we detect a clear signature of SiH4 centered at ~4.55 microns with an abundance of 19+/-2 parts per billion (ppb). Our chemical modelling suggests that this SiH4 abundance may be quenched at ~kilobar levels just above the silicate cloud layers, whereupon vertical atmospheric mixing can transport SiH4 to the observable photosphere. The formation and detection of SiH4 demonstrates key coupled relationships between composition, cloud formation, and atmospheric mixing in cold brown dwarf and planetary atmospheres.

HWO's Tier 1 Contrast Stability Technology Gap presents a key challenge for technology development in the coming years, requiring to a >100x more stable system than JWST. WaveDriver is a concept for a laser guide star spacecraft coupled to an adaptive optics (AO) system onboard HWO that would enable HWO to reach its picometer-level wavefront stability requirements while relaxing other HWO subsystem requirements. At LLNL and UCSC we are revisiting the concept initially proposed by Douglas et al. (2019). We present results from our project's first year, including (1) AO control developments, including with Linear Quadratic Gaussian control and machine learning, (2) AO wavefront sensor (WFS) trade study simulations, and (3) simulations, fabrication, and testing of a 133-port photonic lantern WFS/spectrograph. A key finding from our work is that WaveDriver could be needed to enable HWO's primary mirror segment stability and/or low order wavefront stability requirements.

Fibrils are dynamic plasma structures in the solar chromosphere. Studying these structures is critical for understanding solar atmospheric heating and mass transportation. The purpose of this study is to obtain the characteristics of fibrils surrounding the filament. By employing high-resolution H-alpha data obtained from the New Vacuum Solar Telescope (NVST), we undertake a detailed analysis of the properties of 63 fibrils situated in the vicinity of the filament. Comparing the fibrils on both sides of the filament demonstrates that these fibrils have similar physical properties except for their orientation. The properties of fibrils are statistically measured, including lifetimes of 150-650 s, widths of 320-850 km, maximum lengths of 3-8.5 Mm, projection velocities of 7-29 km/s, and decelerations of 45-474 m/s2. The dominant oscillation period of fibrils is predominantly concentrated in the range of 4.8-6.6 minutes (2.5-3.5 mHz). Transverse oscillations are identified in a subset of fibrils, with periodicities of 269-289 s and phase speeds of 13.7-25.8 km/s, indicating the presence of kink-mode magnetohydrodynamic (MHD) waves.

The chemical abundances of metal-poor stars in globular clusters provide important constraints on their evolutionary scenarios. Using both main r-process and weak r-process patterns, we fit the abundances of s-poor stars in the globular cluster M22. The coefficients of the main and weak r-process components are nearly constant for the sample stars, including s-rich stars. By accounting for the contribution of the s-process from low-mass asymptotic giant branch stars, the abundances of s-rich stars in M22 can also be fitted effectively. In addition, the increasing trend in the s-process component coefficients with rising [Fe/H] indicates a gradual increase in the contribution from low-mass asymptotic giant branch stars.

The Mg I 12.32 {\mu}m line is highly sensitive to magnetic fields due to its long wavelength, making it a promising tool for precise solar-magnetic-field measurements. The formation of this line is significantly influenced by nonlocal thermodynamic equilibrium (NLTE) effects. Previous studies have shown that the Mg I 12.32 {\mu}m line exhibits different behaviors in various regions of the Sun. This study focuses on the peak intensity of the Mg I 12.32 {\mu}m line to analyze its relationship with the physical parameters of the solar atmosphere and its formation mechanism. We employed the Rybicki-Hummer (RH) 1.5D radiative transfer code to synthesize the Stokes profiles of the Mg I 12.32 {\mu}m line based on a three-dimensional solar atmospheric model of a sunspot and its surrounding quiet Sun. By computing Rxi{\Delta}xi, where Rxi is the average response function and {\Delta}xi is the difference in physical parameters between the two models being compared, we identified the atmospheric height and physical parameters that most significantly influence the normalized peak intensity in the quiet Sun and the active region, respectively. In analyzing the synthesized Stokes profiles, we found two key features: (1) in the quiet Sun, the normalized peak intensity is strong at the centers of the granules and weakens in the intergranular lanes; (2) in the sunspot umbra, the normalized peak intensity is generally weak, with only a few areas showing evident emission. Through the analysis of the response functions, we identified the causes of these differences. In addition, we discussed the mechanisms through which these physical parameters influence the normalized peak intensity.

Gravitational waves (GWs) from binary neutron star (BNS) merger remnants complement constraints from the inspiral phase, mass-radius measurements, and microscopic theory by providing information about the neutron-star equation of state (EOS) at extreme densities. We perform general-relativistic simulations of BNS mergers using EOS models that span the uncertain high-density regime. We find a robust correlation between the ratio of energy and angular momentum lost during the late-time post-merger GW signal - the long ringdown - and the EOS at the highest densities in neutron star cores. Applying this correlation to post-merger GW signals reduces EOS uncertainty at several times saturation density, where no direct constraints currently exist.

We conducted a systematic spectral study for single F-type main-sequence (MS) stars without significant X-ray outbursts to investigate X-ray spectral properties such as temperature, emission measure (EM), and luminosity (Lx). To this end, 33 single stars with relatively rich X-ray photon statistics were selected by cross-matching large astronomical catalogs of the XMM-Newton source catalog and the Tycho-2 spectral type catalog. A positive correlation was found in the observed EM--EM-weighted temperature relationship as seen in late-type stars and it is also found in the relationship that our single F-type MS star samples have a plasma with an EM-weighted temperature of $\lesssim$1 keV and an EM of $\lesssim$10$^{53}$ cm$^{-3}$ corresponding to Lx of $\lesssim$10$^{30}$~erg~s$^{-1}$. These observational features for the single F-type MS stars are consistent with those of the single G dwarf stars, suggesting that there are no significant differences in their X-ray coronal properties. Additionally, the obtained relationship between the X-ray activity and the Rossby number reinforces this suggestion in the literature. Moreover, the upper bounds in EM and Lx were found to be unique signatures for single stars and not valid for binary stars. Our results suggest that the planetary evolution in terms of the X-ray properties around F-type MS stars can be understood by extending the frameworks developed for G-type stars.

The cosmic dipole measured in surveys of cosmologically distant sources is generally found to be in disagreement with the kinematic expectation of the Cosmic Microwave Background (CMB). This discrepancy represents severe tension with the Cosmological Principle and challenges the standard model of cosmology. Here, we present a Bayesian analysis of the tension between datasets used to measure the cosmic dipole. We examine the NRAO VLA Sky Survey (NVSS), the Rapid ASKAP Continuum Survey (RACS) and the Wide-field Infrared Survey Explorer catalogue (CatWISE), and jointly analyse them with the Planck observations of the CMB. Under the kinematic interpretation, we find that Planck is in severe tension with CatWISE above 5$\sigma$, strong tension with RACS, and moderate tension with NVSS. Moreover, the strong concordance between CatWISE and NVSS suggests that their dipoles arise from a common astrophysical signal. Conversely, the high discordance between RACS and both CatWISE and NVSS indicates a possible systematic difference in the RACS catalogue itself. Whilst the tension between Planck and infrared-selected quasars is already significant, the question of whether or not the dipole in individual radio surveys adds to the challenge against the standard model is yet to be seen. We estimate that $\mathcal{O}(10^6)$ radio sources are required to measure the tension to a significance of 5$\sigma$. Therefore, in light of the upcoming SKA radio surveys, we are on the cusp of disentangling the anomaly of the cosmic dipole.

The discovery of VHE emission from the Crab pulsar and, more recently, multi-TeV emission from the Vela pulsar have challenged our current understanding of the emission mechanisms of these sources. Studying pulsar emission at TeV energies allows us to understand the engines that power some of the most extreme accelerators in the Galaxy. We present recent highlights from the VERITAS pulsar program using nearly two decades of VERITAS data and novel high energy analysis techniques optimized for emission up to 100 TeV. This work begins to characterize how the emerging population of multi-TeV pulsars can be predicted from existing multi-wavelength observations. In particular, we highlight a search for VHE emission above 1 TeV using over 17 years of Crab pulsar data, which extends the high energy end of the existing VERITAS spectrum. Additionally, we search for both optical and multi-TeV emission from bright Vela-like pulsars, including analysis of over 200 hours of data on PSR J2229+6114, which powers the Boomerang pulsar wind nebula and is putatively associated with the ultra-high-energy source 1LHAASO J2229+5927u. We discuss these results in the context of the broader pulsar population and their impacts on the prospects of new pulsar discoveries with next-generation VHE instruments.

Atmospheric characterization of exoplanets has traditionally relied on Low-Resolution Transmission Spectroscopy (LRTS), obtained from both space- and ground-based facilities, as well as on High-Resolution Transmission Spectroscopy (HRTS). Although HRTS can resolve individual spectral lines, it is subject to normalization degeneracies that limit the accurate retrieval of key atmospheric parameters such as pressure, abundance, and cloud opacity. A promising strategy to mitigate this issue is to combine ground-based HRTS with space-based LRTS. However, this approach depends on two separate datasets, thereby requiring two independent observations. In this study, we explore the feasibility of Multi-Object High-Resolution Transmission Spectroscopy (Mo-HRTS) as a means to constrain atmospheric parameters in retrievals using a single dataset. Through simulations based on existing spectrograph specifications for a well-studied target, we demonstrate that low-resolution broadband transmission spectra can be extracted from Mo-HRTS data.

We present the deepest 21-cm spectral line and 1.4 GHz broad-band continuum observations of nearby early-type spiral galaxy NGC 1371 as part of the MeerKAT HI Observations of Nearby Galactic Objects: Observing Southern Emitters (MHONGOOSE) survey. We found the neutral atomic hydrogen (HI) mostly distributed in a regularly rotating disc with a hole $\sim5$ kpc wide around the galactic centre. The continuum observations reveal, within the HI hole, emission from one of the lowest luminosity AGN known to date and from two unique $\sim10$-kpc wide bipolar bubbles never observed before in this galaxy. The properties of the bubbles suggest that they may result from the impact of the low-power radio jet propagating within the gaseous disk instead of perpendicular to it. We found indication for jet-induced ionised outflows within the HI hole but no molecular gas (upper limit of $M_{\text{H$_2$}}<2\times10^5\text{ M$_\odot$}$) is detected. The emerging picture is that the gas in the central regions has been rapidly depleted by the stellar bar or, despite its low power, the AGN in NGC 1371 is efficiently heating and/or removing the gas through the jets and possibly by radiative winds, leading to the inside-out quenching of the galaxy.

We examine, from first principles, the angular power spectrum between the kinematic Sunyaev-Zel'dovich effect (kSZ) and the reconstructed galaxy momentum - the basis of existing and future "kSZ stacking" analyses. We present a comprehensive evaluation of all terms contributing to this cross-correlation, including both the transverse and longitudinal modes of the density-weighted velocity field, as well as all irreducible correlators that contribute to the momentum power spectrum. This includes the dominant component, involving the convolution of the electron-galaxy and velocity-velocity power spectra, an additional disconnected cross-term, and a connected non-Gaussian trispectrum term. Using this framework, we examine the impact of other commonly neglected contributions, such as the two-halo component of the dominant term, and the impact of satellite galaxies. Finally, we assess the sensitivity of upcoming CMB experiments to these effects and determine that they will be sensitive to the cross-term, the connected non-Gaussian trispectrum term, the two-halo contribution and impact of satellite galaxies, at a significance level of $\sim 4-6 \sigma$. On the other hand, the contribution from longitudinal modes is negligible in all cases. These results identify the astrophysical observables that must be accurately modelled to obtain unbiased constraints on cosmology and astrophysics from near-future kSZ measurements.

Gas-phase metallicity is a fundamental parameter that helps constrain the star-forming history and chemical evolution of a galaxy. Measuring electron temperature through auroral-to-strong line ratios is a direct approach to deriving metallicity. However, there is a longstanding discrepancy between metallicity measured through the direct method and that based on the photoionization models. This paper aims to verify and understand the discrepancies. We bin ~ 1.5 million spaxels from SDSS-IV MaNGA according to metallicity and ionization parameters derived from theoretical strong-line calibrations. We stack the spectra of spaxels within each bin and measure the flux of strong lines and faint auroral lines. Auroral lines for [OII], [SII], [OIII], and [SIII] are detected in the stacked spectra of most bins, and the [NII] auroral line is detected in fewer bins. We apply an empirical method to correct dust attenuation, which makes more realistic corrections for low ionization lines. We derive electron temperatures for these five ionic species and measure the oxygen and sulfur abundances using the direct method. We present the resulting abundance measurements and compare them with those model-calibrated strong-line abundances. The chemical abundances measured with the direct method are lower than those derived from the photoionization model, with a median of 0.09 dex. This discrepancy is smaller compared to the results based on other metallicity calibrations previously reported. However, we notice that the direct method could not account for the variation in ionization parameters, indicating that the precise calibration of metallicity using the direct method has yet to be fully realized. We report significant discrepancies between data and the photoionization model, which illustrates that the one-dimensional photoionization model is incapable of representing the complexity of real situations.

In this study, we introduce SEDust, a pipeline designed to identify the best-fitting spectral energy distributions from the outputs of the DUSTY code and compare them to observational data. The pipeline incorporates a grid of 24000 models, enabling robust fitting for both carbon- and oxygen-rich AGB stars. It calculates key physical parameters, including luminosity, optical depth, and mass-loss rate, and produces the corresponding best-fit SED plots. Using SEDust, we derived the specific mass-return rates for the galaxies NGC 147 and NGC 185. The specific mass-return rate of AGB stars in NGC 147 is $8.13 \times 10^{-12} \mathrm{yr}^{-1}$, while in NGC 185 it is $6.52 \times 10^{-11} \mathrm{yr}^{-1}$. These results indicate that the mass loss from evolved stars alone cannot account for the total mass budget required to sustain these galaxies, highlighting the need for additional sources or mechanisms of mass replenishment to resolve the observed discrepancies.

Since ultra-high-energy cosmic rays (UHECRs) are electrically charged particles, they are deflected by magnetic fields. Those magnetic fields can act as lenses, altering their trajectories and (de)magnifying their apparent source images. These deflections of UHECR trajectories can lead to phenomena such as the appearance of multiple images of an extragalactic source. In this study, we investigate the influence of the Galactic Magnetic Field (GMF) on the propagation of UHECRs, considering four different realistic models for the GMF: the PT11, the JF12, the UF23, and the KST24 models. We investigate how an isotropic flux on Earth would have entered the edge of the Galaxy for different rigidity values from 1 to 100 EV. In addition, we investigate the appearance of multiple images of astrophysical point sources. Furthermore, we analyze the modification of the cosmic ray flux from a source as a function of the rigidity and its dependence on the chosen GMF model. Since the deflection induced by the magnetic field depends on the rigidity of the particle, the effects vary among different nuclear species. Consequently, our findings can have implications for interpreting mass-composition and anisotropy observations, as the rigidity-dependent deflections directly alter the observed UHECR arrival direction distribution.

The hydrodynamics of low-angular-momentum, multi-transonic, axisymmetric, inviscid accretion flow onto a rotating black hole has been systematically investigated using three distinct disc geometries and two thermodynamic equations of state, within the framework of a pseudo-Kerr potential. To enhance astrophysical realism, the study incorporates a multi-component galactic potential, modeling the influence of the surrounding stellar distribution, dark matter, and hot gas with the central blackhole. Our analysis reveals that the inclusion of the galactic potential induces subtle yet noteworthy shifts in the locations of sonic points. This effect is particularly pronounced in the vertical equilibrium disc model, where the region allowing for shock formation undergoes significant modification. The nature of critical points is determined by analyzing the eigenvalues of the corresponding stability matrix, establishing that multi-transonicity is restricted to a finite range of angular momentum. Shock strength and associated dynamic \& thermodynamic quantities-such as mach number, pressure, density and temperature-are found to vary sensitively with galactic parameters, and are illustrated through comprehensive parametric plots. Additionally, a time-dependent linear perturbation analysis, demonstrates that the governing perturbation equations retain their structural form even in the presence of a galactic potential. The flows remain stable under adiabatic, radially propagating perturbations. Interestingly, the perturbative framework naturally gives rise to an emergent acoustic metric, identifying the system as a classical analogue of gravity. The corresponding acoustic surface gravity is analytically derived and shown to exhibit a dependence on both the spin of the black hole and the characteristics of the surrounding galactic environment.

Dark matter (DM) candidates, such as Weakly Interacting Massive Particles (WIMPs), can annihilate to Standard Model particles, subsequently producing gamma rays. In this work, we search for DM-induced gamma-ray signals from Coma Berenices dwarf spheroidal galaxy (CBe dSph) using approximately 25 hours of observations carried out by the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) Telescope, located at Roque de los Muchachos Observatory, La Palma, Spain. Building upon preceding analyses in the gamma-ray regime, we extend the DM search into three dimensions by incorporating spatial information from the assumed DM-density distribution. This approach enhances sensitivity by leveraging both energy and spatial characteristics of the expected signal. The three-dimensional search for a faint signal necessitates the construction of a background model, leading to the proposal of the exclusion-rotation method. This method stacks all observations, excludes the source region, and corrects for the Azimuth-dependent acceptance of the telescopes by rotating the model. Furthermore, the open-source Python package TITRATE is presented, introducing Asimov datasets to the high-level analysis tool Gammapy for the approximation of the test statistic. No evidence of a DM-induced signal for annihilation to $b\bar{b}$, $W^+W^-$, $\mu^+\mu^-$, and $\tau^+\tau^-$ and DM masses $m_\chi$ between 0.17 TeV and 100 TeV in CBe dSph is found. Consequently, the first upper limits on the thermally averaged cross-section in energy and spatial dimensions using TITRATE are set, leading to a sensitivity improvement over previous results by MAGIC with respect to the assumed DM density in the target halo. The development of the Asimov method for DM search reduces the need for Monte Carlo simulations, paving the way for computationally efficient and scalable large-scale analyses across multiple targets and cosmic messengers.

We present a comprehensive investigation into the phenomenological consequences of axion-like particle (ALP) mediated dark matter (DM) on neutron star (NS) structure. Using a relativistic mean-field framework with non-linear mesonic self-interactions constrained by nuclear data and astrophysical observations, we explore the DM parameter space spanning $m_\chi \in [0, 1000]~\mathrm{GeV}$ and $q_f \in [0, 0.06]~\mathrm{GeV}$, generating over 30,000 equations of state (EoSs). Two representative hadronic EoSs are employed, a stiff (EoS1) and a soft (EoS18), with explicit inclusion of the crustal EoS. A multi-tiered statistical filtering scheme, combining voting, likelihood, and kernel density estimation scores, is applied using constraints from radio and X-ray pulsars, GW170817, and the low-mass compact object HESS J1731-347. We find that models satisfying the PSR J0614$-$3329 radius bound automatically comply with HESS, positioning ALP-mediated DM as a viable explanation for low-mass compact objects while still supporting $2\,M_\odot$ NSs. For the stiff EoS, we obtain $m_\chi \gtrsim 43~\mathrm{GeV}$, with score-weighted posteriors favoring $q_f = 0.034^{+0.020}_{-0.012}$ and a broad allowed DM mass range $m_\chi \in [101, 949]~\mathrm{GeV}$ (median $\sim 466$ GeV). The soft EoS yields no strict lower bound, though large $m_\chi$--$q_f$ combinations are disfavored. A high-precision supervised regression model built with AutoGluon achieves $R^2 > 0.998$ for inferring DM parameters from NS observables. Feature analysis reveals $m_\chi$ is constrained by structural ratios such as $R_{1.6}/R_{1.4}$, whereas $q_f$ is set mainly by the tidal deformability $\Lambda_{1.4}$.

The discovery of outsiders in the form of unusual, rare, or even unknown object types is important as they can provide useful information about otherwise hidden physical phenomena and processes. The present study takes advantage of the fact that the automated spectroscopic pipeline of the Sloan Digital Sky Survey (SDSS) occasionally assigns uncommon spectra to high-redshift QSOs. This paper presents an analysis of about 4000 spectra that are QSOs with redshifts z > 4.5 according to the spectroscopic pipeline of the SDSS DR16. It turns out that, after excluding non-classifiable spectra of low quality and those from three special plates, only 26 % are high-z QSOs, 50 % are QSOs at lower redshifts, 16 % are galaxies, and 8 % are stars. A significant proportion of the latter three categories prove to be unusual and are re-assigned here to a variety of rare types. The results of the re-evaluation are summarised in a catalogue.

The Cherenkov Telescope Array Observatory (CTAO) is going to be the leading observatory for very-high-energy gamma-rays over the next decades. Its unique sensitivity, wide field of view, and rapid slewing capability make the CTAO especially suited to study transient astrophysical phenomena. The CTAO will analyse its data in real-time, responding to external science alerts on transient events and issuing its own. The Science Alert Generation (SAG) automated pipeline, a component of the Array Control and Data Acquisition (ACADA) software, is designed to detect and issue candidate science alerts. In this work, we present the current development status of SAG-SCI, the SAG component responsible for the real-time, high-level analysis of CTAO data. The SAG-SCI pipelines receive gamma-ray data from multiple reconstruction lines, merge them, store them in a database, and trigger several parallel scientific analyses on the latest data. These analyses include estimating target significance and flux, producing sky maps and light curves, and conducting blind searches for sources within the field of view. We execute SAG-SCI on a set of simulated gamma-ray data, detecting the simulated sources and accurately reconstructing their flux and position. We also estimate the systematic errors introduced by the analysis and discuss the results in relation to the generation of candidate science alerts.

The relation between metallicity and galaxy mass (the so-called mass-metallicity relation) is the strongest and most prominent among scaling relations between chemical enrichment and galactic properties. However, it is unclear whether this relation primarily traces metal retention or the integrated production of metals, as past studies have obtained contrasting results. We investigate this issue through an extensive Random Forest and Partial Correlations analysis of spectral cubes of 4,500 galaxies from the MaNGA survey. We find that stellar mass ($\rm M_*$) and baryonic gravitational potential ($\rm \Phi_* = M_*/R_e$) are the two most important quantities determining gas metallicity in galaxies. However, their relative roles strongly depend on the galactocentric radius -- the metallicity within 1~$\rm R_e$ depends primarily on the stellar mass, while the metallicity at radii beyond 1.5~$\rm R_e$ depends primarily on the gravitational potential. This finding can be interpreted in terms of metals in the central region ($\rm R\leq 1~R_e$) being mostly bound, regardless of the global gravitational potential and, therefore, the metallicity is determined primarily by the cumulative production of metals (hence the integrated star formation history, i.e. $\rm M_*$); by contrast, in the galactic peripheries the retention of metals depends more critically on the gravitational potential, hence the stronger dependence of the metallicity on $\rm \Phi_*$ at large radii. Our finding reconciles apparent discrepancies between previous results. Finally, we find that the Star Formation Rate is the third most important parameter (after $\rm M_*$ and $\rm \Phi_*$) in determining the metallicity, as expected from the Fundamental Metallicity Relation.

The millisecond pulsar PSR J1713+0747 is a high-priority target for pulsar timing array experiments due to its long-term timing stability, and bright, narrow pulse profile. In April 2021, PSR~J1713$+$0747 underwent a significant profile change event, observed by several telescopes worldwide. Using the broad-bandwidth and polarimetric fidelity of the Ultra-Wideband Low-frequency receiver on Murriyang, CSIRO's Parkes radio telescope, we investigated the long-term spectro-polarimetric behaviour of this profile change in detail. We highlight the broad-bandwidth nature of the event, which exhibits frequency dependence that is inconsistent with cold-plasma propagation effects. We also find that spectral and temporal variations are stronger in one of the orthogonal polarisation modes than the other, and observe mild variations ($\sim 3$ - $5\,\sigma$ significance) in circular polarisation above 1400 MHz following the event. However, the linear polarisation position angle remained remarkably stable in the profile leading edge throughout the event. With over three years of data post-event, we find that the profile has not yet recovered back to its original state, indicating a long-term asymptotic recovery, or a potential reconfiguration of the pulsar's magnetic field. These findings favour a magnetospheric origin of the profile change event over a line-of-sight propagation effect in the interstellar medium.

Most GRB X-ray afterglow light curves are characterised by a plateau, followed by a normal power-law decay interpreted as afterglow emission. Despite the numerous alternative interpretations, the origin of the plateau remains unclear. In the early years of Swift, it was suggested that the plateau might be afterglow radiation, that started before the prompt gamma-ray emission, and its time profile would be an artefact of assuming the start time of the prompt gamma-ray emission as zero time (the so-called "prior activity model"). We aim to test this scenario by leveraging the current Swift sample of early X-ray afterglows of GRBs with measured redshifts. We modelled the GRB rest-frame X-ray afterglow luminosities assuming a simple power-law with the true reference time preceding the prompt gamma-ray emission trigger time by T_0 and the X-ray luminosity L_0 at the trigger time as free parameters. For 90% GRBs of our sample, the model provided a successful description. In 10 cases the afterglow peak is identified and modelled appropriately. Using the 300 GRBs with accurate parameters' estimates, we confirm the anti-correlation between L_0 and T_0 with 0.7 dex scatter. In addition, selecting the subsample of 180 from the literature with reliable estimates of isotropic-equivalent energy E_gamma,iso, peak luminosity L_gamma,iso, and intrinsic peak energy E_p,i of the nuFnu spectrum of the prompt gamma-ray emission, we find a correlation between L_0, T_0, and E_gamma,iso (0.4 dex scatter) over nine decades in L_0 and common to all kinds of GRBs. The afterglow likely begins in most cases before the start of the detected prompt gamma-ray emission. As also suggested by the recent discoveries of Einstein Probe of X-ray emission starting long before the prompt gamma-rays, our results suggest that the occurrence of prior activity could be much more frequent than what has tacitly been assumed so far.

In Epoch 2 of the 2024 PDC25 Hypothetical Asteroid Impact Scenario, an asteroid is confirmed to be on a collision course with the Earth, and its size and surface composition have been well characterized via a flyby mission. A kinetic impactor deflection strategy is the most technologically mature path in order to mitigate this threat. Our goal is to constrain the possible range in momentum transfer coefficients, with implications for the number of impactors and the disruption risk. We conduct a series of numerical simulations, using a shock physics smoothed particle hydrodynamics code, in which we vary the impact velocity, cohesive properties and physical properties (mass / porosity) of the target asteroid. Given a judiciously chosen impactor mass, we show that the momentum transfer coefficient range is capable of a moderate-to-large enhancement of the asteroid deflection, yet keeps the disruption risk firmly at bay. These results are generally unique in having higher impact velocities compared to most previous studies.

Understanding the complex interactions between convection, magnetic fields, and rotation is key to modeling the internal dynamics of the Sun and stars. Under rotational influence, compressible convection forms prograde-propagating convective columns near the equator. The interaction between such rotating columnar convection and the small-scale dynamo (SSD) remains largely unexplored. We investigate the influence of the SSD on the properties of rotating convection in the equatorial regions of solar and stellar convection zones. A series of rotating compressible magnetoconvection simulations is performed using a local f-plane box model at the equator. The flux-based Coriolis number Co is varied systematically. To isolate the effects of the SSD, we compare results from hydrodynamic (HD) and magnetohydrodynamic (MHD) simulations. The SSD affects both convective heat and angular momentum transport. In MHD cases, convective velocity decreases more rapidly with increasing Co than in HD cases. This reduction is compensated by enhanced entropy fluctuations, maintaining overall heat transport efficiency. Furthermore, a weakly subadiabatic layer is maintained near the base of the convection zone even under strong rotational influence when the SSD is present. These behaviors reflect a change in the dominant force balance: the SSD introduces a magnetostrophic balance at small scales, while geostrophic balance persists at larger scales. The inclusion of the SSD also reduces the dominant horizontal scale of columnar convective modes by enhancing the effective rotational influence. Regarding angular momentum transport, the SSD generates Maxwell stresses that counteract the Reynolds stresses, thereby quenching the generation of mean shear flows. These SSD effects should be accounted for in models of solar and stellar convection.

The first experimental formation of thiocarbonic acid (H2CS3) is presented in this work from low-temperature interstellar ice analogs composed of hydrogen sulfide (H2S) and carbon disulfide (CS2) exposed to electron irradiation simulating the impact of galactic cosmic rays (GCRs) on interstellar ices. The recent attention brought to sulfur-bearing molecules, as well as the recent detection of carbonic acid (H2CO3) in the interstellar medium (ISM), invites the study of the interstellar detection of the sulfur counterpart, thiocarbonic acid. However, the interstellar formation pathways of thiocarbonic acid have remained elusive. In this work, thiocarbonic acid was identified in the gas phase during the temperature programmed desorption (TPD) using isomer-selective single photoionization reflectron time-of-flight mass spectrometry (PI-ReToF-MS), suggesting that the hitherto astronomically unobserved thiocarbonic acid represents a promising candidate for future astronomical searches. The formation of H2CS3 isomers was investigated through additional isotopically labeled experiments and the formation mechanisms through quantum chemical studies. These findings unravel a key reaction pathway to thiocarbonic acid and represent a first step toward its possible formation and detection in the ISM, shedding light on the missing sulfur problem.

In dwarf galaxies, nuclear star clusters (NSCs) are believed to primarily form from the migration and merger of globular clusters (GCs), with a possible contribution from in-situ star-forming activity triggered by gas infall. We present the study of NSCs in 41 MATLAS survey dwarf galaxies including ultra-diffuse galaxies (UDGs), as part of a large follow-up imaging program with the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) using the F606W and F814W filters. The sample is biased towards low-surface brightness and large dwarfs, i.e., UDG-like galaxies, and includes two galaxies with a double nucleus, 13 newly identified nucleated dwarfs thanks to HST's high spatial resolution, and five candidate ultra-compact dwarf progenitors. We modeled the NSCs with a Sérsic profile and derived their structural properties and photometry. We find the NSC Sérsic index to increase with the luminosity and stellar mass, while no obvious trend is seen on the effective radius and ellipticity. The faint NSCs tend to have a constant color profile, whereas the bright ones have a bluer center, suggesting that the most massive NSCs in our sample might have experienced a mixed formation scenario, including in-situ star formation. A significant portion of our NSCs tend to be more massive than for other galaxy samples of similar stellar mass, which could be due to some dwarfs ongoing tidal disruption or an initial formation of massive NSCs from multiple GC mergers and in-situ star forming activity. More observations of resolved NSC are needed to be able to infer their formation scenario from the structural properties and photometry in dwarfs.

Studies in the past few decades have investigated young stellar object evolution based on their spectral energy distribution (SED). The SED is heavily influenced not only by evolutionary stage, but also the morphology of the young star. This work is part of the NEMESIS project which is aiming to revisit star formation with the aid of machine learning techniques and provides the framework for this work. In a first effort towards a novel spectro-morphological classification we analyzed young stellar object morphologies and linked them to the currently used observational classes. Thereby we aim to lay the foundation for a spectro-morphological classification, and apply the insights learned in this study in a future, revisited classification scheme. We obtained archival high-resolution survey images from VISTA for approximately 10,000 literature young stellar object candidates towards the Orion star formation complex (OSFC). Utilizing a Self-Organizing map (SOM) algorithm, an unsupervised machine learning method, we created a grid of morphological prototypes from near- and mid-infrared images. Furthermore, we determined which prototypes are most representative of the different observational classes, derived from the infrared spectral index, via Bayesian inference. We present our grids of morphological prototypes of young stellar objects in the near-infrared, which were created purely from observational data. They are thus non-dependent on theoretical models. In addition, we show maps that indicate the probability for a prototype belonging to any of the observational classes. We find that SOMs created from near-infrared images are a useful tool, with limitations, to identify characteristic morphologies of young stellar objects in different evolutionary stages. This first step lays the foundation for a spectro-morphological classification of young stellar objects to be developed in the future.

Galaxy evolution is sensitive to how stars inject feedback into their surroundings. In particular, stellar feedback from star clusters strongly affects gas motions and the baryonic cycle, with more massive clusters having stronger effects. Our previous results show that the star cluster mass distribution in dwarf galaxies depends on feedback, as strong pre-SN feedback, particularly ionizing radiation, results in fewer high-mass clusters. We investigate the mass distribution of gas clouds in dwarf galaxies. Since clusters form from collapsing gas clouds, we expect a similar feedback dependence in both distributions, so we hypothesize that pre-SN feedback yields fewer high-mass clouds. To test this, we use an isocontour analysis at cutoff densities of $10,\ 10^{1.5},\ 10^{2}$ cm$^{-3}$ to identify clouds in dwarf galaxy simulations run with the RAMSES adaptive mesh refinement code. We calculate mass distributions for models with different combinations of SNe, stellar winds, and ionizing radiation. We find that the mass distribution for clouds with $n>100$ cm$^{-3}$ is independent of feedback, but the distribution for complexes with $n>10$ cm$^{-3}$ is more top-heavy in the presence of radiation. Winds do not affect the distribution at any scale. This contradicts our hypothesis that cloud and cluster mass distributions respond similarly to feedback. Instead, the dense cloud mass function shows no feedback dependence, suggesting its shape is set by gravity. We conclude that the cluster mass function must be shaped by intra-cloud feedback regulating star formation and, in the case of radiation, effects on parent cloud temperature. (shortened)

In Titan's atmosphere, the chemistry of small hydrocarbons and nitriles represent an important link from molecular species to the ubiquitous organic haze that gives Titan its characteristic yellow color. Here we present a new search for two previously undetected molecules, triacetylene (C$_{6}$H$_{2}$) and the gas phase dicyanoacetylene (C$_{4}$N$_{2}$), using the Echelon-Cross-Echelle Spectrograph (EXES) instrument aboard the SOFIA (Stratospheric Observatory For Infrared Astronomy) aircraft. We do not detect these two molecules but determine upper limits for their mixing ratios and column abundances. We find the $3\sigma$ upper limits on the uniform volume mixing ratio (VMR) above 100 km for C$_{6}$H$_{2}$ to be $4.3\times10^{-11}$ which is lower than the photochemical model predictions. This new upper limit suggests that the growth of linear molecules is inhibited. We also put a strict upper limit on the uniform VMR for gas phase C$_{4}$N$_{2}$ above 125 km to be $1.0\times10^{-10}$. This upper limit is well below the saturation mixing ratio at this altitude for C$_{4}$N$_{2}$ and greatly limits the feasibility of C$_{4}$N$_{2}$ forming ice from condensation.

Our understanding of the origin of heavy elements beyond iron relies on the rapid neutron capture process (r-process), which accounts for roughly half of their cosmic abundance. However, the extreme neutron-rich conditions required for the r-process involve many nuclei that remain experimentally inaccessible, making theoretical predictions essential. We explore the impact of nuclear masses calculated with the ab initio valence-space in-medium similarity renormalization group, focusing on the region around the N = 82 shell closure. We show that such ab initio mass calculations can refine the r-process predictions compared to global, but more phenomenological mass models. With the ab initio masses, the waiting point of the second r-process peak is strengthened, which leads to an overall slower nucleosynthesis flow, lower abundances of nuclei beyond the peak, and a stronger shift of the third r-process peak.

The Fe xxii doublet has been previously used to determine the density of collisionally ionized emission from magnetic cataclysmic variable stars. We test how this diagnostic doublet behaves for a photoionized plasma with an active galactic nucleus (AGN) spectral energy distribution (SED). We use the photoionized plasma code pion and ~440 ks of archival Chandra HETG for the well-known Seyfert 2 galaxy NGC 1068 to test the behaviour of the Fe xxii doublet in the context of an AGN. This marks the first time these data have been examined with pion. We find that in a photoionized plasma, the Fe xxii doublet is dependent on the density, ionization state, and SED used. Thus, this density diagnostic remains model-dependent. In the context of NGC 1068 the doublet predicts an emission region ~100 rg from the central black hole. This would require a direct line of sight to the central engine, which is at odds with the Seyfert 2 nature of this source. In practice, these results highlight the complexities and challenges of applying photoionized models. With these data, we cannot exclude the possibility of a direct line of sight to the central engine of NGC 1068, but we cannot confirm it. Future observations with instruments such as Athena are needed to explore the Fe xxii doublet further.

We analyze photometric observations of stars, which experienced microlensing events at the considered time, in order to compare the efficiency of detecting exoplanets in observations performed at thirteen different telescopes and with several approaches to the selection of observable events. In constructing an algorithm of the optimal selection of targets for these observations and in comparing the detection efficiencies for several telescopes, we considered models of the night-sky brightness that satisfy the data of infrared observations carried out in 2011 with the Optical Gravitational Lensing Experiment (OGLE) telescope and the RoboNet telescopes (FTS, FTN, and LT) used to search for planets with the microlensing method. The considered models of the night-sky brightness can be used for various observations (not only microlensing events). The time intervals, during which microlensing events can be observed, were determined with accounting for the positions of the Sun and the Moon and the other constraints on the telescope pointing. Our algorithm allows us to determine the already known microlensing events that are accessible for observation with a particular telescope and to select targets, for which the probability of detecting an exoplanet is maximal. The events, which would maximize the probability of detecting exoplanets, were selected for observations. The probability of detecting an exoplanet is usually proportional to the mirror diameter of a telescope. Telescopes with a wider field of view, such as the OGLE, are more effective in finding new microlensing events. To observe different microlensing events, it is usually better to use different nearby telescopes. However, all such telescopes are often better to use for observing the same event in those relatively short time intervals that correspond to the peak brightness of the event.

Recent studies indicate that the formation of planets in protoplanetary disks begins early in the embedded Class 0/I phases of protostellar evolution. The physical and chemical makeup of the embedded phase can provide valuable insights into the process of star and planet formation. This study aims to provide a thorough overview of the various morphologies for molecular emissions observed on disk scales toward nearby embedded sources. We present high angular resolution (0.1", 15 au) molecular line emissions for $^{12}$CO, $^{13}$CO, C$^{18}$O, SO, SiO, DCN, CH$_3$OH, H$_2$CO, and c-C$_3$H$_2$ towards 19 nearby protostellar sources in the context of the Atacama Large Millimeter/submillimeter Array (ALMA) Large Program "Early Planet Formation in Embedded Disks (eDisk)". Emissions in $^{12}$CO are seen towards all sources and primarily trace outflowing materials. A few sources also show high-velocity jets in SiO emission and high-velocity channel maps of $^{12}$CO. The $^{13}$CO and C$^{18}$O emissions are well-known tracers of high-density regions and trace the inner envelope and disk regions with clear signs of rotation seen at continuum scales. The large-scale emissions of $^{13}$CO also delineate the outflow cavity walls where the outflowing and infalling materials interact with each other, and exposure to UV radiation leads to the formation of hydrocarbons such as c-C$_3$H$_2$. Both DCN and CH$_3$OH, when detected, show compact emissions from the inner envelope and disk regions that peak at the position of the protostar. The CH$_3$OH emissions are contained within the region of DCN emissions, which suggests that CH$_3$OH traces the hot core regions. Likewise, a few sources also display emissions in CH$_3$OH towards the outflow. Both SO and H$_2$CO show complex morphology among the sources, suggesting that they are formed through multiple processes in protostellar systems.

Given the mysterious nature of dark matter and dark energy, and the persistent tensions in cosmological data, it is worthwhile exploring more exotic physics in the dark sector, such as a momentum coupling between dark matter and dark energy, specifically in the form of a quintessence field. In this study, using collisionless N-body numerical simulations with a modified version of the RAMSES code, we follow up previous work to investigate the consequences of this model on dark matter halos and their substructures. We consider both the sign of the coupling and the imprints on structure formation and halo properties at a statistical level. We find that there is a clear enhancement (reduction) of substructure if the sign of the coupling is negative (positive) and that the dynamical state of the dark matter halos, particularly host halos, is undervirialised (overvirialised) at redshift zero when compared to uncoupled models or a reference $\Lambda$CDM simulation. Furthermore, positive coupling leads to less concentrated, less cuspy halos, whereas negative coupling leads to the opposite.

Many known exoplanets harbor clouds, which lead to degeneracies in spectroscopic models between particle composition and size. Polarimetry, however, provides independent assessment. Here we report the $7.2 \sigma$ discovery of linearly polarized, scattered light from the hot Jupiter HD 189733b in $B$ band (390 to 475 nm) peaking near quarter phase with $\Delta p = 40.9 \pm 7.1$ ppm. Polarization measurements, obtained with the POLISH2 polarimeter at both Gemini North and the Lick Observatory 3-m, are best explained by silicate (SiO$_2$ or MgSiO$_3$) particles with effective radius $r_\text{eff}=0.038^{+0.047}_{-0.023}$ $\mu$m ($90\%$ confidence). This is broadly consistent with results from both Hubble transmission spectroscopy and JWST secondary eclipse spectroscopy suggesting small, SiO$_2$ scattering particles. It is difficult to reconcile large polarization and moderate Hubble secondary eclipse depth via pure Rayleigh, silicate, or MnS scatterers. The measured polarization of HD 189733b is detected with such high confidence that we place a $2\sigma$ lower limit on its $B$ band geometric albedo of $A_g > 0.26$ with a preferred value of $A_g = 0.6$. This is larger than the prior estimate of $A_g = 0.226 \pm 0.091$ from Hubble secondary eclipse photometry, and it presents HD 189733b as one of the most reflective known exoplanets in $B$ band. It also validates Rayleigh scattering from the exoplanet, as opposed to starspot contamination, as the cause of HD 189733's blue optical slope in transmission spectroscopy. Assuming other known exoplanets harbor atmospheres like HD 189733b, we model dozens to be detectable with at least $5 \sigma$ confidence after one week of Gemini time each.

LS 5039 hosts a high-mass star, and a compact object that might be a strongly magnetized neutron star (NS). This scenario requires a mechanism to power its persistent and strong non-thermal emission. We investigate a mechanism in which the non-steady interaction structure of the stellar and the NS winds can regularly excite NS magnetospheric activity, releasing extra energy and fueling the source non-thermal emission. The NS wind shocked by the stellar wind can recurrently touch the NS magnetosphere, triggering magnetic instabilities whose growth can release extra energy into the NS wind in a cyclic manner. To illustrate and study the impact of these cycles on the two-wind interaction structure on different scales, we performed relativistic hydrodynamics simulations in 2D and 3D with periods of an enhanced power in the NS wind along the orbit. We also used analytical tools to characterize processes near the NS relevant for the non-thermal emission. As the NS wind termination shock touches the magnetosphere energy dissipation occurs, but the whole shocked two-wind structure is eventually driven away halting the extra energy injection. However, due to the corresponding drop in the NS wind ram pressure, the termination shock propagates back towards the magnetosphere, resuming the process. These activity cycles excite strong waves in the shocked flows, intensifying their mixing and the disruption of their spiral-like structure produced by orbital motion. Further downstream, the shocked winds can become a quasi-stable, relatively smooth flow. The recurrent interaction between the NS magnetosphere and shocked wind can fuel a relativistic outflow powerful enough to explain the non-thermal emission of LS 5039. A magnetospheric multipolar magnetic field much stronger than the dipolar one may provide the required energetics, and help to explain the lack of evidence of a recent supernova remnant.

We investigate the spectra of Earth-like planets but with different axial rotation periods. Using the general circulation model of the atmosphere and considering the atmospheric circulation lasting for two years, we calculated the radiation spectra of the Earth and the exo-Earth rotating with periods of 1 and 100 days, respectively. The radiation spectra of the atmospheres were calculated with the SBDART code. We analyzed the spectrum of upward radiation at altitudes of 1 and 11 km in wavelength ranges of 1 to 18 and 0.3 to 1 micron. The following common features were obtained for the Earth and the exo-Earth: (1) the planets exhibit a wide absorption band of CO2 around 14 micron; (2) the radiation spectra at different locations near the equator show no significant differences; and (3) if the spectrum is integrated over the entire disk of the Earth/exo-Earth, the difference in the spectral signal obtained in observations from different directions becomes substantially lower than the difference between the results of observations of individual regions of the planets. The differences in the spectra of exoplanets, which differ from the Earth only in axial rotation period, are comparable to the differences associated with changes in the angle of viewing the planet. Consequently, if the observation angle is not known, the analysis of the spectrum of the planet cannot be used to determine its axial rotation period. The maximal differences in the spectra of Earth-like exoplanets were obtained for wavelengths of about 5-10 and 13-16 micron. By analyzing the spectrum at wavelengths around 9.4-10 micron, we can determine whether the atmosphere of the exoplanet contains ozone or not. Since ozone is essential for life, the 9.4-10 micron band may be important for future observations of Earth-like exoplanets.

Accurate measurements of young stellar cluster internal dynamics provide crucial insights into their formation. With Gaia, we are now able to trace stellar motions and study the dynamics of star clusters with unprecedented precision, but this requires a reliable list of probable members. We examine a 2 deg-radius region in Cepheus OB4, centered on the young cluster Berkeley 59, to build a reliable candidate member list, enabling the study of the cluster's structure, kinematics, and stellar population. We compiled a catalog of optical and near-infrared photometry, along with precise positions and proper motions from Gaia DR3, for sources in the Cepheus OB4 field. Membership probabilities were determined using a probabilistic random forest algorithm and further refined by requiring HR diagram positions consistent with a young age. From a list of 1030 probable members, we estimate a distance of 1009+-12 pc to Berkeley 59. Masses, extinction, and ages were derived by fitting the spectral energy distributions to atmospheric and evolutionary models, while internal dynamics was analyzed using proper motions relative to the cluster's mean motion. Berkeley 59 exhibits an asymmetric expansion pattern with velocity increasing outward and a preferred motion toward the north. The IMF between 0.4 and 7 MSun follows a single power law (dN/dM \propto M**-alpha), with the slope alpha=2.3+-0.3, consistent with Salpeter's slope and previous studies in the region. The region's median age, estimated from the HR diagram, is 2.9 Myr. The velocity dispersion of Berkeley 59 exceeds the virial velocity dispersion derived from its total mass (650+-30 MSun) and half-mass radius (1.71+-0.13 pc). The 2D motions of a stellar group located about 1 deg north of Berkeley 59 provide further support for the previously proposed triggered star formation scenario. (Abridged)

The escape of Lyman-$\alpha$ (Ly$\alpha$) radiation encodes valuable information on the neutral interstellar medium and is often used as a proxy for the escape of ionizing photons. Yet, the theory of Ly$\alpha$ transfer through anisotropic gas distributions remains underdeveloped. We present Monte Carlo radiative transfer simulations of Ly$\alpha$ propagation through porous, inhomogeneous neutral gas, systematically exploring the effects of channel geometry, outflows, dust, and lognormally distributed column densities. We find that Ly$\alpha$ photons do not preferentially escape through the lowest-column-density pathways, but instead traverse channels of substantial optical depth, leading to suppressed central flux and the absence of strongly beamed escape. Subdividing channels has little impact, indicating that geometry and covering fraction are more important than porosity. Channels containing moderate amounts of neutral hydrogen alter escape in characteristic ways, including the appearance of quadruple-peaked spectra, which can be captured by a simple flux-channel relation. Outflows reshape the spectra by facilitating escape through dense media, redshifting photons and blending central features, while dust modulates the visibility of small channels by suppressing flux at line center; in both cases, we develop an analytical model that predicts the resulting central fluxes. Extending to lognormal column density fields, we show that Ly$\alpha$ photons probe a broad range of optical depths, producing skewed spectra that can be approximated by weighted sums of homogeneous models. Our results have direct implications for using Ly$\alpha$ as a tracer of gas properties and ionizing photon escape; for instance, spectra suggestive of high column densities may nonetheless allow LyC leakage through narrow channels.

An analysis of the tilt angles of the active regions in 15-24 activity cycles was performed. We used data from measurements of magnetic fields in the sunspot umbra in the period 1918 -2019 at the Mount Wilson Observatory, as well as the tilt angles of active regions in 'white' light at the Kodaikanal and Mount Wilson observatories in activity cycles 15-21. The mean tilt angles of active regions $\overline{\gamma}$ and the slope $\mu$ from latitude $\theta$ in the activity cycles are considered. Low-latitude bipoles are the most important in predicting the strength of solar cycles. In this work, we selected the cutoff latitude $\theta_{cut}$ at which the highest correlation is observed with the strength of the next activity cycle for active regions with latitude $\theta<\theta_{cut}$. It was found that for magnetic field measurement data, the highest correlation of the parameters $\overline{\gamma}$ and $\mu$ with the strength of the next solar activity cycle is characteristic of bipoles in the equatorial zone with $\theta<\theta_{cut}\approx 14.2^o$. For white light observation data, $\theta_{cut}\approx 8.5^o$ for Mount Wilson observatory and $\theta_{cut}\approx 9.4^o$ for Kodaikanal observatory.

The spatial distribution of chemical elements in the Galactic disk provides key constraints on models of galaxy evolution. However, studies using planetary nebulae (PNe) as tracers have been historically limited by large uncertainties in their distances. To overcome the long-standing distance uncertainties, we recalibrated the H$\alpha$ surface brightness-radius relation (Frew et al. 2016) with Gaia DR3 parallaxes, deriving statistical distances for 1,200 PNe and Bayesian distances for 419 objects with reliable parallaxes. Adopting Bayesian values preferentially, we determined the O/H radial gradient for 230 disk PNe. We tested three models: a single linear gradient, a segmented fit with one break, and a segmented fit with two breaks. Although model selection is statistically inconclusive, segmented fits indicate a change in slope near the solar radius ($R \sim 8$ kpc), with a flatter or slightly positive gradient inward and a steeper negative gradient outward. This feature may reflect changes in star formation efficiency driven by the Galactic bar or the corotation resonance of the spiral arms. Comparison with other tracers - Cepheids, red giants, and open clusters - shows qualitative consistency. The two-dimensional O/H distribution in the Galactic plane supports the adopted distances and reveals modest azimuthal asymmetry, with enhanced abundances near the bar at positive longitudes, and a bimodal abundance structure between the inner and outer solar regions. Our results provide new constraints on the chemical evolution of the Milky Way, the impact of non-axisymmetric structures, and the possible existence of distinct radial abundance regimes across the Galactic disk.

The light odd-Z elements P, Cl, K, and Sc are underproduced in galactic chemical evolution models compared to spectroscopic observations of stars in the Milky Way. The most promising solution to this puzzle is that some massive stars experience O-C shell mergers boosting their yields through dynamic, convective-reactive nucleosynthesis. We report how convective macro physics based on 3D $4\pi$ hydrodynamic simulations impacts production in the O shell by post-processing the $\mathrm{M_{ZAMS}}=15~\mathrm{M_\odot}$ $Z=0.02$ model from the NuGrid dataset. We explore a mixing downturn, boosted velocities, reduced ingestion rate, and convective quenching. Across 24 mixing cases, the pre-explosive yields for [P/Fe], [Cl/Fe], [K/Fe], and [Sc/Fe] are modified by $[-0.33,0.23]~\mathrm{dex}$, $[-0.84,0.64]~\mathrm{dex}$, $[-0.78,1.48]~\mathrm{dex}$, and $[-0.36,1.29]~\mathrm{dex}$, respectively. Cases with a convective downturn with the fastest ingestion rate have the largest enhancement, and production is non-monotonic with boosted velocities. Which reactions are most important for the convective-reactive element production pathways depends on the mixing. We parameterize production of $^{40}\mathrm{K}$ ($t_{1/2} = 1.248~\mathrm{Gyr}$), an important radiogenic heat source for younger ($2{-}3~\mathrm{Gyr}$) rocky planets and find a yield variation exceeding three orders of magnitude. This range of initial abundances for $^{40}\mathrm{K}$ implies the early geodynamic behaviour of silicate mantles in rocky planets can differ greatly from that of Earth. These results underscore the importance of investigating the 3D macro physics of shell merger convection through hydrodynamic simulations to develop a predictive understanding of the origin and variability of the light odd-Z elements and the $^{40}\mathrm{K}/\mathrm{K}$ ratio in planet host stars.

Sub-Neptune planets, with sizes and masses between those of Earth and Neptune, dominate the exoplanet population. Sub-Neptunes are expected to be the most diverse family of the exoplanet population, potentially including rocky gas dwarfs, water worlds, and mini-Neptunes, with a wide range of atmospheric, surface and interior conditions. With no analogue in the solar system, these planets open fundamental questions in planetary processes, origins, and habitability, and present new avenues in the search for life elsewhere. Atmospheric observations with the James Webb Space Telescope (JWST) are enabling unprecedented characterization of sub-Neptunes, starting with the first detections of carbon-bearing molecules in the habitable zone sub-Neptune K2-18 b. We survey the present landscape of JWST observations and atmospheric inferences of sub-Neptunes, which in turn provide key insights into their atmospheric processes, internal structures, surface conditions, formation pathways and potential habitability. The atmospheric abundance constraints reveal evidence of chemical disequilibria, and insights into the planetary mass-metallicity relation in the sub-Neptune regime. Similarly, for sub-Neptunes with H$_2$O-rich interiors, increasing atmospheric H$_2$O abundances with the equilibrium temperature may indicate the existence of a critical temperature for transition from H$_2$ dominated atmospheres with tropospheric cold traps to those with steamy atmospheres. The chemical abundances also provide initial evidence for diverse planet types, from potentially habitable hycean worlds to steam worlds with super critical water layers. These planet types serve as benchmarks for an emerging taxonomy of volatile-rich sub-Neptunes as a function of their equilibrium temperature and atmospheric extent, heralding a new era of chemical classification of low-mass exoplanets with JWST.

The formation process of galaxy groups is not yet fully understood. In particular, that of fossil groups (FGs) is still under debate. Due to the relative rarity of FGs, large samples of such objects are still missing. The present paper aims to analyse the properties of groups in various evolutionary stages (FGs, "almost" FGs, and non-FGs), and to increase the sample of FG candidates. We have spectroscopically observed galaxies in four groups and ten candidate FGs detected in the Canada France Hawaii Telescope Legacy Survey. We searched for substructures by applying the Serna-Gerbal dendrogram method to analyse the dynamical structure of each group. By applying the FIREFLY software to the continuum and PIPE_VIS to the emission lines, we derived the stellar population properties in various regions for each group. A roughly continuous variation in properties is found between a group that is still building up (XCLASS 1330), a well-formed massive group (MCG+00-27-023), a dynamically complex non-FG (NGC 4065), and a near-FG (NGC 4104). We also optically confirm two FGs in the Canada France Hawaii Telescope Legacy Survey, but their X-ray luminosity is still unknown. We observe that the lower the mass of the substructure, the more recent the stellar population in the considered groups. We also show an apparent lack of high-mass substructures for low-metallicity systems. These results are consistent with the generally adopted model of energy transfer during interactions of the galaxies with the group and cluster potential wells. Furthermore, the fossil status of a group might be related to the large-scale environment. Therefore, studying the positions of non-FGs, near-FGs, and FGs within the cosmic web can provide insights into the process of how fossil systems come into being in the Universe.

Optical Forbidden Emission Lines (FELs) come from transitions with long radiative decay times needing low density gas where collisions between atoms are rare. They are produced in the outflows driven by young stellar objects. These lines trace distinct velocity components, including a Low Velocity Component (LVC), which may be tracing a magneto hydrodynamic (MHD) or photoevaporative (PE) wind. We study the jet and LVC of the star DG Tau, whose jet velocity has decreased since 2006. We aim to investigate a link between the high velocity jet and the LVC and clarify the LVC origin as an MHD or PE wind by studying spectral \& spatial changes over time. Using kinematic fitting \& spectro-astrometry, we analyse three epochs of spectra spanning ~18 years. A ~100 km/s decrease in velocity from 2003 to 2021 aligns with known slowing of the jet. Fitting of the [O I] {\lambda}6300, [O I] {\lambda}5577, and [S II] {\lambda}6731 lines reveal complex FEL profiles, with up to six blue-shifted components and a redshifted wing, in agreement with Chou et al. (2025). We see three LVC sub-components (LVC-H, LVC-M, and LVC-L) that are consistent with entrained jet material, disk wind, and dense upper disk atmosphere respectively. While jet components vary in time, the LVC remains quite stable, with changes in the relative brightness of each sub-component. The results cannot distinguish between a MHD or PE wind origin for the LVC. A limit of less than 2 au is put on the de projected height of the LVC-M in [O I] {\lambda}5577, where there is no jet contribution. This supports a disk wind and may favor an MHD wind origin. The near constant peak velocity of LVC-M needs further study in context of a shared origin for jets and MHD winds. Future work needs observations with higher spectral resolution and time cadence to resolve blended components and examine a possible time lag between changes in the jet and LVC.

I find that the dust morphologies in some core-collapse supernova (CCSN) remnants (CCSNRs) possess jet-shaped morphologies, and propose that the properties of the jets that explode the CCSNe and their interaction with the core and envelope (if it exists) are among the factors that determine the amount of dust formed and its morphology. I find that some of the dust-rich structures in the CCSNRs Cassiopeia A and the Crab Nebula are distributed in point-symmetric morphologies, and that the dust in SN 1987A follows the bipolar morphology of the inner ejecta. Earlier studies attributed these morphologies in these CCSNRs to shaping by jets in the framework of the jittering jets explosion mechanism (JJEM). These dust morphologies suggest, in the framework of the JJEM, that exploding jets enhance dust formation in CCSNRs. This study adds to the variety of processes that CCSN exploding jets are involved in and to the establishment of the JJEM as the explosion mechanism of CCSNe.

Be stars are widely considered to be the product of binary interaction. However, whether all Be stars are formed via binary interaction is unclear, and detailed estimates of the multiplicity of Be stars and characterization of their components are required. In this study, we present speckle observations of 76 Be stars taken using the Gemini North and South speckle imagers spanning angular separations of 20 mas-1.2", reaching contrasts ${\Delta}$m~5-6 mag at separations around 0.1". We identify 11 (6 previously unreported) binaries having separations in the 10-1000 au range, and ${\Delta}$m between 0.8-5 mag in our sample. Using archival data to search for components outside our visibility range, we add further multiples (16), which include three triples, leading to a total of 24 multiple systems. Our findings rule out a multiplicity fraction >27% at the 3${\sigma}$ level within the speckle observations separation range and detection limits. Future homogeneous spectroscopic/interferometric observations are essential to probe the inner separations, and along with analysis of available astrometry can cover the entire separation range to characterize the multiplicity fraction, and evolutionary scenario of Be stars.

We construct a variety of bound states of Dirac magnetic monopoles in product $U(1)$ gauge theories, that make up a unit charge Dirac magnetic monopole of the unbroken $U(1)$ gauge group. The size of the bound states is determined by the balance between the repulsive magnetic Coulomb force of the unbroken $U(1)$ gauge group and the attractive force from the tension of the magnetic flux tubes of the broken $U(1)$ gauge groups. These bound states are extensions of the configuration first studied in arXiv:1608.06951. We dub this type of configurations ``Magnetic Monopole Molecules'' (MMMs). Besides some illustrative examples of MMMs made of a small number of constituent magnetic monopoles, a method to combine smaller MMMs to construct larger MMMs is presented. Implications for the weak gravity conjecture are also discussed.

We analyze a new class of static, smooth geometries in five-dimensional supergravity, dubbed $\mathcal{W}$-solitons. They carry the same mass and charges as four-dimensional Reissner-Nordström-like black holes but replace the horizon with a Kaluza-Klein bubble supported by electromagnetic flux. These solutions provide analytically tractable prototypes of black hole microstates in supergravity, including a new, astrophysically relevant neutral configuration involving a massless axion field. Focusing on photon scattering and scalar perturbations, we compute their key observables. We find that $\mathcal{W}$-solitons feature a single photon sphere, qualitatively similar to that of the black hole but with quantitative differences. They have only short-lived quasinormal modes (QNMs), as black holes, while long-lived echo modes seen in other ultracompact horizonless objects are absent. As a result, the ringdown closely resembles that of a black hole while still showing sizable deviations. The latter are at the ${\mathcal{O}}(10\%)$ level, compatible with the recent measurement of GW250114 and potentially falsifiable in the near future. Finally, we show that $\mathcal{W}$-solitons are stable under scalar perturbations. Our results underscore the qualitative similarities between $\mathcal{W}$-solitons and black holes, reinforcing their relevance as smooth black hole microstate prototypes.

Supernova (SN) 1987A is a celebrated laboratory in searches for gamma-ray flashes produced by the radiative decay of sub-GeV particles such as axion-like particles (ALPs), sterile neutrinos, and novel gauge bosons. At large couplings, however, particles decay rapidly inside the stellar envelope, which results in a suppression of the signal. Focusing on the prototypical example of ALPs with a photon coupling, we show that core-collapse SNe of Type Ic are much less affected by this attenuation, thanks to the compactness of their progenitors ensuing from the loss of their envelope. While Fermi-LAT may miss the brief gamma-ray flash from a single Type Ic SN, their high rate allows for a statistical approach: by stacking many events, we can obtain constraints that significantly surpass those from SN 1987A at large couplings. Our approach can be extended to any feebly interacting particle featuring a decay channel into photons.

The past decade has transformed our ability to observe the Universe. Via gravitational waves, merging black holes and neutron stars can now be directly detected, offering unprecedented opportunities to test General Relativity and explore astrophysics in a new way. Driven by this breakthrough, the next generation of detectors is being developed to observe a wider range of sources with greater precision, ushering in a new era in gravitational-wave astronomy: leveraging black holes as probes of new physics. This thesis investigates how astrophysical environments, such as plasma, dark-matter structures, and clouds of ultralight bosons, affect black holes and their gravitational-wave signatures. After a short overview of gravitational-wave astrophysics, I study three classes of scenarios. (i) Isolated black holes: I examine boson clouds around black holes, their electromagnetic couplings and the role of surrounding plasma. (ii) Ringdown: I show that plasma can strongly modify the ringdown of charged black holes, whereas realistic dark-matter halos produce no detectable deviations even for next-generation detectors. (iii) Inspiral: for extreme-mass-ratio inspirals with boson clouds, I find that orbital resonances typically destroy the cloud unless the orbit is nearly counter-rotating, yielding new and exciting observational signatures. Entering the relativistic regime, I develop a self-consistent perturbative framework to model generic environments in extreme-mass-ratio binaries and apply it to the boson-cloud case. Finally, I construct a model for binaries repeatedly crossing active galactic-nucleus disks and track their long-term orbital evolution. The results of this thesis show how black hole environments shape gravitational-wave signals and open avenues for testing new physics with future observatories such as LISA or the Einstein Telescope.

Phonon sensitive superconducting qubits promise to provide sub-eV energy deposit thresholds, useful for future rare-event experiments looking for interactions from dark matter and neutrinos. We detail here engineering results from a Quantum Parity Detector (QPDs), one of a class of phonon sensitive qubits, and, as a first measurement, show that this device has a quiescent quasiparticle density of $1.8 \pm 0.8 \mu \mathrm{m}^{-3}$, in line with expectation. We also outline an argon ion-mill process for multi-step Josephson Junction fabrication, expanding the sparse literature on this topic, which proves useful in avoiding secondary parasitic junctions.

Ethylene glycol is a prebiotically relevant complex organic molecule detected in interstellar and cometary environments, yet quantitative low-energy electron-ethylene glycol scattering data remain limited for astrochemical modeling. This work presents an R-matrix study of low-energy electron collisions with ethylene glycol over the 0 to 12 eV energy range, using static exchange (SE), static exchange plus polarization (SEP), and configuration interaction (CI) models with 6-311G* and cc-pVTZ basis sets. We compute elastic, excitation, and differential cross sections within a close coupling framework. The dataset offers benchmark inputs for astrochemical models, supporting interpretation of ethylene glycol abundances in space and refining constraints on electron-induced prebiotic pathways.

Stochastic gravitational wave (GW) background is secondarily and inevitably induced by the primordial curvature perturbations beyond the first order of the cosmological perturbation theory. We analytically calculate the integration kernel of the power spectrum of the induced GWs, which is the universal part independent of the spectrum of the primordial curvature perturbations, in the radiation-dominated era and in the matter-dominated era. We derive fully analytic expressions of the GW spectrum when possible. As a minor update, we study the case of the top-hat function as the spectrum of the curvature perturbations. We also discuss generalization in the presence of multiple cosmological eras with different equations of state.

We investigate the propagating modes of New General Relativity (NGR) in second-order linear perturbations in the Lagrangian density (first-order in field equations). The Dirac-Bergmann analysis has revealed a violation of local Lorentz invariance in NGR. We review the recent status of NGR, considering the results of its Dirac-Bergmann analysis. We then reconsider the vierbein perturbation framework and identify the origin of each perturbation field in the vierbein field components. This identification is mandatory for adequately fixing gauges while guaranteeing consistency with the invariance guaranteed by the Dirac-Bergmann analysis. We find that the spatially flat gauge is adequate for analyzing a theory with the violation of local Lorentz invariance. Based on the established vierbein perturbative framework, introducing a real scalar field as a test matter, we perform a second-order perturbative analysis of NGR with respect to tensor, scalar, pseudo-scalar, and vector and pseudo-vector modes. We reveal the possible propagating modes of each type of NGR. In particular, we find that Type 3 has stable five propagating modes, \textit{i.e.}, tensor, scalar, and vector modes, compared to five non-linear degrees of freedom, which results in its Dirac-Bergmann analysis; Type 3 is preferable for the application to cosmology. Finally, we discuss our results in comparison to previous related work and conclude this study.

Astrophysical jets from powerful active galactic nuclei (AGN) have recently been proposed as promising probes of dark matter (DM) in the sub-GeV mass range. AGN launch relativistic jets that accelerate cosmic rays (CRs) to very high energies, which can then interact with their surroundings and produce multiwavelength (MW) emission spanning from radio frequencies to TeV $\gamma$ rays. If DM consists of light particles, their interactions with CRs could lead to an additional cooling mechanism that modifies the expected MW emission. In this work, we analyse the MW spectrum of Markarian 421, a well-studied AGN, using a multizone leptonic jet model that includes the interactions between CR electrons and DM particles. For the first time, we account for the uncertainties in the astrophysical jet dynamics, which have been previously neglected when constraining the CR-DM interactions. By fitting simultaneously jet parameters and DM-electrons interactions, we use the MW data from Markarian 421 to set constraints on the DM-induced CR cooling. We obtain 5$\sigma$ upper limit $\sigma_\text{DM-e} \lesssim 1 \times 10^{-34}~\text{cm}^2$ for a DM mass of $1~{\rm MeV}$. We demonstrate that this is about a factor of five weaker than traditional approaches, implying that properly accounting for degeneracies between jet dynamics and DM interactions is key to derive robust constraints on DM interactions.

The gravitational collapse of collisionless matter leads to shell-crossing singularities that challenge the applicability of standard perturbation theory. Here, we present the first fully perturbative approach in three dimensions by using Lagrangian coordinates that asymptotically captures the highly nonlinear nature of matter evolution after the first shell-crossing. This is made possible essentially thanks to two basic ingredients: (1) We employ high-order standard Lagrangian perturbation theory to evolve the system until shell-crossing, and (2) we exploit the fact that the density caustic structure near the first shell-crossing begins generically with pancake formation. The latter property allows us to exploit largely known one-dimensional results to determine perturbatively the gravitational backreaction after collapse, yielding accurate solutions within our post-collapse perturbation theory (PCPT) formalism. We validate the PCPT predictions against high-resolution Vlasov-Poisson simulations and demonstrate that PCPT provides a robust framework for describing the early stages of post-collapse dynamics.

A first-order, confinement/deconfinement phase transition appears in the finite temperature behavior of many non-Abelian gauge theories. These theories play an important role in proposals for completion of the Standard Model of particle physics, hence the phase transition might have occurred in the early stages of evolution of our universe, leaving behind a detectable relic stochastic background of gravitational waves. Lattice field theory studies implementing the density of states method have the potential to provide detailed information about the phase transition, and measure the parameters determining the gravitational-wave power spectrum, by overcoming some the challenges faced with importance-sampling methods. We assess this potential for a representative choice of Yang-Mills theory with $Sp(4)$ gauge group. We characterize its finite-temperature, first-order phase transition, in the thermodynamic (infinite volume) limit, for two different choices of number of sites in the compact time direction, hence taking the first steps towards the continuum limit extrapolation. We demonstrate the persistence of non-perturbative phenomena associated to the first-order phase transition: coexistence of states, metastability, latent heat, surface tension. We find consistency between several different strategies for the extraction of the volume-dependent critical coupling, hence assessing the size of systematic effects. We also determine the minimum choice of ratio between spatial and time extent of the lattice that allows to identify the contribution of the surface tension to the free energy. We observe that this ratio scales non-trivially with the time extent of the lattice, and comment on the implications for future high-precision numerical studies.

Divergence in perturbative expansions is where interesting physics takes place. Particle production on time-dependent backgrounds, as one such example, is interpreted as transition from one vacuum to another. Vacuum is typically defined as an asymptotic state in which the WKB approximation is valid. The use of the WKB method, however, poses several conceptual and computational issues, as the WKB series is divergent in general, quantization is insensitive to higher orders in the series, and the global behavior of solutions cannot be captured. Exact WKB analysis is a powerful resummation technology that provides an analytical tool for a global structure of exact solutions to overcome these problems. In this paper, we establish quantization by fully employing the exact WKB solutions as mode functions and by defining the vacua with respect to them. We provide a self-contained exact WKB formulation to obtain evolution matrices without resorting to the use of known special functions and without approximations. We find that the quantity called Voros coefficient plays an important role to re-normalize the exact WKB solutions compatible with asymptotic states. We show that the ambiguity that coexists with nontrivial Voros coefficients is eliminated by requiring physical quantization conditions. Our formalism provides a conceptual as well as practical framework to upgrade our treatment of quantization and particle production. Combined with other approximating techniques, it can form a basis to tackle a broad class of problems that are beyond technical ability of the existing formulations.

Although originally developed primarily for artificial intelligence workloads, RISC-V-based accelerators are also emerging as attractive platforms for high-performance scientific computing. In this work, we present our approach to accelerating an astrophysical $N$-body code on the RISC-V-based Wormhole n300 card developed by Tenstorrent. Our results show that this platform can be highly competitive for astrophysical simulations employing this class of algorithms, delivering more than a $2 \times$ speedup and approximately $2 \times$ energy savings compared to a highly optimized CPU implementation of the same code.