Papers for Monday, May 11 2026

Fast radio bursts (FRBs) which are well localised ($<$1") to their host galaxy are tools for studying cosmology and the intergalactic medium. Furthermore, high-time resolution datasets of their polarisation properties can enable testing of the numerous models on their potential progenitors. To that end, the CELEBI (CRAFT Effortless Localisation and Enhanced Burst Inspection) pipeline was conceived to enable data reduction from raw antenna voltages to detect fast radio transient events, localise them to sub-arcsecond precision, and produce polarimetric data at time resolutions as fine as 3 ns. Here we present a slew of updates to the CELEBI pipeline. Improvements to the astrometry correction for FRB localisations has aided our ability to determine what part of a galaxy more nearby FRBs have occurred in, which can have its own implication on the progenitor. We also have implemented time and frequency gating on detected fast transients to enable a boost to signal-to-noise, particularly useful for high dispersion measure or faint fast radio transients. We give examples of our improvements to the localisation, including for the currently 'hostless' FRB 20251019A. The polarisation calibration process has been overhauled, resulting in much more accurate measurements of derived polarisation fraction and rotation measures. Furthermore, we now have incorporated tools for structure-maximisation of the dispersion measure of fast radio transients, a software container which enables the installation of CELEBI on other machines, and improved the pipeline efficiency. Together these updates (named 'Polarisation and astrometry Improvements for New Knowledge', or PINK) greatly improve our ability to keep up with the expected detection rate from the CRAFT COherent (CRACO) upgrade to the real-time fast transient detection system of the Australian SKA Pathfinder.

Cosmic rays (CRs) are important drivers for molecular chemistry in star-forming regions, and laboratory experiments have shown that CRs can stimulate the release of complex organic molecules (COMs) such as methanol. Observationally, this has primarily been tested in cold, low-mass cores, so studying how CRs affect COM formation in a high-mass star-forming environment is of great interest. We performed a high-sensitivity wide-band spectral line survey with the Onsala 20 m telescope towards the high-mass protostar Cepheus A HW2, which is known to host an ionised jet. Consistent with previous studies, two primary velocity components ($-11$ km s$^{-1}$ and $-5$ km s$^{-1}$) were identified. Column densities and relative abundances of the detected ions and COMs were estimated from rotational diagrams, single transitions and RADEX grid searches (CH$_3$OH: $1.6\times10^{-9}$, CH$_3$CN: $5.9\times10^{-11}$, t-HCOOH: $7.9\times10^{-11}$, H$_2$CCO: $1.7\times10^{-11}$, CH$_3$CHO: $1.9\times10^{-11}$, CH$_3$OCHO: $7.6\times10^{-10}$ at $-11$ km s$^{-1}$). Deuterium fractions were also estimated (in range $0.002-0.3$ at $-11$ km s$^{-1}$), and the volume density of molecular hydrogen ($2.6\times10^5$ cm$^{-3}$ at $-11$ km s$^{-1}$) was constrained from the RADEX grid searches. Electron fractions and CR ionisation rates (CRIR, $6.8\times10^{-17}$ s$^{-1}$ at $-11$ km s$^{-1}$, $\leq9.2\times10^{-19}$ s$^{-1}$ at $-5$ km s$^{-1}$) were estimated through analytic chemistry using different ions as probes. The gas-grain chemical code Nautilus reproduced the observed abundances of CH$_3$OH, CH$_3$CN, HCO$^+$, N$_2$H$^+$ at the observed density, temperature and CRIR within the uncertainty of the model. The results indicate that the CR ionisation rate of the kinematic component associated with most of the COMs' emission in the region is locally enhanced.

Optical emission-line ratios in star-forming galaxies at $z \sim 3$-8, such as [OIII]/H$\beta$ and [OIII]/[OII], are strongly offset from those at $z \sim 0$-2, pointing to more extreme ionization and ISM conditions in the early Universe. To constrain the physical origin of these offsets, we developed Lumen, a framework for modelling nebular emission from spatially distributed HII regions in cosmological simulations. We apply Lumen to IllustrisTNG50, validate its predictions at low redshift, and test a suite of proposed mechanisms for producing extreme line ratios at $z = 3$-8. We focus on the [NII]/H$\alpha$ versus [OIII]/H$\beta$ (N2-BPT) diagram, the [SII]/H$\alpha$ versus [OIII]/H$\beta$ (S2-VO87) diagram, and the [OIII]/[OII] versus ([OII]+[OIII])/H$\beta$ (O32-R23) diagram. We find that $\alpha$-enhancement alone cannot explain the bulk of observations. Moderate offsets emerge from the combined effects of $\alpha$-enhancement, a higher IMF upper-mass cutoff, and AGN contributions. The most extreme [OIII]/H$\beta$ and [OIII]/[OII] values require high ionization parameters powered by massive star clusters of $\gtrsim 10^5$-$10^6\,\mathrm{M}_\odot$, consistent with recent JWST observations. Reproducing the highest [NII]/H$\alpha$ ratios additionally requires enhanced nitrogen abundances. Although gas densities of $n \sim 10^4\,\mathrm{cm}^{-3}$ can boost several diagnostic ratios, they suppress [SII]/H$\alpha$ and are therefore in tension with current observations. Overall, models combining harder ionizing spectra, elevated ionization parameters from massive star clusters, and enhanced nitrogen abundances reproduce the observed high-$z$ galaxy population across the N2-BPT, S2-VO87, and O32-R23 diagrams. This successful model also motivates new demarcation lines for star-forming galaxies in the N2-BPT and S2-VO87 diagrams.

The competition between metal synthesis and feedback from massive stars establishes the mass-metallicity relation (MZR) at low-redshifts. Examining this relation at higher redshifts, particularly at the low-mass end $\lesssim10^{8}\,{\rm M_\odot}$, is essential for understanding chemical enrichment and stellar feedback. In this study, we utilize the deep ($\sim30\,$hrs) JWST/NIRSpec G395M GLIMPSE-D survey of the lensed field Abell S1063, to explore the low-mass end of the MZR at high redshift ($z\sim6-8$). We identify eight [OIII]$\lambda$4364 emitters, enabling the most reliable "direct" metallicity measurements in galaxies down to stellar masses of $\sim10^{6-8}\,{\rm M_\odot}$. By combining our sample and galaxies with [OIII]$\lambda$4364 detections from the literature, we calculate direct metallicities for 21 galaxies. We compare our direct metallicities to those derived from strong-line diagnostics, and find them to be consistent with previous calibrations. We fit the MZR at $10^{6.7-9}\,M_{\odot}$ with $\sim0.3-0.5$ dex lower metallicity than local galaxies at similar stellar mass. We find the slope to be $0.25\pm0.10$, comparable to the local MZR; and the MZR exhibits a scatter of $\sim0.2\,$dex, which is larger than the local MZR, The lower metallicities may reflect denser, more gas-rich early environments, with continuous inflow of metal-poor gas diluting the ISM metallicity. In addition, we show that in extremely high electron densities ($n_e \gtrsim 10^5\,{\rm cm^{-3}}$), metallicities can be significantly underestimated ($\sim0.5$ dex), if lower $n_e$ are assumed for galaxies with high $n_e$. In a nutshell, these observations provide the first glimpse of the low-mass MZR at $z\sim6-8$ using direct metallicity measurements. More deep spectroscopic observations in lensed fields will be critical to robustly characterize the MZR and chemical evolution in the early universe.

We present an HST imaging survey of a 1.1 sq. degree sky area toward the Milky Way Galactic Bulge. This field significantly overlaps with the upcoming Nancy Grace Roman Galactic Bulge Time Domain Survey (GBTDS). High angular resolution imaging of this area with HST before the start of the Roman Galactic Exoplanet Survey (RGES) will greatly strengthen Roman's ability to characterize detected exoplanet systems, as well as provide a rich and wide-field archive for use as a legacy dataset toward the Galactic Bulge for the broader community. We conduct coordinated-parallel imaging with both wide-field cameras on HST, Wide-field Camera 3 (WFC3) and Advanced Camera for Surveys (ACS), utilizing the F606W and F814W passbands. Approximately 70% of the survey was conducted during HST Cycle 32, with the remaining 30% conducted during Cycle 33. In this paper, the first in a series, we give a general overview of the program and the observing strategy, and present early results. This campaign secures HST's lasting impact on the high-precision study of stellar populations, dynamics, exoplanet systems, interstellar extinction, metallicities, cluster associations, and more toward the center of our Galaxy.

A central question in galactic dynamics and galactic archeology is: how much do the orbits of stars redistribute (migrate) after birth? We use the FIRE-2 cosmological zoom-in simulations of 11 Milky Way-mass galaxies to quantify the change in the orbital specific angular momentum, j_phi, orbital radius, R_orbit, and azimuthal velocity, v_phi, of stars from birth to today. We examine the dependences on stellar age, present-day R_orbit, and birth R_orbit, characterizing both the median (net) change, Delta R_orbit, and its scatter, sigma(Delta R_orbit). We comprehensively compare five ways of measuring orbital radius; we find generally consistent trends, but only when measuring radius today and radial redistribution self-consistently. Stars selected by their birth R_orbit typically decreased in R_orbit, j_phi, and v_phi since birth. The trend for stars at a given R_orbit today depends on age: those younger than ~5 Gyr generally decreased in R_orbit, j_phi, and v_phi since birth, while those older generally increased in R_orbit, j_phi, and v_phi since birth. sigma(Delta R_orbit), a standard metric of radial redistribution, increases with stellar age only up to ~ 3 Gyr; it saturates at sigma(Delta R_orbit) ~2 kpc for older stars. This saturation contradicts a common expectation of a monotonic increase with age. Our results broadly agree with recent observational inferences of Delta R_orbit and sigma(Delta R_orbit) in the Milky Way. Across our FIRE-2 sample, the timing of disk formation does not correlate with sigma(Delta R_orbit), but it correlates with (net) Delta R_orbit.

JWST has enabled the detection of galaxies in the earliest stages of cosmic history. We compare the ultraviolet luminosity functions (UVLFs) at redshifts $z=7-15$ predicted by the new cosmological hydrodynamics simulations, COLIBRE with observations, including those from JWST. The UV luminosities of COLIBRE galaxies are derived using the radiative transfer code SKIRT, which tracks stellar emission and its processing through the multi-phase interstellar medium and dust distribution predicted by COLIBRE. We find that although COLIBRE is consistent with the observed evolution of the stellar mass function up to $z=12$, its dust-attenuated UVLFs fall systematically below the observations at the bright end: at the number density of $10^{-6}\,\mathrm{Mpc^{-3}\,mag^{-1}}$, the brightest galaxies are underluminous by $\approx 1\,\rm mag$ at $z=7$, increasing to $\approx 2.5\,\rm mag$ at $z=15$. Accounting for observational uncertainties brings the COLIBRE UVLFs closer to the observational data, but does not fully resolve the discrepancy. Ignoring dust attenuation allows COLIBRE to produce sufficiently bright galaxies at $7\lesssim z \lesssim 12$, while at $z=15$, COLIBRE still underpredicts the luminosities of the brightest galaxies, indicating the need for additional physical mechanisms to boost the UV luminosities at the earliest cosmic epochs, such as a ''top-heavy'' stellar initial mass function. We fit the COLIBRE UVLFs with Schechter functions and calculate the evolution of the best-fit parameters. We find that the galaxy number density decreases, the characteristic luminosity becomes fainter and the faint-end slope becomes steeper towards higher redshifts. The UV luminosity density decreases by a factor of $\approx 300$ from $z = 7$ to $z = 15$.

Gravitational wave sources act as absolute distance indicators, making them powerful probes of the present-day expansion rate of the Universe, $H_0$. The cross-correlation method combines gravitational wave events with galaxy catalogues to constrain cosmological parameters through their shared large-scale structure. In this work, we investigate how key methodological choices -- including covariance treatment, bias parametrisation for galaxies and gravitational wave events, and distance and redshift binning width -- affect the inferred value of $H_0$. We also study catalogue incompleteness, showing that selection effects can be incorporated directly into the theoretical prediction, without the need to model the missing population explicitly, a key advantage over the standard galaxy catalogue approach. Our results indicate that, with appropriate modelling choices and a sufficiently large sample of precise gravitational wave events, the systematic biases considered here can be effectively mitigated, highlighting the potential of the cross-correlation method for future dark siren precision cosmology.

The cosmological redshift of a galaxy's light is inferable from its observable properties in images. Because imaging is much easier to acquire than spectroscopic observations that would allow the identification of distinct line features, this motivates the technique of photometric redshift estimation (photo-$z$). Photo-$z$ has been an early and sustained driver for the utilization of artificial intelligence (AI) in astrophysics, and conversely AI methods are underlying most of the recent advances in photo-$z$. Here we review the diversity of AI methods applied to the photo-$z$ problem over the years in a discriminative way, that is, to regress redshift from photometric observables. We argue that, besides optimization suiting specific applications, this approach has effectively converged. It is limited not by the AI methodology but by the size and substantial systematic uncertainties and selection effects in spectroscopic training samples. In order to progress, either an unobtainable quantity and quality of training data or a more principled approach in using it is required. We thus outline ongoing research of integrating AI in a Bayesian modeling of galaxy data. This comes in the form of generative models for representing the distribution of intrinsic properties and outcomes of telescope observations of the galaxy population.

Heavily reddened quasars (HRQs) are luminous, dust-obscured broad-line quasars thought to represent a short-lived phase of intense black hole growth and feedback. Previous studies have been limited by small sample sizes, restricting robust statistical analysis. We expand the sample of the most luminous HRQs to enable population-level studies, connecting their spectral energy distributions (SEDs) to other quasar populations and placing them within an evolutionary sequence of massive galaxy and black hole formation. We assemble multiwavelength broadband photometry for the brightest HRQ candidates (K$_{AB}$ < 18 mag) and select AGN with red near-infrared colours (J-K)$_{AB}$ > 1.6. Using SPHEREx spectrophotometry, we confirm HRQs and determine redshifts. Detailed SED fitting allows comparison with other luminous quasars, including a control sample of hyper-luminous, unobscured Quaia quasars and luminous Hot Dust-Obscured Galaxies (Hot DOGs). We confirm 77 new HRQs with redshifts 1.5 < z < 3.9, dust-corrected optical continuum luminosities log$_{10}(\lambda L_\lambda (3000A)$ [erg/s])>47.0, and line-of-sight extinctions 0.4 < E(B-V) < 1.6 (A$_V$ mag). This more than doubles the known HRQs at z > 1.5, including the first seven at z > 3. A UV excess consistent with scattered quasar emission is detected in 76% of HRQs. We show that HRQs are hot-dust poor compared to blue quasars of similar luminosity and redshift. Their 6um continuum luminosities are systematically fainter at fixed 3000A continuum luminosity relative to blue Quaia quasars, indicating deficiency in both hot and warm dust. These results support a scenario in which HRQs represent a blow-out phase, where strong feedback begins clearing obscuring material from central regions.

X-ray spectral modeling is a powerful tool for studying the immediate environment of accreting objects, including supermassive black holes. Several models, either phenomenological or physically driven, have been developed over the past decade to study X-ray spectra, delivering important insights into the properties of circumnuclear material of active galactic nuclei (AGN). Despite the fact that these models are able to reproduce the data well, they often lack realistic geometries, and most of them consist of simplified configurations such as a slab or a torus. We use the ray-tracing code \textsc{RefleX} to generate new spectral models that cover a wide energy range in the X-ray band, adopting a realistic configuration for the surrounding material. We introduce two new table models that are publicly available: 1) the RXToPo model, which features an X-ray source along with a dusty torus and a polar hollow cone; 2) the RXagn1 model, which includes, besides the torus and polar cone, also the accretion disk and the broad line region. Both models were applied to the X-ray spectrum of NGC 424, demonstrating their potential to study sources whose X-ray emission is dominated by reprocessed radiation.

Astrophysical variabilities of Type Ia supernovae (SNe Ia), such as their link with their birth environment, are now one of the leading sources of systematic uncertainties on the measurement of the dark energy equation-of-state parameter $w$. Population studies of SNe Ia, using large samples, give precious insights into these variabilities. We analyse a volume-limited subsample of the ZTF SN Ia DR2 with BayeSN, a hierarchical Bayesian model for SN Ia SEDs. We investigate the distributions of SN Ia light curve parameters and their link with SN environment. Using a new training of BayeSN released in a companion paper, we find a smaller scatter of Hubble residuals compared to SALT. We then investigate the magnitude step, which accounts for the correlation between SN Ia standardised absolute magnitude and host environments. We find a posteriori steps of $0.103\pm0.010$ mag (a $10.1\sigma$ difference from 0) when using global stellar mass as an environmental proxy, and $0.086\pm0.010$ mag ($8.3\sigma$) when using local colour, in accordance with steps computed using SALT light curve fits. This confirms that the large step seen in the ZTF SN Ia DR2 data was not due to the SALT fit or the associated standardisation process. We then investigate the origin of the step, using a BayeSN model which accounts for both an intrinsic magnitude step and differing dust properties with the SN environment. We find a $0.103\pm0.018$ mag ($5.6\sigma$) step in global mass and a $0.085\pm0.019$ mag ($4.5\sigma$) step in local colour. The means of the $R_V$ distribution are similar between different host environments, with $\Delta\mathbb{E}(R_V)\leq0.2$ across all environment proxies, with significances ranging from $0.6\sigma$ to $1.2\sigma$. This is a strong signal of the existence of an intrinsic dependence of SN Ia absolute magnitude on environment.

We present VLA C-band (5~cm) continuum, K-band (1.3~cm) continuum, and water maser (22.235 GHz) monitoring of the protostar HOPS-373. We additionally present the contemporaneous monitoring for 95 sources within the 5~cm field of view for over two years during the peak of the HOPS-373 outburst and an additional epoch in 2026. HOPS-373 is a binary Class 0 protostar located in the Orion star forming region that was found to have a $\sim$4$\times$ luminosity burst from the JCMT Transient Survey and NEOWISE monitoring. We do not find evidence for a change in the free-free emission traced by VLA 5~cm continuum during the peak of its outburst or during the decline. Moreover, the 1.3~cm continuum does not show significant variability between the NE and SW components of the HOPS-373 binary. The water maser emission is highly variable toward HOPS-373, multiple velocity components are detected at different (or the same) times and the maser spots are located close to the 1.3~cm continuum source of HOPS-373-SW. There is tentative evidence for the water maser spots to be propagating away from the source, but there is not a robust connection between the outburst and the observed maser activity. The lack of correlation between outburst and free-free emission from HOPS-373 indicates that the free-free emission may not directly respond to increases in the accretion rate and subsequently the outflow rate. The lack of a link could be due to the outflow mostly being neutral, or there may be offsets in the timescale for the free-free response.

The common envelope (CE) phase plays a key role in the formation of binary compact object systems. Its final outcome strongly depends on the envelope binding energy, but this quantity is often estimated using fitting formulas that are not fully consistent with the underlying stellar evolution models adopted in population-synthesis codes. Here, we investigate envelope binding energies across the most extensive stellar grid considered to date. Our stellar tracks, evolved with PARSEC v2.0, include hydrogen (H) -rich stars with metallicities ranging from $Z = 10^{-11}$ (Population III stars) to $Z = 0.03$, and initial masses between 2 and 2000 M$_\odot$, as well as pure-helium stars with masses from 0.36 to 350 M$_\odot$. We examine the sensitivity of the envelope binding energies to the selected core-envelope boundary definition and to different internal energy source contributions. For H-rich stars, we find that internal energy sources can alter the envelope binding energy by more than an order of magnitude, whereas the core boundary criteria play a secondary role. In contrast, for pure helium stars, the core-boundary criterion becomes the dominant factor. The envelope binding energies derived from different stellar tracks can show deviations of several orders of magnitude, with larger differences for more massive stars and higher this http URL, by implementing our new envelope binding energy prescriptions into the binary population synthesis code SEVN, we show that the predicted merger rate densities of compact binaries can differ by more than an order of magnitude compared to previous models. Our results highlight the importance of using envelope binding energies that are consistent with the underlying stellar evolution models and caution against extrapolating empirical fits beyond the considered parameter space.

The Hubble Advanced Spectral Products (HASP) program is designed to robustly coadd Cosmic Origins Spectrograph (COS) and Space Telescope Imaging Spectrograph (STIS) spectra within the Mikulski Archive for Space Telescopes (MAST) in an automated fashion such that coadds are available for new data or archival data with updated calibrations. For each target within a visit or program, HASP employs a meticulous multi-stage filtering process to ensure data quality and creates coadded products for all central wavelengths (CENWAVEs) within specific gratings, as well as combined products using different gratings and instruments. The project also emphasizes making the code accessible to the user community for custom coaddition. As calibrations improve and new data are added to the archive, HASP products are re-created automatically so that they represent the best reduction of a given visit or program. Automated coadditions like those achieved by HASP can significantly enhance the combination of different CENWAVES, increase signal-to-noise ratios, and increase wavelength coverage. These properties make HASP a vital resource for astronomers using archival spectroscopic data from HST.

Asteroid reflectance spectra provide key constraints on surface composition. Gaia DR3 enables the study of 60,518 asteroids through NUV to visible reflectance spectra. We aim to classify asteroids using Gaia DR3 spectra and provide a homogeneous framework. Owing to systematics affecting Gaia DR3 data, direct comparison with previous taxonomies has to be taken with caution; thus, we developed a classification scheme tailored to Gaia and linked the resulting taxa to established classes. We selected the highest-quality spectra using Gaia DR3 quality flags and applied uncertainty thresholds to mitigate spectral artifacts, retaining over one-third of the original sample at the least noisy wavelength. To improve compositional discrimination, we included albedo, reducing the final sample to about one-fourth of its initial size. We then iteratively applied dimensionality reduction and clustering to identify the spectral taxa. We classified 14,042 asteroids into 13 taxonomic classes: A, B, C, D, E, F, G, K, L, M, P, S, and V, representing an increase of three compared to the number of objects classified in previous spectral classifications. The largest relative increase is found for the K class. The inclusion of NUV wavelengths allows the separation of B and F types within the C-complex and facilitates the identification of G types. The dynamical distribution follows expected trends, with Stypes dominating the inner and middle Main Belt, C-complex asteroids prevalent in the outer Main Belt, and D types beyond. We present a taxonomical classification of 14,042 asteroids based on Gaia DR3 reflectance spectra. NUV coverage is critical for disentangling primitive classes within the C-complex. Although artifacts in Gaia DR3 require caution when comparing median spectra with other datasets, this classification provides a robust reference for future Gaia releases, with larger observed samples.

We present the results of our investigations of spectrally and spatially resolved (sub)millimeter HCN-to-HCO$^{+}$ flux ratios at J=2-1, J=3-2, and/or J=4-3 in 18 nearby ($z <$ 0.15) ultraluminous infrared galaxies (ULIRGs), using ALMA $\lesssim$0.2" ($\lesssim$500 pc) resolution data. The geometry of elevated HCN-to-HCO$^{+}$ flux ratios (with $>$3$\sigma$ detections for both molecular lines) in position-position-velocity (PPV) space is visually classified into (i) spherical shell (spectrally and spatially distinct), (ii) spectrally distinct and spatially compact, and (iii) filled (spectrally filled and spatially compact). These can naturally be explained by the elevation of the flux ratio due to (i) a spatially resolved outflow, (ii) an AGN and/or a spatially unresolved outflow with blueshifted and redshifted emission components, and (iii) an AGN and/or a spatially confined outflow with not clearly separated blueshifted and redshifted velocity components, respectively. Signatures of elevated HCN-to-HCO$^{+}$ flux ratios originated from (a) spatially resolved outflow and (b) AGN and/or spatially unresolved outflow are seen in seven and nine ULIRGs, respectively. In the former spatially resolved outflow-origin case, modest-velocity components relative to the maximum outflow velocity tend to be probed by spaxels with elevated HCN-to-HCO$^{+}$ flux ratios. The spectrally and spatially resolved HCN-to-HCO$^{+}$ flux ratios can provide additional information on the physical origin of the elevated flux ratios in nearby ULIRG nuclei, compared to previously conducted spatially integrated and/or velocity-integrated analyses.

We explore the origin of the rotation rates of massive stars. Contrary to their low-mass siblings, most massive stars do not have detectable magnetic fields, so that star-disk interaction models used for the formation of rotating low-mass stars do not apply. We investigate whether the magnetic fields of protostellar jets present in the parent molecular cloud prevent the protostar from reaching the critical angular velocity. Starting from the gravitational collapse of a molecular cloud, we run two two-dimensional radiation-gravito-magnetohydroynamical simulations to study the formation of an accretion disk and the launching of magnetically-driven protostellar outflows (of particular interest is the formation of a magnetocentrifugal jet originating from the protostar and inner disk). We then study the angular momentum transfer from the disk and jet onto the protostar. Finally, we compute one-dimensional stellar evolution models of the pre-main sequence including our results from the disk-jet simulations and follow the angular momentum redistribution within the structure of the protostar. We find that the angular momentum transported outwards by the magnetically-driven protostellar outflows is sufficient for keeping the protostar below the critical speed at all times. Moreover, we are able to link the strength of the jet, and thus the rotation rate at the end of the accretion epoch, to the initial conditions for star formation. Our results show that the jet strength produces a variety of stellar rotation rates, suggesting that protostellar jets fix the rotation rate of massive stars.

We present the analysis of high-resolution synthetic dust polarization maps derived from large-scale simulations of magnetized multiphase interstellar turbulence carried out with the AthenaK code on the $Frontier$ exascale supercomputer at the Oak Ridge National Laboratory. Our turbulence model accurately captures spectral properties of the $E$- and $B$-modes measured by $Planck$ at 353 GHz. The simulations provide new insights into the physical origins of the observed $E/B$ asymmetry and positive $TE$ signal, facilitating the development of advanced models of Galactic foreground emission for current and future CMB experiments.

The settling of dust particles plays a critical role in the growth and dynamics of dust grains. We performed a detailed modeling of the ALMA continuum substructures for six highly inclined protoplanetary discs using radiative transfer simulations, to constrain the vertical height of millimetre dust grains and the settling strength. Our modeling results are a very thin millimetre dust disc in T Cha ($\text{h}_{\text{dust}}<$ 0.1 au throughout the disc), a vertically extended dust disc in DoAr 25 ($\text{h}_{\text{dust}}$ of $\sim$ 4.7 au at 140 au) and tentatively a thin disc in MY Lup ($\text{h}_{\text{dust}}<$ 0.5 au at 70 au). From lower resolution observations we found a very thin disc for PDS 111 ($\text{h}_{\text{dust}}<$ 0.1 au throughout the disc) and a more vertically extended millimetre dust disc in V409 Tau ($\text{h}_{\text{dust}}$ of $\sim$ 1.3 au at 35 au). We could not measure the vertical height in the asymmetric disc of RY Lup. We also found that the input dust opacities are a source of degeneracy in our models. Our tentative results, assuming the Ricci dust opacities, point to a diverse settling strength in our sample and possible radial variations. We also compared the models that best fit the ALMA data with the SPHERE data to test if they can reproduce the vertical distribution of small dust grains. This comparison suggests that models that reproduce the dust density distribution in the midplane cannot reproduce the distribution of small dust grains in the upper layers, reinforcing the need for more complex models.

We present You Only Stack Once (YOSO), an automated pipeline designed to detect faint, slow-moving Solar System objects in wide-field astronomical surveys. The pipeline integrates a novel Gaussian Motion Filter (GMoF) that operates at the pixel level to enhance signal-to-noise for objects exhibiting a range of apparent rates of motion. Unlike conventional shift-and-stack methods, which rely on discrete velocity trials, GMoF amplifies trails while suppressing random noise and static background features. Applied to a subset of DEEP observations from the Dark Energy Camera, YOSO recovered 45 out of 73 previously detected objects, as well as 11 new TNOs. It also discovered 216 objects in the near Solar System. Although alternative shift-and-stack methods are sensitive to objects about 0.88 magnitudes fainter, YOSO's false positive rate is extremely low, since it detects only sources that exhibit a trail and are consistent with a point source when shifted at the right rate. We show how this method can be deployed on large surveys like LSST, and adapted for other domains that require motion-based signal enhancement, including exoplanet imaging through Angular Differential Imaging (ADI), and near-Earth object (NEO) detection for missions like NEO Surveyor. YOSO thus provides a versatile, scalable approach for extracting faint, motion-dependent signals in the era of data-intensive astronomy.

V1674 Her (Nova Her 2021) is the fastest classical nova ever recorded, with an optical decline time of $t_2 \sim 1$ day, typically interpreted as evidence for a white dwarf mass close to the Chandrasekhar limit. We present a broadband X-ray study of V1674 Her combining contemporaneous XMM-Newton and NuSTAR observations in quiescence to directly constrain the white dwarf mass and magnetic field strength. The hard X-ray emission is modeled using a physically motivated post-shock accretion column model that accounts for the temperature gradient in the flow and reflection from the white dwarf surface. Under the assumption that the accretion disk is truncated at the co-rotation radius, we obtain a white dwarf mass of $M = 1.09^{+0.07}_{-0.06}\,M_\odot$. An independent constraint derived from timing analysis of the X-ray power spectrum yields a consistent value of $M = 1.12 \pm 0.06\,M_\odot$. These values are significantly lower than those inferred from empirical decline-time relations, suggesting that such relations may overestimate white dwarf masses in extreme fast novae. From the inferred accretion rate and magnetospheric radius, we estimate a surface magnetic field strength of $B = 21.3^{+6.6}_{-5.7}\,(\mathrm{stat})^{+12.9}_{-8.1}\,(\mathrm{sys})\,\mathrm{MG}$, placing V1674 Her at the high end of the magnetic field distribution for intermediate polars. Our results demonstrate that even the fastest novae do not necessarily host near-Chandrasekhar white dwarfs, highlighting the importance of direct X-ray constraints and suggesting that additional parameters beyond white dwarf mass play a key role in setting nova timescales.

We present a novel methodology for mapping dust extinction in nearby galaxies at parsec-scale resolution. We apply it to HST 68 fields within the Small and Large Magellanic Clouds (23 fields in the SMC and 45 fields in the LMC) using multi-band HST photometry from the Scylla and METAL surveys. Our technique leverages \textit{kriging}, a geostatistical interpolation method built on the principles of Gaussian Process regression, combined with Gaussian mixture modeling to statistically isolate background stellar sources and account for line-of-sight depth effects. 3D dust simulations demonstrate the method's capability to recover column densities to an accuracy of $A_V \approx 0.1$ mag in fields with at least 1000 sources. The resulting $4^{\prime\prime}$ resolution ($\sim1$-pc) dust maps reveal detailed structure and strong spatial correlation with ancillary ISM tracers, especially in star-forming regions like 30 Doradus. Global extinction of total column densities follows log-normal profiles in both galaxies, with the SMC exhibiting slightly higher mean extinction ($e^{\mu}=0.47$ mag) than the broader LMC ($e^{\mu}=0.43$ mag), likely due to significant line-of-sight depths. We find systematic offsets between dust mass surface densities ($\Sigma_{D}$) derived from extinction versus FIR emission in both galaxies, with $\Sigma_{D, FIR}/\Sigma_{D, A_V}$ ratios ranging from $0.6-1.8$. This work provides the highest-resolution dust extinction maps in SMC and LMC to date, which offer a vital independent benchmark for constraining dust emissivity, $\text{CO}$-dark gas fractions, and the multi-scale structure of the ISM in low-metallicity environments.

This paper presents a version of the HEXTOR energy balance model that has been configured for the study of habitable terrestrial planets orbiting low-mass stars. The model is validated for rapidly-rotating Earth-like planets using latitudinal coordinates, which shows expected patterns of bistability. A tidally-locked coordinate transformation is then applied to the model, which is calibrated to match mean values of the minimum, average, and maximum surface temperatures from a general circulation model ensemble of TRAPPIST-1 e. This calibrated energy balance model is used to characterize the possible climate states of such a synchronously rotating planet across a parameter space of instellation and carbon dioxide partial pressure. These calculations suggest a state of partial ice cover for TRAPPIST-1 e and complete ice cover for TRAPPIST-1 f, unless carbon dioxide partial pressure is ~1 bar or greater. This approach demonstrates the capability of a simplified one-dimensional model to study the climates of terrestrial planets in synchronous rotation, which can help guide more complex models and observations toward the most promising targets of interest.

We present a comprehensive analysis of extended H$_2$ emission from 34 protoplanetary disks observed with the JWST Disk Infrared Spectroscopic Chemistry Survey (JDISCS), supplemented by archival data. We investigated the morphology, kinematics, excitation conditions, and mass dynamics of H$_2$. Extended emission from pure rotational H$_2$ lines is found to be common, with 16 sources exhibiting clear signatures of disk winds. These include monopolar and bipolar structures in inclined disks and ring-like or bubble-like morphologies in face-on systems features indicative of wide-angle disk winds. Our analysis shows that the H$_2$ is consistent with slow {(4.2$^{+6.7}_{-3.0}$ km s$^{-1}$)} MHD driven winds. For ten disks, we model the wind morphology and find a median half-opening angle of $45\arcdeg^{+5}_{-4}$ and a characteristic power-law index of $\alpha \sim$ 1.6. Excitation analysis yields a median gas temperature of 624 $\pm$ 130 K and a column density of $\log(N_{\mathrm{tot}}\,[\mathrm{cm}^{-2}]) = 18.6 \pm 0.6$. The median wind mass-loss rate, ${\rm log_{10}}(\dot{\rm M}_{\rm wind}^{\rm tot}) = -9_{-0.4}^{+0.8}\,{\rm M_\odot\,yr^{-1}}$, implies that, if molecular winds are the dominant mechanism responsible for disk dispersal, a typical disk with a mass of $2-3\,M_{\rm Jup}$ would dissipate on a $\sim$2-3 Myr timescale, consistent with observed disk lifetimes. The $\dot{\rm M}_{\mathrm{\rm wind}}^{\rm tot}$ span a relatively narrow range ($\sim$2 dex) and do not correlate strongly with accretion rates onto the star, suggesting that the mass loss rate and the accretion rates are probing different timescales. Our findings demonstrate that spatially extended warm H$_2$ emission is a widespread and reliable tracer of molecular disk winds in protoplanetary systems.

Gravitational-wave observations have renewed interest in the black-hole mass gap and in the maximum mass of first-generation black holes below its lower edge. The \(^{12}{\rm C}(\alpha,\gamma)^{16}{\rm O}\) reaction plays a central role in this problem because it determines the carbon-to-oxygen ratio after core-helium burning and thereby affects the later evolution of massive stars toward pulsational pair instability and pair-instability supernovae. Recent attempts to constrain \(S(300~{\rm keV})\) from gravitational-wave population inferences face important limitations, because the lower edge of the black-hole mass gap is not directly measured. It is inferred model dependently from assumptions about stellar evolution, metallicity, mass loss, rotation, binary evolution, hierarchical mergers, selection effects, priors, and the adopted population model. Therefore, values of \(S(300~{\rm keV})\) inferred from black-hole populations must remain consistent with independent nuclear-physics constraints. In this work we reanalyze the low-energy \(^{12}{\rm C}(\alpha,\gamma)^{16}{\rm O}\) \(S\) factor using updated information on the subthreshold \(1^{-}\) and \(2^{+}\) ANCs and on the ground-state ANC of \(^{16}{\rm O}\), together with direct capture data. These constraints favor a lower \(S(300~{\rm keV})\) than the older central evaluation and disfavor very large values required by some black-hole-population interpretations. Using the resulting ANC-constrained \(S(300~{\rm keV})\) range and the transformed relation between this quantity and the lower edge of the pair-instability mass gap, we estimate \[ \frac{M_{\rm BH}}{M_\odot}\simeq 61\text{--}75 . \] Thus, the present nuclear-physics constraints favor a relatively high lower edge of the first-generation black-hole mass gap.

Glycine-the simplest amino acid-has remained undetected in the interstellar medium despite decades of sensitive searches, motivating alternative approaches to constrain its astrochemical origin. A promising strategy is to investigate the broader $\rm C_{2}H_{5}O_{2}N$ isomer family and identify detectable members that can serve as observational anchors for glycine-related chemistry. Herein, we report the first robust interstellar detection of methyl carbamate toward the hot molecular core G358.93-0.03 MM1 using ALMA 1 mm observations. Ten unblended rotational transitions are identified, yielding a column density of (4.21$\pm0.84)\times10^{15} \rm cm^{-2}$ and an excitation temperature of $204\pm10$ K. We also searched for other $\rm C_{2}H_{5}O_{2}N$ isomers with available rotational spectroscopic data, including glycine, but none were detected, allowing us to derive upper limits on their column densities. The resulting abundance pattern deviates significantly from the Minimum Energy Principle predictions, highlighting that the $\rm C_{2}H_{5}O_{2}N$ family is shaped primarily by kinetic chemical process rather than thermodynamic equilibrium. The observed methyl carbamate abundance is consistent with a grain-surface formation scenario involving radical-radical recombination ($\rm CH_{3}$O + $\rm NH_{2}$CO), further supported by its correlated abundances with its proposed precursors, methanol and formamide, across diverse astrophysical environments. This detection establishes methyl carbamate as a new observational anchor for glycine chemistry, providing critical constraints on the formation pathways of amino-acid-related molecules in star-forming regions.

Galaxy clusters contain a hot, diffuse, and weakly magnetized plasma known as the intracluster medium (ICM). In this environment, how thermal conduction influences plasma dynamics and the conditions under which it operates efficiently remain open questions in cluster physics. Systems in which active galactic nuclei (AGN) jets interact with cold fronts produced by cluster mergers provide a unique setting to examine the interplay between conduction, jet dynamics, and ordered magnetic fields. To interpret the detailed structures revealed by recent observations, it is therefore important, as a first theoretical step, to quantify how thermal conduction modifies AGN jet morphology and the surrounding magnetic-field configuration. We perform two-dimensional magnetohydrodynamic (MHD) simulations of an AGN jet in an ICM environment, incorporating anisotropic thermal conduction with varying efficiency. The simulations show that thermal conduction transports heat from the jet head backward along magnetic field lines into the inner cocoon. This process increases the inner cocoon pressure, enhancing jet collimation by a factor of $\sim 4$ compared to models without conduction. This stronger collimation stretches the magnetic fields along the cold-front surface, resulting in a maximum field strength up to a factor of $\sim 1.5$ larger. Jet collimation increases as the conduction efficiency increases, which is interpreted as a conductive collimation mechanism. These results suggest that anisotropic thermal conduction can operate effectively on jet scales in galaxy clusters, and that accounting for conduction may be important when interpreting jet morphology and magnetic field structure in merging cluster environments.

Magnetars are a subclass of neutron stars with ultra-strong surface magnetic fields. Some magnetars exhibit persistent hard X-ray emission, characterized by power-law tails with photon indices around 1--1.5, extending from ${\sim}$10 keV to several hundred keV. The leading explanation for this hard X-ray component is resonant Compton scattering, in which the thermal seed photons are upscattered by relativistic electron-positron pairs flowing along magnetic field lines in the magnetosphere. In this work, we adopt the pair outflow framework of the magnetar magnetosphere and calculate the resonant Compton scattering opacity, as well as the spectrum and polarization of the upscattered emission. We find that resonant cooling can substantially modify the magnetospheric plasma density and impose strong optical depth constraints on the hard X-ray emission regions. Under the viewing geometry inferred from IXPE, an equatorial twist near the stellar surface provides a viable configuration for the NuSTAR hard X-ray spectrum of 4U 0142+61, while a polar-twist geometry is disfavored. Joint spectral, timing, and polarimetric modeling will be essential for distinguishing between the magnetospheric scattering geometries and understanding the physical properties of the pair plasma.

To complete the analysis of the 2023 KMTNet subprime-field microlensing planetary events identified by its AlertFinder system, we present the analysis of six events, KMT-2023-BLG-(1810, 0084, 1118, 0584, 1697, 2218). We find that the first three events are securely confirmed as planetary, with inferred mass ratios of $\log q \sim -1.9$, $-2.0$, and $-2.6$, respectively. The remaining three events exhibit the well-known degeneracy between binary-lens/single-source (2L1S) and single-lens/binary-source (1L2S) models, and two of these also admit viable stellar binary solutions. A Bayesian analysis indicates that the companions in the confirmed planetary events are likely either super-Jupiters orbiting beyond the snow line of M- or K-dwarf hosts or, for two degenerate solutions of KMT-2023-BLG-1118, Saturn-mass planets orbiting late-type M dwarfs. To date, the 2023 KMTNet sample contains 25 unambiguous planetary events, and its mass-ratio distribution is consistent with that of the KMTNet planetary sample from 2016--2019.

We report a detailed analysis on the young stellar cluster Berkeley 59 using Fermi-LAT. Using up-to-date source catalog and background models, we found significant extended GeV emission around Berkeley 59, which can be modeled by a radial disk of 1.02 degree radius with a significance of the extension of 10.6 sigma. We investigated the molecular, neutral and ionized gas content and the hadronic origin. The gamma-ray spectrum of Berkeley 59 has a photon index of 2.88. The derived gas mass from H2 and HII around Berkeley 59 is about 289 solar mass. We derived the relationship between cosmic ray acceleration efficiency and diffusion coefficient. Our results suggest that the extended gamma-ray emission originates from cosmic rays accelerated by cluster winds interacting with surrounding gas.

We investigate the long-term dynamical evolution of Ter2, Ter4, and Ter5, focusing on their mutual interactions, mass-loss behaviour, and survivability in the dense Galactic centre environment. We performed a suite of high-resolution direct N-body simulations over 8 Gyr, modelling three individual clusters that we also modelled as combined systems. We compared reference runs of isolated clusters with simulations of the full three-cluster system to quantify possible differences in mass loss, potential energy, and orbital behaviour. Our simulations reveal multiple close encounters between the Terzan clusters. The most significant encounters occur between Ter2-Ter4 and Ter4-Ter5, with their tidal radii exceeding the minimum separation. A notable case is the pair Ter2-Ter4, which approaches within 10 pc at a relative velocity of ~320 km/s. We found that the mass-loss rate is higher for the low-mass Ter2 and Ter4 systems in the combined three-cluster simulations than in our similar isolated runs, highlighting the importance of mutual cluster interactions. The common run clearly demonstrates that mutual gravitational interactions between clusters drive significant triaxial deformations, especially for Ter2 and Ter5, which evolve from nearly spherical to distinctly prolate shapes. In contrast, the isolated runs show clusters that remained almost perfectly spherical, confirming that the observed shape changes are correlated with the mutual interactions. The survivability and dynamical evolution of Galactic centre globular clusters cannot be fully understood without accounting for collective interactions among all systems within a few kiloparsecs. Our results emphasise the necessity of complex multi-cluster modelling in realistic Galactic potentials to capture the long-term fate of surviving and dissolved clusters

The recent detection of the ultra-high energy neutrino KM3-230213A by KM3NeT/ARCA marks the first observation of an astrophysical neutrino with energy above 100 PeV, opening a new window to the ultra-high energy Universe. In this contribution, the current global ultra-high energy neutrino landscape in light of this event is reviewed, including tension of this observation with existing limits set by the IceCube and the Pierre Auger Observatories. Different scenarios are discussed to explain its origin. Recent efforts to constrain features of potential source populations using the inferred diffuse ultra-high energy neutrino flux are also presented.

We present high-resolution UVES+VLT observations of neutral nickel and iron atoms in the coma of the interstellar comet 3I/ATLAS taken after perihelion. Metal emission was strong shortly after perihelion and persisted at large heliocentric distances. At $r_h \sim 2$ au the total metal production rate was found to be at least an order of magnitude larger than that of typical solar-system comets. Post-perihelion production rates exhibit pronounced asymmetry compared to the pre-perihelion behavior: production rates are higher after perihelion and decline more gradually with $r_h$, the difference being stronger for FeI. The NiI/FeI abundance ratio, initially anomalously large before perihelion, evolved toward values comparable to solar-system comets near 2 au, and shows a weaker $r_h$ dependence after perihelion. To interpret these results, we revisited and extended the carbonyl hypothesis in which FeI and NiI are produced by the rapid photodissociation of Fe(CO)$_5$ and Ni(CO)$_4$ vaporized from the nucleus. Fits that include direct sublimation of carbonyls reproduce the observed rates and the high NiI/FeI line ratio, which is determined by the higher volatility of Ni(CO)$_4$. Desorption of carbonyls from sublimating CO$_2$ and H$_2$O ices is found to be negligible. The temperature profiles needed to reproduce the observations were found to be shallower than the equilibrium $T \propto r_h^{-1/2}$ relation, suggesting that the sublimation could occur below the surface of the nucleus. Fits using temperature profiles from thermal models require sublimation from depths of several cm, especially post-perihelion. An additional transient heat source ($T \simeq$ 100-140~K), possibly linked to the amorphous-crystalline ice transition, is proposed to explain the early NiI excess before perihelion.

Long-term \textit{Fermi}-LAT monitoring makes it possible to ask whether a blazar light curve shows signs of an upcoming flare before the flare becomes obvious in the $\gamma$-ray emission. We present a strictly causal machine-learning framework for forecasting $\gamma$-ray blazar flares from 3-d binned LAT light curves. Flare intervals are identified with Bayesian Blocks, and each light curve is sampled with 365-d trailing windows from which 42 variability features are measured. We train separate WATCH and TRIGGER models: WATCH predicts whether flare activity will appear within the next 90 d, while TRIGGER predicts whether a new flare onset will occur within the next 45 d. To avoid temporal leakage, all scaling, calibration, threshold selection, and validation use only the pre-cutoff data before MJD 60000. We apply the method to the FSRQ 4FGL\,J1048.4$+$7143, using 13 bright blazars as auxiliary training sources. Among logistic regression, polynomial logistic regression, and random forest classifiers, polynomial logistic regression gives the strongest held-out WATCH performance, with ROC AUC $=0.891$, average precision $=0.396$, and a block-permutation probability $p_{\rm perm}=0.006$. At the selected WATCH threshold, it recovers 18 of the 21 positive windows in the held-out WATCH set, corresponding to a recall of 0.86. The same model also gives the best held-out TRIGGER ranking, with TRIGGER AUC $=0.770$ and TRIGGER AP $=0.123$, although no reliable pre-onset TRIGGER alert is obtained. The WATCH state appears before both held-out flare episodes, with final alerts 4.5 and 2.5 d before onset. The corresponding broader WATCH-active periods begin 88.5 and 72.5 d before flare onset. These results suggest that long-term {\fermi} light curves contain useful predictive information about the build-up to blazar flares.

Fanaroff-Riley class I (FRI) radio galaxies show centre-brightened emission from disrupted lower power jets, while traditionally more luminous class II (FRIIs), are edge-brightened, with relativistic jets terminating in hotspots. Population studies of radio-loud AGN (RLAGN) with low frequency, deep, wide-field surveys have revealed FRII-like radio structures at lower luminosities. We present the first high-resolution morphological investigation of a representative LOFAR-selected sample of low-luminosity FRIIs, to determine whether this new population is physically distinct from traditional high-luminosity FRIIs. Using new $1.5$-GHz Jansky Very Large Array (VLA) observations for a sample of 19 low-luminosity FRIIs, from the LOFAR Two Metre Sky Survey Data Release 1 (LoTSS DR1), with luminosities up to three orders of magnitude lower than the typical FR break ($L_{150} = 10^{26}$ W Hz$^{-1}$). We examine the compact features and perform spectral index analysis to identify hotspots, cores and signatures of restarting or remnant activity. We find a higher prevalence of cores and a comparable number of hotspots in the low-luminosity FRII sample compared to a randomly-selected sample of luminous ($L_{150}>10^{26}$ W Hz$^{-1}$) FRIIs selected from the same parent LOFAR sample. Approximately 32 per cent of low-luminosity FRIIs show restarting or remnant behaviour, while $\sim 32$ per cent are active FRIIs with compact hotspots. Our results show that FRII source dynamics occur at low radio luminosities, but reinforce earlier conclusions that the population of low-luminosity edge-brightened RLAGN is highly diverse. Binary morphological classifications should be used cautiously as a first step towards more nuanced investigations of the complexity of jet life cycles and evolution.

Young massive star clusters (YMSCs) have been proposed as excellent candidates for the main sources of Galactic cosmic rays (CRs) up to the PeV range. The detection and study of gamma rays in the very-high-energy (E>100GeV) range has brought arguments in favour of this hypothesis. Current instruments have detected only a few YMSCs. Future observatories are expected to increase this number, providing a larger sample improving our ability to constrain the role of YMSCs in the origin of CRs. We study the population of TeV YMSCs detected and their properties, confronting simulations of the YMSC population to the observed sample, to address the fundamental questions concerning the spectrum of accelerated particles, the efficiency of CR production, and the fraction of the wind luminosity converted into turbulent magnetic fields. Using Monte Carlo methods, we simulate the Galactic population of YMSCs in the gamma-ray domain and confront our simulations to the catalogue of sources of the systematic survey of the Galactic plane performed by H.E.S.S. (HGPS) and the First LHAASO Catalogue of Gamma-Ray Sources. We systematically explore the parameter space of our model, including the slope of accelerated particles $\alpha$, the CR efficiency $\eta_{\rm CR}$, the fraction of the wind luminosity converted into turbulent magnetic field $\eta_{\rm b}$, and the diffusion regime. We found 5 possible sets of parameters for which >75% of realisations agree with the combined data from the HGPS and LHAASO 1st catalogue. Certain regions of the parameter space are strongly disfavoured, such as Bohm diffusion. Our model successfully reproduces the YMSC population observed in both catalogues. With future systematic surveys, e.g. the Cherenkov Telescope Array Observatory (CTAO), this approach will help break degeneracies and improve our understanding of particle acceleration at YMSC shocks in the Galaxy.

We present optical and near-infrared observations of the fast-declining Type Ia supernova (SN Ia) 2022an. The photometric and spectroscopic properties identify it as a standard 91bg-like event; however, our data reveal a relatively narrow absorption feature with a full width at half maximum (FWHM) of 75 angstroms near $1.037\,\mu$m in the rest frame of the observed spectra that persists from around 30 days to nearly 90 days after maximum light. We attribute this feature to He I $1.083\,\mu$m line with a blueshifted velocity of $1.3\times10^{4}$ km s$^{-1}$ and a FWHM of $2.1\times10^{3}$ km s$^{-1}$, supported by the detection of multiple optical He I transitions in earlier epochs at a higher velocity around $1.5\times10^{4}$ km s$^{-1}$. The high velocity of the helium could not be explained by helium external to the progenitor at the explosion, such as the stripped surface helium from a companion star. The properties of the helium absorption in SN 2022an spectra instead point to unburnt material in the outer ejecta, thus providing the most compelling evidence to date for helium-bearing ejecta in a 91bg-like SN Ia. Such helium has been predicted for sub-Chandrasekhar-mass double-detonation explosions involving a surface helium shell. No theoretical calculations of modern helium-shell double detonation have been performed at epochs similar to those observed for SN 2022an to study the effect of helium on their spectra, revealing a gap between observations and theoretical calculations in understanding the manifestation of helium in SNe Ia. Nevertheless, the discovery of persistent helium absorption in SN 2022an demonstrates the diagnostic power of NIR spectroscopy for understanding thermonuclear supernova explosions by probing the abundance and structure of their ejecta.

The atmospheres of super-Earths and sub-Neptunes can be strongly modified by chemical exchange with their molten interiors during long-lived magma ocean phases. Interpreting atmospheric observations requires fast models that self-consistently couple atmospheric chemistry to the composition of the planetary interior. We present an updated implementation of the global chemical equilibrium (GCE) framework from (Schlichting & Young 2022), which computes the equilibrium composition of a coupled metal-silicate-gas system. The numerical solver has been improved using a gradient-based optimizer, reducing the computational cost of solving the chemical network by more than two orders of magnitude and enabling large parameter studies. We apply the framework to a large synthetic population of planets and explore the imprint of bulk refractory composition of Mg, Si, and Fe on atmospheric properties. We consider planets with different masses, thermal states, and volatile inventories. We find that the atmospheric mass fraction and atmospheric metal mass fraction are primarily controlled by the temperature at the atmosphere-magma ocean interface and the planetary water budget, while the accreted hydrogen mass fraction plays a minor role because most hydrogen dissolves into the interior. For planets that accreted water, the refractory ratios Mg/Si and Fe/Si strongly influence carbon partitioning between the gas, silicate, and metal phases, producing large variations in atmospheric atmospheric metal mass fraction and C/O ratios. These results demonstrate that atmospheric compositions of sub-Neptunes depend sensitively on both the volatile inventory and the bulk composition of rocky material, providing new constraints for interpreting atmospheric observations. The new GCE code is open-source.

Ultra-hot Jupiters (UHJs) are exceptional laboratories for studying planetary atmospheres under extreme irradiation conditions. With close-in tidally locked orbits, these planets can have daysides hot enough for metals to be significantly ionized while still maintaining nightsides cold enough for refractory species to potentially condense. We present an analysis of the ultra-hot Jupiter HAT-P-70b taken with the MAROON-X high-resolution spectrograph. Using cross-correlations, we detect 14 neutral and singly ionized species, including Fe I, Fe II, Ti I, Ca I, Ca II, Cr I, Na I, V I, Mn I, Ni I, Mg I, Ba II, O I, and Sr I, with tentative evidence for H I, Co I, and K I. The absorption signals exhibit blueshifts on the order of a few $\mathrm{km\,s^{-1}}$, consistent with day-to-night winds. We further constrain relative abundances with atmospheric retrievals and demonstrate that some inferred elemental abundance ratios depend strongly on modeling assumptions. In particular, we show that a well-mixed retrieval approach neglecting ionization can strongly bias highly ionizable elements such as Ca and Ti. Accounting for the effects of equilibrium chemistry and thermal ionization generally results in inferred elemental abundance ratios that are closer to expectations for a solar-like composition, although not in all cases. Interestingly, we find a distinct nickel enrichment on HAT-P-70b, adding to the growing number of UHJ studies where the Ni abundance is seemingly enhanced. Our results underline the importance of considering physical and chemical atmospheric processes such as ionization when interpreting high-resolution transmission spectra of UHJs.

On October 3rd, 2024, the Sun emitted an X9.0-class flare from active region NOAA 13842. The event was recorded by multiple space-based instruments, beginning hours before the eruption, granting a unique opportunity to provide insight into the flare's pre-flare phase. In this study, we employ analysis of Interface Region Imaging Spectrograph (IRIS) spectroscopic data to investigate pre-flaring phenomena associated with this flare. We present time-series and wavelet analysis of non-thermal velocity, Doppler velocity, and line intensity quantities of the IRIS Si IV 1403 angstrom line. We find two ranges of periodic oscillations during the pre-flare phase: ~7-10 min and ~18-21 min oscillations, with local enhancements occurring near the polarity inversion line. We also find a steady rise in Si IV line parameters beginning 3 hours before the flare in the same region, transitioning into strong non-thermal velocities and blueshifts ~15 minutes before onset. These findings are consistent with a slow destabilization of the coronal magnetic field, possibly driven by the gradual activation of a flux rope, followed by a rapid shift to intense reconnection activity leading to flare onset.

Stellar streams are excellent probes of the gravitational potential in which they evolve. In the Milky Way (MW), globular cluster (GC) streams are routinely used to infer properties about time-dependent perturbations of the underlying potential. This implies that streams with Galactocentric radii small enough to be perturbed by the MW bar should offer constraints on it, such as its pattern speed, which currently has a wide range of values reported in the literature and is important when studying stellar kinematics. The GC M92 has a small pericentre and should be affected by the bar. It has a diffuse stellar stream, but confirming stream members has previously been hindered by a lack of spectroscopic data. In this paper, we use Dark Energy Spectroscopic Instrument (DESI) observations together with photometric and astrometric data to obtain spectroscopic members of the M92 stream for the first time. We identify a clear spatial distribution and gradients in distance moduli, proper motions, and radial velocities that confirm the stream's existence. We compare the observed stream to mock streams generated in different barred potentials and estimate the MW bar's pattern speed $\Omega = 29.1^{+0.7}_{-0.4}$ km s$^{-1}$ kpc$^{-1}$ and $\dot \Omega = 0.7^{+3.5}_{-2.3}$ km s$^{-1}$ kpc$^{-1}$ Gyr$^{-1}$. This is the first time a stellar stream is used to probabilistically infer these bar properties, and it opens up an exciting realm of inner Galactic potential characterisation using stellar streams.

Magnetohydrodynamic (MHD) simulations are indispensable research infrastructure in astrophysics today. In order to satisfy the solenoidal constraint of the MHD equations on discretized grids, modern simulation codes often employ either constrained transport (CT) with a staggered grid or divergence cleaning using an additional variable. We compare CT and Dedner's mixed divergence cleaning schemes systematically, and find that the divergence cleaning scheme can produce substantial artifacts in certain situations. Through numerical experiments including both idealized tests and practical applications, we show that the original implementation of Dedner's scheme becomes inaccurate when magnetic fields are strongly localized or when the timestep suddenly changes. We find that some previous results, such as the extremely rapid growth of magnetic fields during star formation in the early Universe, may be affected by the spurious behavior of the divergence cleaning scheme. We propose a few modifications to improve the robustness of the divergence cleaning method. Nevertheless, we find that the CT scheme is more accurate and reliable in many situations.

Extreme sudden changes in the flow of accreting gas onto SMBHs manifest themselves via large-amplitude continuum variability and changes to broad Balmer emission profiles, driving changing-look AGN. X-ray flux monitoring with SRG/eROSITA revealed that in the Seyfert AGN HE 1237-2252 the soft X-ray flux dipped abruptly, by a factor of 17 within 18 months. We initiated a follow-up campaign that caught the luminosity recovery after the dip, and enabled us to study how the various accretion components responded during this flux recovery. Our campaign included multiband photometry, X-ray spectroscopy, and optical spectroscopy. We tracked as the accretion rate relative to Eddington increased by a factor of 7 in 3 years. Based on broad Hbeta variability, HE 1237-2252 was subtype 1.0-1.2 in 2002, transitioned to subtype 1.8 by the time of the luminosity dip, and then transitioned back to subtype 1.0 within 3 months as luminosity recovered. Both transitions saw broad Hbeta integrated line flux change by factors of 4-6. The broad Balmer profile is decomposed into a broad Gaussian consistent with virialized gas at 27+/-3 lt-dy, plus a double-peaked profile, consistent with a diskline structure at more than roughly 5 lt-dy. The diskline component's relative contribution to the total profile increases as continuum flux rises. The lack of obscuration in the X-ray spectra, as well as the IR continuum dip, point to an intrinsic pause in the accretion rate as opposed to variable line-of-sight obscuration. Candidates for the underlying mechanisms include propagating cold and warm fronts in the accretion disk. The increased prominence of the diskline BLR component's emission could be due to evolution in the physical extent of the X-ray corona, and in the fraction of >13.6 eV photons intercepted by the diskline, as the accretion rate increases.

In the black hole star (BH*) model, the characteristic "V"-shaped SED of LRDs is produced by an accreting BH embedded in a dense neutral-gas envelope with a near-unity covering factor. This envelope reprocesses radiation and emits as a ~5,000K blackbody, producing the optical continuum. Meanwhile, the UV is powered by a low-mass, dust-free, metal-poor host. The BH* scenario is promising, but it has yet to undergo detailed testing; conducting a self-consistent UV-to-optical spectral-fitting analysis of LRDs would provide a robust assessment of the model. In this work, we test the BH* scenario by fitting the full JWST/NIRSpec PRISM spectrum of The Cliff ($z_{spec}=3.55$), an LRD that played a pivotal role in the development of this model. A Bagpipes fit that allows stellar, nebular, AGN, and blackbody components naturally yields a BH*-like solution for The Cliff, even with broad priors. Our method allows us to characterize its host, despite remaining unresolved in JWST imaging. From the continuum, we infer the host to be low-mass (log $M_\star/M_\odot$~7.7), star-forming, metal-poor, affected by non-negligible dust attenuation ($A_V$~0.5 mag) acting on both stellar and nebular components. Larger $M_\star$ (up to log $M_\star/M_\odot$~8.1) and attenuations (up to $A_V$~1 mag) are obtained depending on the assumed dust attenuation law. Modest AGN UV leakage is consistently allowed by the code, but remains weak and not robustly constrained, with both AGN+host and host-dominated UV scenarios yielding equivalent fits. The star formation history of the host is relatively smooth, with the galaxy already assembling log $M_\star/M_\odot$~7 about 200 Myr before $z_{spec}=3.55$. The BH-to-$M_\star$ ratio exceeds the values expected from BH-host scaling relations, especially at recent times. This tension may indicate either inaccurate estimates of the BH properties or non-coeval BH-host evolution.

The [$^{12}$C II] emission at 158 $\mu$m is a key cooling line of the interstellar medium and traces gas kinematics in spectrally resolved observations. Its spectral profile is often modified by optical depth effects. The intrinsic line shape can be reconstructed by comparison with emission from the less abundant $^{13}$C isotope. Due to the additional neutron spin, [$^{13}$C II] emission splits into three hyperfine structure (hfs) transitions. Laboratory measurements have provided the centroid frequency and the strongest component ($F=2-1$); the two weaker components ($F=1-0$ and $F=1-1$) have been inferred only from quantum-mechanical calculations. The magnetic-dipole hfs constants, from which the transition frequencies follow, have not been measured experimentally. The high spectral resolution of observations with the upgraded German Receiver for Astronomy at Terahertz Frequencies (upGREAT) on board SOFIA enabled simultaneous detection of all three hfs transitions. From these astronomical data we determine, for the first time, the magnetic-dipole hfs constants $A_{1/2}^{\rm hf} = 810.71(11)$ MHz and $A_{3/2}^{\rm hf} = 162.18(5)$ MHz of the [$^{13}$C II] $2s^2\,2p\,{}^2P^\circ$ ground term. Combined with the laboratory centroid frequency, this yields the rest frequencies of all three hfs lines. Using [$^{12}$C II] as a reference, we also improve the precision of the [$^{13}$C II] centroid frequency. This work shows that spectrally resolved astronomical observations can constrain fundamental atomic properties, with hfs precision rivaling laboratory measurements. The approach extends to other atomic and molecular transitions where laboratory data are difficult to obtain.

I present the Spitzer Spectroscopic Data Fusion, a collection of merged spectroscopic redshift catalogs covering fourteen of the most widely studied extragalactic survey fields. Building on the Spitzer Data Fusion multi-wavelength photometric database, the collection merges several publicly available spectroscopic redshift catalogs within each field using a 1 arcsec matching radius, delivers a single best redshift per source together with provenance and overlap flags, and is available on Zenodo at this https URL The dataset is regularly updated as new spectroscopic surveys are published. It is intended as a community calibration resource for photometric redshift training, SED fitting, and multi-wavelength cross-identification studies.

Asteroseismology is the study of resonant oscillations of stars to infer their internal structure and dynamics. It is also a powerful tool for precisely determining stellar parameters such as mass, radius, surface gravity, and age. The ongoing TESS mission, with its nearly complete sky coverage, presents a unique opportunity to uniformly probe stellar populations across the Milky Way. TESS is estimated to have observed more than 300,000 oscillating red giants, most of which have one to two months of observations. Given the scale of this dataset, we need a fast, efficient, and robust way to analyse the data. In this work, our objective is to develop a machine learning (ML) based method to infer asteroseismic parameters from short-duration observations. Specifically, we focus on two global seismic parameters, the large frequency separation ($\Delta\nu$) and the frequency at maximum power ($\nu_{\mathrm{max}}$), from one-month-long TESS observations of red giants. Meanwhile, for K2 data, our focus extends to inferring the period spacings of dipolar gravity modes ($\Delta\Pi_{1}$), in addition to $\Delta\nu$ and $\nu_{\mathrm{max}}$. Our findings demonstrate that our machine learning algorithm can accurately infer $\Delta\nu$ and $\nu_{\mathrm{max}}$ for approximately 50% of samples created by taking one-month Kepler and K2 observations. For TESS one sector data however, we recover reliable $\Delta\nu$ for only about 23% of the stars. Additionally, we get reliable $\Delta\Pi_{1}$ inferences for about 200 young red-giants from K2. For these $\Delta\Pi_{1}$ inferences, we see a good match with the well known $\Delta\nu-\Delta\Pi_{1}$ degenerate sequence observed in Kepler red-giants.

The chiral magnetic effect (CME), arising from the chiral anomaly and enabling a mutual conversion between magnetic topology and fermionic chirality, is a key mechanism in magnetar field evolution. Previous work by Dehman & Pons (2025) demonstrated that the CME can efficiently generate dipolar fields ($B_{\rm dip} \gtrsim 10^{14}~\mathrm{G}$), consistent with magnetar timing measurements, provided that the initial magnetic field carries net helicity. However, whether neutron stars are born with magnetic helicity remains uncertain. In this work, we investigate the CME across a range of initial helicity configurations, including non-helical initial conditions. We find that the CME efficiently generates magnetar-strength dipoles on timescales of decades, independently of the initial helicity content. The instability is driven by localized helical structures that induce a residual chiral asymmetry and is primarily governed by the maximum chiral chemical potential, requiring $\mu_5^{\rm max} \gtrsim \mathrm{few}\times10^{-11}~\mathrm{MeV}$ for onset in the magnetar regime. Our results further show that these dipoles may either remain stable and subsequently evolve through standard Ohmic decay, or become unstable if they acquire sufficient helicity, in which case they decay through the chiral anomaly, transferring energy to less helical modes. This outcome depends sensitively on the initial helicity distribution. These findings extend the applicability of the CME to more realistic magnetic-field configurations and underscore the importance of the helicity distribution at birth, a quantity that remains poorly constrained in neutron star formation, yet is crucial for determining neutron star magnetic evolution and magnetar formation.

Leptophilic sub-MeV spin-1 dark matter (DM) can be converted into a photon via inelastic scattering with a free electron or absorption by a neutral hydrogen atom in the primordial plasma. We study for the first time the impact of the energy injection resulting from such processes on cosmic microwave background (CMB) anisotropies. We obtain upper limits on the vector and axial-vector DM-electron couplings using Planck 2018 temperature, polarization, and lensing data for DM masses between 100 eV and 100 keV. We find that, due to the suppression of the hydrogen atomic form factor at high energies, inelastic scattering provides the dominant constraint for DM masses above the keV scale. At lower masses, hydrogen ionization through DM absorption is the leading channel, driven by the higher efficiency of post-recombination energy injection in modifying the free-electron fraction. Although the bounds we derive are considerably weaker than existing laboratory and astrophysical limits, they provide a robust and independent cosmological probe of leptophilic DM interactions.

We show that Majorana neutrinos convert into antineutrinos in a background of ultralight vector dark matter coupled to lepton number, such as the gauge boson of $\text{U}(1)_{B-L}$ or $\text{U}(1)_{L_i - L_j}$ with $i, j = e , \mu, \tau$. This effect is suppressed by the small neutrino mass, but the enhancement by long astrophysical baselines can enable future searches for solar and supernova neutrinos to explore uncharted parameter space. For instance, for $\text{U}(1)_{B-L}$ dark matter, the observation of a supernova neutrino burst at DUNE, Hyper-Kamiokande, and JUNO could probe gauge couplings as small as $e^\prime \sim 10^{-32} - 10^{-25}$ for dark matter masses of $m_{A^\prime} \sim 10^{-22} \ \text{eV} - 10^{-14} \ \text{eV}$, beyond the capability of other future probes.

A broad experimental program is targeting the QCD axion band predicted by single-axion solutions to the strong CP problem. Multi-axion theories provide a well-motivated departure from this canonical picture, since additional states generically modify the mass-photon-coupling relation. We investigate the general structure of multi-axion solutions to the strong CP problem and study the different qualitative mass-coupling patterns that arise, including axions to the right of the QCD band, axions in the experimentally accessible region to its left, and scenarios in which the QCD axion band itself is displaced. This general treatment reveals a broad set of phenomenological possibilities that are not captured by more restrictive assumptions. In particular, we identify the structure of Peccei-Quinn symmetry breaking and the relative alignment between the QCD and electromagnetic anomalies as key ingredients determining the location of the axions in parameter space. Combining these ingredients, we derive a general sum rule for $N$-axion systems that incorporates both general PQ breaking and non-universal anomaly coefficients. We apply the framework to the two-axion system and to general multi-axion setups, identifying UV-complete theories in which the different phenomenological regimes arise naturally. Our results motivate an extended axion search program and have implications for our understanding of fundamental physics and the ultraviolet completion of the Standard Model.

The presence of a chiral asymmetry in a relativistic plasma opens a tachyonic instability toward the growth of a helical magnetic field. We study the transfer of energy from the chiral asymmetry into the magnetic field during the development of this chiral plasma instability. We find that there is more energy stored in the initial chiral asymmetry than goes into growing magnetic field and that the excess energy is transferred to the thermal bath. Consequently, we find that the chiral plasma instability is accompanied by a heating of the plasma, and the temperature increase is parametrically $\delta T \sim \mu_5^2 / T$ if the ratio of chemical potential to temperature is small, i.e. $\mu_5/T \ll 1$. We briefly remark on possible observable implications for early universe cosmology.

We explore an uncharted corner of dark matter phenomenology: non-supersymmetric spin-$3/2$ dark matter with baryon number violating interactions. In an effective field theory description, we identify the leading baryonic portal between the spin-$3/2$ state and Standard Model quarks and show that it can account for the observed dark matter abundance through UV freeze-in and Boltzmann-suppressed freeze-in, while the freeze-out region is completely excluded. The resulting phenomenology is distinctive, with relic production controlled by the competition between baryon-violating single-particle processes and baryon-conserving pair production. We map the viable parameter space against indirect detection, direct detection, and LHC monojet bounds, finding strong complementarity between these probes and especially stringent limits when production and decay are tied to the same operator. We also present a dark QCD-like ultraviolet completion in which the spin-$3/2$ particle arises as a composite baryon, naturally generating the effective interactions and mitigating the main theoretical obstacles of elementary higher-spin states. This framework opens a novel and testable connection between baryonic portals, confining dark sectors, and higher-spin dark matter.

The nature of dark matter remains a central unresolved problem in contemporary physics, motivating the exploration of well-defined extensions of the Standard Model. Among these, the Inert Doublet Model provides a minimal and theoretically consistent framework accommodating a viable weakly interacting massive particle dark matter candidate. In this work, we investigate the IDM parameter space through an analysis of FermiLAT observations of dark matter mini-spikes surrounding stellar-mass black holes. Owing to the strong gravitational compression of dark matter in the vicinity of these systems, the resulting annihilation signal can be significantly enhanced, rendering such environments exceptionally sensitive probes of dark matter interactions. We find that substantial regions of the IDM parameter space, particularly in the high-mass regime, are subject to stringent constraints extending into the multi-TeV range. These results underscore the increasingly important role of indirect detection in probing particle dark matter scenarios beyond the reach of current collider and direct detection experiments.

Persistence diagrams provide stable, interpretable summaries of geometric and topological structure and are useful for simulation-based inference when low-order statistics miss key information. Yet persistence-based pipelines require hand-chosen filtrations, vectorizations, and compressors, typically without an objective tied to parameter uncertainty. We introduce \textbf{TopoFisher}, a differentiable persistent-homology pipeline that learns topological summaries by maximizing local Gaussian Fisher information. Using simulations near a fiducial parameter, TopoFisher optimizes trainable filtrations, diagram vectorizations, and compressors without posterior samples or supervised regression targets, while retaining stable topological inductive bias. We also give sufficient regularity conditions for the log-determinant Fisher loss to be locally Lipschitz in trainable parameters. Controlled experiments on noisy spirals and Gaussian random fields, where total Fisher information is known, show that TopoFisher recovers much of the available information and outperforms fixed topological vectorizations. Our main results are on weak gravitational lensing, a high-dimensional non-Gaussian cosmological field-inference problem. Learned topological summaries reach higher Fisher information than state-of-the-art cosmological summaries and approach an unconstrained Information Maximising Neural Network baseline with up to $\sim80\times$ fewer parameters. The learned filtrations also generalize better: under simulator shift from lognormal to LPT-based maps it retains most Fisher information, while the neural baseline drops, and in neural posterior estimation they give tighter constraints than the neural baseline, and of state-of-the-art cosmological summaries. These results support Fisher-based topological optimization as a robust, parameter-efficient front end for simulation-based inference.