Papers for Tuesday, Mar 18 2025

We show that Laser Interferometer Space Antenna can uniquely identify the sites of intermediate-mass binary black hole (IMBBH) mergers if they occur in Active Galactic Nuclei (AGN) disks with a gas density $\rho\geq10^{-12} \, {\rm g/cc}$ via measurement of dynamical friction effect in the gravitational waveform. We find that even a single observation of a gravitational wave source with a total mass of $10^3 M_{\odot}$ and a mass ratio of 2 at a luminosity distance of 3 Gpc is sufficient to confidently associate the merger to be in an AGN disk with a density $\sim 10^{-12} \, {\rm g/cc}$, as it allows estimation of the density with an error bar ${\cal O}(100\%)$. This provides a new way of inferring AGN disk densities that complement traditional X-ray observations. Further, we find that neglecting the presence of environmental effects in the waveform models used for parameter estimation can bias the chirp mass, mass ratio and arrival time of a merger. If not corrected, this can significantly impact our ability to carry out multiband data analysis of IMBBHs that combines information from LISA and the ground-based gravitational wave detectors.

We present and analyse the results of the Science data challenge 3a (SDC3a, this https URL), an EoR foreground-removal community-wide exercise organised by the Square Kilometre Array Observatory (SKAO). The challenge ran for 8 months, from March to October 2023. Participants were provided with realistic simulations of SKA-Low data between 106 MHz and 196 MHz, including foreground contamination from extragalactic as well as Galactic emission, instrumental and systematic effects. They were asked to deliver cylindrical power spectra of the EoR signal, cleaned from all corruptions, and the corresponding confidence levels. Here we describe the approaches taken by the 17 teams that completed the challenge, and we assess their performance using different metrics. The challenge results provide a positive outlook on the capabilities of current foreground-mitigation approaches to recover the faint EoR signal from SKA-Low observations. The median error committed in the EoR power spectrum recovery is below the true signal for seven teams, although in some cases there are some significant outliers. The smallest residual overall is $4.2_{-4.2}^{+20} \times 10^{-4}\,\rm{K}^2h^{-3}$cMpc$^{3}$ across all considered scales and frequencies. The estimation of confidence levels provided by the teams is overall less accurate, with the true error being typically under-estimated, sometimes very significantly. The most accurate error bars account for $60 \pm 20$\% of the true errors committed. The challenge results provide a means for all teams to understand and improve their performance. This challenge indicates that the comparison between independent pipelines could be a powerful tool to assess residual biases and improve error estimation.

JWST spectroscopy has revealed a population of compact objects at redshifts $z=2$-9 with `v'-shaped spectral energy distributions, broad permitted lines, and, often, hydrogen Balmer absorption. Among these `Little Red Dots' (LRDs), Abell2744-QSO1 at $z=7.04$ has been confirmed to have time-variable equivalent width (EW) in its broad emission lines, confirming its AGN nature. We extend the analysis of NIRSpec/IFS data from the BlackTHUNDER survey to the H$\alpha$ line. The broad-line profile in Abell2744-QSO1 is manifestly non-Gaussian, requiring at least two Gaussian components with full width at half maximum FWHM=$450\pm50$ and $1800\pm100$ km s$^{-1}$. Crucially, we also detect a narrow-line Gaussian component, and strong H$\alpha$ absorption (EW relative to the continuum $\approx 30^{+15}_{-9}$ A), confirming a connection between the strong Balmer break and line absorption. The absorber is at rest with respect to broad H$\alpha$, suggesting that the gas cannot be interpreted as an inflow or outflow, forming instead a long-lived structure. Its velocity dispersion is $\sigma_{abs} = 100\pm10$ km s$^{-1}$, consistent with the value inferred from the analysis of the Balmer break. Based on H$\alpha$, we infer a black hole mass of log(M$_{BH}$/M$_\odot$)=6.3-6.7, 0.9-1.3 dex smaller than previous estimates based on H$\beta$. The Eddington ratio is 0.7-1.6. Combining the high signal-to-noise ratio of the narrow H$\alpha$ line with the spectral resolution R=3,700 of the G395H grating, we infer a narrow-line dispersion $\sigma_n = 22^{+5}_{-6}$ km s$^{-1}$, which places a stringent constraint on the black-hole-to-dynamical-mass ratio of this system to be M$_{BH}$/M$_{dyn}$>0.02-0.4. If M$_{BH}$ is near the low-mass end of our estimates, the SMBH would be accreting at a super-Eddington rate. Alternatively, at the high-M$_{BH}$ end, there would be minimal room for a host galaxy.

Pseudo-Nambu-Goldstone (pNG) Higgs Inflation is a novel approach to relate the Higgs boson and its interaction with Electroweak gauge bosons with cosmic inflation, with the potential of solving both the fine-tuning issues in the Higgs mass and inflationary potentials. In this work, we present a linear perturbation analysis of the minimal implementation of pNG Higgs inflation using the symmetry coset SU($5$)/SO($5$). Similar to Chromo-natural inflation, this model exhibits a period of instability in the tensor modes that exponentially enhance left-handed gravitational waves. Thus, large Chern-Simons couplings $\beta \gtrsim 6 \times 10^8$ and decay constants $f\gtrsim1\times10^{18}~\mathrm{GeV}$ are required to suppress the tensor-to-scalar ratio $r$ to be compatible with the cosmic microwave background (CMB) measurement. These large couplings also cause an overproduction of the scalar modes, making the minimal construction of pNG Higgs inflation disfavored by CMB observations. However, this tension could potentially be relieved by considering multi-field inflation. The pNG Higgs construction naturally contains multiple scalar fields via the interplay of spontaneously broken global and gauge symmetries. The rich structure enables a broad range of multi-field inflation, and we conclude by briefly discussing this possibility and future work.

We present the first numerical relativity simulations including neutrino flavor transformations that could result from flavor instabilities, quantum many-body effects, or potential beyond standard model physics in neutron star mergers. We find that neutrino flavor transformations impact the composition and structure of the remnant, potentially leaving an imprint on the post-merger gravitational-wave signal. They also have a significant impact on the composition and nucleosynthesis yields of the ejecta.

We introduce a python package called ECHO21 for generating global 21-cm signal from the dark ages through cosmic dawn to the end of reionization. Because of its analytical-prescription-based foundation, ECHO21 generates a single model in $\mathcal{O}(1)\,$s. The code can generate a large set of signals, ideal for building emulators and performing astrophysical or cosmological inference from a given 21-cm dataset. The code is MPI parallel with reasonable scalability and thus, can be run on high-performance computers. We offer six astrophysical parameters that control the Lyman-$\alpha$ emissivity, X-ray emissivity, emissivity of ionizing photons, and star formation rate. A critical component of 21-cm modelling, but ignored by majority of public codes, that we include is the Ly$\alpha$ heating. For a certain range of astrophysical parameters, the Ly$\alpha$ heating could even dominate the X-ray heating. In addition to astrophysical parameters, in ECHO21 it is just as easy to vary the standard cosmological parameters which makes it possible to combine constraints from 21-cm observations and other cosmological probes. Further, we offer two models of star formation rate; a physically-motivated and an empirically-motivated. Since the latter is directly inferred by HST/JWST observations, it makes ECHO21 an appropriate tool to build synergies between 21-cm observations and galaxy surveys. With a number of 21-cm experiments soon to provide cosmic dawn 21-cm data, ECHO21 is a handy package for making quick but sufficiently realistic astrophysical inferences.

Wide-orbit planets are particularly sensitive to detection by the Roman Galactic Bulge Time Domain Survey (GBTDS). This study investigates the degeneracy of these events with binary sources, focusing on how observation cadence affects the resolution of these degeneracies. We analyzed the impact of various cadences from (3.6 min)^(-1) to (5 hr)^(-1), which encompasses planned cadences for both the GBTDS and cadences used by ground-based surveys like KMTNet. The results show that a $\sim (15 min)^(-1) cadence is generally sufficient to resolve this degeneracy unless the source star is a giant (rho >~ 0.01).

We present distances to ten supernova (SN) host galaxies determined via the red giant branch tip (TRGB) using JWST/NIRCAM and the F115W, F356W, and F444W bandpasses. Our analysis, including photometric catalog cleaning, adoption of disk light profiles, TRGB color slope estimation, and a novel technique for identifying the infrared TRGB, was conducted blinded. The new F115W TRGB distances agree well with our previously derived HST TRGB distances, differing by only 1 percent on average and 4 percent on a per-galaxy basis. The color-corrected F115W TRGB is therefore equally precise a method of distance measurement as, and offers unique advantages over, its color-insensitive, I-band counterpart. Using these distances, we update the absolute calibrations of eleven calibrator SNe, yielding 68.4 < H0 < 69.6 km/s/Mpc depending on which of four sets of SN magnitudes are used. We expand the sample of calibrator SNe to 24 by combining with HST TRGB distances. Doing so increases our H0 estimate based on the Carnegie Supernova Project II (CSP-II) by 0.8 km/s/Mpc (1.4 sigma) demonstrating that our JWST H0 based on 11 SNe is not significantly biased toward lower values. In contrast, the Pantheon+ calibration shifts higher by +2 km/s/Mpc (3.1 sigma), a significantly larger increase than seen in both the CSP and the Pantheon team's own SuperCal analysis. More JWST observations of the TRGB as well as independent analyses of low-redshift SNe are needed to continue unraveling the true nature of the Hubble Tension.

circumgalactic medium (CGM), the metagalactic ultraviolet background (UVB) plays a significant role in determining the ionization state of different metal species. However, the UVB is uncertain with multiple models having been developed by various research groups over the past several decades. In this work, we examine how different UVB models influence the ionic column densities of CGM absorbers. We use these UVB models to infer ion number densities in the FOGGIE galaxy simulations at $z=2.5$ and use the Synthetic Absorption Line Surveyor Application (SALSA) package to identify absorbers. Absorbers are then matched across UVB models based on their line of sight position so that their column densities can be compared. From our analysis, we find that changing the UVB model produces significant changes in ionization, specifically at lower gas densities and higher temperatures where photoionization dominates over collisional ionization. We also find that the scatter of column density differences between models tends to increase with increasing ionization energy, with the exception of \hi, which has the highest scatter of all species we examined.

HD93129A is an O+O stellar system whose CWR has been mapped by high angular resolution observations at cm wavelengths. The synchrotron nature of the radio emission confirms its particle accelerator status. According to astrometric measurements since 1996, the system has an orbital period of ~120 yr and recently went through its periastron passage. We characterize the radio emission during the epoch of periastron passage, when the particle density and the local magnetic energy density in the CWR increase. We monitored HD93129A and surroundings at 2.1, 5.5 and 9 GHz with the ATCA over 17 months, with a ~2-month cadence. Previous ATCA data and data collected using other radio observatories were also included. We obtained radio light curves in subbands per band per epoch. The flux densities show an average rise of a factor four from 2003 to 2018, with the caveat that the 2009-2018 time lapse is devoid of data, and a similar decay between 2018 to 2020. We fit the spectral energy distribution of quasi-simultaneous data at three epochs and find that the magnetic-to-thermal pressure ratio does not remain constant along the orbit, possible suggesting magnetic field amplification close to periastron. In the 2019 epoch, we estimate a magnetic field strength of ~1.1G in the apex of the CWR. The evolution of the SED and spectral index is also presented. By combining ATCA and ASKAP images a spectral index map was obtained in an area of 30' size. The radio emission in the direction of other massive binary systems in the field (WR22, WR25 and HD93250) was measured and briefly discussed. Intensive radio monitoring allows us to track the evolution of physical conditions in the shocks. The general trend of decreasing emission of HD93129A in the high-frequency bands in 2019-2020 suggests that the system is at post-periastron, consistent with model predictions. (Abridged)

Star clusters can interact and merge in galactic discs, halos, or centers. We present direct N-body simulations of binary mergers of star clusters with $M_{\star} = 2.7 \times 10^4 \: \mathrm{M_{\odot}}$ each, using the N-body code BIFROST with subsystem regularisation and post-Newtonian dynamics. We include 500 $\mathrm{M_{\odot}}$ massive black holes (MBHs) in the progenitors to investigate their impact on remnant evolution. The MBHs form hard binaries interacting with stars and stellar black holes (BHs). A few Myr after the cluster merger, this produces sizable populations of runaway stars ($\sim$800 with $v_{\mathrm{ej}} \gtrsim 50 \mathrm{kms^{-1}}$) and stellar BHs ($\sim$30) escaping within 100 Myr. The remnants lose $\sim30\%$ of their BH population and $\sim3\%$ of their stars, with $\sim$30 stars accelerated to high velocities $\gtrsim 300 \mathrm{kms^{-1}}$. Comparison simulations of isolated clusters with central hard MBH binaries and cluster mergers without MBHs show that the process is driven by MBH binaries, while those with a single 1000 $\mathrm{M_{\odot}}$ MBH in isolated or merging clusters produce fewer runaway stars at lower velocities. Low-eccentricity merger orbits yield rotating remnants ($v_{\mathrm{rot}} \sim 3 \mathrm{kms^{-1}}$) , but probing the presence of MBHs via kinematics alone remains challenging. We expect the binary MBHs to merge within a Hubble time, producing observable gravitational-wave (GW) events detectable by future GW detectors such as the Einstein Telescope and LISA. The results suggest that interactions with low-mass MBH binaries formed in merging star clusters are an important additional channel for producing runaway and high-velocity stars, free-floating stellar BHs and compact objects.

The Galactic Centre region contains a dense accumulation of stars, which can be separated into two components: A flattened and dense nuclear star cluster (NSC), and a surrounding, more extended and more flattened, nuclear stellar disc (NSD). Previous studies have collected a few thousand spectra of the inner NSC, and also the outer NSD, and measured line-of-sight velocities and metallicities. Until now, such measurements exist only for a few 100 stars in the region where the stellar surface density transitions from being dominated by the NSC into being dominated by the NSD. We want to study the stellar population from the centre of the NSC out to well beyond its effective radius, where the NSD dominates. We investigate whether and how the mean properties and kinematics of the stars change systematically. We conducted spectroscopic observations with Flamingos-2 in the K-band via a continuous slit-scan. The data extend from the central NSC into the inner NSD, out to 32 pc from Sgr A* along Galactic longitude l. Based on their CO equivalent width, we classify the stars as hot or cool stars. The former are massive, young stars, while almost all of the latter are older than one to a few Gyr. We measure the overall metallicity [M/H] and line-of-sight velocity for >2,500 cool stars, and present the first continuous spatial maps and profiles of the mean value of various stellar and kinematic parameters. We identify hot, young stars across the field of view. Some stars appear to be isolated, while others accumulate near the Quintuplet cluster or the central parsec cluster. The position-velocity curve of the cool stars shows no dependence on [M/H], but it depends on the colour of the stars. The colour may be a tracer of the line-of-sight distance and thus distinguish stars located in the NSC from those in the NSD. [abridged]

The Trinity Demonstrator is a proof of concept prototype for the Trinity Neutrino Observatory, which is sensitive to astrophysical neutrinos above PeV energies. The Demonstrator is a one-square meter class imaging atmospheric Cherenkov telescope deployed on Frisco Peak, Utah, and remotely operated. The light-collection surface is equipped with 77 mirror facets with 15 cm diameter, and its $3.87^\circ\times3.87^\circ$ field of view is instrumented with a 256-pixel camera yielding a $0.24^\circ$ angular resolution. The camera signals are digitized with a 100 MS/s, and 12-bit resolution switched capacitor array readout. We discuss the Demonstrator's design, the telescope's deployment on Frisco Peak, and its commissioning.

Population synthesis modeling of the observed dynamical and physical properties of a population is a highly effective method for constraining the underlying birth parameters and evolutionary tracks. In this work, we apply a population synthesis model to the canonical magnetar population to gain insight into the parent population. We utilize simulation-based inference to reproduce the observed magnetar population with a model which takes into account the secular evolution of the force-free magnetosphere and magnetic field decay simultaneously and self-consistently. Our observational constraints are such that no magnetar is detected through their persistent emission when convolving the simulated populations with the XMM-Newton EPIC-pn Galactic plane observations, and that all of the $\sim$30 known magnetars are discovered through their bursting activity in the last $\sim50$ years. Under these constraints, we find that, within 95 % credible intervals, the birth rate of magnetars to be $1.8^{+2.6}_{-0.6}$ kyr$^{-1}$, and lead to having $10.7^{+18.8}_{-4.4}$ % of neutron stars born as magnetars. We also find a mean magnetic field at birth ($\mu_b$ is in T) $\log\left(\mu_b\right) = 10.2^{+0.1}_{-0.2}$, a magnetic field decay slope $\alpha_d = 1.9 ^{+0.9}_{-1.3}$, and timescale $\tau_d = 17.9^{+24.1}_{-14.5}$ kyr, in broad agreement with previous estimates. We conclude this study by exploring detection prospects: an all-sky survey with XMM-Newton would potentially allow to get around 7 periodic detections of magnetars, with approximately 150 magnetars exceeding XMM-Newton's flux threshold, and the upcoming AXIS experiment should allow to double these detections.

Low-mass, metal-enriched stars were likely present as early as cosmic dawn. In this work, we investigate whether these stars could have hosted planets in their protoplanetary disks. If so, these would have been the first planets to form in the Universe, emerging in systems with metallicities much lower than solar. In the core accretion model, planetesimals serve as the building blocks of planets, meaning that planetesimal formation is a prerequisite for planet formation. In a non-structured disk, planetesimal formation typically requires near-solar metallicities according to our current understanding. However, mechanisms that concentrate solid material can significantly lower this metallicity threshold. Here, we explore whether vortices can facilitate the formation of the first planets and planetesimals at cosmic dawn. Vortices are prime sites for planetesimal formation due to their ability to efficiently trap and concentrate dust. We conduct simulations spanning a range of metallicities, and identify a metallicity threshold at Z >=~ 0.04 Zsun for planetesimal formation. If these planetesimals remain inside the vortex long enough to accrete the remaining trapped solids, Mercury-mass planets can form. The formation of Mars-mass planets or larger requires a metallicity of Z >=~ 0.08 Zsun. These results assume a low level of disk turbulence, with higher turbulence levels leading to higher metallicity thresholds.

Stellar UV spectra are fundamental diagnostics of physical and magnetic properties of stars. For instance, lines like Mg II at 280 nm serve as valuable indicators of stellar activity, providing insights into the activity levels of Sun-like stars and their potential influence on the atmospheres of orbiting planets. On the other hand, the effective temperature (Teff) is a fundamental stellar parameter, critical for determining stellar properties such as mass, age, composition and evolutionary status. In this study, we investigate the temperature sensitivity of three lines in the mid-ultraviolet range (i.e., Mg II 280.00 nm, Mg I 285.20 nm, and Si I 286.15 nm). Using spectra from the International Ultraviolet Explorer (IUE), we analyze the behavior of the ratios of their corresponding indices (core/continuum) for a sample of calibrating solar-like stars, and find that the ration R = Mg II/Mg I best traces Teff through a log-log relation. The Teff estimated using this relation on a test-sample of solar-like stars agree with the Teff from the literature at the 95% confidence level. The observed results are interpreted making use of Response Functions as diagnostics. This study extends the well-established use of line depth ratio-temperature relationships, traditionally applied in the visible and near-infrared ranges, to the mid-UV spectrum. With the growing interest in stellar UV spectroscopy, results presented in this paper are potentially relevant for future missions as HWO, MANTIS and UVEX.

We examine the relationship between circumnebular extinction and core mass for sets of [O III]-bright planetary nebulae (PNe) in the Large Magellanic Cloud and M31. We confirm that for PNe within one magnitude of the Planetary Nebula Luminosity Function's (PNLF's) bright-end cutoff magnitude (M*), higher core-mass PNe are disproportionally affected by greater circumnebular extinction. We show that this result can explain why the PNLF cutoff is so insensitive to population age. In younger populations, the higher-mass, higher-luminosity cores experience greater circumnebular extinction from the dust created by their AGB progenitors compared to the lower-mass cores. We further show that when our core-mass-nebular extinction law is combined with post-AGB stellar evolutionary models, the result is a large range of population ages where the brightest PNe all have nearly identical [O III] luminosities. Finally, we note that while there is some uncertainty about whether the oldest stellar populations can produce planetary nebulae as bright as M*, this issue is resolved if the initial-final mass relation (IFMR) for the lowest-mass stars results in slightly more massive cores, as observed in some clusters. Alternatively, introducing a small amount of intrinsic scatter (0.022 Msun) into the IFMR also addresses this uncertainty.

Fast radio bursts (FRBs) are fierce radio flashes from the deep sky. Abundant observations have indicated that highly magnetized neutron stars might be involved in these energetic bursts, but the underlying trigger mechanism is still enigmatic. Especially, the widely expected periodicity connected to the spin of the central engine has never been discovered, which leads to further debates on the nature of FRBs. Here we report the first discovery of a $\sim 1.7$ s period in the repeating source of FRB 20201124A. This is an active repeater, from which more than 2800 FRBs have been observed on a total of 49 days. The phase-folding method is adopted to analyze the bursts on each day separately. While no periodical signal is found in all other datasets, a clear periodicity does appear on two specific days, i.e. a period of $1.706015(2)$ s on MJD 59310, and a slightly larger period of $1.707972(1)$ s on MJD 59347. A period derivative of $6.14\times10^{-10}$ s s$^{-1}$ can be derived from these two periods, which further implies a surface magnetic field strength of $1.04\times10^{15}$ G and a spin-down age of $44$ years for the central engine. It is thus concluded that FRB 20201124A should be associated with a young magnetar.

A long-standing enigma in observational astronomy is the identification of the so-called 21 $\mu$m feature in a subset of envelopes of post-asymptotic giant branch (post-AGB) stars. Identifying this transient feature is important for understanding the chemical processes during the brief post-AGB phase and the enrichment of the interstellar medium. Understanding the structures and chemical environments of these objects is a prerequisite for such an endeavor. We investigate the structure of the circumstellar envelope and the spatial distribution of gas-phase molecules in the 21 $\mu$m source IRAS 23304+6147, aiming to explor the potential physicochemical conditions required for the emergence of the 21 $\mu$m feature. Molecular line observations toward IRAS 23304+6147 at the 1.3 mm band were performed using the Northern Extended Millimeter Array. A morpho-kinematic model was built to reproduce the observed $^{13}$CO images and to decipher the structures of the nebula. The imaging results reveal an elliptically elongated shell with an equatorial density enhancement (or a torus-like structure),and in detail how the various molecules distribute in the envelope. The nebular morphology points to a binary system in which the ultraviolet radiation from the companion may trigger photochemistry in the inner regions. The torus-like structure exhibits an enrichment of linear carbon-chain molecules and a depletion of silicon-bearing molecules. The chemically stratified structure of $^{13}$CN, HC$_3$N, and C$_4$H represents an observational evidence of the internal radiation that initiates photochemistry. The carbon-rich torus-like structure probably offers a conducive environment for the formation of dust and complex molecules implicated in the rare 21 $\mu$m emission.

Magnetars, highly magnetized neutron stars, host superconducting and superfluid phases. We develop a minimal model that captures the interplay between neutron superfluidity, proton superconductivity, and electromagnetic fields using the Gross-Pitaevskii-Poisson, Ginzburg-Landau, and Maxwell equations. Our numerical simulations show that strong rotation enhances the net magnetic field inside the magnetar, suppresses superconductivity there, and amplifies the field near the surface. We explain this by a theory that makes testable predictions, including gravitational-wave signatures.

In this work, we study the generation of gravitational waves in the E-model inflation with the scalar field non-minimally coupled to the Gauss-Bonnet term. Considering a wall-crossing behavior in the moduli space, we parameterize the coupling coefficient $\xi$ as a step-like function, then if $V_{,\phi}\xi_{,\phi}>0$, the Gauss-Bonnet term dominate the inflation dynamics, causing a short rapid-decline phase of the inflaton, and for appropriate parameter spaces, the mode equation of tensor perturbations develops a transient growing solution. This process generates a peak in the tensor perturbation power spectrum, corresponding to a peak in the gravitational wave energy spectrum around the nanohertz frequency band. Further more, we investigate the feasibility of generating double peaks in the gravitational wave spectrum using a double-step coupling, For certain parameter choices, one peak lies near nanohertz frequencies, while the other is around millihertz frequencies. Consequently, these gravitational waves can be observed by the pulsar timing array and the space-based gravitational wave detectors such as LISA, simultaneously.

Understanding the molecular gas content in the interstellar medium (ISM) is crucial for studying star formation and galaxy evolution. The CO-to-H$_2$ ($X_{\rm CO}$) and the [CI]-to-H$_2$ ($X_{\rm CI}$) conversion factors are widely used to estimate the molecular mass content in galaxies. However, these factors depend on many ISM environmental parameters. This work investigates the dependence of $X_{\rm CO}$ and $X_{\rm CI}$ on these parameters, with a focus on the low-metallicity $\alpha$-enhanced ISM ($\rm [C/O]<0$), to provide improved tracers of molecular gas in diverse conditions. We used the PDFchem algorithm, coupled with a database of 3D-PDR models. These account for a wide range of metallicities, dust-to-gas mass ratios, FUV intensities, and cosmic-ray ionization rates. The conversion factors were computed by integrating the PDR properties over log-normal column density distributions ($A_{\rm V}$-PDFs) representing various cloud types. The $X_{\rm CO}$ factor increases significantly with decreasing metallicity, exceeding $\sim\!\!1000$ times the Galactic value at ${\rm [O/H] = -1.0}$ under $\alpha$-enhanced conditions, as opposed to $\sim\!\!300$ times under non-$\alpha$-enhanced conditions (${\rm [C/O]=0}$). In contrast, $X_{\rm CI}$ shows a more gradual variation with metallicity, making it a more reliable tracer of molecular gas in metal-poor environments under most conditions. The fraction of `CO-dark' molecular gas increases dramatically in low-metallicity regions, exceeding 90\% at ${\rm [O/H] = -1.0}$, particularly in diffuse clouds and environments with strong FUV radiation fields. We recommend the use of the $\log_{10}X_{\rm CO}\simeq-2.41Z+41.3$ relation for the CO-to-H$_2$ conversion factor, and the $\log_{10}X_{\rm CI}\simeq-0.99Z+29.7$ relation for the [CI]-to-H$_2$, where $Z=12+\log_{10}({\rm O/H})$.

We carry out NLTE (non local thermodynamic equilibrium) radiative transfer simulations to determine whether explosion during the merger of a carbon-oxygen (CO) white dwarf (WD) with a helium (He) WD can reproduce the characteristic Ca II/[Ca II] and He I lines observed in Ca-rich transients. Our study is based on a 1D representation of a hydrodynamic simulation of a 0.6 $M_{\odot}$ CO + 0.4 $M_{\odot}$ He WD merger. We calculate both photospheric and nebular-phase spectra including treatment for non-thermal electrons, as is required for accurate modelling of He I and [Ca II]. Consistent with Ca-rich transients, our simulation predicts a nebular spectrum dominated by emission from [Ca II] 7291, 7324 angstrom and the Ca II near-infrared (NIR) triplet. The photospheric-phase synthetic spectrum also exhibits a strong Ca II NIR triplet, prominent optical absorption due to He I 5876 angstrom and He I 10830 angstrom in the NIR, as is commonly observed for Ca-rich transients. Overall, our results therefore suggest that CO+He WD mergers are a promising channel for Ca-rich transients. However, the current simulation overpredicts some He I features, in particular both He I 6678 and 7065 angstrom and shows a significant contribution from Ti II, which results in a spectral energy distribution that is substantially redder than most Ca-rich transients at peak. Additionally the Ca II nebular emission features are too broad. Future work should investigate if these discrepancies can be resolved by considering full 3D models and exploring a range of CO+He WD binary configurations.

Outflows/jets are ubiquitous in a wide range of astrophysical objects, yet the mechanisms responsible for their generation remain elusive. One hypothesis is that they are magnetically driven. Based on general relativistic MHD equations, we establish a formulation to describe the outflows driven by large-scale magnetic fields from the accretion disk in Schwarzschild spacetime. The outflow solution manifests as a contour level of a ``Bernoulli" function, which is determined by ensuring that it passes through both the slow and fast magnetosonic points. This approach is a general relativistic extension to the classical treatment of Cao and Spruit (1994). The initial plasma $\beta$ that permits magnetically driven outflow solutions is constrained, with the slow magnetosonic point above the footpoint setting an upper limit ($\beta_\mathrm{b}\lesssim 2$) and the Alfvén point inside the light cylinder setting a lower limit ($\beta_\mathrm{b}\gtrsim 0.02$). The higher the magnetization, the higher the temperature allowed, leading to relativistic outflows/jets. We investigate the relativistic outflows/jets of several typical objects such as active galactic nuclei (AGN), X-ray binaries (XRBs) and gamma-ray bursts (GRBs). The results indicate that all of these phenomena require strongly magnetized, high-temperature outflows as initial conditions, suggesting a potential association between the production of relativistic outflows/jets and corona-like structures.

We report the discovery of a radio megahalo in the merging cluster PLCKG287.0+32.9, based on upgraded Giant Metrewave Radio telescope (uGMRT) observations at frequencies 300-850 MHz. The sensitive radio observations provide a new window to study the complex physics occurring in this system. Apart from significant detections of the known diffuse radio emission in the cluster, we detect the central diffuse emission to a much larger extent of $\sim$ 3.2 Mpc, reaching the R$_{500}$ of the cluster. The radial surface brightness profile shows a distinct flattening beyond $\sim$0.5R$_{500}$, dividing the emission into inner and outer components. This outer envelope shows a steep spectral index ($\lesssim$ -1.5) and, emissivity $\sim 20$ times lower than the inner component, confirming the megahalo characteristics. The radial profile of the spectral index also distinguishes the steep spectrum megahalo emission. Our observational results align with recent numerical simulations, showing megahalo emission oriented along the merger axis and the re-acceleration of electrons driven by late-stage merger-induced turbulence. This is the first detection of a radio megahalo at a frequency higher than the LOFAR 144 MHz, opening the possibilities for more discoveries and spectral studies to understand their origin.

We investigate the period changes of 13 short-period Type II Cepheids using the O-C method over a century-long data baseline. The O-C diagrams for these stars exhibit a parabolic trend, indicating both increasing and decreasing period changes over time. These observed period changes are consistent with recent theoretical models based on horizontal branch evolutionary models for short-period BL Her stars. The pulsation stability test proposed by Lombard and Koen confirms that the period changes are signficant, indicating evolutionary shifts. We identify seven BL Her stars with decreasing periods, expanding the existing sample size of short-period Type II Cepheids. This contributes to a deeper understanding of stellar evolution and the processes governing low-mass stars.

Solar flares are the most powerful, magnetically-driven, explosions in the heliosphere. The nature of magnetic energy release in the solar corona that heats the plasma and accelerates particles in a flare, however, remains poorly understood. Here, we report high-resolution coronal observations of a flare (SOL2024-09-30T23:47) by the Solar Orbiter mission that reveal initially weaker but rapid reconnection events, on timescales of at most a few seconds, leading to a more prominent activity of similar nature that explosively cause a flare. Signatures of this process are further imprinted on the widespread raining plasma blobs with short lifetimes, giving rise to the characteristic ribbon-like emission pattern associated with the flare. Our novel observations unveil the central engine of a flare and emphasize the crucial role of an avalanche-like magnetic energy release mechanism at work.

Many studies have revealed that the core mass function (CMF) in high-mass star-forming regions is top-heavy. In this work, we start from the canonical initial mass function (IMF) to inversely synthesize the observed CMFs of high-mass star formation regions, taking into account variations in multiplicity and mass conversion efficiency from core to star ($\epsilon_{\rm core}$). To match the observed CMFs, cores of different masses should have varying $\epsilon_{\rm core}$, with $\epsilon_{\rm core}$ increasing as the core mass decreases. However, the multiplicity fraction does not affect the synthesized CMFs. To accurately fit the high-mass end of the CMF, it is essential to determine whether the CMF shows a slope transition from the low-mass end to the high-mass one. If the CMF truly undergoes a slope transition but observational biases obscure it, leading to a combined fit with a shallower slope, this could artificially create a top-heavy CMF.

We reassess the capacity for multimessenger inference of AT2017gfo/GW170817 using both kilonova and gravitational wave emission within the context of a recent simulation-based surrogate model for kilonova emission. Independent of the inclusion of gravitational wave observations, comparisons between observations that incorporate our kilonova model favor a narrow range of ejecta properties, even when allowing for a wide range of systematic uncertainties in our modeling approach. Conversely, we find that astrophysical conclusions about the neutron star itself, including its mass and radius, depend strongly on assumptions about how much material is ejected from the neutron star. Looking forward, our analysis highlights the importance of systematic uncertainty in general, the need for better modeling of neutron star merger mass ejection from first principles, and warns against uncontextualized applications of ejecta predictions using fits to numerical relativity simulations.

The physical role played by small-scale activity that occurs before the sudden onset of solar energetic events (SEEs, i.e., solar flares and coronal mass ejections) remains in question, in particular as related to SEE initiation and early evolution. It is still unclear whether such precursor activity, often interpreted as plasma heating, particle acceleration, or early filament activation, is indicative of a pre-event phase or simply on-going background activity. In this series, we statistically investigate the uniqueness and causal connection between precursors and SEEs using paired activity-quiet epochs. This first paper specifically introduces transient brightenings (TBs) and presents analysis regimes to study their role as precursors, including imaging of the solar atmosphere, magnetic field, and topology analysis. Applying these methods qualitatively to three cases, we find that prior to solar flares, TBs 1) tend to occur in one large cluster close to the future flare ribbon location and below the separatrix surface of a coronal magnetic null point, 2) are co-spatial with reconnection signatures in the lower solar atmosphere, such as bald patches and null point fan traces and 3) cluster in the vicinity of strong-gradient polarity inversion lines and regions of increased excess magnetic energy density. TBs are also observed during quiet epochs of the same active regions, but they appear in smaller clusters not following a clear spatial pattern, although sometimes associated with short, spatially-intermittent bald patches and fan traces, but predominantly away from strong gradient polarity inversion lines in areas with little excess energy density.

We examine the long-term trends in impact factor over the past decade (2015-2014) for seven flagship journals widely used in Astrophysics: ApJ, AJ, ApJL, ApJS,A &A, JCAP, and MNRAS. We check the variation of both the traditional impact factor as well as the median-based impact factor, which we had studied in a previous work. We find that ApJS exhibits the largest drop in impact factor from 14.9 to 9.0, while ApJ and MNRAS show a steady decline from 6.7 to 5.2 and 5.6 to 5.0, respectively. However, the impact factors for AJ and ApJL have shown a steady increase from 4.55 to 5.35 and 6.4 to 9.7, respectively. The median-based impact factors are much more stable showing variations of at most $\pm 1$ within the last decade.

Compact objects undergoing mass transfer exhibit significant (and double-peaked) $H_{\alpha}$ emission lines. Recently, new methods have been developed to identify black hole X-ray binaries (BHXBs) and calculate their systematic parameters using $H_{\alpha}$ line parameters, such as the full-width at half maximum (FWHM), equivalent width (EW), and separation of double peaks. In addition, the FWHM-EW plane from spectroscopy and the $H_{\alpha}$ color-color diagram from photometry can be used for rapid stellar classification. We measure the $H_{\alpha}$ and $H_{\beta}$ profiles (e.g., FWHM and EW) using the LAMOST DR9 low- and medium-resolution spectra, and calculate the systematic parameters (e.g., velocity semi-amplitude of the donor star, mass ratio, inclination angle, and mass of the accretor). A new correlation between FWHM and $K_{\rm 2}$, $K_{\rm 2} = 0.205(18)\ \rm{FWHM}$, is obtained for cataclysmic variables (CVs) in our sample. Both the FWHM-EW plane and the $H_{\alpha}$ color-color diagram can distinguish CVs with FWHM $\gtrsim$ 1000 km/s from Be stars and young stellar objects (YSOs) to some extent. To improve classification accuracy and enhance the selection of compact objects, we propose a new set of idealized filters with effective widths of 30 Å, 130 Å, and 400 Å\ for the narrow $H_{\alpha}$ filter, broad $H_{\alpha}$ filter, and $r$-band filter, respectively.

We investigate the effects of the ALP-mediated dark matter (DM) model on neutron star properties using the Quantum Hadrodynamics model (QHD). Using the relativistic mean-field approximation with the QHD-ALP-DM framework, we compute the equation of state (EoS) of neutron stars. Based on our previous study, we find that typical ALP parameter values have no significant effect on the EoS. We then explore various parametrizations of this model by varying the DM Fermi momentum, $q_f$, and DM mass, $m_{\chi}$. Our results show that increasing $q_f$ or $m_{\chi}$ shifts the energy density to higher values while reducing the maximum mass, radius, and tidal deformability of neutron stars. Finally, comparison with observational constraints from gravitational wave events and pulsar measurements indicates that the allowed parameter space for this model is constrained to $q_f < 0.05$ MeV and $m_{\chi} < 1000$ GeV. As a result, our study highlights the importance of next-generation gamma-ray observatories, such as the Cherenkov Telescope Array (CTA), in probing the ALP-mediated DM model.

We present a pioneering achievement in the high-precision photometric calibration of CMOS-based photometry, by application of the Gaia BP/RP (XP) spectra-based synthetic photometry (XPSP) method to the mini-SiTian array (MST) photometry. Through 79 repeated observations of the $\texttt{f02}$ field on the night, we find good internal consistency in the calibrated MST $G_{\rm MST}$-band magnitudes for relatively bright stars, with a precision of about 4\,mmag for $G_{\rm MST}\sim 13$. Results from more than 30 different nights (over 3100 observations) further confirm this internal consistency, indicating that the 4\,mmag precision is stable and achievable over timescales of months. An independent external validation using spectroscopic data from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) DR10 and high-precision photometric data using CCDs from Gaia DR3 reveals a zero-point consistency better than 1\,mmag. Our results clearly demonstrate that CMOS photometry is on par with CCD photometry for high-precision results, highlighting the significant capabilities of CMOS cameras in astronomical observations, especially for large-scale telescope survey arrays.

Fast Radio Bursts (FRBs) are short-duration, highly-energetic extragalactic radio transients with unclear origins & emission mechanisms. Despite extensive multi-wavelength searches, no credible X-ray or other prompt electromagnetic counterparts have been found for extragalactic FRBs. We present results from a comprehensive search for such prompt X-ray counterparts using AstroSat-CZTI which has been actively detecting other high-energy fast transients like Gamma-ray bursts (GRBs). We undertook a systematic search in AstroSat-CZTI data for hard X-ray transients temporally & spatially coincident with 578 FRBs, and found no X-ray counterparts. We estimate flux upper limits for these events and convert them to upper limits on X-ray-to-radio fluence ratios. Further, we utilize the redshifts derived from the dispersion measures of these FRBs to compare their isotropic luminosities with those of GRBs, providing insights into potential similarities between these two classes of transients. Finally, we explore the prospects for X-ray counterpart detections using other current and upcoming X-ray monitors, including Fermi-GBM, Swift-BAT, SVOM-ECLAIRs, and Daksha, in the era of next-generation FRB detection facilities such as CHIME, DSA-2000, CHORD, and BURSTT. Our results highlight that highly sensitive X-ray monitors with large sky coverage, like Daksha, will provide the best opportunities to detect X-ray counterparts of bright FRBs.

Just less than 300 symbiotic stars are currently known in the Galaxy. The population synthesis methods predict that this amount should be 10--100 times larger. In recent years, several works have attempted to find symbiotic candidates from photometric surveys. Regular spectroscopic observations of these candidates can increase the number of known symbiotic systems. We aim to verify the symbiotic nature of 2MASS J21012803+4555377. Archive photometry and low-resolution spectra (R=1500-2000) of the candidate are presented. Besides molecular bands, the spectrum displays numerous emission lines including forbidden and high-ionization ones -- He II, [Fe VII], etc. A strong Raman-scattered O VI line is observed at 6825A. The source shows prominent excessive emission in the infrared related to a dense circumstellar dust shell. All this evidence indicates that 2MASS J21012803+4555377 should be classified as a D-type symbiotic star.

A debate persists regarding the correlation between the DIBs 9577 and 9632 Å, and whether they share a common molecular carrier (i.e., C$_{60}^{+}$). A robust high correlation determination emerges after bridging the baseline across an order of magnitude ($\simeq 50 - 700$ mÅ, $r=0.93\pm0.02$), and nearly doubling the important higher equivalent width domain by adding new Mg II-corrected sightlines. Moreover, additional evidence is presented of possible DIB linkages to fullerenes, whereby attention is drawn to DIBs at 7470.38, 7558.44, and 7581.47 Å, which match the Campbell experimental results for C$_{70}^{+}$ within 1 Å, and the same is true of 6926.48 and 7030.26 Å for C$_{70}^{2+}$. Yet their current correlation uncertainties are unsatisfactory and exacerbated by expectedly low EWs (e.g., $\overline{EW}=4$ mÅ for 6926.48 Å), and thus further observations are required to assess whether they represent a bona fide connection or numerical coincidence.

Aims. We examined the capabilities of methods based on the weak-field approximation and line bisectors to extract fast and reliable information about the height stratification of the magnetic field and line-of-sight velocities, respectively, from high spatial resolution observations of the Mg I b$_2$ line at 5173 Å. Methods. The Mg I b$_2$ line was analyzed alongside the Fe I 6173 Å line to help constrain the physical conditions of the photosphere. Additionally, we present the first high-resolution inversions of the Mg I b$_2$ line under nonlocal thermodynamic equilibrium (NLTE) conditions conducted over a large field of view using a full-Stokes multiline approach. To determine the optimal inversion strategy, we performed several tests on the Mg I b$_2$ line using the Fourier Transform Spectrometer atlas profile before applying it to our observations. Results. The good correlations between the traditional methods and the NLTE inversions indicate that the weak-field approximation is generally a reliable diagnostic tool at moderate field strengths for the rapid inference of the longitudinal magnetic field from the Mg I b$_2$ line. In contrast, line bisectors exhibit poorer correlations with the NLTE inferred plasma velocities, suggesting that they might not be suitable for deriving velocity gradients from the Mg I b$_2$ line. Furthermore, to accurately derive the thermodynamic properties of the solar atmosphere from this line, the more complex, and time-consuming, NLTE Stokes inversions are necessary. This work also provides observational evidence of the existence of low-lying canopies expanding above bright magnetic structures and pores near the low chromosphere.

The Mg I b$_2$ line at 5173 Å is primarily magnetically sensitive to heights between the mid photosphere and the low chromosphere, a region that has not been sufficiently explored in the solar atmosphere but is crucial for understanding the magnetic coupling between the two layers. New generation solar observatories are now performing polarimetric observations of this spectral line, enabling simultaneous measurements with multiple spectral lines. This allows for detailed studies of the magnetism around the temperature minimum region at high spatial, temporal, and spectral resolutions. We present a morphological classification of the Stokes $I$ and $V$ profiles of the Mg I b$_2$ line using the Euclidean distance method on high spatial resolution observations from the Swedish 1-m Solar Telescope. The physical properties of the resulting classes were analyzed using classical inference methods. Additionally, we present a two-line full-Stokes inversion of the representative profiles in which the Mg I b$_2$ line is treated fully under non-local thermodynamic equilibrium (NLTE) conditions, while the Fe I 6173 Å line is simultaneously inverted under LTE assumptions to provide photospheric constraints. This approach offers insights into the temperature stratification and other physical gradients involved in the formation of the different profile morphologies. We found nine classes of Stokes $V$ profiles and 16 classes of Stokes $I$ profiles in our Mg I b$_2$ dataset. These classes can be further grouped into families based on shared characteristics, physical properties, and location. Our classification provides important information on the different environments and processes occurring in the solar atmosphere around the temperature minimum region. It is also relevant for improving the performance of NLTE inversions.

We present a study of giant molecular cloud (GMC) properties in the Andromeda galaxy (M31) using CO(3-2) data from the James Clerk Maxwell Telescope (JCMT) in selected regions across the disc and in the nuclear ring, and comparing them with CO(1-0) observations from the IRAM 30m telescope in the same regions. We find that GMCs in the centre of M31 generally exhibit larger velocity dispersions ($\sigma$) and sizes ($R$) compared to those in the disc, while their average surface density ($\Sigma$) and turbulent pressure ($P_{\rm turb}$) are lower. This low turbulent pressure in the central region is primarily due to the low density of molecular gas. The estimated GMC properties depend on the choice of CO transitions. Compared to CO(1-0), CO(3-2) exhibits smaller velocity dispersion and equivalent radius but higher surface density. These differences highlight the distinct physical conditions probed by different molecular gas tracers. We estimate the virial parameter $\alpha_{\rm vir}\propto \sigma^2 R/\Sigma$ and find that most molecular clouds exhibit high values ($\alpha_{\rm vir} \sim 4-6$) for both CO transitions, indicating that they are unbound. Furthermore, clouds in the nuclear ring display even larger $\alpha_{\rm vir}$ values of $\lesssim 100$, suggesting that they may be highly dynamic, short-lived structures, although they could potentially achieve equilibrium under the external pressure exerted by the surrounding interstellar medium.

Molecular hydrogen (H$_2$) is by far the most abundant molecule in the Universe. However, due to the low emissivity of H$_2$, carbon monoxide (CO) is widely used instead to trace molecular gas in galaxies. The relative abundances of these molecules is expected to depend on both physical (e.g., density) and chemical (e.g., metal enrichment) properties of the gas, making direct measurements in diverse environments crucial. We present a systematic search for CO in absorption toward 34 stars behind H$_2$ gas in the Magellanic Clouds using the Hubble Space Telescope. We report the first two definitive detections of CO absorption in the Large Magellanic Cloud (LMC) and one in the Small Magellanic Cloud (SMC), along with stringent upper limits for the remaining sightlines. Non-detections of CO are consistent with models of low thermal pressures and/or low metallicities while detections at the lower metallicities of the Magellanic Clouds require higher thermal pressures, $P_{\rm th}=10^5-10^6$$\,$K$\,$cm$^{-3}$ than detections the Milky Way at similar $N({\rm H_2})$. Notably, the high density derived from the rotational excitation of CO towards SK$\,$143 in the SMC suggests full molecularization of CO in the absorbing cloud, with CO/H$_2 = 8.3^{+2.0}_{-1.6}\times10^{-5}$ consistent with the standard ratio ($3.2\times10^{-4}$) measured in dense molecular gas in the Milky Way, scaled to the SMC's $0.2\,Z_{\odot}$ metallicity.

We present analyses of Spitzer InfraRed Array Camera (IRAC) 3.6 $\mu$m and 4.5 $\mu$m phase curve observations of hot Jupiters WASP-77Ab and WASP-121b. For WASP-121b, we find amplitudes of 1771 $\pm$ 95 ppm (3.6 $\mu$m) and 2048 $\pm$ 109 ppm (4.5 $\mu$m), and near-zero offsets of -0.78 $\pm$ 1.87$^{\circ}$ (3.6 $\mu$m) and 0.42 $\pm$ 1.74$^{\circ}$ (4.5 $\mu$m), consistent within 2.2$\sigma$ and 1.3$\sigma$, respectively, with JWST NIRSpec results. For WASP-77Ab, we find amplitudes of 535 $\pm$ 52 ppm (3.6 $\mu$m) and 919 $\pm$ 40 ppm (4.5 $\mu$m), and offsets of 33.45 $\pm$ 2.79$^{\circ}$ (3.6 $\mu$m) and 16.28 $\pm$ 2.52$^{\circ}$ (4.5 $\mu$m). We report day- and nightside brightness temperatures: for WASP-121b, 2779 $\pm$ 40 K (3.6 $\mu$m) and 2905 $\pm$ 51 K (4.5 $\mu$m) (day) and 1259 $\pm$ 67 K (3.6 $\mu$m) and 1349 $\pm$ 54 K (4.5 $\mu$m) (night), and for WASP-77Ab, 1876 $\pm$ 23 K (3.6 $\mu$m) and 1780 $\pm$ 25 K (day) and 1501 $\pm$ 22 K (3.6 $\mu$m) and 1234 $\pm$ 20 K (4.5 $\mu$m) (night). Comparing WASP-121b data to general circulation models, we find evidence for drag inhibiting day-to-night heat transfer, which our model reproduces using magnetic circulation. Further, comparing both planets' data to Energy Balance Models, we show suppressed circulation in WASP-121b and potential evidence for an unusually high Bond albedo in WASP-77Ab. We add both planets to the Spitzer population study of previously identified trends in offset versus orbital period, finding that a positive trend is weakened, but not eliminated, by including these planets.

Inverse velocity dispersion (IVD) events, characterized by higher-energy particles arriving later than lower-energy particles, challenge the classical understanding of SEP events and are increasingly observed by spacecraft, such as Parker Solar Probe (PSP) and Solar Orbiter (SolO). However, the mechanisms underlying IVD events remain poorly understood. This study aims to investigate the physical processes responsible for long-duration IVD events by analyzing the SEP event observed by SolO on 2022 June 7. We explore the role of evolving shock connectivity, particle acceleration at interplanetary (IP) shocks, and cross-field transport in shaping the observed particle this http URL utilize data from Energetic Particle Detector (EPD) suite onboard SolO to analyze the characteristics of the IVD, and model the event using the Heliospheric Energetic Particle Acceleration and Transport (HEPAT) model. The IVD event exhibited a distinct and long-duration IVD signature, across proton energies from 1 to 20 MeV and lasting for approximately 10 hours. Simulations suggest that evolving shock connectivity and the evolution of shock play a primary role in the IVD signature, with SolO transitioning from shock flank to nose over time, resulting in a gradual increase in maximum particle energy along the field line. Furthermore, model results show that limited cross-field diffusion can influence both the nose energy and the duration of the IVD event. This study demonstrates that long-duration IVD events are primarily driven by evolving magnetic connectivity along a non-uniform shock that evolves over time, where the connection moves to more efficient acceleration sites as the shock propagates farther from the Sun. Other mechanisms, such as acceleration time at the shock, may also contribute to the observed IVD features.

We investigate helium accumulation on carbon-oxygen (CO) white dwarfs (WDs), exploring a broad parameter space of initial WD masses ($0.65$--$1.0M_{\odot}$) and helium accretion rates ($10^{-10}$--$10^{-4}M_{\odot}\text{yr}^{-1}$). Our simulations, which were allowed to run for up to the order of a Gyr, reveal distinct regimes determined by the given accretion rate: at higher rates ($\gtrsim10^{-5}M_\odot\rm yr^{-1}$), the mass is repelled by radiation pressure without accretion; intermediate rates ($\sim10^{-8}$--$10^{-5}M_{\odot}\text{yr}^{-1}$) produce periodically recurring helium nova eruptions, enabling gradual WD mass growth; and lower rates ($\lesssim 10^{-8}M_{\odot}\text{yr}^{-1}$) facilitate prolonged, uninterrupted helium accumulation, eventually triggering a thermonuclear runaway (TNR) which for some cases is at sub-Chandrasekhar masses, indicative of a type Ia supernova (SNe) ignition, i.e. providing a potential single-degenerate channel for sub-Chandra SNe. Our models indicate that the WD mass and the helium accumulation rate critically determine the ignition mass and TNR energetics. We identify compositional and thermal signatures characteristic of each regime, highlighting observational diagnostics relevant to helium-rich transients. We discuss these theoretical results in the context of the observed helium nova V445 Puppis, emphasizing helium accretion's pivotal role in shaping diverse thermonuclear phenomena.

Gas flows between galaxies and the CGM play a crucial role in galaxy evolution. When ionized by a quasar, these gas flows can be directly traced as giant nebulae. We present a study of a giant nebula around a radio-loud quasar, 3C$\,$57 at $z\approx0.672$. Observations from MUSE reveal that the nebula is elongated with a major axis of $70 \, \rm kpc$ and a minor axis of $40 \, \rm kpc$. The nebula displays an approximately symmetric blueshifted-redshifted pattern along the major axis and multi-component emission features in its $\rm[O\,II]$ and $\rm [O\,III]$ profiles. The morphology and kinematics can be explained as rotating gas or biconical outflow, both of which qualitatively reproduce the observed position-velocity diagram. The 3C$\,$57 nebula is significantly more kinematically disturbed, with $\rm W_{80}$ (the line width encompassing 80$\%$ of the flux) of approximately $300{-}400\,\rm km\,s^{-1}$, compared to $\rm H\,I$ gas in local early-type galaxies, which typically shows $\rm W_{80} \approx 50\,\rm km\,s^{-1}$. This velocity dispersion is comparable to the gas in cool-core clusters despite originating in a group 100 times less massive. For biconical outflow models, the inferred $10{-}20^{\circ}$ inclination angle is in tension with the unobscured nature of the quasar, as the dusty torus is expected to be perpendicular to the outflow. Neither a quiescent rotating gas origin nor a biconical outflow fully reproduces the observed kinematics and morphology of the 3C$\,$57 nebula, suggesting a more intricate origin likely involving both rotation and AGN feedback.

The total mass of a galaxy group, such as the Milky Way (MW) and the Andromeda Galaxy (M31), is usually determined from the kinematics of the satellites within their virial zones. Bahcall and Tremaine (1981) proposed the $v^2r$ estimator as an alternative to the virial theorem. We develop this approach by taking into account the three-dimensional distribution of satellites in the system to improve the reliability and accuracy of galaxy mass estimates. Applying this method to comprehensive dataset of Local Group satellites based on recent precise distance measurements, we estimate the total mass of MW of $(7.9 \pm 2.3) \times 10^{11}$ Msun and M31 of $(1.55 \pm 0.34) \times 10^{12}$ Msun. The capability of the method is limited by the distance measurement accuracy, making it extremely useful for the Local Group, but challenging for more distant systems.

We discovered four millisecond pulsars (MSPs) in searches of 80 $\gamma$-ray sources conducted from 2015 to 2017 with the Murriyang radio telescope of the Parkes Observatory. We provide an overview of the survey and focus on the results of a follow-up pulsar timing campaign. Using Fermi Large Area Telescope data, we have detected $\gamma$-ray pulsations from all four pulsars, and by combining radio and $\gamma$-ray data we obtain improved timing solutions. We also provide flux density distributions for the radio pulsars and flux-calibrated and phase-aligned radio and $\gamma$-ray pulse profiles. Some of the pulsars may be suitable for radio pulsar timing array experiments. PSR J0646-5455, PSR J1803-4719, and PSR J2045-6837 are in typical, nearly circular white dwarf binaries with residual eccentricities proportional to their binary periods. PSR J1833-3840 is a black widow pulsar with the longest known period, Pb = 0.9 d, and a very soft radio spectrum. PSR J0646-5455 has a strong, Vela-like $\gamma$-ray pulse profile and is suitable for inclusion in the $\gamma$-ray Pulsar Timing Array (GPTA). Despite this, it is possibly one of the lowest-efficiency $\gamma$-ray MSPs known. Indeed, all four new $\gamma$-ray MSPs have lower-than-average efficiency, a potential indication of bias in earlier searches. Finally, we retrospectively evaluate the efficiency of this survey: while only four new MSPs were directly discovered, subsequent campaigns have found pulsars in a further 19 of our targets, an excellent 30% efficiency.

We develop several aspects of the theory of gaseous astrophysical discs in which the gravity of the disc makes a significant contribution to its structure and dynamics. We show how the internal gravitational potential can be expanded in powers of the aspect ratio of the disc (or of a structure within it) and separated into near and far contributions. We analyse the hydrostatic vertical structure of a wide family of disc models, both analytically and numerically, and show that the near contribution to the internal gravitational potential energy can be written in an almost universal form in terms of the surface density and scaleheight. We thereby develop an affine model of the dynamics of (generally non-hydrostatic) self-gravitating discs in which this contribution to the energy acts as a gravitational pressure in the plane of the disc. This combines with and significantly reinforces the gas pressure, allowing us to define an enhanced effective sound speed and Toomre stability parameter Q for self-gravitating discs. We confirm that this theory fairly accurately reproduces the onset of axisymmetric gravitational instability in discs with resolved vertical structure. Among other things, this analysis shows that the critical wavelength is on the order of twenty times the scaleheight, helping to justify the validity of the affine model. The weakly nonlinear theory also typically exhibits subcritical behaviour, with equilibrium solutions of finite amplitude being found in the linearly stable regime Q > 1 for adiabatic exponents less than 1.50.

We report the discovery of two new magnetic cataclysmic variables with brown dwarf companions and long orbital periods ($P_{\rm orb}=95\pm1$ and $104\pm2$ min). This discovery increases the sample of candidate magnetic period bouncers with confirmed sub-stellar donors from four to six. We also find their X-ray luminosity from archival XMM-Newton observations to be in the range $L_{\rm X}\approx10^{28}$$-$$10^{29} \mathrm{erg\,s^{-1}}$ in the 0.25$-$10 keV band. This low luminosity is comparable with the other candidates, and at least an order of magnitude lower than the X-ray luminosities typically measured in cataclysmic variables. The X-ray fluxes imply mass transfer rates that are much lower than predicted by evolutionary models, even if some of the discrepancy is due to the accretion energy being emitted in other bands, such as via cyclotron emission at infrared wavelengths. Although it is possible that some or all of these systems formed directly as binaries containing a brown dwarf, it is likely that the donor used to be a low-mass star and that the systems followed the evolutionary track for cataclysmic variables, evolving past the period bounce. The donor in long period systems is expected to be a low-mass, cold brown dwarf. This hypothesis is supported by near-infrared photometric observations that constrain the donors in the two systems to be brown dwarfs cooler than $\approx$1100 K (spectral types T5 or later), most likely losing mass via Roche Lobe overflow or winds. The serendipitous discovery of two magnetic period bouncers in the small footprint of the XMM-Newton source catalog implies a large space density of these type of systems, possibly compatible with the prediction of 40$-$70 per cent of magnetic cataclysmic variables to be period bouncers.

The two moons of Mars, Phobos and Deimos, have orbits that are close to martian equator, indicating their formation from a circumplanetary disk. Phobos is currently migrating toward Mars due to tidal dissipation within the planet, and may be disrupted into a ring in few tens of Myr. The past evolution of Phobos is not fully understood, with one possibility being that Phobos formed in the early Solar System just interior to the synchronous orbit and migrated inward over several Gyr. Alternatively, Phobos may be the most recent product of an ongoing martian ring-moon cycle that lasted several Gyr but formed Phobos only 100 Myr ago at the fluid Roche limit. Here we use numerical integrations to simulate past evolution of Phobos in both of these scenarios and test whether Phobos's small eccentricity and inclination are consistent with either of these hypotheses. During its tidal evolution, Phobos crossed multiple resonances with both the rotation of Mars and the apparent motion of the Sun, requiring detailed numerical modeling of these dynamical events. Furthermore, Phobos crossed resonances with Deimos, which can affect the orbit of Deimos. We find that both the ancient Phobos hypothesis and the ring-moon cycle are fully consistent with the present orbit of Phobos, with no currently available means of distinguishing between these very different dynamical histories. Furthermore, we find that Deimos is affected by weak chaos caused by secular resonances with the planetary system, making the eccentricity of Deimos an ineffective constraint on the past migration of Phobos.

The Habitable Worlds Observatory (HWO) will enable a transformative leap in the direct imaging and characterization of Earth-like exoplanets. For this, NASA is focusing on early investment in technology development prior to mission definition and actively seeking international partnerships earlier than for previous missions. The "R&D for Space-Based HCI in Europe" workshop, held in March 2024 at Paris Observatory, convened leading experts in high-contrast imaging (HCI) to discuss European expertise and explore potential strategies for European contributions to HWO. This paper synthesizes the discussions and outcomes of the workshop, highlighting Europe's critical contributions to past and current HCI efforts, the synergies between ground- and space-based technologies, and the importance of laboratory testbeds and collaborative funding mechanisms. Key conclusions include the need for Europe to invest in technology development for areas such as deformable mirrors and advanced detectors, and establish or enhance laboratory facilities for system-level testing. Putting emphasis on the urgency of aligning with the timeline of the HWO, the participants called on an open affirmation by the European Space Agency (ESA) that a European contribution to HWO is clearly anticipated, to signal national agencies and unlock funding opportunities at the national level. Based on the expertise demonstrated through R&D, Europe is poised to play a pivotal role in advancing global HCI capabilities, contributing to the characterization of temperate exoplanets and fostering innovation across domains.

Ground-based high-resolution spectroscopy enables precise molecular detections, and velocity-resolved atmospheric dynamics, offering a distinct advantage over low-resolution methods for exoplanetary atmospheric studies. IGRINS-2, the successor to IGRINS, features improved throughput and enhanced sensitivity to carbon monoxide by shifting its $\textit{K}$-band coverage by ~36 nm to longer wavelengths. To evaluate its performance, we attempt to investigate the atmospheric characteristics of WASP-33 b. Observations were conducted on 2024 January 7 for a total of 2.43 hours; This includes 1.46 hours in the pre-eclipse phase to capture the planet's thermal emission spectrum. Our analysis, employing a composite atmospheric model, confirms the presence of a thermally inverted atmosphere on the planet's dayside with a signal-to-noise ratio (SNR) of 7.5. More specifically, we capture CO, H$_{2}$O, and OH with SNRs of 5.2, 4.2, and 4.4, respectively. These results are consistent with previous studies and demonstrate that IGRINS-2 is well-suited for detailed investigation of exoplanetary atmospheres. We anticipate that future observations with IGRINS-2 will further advance our understanding of exoplanetary atmospheres.

We investigate the Missing Baryon problem using Fast Radio Bursts (FRBs) to trace cosmic baryons. We use the CROCODILE simulations with the GADGET3/4-OSAKA SPH code, incorporating star formation, supernova (SN), and active galactic nuclei (AGN) feedback. Light cones generated from large-scale structure simulations allow us to compute gas density profiles and dispersion measures (DMs) measurable by FRBs. Our results show that AGN feedback reduces central gas densities in halos, reshaping the boundary between the circumgalactic medium (CGM) and intergalactic medium (IGM). Zoom-in simulations further reveal that AGN feedback significantly modulates foreground halo DM contributions along different sightlines. By analyzing the DM--redshift (DM--z) relation and comparing it to the Macquart relation, we constrain the diffuse baryon mass fraction at z = 1 to fdiff = 0.865 (+0.101, -0.165) (fiducial) and fdiff = 0.856 (+0.101, -0.162) (NoBH), including IGM (fIGM) and halo (fHalos) contributions. We also quantify the redshift evolution of fdiff and fIGM, providing the fitting results. Our study provides a framework for understanding baryon distribution across cosmic structures, FRB host galaxies, and the role of AGN in shaping foreground DM contributions.

We study the effect of stellar evolution on the dispersal of protoplanatary disks by performing one-dimensional simulations of long-term disk evolution. Our simulations include viscous disk accretion, magnetohydrodynamic winds, and photoevaporation as important disk dispersal processes. We consider a wide range of stellar mass of $0.1$ - $7M_{\odot}$, and incorporate the luminosity evolution of the central star. For solar-mass stars, stellar evolution delays the disk dispersal time as the FUV luminosity decreases toward the main sequence. In the case of intermediate-mass stars, the FUV luminosity increases significantly over a few million years, driving strong photoevaporation and enhancing disk mass loss during the later stages of disk evolution. This highlights the limitations of assuming a constant FUV luminosity throughout a simulation. Photoevaporation primarily impacts the outer regions of the disk and is the dominant disk dispersal process in the late evolutionary stage. Based on the results of a large set of simulations, we study the evolution of a population of star-disk systems and derive the disk fraction as a function of time. We demonstrate that the inclusion of stellar luminosity evolution can alter the disk fraction by several tens of percent, bringing the simulations into closer agreement with recent observations. We argue that it is important to include the stellar luminosity evolution in simulations of the long-term dispersal of protoplanetary disks.

We present the ultraviolet, optical and infrared counterparts of 128 galaxies detected in neutral hydrogen (HI) in the FAST Ultra-Deep Survey (FUDS) field 0 (FUDS0). HI mass upper limits are also calculated for 134 non-detections in the field. Stellar masses ($M_*$), star formation rates (SFRs) and star formation histories are computed by fitting spectral energy distributions (SEDs) using ProSpect. The results show that HI-selected galaxies prefer recent long-lasting, but mild star formation activity, while HI non-detections have earlier and more intense star formation activity. Based on their distribution on the SFR versus $M_*$ diagram, the typical evolution of HI-selected galaxies follows three distinct stages: (i) Early stage: the total SFR increases, though the specific SFR (sSFR) decreases from 10$^{-8}$ to 10$^{-9}$ yr$^{-1}$; (ii) Mass accumulation stage: the SFR is steady, and stellar mass increase linearly with time; (iii) Quenching stage: star formation activity quenches on a rapid timescale and at constant stellar mass. 37 non-detections are located on star-forming main sequence, but are not detected in HI due to low sensitivity close to field edges or close to strong radio frequency interference. Comparisons with the existing optical, optically-selected HI, and HI catalogs show a good agreement with respect to measured $M_*$ and SFR, with minor discrepancies due to selection effects. The ongoing full FUDS survey will help us better explore the evolutionary stages of HI galaxies through a larger sample.

We present a catalog of 927 low-mass active galactic nuclei (AGNs) with black hole mass of $M_{BH}\leqslant2\times10^{6} M_{\odot}$ characterized by broad H$\alpha$ or H$\beta$ emission lines,uniformly selected from the Seventeenth Data Release (DR17) of the Sloan Digital Sky Survey (SDSS) spectra. Taking advantages of the wide wavelength coverage of BOSS/eBOSS spectra of the SDSS, this sample significantly extends the redshift range to $z\leqslant0.57$, a marked improvement over the previous studies which were generally limited to $z\leqslant0.35$. This sample encompasses black hole masses from $10^{3.7}$ to $10^{6.3} M_{\odot}$, with Eddington ratios ranging from 0.01 to 3.3. Preliminary analysis of this sample reveals a marked decline in maximum accretion rates (namely $L/L_{Edd}$) and broad-H$\alpha$ luminosities with decreasing redshift, analogous to the passive ``downsizing'' evolutionary trend observed in high-mass AGNs. This systematic catalog of low-redshift low-mass AGNs, the largest so far, will benefit the studies on accretion physics, AGN--galaxy connection and the origin of supermassive black holes.

We study the stellar mass-gas metallicity relation (MZR) which shows a significant scatter for a fixed stellar mass. By defining global environments, nodes, filaments, and voids within the Horizon Run 5 cosmological hydrodynamical simulation, we explore when and where the enrichment of galaxies occurs, analysing key evolution parameters such as star-formation rate and changes in gas-fraction and gas-metallicity per unit time. At high redshift ($z>4.5$), there are minimal deviations from the MZR due to environment, however, larger deviations emerge as redshift decreases. Low stellar mass galaxies in nodes, $M_{\star} < 10^{9.8}\,\text{M}_{\odot}$, start showing deviations at $z = 3.5$, whilst other environments do not. For, $z < 2$, filaments and voids begin to show deviations above and below the MZR, respectively. By $z = 0.625$, the last epoch of HR5, deviations exist for all stellar masses and environments, with a maximum value of 0.13 dex at $M_{\star} \approx 10^{9.35}\,\text{M}_{\odot}$, between the median gas metallicities of node and void galaxies. To explain this environmental variance we discuss gas accretion, AGN, ram-pressure-stripping and strangulation as regulators of $Z_{g}$. Concurrently, at high metallicities, for $z < 2$, while massive galaxies in nodes show increasing $Z_{g}$ and decreasing [O/Fe], void galaxies show a turnover where $Z_{g}$ falls with decreasing [O/Fe]. This directly points to the importance of cold-gas accretion in retaining lower $Z_{g}$ in massive void galaxies for $z < 2$, whilst its absence in nodes allowed $Z_{g}$ to access higher values.

Recent observational analyses have revealed a significant tension in the growth index $\gamma$, which characterizes the growth rate of cosmic structures. Specifically, when treating $\gamma$ as a free parameter within $\Lambda$CDM framework, a combination of Planck and $ f\sigma_8 $ data yields $\gamma \approx 0.64$, in $\sim4\sigma$ tension with the theoretically expected value $\gamma \approx 0.55$ (assuming general relativity). This discrepancy, closely related to the $ S_8 $ tension, poses a new challenge to the standard cosmological model by suggesting that it predicts an excessive growth of structure. In this work, we demonstrate that the $\Lambda_{\rm s}$CDM framework (featuring a rapid sign-switching cosmological constant (mirror AdS-to-dS transition) in the late universe at redshift $ z_\dagger \sim 2 $) can simultaneously alleviate the $ \gamma $, $ H_0 $, and $ S_8 $ tensions. We also examined a scenario with fixed $ z_\dagger = 1.7 $, previously identified as a sweet spot for alleviating multiple major cosmological tensions (including those in $ H_0 $, $ M_B $, and $ S_8 $) finding that it completely eliminates both the $ \gamma $ and $ H_0 $ tensions, although it is statistically disfavored by our dataset combinations. Our findings suggest that $\Lambda_{\rm s}$CDM is a promising model, %alternative to $\Lambda$CDM, providing a potential unified resolution to multiple major cosmological tensions.

Aims. We introduce the SISSI (Supernovae In a Stratified, Shearing Interstellar medium) simulation suite, which aims to enable a more comprehensive understanding of supernova remnants (SNRs) evolving in a complex interstellar medium (ISM) structured under the influence of galactic rotation, gravity and turbulence. Methods. We utilize zoom-in simulations of 30 SNRs expanding in the ISM of a simulated isolated disk galaxy. The ISM of the galaxy is resolved down to a maximum resolution of $\sim 12\,\text{pc}$, while we achieve a zoomed-in resolution of $\sim 0.18\, \text{pc}$ in the vicinity of the explosion sources. We compute the time-evolution of the SNRs' geometry and compare it to the observed geometry of the Local Bubble. Results. During the early stages of evolution, SNRs are well described by existing analytical models. On longer timescales, starting at about a percent of the orbital timescale, they depart from spherical symmetry and become increasingly prolate or oblate. The timescale for the departure from spherical symmetry is shorter than the expectation from a simple model for the deformation by galactic shear, suggesting that galactic shear alone cannot explain these differences. Yet, the alignment of the minor- and major axis of the SNRs is in line with expectations from said model, indicating that the deformation might have a shear-related origin. A comparison with the geometry of the Local Bubble reveals that it might be slightly younger than previously believed, but otherwise has a standard morphology for a SNR of its age and size. Conclusions. Studying the geometry of SNRs can reveal valuable insights about the complex interactions shaping their dynamical evolution. Future studies targeting the geometry of Galactic SNRs may use this insight to obtain a clearer picture of the processes shaping the Galactic ISM.

SN 2023ixf is one of the brightest Core Collapse Supernovae of the 21st century and offers a rare opportunity to investigate the late stage of a Supernova through nebular phase spectroscopy. We present four nebular phase spectra from day +291 to +413 after explosion. This is supplemented with high cadence early phase spectroscopic observations and photometry covering the first 500 days to investigate explosion parameters. The narrow and blue-shifted nebular Oxygen emission lines are used to infer an ejected Oxygen mass of $<0.65M_\odot$, consistent with models of a relatively low mass ($M_{ZAMS}<15M_\odot$) progenitor. An energy of 0.3 to $1.4 \times10^{51}$ erg and a light curve powered by an initial $^{56}$Ni mass of $0.049 \pm 0.005 M_\odot$ appear consistent with a relatively standard Type II explosion, while an incomplete $\gamma$-ray trapping (with timescale of $240\pm4$ days) suggests a lower ejecta mass. Assuming a typical explosion, the broad Hydrogen and Calcium profiles suggest a common origin within a lower mass, partially stripped envelope. Hydrogen emission broadens with time, indicating contribution from an additional power source at an extended distance; while the emergence of high velocity ($\sim$6,000 km s$^{-1}$) Hydrogen emission features (beginning around day +200) may be explained by Shock Interaction with a dense Hydrogen-rich region located at $\sim1.5 \times 10^{16}$cm. Such envelope mass loss for a low mass progenitor may be explained through theoretical models of Binary interaction.

Thermonuclear explosions of carbon-oxygen white dwarfs as Type Ia supernovae (SNe Ia) play a significant role in the galactic chemical evolution (GCE) of the Milky Way. However, a long-standing and as yet unresolved problem of modern astrophysics concerns the identity of their progenitor. We aim to use GCE predictions to help constrain potential SN Ia progenitor scenarios, since it is well known that SN Ia nucleosynthesis yields, in particular the Fe-peak elements, depend on the explosion mechanism. We calculated 1140 GCE models and compared the GCE-predicted abundance ratios for four different SN Ia explosion mechanisms -- two from sub-Chandrasekhar (MCh) mass progenitors and two from near-MCh mass progenitors -- to spectroscopic measurements of Milky Way disk stars, considering both local thermodynamic equilibrium (LTE) and non-LTE (NLTE) assumptions. We calibrated the GCE framework for two sets of massive star yields in order to assess how stellar modelling uncertainties affect the relative contribution from core-collapse supernovae (CCSNe) towards Si, Ca, and the Fe-peak elements. From a GCE perspective, Si and Ca cannot be used to constrain SN Ia progenitors since there is little variation in their yields between different explosion types. The GCE of [Ti/Fe] and [Co/Fe] are not reproduced by any combination of yields. The [Cr/Fe] ratio is also problematic, since hardly any NLTE data of the disk are available and there are conflicting yields from CCSNe. For [Mn/Fe], neither CCSN yield set are compatible with the NLTE data. For [Ni/Fe], the NLTE data are well fit by one set of CCSN yields, with the best-fitting GCE models having a $\sim85\%$ contribution from sub-MCh SNe Ia. We advise caution when using GCE models to constrain the Galaxy's SN Ia population, since the results depend on both the choice of CCSN yields and the elemental ratio used as a diagnostic.

Context: Studying the internal kinematics of galaxies provides insights into their past evolution, current dynamics, and future trajectory. The Large Magellanic Cloud (LMC), as the largest and one of the nearest satellite galaxies of the Milky Way, presents unique opportunities to investigate these phenomena in great detail. Aims: We investigate the internal kinematics of the LMC by deriving precise stellar proper motions using data from the VISTA survey of the Magellanic Clouds system (VMC). The main objective is to refine the LMC's dynamical parameters using improved proper motion measurements including one additional epoch of VISTA observations which extended the time baseline from ~ 2 to 10 years. Methods: The precision of the proper motion was significantly enhanced, reducing uncertainties from 6 mas/yr to 1.5 mas/yr. We derived geometrical and kinematic parameters, generating velocity maps and rotation curves, for both young and old stellar populations. Finally, we compared a suite of dynamical models, which simulate the interaction of the LMC with the Milky Way and Small Magellanic Cloud (SMC), against the observations. Results: The tangential rotation curve reveals an asymmetric drift between young and old stars, while the radial velocity curve for the young population shows an increasing trend within the inner bar region, suggesting non-circular orbits. We confirm the clockwise rotation around the dynamical centre of the LMC, consistent with previous predictions. A significant residual motion was detected toward the north-east of the LMC, directed away from the centre. This feature observed in the inner disk region is kinematically connected with a substructure identified in the periphery known as Eastern Substructure 1. This motion suggests a possible tidal influence from the Milky Way, combined with the effects of the recent close pericentre passage of the SMC ~150 Myr ago.

Ongoing and upcoming wide-field surveys at different wavelengths will measure the distribution of galaxy clusters with unprecedented precision, demanding accurate models for the two-point correlation function (2PCF) covariance. In this work, we assess a semi-analytical framework for the cluster 2PCF covariance that employs three nuisance parameters to account for non-Poissonian shot noise, residual uncertainties in the halo bias model, and subleading noise terms. We calibrate these parameters on a suite of fast approximate simulations generated by PINOCCHIO as well as full $N$-body simulations from OpenGADGET3. We demonstrate that PINOCCHIO can reproduce the 2PCF covariance measured in OpenGADGET3 at the few percent level, provided the mass functions are carefully rescaled. Resolution tests confirm that high particle counts are necessary to capture shot-noise corrections, especially at high redshifts. We perform the parameter calibration across multiple cosmological models, showing that one of the nuisance parameters, the non-Poissonian shot-noise correction $\alpha$, depends mildly on the amplitude of matter fluctuations $\sigma_8$. In contrast, the remaining two parameters, $\beta$ controlling the bias correction and $\gamma$ controlling the secondary shot-noise correction, exhibit more significant variation with redshift and halo mass. Overall, our results underscore the importance of calibrating covariance models on realistic mock catalogs that replicate the selection function of forthcoming surveys and highlight that approximate methods, when properly tuned, can effectively complement full $N$-body simulations for precision cluster cosmology.

The star-forming region N66, as a host of the majority of OB stars in the Small Magellanic Cloud, provides a unique opportunity to enhance our understanding of the triggers of high-mass star formation. We investigate the properties of the molecular cloud in N66 using the $^{12}$CO(1-0) data obtained with the Atacama Large Millimeter/submillimeter Array. A cloud decomposition analysis identified 165 independent cloud structures and substructures. The size-linewidth scaling relation for the entire region exhibits an index of 0.49, indicating that the region is in a state of virial equilibrium. In contrast, a detailed analysis of the central N66 region revealed a size-linewidth scaling relation with an index of 0.75, suggesting that distinct factors are influencing the dynamics of this central area. Averaging the spectra in the central N66 region revealed three distinct velocity peaks at 145, 152, and 160 $\mathrm{km \, s^{-1}}$, indicating that some kinds of interactions are occurring within the cloud. The analysis of the position-velocity diagrams in the central region revealed a ring-like structure, indicating the presence of an expanding bubble. The bubble exhibits supersonic characteristics, with an expansion velocity of $v_{\mathrm{exp}} \approx 11$ $\mathrm{km \, s^{-1}}$, and an overall systemic velocity of $v_{\mathrm{sys}}\approx $ 151 $\mathrm{km \, s^{-1}}$. The radius is estimated to be in the range of $r \approx [9.8 - 12.9] \pm 0.5$ pc and is approximately 1.2 Myr old.

We report the discovery of the young B6V run-away star LAMOST J083323.18+430825.4, 2.5\,kpc above the Galactic plane. Its atmospheric parameters and chemical composition are determined from LAMOST spectra, indicating normal composition. Effective temperature (Teff=14,500) and gravity (log g=3.79) suggest that the star is close to terminating hydrogen burning. An analysis of the spectral energy distribution allowed us to determine the angular diameter as well as the interstellar reddening. Using evolutionary models from the MIST database we derived the stellar mass (4.75Msun) and age (104^+11_-13 Myr). The spectroscopic distance (4.17 kpc), the radius (4.5 Rsun), and the luminosity (log(L/Lsun)=2.89) then result from the atmospheric parameters. Using Gaia proper motions, the trajectory is traced back to the Galactic disk to identify the place of birth in a spiral arm. The ejection velocity of 92 km s^{-1} is typical for runaway stars in the halo. The age of the star is larger than its time of flight (78+-4 Myr), which favors a binary supernova event as the likely ejection mechanism. The TESS light curve shows variations with a period of 3.58 days from which we conclude that it is a slowly pulsating B-star, one of very few run-away B-stars known to pulsate.

IceCube-Gen2 is a proposed extension to the existing IceCube Neutrino Observatory at the South Pole. It will consist of three components: an in-ice optical array, a surface array on top of the optical array, and a radio array for detecting ultra-high energy neutrinos. Here we study the sensitivity of this future detector to the mass separation of primary cosmic rays, using CORSIKA Monte Carlo simulations of extensive air showers initiated by H, He, O and Fe primaries. The surface array will use two types of detection technologies: scintillation detectors and radio antennas; the latter are not considered in this study. A set of mass-sensitive variables are investigated utilizing both the scintillators of the surface array and the full optical in-ice array. Among these, the high-energy muons measurable by the in-ice array are found to have the highest mass separation power for showers for which the cosmic-ray energy is known, e.g. from the surface array.

Context. In Class 0/I and the outskirts of Class II circumstellar discs, the self-gravity of gas significantly affects the disc's vertical hydrostatic equilibrium. The contribution of dust, whose measured mass is still uncertain, could influence this equilibrium. Aims. We aim to formulate and solve approximately the equations governing the hydrostatic equilibrium of a self-gravitating disc composed of gas and dust. Particularly, we aim to provide a fully consistent treatment of turbulence and gravity, affecting almost symmetrically gas and dust. Observationally, we study the possibility of indirectly measuring disc masses through gas layering and dust settling measurements. Methods. We used analytical methods to approximate the solution of the 1D Liouville equation with additional non-linearities governing the stratification of a self-gravitating protoplanetary disc. The findings were verified numerically and validated through physical interpretation. Results. For a constant vertical stopping time profile, we discovered a nearly exact layering solution valid across all self-gravity regimes for gas and dust. From first principles, we defined the Toomre parameter of a bi-fluid system as the harmonic average of its constituents' Toomre parameters. Based on these findings, we propose a method to estimate disc mass through gas or dust settling observations. We introduce a generic definition of the dust-to-gas scale height, applicable to complex profiles. We also identified new exact solutions for benchmarking self-gravity solvers in numerical codes. Conclusions. The hydrostatic equilibrium of a gas/dust mixture is governed by their Toomre parameters and effective relative temperature. This equilibrium could be used for measuring disc masses, improving our understanding of disc settling and gravitational collapse, and enhancing the computation of self-gravity in thin disc simulations.

The Tayler instability of an azimuthal magnetic field with one or two ``rings'' along the radius is studied for an axially unbounded Taylor-Couette flow. The rotation law of the conducting fluid is a quasi-Keplerian one. Without rotation all toroidal fields are the more destabilized the more the radial profiles differ from the uniformity. For medium Reynolds numbers of rotation, however, the behaviour of the lines of neutral stability strongly depend on the magnetic Prandtl number. For Pm=1 the differential rotation matches the instability lines of azimuthal fields with and without rings so that the maximally possible Reynolds numbers for fields with smooth radial profiles and such with rings do hardly differ. The magnetic Mach number of the considered examples are of the astrophysically relevant order of magnitude between ten and twenty. The nonaxisymmetric instability fluctuations form a weak alpha effect of the mean-field electrodynamics which always changes its sign between the walls independent of the Reynolds number, magnetic Prandtl number or the radial profile of the magnetic background field. The resulting dynamo modes work on a similar axial scale as the Tayler instability, hence they are small-scale dynamos. The fields are axially drifting with high phase velocity where at certain periods the azimuthal fields with one-ring geometry develop to fields with two rings along the radius. It is still open whether and how a nonlinear dynamo model may overcome this puzzling complication.

During September 2023 the Alice ultraviolet spectrograph on the New Horizons (NH) spacecraft was used to map diffuse Lyman alpha (Lya) emission over most of the sky, at a range of 56.9 AU from the Sun. At that distance, models predict that the interplanetary medium Lya emissions result from comparable amounts of resonant backscattering of the solar Lya line by interstellar hydrogen atoms (HI) passing through the solar system, in addition to an approximately isotropic background of 30-70 R from the Local InterStellar Medium (LISM). The NH observations show no strong correlations with nearby cloud structures of the LISM or with expected structures of the heliosphere, such as a hydrogen wall associated with the heliopause. To explain the relatively bright and uniform Lya of the LISM we propose that hot, young stars within the Local Hot Bubble (LHB) shine on its interior walls, photoionizing HI atoms there. Recombination of these ions can account for the observed 50 R Lya background, after amplification of the diffuse Lya by resonant scattering, although sophisticated (i.e., 3-D) radiative transfer models should be used to confirm this conjecture. Future observations of the diffuse Lya, with instruments capable of resolving the line profile, could provide a new window on HI populations in the LISM and heliosphere. The NH Alice all-sky Lya observations presented here may be repeated at some point in the future, if resources allow, and the two maps could be combined to provide a significant increase in angular resolution.

In this work, we present OLÉ, a new online learning emulator for use in cosmological inference. The emulator relies on Gaussian Processes and Principal Component Analysis for efficient data compression and fast evaluation. Moreover, OLÉ features an automatic error estimation for optimal active sampling and online learning. All training data is computed on-the-fly, making the emulator applicable to any cosmological model or dataset. We illustrate the emulator's performance on an array of cosmological models and data sets, showing significant improvements in efficiency over similar emulators without degrading accuracy compared to standard theory codes. We find that OLÉ is able to considerably speed up the inference process, increasing the efficiency by a factor of $30-350$, including data acquisition and training. Typically the runtime of the likelihood code becomes the computational bottleneck. Furthermore, OLÉ emulators are differentiable; we demonstrate that, together with the differentiable likelihoods available in the $\texttt{candl}$ library, we can construct a gradient-based sampling method which yields an additional improvement factor of 4. OLÉ can be easily interfaced with the popular samplers $\texttt{MontePython}$ and $\texttt{Cobaya}$, and the Einstein-Boltzmann solvers $\texttt{CLASS}$ and $\texttt{CAMB}$. OLÉ is publicly available at this https URL .

In light of the evidence for dynamical dark energy (DE) found from the most recent Dark Energy Spectroscopic Instrument (DESI) baryon acoustic oscillation (BAO) measurements, we perform a non-parametric, model-independent reconstruction of the DE density evolution. To do so, we develop and validate a new framework that reconstructs the DE density through a third-degree piece-wise polynomial interpolation, allowing for direct constraints on its redshift evolution without assuming any specific functional form. The strength of our approach resides in the choice of directly reconstructing the DE density, which provides a more straightforward relation to the distances measured by BAO than the equation of state parameter. We investigate the constraining power of cosmic microwave background (CMB) observations combined with supernovae (SNe) and BAO measurements. In agreement with results from other works, we find a preference for deviations from $\Lambda$CDM, with a significance of $2.4\sigma$ when using the Dark Energy Survey Year 5 (DESY5) SNe data, and $1.3\sigma$ with PantheonPlus. In all the cases we consider, the derived DE equation of state parameter presents evidence for phantom crossing. By investigating potential systematic effects in the low-redshift samples of DESY5 observations, we confirm that correcting for the offset in apparent magnitude with respect to PantheonPlus data, as suggested in previous studies, completely removes the tension. Furthermore, we assess the risk of potentially overfitting the data by changing the number of interpolation nodes. As expected, we find that with lesser nodes we get a smoother reconstructed behavior of the DE density, although with similar overall features. The pipeline developed in this work is ready to be used with future high-precision data to further investigate the evidence for a non-standard background evolution.

Fast radio bursts (FRBs) are energetic, short-duration radio pulses of unclear origins. In this study, we investigate the FRBs and pulsars with broad energy distributions by fitting their high energy tails with a power-law model. Two cosmological repeating FRBs (FRB 20201124A and FRB 20220912A), one nearby FRB (FRB 20200120E), and two pulsars (RRATs J1846-0257 and J1854+0306), exhibit power-law indices of $\alpha \gtrsim -1$, suggesting that their bright pulses contribute significantly to the total radio pulse energy. The brightest bursts from these sources fit well with a simple power-law model ($\alpha = -0.26 \pm 0.05$), indicating a tentative link between certain high-luminosity FRBs and low-luminosity radio bursts. We also discuss detailed survey strategies for FAST, MeerKAT and Parkes cryoPAF in the search for FRBs in nearby globular clusters (GCs) using different power-law indices, recommending targets for observation. We suggest that combining observations with FAST ($\sim$ 3 hours) and Parkes cryoPAF (10-20 hours) are practicable for discovering new FRBs in the nearby GCs.

Determining the mass of the neutron stars (NSs) accurately improves our understanding of the NS interior and complicated binary evolution. However, the masses of the systems are degenerate with orbital inclination angle when using solely gravitational waves (GWs) or electromagnetic measurements, especially for face-on binaries. Taking advantages of both GWs and optical observations for LISA neutron-star white-dwarf (NS-WD) binaries, we propose a mass determination method utilising multi-messenger observational information. By combining the binary mass function obtained from optical observations and a GW mass function, that we introduce, derived from GW observations, we demonstrate how we can set improved constraints on the NS mass and break the degeneracy in the mass and viewing inclination determination. We further comment on the universal relation of the error bar of the GW mass function versus GW signal-to-noise ratio (SNR), and propose a simple method for the estimate of capability of GW observations on mass determination with {LISA}. We show that for ultra-compact NS-WD binaries within our Galaxy, the mass of the NS can be constrained to within an accuracy of +- 0.2 \solarmass with the proposed method.

With the imminent data releases from next-generation spectroscopic surveys, hundreds of thousands of white dwarf spectra are expected to become available within the next few years, increasing the data volume by an order of magnitude. This surge in data has created a pressing need for automated tools to efficiently analyze and classify these spectra. Although machine learning algorithms have recently been applied to classify large spectroscopic datasets, they remain constrained by the limited availability of training data. The Sloan Digital Sky Survey (SDSS) serves as the current standard training set, as it provides the largest collection of labeled spectra; however, it faces challenges related to severe class imbalance and uncertain label consistency across different surveys. In this work, we address these limitations by training histogram gradient-boosted classifiers on a synthetic SDSS dataset to identify six ubiquitous chemical signatures in the atmosphere of white dwarfs, and test them on 14,246 objects with SNR$>$10 SDSS spectroscopy. We show our approach not only surpasses human expert performance, but also enables subtype classification and effectively resolves label transferability issues. The methodology developed here is adaptable to any spectroscopic survey, providing a critical tool for the astronomical community.

Aims. We investigate the role of cosmic ray (CR) halos in shaping the properties of starburst-driven galactic outflows. Methods. We develop a microphysical model for galactic outflows driven by a continuous central feedback source, incorporating a simplified treatment of CRs. The model parameters are linked to the effective properties of a starburst. By analyzing its asymptotic behavior, we derive a criterion for launching starburst-driven galactic outflows and determine the corresponding outflow velocities. Results. We find that in the absence of CRs, galactic outflows can only be launched if the star-formation rate (SFR) surface density exceeds a critical threshold proportional to the dynamical equilibrium pressure. In contrast, CRs can always drive slow outflows. CRs dominate in systems with SFR surface densities below the critical threshold but become negligible in highly star-forming systems. However, in older systems with established CR halos, the CR contribution to outflows diminishes once the outflow reaches the galactic scale height, rendering CRs ineffective in sustaining outflows in such systems. Conclusions. Over cosmic time, galaxies accumulate relic CRs in their halos, providing additional non-thermal pressure support that suppresses low-velocity CR-driven outflows. We predict that such low-velocity outflows are expected only in young systems that have not yet built up significant CR halos. In contrast, fast outflows in starburst galaxies, where the SFR surface density exceeds the critical threshold, are primarily driven by momentum injection and remain largely unaffected by CR halos.

Neural network emulators are widely used in astrophysics and cosmology to approximate complex simulations inside Bayesian inference loops. Ad hoc rules of thumb are often used to justify the emulator accuracy required for reliable posterior recovery. We provide a theoretically motivated limit on the maximum amount of incorrect information inferred by using an emulator with a given accuracy. Under assumptions of linearity in the model, uncorrelated noise in the data and a Gaussian likelihood function, we demonstrate that the difference between the true underlying posterior and the recovered posterior can be quantified via a Kullback-Leibler divergence. We demonstrate how this limit can be used in the field of 21-cm cosmology by comparing the posteriors recovered when fitting mock data sets generated with the 1D radiative transfer code ARES directly with the simulation code and separately with an emulator. This paper is partly in response to and builds upon recent discussions in the literature which call into question the use of emulators in Bayesian inference pipelines. Upon repeating some aspects of these analyses, we find these concerns quantitatively unjustified, with accurate posterior recovery possible even when the mean RMSE error for the emulator is approximately 20% of the magnitude of the noise in the data. For the purposes of community reproducibility, we make our analysis code public at this link this https URL.

The Pleiades is a young open cluster that has not yet dynamically relaxed, making it an ideal target to observe various internal dynamical effects. By employing a well-defined sample of main-sequence (MS) cluster members, including both MS single stars and unresolved MS+MS binaries, we revisited their individual masses and mass functions and quantified the mass dependence of their radial distributions. We found that the mass function of binaries is more top-heavy than that of single stars. Significant mass segregation is observed for both single and binary populations respectively, with more massive objects concentrated towards the cluster center. Notably, within given mass ranges, binaries are distributed more scattered than single stars, providing direct evidence for more efficient dynamical disruption of binaries in the inner region. The radial distribution of the binary fraction, expressed as the $f_{\rm b}-R$ relation can be characterized by a bimodal shape, with higher $f_{\rm b}$ values in both innermost and outermost regions of the cluster. The lower-mass subsample exhibits a monotonic increase in $f_{\rm b}$ with radius, reflecting the impact of binary disruption. Conversely, for the higher-mass subsample, $f_{\rm b}$ decreases with radius. It can be explained that these massive cluster members, which possess higher binary probabilities, have already undergone significant mass segregation. All these observational evidence and analyses related to the radial mass distribution imply that the Pleiades is currently undergoing a complicated interplay of various internal dynamical effects, of which the modulation between mass segregation and binary disruption is particularly pronounced.

Measurements of the GD-1 star stream velocity distribution within $\pm$3 degrees of the centerline find a total line of sight velocity spread of 5-6 km/s in the well measured $\phi_1=$ [-30, 0] region (Valluri25). The velocity spread is far above the $\sim$2-3 km/s of a dissolved globular cluster in a smooth galactic potential. The dynamical heating of the GD-1 star stream is simulated in an evolving model Milky Way potential which includes the subhalos extracted from cosmological CDM and WDM Milky Way-like halos. The model bridges fully cosmological Milky Way-like halos and late time static Milky Way potentials allowing individual streams to be accurately integrated. An evolving CDM subhalo population acting for $\sim$11 Gyr heats GD-1 to 6.2 km/s. The WDM (7 keV and lighter) models develop a velocity dispersion of 3.9 km/s, only slightly greater than the 3.5 km/s in an evolving smooth halo without subhalos for 11 Gyr. The dynamical age of the best model stream is close to the isochrone age of the stars in the stream. Subhalos with masses in the decade around $10^{7.5} M_\odot$, below the mass range of dwarf galaxies, dominate the dynamical stream heating.

We present the first comprehensive theoretical predictions of radio emission from a Type Ic-BL supernova (SN) associated with a gamma-ray burst (GRB) jet. It is naturally supposed that the expected radio light curve consists of two components of emitting source: radio emission from a non-relativistic SN shock and afterglow emitted from the head of the relativistic GRB jet. We calculate each component of radio emission, placing an emphasis on surveying wide ranges of isotropic explosion energy and viewing angle in our GRB afterglow modeling. We show that in particular parameter space, the composite radio light curve would be characterized by a double-peaked shape. The condition for the clear appearance of the double-peaked radio light curve is either (1) the isotropic explosion energy is small (low-luminosity GRB) or (2) the viewing angle is large (off-axis GRB). Our results highlight that follow-up radio observations conducted within a few years after the optical discovery of nearby Type Ic-BL supernovae ($\sim$100~Mpc) can serve as a unique diagnostic for off-axis GRBs undiscovered in Type IcBL SNe. This will be a step toward uncovering the nature of long GRB progenitors and clarifying their connection to Type IcBL SNe.

Coronagraph observations provide key information about the orientation of the Sun's magnetic field. Previous studies used quasi-radial features detected in coronagraph images to improve coronal magnetic field models by comparing the orientation of the features to the projected orientation of the model field. Various algorithms segment these coronal features to approximate the local plane-of-sky geometry of the coronal magnetic field, and their orientation can be used as input for optimizing and constraining coronal magnetic field models. We present a new framework that allows for further quantitative evaluations of image-based coronal segmentation methods against magnetic field models, and vice-versa. We compare quasi-radial features identified from QRaFT, a global coronal feature tracing algorithm, in white-light coronagraph images to outputs of MAS, an advanced magnetohydrodynamic model. We use the FORWARD toolset to produce synthetic polarized brightness images co-aligned to real coronagraph observations, segment features in these images, and quantify the difference between the inferred and model magnetic field. This approach allows us to geometrically compare features segmented in artificial images to those segmented in white-light coronagraph observations against the plane-of-sky projected MAS coronal magnetic field. We quantify QRaFT's performance in the artificial images and observational data, and perform statistical analyses that measure the similarity of these results to compute the accuracy and uncertainty of the model output to the observational data. The results demonstrate through a quantitative evaluation that a coronal segmentation method identifies the global large-scale orientation of the coronal magnetic field within $\sim\pm10^\circ$ of the plane-of-sky projected MAS magnetic field.

Determining the nature of emission processes at the heart of quasars is critical for understanding environments of supermassive black holes. One of the key open questions is the origin of long-wavelength emission from radio-quiet quasars. The proposed mechanisms span a broad range, from central star formation to dusty torus, low-power jets, or coronal emission from the innermost accretion disk. Distinguishing between these scenarios requires probing spatial scales $\leq$0.01 pc, beyond the reach of any current millimetre-wave telescope. Fortunately, in gravitationally lensed quasars, compact mm-wave emission might be microlensed by stars in the foreground galaxy, providing strong constraints on the source size. We report a striking change in rest-frame 1.3-mm flux-ratios in RXJ1131-1231, a quadruply-lensed quasar at z = 0.658, observed by the Atacama Large Millimeter/submillimeter Array (ALMA) in 2015 and 2020. The observed flux-ratio variability is consistent with microlensing of a very compact source with a half-light radius $\leq$50 astronomical units. The compactness of the source leaves coronal emission as the most likely scenario. Furthermore, the inferred mm-wave and X-ray luminosities follow the characteristic Güdel-Benz relationship for coronal emission. These observations represent the first unambiguous evidence for coronae as the dominant mechanism for long-wavelength emission in radio-quiet quasars.

Motivated by a recent proposal that points to the Sombrero galaxy as a source of the highest energy cosmic rays, we investigate the feasibility of accelerating light and heavy nuclei in the supermassive black hole located at the center of this dormant galaxy. We show that cosmic ray nuclei concentrated in the immediate vicinity of the supermassive black hole could be efficiently accelerated up to the maximum observed energies without suffering catastrophic spallations. Armed with our findings we stand against the conventional wisdom and conjecture that accelerators of the highest energy cosmic rays must anti-correlate with the (electromagnetic) source power.

Using multidirectional measurements from the Transiting Exoplanet Survey Satellite (TESS), we investigated the viability of determining the approximate shape and spin axis orientations for 44 selected main belt asteroids, using light curve inversion, assuming Lommel-Seeliger ellipsoids. This study aims to investigate the applicability of low-degree-of-freedom shape models in those cases when rotation periods can be accurately determined, but light curves are only available in a limited number of geometries or orbital phases. Our results are compared with the shape and spin axis solutions obtained for the same set of asteroids by more complex light curve inversion methods using mainly ground-based measurements, available via the Database of Asteroid Models from Inversion Techniques (DAMIT).The best-fit spin-axis orientations show a moderately good match with the DAMIT solutions; however, a better agreement is reached with triaxial ellipsoid solution obtained from other large, independent surveys. This suggests that while TESS-only data works well for finding rotation periods, it has its limitations when determining asteroid shape and spin-axis orientation. We discuss the challenges and potential applications of this approach for studying large number of asteroids observed by TESS.

The cumulative number density matching approach equates number densities between adjacent redshifts to derive empirical galaxy evolution tracks from the observed galaxy stellar mass function. However, it is well known that this approach overlooks scatter in mass assembly histories and merger effects, with previous studies relying on model-based corrections, either from hydrodynamical cosmological simulations or adjustments to the evolution of cumulative number density with redshift. Here, we revisit this approach, showing that dark matter halo assembly histories imply evolving number densities that are far from constant. These exhibit an average slope of $d \log n_\text{vir} /dz \sim 0.2$ dex for progenitors at $z=0$, leading to evolutionary tracks where galaxies are $\sim2-3$ times smaller in mass at $z\sim2$ and an order of magnitude smaller by $z\sim7$ compared to the number density matching approach. We show that evolving halo number densities provide realistic evolutionary tracks without relying on model-based corrections. Accounting for random errors in stellar mass measurements is also crucial for robust track derivation. We also discuss a generalization that incorporates a galaxy's star formation activity. When additionally considering the scatter around the $M_\ast-M_\text{vir}$ relation ($\sim0.15$ dex), our evolving halo cumulative number density approach shows that some observed stellar masses, $M_{\text{obs},\ast}$, can exceed the universal baryon fraction $f_\text{bar}\sim0.16$. For instance, at $z=5$, around $2\%$ of progenitor galaxies of haloes with $M_\text{vir} \sim 3\times 10^{12}\,M_\odot$ have $M_{\text{obs},\ast}>f_\text{bar} \; M_\text{vir}$, suggesting a potential ``early galaxy formation problem''. However, when deconvolving mass from random errors this tension is reduced with significant confidence at the $\sim5-6\sigma$ level.

This paper presents the technical design of the pathfinder Barcelona Raman LIDAR (pBRL) for the northern site of the Cherenkov Telescope Array Observatory (CTAO-N) located at the Roque de los Muchachos Observatory (ORM). The pBRL is developed for continuous atmospheric characterization, essential for correcting high-energy gamma-ray observations captured by Imaging Atmospheric Cherenkov Telescopes (IACTs). The LIDAR consists of a steerable telescope with a 1.8 m parabolic mirror and a pulsed Nd:YAG laser with frequency doubling and tripling. It emits at wavelengths of 355 nm and 532 nm to measure aerosol scattering and extinction through two elastic and Raman channels. Built upon a former Cherenkov Light Ultraviolet Experiment (CLUE) telescope, the pBRL's design includes a Newtonian mirror configuration, a coaxial laser beam, a near-range system, a liquid light guide and a custom-made polychromator. During a one-year test at the ORM, the stability of the LIDAR and semi-remote-controlled operations were tested. This pathfinder leads the way to designing a final version of a CTAO Raman LIDAR which will provide real-time atmospheric monitoring and, as such, ensure the necessary accuracy of scientific data collected by the CTAO-N telescope array.

The X-rays and Extreme Ultraviolet (XUV) emission from M stars can drive the atmospheric escape on planets orbiting them. M stars are also known for their frequent emission of stellar flares, which will increase the high-energy flux received by their orbiting planets. To understand how stellar flares impact the primordial atmospheres of planets orbiting young M stars, we use UV spectroscopic data of flares from the Habitable Zones and M dwarf Activity across Time (HAZMAT) and Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary Systems (MUSCLES) programs as a proxy to the XUV flare emission. Using the software package VPLanet, we simulate the young AU Mic planetary system composed of two Neptune-sized and one Earth-sized planet orbiting a 23-Myr-old M1 star. Our findings show that the Earth-sized planet AU Mic d should be in the process of losing completely its atmosphere in the next couple million years, solely due to the quiescent emission, with flares not significantly contributing to its atmospheric escape due to the small size of AU mic d and its close-in distance from the star. However, our results indicate that flares would play a crucial role for such planets further away, in the habitable zone (i.e. 0.2935 AU) of AU Mic-like stars during the post-saturation phase, accelerating the total atmospheric loss process by a few billion years. For planets between 0.365 AU and the HZ outer edge, the additional XUV from flares is necessary to deplete primordial atmospheres fully since the quiescent emission alone is insufficient.

Context. Binary asteroids are present in all populations of the Solar System, from near-Earth to trans-Neptunian regions. As is true for the small Solar System bodies (SSSBs), binary asteroids generally offer valuable insights into the formation of the Solar System, as well as its collisions and dynamic evolution. In particular, the binaries provide fundamental quantities and properties of these SSSBs, such as mass, angular momentum, and density, all of which are often hidden. The direct measurement of densities and porosities is of great value in revealing the gravitational aggregates and icy bodies that form the asteroid-comet continuum. Aims. Several observation techniques from space and ground-based platforms have provided many results in this regard. Here we show the value of the Gaia mission and its high-precision astrometry for analysing asteroid binaries and for individually deriving the masses of the components. Methods. We focus on the binary asteroid (4337) Arecibo, a member of the Themis family. We analysed the astrometry obtained in the Gaia FPR catalogue release, and performed orbital fitting for both the heliocentric orbit of the system and the relative orbit of the binary components. Results. We obtain an estimation of the component masses and their flux ratio, and derive bulk densities rho1 = 1.2 and rho2 = 1.6 for the primary and the secondary, respectively. The results are consistent with an ice-rich body in the outer main belt. They also show a significantly denser secondary or a less closely packed primary. Constraints on these densities and on macroscopic porosities are nevertheless limited by our poor knowledge of the sizes of the components. Observations of future mutual events, and of stellar occultations predicted in 2024 - 2025, will be essential for improving our knowledge of this system and its formation.

The classical nova V392 Per 2018 is characterized by a very fast optical decline, long binary orbital period of 3.23 days, detection of GeV gamma rays, and almost identical decay trends of $B$, $V$, and $I_{\rm C}$ light curves. The last feature is unique because most novae develop strong emission lines in the nebular phase and these lines contribute especially to the $B$ and $V$ bands and make large differences between the $BV$ and $I_{\rm C}$ light curves. This unique feature can be understood if the optical flux is dominated by continuum until the late phase of the nova outburst. Such continuum radiation is emitted by a bright accretion disk irradiated by a hydrogen burning white dwarf (WD) and viscous heating disk with high mass-accretion rate after the hydrogen burning ended. We present a comprehensive nova outburst model that reproduces all of these light curves. We determined the WD mass to be $M_{\rm WD}=1.35$ - $1.37 ~M_\odot$ and the distance modulus in the $V$ band to be $(m-M)_V=14.6 \pm 0.2$; the distance is $d= 3.45\pm 0.5$ kpc for the reddening of $E(B-V)=0.62$.

Context. Over the past few years, the $R$-Process Alliance (RPA) has successfully carried out a search for stars that are highly enhanced in elements produced via the rapid neutron-capture ($r$-) process. In particular, the RPA has identified a number of relatively bright, highly $r$-process-enhanced ($r$-II) stars, suitable for observations with the Hubble Space Telescope (HST), facilitating abundance derivation of elements such as gold (Au) and cadmium (Cd). Aims. This paper presents the detailed abundances derived for the metal-poor ([Fe/H] = -2.55) highly $r$-process-enhanced ([Eu/Fe] = +1.29) $r$-II star 2MASS J05383296-5904280. Methods. 1D LTE elemental abundances are derived via equivalent width and spectral synthesis using high-resolution high signal-to-noise near-UV HST/STIS and optical Magellan/MIKE spectra. Results. Abundances are determined for 43 elements, including 26 neutron-capture elements. In particular, abundances of the rarely studied elements Nb, Mo, Cd, Lu, Os, Pt, and Au are derived from the HST spectrum. These results, combined with RPA near-UV observations of two additional $r$-II stars, increase the number of Cd abundances derived for $r$-process-enriched stars from seven to ten and Au abundances from four to seven. A large star-to-star scatter is detected for both of these elements, highlighting the need for more detections enabling further investigations, specifically into possible non-LTE (local thermodynamical equilibrium) effects.

The currently observing Dark Energy Spectroscopic Instrument (DESI) places sub-percent constraints on the Baryon Acoustic Oscillations (BAO) scaling parameters from the Lyman-$\alpha$ (Ly-$\alpha$) forest. However, no systematic error budget stemming from non-linearities in the 3D clustering of the Ly-$\alpha$ forest is included in the DESI-Ly-$\alpha$ analysis. In this work, we measure the size of the shift of the BAO peak using large Ly-$\alpha$ forest mocks produced on the $N$-body simulation suite \textsc{AbacusSummit}. Specifically, we measure the Ly-$\alpha$ auto-correlation and the Ly-$\alpha$-quasar cross-correlation functions. We use the DESI Ly-$\alpha$ forest fitting pipeline, \textsc{Vega}, with the publicly available covariance matrix from eBOSS DR16. To mitigate the noise, we adopt a linear control variates (LCV) technique, reducing the error bars by a factor of up to $\sim \sqrt{50}$ on large scales. From the auto-correlation, we detect a small positive shift in radial direction of $\Delta \alpha_\parallel = 0.35\%$ at the 3$\sigma$ level and virtually no shift in the transverse direction, $\alpha_\perp$. From the cross-correlation, we see a similar shift to $\Delta\alpha_\parallel$, albeit with larger error bars, and a small negative shift, $\Delta \alpha_\perp=\sim$0.25\%, at the 2$\sigma$ level. We also make a connection with the Ly-$\alpha$ forest effective field theory (EFT) framework and find that the one-loop EFT power spectrum yields unbiased measurements of the BAO shift parameters in radial and transverse direction for Ly-$\alpha$ auto and the Ly-$\alpha$-quasar cross-correlation measurements. When using the one-loop EFT framework, we find that we can recover the BAO parameters without a shift, which has important implications for future Ly-$\alpha$ forest analyses based on EFT. This work paves the way for the full-shape analysis of DESI and future surveys.

We present a nontrivial extension of the problem of spherical accretion of a collisionless kinetic gas into the standard Schwarzschild black hole. This extension consists of replacing the Schwarzschild black hole by generic static and spherically symmetric black hole spacetimes with the aim of studying the effects of either modified gravitational theories beyond Einstein gravity or matter sources coupled to general relativity on the accretion process. This generalization also allows us to investigate the accretion into other types of black hole spacetimes, such as ones inspired by loop quantum gravity and string theory. To do so, we take into account a large class of static and spherically symmetric black holes whose spacetime is asymptotically flat with a positive total mass, has a regular Killing horizon, and satisfies appropriate monotonicity conditions of the metric functions. We provide the most general solution of the collisionless Boltzmann equation on such spacetimes by expressing the one-particle distribution function in terms of suitable symplectic coordinates on the cotangent bundle, and we calculate the relevant observables, such as particle current density and energy-momentum-stress tensor. Specializing to the case where the gas is described by an isotropic ideal fluid at rest at infinity, we compute the mass accretion rate and compression ratio, and we show that the tangential pressure is larger than the radial one at the horizon, indicating that the behavior of a collisionless gas is different from the one of an isotropic perfect fluid. As an example, we apply our generic formulae to two special black hole spacetimes, namely the Reissner-Nordström black hole and a loop quantum corrected black hole. We explore the effects of the free parameters on the observables and accretion rate, and we compare the results with those corresponding to the Schwarzschild black hole.

I present the first constraints on QCD axion dark matter using measurements from the James Webb Space Telescope. By utilizing publicly available MIRI and NIRSpec blank-sky observations, originally collected for sky subtraction purposes, I derive strong limits on the axion-photon coupling constant $g_{a \gamma \gamma}$ in the mass range 0.1-4 eV. These constraints improve upon previous studies by more than two orders of magnitude for a range of masses. This analysis underscores the potential of blank-sky observations as a powerful tool for constraining dark matter models and demonstrates how astrophysical missions can be repurposed for particle physics research.

We present the first precise calculations of the gravitational quasinormal-mode (QNM) frequencies for spinning black holes with dimensionless angular momenta $J/M^2 := a \lesssim 0.75$ in dynamical Chern-Simons gravity. Using the \textit{Metric pErTuRbations wIth speCtral methodS} (METRICS) framework, we compute the QNM frequencies of both axial and polar metric perturbations, focusing on the $nl m = 022$, $033$, and $032$ modes. The METRICS frequencies for the 022 mode achieve numerical uncertainties $\lesssim 10^{-4}$ when $0 \leq a \leq 0.5$ and $\lesssim 10^{-3}$ for $0.5 \leq a \leq 0.75$, without decoupling or simplifying the linearized field equations. We also derive optimal fitting polynomials to enable efficient and accurate evaluations of the leading-order frequency shifts in these modes. The METRICS frequencies and fitting expressions are a robust and indispensable step toward enabling gravitational-wave ringdown tests of dynamical Chern-Simons gravity.

A neutron star (NS) in a binary system deforms due to the companion's tidal gravitational field. As the binary inspirals due to gravitational wave (GW) emission, the NS's deformation evolves; this evolution is typically modeled as the star's linear response to the companion's time-evolving tidal potential. In principle, the fluid elements' displacements can be excited and evolve nonlinearly since the equations of hydrodynamics and the tidal forcing have nonlinear terms. Recently, Kwon, Yu, and Venumadhav (KYV I [arXiv:2410.03831]) showed that nonlinear terms in the hydrodynamic equations of motion make the low-frequency response of NSs, characterized by gravity ($g$-) modes, behave in an anharmonic manner. The anharmonicity is dominantly generated by the mutual coupling of the four lowest-order ($n=1$, $l=|m|=2$) $g$-modes, and allows them to stay locked in a resonant state that oscillates phase-coherently with the orbit throughout the inspiral. As a result, the $g$-modes grow to larger amplitudes than the linear response suggests, leading to an extra phase correction to the frequency-domain GW signal $|\Delta \Psi|\approx 3\,{\rm rad}$ at a GW frequency of $1.05\,{\rm kHz}$. This effect is part of the truly dynamical tide, in the sense that the amplitude depends not just on the binary's instantaneous frequency but the entire history of the inspiral. In this paper, we explain the phenomenology of resonance locking in detail and analytically validate the numerical dephasing calculations in KYV I. We also demonstrate that the effect is only significant for the lowest-order $g$-modes.

In this study, we investigate the geodesic structure, gravitational lensing/mirroring phenomena, and scalar perturbations of deformed AdS-Schwarzschild black holes with global monopoles, incorporating both ordinary and phantom configurations. We introduce a modified black hole metric characterized by a deformation parameter $\alpha$, a control parameter $\beta$, and a symmetry-breaking scale parameter $\eta$, which collectively influence the spacetime geometry. Through comprehensive geodesic analysis, we determine the photon sphere radius numerically for various parameter configurations, revealing significant differences between ordinary and phantom global monopoles. The stability of timelike circular orbits is assessed via the Lyapunov exponent, demonstrating how these parameters affect orbital dynamics. Our gravitational lensing analysis, employing the Gauss-Bonnet theorem, reveals a remarkable gravitational mirroring effect in phantom monopole spacetimes at high AdS curvature radii, where light rays experience negative deflection angles-being repelled rather than attracted by the gravitational field. Furthermore, we analyze massless scalar perturbations and derive the corresponding greybody factors, which characterize the transmission of Hawking radiation through the effective potential barrier surrounding the black hole. Our numerical results indicate that phantom global monopoles substantially modify both gravitational lensing/mirroring properties and the radiation spectrum compared to ordinary monopoles. The presence of the deformation parameter $\alpha$ introduces additional complexity to the system, leading to distinct thermodynamic behavior that deviates significantly from the standard AdS-Schwarzschild solution.

The maximal frequency domain of the cosmic gravitons falls in the THz region where, without conflicting with the existing phenomenological bounds, only few particles with opposite (comoving) three-momenta are produced. Although any reliable scrutiny of the ultra-high frequency spikes should include all the sources of late-time suppression at lower and intermediate frequencies, some relevant properties of the averaged multiplicities and of the spectral energy density can be derived within a reduced set of approximations that may become invalid as the frequency decreases well below the Hz. The accuracy of these concurrent approaches is assessed from the properties of the transition matrix that relates the late-time spectra to the values of the mode functions during an inflationary stage. In the obtained framework the bounds on the post-inflationary expansion rate are swiftly deduced and compare quite well with the ones including a more faithful numerical treatment. It also follows that the timeline of the post-inflationary expansion rate might be observationally accessible, in the years to come, provided the electromechanical detectors (like microwave cavities or waveguides) operating between the MHz and the THz shall eventually reach sensitivities in the chirp amplitudes which are (at least) twelve orders of magnitude smaller than the ones experimentally attainable in the audio band (i.e. between few Hz and the kHz).

Very Special Linear Gravity (VSL-Gravity) is an alternative model of linearized gravity that incorporates massive gravitons while retaining only two physical degrees of freedom thanks to gauge invariance. Recently, the gravitational period-decay dynamics of the model has been determined using effective field theory techniques. In this study, we conduct a comprehensive Bayesian analysis of the PSR B1913+16 binary pulsar dataset to test the predictions of VSL-Gravity. Our results place a 95\% confidence level upper bound on the graviton mass at $m_g \lesssim 10^{-19} \, \text{eV}/c^2$. Additionally, we observe a significant discrepancy in the predicted mass of one of the binary's companion stars. Lastly, we discuss the broader implications of a non-zero graviton mass, from astrophysical consequences to potential cosmological effects.

This paper establishes the minimum entropy principle (MEP) for the relativistic Euler equations with a broad class of equations of state (EOSs) and addresses the challenge of preserving the local version of the discovered MEP in high-order numerical schemes. At the continuous level, we find out a family of entropy pairs for the relativistic Euler equations and provide rigorous analysis to prove the strict convexity of entropy under a necessary and sufficient condition. At the numerical level, we develop a rigorous framework for designing provably entropy-preserving high-order schemes that ensure both physical admissibility and the discovered MEP. The relativistic effects, coupled with the abstract and general EOS formulation, introduce significant challenges not encountered in the nonrelativistic case or with the ideal EOS. In particular, entropy is a highly nonlinear and implicit function of the conservative variables, making it particularly difficult to enforce entropy preservation. To address these challenges, we establish a series of auxiliary theories via highly technical inequalities. Another key innovation is the use of geometric quasi-linearization (GQL), which reformulates the nonlinear constraints into equivalent linear ones by introducing additional free parameters. These advancements form the foundation of our entropy-preserving analysis. We propose novel, robust, locally entropy-preserving high-order frameworks. A central challenge is accurately estimating the local minimum of entropy, particularly in the presence of shock waves at unknown locations. To address this, we introduce two new approaches for estimating local lower bounds of specific entropy, which prove effective for both smooth and discontinuous problems. Numerical experiments demonstrate that our entropy-preserving methods maintain high-order accuracy while effectively suppressing spurious oscillations.

We analyse the observations of the satellites of Jupiter from the Sidereus Nuncius (January 7 to March 1, 1610) and compare them to the predictions obtained using a modern sky simulator, verifying them one by one. A sinusoidal fit of the data obtained from the 64 available sketches, allows measuring the relative major semi-axes of the satellites' orbits and their periods with a statistical precision of 2-4\% and 0.1-0.3\% respectively. The periods are basically unbiased while the orbits tend to be underestimated for Callisto by about 12\%. The posterior fit error indicates that the positions of the satellites are determined with a resolution of 0.4-0.6 Jupiter diameters in the notation of Galilei corresponding to about 40- 70 arc sec i.e. similar to the true angular diameter of Jupiter, in those days. We show that with this data one can infer in a convincing way the third law of Kepler for the Jupiter system. The 1:2 and 1:4 orbital resonance between the periods of Io and Europa/Ganymede can be determined with \% precision. In order to obtain these results it is important to separate the four datasets. This operation, which is nowadays simple using a sky simulator, and is fully reported in this work, was an extremely difficult task for Galilei as the analysis will evidence. Nevertheless we show how the four periods might have been extracted using the modern Lomb-Scargle technique without having to separate the four data-sets already just using these early observations. We also perform a critical evaluation of the accuracy of the observation of the Pleiades and other clusters and the Moon.

Spin-$s$ light dark boson particles can exhibit wave-like behavior, capable of forming long-lived, coherent, spatially localized structures known as solitons. This work considers the possibility that a light spin-2 particle might be part of or all the dark matter content of the Universe, which could result in a significant fraction of solitons existing today in galactic halos. If these dark matter particles interact with electromagnetism through dimension-6 operators, the solitons may experience parametric resonance of photons triggered by the surrounding electromagnetic field. We explore the feasibility and key characteristics of this electromagnetic radiation, as well as the potential for detection through soliton mergers using ground-based facilities.

Photon propagators for power-law inflation are constructed in two one-parameter families of noncovariant gauges, in an arbitrary number of spacetime dimensions. In both gauges photon propagators take relatively simple forms expressed in terms of scalar propagators and their derivatives. These are considerably simpler compared to their general covariant gauge counterpart. This makes feasible performing dimensionally regulated loop computations involving massless vector fields in inflation.

We investigate the linear tearing instability in weakly collisional, gyrotropic plasmas via a non-ideal CGL-MHD framework. Even for an initially isotropic equilibrium, our analysis reveals a striking dependence of the maximum growth rate on plasma-$\beta$, with $\gamma_{max}\tau_{A}\propto\beta^{-1/4}$ in the high-$\beta$ regime, thereby challenging the $\beta$-independence predicted by standard MHD theory. We show that this new scaling emerges from the self-consistent fluctuations in pressure anisotropy, which can suppress or enhance the instability depending on the underlying plasma parameters. Systematic scans of the Lundquist number, magnetic Prandtl number, and anisotropy degree $\Delta\beta$ highlight conditions under which the tearing mode departs significantly from classical behavior. Our findings emphasize that weak collisionality and gyrotropic effects must be considered to accurately capture tearing evolution in high-$\beta$ plasma environments.

The hydrogen ions in the superionic ice can move freely, playing the role of electrons in metals. Its electromagnetic behavior is the key to explaining the anomalous magnetic fields of Uranus and Neptune. Based on the ab initio evolutionary algorithm, we searched for the stable H4O crystal structure under pressures of 500-5000 GPa and discovered a new layered chain $Pmn2_1$-H$_4$O structure with H$_3$ ion clusters. Interestingly, H3 ion clusters rotate above 900 K (with an instantaneous speed of 3000 m/s at 900 K), generating an instantaneous magnetic moment ($10^{-26}$ Am$^2 \approx 0.001 \mu_B$). Moreover, H ions diffuse in a direction perpendicular to the H-O atomic layer at 960-1000 K. This is because the hydrogen oxygen covalent bonds within the hydrogen oxygen plane hinder the diffusion behavior of H$_3$ ion clusters within the plane, resulting in the diffusion of H$_3$ ion clusters between the hydrogen oxygen planes and the formation of a one-dimensional conductive superionic state. One-dimensional diffusion of ions may generate magnetic fields. We refer to these two types of magnetic moments as "thermal-induced ion magnetic moments". When the temperature exceeds 1000 K, H ions diffuse in three directions. When the temperature exceeds 6900 K, oxygen atoms diffuse and the system becomes fluid. These findings provide important references for people to re-recognize the physical and chemical properties of hydrogen and oxygen under high pressure, as well as the sources of abnormal magnetic fields in Uranus and Neptune.

DECIGO (DECi-hertz Interferometer Gravitational Wave Observatory) is a space-based gravitational wave antenna concept targeting the 0.1-10 Hz band. It consists of three spacecraft arranged in an equilateral triangle with 1,000 km sides, forming Fabry-Pérot cavities between them. A precursor mission, B-DECIGO, is also planned, featuring a smaller 100 km triangle. Operating these cavities requires ultra-precise formation flying, where inter-mirror distance and alignment must be precisely controlled. Achieving this necessitates a sequential improvement in precision using various sensors and actuators, from the deployment of the spacecraft to laser link acquisition and ultimately to the control of the Fabry-Pérot cavities to maintain resonance. In this paper, we derive the precision requirements at each stage and discuss the feasibility of achieving them. We show that the relative speed between cavity mirrors must be controlled at the sub-micrometer-per-second level and that relative alignment must be maintained at the sub-microradian level to obtain control signals from the Fabry-Pérot cavities of DECIGO and B-DECIGO.

We explore the effects of gravitational waves (GWs) on hydrogen's radio spectral lines, focusing on the ground-state hyperfine transition and radiative transitions in highly excited Rydberg states. To analyze GW impacts on hyperfine structure, we derive Maxwell's equations in a gravitational-wave background using linearized gravity and the $3+1$ formalism. Our findings reveal that GWs induce energy shifts in hyperfine magnetic substates, modifying the 21 cm line. However, these energy shifts fall well below the detection limits of current radio astronomical instruments. For transitions in highly excited states, which produce radio recombination lines (RRL), the influence of GW manifests itself as spectral broadening, with the fractional linewidth for $\mathrm{H}n\alpha$ scaling as $\Delta\nu/\nu_0 \sim n^7\omega^2_{\mathrm{gw}}h(t)$. This suggests that RRLs could serve as probes for ultra-high-frequency GWs, particularly given that Rydberg atoms in the interstellar medium can reach quantum numbers above $n=100$. As an example of possibly detectable high frequency GW source, We investigate GWs emitted during the inspiral of planetary-mass primordial black hole binaries, where GW-induced broadening in RRLs could exceed natural broadening effects. Additionally, we examine the influence of the recently detected stochastic gravitational-wave background on hydrogen spectral lines.

We investigate the effects of extended mass and spheroidal deformation on the periapsis shift of quasi-circular orbits inside a gravitating mass distribution in the Newtonian framework. Focusing on the internal gravitational potential of a spheroidal body with both homogeneous and inhomogeneous density profiles, we elucidate how the ratio of local density to average density governs the extended mass effect on the periapsis shift. By analyzing the orbital angular frequency, along with the radial and vertical epicyclic frequencies, we demonstrate that in the uniform density case (i.e., the Maclaurin spheroid), where the potential takes the form of a harmonic oscillator, the periapsis exhibits a constant retrograde shift of $-\pi$. In contrast, in regions where density inhomogeneity and spheroidal deformation (in both prolate and oblate forms) are significant, the periapsis shift varies with the guiding orbital radius due to local density contrast and deformation effects. The resuls indicate that oblate deformation suppresses the extended mass effect associated with the ratio of local density to average density, whereas prolate deformation amplifies it. Furthermore, by varying the density distribution parameters, we establish the conditions for orbital stability and identify the emergence of marginally stable orbits.

We explore scalarized Einstein-Gauss-Bonnet theories within the context of the Parameterized Post-Newtonian formalism, which serves as a robust framework for examining modifications to General Relativity that exhibit scalarization. This approach enables us to impose a variety of constraints on the parameter space, particularly focusing on the PPN parameters $\gamma$ and $\beta$. Our analysis reveals several significant bounds for each scalarized model, utilizing data from the Cassini mission, Lunar Laser Ranging, and the forthcoming BepiColombo mission, in conjunction with geodetic Very Long Baseline Interferometry measurements around the Sun. In particular, we conducted a combined analysis of the MESSENGER mission's precision measurements of Mercury's perihelion precession $\dot{\omega}$ alongside the Cassini constraints on $\gamma$, yielding intriguing limits for the Ricci-EGB model. Furthermore, we investigate the impact of the new post-Newtonian potential introduced by the Gauss-Bonnet term at fourth order, which necessitates an expanded formulation of the PPN parameters. This highlights that the parameter $\beta$ exhibits different effects when analyzing the Ricci-EGB model. Additional constraints are derived from this framework by estimating the $\gamma$ PPN parameter using data from strong-lensing galaxy systems.