Papers for Friday, Jul 26 2024

This work tackles a significant challenge in dynamo theory: the possibility of long-term amplification and maintenance of an axisymmetric magnetic field. We introduce a novel model that allows for non-trivial axially-symmetric steady-state solutions for the magnetic field, particularly when the dynamo operates primarily within a "nearly-spherical" toroidal volume inside a fluid shell surrounding a solid core. In this model, Ohm's law is generalized to include the restoring friction force, which aligns the velocity of the shell with the rotational speed of the inner core and outer mantle. Our findings reveal that, in this context, Cowling's theorem and the neutral point argument are modified, leading to magnetic energy growth for a suitable choice of toroidal flow. The global equilibrium magnetic field that emerges from our model exhibits a dipolar character.

Brown dwarfs (BD) are model degenerate in age and mass. High-contrast imaging and spectroscopy of BD companions to host stars where the mass and age can be independently constrained by dynamics and stellar age indicators respectively provide valuable tests of BD evolution models. In this paper, we present a new epoch of Subaru/CHARIS H- and K-band observations of one such previously discovered system, HD 33632 Ab. We reanalyze the mass and orbit using our new epoch of extracted relative astrometry, and fit extracted spectra to the newest generation of equilibrium, disequilibrium, and cloudy spectral and evolution models for BDs. No spectral model perfectly agrees with evolutionary tracks and the derived mass and age, instead favoring a somewhat younger BD than the host star's inferred age. This tension can potentially be resolved using atmosphere and evolution models that consider both clouds and disequilibrium chemistry simultaneously, or by additional future spectra at higher resolution or in other band passes. Photometric measurements alone remain consistent with the luminosity predicted by evolutionary tracks. Our work highlights the importance of considering complexities like clouds, disequilibrium chemistry, and composition when comparing spectral models to evolutionary tracks.

Here, I present the community with exoTEDRF (EXOplanet Transit and Eclipse Data Reduction Framework; formerly known as supreme-SPOON), an end-to-end pipeline for data reduction and light curve analysis of time series observations (TSOs) of transiting exoplanets with JWST. The pipeline is highly modular and designed to produce reliable spectra from raw JWST exposures. exoTEDRF (pronounced exo-tedorf) consists of four stages, each of which are further subdivided into a series of steps. These steps can either be run individually, for example in a Jupyter notebook, or via the command line using the provided configuration files. The steps are highly tunable, allowing full control over every parameter in the reduction. Each step also produces diagnostic plots to allow the user to verify their results at each intermediate stage, and compare outputs with other pipelines if so desired. Finally, exoTEDRF has also been designed to be run in "batch" mode: simultaneously running multiple reductions, each tweaking a subset of parameters, to understand any impacts on the resulting atmosphere spectrum.

We present our numerical simulation approach for the End-to-End (E2E) model applied to various astronomical spectrographs, such as SOXS (ESO-NTT), CUBES (ESO-VLT), and ANDES (ESO-ELT), covering multiple wavelength regions. The E2E model aim at simulating the expected astronomical observations starting from the radiation of the scientific sources (or calibration sources) up to the raw-frame data produced by the detectors. The comprehensive description includes E2E architecture, computational models, and tools for rendering the simulated frames. Collaboration with Data Reduction Software (DRS) teams is discussed, along with efforts to meet instrument requirements. The contribution to the cross-correlation algorithm for the Active Flexure Compensation (AFC) system of CUBES is detailed.

To understand the origin of extended disks of low-surface brightness (LSB) galaxies, we studied in detail 4 such systems with large disks seen edge-on. Two of them are edge-on giant LSB galaxies (gLSBGs) recently identified by our team. The edge-on orientation of these systems boosts their surface brightnesses that provided an opportunity to characterize stellar populations spectroscopically and yielded the first such measurements for edge-on gLSBGs. We collected deep images of one galaxy using the 1.4-m Milanković Telescope which we combined with the archival Subaru Hyper Suprime-Cam and DESI Legacy Surveys data available for the three other systems, and measured the structural parameters of the disks. We acquired deep long-slit spectra with the Russian 6-meter telescope and the 10-m Keck II telescope and estimated stellar population properties in the high- and low-surface brightness regions as well as the gas-phase metallicity distribution. The gas metallicity gradients are shallow to flat in the range between 0 and -0.03 dex per exponential disk scale length, which is consistent with the extrapolation of the gradient -- scale length relation for smaller disk galaxies. Our estimates of stellar velocity dispersion in the LSB disks as well as the relative thickness of the disks indicate the dynamical overheating. Our observations favor mergers as the essential stage in the formation scenario for massive LSB galaxies.

Outflowing gas from supermassive black holes in the centers of active galaxies has been postulated as a major contributor to galactic evolution. To explore the interaction between narrow-line region (NLR) outflows and their host galaxies, we use Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) spectra and Wide Field Camera 3 (WFC3) images of 15 nearby (z < 0.02) active galactic nuclei (AGN) to determine the extents and geometries of their NLRs. We combine new HST WFC3 continuum and [O III] $\lambda$5007A images of 11 AGN with 4 archival AGN to match existing spectra from HST STIS. For the 6 AGN with suitable long-slit coverage of their NLRs, we use isophotal fitting of ground-based images, continuum-subtracted [O III] images, and the STIS spectra, to resolve, measure, and de-project the gas kinematics to the plane of the host galaxy disk and distinguish NLR outflows from galaxy rotation and/or kinematically disturbed gas. We find an average [O III] extent of $\sim$680pc with a correlation between gas extent and [O III] luminosity of R$_\mathrm{[O III]}$ $\propto$ L$_{\text{[O III]}}^{0.39}$. The measured extents depend strongly on the depth of the [O III] images, highlighting the importance of adopting uniform thresholds when analyzing scaling relationships. The outflows reach from 39-88% of the full NLR extents, and we find that all 6 of the AGN with STIS coverage of their entire NLRs show strong kinematic evidence for outflows, despite previous uncertainty for these AGN. This suggests that NLR outflows are ubiquitous in moderate luminosity AGN and that standard criteria for kinematic modeling are essential for identifying outflows.

We present the BoRG-JWST survey, a combination of two JWST Cycle 1 programs aimed at obtaining NIRSpec spectroscopy of representative, UV-bright $7<z<10$ galaxy candidates across 22 independent sight lines selected from Hubble/WFC3 pure-parallel observations. We confirm the high-$z$ nature of 10 out of 19 observed primary targets through low-resolution prism observations, with the rest revealing themselves unsurprisingly to be $z\sim1-3$ interlopers, brown dwarfs, or yielding inconclusive results. From the MSA observations, we confirm an additional 9 filler sources at $z>5$, highlighting the large abundance of high-redshift galaxies even in individual WFC3 pointings. The primary sample span an absolute magnitude range $-20.4<M_{\rm UV}<-22.4$ mag and harbour UV continuum slopes of $\beta\simeq-2.5$ to $-2.0$, representing some of the most luminous $z>7$ sources currently known and comparable to the brightest sources at $z>10$. Prominent [O III]+H$\beta$ lines are found across the full sample, while a stack of sources reveals a plethora of other rest-optical lines and additional rest-UV C III]1909 Å emission. Despite their luminosities, none of the low-resolution spectra display evidence for Type 1 AGN activity based on a search for broad-line emission. Lastly, we present a spectroscopic data release of 188 confirmed $0.5\lesssim z\lesssim5.0$ sources from filler MSA observations, highlighting the legacy value of the survey and a representative benchmark for comparisons to deep field observations.

The majority of low-mass ($\log_{10} M_*/M_{\odot}=9-10$) galaxies at high redshift ($z>1$) appear elongated in projection. We use JWST-CEERS observations to explore the role of gravitational lensing in this puzzle. The typical galaxy-galaxy lensing shear $\gamma\sim1\%$ is too low to explain the predominance of elongated early galaxies with ellipticity $e\approx0.6$. However, non-parametric quantile regression with Bayesian Additive Regression Trees reveals hints of an excess of tangentially-aligned source-lens pairs with $\gamma>10\%$. On larger scales, we also find evidence for weak lensing shear. We rule out the null hypothesis of randomly oriented galaxies at $\gtrsim99\%$ significance in multiple NIRCam chips, modules and pointings. The number of such regions is small and attributable to chance, but coherent alignment patterns suggest otherwise. On the chip scale, the average complex ellipticity $\langle e\rangle\sim10\%$ is non-negligible and beyond the level of our PSF uncertainties. The shear variance $\langle\overline{\gamma}^2\rangle\sim10^{-3}$ is an order of magnitude above the conventional weak lensing regime but is more sensitive to PSF systematics, intrinsic alignments, cosmic variance and other biases. Taking it as an upper limit, the maximum implied ``cosmic shear'' is only a few percent and cannot explain the elongated shapes of early galaxies. The alignments themselves may arise from lensing by a protocluster or filament at $z\sim0.75$ where we find an overabundance of massive lens galaxies. We recommend a weak lensing search for overdensities in ``blank'' deep fields with JWST and the Roman Space Telescope.

We assess the capabilities of the LiteBIRD mission to map the hot gas distribution in the Universe through the thermal Sunyaev-Zeldovich (SZ) effect. Our analysis relies on comprehensive simulations incorporating various sources of Galactic and extragalactic foreground emission, while accounting for specific instrumental characteristics of LiteBIRD, such as detector sensitivities, frequency-dependent beam convolution, inhomogeneous sky scanning, and $1/f$ noise. We implement a tailored component-separation pipeline to map the thermal SZ Compton $y$-parameter over 98% of the sky. Despite lower angular resolution for galaxy cluster science, LiteBIRD provides full-sky coverage and, compared to the Planck satellite, enhanced sensitivity, as well as more frequency bands to enable the construction of an all-sky $y$-map, with reduced foreground contamination at large and intermediate angular scales. By combining LiteBIRD and Planck channels in the component-separation pipeline, we obtain an optimal $y$-map that leverages the advantages of both experiments, with the higher angular resolution of the Planck channels enabling the recovery of compact clusters beyond the LiteBIRD beam limitations, and the numerous sensitive LiteBIRD channels further mitigating foregrounds. The added value of LiteBIRD is highlighted through the examination of maps, power spectra, and one-point statistics of the various sky components. After component separation, the $1/f$ noise from LiteBIRD is effectively mitigated below the thermal SZ signal at all multipoles. Cosmological constraints on $S_8=\sigma_8\left(\Omega_{\rm m}/0.3\right)^{0.5}$ obtained from the LiteBIRD-Planck combined $y$-map power spectrum exhibits a 15% reduction in uncertainty compared to constraints from Planck alone. This improvement can be attributed to the increased portion of uncontaminated sky available in the LiteBIRD-Planck combined $y$-map.

While dynamical tides only become relevant during the last couple of orbits for circular inspirals, orbital eccentricity can increase their impact during earlier phases of the inspiral by exciting tidal oscillations at each close encounter. We investigate the effect of dynamical tides on the orbital evolution of eccentric neutron star binaries using post-Newtonian numerical simulations and constructing an analytic stochastic model. Our study reveals a strong dependence of dynamical tides on the pericenter distance, with the energy transferred to dynamical tides over that dissipated in gravitational waves (GWs) exceeding $\sim1\%$ at separations $r_\mathrm{p}\lesssim50$ km for large eccentricities. We demonstrate that the effect of dynamical tides on orbital evolution can manifest as a phase shift in the GW signal. We show that the signal-to-noise ratio of the GW phase shift can reach the detectability threshold of 8 with a single aLIGO detector at design densitivity for eccentric neutron star binaries at a distance of $40$ Mpc. This requires a pericenter distance of $r_\mathrm{p0}\lesssim68$ km ($r_\mathrm{p0}\lesssim76$ km) at binary formation with eccentricity close to 1 for a reasonable tidal deformability and f-mode frequency of 500 and $1.73$ kHz (700 and $1.61$ kHz), respectively. The observation of the phase shift will enable measuring the f-mode frequency of neutron stars independently from their tidal deformability, providing significant insights into neutron star seismology and the properties of the equation of state. We also explore the potential of distinguishing between equal-radius and twin-star binaries, which could provide an opportunity to reveal strong first-order phase transitions in the nuclear equation of state.

With the growing number of detections of binary black hole mergers, we are beginning to probe structure in the distribution of masses. A recent study by Schneider et al. proposes that isolated binary evolution of stripped stars naturally gives rise to the peaks at chirp masses $\sim 8 M_\odot$, $14 M_\odot$ in the chirp mass distribution and explains the dearth of black holes between $\approx 10-12 M_\odot$ in chirp mass. The gap in chirp mass results from an apparent gap in the component mass distribution between $m_1, m_2 \approx 10-15 M_\odot$ and the specific pairing of these black holes. This component mass gap results from the variation in core compactness of the progenitor, where a drop in compactness of Carbon-Oxygen core mass will no longer form black holes from core collapse. We develop a population model motivated by this scenario to probe the structure of the component mass distribution of binary black holes consisting of two populations: 1) two peak components to represent black holes formed in the compactness peaks, and 2) a powerlaw component to account for any polluting events, these are binaries that may have formed from different channels (e.g. dynamical). We perform hierarchical Bayesian inference to analyse the events from the third gravitational-wave transient catalogue (GWTC-3) with this model. We find that there is a preference for the lower mass peak to drop off sharply at $\sim 11 M_\odot$ and the upper mass peak to turn on at $\sim 13 M_\odot$, in line with predictions from Schneider et al. However, there is no clear evidence for a gap. We also find mild support for the two populations to have different spin distributions. In addition to these population results, we highlight observed events of interest that differ from the expected population distribution of compact objects formed from stripped stars.

We present a dynamical study of the intermediate polar cataclysmic variable YY Dra based on time-series observations in the $K$ band, where the donor star is known to be the major flux contributor. We covered the $3.97$-h orbital cycle with 44 spectra taken between $2020$ and $2022$ and two epochs of photometry observed in 2021 March and May. One of the light curves was simultaneously obtained with spectroscopy to better account for the effects of irradiation of the donor star and the presence of accretion light. From the spectroscopy, we derived the radial velocity curve of the donor star metallic absorption lines, constrained its spectral type to M0.5$-$M3.5 with no measurable changes in the effective temperature between the irradiated and non-irradiated hemispheres of the star, and measured its projected rotational velocity $v_\mathrm{rot} \sin i = 103 \pm 2 \, \mathrm{km}\,\mathrm{s}^{-1}$. Through simultaneous modelling of the radial velocity and light curves, we derived values for the radial velocity semi-amplitude of the donor star, $K_2 = 188^{+1}_{-2} \, \mathrm{km} \, \mathrm{s}^{-1}$, the donor to white dwarf mass ratio, $q=M_2/M_1 = 0.62 \pm 0.02$, and the orbital inclination, $i={42^{\circ}}^{+2^{\circ}}_{-1^{\circ}}$. These binary parameters yield dynamical masses of $M_{1} = 0.99^{+0.10}_{-0.09} \, \mathrm{M}_{\odot}$ and $M_2 = 0.62^{+0.07}_{-0.06} \, \mathrm{M}_{\odot}$ ($68$ per cent confidence level). As found for the intermediate polars GK Per and XY Ari, the white dwarf dynamical mass in YY Dra significantly differs from several estimates obtained by modelling the X-ray spectral continuum.

Atmospheres are not spatially homogeneous. This is particularly true for hot, tidally locked exoplanets with large day-to-night temperature variations, which can yield significant differences between the morning and evening terminators -- known as limb asymmetry. Current transit observations with the James Webb Space Telescope (JWST) are precise enough to disentangle the separate contributions of these morning and evening limbs to the overall transmission spectrum in certain circumstances. However, the signature of limb asymmetry in a transit light curve is highly degenerate with uncertainty in the planet's time of conjunction. This raises the question of how precisely transit times must be measured to enable accurate studies of limb asymmetry, particularly with JWST. Although this degeneracy has been discussed in the literature, a general description of it has not been presented. In this work, we show how this degeneracy results from apparent changes in the transit contact times when the planetary disk has asymmetric limb sizes. We derive a general formula relating the magnitude of limb asymmetry to the amount which it would cause the apparent time of conjunction to vary, which can reach tens of seconds. Comparing our formula to simulated observations, we find that numerical fitting techniques add additional bias to the measured time, of generally less than a second, resulting from the occultation geometry. We also derive an analytical formula for this extra numerical bias. These formulae can be applied to planning new observations or interpreting literature measurements, and we show examples for commonly studied exoplanets.

Very metal-poor stars ([Fe/H]<-2) are important laboratories for testing stellar models and reconstructing the formation history of our galaxy. Asteroseismology is a powerful tool to probe stellar interiors and measure ages, but few asteroseismic detections are known in very metal-poor stars and none have allowed detailed modeling of oscillation frequencies. We report the discovery of a low-luminosity Kepler red giant (KIC 8144907) with high S/N oscillations, [Fe/H]=-2.66+/-0.08 and [alpha/Fe]=0.38+/-0.06, making it by far the most metal-poor star to date for which detailed asteroseismic modeling is possible. By combining the oscillation spectrum from Kepler with high-resolution spectroscopy we measure an asteroseismic mass and age of 0.79+/-0.02(ran)+/-0.01(sys) Msun and 12.0+/-0.6(ran)+/-0.4(sys) Gyr, with remarkable agreement across different codes and input physics, demonstrating that stellar models and asteroseismology are reliable for very metal-poor stars when individual frequencies are used. The results also provide a direct age anchor for the early formation of the Milky Way, implying that substantial star formation did not commence until redshift z~3 (if the star formed in-situ) or that the Milky Way has undergone merger events for at least ~12 Gyr (if the star was accreted by a dwarf satellite merger such as Gaia Enceladus).

Low-luminosity AGNs with low-mass black holes (BHs) in the early universe are fundamental to understanding the BH growth and their co-evolution with the host galaxies. Utilizing JWST NIRCam Wide Field Slitless Spectroscopy (WFSS), we perform a systematic search for broad-line ${\rm H\alpha}$ emitters (BHAEs) at $z\approx 4-5$ in 25 fields of the ASPIRE (A SPectroscopic survey of biased halos In the Reionization Era) project, covering a total area of 275 arcmin$^2$. We identify 16 BHAEs with FWHM of the broad components spanning from $\sim$ 1000 km s$^{-1}$ to 3000 km s$^{-1}$. Assuming the broad linewidths arise due to Doppler broadening around BHs, the implied BH masses range from $10^7$ to $10^{8}~M_\odot$, with broad ${\rm H\alpha}$-converted bolometric luminosity of $10^{44.5}-10^{45.5}$ erg s$^{-1}$ and Eddington ratios of $0.07-0.47$. The spatially extended structure of the F200W stacked image may trace the stellar light from the host galaxies. The ${\rm H\alpha}$ luminosity function indicates an increasing AGN fraction towards the higher ${\rm H\alpha}$ luminosities. We find possible evidence for clustering of BHAEs: two sources are at the same redshift with a projected separation of 519 kpc; one BHAE appears as a composite system residing in an overdense region with three close companion ${\rm H\alpha}$ emitters. Three BHAEs exhibit blueshifted absorption troughs indicative of the presence of high-column-density gas. We find the broad-line and photometrically selected BHAE samples exhibit different distributions in the optical continuum slopes, which can be attributed to their different selection methods. The ASPIRE broad-line ${\rm H\alpha}$ sample provides a good database for future studies of faint AGN populations at high redshift.

The redshifted $21$\,cm signal of neutral hydrogen can be used as a direct probe of the intergalactic medium during Cosmic Dawn\,(CD) and Epoch of Reionization\,(EoR). However, detecting this inherently weak signal has numerous challenges. The major ones include accurate foreground removal from low-frequency radio observations and systematics arising from instrumental effects. The Earth's ionosphere poses a major obstacle at these low radio frequencies. Thus, a systematic study of ionospheric effects on these sensitive low-frequency observations is critical, given that the construction of the Square Kilometre Array (SKA1-Low) is in full progress. We use the end-to-end pipeline, called {\sc 21cme2e}, to study the effect of time-varying ionospheric corruption on the $21$\,cm power spectrum recovery. We use two models: a) a catalogue-based model focused on source position shift due to the refractive effect of the ionosphere and b) a realistic ionospheric condition generated using Kolmogorov's turbulence model. We assess the effect of the imperfections thus generated on the extraction of \HI\ $21$\,cm signal power spectrum. Our study shows that beyond ``median ionospheric offset" ($\theta_{\text{MIO}} \lesssim 0.1''$), the $21$\,cm signal from the EoR is unaffected by residual ionospheric effects. Our study emphasizes the need for the development of efficient ionospheric calibration algorithms for the upcoming SKA1-Low observations to extract the \HI\ $21$\,cm power spectra from the CD/EoR.

NGC 6357, a star-forming complex at $\sim 1.7$ kpc from the Sun, contains giant molecular clouds and three prominent star clusters alongside with HII regions, very massive stars and thousands of young stellar objects in different evolutionary stages. We present a combined infrared kinematic and time domain study of the line of sight towards this region enabled by the VVVX survey. In terms of kinematics, a novel discovery emerges: an asymmetrical distribution in the vector point diagram. Some stars in the sample exhibit spatial proximity to dusty regions, with their proper motions aligned with filament projections, hinting at a younger population linked to triggered star formation. However, this distribution could also stem from an asymmetric stellar expansion event within NGC 6357, warranting further investigation. Comparing this data with Gaia revealed inconsistencies likely due to high extinction levels in the region. Additionally, owing to accretion episodes and surface cool spots, young stars display high variability. Using the $K_s$-band time series data, we overcome the extreme levels of extinction towards the region, and compile a catalogue of $774$ infrared light curves of young stars. Each light curve has been characterized in terms of asymmetry and periodicity, to infer the dominant underlying physical mechanism. These findings are then correlated with evolutionary stages, aiming to uncover potential age disparities among the observed stars. This study contributes to our understanding the intricate dynamics and evolutionary processes within NGC 6357, offering valuable insights into the formation and development of stellar populations within such complex environments.

Small-scale winds driven from accretion discs surrounding active galactic nuclei (AGN) are expected to launch kpc-scale outflows into their host galaxies. However, the ways in which the structure of the interstellar medium (ISM) affects the multiphase content and impact of the outflow remains uncertain. We present a series of numerical experiments featuring a realistic small-scale AGN wind with velocity $5\times 10^3-10^4\ \rm{km/s}$ interacting with an isolated galaxy disc with a manually-controlled clumpy ISM, followed at sub-pc resolution. Our simulations are performed with AREPO and probe a wide range of AGN luminosities ($L=10^{43-47}\ \rm{erg/s}$) and ISM substructures. In homogeneous discs, the AGN wind sweeps up an outflowing, cooling shell, where the emerging cold phase dominates the mass and kinetic energy budgets, reaching a momentum flux $\dot{p} \approx 7\ L/c$. However, when the ISM is clumpy, outflow properties are profoundly different. They contain small, long-lived ($> 5\ \rm{Myr}$), cold ($T<10^{4.5}\ \rm{K}$) cloudlets entrained in the faster, hot outflow phase, which are only present in the outflow if radiative cooling is included in the simulation. While the cold phase dominates the mass of the outflow, most of the kinetic luminosity is now carried by a tenuous, hot phase with $T > 10^7 \ \rm K$. While the hot phases reaches momentum fluxes $\dot{p} \approx (1 - 5)\ L/c$, energy-driven bubbles couple to the cold phase inefficiently, producing modest momentum fluxes $\dot{p} < L/c$ in the fast-outflowing cold gas. These low momentum fluxes could lead to the outflows being misclassified as momentum-driven using common observational diagnostics. We also show predictions for scaling relations between outflow properties and AGN luminosity and discuss the challenges in constraining outflow driving mechanisms and kinetic coupling efficiencies using observed quantities.

The differential rotation plays a crucial role in the dynamics of the Sun. We study the solar rotation and its correlation with solar activity by applying a modified machine learning algorithm to identify and track coronal bright points (CBPs) from the Solar Dynamics Observatory/Atmospheric Imaging Assembly observations at 193 Å during cycle 24. For more than 321,440 CBPs, the sidereal and meridional velocities are computed. We find the occurring height of CBPs about 5627 km above the photosphere. We obtain a rotational map for the corona by tracking CBPs at the formation height of Fe\,{\sc xii} (193 Å) emissions. The equator rotation (14.$^{\circ}$40 to 14.$^{\circ}$54 day$^{-1}$) and latitudinal gradient of rotation ($ - $3.$^{\circ}$0 to $ - $2.$^{\circ}$64 day$^{-1}$) show very slightly positive and negative trends with solar activity (sunspots and flares), respectively. For cycle 24, our investigations show that the northern hemisphere has more differential rotation than the southern hemisphere, confirmed by the asymmetry of the midlatitude rotation parameter. The asymmetry (ranked) of the latitudinal gradient of the rotation parameter is concordant with the sunspot numbers for 7 yr within the 9 yr of the cycle; however, for only 3 yr, it is concordant with the flare index. The minimum horizontal Reynolds stress changes from about $ - $2500 m$^{2}$ s$^{-2}$ (corresponding to high activity) in 2012 and 2014 to $ - $100 m$^{2}$ s$^{-2}$ (corresponding to low activity) in 2019 over 5$^{\circ}$ to 35$^{\circ}$ latitudes within cycle 24. We conclude that the negative horizontal Reynolds stress (momentum transfer toward the Sun's equator) is a helpful indication of solar activity.

Cosmic rays (CRs) are the primary driver of ionization in star forming molecular clouds (MCs). Despite their potential impacts on gas dynamics and chemistry, no simulations of star cluster formation following the creation of individual stars have included explicit cosmic ray transport (CRT) to date. We conduct the first numerical simulations following the collapse of a $2000 M_{\odot}$ MC and the subsequent star formation including CRT using the STARFORGE framework implemented in the GIZMO code. We show that when CR-transport is streaming-dominated, the CR energy in the cloud is strongly attenuated due to energy losses from the streaming instability. Consequently, in a Milky Way like environment the median CR ionization rate (CRIR) in the cloud is low ($ \zeta \lesssim 2 \times 10^{-19} \rm s^{-1}$) during the main star forming epoch of the calculation and the impact of CRs on the star formation in the cloud is limited. However, in high-CR environments, the CR distribution in the cloud is elevated ($\zeta \lesssim 6 \times 10^{-18}$), and the relatively higher CR pressure outside the cloud causes slightly earlier cloud collapse and increases the star formation efficiency (SFE) by $50 \%$ to $\sim 13 \%$. The initial mass function (IMF) is similar in all cases except with possible variations in a high-CR environment. Further studies are needed to explain the range of ionization rates observed in MCs and explore star formation in extreme CR environments.

Recent observations have indicated a Cosmic Microwave Background (CMB) temperature decrement in the direction of local galaxies within the 2MASS Redshift Survey. We investigate this detection by analyzing its frequency dependence and sensitivity to component separation methods, suggesting that Galactic foregrounds are unlikely to be the cause. Contrary to previous studies, we find that the decrement is independent of galaxy type, indicating a possible correlation between the CMB and the overall matter density field. To test this hypothesis, we employ three analytical approaches: cross-correlation analysis, template fitting, and Bayes Factor calculation. Our cross-correlation analysis shows a significant correlation (p < 0.7%) between the CMB and the 2MASS Redshift Survey projected matter density at distances below 50 Mpc/h. Template fitting and Bayes Factor analyses support this finding, albeit with lower significance levels (1% - 5%). Importantly, we do not detect this signal beyond 50 Mpc/h, which constrains potential physical interpretations. We discuss that the physical origin of this correlation could potentially be linked to the dark matter distribution in the halos of galaxies. Further investigation is required to confirm and understand this intriguing connection between the CMB and local matter distribution.

Our recent work shows how M-Earth climates and transmission spectra depend on the amount of ice-free ocean on the planet's dayside and the mass of N2 in its atmosphere. M-Earths with more ice-free ocean and thicker atmospheres are hotter and more humid, and have larger water vapour features in their transmission spectra. In this paper, we describe a climate transition in high-pN2 simulations from the traditional ``eyeball" M-Earth climate, in which only the substellar region is temperate, to a ``temperate nightside" regime in which both the dayside and the nightside are entirely ice-free. Between these two states, there is a ``transition" regime with partial nightside ice cover. We use 3D climate simulations to describe the climate transition from frozen to deglaciated nightsides. We attribute this transition to increased advection and heat transport by water vapour in thicker atmospheres. We find that the nightside transitions smoothly back and forth between frozen and ice-free when the instellation or pCO2 is perturbed, with no hysteresis. We also find an analogous transition in colder planets: those with thin atmospheres can have a dayside hotspot when the instellation is low, whereas those with more massive atmospheres are more likely to be in the ``snowball" regime, featuring a completely frozen dayside, due to the increased advection of heat away from the substellar point. We show how both of these climate transitions are sensitive to instellation, land cover, and atmosphere mass. We generate synthetic transmission spectra and phase curves for the range of climates in our simulations.

Future millimeter wavelength experiments aim to both increase aperture diameters and broaden bandwidths to increase the sensitivity of the receivers. These changes produce a challenging anti-reflection (AR) design problem for refracting and transmissive optics. The higher frequency plastic optics require consistently thin polymer coats across a wide area, while wider bandwidths require multilayer designs. We present multilayer AR coats for plastic optics of the high frequency BICEP Array receiver (200-300 GHz) utilizing an expanded polytetrafluoroethylene (ePTFE) membrane, layered and compressively heat-bonded to itself. This process allows for a range of densities (from 0.3g/cc to 1g/cc) and thicknesses (>0.05mm) over a wide radius (33cm), opening the parameter space of potential AR coats in interesting directions. The layered ePTFE membrane has been combined with other polymer layers to produce band average reflections between 0.2% and 0.6% on high density polyethylene and a thin high modulus polyethylene window, respectively.

The UKIRT Hemisphere Survey covers the northern sky in the infrared from 0-60 degrees declination. Current data releases include both J and K bands, with H-band data forthcoming. Here we present a novel pipeline to recover asteroids from this survey data. We recover 26,138 reliable observations, corresponding to 23,399 unique asteroids, from these public data. We measure J-K colors for 601 asteroids. Our survey extends about two magnitudes deeper than 2MASS. We find that our small inner main belt objects are less red than larger inner belt objects, perhaps because smaller asteroids are collisionally younger, with surfaces that have been less affected by space weathering. In the middle and outer main belt, we find our small asteroids to be redder than larger objects in their same orbits, possibly due to observational bias or a disproportionate population of very red objects among these smaller asteroids. Future work on this project includes extracting moving object measurements from H and Y band data when it becomes available.

This study provides a continuous ephemeris reconstruction for comet 67P/Churyumov-Gerasimenko by reanalyzing Rosetta radiometric measurements and Earth-based astrometry. Given the comet-to-spacecraft relative trajectory provided by the navigation team, these measurements were used to estimate the comet state and some critical physical parameters, most notably the non-gravitational accelerations induced by the outgassing of surface volatiles, for which different models were tested and compared. The reference reconstructed ephemeris, which uses a stochastic acceleration model, has position uncertainties below 10 km, 30 km, and 80 km in the orbital radial, tangential, and normal directions for the whole duration of the Rosetta proximity phase (from July 2014 to October 2016). Furthermore, the solution can fit ground-based astrometry between March 2010 and July 2018, covering a complete heliocentric orbit of 67P. The estimated comet non-gravitational accelerations are dominated by the orbital radial and normal components, reaching peak values of $(1.28 \pm 0.17) \times 10^{-8} \, \text{m/s}^2$ and $(0.52 \pm 0.20) \times 10^{-8} \, \text{m/s}^2$, respectively 15 days and 24 days after perihelion. Furthermore, the acceleration magnitude is shown to have a steep dependence on the comet heliocentric distance $\text{NGA} \sim r_\odot^{-6}$ and shows asymmetries in the pre- and post-perihelion activities. The estimated acceleration components, agnostic due to the limited physical assumptions, could be used as a constraint for future investigations involving high-fidelity thermophysical models of the comet surface.

The fraction of white dwarfs found in wide binaries is estimated by cross referencing a catalogue of wide binaries with catalogues photometrically determined white-dwarf candidates and spectroscopically confirmed white dwarf stars. The wide-binary fraction of white dwarfs with hydrogen-dominated atmospheres is about 5%, but the fraction of white dwarfs with helium or carbon-dominated atmospheres is significantly larger. Using spectroscopic classifications, the binary fraction of DA white dwarfs is determined to be $0.063\pm0.002$ and for non-DA white dwarfs is larger at $0.080\pm0.004$.

To date, we have access to enormous inventories of stellar spectra that allow the extraction of atmospheric parameters and chemical abundances essential in stellar studies. However, characterizing such a large amount of data is complex and requires a good understanding of the studied object to ensure reliable and homogeneous results. In this study, we present a methodology to measure homogenously the basic atmospheric parameters and detailed chemical abundances of over 1600 thin disk main-sequence stars in the 100 pc solar neighborhood, using APOGEE-2 infrared spectra. We employed the code tonalli to determine the atmospheric parameters using a prior on log g. The log g prior in tonalli implies an understanding of the treated population and helps to find physically coherent answers. Our atmospheric parameters agree within the typical uncertainties (100 K in Teff, 0.15 dex in log g and $[M/H]$) with previous estimations of ASPCAP and Gaia DR3. We use our temperatures to determine a new infrared color-temperature sequence, in good agreement with previous works, that can be used for any main-sequence star. Additionally, we used the BACCHUS code to determine the abundances of Mg, Al, Si, Ca, and Fe in our sample. The five elements (Mg, Al, Si, Ca, Fe) studied have an abundance distribution centered around slightly sub-solar values, in agreement with previous results for the solar neighborhood. The over 1600 main-sequence stars atmospheric parameters and chemical abundances presented here are useful in follow-up studies of the solar neighborhood or as a training set for data-driven methods.

The element abundances of local group galaxies connect enrichment mechanisms to galactic properties and serve to contextualise the Milky Way's abundance distributions. Individual stellar spectra in nearby galaxies can be extracted from Integral Field Unit (IFU) data, and provide a means to take an abundance census of the local group. We introduce a program that leverages $R=1800$, $\mathrm{SNR}=15$, IFU resolved spectra from the Multi Unit Spectroscopic Explorer (MUSE). We deploy the data-driven modelling approach for labelling stellar spectra with stellar parameters and abundances, of The Cannon, on resolved stars in NGC 6822. We construct our model for The Cannon using $\approx$19,000 Milky Way LAMOST spectra with APOGEE labels. We report six inferred abundance labels (denoted $\ell_\mathrm{X}$), for 192 NGC 6822 disk stars, precise to $\approx$$0.15$ dex. We validate our generated spectral models provide a good fit the data, including at individual atomic line features. We infer mean abundances of $\ell_\mathrm{[Fe/H]} = -0.90 \pm 0.03$, $\ell_\mathrm{[Mg/Fe]} = -0.01 \pm 0.01$, $\ell_\mathrm{[Mn/Fe]} = -0.22 \pm 0.02$, $\ell_\mathrm{[Al/Fe]} = -0.33 \pm 0.03$, $\ell_\mathrm{[C/Fe]} =-0.43 \pm 0.03$, $\ell_\mathrm{[N/Fe]} =0.18 \pm 0.03$. These abundance labels are similar to dwarf galaxies observed by APOGEE, and the lower enhancements for NGC 6822 compared to the Milky Way are consistent with expectations. This approach supports a new era in extra-galactic archaeology of characterising the local group enrichment diversity using low-resolution, low-SNR IFU resolved spectra.

Bayesian inference for inverse problems hinges critically on the choice of priors. In the absence of specific prior information, population-level distributions can serve as effective priors for parameters of interest. With the advent of machine learning, the use of data-driven population-level distributions (encoded, e.g., in a trained deep neural network) as priors is emerging as an appealing alternative to simple parametric priors in a variety of inverse problems. However, in many astrophysical applications, it is often difficult or even impossible to acquire independent and identically distributed samples from the underlying data-generating process of interest to train these models. In these cases, corrupted data or a surrogate, e.g. a simulator, is often used to produce training samples, meaning that there is a risk of obtaining misspecified priors. This, in turn, can bias the inferred posteriors in ways that are difficult to quantify, which limits the potential applicability of these models in real-world scenarios. In this work, we propose addressing this issue by iteratively updating the population-level distributions by retraining the model with posterior samples from different sets of observations and showcase the potential of this method on the problem of background image reconstruction in strong gravitational lensing when score-based models are used as data-driven priors. We show that starting from a misspecified prior distribution, the updated distribution becomes progressively closer to the underlying population-level distribution, and the resulting posterior samples exhibit reduced bias after several updates.

VLT/UVES spectroscopic and TESS photometric observations for WASP 0346-21 allow the direct determination of its physical properties, along with the detection of a circumbinary object and oscillating signals. The high-resolution spectra yielded the radial velocities of all three stars and the atmospheric parameters of $T_{\rm eff,A}$ = 7225$\pm42$ K, [M/H] = 0.30$\pm$0.03 dex, and $v_{\rm A}$$\sin i$ = 78$\pm$5 km s$^{-1}$ of the primary component. The combined analysis of these observations resulted in the fundamental parameters of the eclipsing components and the third light of $l_3$ = 0.043$\pm$0.004, which is consistent with the light contribution of the tertiary star observed in the echelle spectra. WASP 0346-21 A resides within the overlapping main-sequence domain of $\delta$ Sct and $\gamma$ Dor variables, while the secondary component of $M_{\rm B}$ = 0.185$\pm$0.013 M$_\odot$, $R_{\rm B}$ = 0.308$\pm$0.023 R$_\odot$, $T_{\rm eff,B}$ = 10,655$\pm$146 K, and $L_{\rm B}$ = 1.09$\pm$0.17 L$_\odot$ matches well with the low-mass white dwarf (WD) model for $Z$ = 0.01, corresponding to the thick-disk population classified by the Galactic kinematics. Multifrequency analyses were performed on the residual TESS data after removing the binarity effects. The low frequencies around 26.348 day$^{-1}$ and 17.683 day$^{-1}$ are $\delta$ Sct pulsations originating from WASP 0346-21 A, and the high frequencies of 97.996 day$^{-1}$ and 90.460 day$^{-1}$ are considered to be extremely low-mass WD oscillations. These results demonstrate that WASP 0346-21 is a hierarchical triple system, consisting of an EL CVn binary with multiperiodic pulsations in each component and a distant outer tertiary.

We report the first observational evidence for magnetic field amplification in the north-east/south-west (NE/SW) shells of supernova remnant SN 1006, one of the most promising sites of cosmic ray (CR) acceleration. In previous studies, the strength of magnetic fields in these shells was estimated to be $B_{\rm SED}$ $\simeq$ 25$\mu$G from the spectral energy distribution, where the synchrotron emission from relativistic electrons accounted for radio to X-rays, along with the inverse Compton emission extending from the GeV to TeV energy bands. However, the analysis of broadband radio data, ranging from 1.37~GHz to 100~GHz, indicated that the radio spectrum steepened from $\alpha_1 = 0.52 \pm 0.02$ to $\alpha_2 = 1.34 \pm 0.21$ by $\Delta \alpha$ = 0.85 $\pm$ 0.21. This is naturally interpreted as a cooling break under strong magnetic field of $B_{\rm brk}$ $\ge$ 2~mG. Moreover, the high-resolution MeerKAT image indicated that the width of the radio NE/SW shells was broader than that of the X-ray shell by a factor of only 3$-$20, as measured by Chandra. Such narrow radio shells can be naturally explained if the magnetic field responsible for the radio emissions is $B_{\rm R}$ $\ge$ 2 mG. Assuming that the magnetic field is locally enhanced by a factor of approximately $a$ = 100 along the NE/SW shells, we argue that the filling factor, which is the volume ratio of such a magnetically enhanced region to that of the entire shell, must be as low as approximately $k$ = 2.5$\times$10$^{-5}$.

GLINT is a nulling interferometer downstream of the SCExAO extreme-adaptive-optics system at the Subaru Telescope (Hawaii, USA), and is a pathfinder instrument for high-contrast imaging of circumstellar environments with photonic technologies. GLINT is effectively a testbed for more stable, compact, and modular instruments for the era of 30m-class telescopes. GLINT is now undergoing an upgrade with a new photonic chip for more achromatic nulls, and for phase information to enable fringe tracking. Here we provide an overview of the motivations for the GLINT project and report on the design of the new chip, the on-site installation, and current status.

Pulsars have been primarily detected by their narrow pulses or periodicity in time domain data. Interferometric surveys for pulsars are challenging due to the trade-off between beam sensitivity and beam size and the corresponding tradeoff between survey sensitivity (depth), sky coverage, and computational efforts. The detection sensitivity of time-domain searches for pulsars is affected by dispersion smearing, scattering, and rapid orbital motion of pulsars in binaries. We have developed a new technique to select pulsar candidates in interferometric radio images by identifying scintillating sources and measuring their scintillation bandwidth and timescale. Identifying likely candidates allows sensitive, focused time-domain searches, saving computational effort. Pulsar scintillation is independent of its timing properties and hence offers a different selection of pulsars compared to time-domain searches. Candidates identified from this method could allow us to find hard-to-detect pulsars, such as sub-millisecond pulsars and pulsars in very compact, highly-accelerated binary orbits. We use uGMRT observations in the fields of PSR\,B1508+55, PSR\,J0437$-$4715, and PSR\,B0031$-$07 as test cases for our technique. We demonstrate that the technique correctly differentiates between the pulsar and other non-scintillating point sources and show that the extracted dynamic spectrum of the pulsar is equivalent to that extracted from the uGMRT phased array beam. We show the results from our analysis of known pulsar fields and discuss challenges in dealing with interference and instrumental effects.

In this study, we present an analysis of the archival X-ray data of the eclipsing supersoft X-ray binary CAL 87 observed with the {\it Chandra} Advanced CCD Imaging Spectrometer (ACIS) camera and Low Energy Transmission Grating (LETG) in 2001 August and with {\it XMM-Newton} in 2003 April. The high resolution X-ray spectra are almost unchanged in the two different dates. The average unabsorbed X-ray luminosity during the exposure was 4.64$-$5.46$\times10^{36}$ ergs s$^{-1}$ in 2001 and 4.54$-$4.82 $\times10^{36}$ ergs s$^{-1}$ in 2003, with prominent and red-shifted emission lines, mostly of nitrogen, oxygen, iron and argon, contributing to at least 30\% of the X-ray flux. The continuum X-ray flux is at least an order of magnitude too small for a hot, hydrogen burning WD. However, the continuum flux is consistent with Thomson-scattering reflecting about 5\% of the light of a hydrogen burning WD with effective temperature of 800,000 K, and a mass of $\sim$ 1.2 M$_\odot$. It has been noted before that a large Thomson-scattering corona explains the X-ray eclipse of CAL 87, in which the eclipsed region is found to be of size the order of a solar radius. The emission lines originate in an even more extended region, beyond the eclipsed central X-ray source; the emission spectrum is very complex, with unusual line ratios.

In this paper we construct a dissipative quintessential cosmic inflation. For this purpose, we add a multiplicative dissipative term in the standard quintessence field Lagrangian. We consider the specific form of dissipation as the time integral including the Hubble parameter and an arbitrary function that describes the dissipative properties of the quintessential scalar field. Inflation parameters and observables are calculated under slow-roll approximations and a detailed calculation of the cosmological perturbations is performed in this setup. We consider different forms of potentials and calculate the scalar spectral index and tensor-to-scalar ratio for a constant as well as variable dissipation function. To check the reliability of this model, a numerical analysis on the model parameters space is done in confrontation with recent observational data. By comparing the results with observational joint datasets at 68% and 95% confidence levels, we obtain some constraints on the model parameters space, specially the dissipation factor with e-folds numbers N = 55 and N = 60. As some specific results, we show that the power-law potential with a constant dissipation factor and N = 60 is mildly consistent with observational data in some restricted domains of the model parameter space with very small and negative dissipation factor and a negligible tensor-toscalar ratio. But this case with N = 55 is consistent with observation considerably. For power-law potential and variable dissipation factor as $Q = {\alpha}\phi^n$, the consistency with observation is also considerable with a reliable tensor-to-scalar ratio. The quadratic and quartic potentials with variable dissipation function as $Q = {\alpha}\phi^n$ are consistent with Planck2018 TT, TE, EE+lowE+lensing data at the 68% and 95% levels of confidence for some intervals of the parameter n.

We present a measurement of the mean absorption of cool gas traced by Mg II (${\lambda\lambda 2796, 2803}$) around emission line galaxies (ELGs), spanning spatial scales from 20 kpc to 10 Mpc. The measurement is based on cross-matching the positions of about 2.5 million ELGs at $z = 0.75-1.65$ and the metal absorption in the spectra of 1.4 million background quasars with data provided by the Year 1 sample of the Dark Energy Spectroscopic Instrument (DESI). The ELGs are divided into two redshift intervals: $0.75 < z < 1.0$ and $1.0 < z < 1.65$. We find that the composite spectra constructed by stacking the ELG-QSO pairs show evolution with redshift, with $z>1$ having a systematically higher signal of Mg II absorption. Within 1 Mpc, the covering fraction of the cool gas at $z > 1$ is higher than that of $z < 1$. The enhancement becomes less apparent especially if the projected distance $r_{p}>$1 Mpc. Also, ELGs with higher stellar mass and star formation rate (SFR) yield higher clustering of Mg II absorbers at $z<1$. For $z>1$, the covering fractions with different SFRs show little difference. The higher Mg II absorption at higher redshift also supports the observations of higher star formation at cosmic noon. Besides, the profile of Mg II absorption reveals a change of slope on scales of about 1 Mpc, consistent with the expected transition from a dark matter halo-dominated environment to a regime where clustering is dominated by halo-halo correlations. We estimate the cool gas density profile and derive the metal abundance at different redshifts. The growth of metal abundance suggests an increased presence of cool gas in the intergalactic medium (IGM) towards higher redshifts.

We present the detailed analysis of a new hybrid (p- and g-mode) sdB pulsator, TIC441725813 (TYC 4427-1021-1), discovered and monitored by TESS over 670 days. The TESS light curves available for this star were analysed using prewhitening techniques to extract mode frequencies accurately. The pulsation spectrum is then interpreted through methods that include asymptotic period spacing relationships and rotational multiplets identification. We also exploited a high signal-to-noise ratio (S/N), low-resolution spectrum of TIC441725813 using grids of non-local thermodynamic equilibrium (NLTE) model atmospheres to derive its atmospheric parameters. Interestingly, several frequency multiplets interpreted as rotational splittings of deep-probing g-modes indicate a slow rotation period of at least $85.3 \pm 3.6$ day, while splittings of mostly envelope-probing p-modes suggest a significantly shorter rotation period of $17.9 \pm 0.7$ day, which implies the core (mainly the helium mantle with possibly the deeper partially-mixed helium-burning core that it surrounds) rotates at least ~4.7 times slower than the envelope. The radial velocity curves indicate that TIC441725813 is in a close binary system with a low-luminosity companion, possibly a white dwarf. While elusive in the available TESS photometry, a low-frequency signal that would correspond to a period of $\sim 6.7$ h is found, albeit at low S/N. TIC441725813 is a particularly interesting sdB star whose envelope rotates faster than the core. We hypothesise that this might be caused by the effects of tidal interaction with a companion, although in the present case, the presence of such a companion will have to be further investigated. This analysis paves the way toward a more detailed seismic probing of TIC441725813 using optimisation techniques, which will be presented in a second paper.

NH$_{3}$(ammonia) plays a critical role in the chemistry of star and planet formation, yet uncertainties in its binding energy (BE) values complicate accurate estimates of its abundances. Recent research suggests a multi-binding energy approach, challenging the previous single-value notion. In this work, we use different values of NH$_{3}$ binding energy to examine its effects on the NH$_{3}$ abundances and, consequently, in the early evolution of protostellar cores. Using a gas-grain chemical network, we systematically vary the values of NH$_{3}$ binding energies in a model Class 0 protostellar core and study the effects of these binding energies on the NH$_{3}$ abundances. Our simulations indicate that abundance profiles of NH$_{3}$ are highly sensitive to the binding energy used, particularly in the warmer inner regions of the core. Higher binding energies lead to lower gas-phase NH$_{3}$ abundances, while lower values of binding energy have the opposite effect. Furthermore, this BE-dependent abundance variation of NH$_{3}$ significantly affects the formation pathways and abundances of key species such as HNC, HCN, and CN. Our tests also reveal that the size variation of the emitting region due to binding energy becomes discernible only with beam sizes of 10 arcsec or less. These findings underscore the importance of considering a range of binding energies in astrochemical models and highlight the need for higher resolution observations to better understand the subtleties of molecular cloud chemistry and star formation processes.

Solar wind modelling has become a crucial area of study due to the increased dependence of modern society on technology, navigation, and power systems. Accurate space weather forecasts can predict upcoming threats to Earth's geospace. In this study, we examine a novel full magnetohydrodynamic (MHD) chain from the Sun to Earth. The goal of this study is to demonstrate the capabilities of the full MHD modelling chain from the Sun to Earth by finalising the implementation of the full MHD coronal model into the COolfluid COroNa UnsTructured (COCONUT) model and coupling it to the MHD heliospheric model Icarus. The resulting coronal model has significant advantages compared to the pre-existing polytropic alternative, as it models a more realistic bi-modal wind, which is crucial for heliospheric studies. In this study, only thermal conduction, radiative losses, and approximated coronal heating function were considered in the energy equation. A realistic specific heat ratio was applied. The output of the coronal model was used to onset the 3D MHD heliospheric model Icarus. A minimum solar activity case was chosen as the first test case for the full MHD model. The numerically simulated data in the corona and the heliosphere were compared to observational products. We present a first attempt to obtain the full MHD chain from the Sun to Earth with COCONUT and Icarus. The coronal model has been upgraded to a full MHD model for a realistic bi-modal solar wind configuration. The approximated heating functions have modelled the wind reasonably well, but simple approximations are not enough to obtain a realistic density-speed balance or realistic features in the low corona and farther, near the outer boundary. The full MHD model was computed in 1.06 h on 180 cores of the Genius cluster of the Vlaams Supercomputing Center, which is only 1.8 times longer than the polytropic simulation.

We report a significantly tighter trend between gaseous N/O and $M_*/R_e$ (a proxy for gravitational potential) than has previously been reported between gaseous metallicity and $M_*/R_e$, for star-forming galaxies in the MaNGA survey. We argue this result to be a consequence of deeper potential wells conferring greater resistance to metal outflows while also being associated with earlier star-formation histories, combined with N/O being comparatively unaffected by metal-poor inflows. The potential-N/O relation thus appears to be both more resistant to short-timescale baryonic processes and also more reflective of a galaxy's chemical evolution state, when compared to previously-considered relations.

We explore the origin of the broad component of the [Ar II] 7 mcm line emission related to the ejecta excitation by the neutron star of SN 1987A. We argue that the line broad wings are emitted at the tmperature of $\sim300$ K. The flux excess in the red wing of [Ar II] line is reproduced by the line photons scattering off the optically thin uniform dust component with the grain size of 1 - 2 mcm and the total mass of $\mbox{(several)}\times10^{-3}\,M{\odot}$. The dusty opaque clumps containing almost all the dust of SN~1987A have a low occultation optical depth and line photon scattering on dusty clumps do not contribute noticeably in the red wing. The additional heating might be related to ionization losses of relativistic protons.

Chemical evolution models predict a gradual build-up of $^{13}$C in the universe, based on empirical nuclear reaction rates and assumptions on the properties of stellar populations. However, old metal-poor stars within the Galaxy contain more $^{13}$C than is predicted, suggesting that further refinements to the models are necessary. Gas at high redshift provides important supplementary information at metallicities $-2\lesssim$ [Fe/H] $\lesssim-1$, for which there are only a few measurements in the Galaxy. We obtained new, high-quality, VLT/ESPRESSO observations of the QSO B1331+170 and used them to measure $^{12}$C/$^{13}$C in the damped Lyman-$\alpha$ system (DLA) at $z_{abs}=1.776$, with [Fe/H]=-1.27. AI-VPFIT, an Artificial Intelligence tool based on genetic algorithms and guided by a spectroscopic information criterion, was used to explore different possible kinematic structures of the carbon gas. Three hundred independent AI-VPFIT models of the absorption system were produced using pre-set $^{12}$C/$^{13}$C values, ranging from 4 to 500. Our results show that $^{12}$C/$^{13}$C$=28.5^{+51.5}_{-10.4}$, suggesting a possibility of $^{13}$C production at low metallicity.

High energy electrons carry much of a solar flare's energy. Therefore, understanding changes in electron beam distributions during their propagation is crucial. A key focus of this paper is how the co-spatial return current reduces the energy flux carried by these accelerated electrons. We systematically compute this reduction for various beam and plasma parameters relevant to solar flares. Our 1D model accounts for collisions between beam and plasma electrons, return current electric-field deceleration, thermalization in a warm target approximation, and runaway electron contributions. The results focus on the classical (Spitzer) regime, offering a valuable benchmark for energy flux reduction and its extent. Return current losses are only negligible for the lowest nonthermal fluxes. We calculate the conditions for return current losses to become significant and estimate the extent of the modification to the beam's energy flux density. We also calculate two additional conditions which occur for higher injected fluxes: (1) where runaway electrons become significant, and (2) where current-driven instabilities might become significant, requiring a model that self-consistently accounts for them. Condition (2) is relaxed and the energy flux losses are reduced in the presence of runaway electrons. All results are dependent on beam and co-spatial plasma parameters. We also examine the importance of the reflection of beam electrons by the return-current electric field. We show that the interpretation of a number of flares needs to be reviewed to account for the effects of return currents.

In recent years, the topic of existence and exploration of exocomets has been gaining increasing attention. The asymmetrical decrease in the stellar brightness due to the passage of a comet-like object in front of the star was successfully predicted. It was subsequently confirmed on the basis of the light curves of stars observed by Kepler and TESS orbital telescopes. Since then, there have been successful attempts to fit the asymmetrical dips observed in the stellar light curves utilizing a simple 1D model of an exponentially decaying optically thin dust tail. In this work, we propose fitting the photometric profiles of some known exocomet transits based on a Monte Carlo approach to build up the distribution of dust particles in a cometary tail. As the exocomet prototypes, we used the physical properties of certain Solar System comets belonging to the different dynamical groups and moving at heliocentric distances of 0.6 au, 1.0 au, 5.0 au, and 5.5 au. We obtained a good agreement between the observed and modeled transit light curves. We also show that the physical characteristics of dust particles, such as the particle size range, the power index of dust size distribution, the particle terminal velocity, and distance to the host star affect the shape of the transit light curve, while the dust productivity of the comet nucleus and the impact parameter influence its depth and duration. The estimated dust production rates of the transiting exocomets are at the level of the most active Solar System comets.

The degree of Gaussianity of a field offers insights into its cosmological nature, and its statistical properties serve as indicators of its Gaussianity. In this work, we examine the signatures of Gaussianity in a gravitational wave background (GWB) by analyzing the cumulants of the one- and two-point functions of the relevant observable, using pulsar timing array (PTA) simulations as a proof-of-principle. This appeals to the ongoing debate about the source of the spatially-correlated common-spectrum process observed in PTAs, which is likely associated with a nanohertz stochastic GWB. We investigate the distribution of the sample statistics of the one-point function in the presence of a Gaussian GWB. Our results indicate that, within PTAs, one-point statistics are impractical for constraining the Gaussianity of the nanohertz GWB due to dominant pulsar noises. However, our analysis of two-point statistics shows promise, suggesting that it may be possible to constrain the Gaussianity of the nanohertz GWB using PTA data. We also emphasize that the Gaussian signatures identified in the one- and two-point functions in this work are expected to be applicable to any gravitational wave background.

Recently, we constructed the specific solution to the second-order cosmological perturbation theory, around any Friedmann-Lemaitre-Robertson-Walker (FLRW) background filled with dust matter and a positive cosmological constant. In this paper, we use the Cosmicflows-4 (CF4) sample of galaxies from the Extragalactic Distance Database to constrain this metric tensor. We obtain an approximation to the local matter distribution and geometry. We numerically solve for null geodesics for randomly distributed mock sources and compare this model with the Lemaitre-Hubble constant inferred from the observations under the assumption of perfect isotropy and homogeneity. We conclude on effects of realistic inhomogeneities on the luminosity distance in the context of the Hubble tension and discuss limitations of our approach.

Nonlinear simulations of neutron star mergers are complicated by the need to represent turbulent dynamics. As we cannot (yet) perform simulations that resolve accurately both the gravitational-wave scale and the smallest scales at which magneto/hydrodynamic turbulence plays a role, we need to rely on approximations. Addressing this problem in the context of large-eddy models, we outline a coherent Lagrangian filtering framework that allows us to explore the many issues that arise, linking conceptual problems to practical implementations and the interpretation of the results. We develop understanding crucial for quantifying unavoidable uncertainties in current and future numerical relativity simulations and consider the implications for neutron-star parameter estimation and constraints on the equation of state of matter under extreme conditions.

The very late thermal pulse (VLTP) affects the evolution of $\sim$20\% of 1--8\,$\mathrm M_\odot$ stars, repeating the last phases of the red giant within a few years and leading to the formation of a new, but hydrogen-poor nebula within the old planetary nebula (PN). The strong dust formation in the latter obscures the optical and near-infrared radiation of the star. We aimed to determine the reheating timescale of the central star in Sakurai's object, which is an important constraint for the poorly understood VLTP evolution. We observed the radio continuum emission of Sakurai's object for almost 20 years from 2004 to 2023. Continuous, multi-frequency observations proved to be essential to distinguish between phases dominated by photoionization and shock ionization. The flux density fluctuates by more than a factor 40 within months to years. The spectral index remained negative between 2006 and 2017 and is close to zero since 2019. The emission region is barely resolved since 2021. Non-thermal radio emission observed from 2004 to 2017 traces shocks induced by wind interactions due to discrete mass-loss events. Thermal emission dominates during the period 2019--2023 and may indicate photoionization of the nebula by the central star.

In this paper, we investigate a cosmological model based on viscous $f(R,T)$ gravity as a potential alternative to dark energy. This model incorporates bulk viscosity and is analyzed using an effective equation of state. We consider the simplest specific model, $f(R,T)=R+\lambda T$, where $\lambda$ is a constant. The exact solution of our viscous $f(R,T)$ cosmological model is derived, and then we use the combined datasets consisting of 31 $H(z)$ data points and 1701 Pantheon+ SNe data points to determine the best-fit values of the model parameters. We find good agreement with observations, particularly at higher redshifts. Our model's behavior, including energy density, pressure with viscosity, effective equation of state, and deceleration parameter, is analyzed. It indicates a shift from decelerated to accelerated phases of the universe's expansion, suggesting that bulk viscosity in the cosmic fluid could effectively generate the negative pressure necessary for cosmic expansion. Finally, we explore statefinder diagnostics to differentiate between various dark energy models, revealing that our model resides in the quintessence region.

Surface albedo is an important parameter in radiative transfer simulations of the Earth's system, as it is fundamental to correctly calculate the energy budget of the planet. The Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on NASA's Terra and Aqua satellites continuously monitor daily and yearly changes in reflection at the planetary surface. The MODIS Surface Reflectance black-sky albedo dataset (MCD43D, version 6.1) gives detailed albedo maps in seven spectral bands in the visible and near-infrared range. These albedo maps allow us to classify different Lambertian surface types and their seasonal and yearly variability and change, albeit only in seven spectral bands. However, a complete set of albedo maps covering the entire wavelength range is required to simulate radiance spectra, and to correctly retrieve atmospheric and cloud properties from Earth's remote sensing. We use a Principal Component Analysis (PCA) regression algorithm to generate hyperspectral albedo maps of Earth. Combining different datasets of hyperspectral reflectance laboratory measurements for various dry soils, vegetation surfaces, and mixtures of both, we reconstruct the albedo maps in the entire wavelength range from 400 to 2500~nm. The PCA method is trained with a 10-years average of MODIS data for each day of the year. We obtain hyperspectral albedo maps with a spatial resolution of 0.05° in latitude and longitude, a spectral resolution of 10~nm, and a temporal resolution of 1~day. Using the hyperspectral albedo maps, we estimate the spectral profiles of different land surfaces, such as forests, deserts, cities and icy surfaces, and study their seasonal variability. These albedo maps shall enable to refine calculations of Earth's energy budget, its seasonal variability, and improve climate simulations.

4U 1954+31 is a high-mass X-ray binary (HMXB) that contains a neutron star and an M supergiant companion. The neutron star has a spin period of ~5.4 hr. The traditional wind-accreting model requires an ultra-strong magnetic field for the neutron star to explain its extremely long spin period, which seems problematic for the neutron star with an age of a few tens of million years. In this work, we take into account the unsteady feature of wind accretion, which results in alternation of the direction of the wind matter's angular momentum. Accordingly, the torque exerted by the accreted wind matter varies between positive and negative from time to time, and largely cancels out over long time. In such a scenario, neutron stars can naturally attain long spin periods without the requirement of a very strong magnetic field. This may also provide a reasonable explanation for the spin period distribution of long-period neutron stars in HMXBs.

The recent observation of the GW230529 event indicates that black hole-neutron star binaries can contain low-mass black holes. Since lower mass systems are more favourable for tidal disruption, such events are promising candidates for multi-messenger observations. In this study, we employ five finite-temperature, composition-dependent matter equations of state and present results from ten 3D general relativistic hydrodynamic simulations for the mass ratios $q = 2.6$ and $5$. Two of these simulations target the chirp mass and effective spin parameter of the GW230529 event, while the remaining eight contain slightly higher-mass black holes, including both spinning ($a_{BH} = 0.7$) and non-spinning ($a_{BH} = 0$) models. We discuss the impact of the equation of state, spin, and mass ratio on black hole-neutron star mergers by examining both gravitational-wave and ejected matter properties. For the low-mass ratio model we do not see fast-moving ejecta for the softest equation of state model, but the stiffer model produces on the order of $10^{-6}M_\odot$ of fast-moving ejecta, expected to contribute to an electromagnetic counterpart. Notably, the high-mass ratio model produces nearly the same amount of total dynamical ejecta, but yields $52$ times more fast-moving ejecta than the low-mass ratio system. In addition, we observe that the black-hole spin tends to decrease the amount of fast-moving ejecta while increasing significantly the total ejected mass. Finally, we note that the disc mass tends to increase as the neutron star compactness decreases.

The recent DESI Baryon Acoustic Oscillation measurements have led to tight upper limits on the neutrino mass sum, potentially in tension with oscillation constraints requiring $\sum m_{\nu} \gtrsim 0.06\,{\text{eV}}$. Under the physically motivated assumption of positive $\sum m_{\nu}$, we study the extent to which these limits are tightened by adding other available cosmological probes, and robustly quantify the preference for the normal mass ordering over the inverted one, as well as the tension between cosmological and terrestrial data. Combining DESI data with Cosmic Microwave Background measurements and several late-time background probes, the tightest $2\sigma$ limit we find without including a local $H_0$ prior is $\sum m_{\nu}<0.05\,{\text{eV}}$. This leads to a strong preference for the normal ordering, with Bayes factor relative to the inverted one of $46.5$. Depending on the dataset combination and tension metric adopted, we quantify the tension between cosmological and terrestrial observations as ranging between $2.5\sigma$ and $5\sigma$. These results are strenghtened when allowing for a time-varying dark energy component with equation of state lying in the physically motivated non-phantom regime, $w(z) \geq -1$, highlighting an interesting synergy between the nature of dark energy and laboratory probes of the mass ordering. If these tensions persist and cannot be attributed to systematics, either or both standard neutrino (particle) physics or the underlying cosmological model will have to be questioned.

The origin of warm ions in the circum-galactic medium (CGM) surrounding massive galaxies remains a mystery. In this paper, we argue that a significant fraction of the observed warm-ion columns may arise in the intergalactic medium (IGM) surrounding galactic halos. We use a simple spherical collapse model of the dark matter (DM) halos and their baryonic content to compute the evolving ion fractions within and outside virial halos. We show that the photoionized IGM may produce a thick blanket of warm ions around the CGM, thereby contaminating CGM observations. We find that the IGM contributes $> 75\%$ of the total \ion{O}{6} column densities in halos with virial masses exceeding a few times $10^{11}~M_\odot$, and that it may dominate the \ion{O}{6} absorption even for lower mass-halos, depending on the impact parameter. We compare our results with observations and find that our simplified model reproduces the overall \ion{O}{6} columns as well as their trend with the impact parameter and halo mass. We show that observed warm ion columns may be completely dominated by the IGM envelopes, consistent with CGM$^2$ data. We, therefore, suggest that theoretical interpretations of CGM-survey observations must consider the possible contribution of the surrounding IGM. Although our simplified model suggests that it may be possible to kinematically distinguish between CGM and IGM origins through the absorption line profiles, this distinction is likely unfeasible in realistic astrophysical halos, due to the complex velocity structure in the multi-phased CGM.

We report evidence for enhanced quenching in low-redshift galaxy clusters hosting radio relics. This effect is strongest for low-mass galaxies and is consistent with a rapid quenching of star formation. These results imply that merger shocks in the intracluster medium play a role in driving environmental quenching, which we argue is due to the elevated ram pressure experienced by satellite galaxies in these disturbed systems.

Time-domain astrophysics has leaped forward with the direct discovery of gravitational waves and the emergence of new generation instruments for multi-messenger studies. The capacity of the multi-messenger multi-wavelength community to effectively pursue follow-up observations is hindered by the suboptimal localization of numerous transient events and the escalating volume of alerts. Thus, we have developed an effective tool to overcome the observational and technical hurdles inherent in the emerging field of multi-messenger astrophysics. We present tilepy, a Python package for the automatic scheduling of follow-up observations of poorly localized transient events. It is ideally suited to tackle the challenge of complex follow-up in mid and small-FoV telescope campaigns, with or without human intervention. We demonstrate the capabilities of tilepy in the realm of multi-observatory, multi-wavelength campaigns, to cover the localization uncertainty region of various events ultimately aiming at pinpointing the source of the multi-messenger emission. The tilepy code is publicly available on GitHub and is sufficiently flexible to be employed either automatically or in a customized manner, tailored to collaboration and individual requirements. tilepy is also accessible via a public API and through the Astro-COLIBRI platform.

We consider the possibility that the cosmic neutrino background might have a nonthermal spectrum, and investigate its effect on cosmological parameters relative to standard $\Lambda$-Cold Dark Matter ($\Lambda$CDM) cosmology. As a specific model, we consider a thermal $y$-distortion, which alters the distribution function of the neutrino background by depleting the population of low-energy neutrinos and enhancing the high-energy tail. We constrain the thermal $y$-parameter of the cosmic neutrino background using Cosmic Microwave Background (CMB) and Baryon Acoustic Oscillation (BAO) measurements, and place a $95\%$-confidence upper bound of $y \leq 0.043$. The $y$-parameter increases the number of effective relativistic degrees of freedom, reducing the sound horizon radius and increasing the best-fit value for the Hubble constant $H_0$. We obtain an upper bound on the Hubble constant of $H_0 = 71.12\ \mathrm{km/s/Mpc}$ at $95\%$ confidence, substantially reducing the tension between CMB/BAO constraints and direct measurement of the expansion rate from Type-Ia supernovae. Including a spectral distortion also allows for a higher value of the spectral index of scalar fluctuations, with a best-fit of $n_{\mathrm{S}} = 0.9720 \pm 0.0063$, and a $95\%$-confidence upper bound of $n_{\mathrm{S}} \leq 0.9842$.

Spaced-based mirrors are a developing use-case for Additive Manufacturing (AM), the process that builds a part layer-by-layer. The increased geometric freedom results in novel and advantageous designs previously unachievable. Conventionally, mirror fabrication uses subtractive (milling & turning), formative (casting) and fabricative (bonding) manufacturing methods; however, an additive method can simplify an assembly by consolidating individual components into one, and incorporating lattice structures and function optimised geometries to reduce the mass of components, which are beneficial to space-based instrumentation as mass and volume are constrained. Attention must be given to the printability of the design - build orientation and powder/resin removal from lattices and internal cavities are challenges when designing for AM. This paper will describe the design, manufacture and metrology of mirror prototypes from the Active Deployable Optical Telescope (ADOT) 6U CubeSat project. The AM mirror is 52mm in diameter, 10mm deep, with a convex 100mm radius of curvature reflective surface and deploys telescopically on three booms. The objectives of the designs were to combine the boom mounting features into the mirror and to lightweight both prototypes by 50% and 70% using internal, thin-walled lattices. Four final lattice designs were downselected through simulation and prototype validation. Prototypes were printed in the aluminium alloy AlSi10Mg using powder bed fusion and fused silica using stereolithography. Aluminium mirrors were single point diamond turned and had surface roughness measurements taken. Fused silica designs were adapted from the aluminium designs and have completed printing.

Carbon abundances in first-ascent giant stars are usually lower than those of their main-sequence counterparts. At moderate metallicities, stellar evolution of single stars cannot account for the existence of red-giant branch stars with enhanced carbon abundances. The phenomenon is usually interpreted as resulting from past mass transfer from an evolved binary companion now in the white dwarf evolutionary stage. Aims: We aim to confirm the links between [C/O] enhancement, s-process element enhancement and binary fraction using large-scale catalogues of stellar abundances and probable binary stars. Methods: We use a large data set from the 17 data release of the SDSS-IV/APOGEE~2 survey to identify carbon-enhanced stars in the Galactic disk. We identify a continuum of carbon enrichment throughout three different sub-populations of disk stars and explore links between the degree of carbon enrichment and binary frequency, metallicity and chemical compositions. Results: We verify a clear correlation between binary frequency and enhancement in the abundances of both carbon and cerium, lending support to the scenario whereby carbon-enhanced stars are the result of mass transfer by an evolved binary companion. In addition, we identify clustering in the carbon abundances of high-$\alpha$ disk stars, suggesting that those on the high metallicity end are likely younger, in agreement with theoretical predictions for the presence of a starburst population following the gas-rich merger of the Gaia-Enceladus/Sausage system.

The kinematics of the young stellar association near the Sun TW Hya is studied. Kinematic estimates of the age of this association were obtained in two ways. The first method -- analysis of stellar trajectories integrated back in time -- gave an estimate of the age $t=4.9\pm1.2$ Myr. The second was to analyze the instantaneous velocities of stars and showed that there is a volume expansion of the stellar system with an angular velocity coefficient $K_{xyz}=103\pm12$ km s$^{-1}$ kpc$^{-1}$. Based on this effect, the time interval that passed from the beginning of the expansion of the TW Hya association to the present moment was found, $t=9.5\pm1.1$ Myr. The following principal semi-axes of the residual velocity ellipsoid are determined: $\sigma_{1,2,3}=(5.25,1.84,0.35)\pm(0.34,0.63,0.26)$ km s$^{-1}$.

If a planetary nebula (PN) is shown to be a member of a star cluster, we obtain important new constraints on the mass and chemical composition of the PN's progenitor star, which cannot be determined for PNe in the field. Cluster membership can be tested by requiring the projected separation between the PN and cluster to be within the tidal radius of the cluster, and the objects to have nearly identical radial velocities (RVs) and interstellar extinctions, and nearly identical proper motions (PMs). In an earlier study, we used PMs to confirm that three PNe, which had already passed the other tests, are highly likely to be members of Galactic globular clusters (GCs). For a fourth object, the PN JaFu 1, which lies in the Galactic bulge near the GC Palomar 6 on the sky and has a similar RV, the available PM measurement gave equivocal results. We have now obtained new high-resolution images of the central star of JaFu 1 with the Hubble Space Telescope (HST) which, combined with archival HST frames taken 14 and 16 years earlier, provide a high-precision PM. Unfortunately, we find that the PM of the central star differs from that of the cluster with high statistical significance, and thus is unlikely to be a member of Palomar 6. Nevertheless, JaFu 1 is of astrophysical interest because its nucleus appears to be a member of the rare class of "EGB 6-type" central stars, which are associated with compact emission-line knots.

The 21-cm forest is a sensitive probe for the early heating process and small-scale structures during the epoch of reionization (EoR), to be realized with the upcoming Square Kilometre Array (SKA). Its detection relies on the availability of radio-bright background sources, among which the radio-loud quasars are very promising, but their abundance during the EoR is still poorly constrained due to limited observations. Here, we use a physics-driven model to forecast future radio-loud quasar observations. We fit the parameters of the model using observational data of high-redshift quasars. Assuming Eddington accretion, the model yields an average lifetime of $t_{\rm q} \sim 10^{5.3}$yr for quasars at $z\sim6$, consistent with recent results obtained from quasar proximity zone pre-study. We show that if the radio-loud fraction of quasars evolves with redshift, it will significantly reduce the abundance of observable radio-loud quasars in the SKA era, making 21-cm forest studies challenging. With a constant radio-loud fraction, our model suggests that a one-year sky survey conducted with SKA-LOW has the capability to detect approximately 20 radio-loud quasars at $z\sim 9$, with sufficient sensitivity to resolve individual 21-cm forest lines.

Coronal mass ejections (CMEs) are powerful drivers of space weather, with magnetic flux ropes (MFRs) widely regarded as their primary precursors. However, the variation in reconnection flux during the evolution of MFR during CME eruptions remains poorly understood. In this paper, we develop a realistic 3D magneto-hydrodynamic model using which we explore the temporal evolution of reconnection flux during the MFR evolution using both numerical simulations and observational data. Our initial coronal configuration features an isothermal atmosphere and a potential arcade magnetic field beneath which an MFR emerges at the lower boundary. As the MFR rises, we observe significant stretching and compression of the overlying magnetic field beneath it. Magnetic reconnection begins with the gradual formation of a current sheet, eventually culminating with the impulsive expulsion of the flux rope. We analyze the temporal evolution of reconnection fluxes during two successive MFR eruptions while continuously emerging the twisted flux rope through the lower boundary. We also conduct a similar analysis using observational data from the Helioseismic and Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA) for an eruptive event. Comparing our MHD simulation with observational data, we find that reconnection flux play a crucial role in determination of CME speeds. From the onset to the eruption, the reconnection flux shows a strong linear correlation with the velocity. This nearly realistic simulation of a solar eruption provides important insights into the complex dynamics of CME initiation and progression.

Astrophysical emission lines arising from particle decays can offer unique insights into the nature of dark matter (DM). Using dedicated simulations with background and foreground modeling, we comprehensively demonstrate that the recently launched XRISM space telescope with powerful X-ray spectroscopy capabilities is particularly well-suited to probe decaying DM, such as sterile neutrinos and axion-like particles, in the mass range of few to tens of keV. We analyze and map XRISM's DM discovery potential parameter space by considering Milky Way Galactic DM halo, including establishing an optimal line-of-sight search, as well as dwarf galaxies where we identify Segue 1 as a remarkably promising target. We demonstrate that with only 100 ks exposure XRISM/Resolve instrument is capable of probing the underexplored DM parameter window around few keV and testing DM couplings with sensitivity that exceeds by two orders existing Segue 1 limits. Further, we demonstrate that XRISM/Xtend instrument sensitivity enables discovery of the nature of faint astrophysical X-ray sources, especially in Segue 1, which could shed light on star-formation history. We discuss implications for decaying DM searches with improved detector energy resolution in future experiments.

It has now been just over four decades since the first discovery of a millisecond spin period pulsar (MSP), B1937+21, by Don Backer and collaborators in late 1982. This finding of an entirely new class of astronomical object revolutionized pulsar astronomy and provided inspiration for novel scientific investigation for decades to come, continuing to the current day and beyond. Here we review the events leading to the discovery, based on archival material, personal correspondence, and first-hand accounts of several of the participants. We also briefly review the enormous impact that MSPs have had on physics and astronomy by highlighting major MSP-related science of the past 40 years.

The NASA Standard Break-Up Model models collisions and explosions in space, which identifies the future distribution of debris. Given a possible break-up event, this work analyses the threat posed by the generated debris in the orbit of an asset spacecraft. Using the Koopman Operator solution of the $J_2$ perturbed two-body dynamics, the family of all possible orbits that cross the asset's pathway is identified and parameterized according to their velocity. The threat level assessment of a collision onto the asset is estimated considering the intersection between the velocities of the break-up model and the Koopman transfer solutions.

The proper elements of asteroids are obtained from the instantaneous orbital elements by removing periodic oscillations produced by gravitational interactions with planets. They are unchanging in time, at least if chaotic dynamics and non-gravitational forces could be ignored, and can therefore be used to identify fragments of major collisions (asteroid families) that happened eons ago. Here we present a new catalog of proper elements for 1.25 million main belt asteroids. We explain the methodology, evaluate uncertainties, and discuss how the new catalog can be used to identify asteroid families. A systematic search for families yielded 153 cases not reported in Nesvorný at al. (2015) -- 17 of these cases were identified in various other publications, 136 cases are new discoveries. There are now 274 families in the asteroid belt in total (plus a handful of families in the resonant Hilda population). We analyzed several compact families in detail. The new family around the middle belt asteroid (9332) 1990SB1 (9 members) is the youngest family found so far (estimated formation only 16-17 kyr ago). New families (1217) Maximiliana, (6084) Bascom, (10164) Akusekijima and (70208) 1999RX33 all formed 0.5-2.5 Myr ago. The (2110) Moore-Sitterly family is a close pair of relatively large bodies, 2110 and 44612, and 15 small members all located sunwards from 2110 and 44612, presumably a consequence of the Yarkovsky drift over the estimated family age (1.2-1.5 Myr). A systematic characterization of the new asteroid families is left for future work.

Boyle and Turok's $CPT$-symmetric universe model posits that the universe was symmetric at the Big Bang, addressing numerous problems in both cosmology and the Standard Model of particle physics. We extend this model by considering the symmetric conditions at the end of the Universe, following Lasenby et al. by imposing constraints on the allowed perturbation modes. These constrained modes conflict with the integer wave vectors required by the global spatial geometry in a closed universe. To resolve this conflict, only specific values of curvature are permissible, and in particular the curvature density is constrained to be $\Omega_K \in \{-0.014, -0.009, -0.003, \ldots\}$, consistent with Planck observations.

Studying the structures (halos and galaxies) within the cosmic environments (void, sheet, filament, and node) where they reside is an ongoing attempt in cosmological studies. The link between the properties of structures and the cosmic environments may help to unravel the nature of the dark sector of the Universe. In this paper, we study the cosmic web environments from the spatial pattern perspective in the context of $ \Lambda $CDM and $ \nu \Lambda $CDM as an example of an extension to the vanilla model. To do this, we use the T-web classification method and classify the cosmic environments for the catalogues from the gevolution N-body simulations for $ \Lambda $CDM and $ \nu \Lambda $CDM cosmology. Then, we compute the first nearest neighbour cumulative distribution function, spherical contact cumulative distribution function, and $ J$-function for every cosmic environment. In the context of the standard model, the results indicate that these functions can differentiate the various cosmic environments. In association with distinguishing between extensions of the standard model of cosmologies, these functions within the cosmic environment seem beneficial as a complementary probe.

Degenerate Higher Order Scalar Tensor (DHOST) theories are the most general scalar-tensor theories whose Lagrangian depends on the metric tensor and a single scalar field and which propagate only one scalar degree of freedom, without being plagued by Ostrogradsky instabilities. This is achieved through certain degeneracies of the functions forming their Lagrangian. They generalise the Horndeski and beyond-Horndeski theories. Originally build to describe the late-time acceleration of the expansion of the universe, generalising the cosmological constant, they can be used to build models for early universe, to describe inflation or alternatives to standard inflation. In the late universe, they modify the standard Vainstein screening mechanism from Horndeski theories which can have observable consequences and are suited to build black hole models, featuring non-stealth Kerr black hole solutions. In this work we review their effects on cosmology, looking at their basic properties, their parameterisations and classifications, and then focusing on solutions in the early and the late universe.

One of the fundamental characteristics of slow roll inflation is its generation of tensor perturbations, which manifest as stochastic gravitational waves (GWs). Slow roll inflation results in a nearly scale-invariant GW spectrum that maintains its scale invariance as it transitions into the radiation-dominated era. However, introducing an intermediate reheating phase can modify the spectral tilt, depending on the equation of state governing that particular epoch. These GWs, especially on smaller scales, are anticipated to be observable by forthcoming GW detectors. In this study, we initially delineate the parameter space encompassing the inflationary energy scale, reheating temperature, and equation of state in a model-independent manner, focusing on the spectra detectable by GW detectors such as LISA, ET, DECIGO, and BBO. We also examine the implications for the $\alpha$-attractor model of inflation and explore the observational constraints on $n_s-r$ prediction in the light of GW detection. Then, we point out the probable ranges for various non-gravitational and gravitational coupling between the inflaton and Standard Model particles considering the perturbative reheating. If one assumes PBHs were formed during the early reheating era, such detection of GW signal also sheds light on the probing PBH parameters. Note that for the case of PBH domination, we also consider the contribution of the induced GW due to the density function in PBH distribution, which helps to decode the phase of early PBH domination. Finally, to test the production of other cosmological relics through future GW missions, we consider dark matter produced via gravitational interaction in the early universe.

We consider Dark Matter self-interactions mediated by ultralight scalars. We show that effectively massless mediators lead to an enhancement of the matter power spectrum, while heavier mediators lead to a suppression, together with a feature around their Jeans scale. We derive the strongest present constraints by combining Planck and BOSS data. The recent DESI measurements of Baryon Acoustic Oscillations exhibit a mild preference for long-range self-interactions, as strong as 4 per mille of the gravitational coupling. Forthcoming data from DESI itself and Euclid will confirm or disprove such a hint.