Papers for Monday, Jan 27 2025

We present new theoretical light curves in the Rubin-LSST filters for a fine grid of BL Her models computed using MESA-RSP. We also derive new theoretical period-luminosity (PL) and period-Wesenheit (PW) relations in the Rubin-LSST filters with the goal to study the effect of convection parameters and metallicity on these relations. The grid of BL Her models was computed with the input stellar parameters: metallicity ($-2.0\; \mathrm{dex} \leq \mathrm{[Fe/H]} \leq 0.0\; \mathrm{dex}$), stellar mass ($0.5M_{\odot}-0.8M_{\odot}$), stellar luminosity ($50L_{\odot}-300L_{\odot}$), and effective temperature (across the full extent of the instability strip; in steps of 50K) and using four sets of convection parameters. Bolometric correction tables from MIST were used to transform the theoretical bolometric light curves of the BL Her models into the Rubin-LSST ugrizy filters. The PL relations of the BL Her models exhibit steeper slopes but smaller dispersion with increasing wavelengths in the Rubin-LSST filters. The PL and PW slopes for the complete set of BL Her models computed with radiative cooling (sets B and D) are statistically similar across the grizy filters. The BL Her models exhibit weak or negligible effect of metallicity on the PL relations for wavelengths longer than the g filter for both the cases of the complete set of models as well as the low-mass models. However, we find significant effect of metallicity on the PL relation in the u filter. Strong metallicity effects are observed in the PWZ relations involving the u filter and are found to have significant contribution from the high-metallicity BL Her models. Due to negligible metallicity effect for relations involving the Wesenheit indices $W(i,g-i)$, $W(z,i-z)$ and $W(y,g-y)$, we recommend these filter combinations for BL Her stars when observed with the Rubin-LSST to be used as reliable standard candles.

Highly-irradiated gas giant exoplanets are predicted to show circulation patterns dominated by day-to-night heat transport and a spatial distribution of clouds that is driven by advection and local heating. Hot-Jupiters have been extensively studied from broadband phase-curve observations at infrared and optical wavelengths, but spectroscopic observations in the reflected light are rare and the regime of smaller and higher-metallicity ultra-hot planets, such as hot-Neptunes, remains largely unexplored to date. Here we present the phase-resolved reflected-light and thermal-emission spectroscopy of the ultra-hot Neptune LTT 9779b, obtained through observing its full phase-curve from 0.6 to 2.8 $\mu$m with JWST NIRISS/SOSS. We detect an asymmetric dayside in reflected light (3.1$\sigma$ significance) with highly-reflective white clouds on the western dayside (A = 0.79$\pm$0.15) and a much lower-albedo eastern dayside (A = 0.41$\pm$0.10), resulting in an overall dayside albedo of A = 0.50$\pm$0.07. The thermal phase curve is symmetric about the substellar point, with a dayside effective temperature of T$_\mathrm{eff,day}$ = 2,260$^{+40}_{-50}$ K and a cold nightside (T$_\mathrm{eff,night}$ <1,330 K at 3-$\sigma$ confidence), indicative of short radiative timescales. We propose an atmospheric circulation and cloud distribution regime in which heat is transported eastward from the dayside towards the cold nightside by an equatorial jet, leading to a colder western dayside where temperatures are sufficiently low for the condensation of silicate clouds.

The mass of galaxy clusters derived from weak-lensing observations is sensitive to projection effects, and, on average, it is biased low with respect to the true cluster mass, with a mass and redshift dependence. In this work, we leverage state-of-the-art hydrodynamical simulations of galaxy clusters carried out with GadgetX and GIZMO-SIMBA as part of the Three Hundred Project. We use them to quantify weak-lensing mass biases with respect also to the results from dark matter-only simulations. We also investigate how the biases of the weak-lensing mass estimates propagate into the richness-mass relation. Future wide-field weak-lensing surveys require per cent accuracy on the characterisation of cluster masses in order to use galaxy cluster number count and clustering as complementary probes for cosmological analyses. We aim to shed light on the effect of the presence of baryons on the weak-lensing mass bias and also whether this bias depends on the galaxy formation recipe; in addition, we seek to model the richness-mass relation that can be used as guidelines for observational experiments for cluster cosmology. We produce weak-lensing simulations of random projections to model the expected excess surface mass density profile of clusters up to redshift $z=1$. We derive the weak-lensing mass-richness relation and find consistency within 1$\sigma$ uncertainties across hydrodynamical simulations. The scatter in observed richness at a fixed weak-lensing mass, or vice versa, increases linearly with redshift at a fixed stellar mass cut. Importantly, we observe that the scatter in richness at a given true mass is smaller than at a given weak-lensing mass. Our results align well with SDSS redMaPPer cluster observations. (Abridged)

Extreme coronal line emitters (ECLEs) are a rare class of galaxy that exhibit strong, high-ionization iron coronal emission lines in their spectra. In some cases, these lines are transient and may be the result of tidal disruption event (TDEs). To test this connection, we calculate the rate of variable ECLEs (vECLEs) at redshift $\sim0.3$. We search for ECLEs in the Baryon Oscillation Spectroscopic Survey (BOSS) LOWZ sample and discover two candidate ECLEs. Using follow-up spectra from the Dark Energy Spectroscopic Instrument and Gemini Multi-Object Spectrograph, and mid-infrared observations from the Wide-field Infrared Survey Explorer, we determine that one of these galaxies is a vECLE. Using this galaxy, we calculate the galaxy-normalized vECLE rate at redshift $\sim0.3$ to be $R_\mathrm{G}=1.6~^{+3.8}_{-1.4}\times10^{-6}~\mathrm{galaxy}^{-1}~\mathrm{yr}^{-1}$ and the mass-normalized rate to be $R_\mathrm{M}=7~^{+16}_{-6}\times10^{-18}~\mathrm{M_\odot^{-1}}~\mathrm{yr}^{-1}$. This is then converted to a volumetric rate of $R_\mathrm{V}=1.8~^{+4.5}_{-1.5}\times10^{-9}~\mathrm{Mpc}^{-3}~\mathrm{yr}^{-1}$. Formally, the LOWZ vECLE rates are $2-4$ times lower than the rates calculated from the Sloan Digital Sky Survey Legacy sample at redshift $\sim0.1$. However, given the large uncertainties on both measurements, they are consistent with each other at $1\sigma$. Both the galaxy-normalized and volumetric rates are one to two orders of magnitude lower than TDE rates from the literature, consistent with vECLEs being caused by $5-20$ per cent of all TDEs.

The formation of cataclysmic variables (CVs) has long been modeled as a product of common envelope evolution (CEE) in isolated binaries. However, a significant fraction of intermediate-mass stars -- the progenitors of the white dwarfs (WDs) in CVs -- are in triples. We therefore investigate the importance of triple star dynamics in CV formation. Using Gaia astrometry and existing CV catalogs, we construct a sample of $\sim50$ CVs in hierarchical triples within 1 kpc of the Sun, containing main-sequence (MS) and WD tertiaries at separations of 100 - 30,000 au. We infer that at least 10% of CVs host wide tertiaries. To interpret this discovery, we evolve a population of 2000 triples using detailed three-body simulations, 47 of which become CVs. We predict that 20% of CVs in triples form without ever experiencing CEE, where the WD and donor are brought together by the eccentric Kozai-Lidov (EKL) mechanism after the formation of the WD. These systems favor larger donor stars and longer birth orbital periods (8-20 hrs) than typical CVs. Among systems that do undergo CEE, about half would not have interacted without the presence of the tertiary. Triple formation channels both with and without CEE require initially wide inner orbits ($\gtrsim 1$ au), which in turn require larger tertiary separations to be stable. Consistent with this prediction, we find that the observed Gaia CV triples have wider separations on average than normal wide binaries selected in the same way. Our work underscores the importance of triples in shaping interacting binary populations including CVs, ultracompact binaries, and low-mass X-ray binaries.

We analyze 23 spectroscopically confirmed Type-2 quasars (QSOs) selected from the WISE 22$\rm \mu$m band in the SDSS Stripe 82 region, focusing on their multi-band photometry and spectral energy distributions (SEDs). These objects were selected to be IR-luminous ($\rm flux_{W4} > 5mJy$, i.e., $12.62 < W4 < 14.62 \rm\ AB \, magnitude$), optically faint ($r > 23$) or with red color ($r - W4 >8.38$). Gemini/GNIRS observations were conducted for all 24 candidates, and 18/24 were also observed with Keck/LRIS. The observations confirm 23 to be real Type-2 QSOs in the redshift range $0.88 - 2.99$ (12 are at $z>2$). We collect multi-band photometry and conduct SED fitting. The composite photometry probes the wavelength from 0.1$\rm \mu$m to 10$\rm \mu$m at the rest frame. The IR emission is dominated by dust torus implying an average torus luminosity for the sample of $L_{\rm torus} 10^{46.84} \rm erg/s$. The origin of the rest-UV/optical light is not definitive, but we present three possible scenarios: scattered light, stellar emission, and the reddened accretion disk. Assuming an obscured:unobscured ratio of approximately 1:1, our targets have $L_{\rm bol} = 10^{46.28} \rm erg \,s^{-1} - 10^{47.49} \rm erg \,s^{-1}$ and around SMBH masses $\rm 10^{8.18} M_{\odot} - 10^{9.39} M_{\odot}$, assuming they accreate at the Eddington limit. Compared to previous Type-2 AGN SEDs, our targets have a brighter dust torus and redder optical-IR color. By comparing the SED to the results from JWST `little red dots' (LRDs), we find that these IR-selected Type-2 QSOs have similar SED shapes to the LRDs. This pilot Type-2 QSO survey demonstrates that mid-IR selection is an efficient way to find luminous Type-2 QSOs at $z>2$. Finally, the composite photometry and Type-2 QSOs SED model generated by this sample provide a guide for finding more Type-2 QSOs at higher redshift.

In this work we study the circumstellar material (CSM) around massive stars, and the mass-loss rates depositing this CSM, using a large sample of radio observations of 325 core-collapse supernovae (CCSNe; only $\sim 22 \%$ of them being detected). This sample comprises both archival data and our new observations of 99 CCSNe conducted with the AMI-LA radio array in a systematic approach devised to constrain the mass-loss at different stages of stellar evolution. In the SN-CSM interaction model, observing the peak of the radio emission of a SN provides the CSM density at a given radius (and therefore mass-loss rate that deposited this CSM). On the other hand, limits on the radio emission, and/or on the peak of the radio emission provide a region in the CSM phase space that can be ruled out. Our analysis shows discrepancy between the values of mass-loss rates derived from radio-detected and radio-non-detected SNe. Furthermore, we rule out mass-loss rates in the range of $2 \times 10^{-6} - 10^{-4} \, \rm M_{\odot} \, yr^{-1}$ for different epochs during the last 1000 years before the explosion (assuming wind velocity of $10 \, \rm km \, s^{-1}$) for the progenitors of $\sim 80\%$ of the type II SNe in our sample. In addition, we rule out the ranges of mass-loss rates suggested for red supergiants for $\sim 50 \%$ of the progenitors of type II SNe in our sample. We emphasize here that these results take a step forward in constraining mass-loss in winds from a statistical point of view.

Using the TNG100-1 cosmological simulations, we explore how galaxy properties, such as specific star formation rate ($\rm sSFR=SFR/M_*$), gas fraction ($\rm f_{gas} \,= \, M_{\rm H}/M_{*}$), and star formation efficiency ($\rm SFE_{H} = SFR/M_{H}$), change over the course of galaxy-galaxy interactions. We identify 18,534 distinct encounters from the reconstructed orbits of a sample of massive galaxies ($\rm M_{*} > 10^{10} \; \rm M_{\odot}$) with companions within a stellar mass ratio of 0.1 to 10. Using these encounters, we study the variation of galaxy properties over time as they approach and move away from pericentric encounters over a redshift range of $0 \leq z < 1$. Following the closest pericentric encounters ($\leq 50$ kpc) of a host galaxy with its companion, we find that sSFR is enhanced by a factor of $1.6 \pm 0.1$ on average within the central stellar half-mass radius (R\textsubscript{1/2}) compared to pre-encounter values. Our results show a time delay between pericentre and maximum sSFR enhancement of $\sim$0.1 Gyr with a mean galaxy separation of 75 kpc. We similarly find that $\rm f_{gas}$ is enhanced by a factor of $1.2 \pm 0.1$, and $\rm SFE_{H}$ is enhanced by a factor of $1.4 \pm 0.1$ following the pericentre of an encounter within the same timescale. Additionally, we find evidence of inflowing gas towards the centre, measured by comparing the $\rm f_{gas}$ and metallicity within the central R\textsubscript{1/2} to the galactic outskirts. We find that approximately 70 per cent of the peak sSFR enhancement can be attributed to the increase in $\rm SFE_{H}$, with the increase in $\rm f_{gas}$ contributing the remaining 30 per cent.

Several ground- and space-based searches have increased the number of known exoplanets to nearly 6000. While most are highly unlike our planet, the first rocky worlds in the Habitable Zone (HZ) provide the most intriguing targets for the search for life in the cosmos. As the detections increase, it is critical to probe the HZ as well as its limits empirically using known exoplanets. However, there is not yet a list of rocky worlds that observers can use to probe the limits of surface habitability. We analyze all known exoplanets and identify 67 rocky worlds in the empirical HZ and 38 in a narrower 3D-model HZ. We compare their demographics with the full catalog of exoplanets, analyze their characteristics, give HZ limits for each system, and prioritize targets for observation. We address another critical dimension to this exploration and compile missing stellar age estimates for these candidates. To probe the limits of habitability, we identify several transiting and non-transiting rocky planets that can provide constraints on the inner and outer edge of the HZ, explore how eccentricity influences habitability, and identify the oldest HZ worlds as well as exoplanets with similar flux to modern Earth's. The resulting list of rocky exoplanet targets in the HZ will allow observers to shape and optimize their search strategies with space- and ground-based telescopes -- such as the James Webb Space Telescope, the Extremely Large Telescope, the Habitable Worlds Observatory, and LIFE -- and to design new observing strategies and instruments to explore these intriguing worlds, addressing the question of the limits of surface habitability on exoplanets.

The Event Horizon Telescope (EHT) has produced horizon-resolving images of Sagittarius A* (Sgr A$^*$). Scattering in the turbulent plasma of the interstellar medium distorts the appearance of Sgr A$^*$ on scales only marginally smaller than the fiducial resolution of EHT. Therefore, this process both diffractive blurs and adds stochastic refractive substructures that limits the practical angular resolution of EHT images of Sgr A$^*$. We utilized a novel recurrent neural network machine learning framework to demonstrate that it is possible to mitigate interstellar scattering at wavelengths of $1.3\,{\rm mm}$ near the galactic center up to structures at the scale of $5\mu{as}$ well below the nominal instrumental resolution of EHT, $24\,\mu{\rm as}$.

We search a sample of 9,361,613 isolated sources with 13<g<14.5 mag for slowly varying sources. We select sources with brightness changes larger than ~ 0.03 mag/year over 10 years, removing false positives due to, for example, nearby bright stars or high proper motions. After a thorough visual inspection, we find 782 slowly varying systems. Of these systems, 433 are identified as variables for the first time and 349 are previously classified as variables. Previously classified systems were mostly identified as semi-regular variables (SR), slow irregular variables (L), spotted stars (ROT), or unknown (MISC or VAR), as long time scale variability does not fit into a standard class. The stellar sources are scattered across the CMD and can be placed into 5 groups that exhibit distinct behaviors. The largest groups are very red subgiants and lower main sequence stars. There are also a small number of AGN. There are 551 candidates (~70 percent) that also show shorter time scale periodic variability, mostly with periods longer than 10 days. The variability of 191 of these candidates may be related to dust.

Dwarf galaxies like Sagittarius (Sgr) provide a unique window into the early stages of galactic chemical evolution, particularly through their metal-poor stars. By studying the chemical abundances of stars in the Sgr core and tidal streams, we can gain insights into the assembly history of this galaxy and its early heavy element nucleosynthesis processes. We efficiently selected extremely metal-poor candidates in the core and streams for high-resolution spectroscopic analysis using metallicity-sensitive photometry from SkyMapper DR2, and Gaia DR3 XP spectra and proper motions. This allowed us to obtain a high-purity selection of Sgr members based on stellar kinematics while reducing the chances of potential contamination from the Milky Way halo. We present a sample of 37 Sgr stars with detailed chemical abundances, of which we identify 10 extremely metal-poor (EMP; $\rm{[Fe/H]} \le -3.0$) stars, 25 very metal-poor (VMP; $\rm{[Fe/H]} \le -2.0$) stars, and 2 metal-poor (MP; $\rm{[Fe/H]} \le -1.0$) stars. This sample increases the number of extremely metal-poor Sgr stars analyzed with high-resolution spectroscopy by a factor of five. Of these stars, 15 are identified as members of the Sgr tidal stream, while the remaining 22 are associated with the core. We derive abundances for up to 20 elements and identify no statistically significant differences between the element abundance patterns across the core and stream samples. Intriguingly, we identify stars that may have formed in ultra-faint dwarf galaxies that accreted onto Sgr, in addition to patterns of C and r-process elements distinct from the Milky Way halo. Over half of the sample shows a neutron-capture element abundance pattern consistent with the scaled solar pure r-process pattern, indicating early r-process enrichment in the Sgr progenitor.

Feedback from black hole-powered jets has been invoked in many cosmological simulations to regulate star formation and quench galaxies. Despite this, observational evidence of how jets might be able to affect their hosts remains scarce, especially for low power jets in halos smaller than clusters. Recent observations of outflows around FR0 galaxies, that host compact radio-loud sources, imply that lower-power jetted active galactic nuclei (AGN) may have a significant impact on their hosts through jet interactions with the interstellar medium (ISM). Using the Arepo code, we launch jets of low and intermediate power (10$^{38}$ - 10$^{43}$ erg s$^{-1}$) within a ~kpc-scale periodic box with driven turbulence to study how the jets propagate through a turbulent ISM. Our simulation results broadly fit into three different scenarios $\unicode{x2013}$ jets penetrating easily through the ISM, becoming completely stalled, or the interesting intermediate stage, when jets are highly disturbed and redirected. We suggest that intermediate power jets do not have enough ram pressure to affect the turbulent structure of the ISM, and so only fill pre-existing cavities. Low-power jets are able to drive outflows in a hot phase ($>10^{4.4}$ K). However, warm (~$10^4$ K) ionized gas outflows appear under certain conditions. This work is part of the ''Learning the Universe'' collaboration, aiming to build next-generation cosmological simulations that incorporate a new prescription for AGN feedback.

Fast radio bursts (FRBs) are very energetic pulses of unknown physical origin. These can be used to study the intergalactic medium (IGM) thanks to their dispersion measure (DM). The DM has several contributions that can be measured (or estimated), including the contribution from the host galaxy itself, DM_host. In this work, we empirically estimate DM_host for a sample of 12 galaxy hosts, using a direct method based solely on the properties of the host galaxies themselves (DM_host_dir). We use VLT/MUSE observations of the FRB hosts for estimating DM_host_dir. The method relies on estimating the DM contribution of both the FRB host galaxy's interstellar medium and its halo separately. For comparison purposes, we also provide an alternative indirect method to estimate DM_host based on the Macquart relation (DM_host_mq). We find an average <DM_host> = 80+/-11 pc/cc with a standard deviation of 38 pc/cc (in the rest-frame) based on our direct method, with a systematic uncertainty of 30%. We report positive correlations between DM_host and both the stellar masses and the star-formation rates of their host galaxies. In contrast, we do not find any strong correlation between DM_host and neither redshift nor the projected distances to the FRB hosts centers. Finally, we do not find any strong correlation between DM_host_dir and DM_host_mq, although their average values are consistent. Our reported correlations could be used to improve the priors used in establishing DM_host for individual FRBs. Similarly, such correlations and the lack of a strong redshift evolution can be used to constrain models for the progenitor of FRBs. However, the lack of a DM_host_dir and DM_host_mq correlation indicates that there may still be contributions to the DM of FRBs not included in our modeling, e.g. large DMs from the FRB progenitor and/or intervening large-scale structures not accounted for in DM_host_mq.

We test a novel method for estimating black hole masses ($M_{\rm BH}$) in obscured active galactic nuclei (AGN) that uses proxies to measure the full-width half maximum of broad H$\alpha$ (FWHM$_{\rm bH\alpha}$) and the accretion disk luminosity at 5100 Angstrom ($\lambda L_{\rm 5100 Angstrom}$). Using a published correlation, we estimate FWHM$_{\rm bH\alpha}$ from the narrow optical emission line ratio $L_{\rm [O\,III]}/L_{\rm nH\beta}$. Using a sample of 99 local obscured AGN from the Swift-BAT AGN Spectroscopic Survey, we assess the agreement between estimating $\lambda L_{\rm 5100 Angstrom}$ from the intrinsic 2-10 keV X-ray luminosity and from narrow optical emission lines. We find a mean offset of $0.32 \pm 0.68$ dex between these methods, which propagates to a factor of $\sim$2 uncertainty when estimating $M_{\rm BH}$ using a virial mass formula where $L_{\rm [O\,III]}/L_{\rm nH\beta}$ serves as a proxy of FWHM$_{\rm bH\alpha}$ ($M_{\rm BH,[O\,III]/nH\beta}$). We compare $M_{\rm BH,[O\,III]/nH\beta}$ with virial $M_{\rm BH}$ measurements from broad Paschen emission lines. For the 14 (12) BASS AGN with broad Pa$\alpha$ (Pa$\beta$) detections, we find $M_{\rm BH,[O\,III]/nH\beta}$ to be systematically higher than $M_{\rm BH,Pa\alpha}$ ($M_{\rm BH,Pa\beta}$) by a factor of 0.39 $\pm$ 0.44 dex (0.48 $\pm$ 0.51 dex). Since these offsets are within the scatter, more data are needed to assess whether $M_{\rm BH,[O\,III]/nH\beta}$ is biased high. For 151 BASS AGN with measured stellar velocity dispersions ($\sigma_{\rm *}$), we find that the $\sigma_{\rm *}$-derived $M_{\rm BH}$ agrees with $M_{\rm BH,[O\,III]/nH\beta}$ to within 0.08 dex, albeit with wide scatter (0.74 dex). The method tested here can provide estimates of $M_{\rm BH}$ in thousands of obscured AGN in spectroscopic surveys when other diagnostics are not available, though with an uncertainty of $\sim$3-5.

The blazar 3C 279 is well known for its prolific emission of rapid flares. A particular event occurred on 12/20/2013, exhibiting a large flux increase with a doubling time scale of a few hours, a very hard gamma-ray spectrum, and a time-asymmetric light curve with slow decay, but no significant variations detected in the optical range. We propose a novel scenario to interpret this flare, based on two emission zones, a stationary blob and a moving plasma blob. The stationary blob, located within the BLR, accounts for the low-state emission. The moving blob decouples from the stationary zone, accelerates and crosses the BLR. The high-energy flare is attributed to the variable external Compton emission as the blob moves through the BLR, while variations in the synchrotron emission are negligible. Our interpretation differs from previous interpretations by attributing the flare to the bulk motion and geometry of the external photon fields, without invoking varying electron injection.

The distribution and origin of serpentine on Mars can provide insights into the planet's aqueous history, habitability, and past climate. In this study, we used dynamic aperture factor analysis/target transformation applied to 15,760 images from the Compact Reconnaissance Imaging Spectrometer for Mars, followed by validation with the radiance ratio method, to construct a map of Mg-serpentine deposits on Mars. Although relatively rare, Mg-serpentine was detected in diverse geomorphic settings across Noachian and Hesperian-aged terrains in the southern highlands of Mars, implying that serpentinization was active on early Mars and that multiple formation mechanisms may be needed to explain its spatial distribution. We also calculated the amount of H2 produced during the formation of the observed deposits and conclude that serpentinization was likely more widespread on Mars than indicated by the observed distribution.

We present an analysis of very metal-poor (VMP) and metal-poor stars ($-3.0 < \mathrm{Fe/H]} < -1.5$) in the Gaia BP/RP or XP catalog, which reveals two distinct metallicity distribution functions (MDFs) in regions of the Galactic disk above and below $|z| = 1.0$ kpc. The low-$|z|$ regions display a metallicity peak around [Fe/H] = -2.0 with a sharp transition in Galactocentric azimuthal velocity ($v_\phi$), a feature notably absent in high-$|z|$ regions. Using a galactic chemical evolution (GCE) model, we found that the proto-Milky Way underwent two distinct formation scenarios: a rapid star formation burst followed by quenching near the Galactic center and an extended period of steady star formation. This starburst could have been triggered by a gas-rich accretion event in the first Gyr of our Galaxy's history. Comparison with Milky Way-analog galaxies in Auriga simulations shows strong agreement in the characteristics of this starburst population. During the accretion event, gas rapidly sinks into the inner regions of these analog galaxies, producing the observed MDF peak and the low $v_\phi$ values. The simulations further indicate that most stars at the metallicity peak formed in situ, rather than through accretion. These findings identify this starburst population as the long-sought in situ component of the proto-Galaxy.

Brown dwarfs lack nuclear fusion and cool with time; the coldest known have an effective temperature below 500 K, and are known as Y dwarfs. We present a James Webb Space Telescope (JWST) photometric dataset of Y dwarfs: twenty-three were imaged in wide-field mode, 20 using NIRCam with the F150W and F480M filters, and 3 using NIRISS with the F480M filter. We present an F480M vs. F150W $-$ F480M color-magnitude diagram for our sample, and other brown dwarfs with F150W and F480M colors synthesized from JWST spectra by Beiler et al. (2024). For one target, WISEA J083011.95$+$283716.0, its detection in the near-infrared confirms it as one of the reddest Y dwarfs known, with F150W $-$ F480M $= 9.62$ mag. We provide its updated parallax and proper motion. One of the Beiler et al. Y dwarfs, CWISEP J104756.81+545741.6, is unusually blue, consistent with strong CO absorption seen in its spectrum which the F480M filter is particularly sensitive to. The strong CO and the kinematics of the object suggest it may be very low-mass and young. We update the resolved photometry for the close binary system WISE J033605.05$-$014350.4 AB, and find that the secondary is almost as cold as WISE 085510.83$-$071442.5, with $T_{\rm eff} \lesssim 300$ K, however the F150W $-$ F480M color is significantly bluer, possibly suggesting the presence of water clouds. Astrometry is measured at the JWST epoch for the sample which is consistent with parallax and proper motion values reported by Kirkpatrick et al. (2021) and Marocco et al. (in prep).

The Ultraviolet Explorer (UVEX) is expected to fly in 2030 and will have the opportunity -- and the rapid near/far ultraviolet (UV) capabilities -- to glean unprecedented insight into the bright UV emission present in kilonovae like that of AT 170817gfo, the electromagnetic counterpart to binary neutron star merger GW170817. To do so, it will need to perform prompt target-of-opportunity observations following detection of binary neutron star mergers by the LIGO-Virgo-KAGRA gravitational observatories. We present initial simulations to develop UVEX target-of-opportunity strategies for such events and provide the community with detailed initial estimates of the prospects for and characteristics of UVEX target-of-opportunity observations following gravitational-wave events, considering fiducial scenarios for the fifth and sixth LIGO-Virgo-KAGRA observing runs. Additionally, in light of the relatively few binary neutron star mergers observed since GW170817, we consider variant target-of-opportunity strategies for UVEX to maximize scientific gain in the case of a lowered binary neutron star merger rate.

We study a sample of 30 high-redshift blazars ($z>2.5$) by means of spectra and the radiation mechanism with Fermi Large Area Telescope $\gamma$-ray observations spanning 15 years. Three models -- the power law, power law with an exponential cutoff, and log-parabola -- are employed to analyze the spectral properties, and most sources exhibit significant curvature. The high-redshift blazars exhibit higher $\gamma$-ray luminosities and softer spectral indices compared with their low-redshift counterparts, where B3~1343+451 has the highest integrated flux, $\rm 1.13 \times 10^{-7} \mathrm{\ ph \ cm^{-2} s^{-1}}$. We use a standard one-zone leptonic emission model to reproduce the spectral energy distributions of 23 sources with multiwavelength observations. We find that modeling with infrared seed photons is systematically better than with broad-line region (BLR) photons based on a $\chi^2$ test, which suggests that the $\gamma$-ray-emitting regions are most likely located outside the BLR. The fit results show that high-redshift blazars exhibit higher energy density, jet power, kinetic power, and accretion disk luminosities, along with lower synchrotron and inverse Compton (IC) peak frequencies, relative to their lower-redshift counterparts. We find that blazars with higher accretion disk luminosities tend to have lower IC peak frequencies, leading to more efficient cooling of high-energy electrons. The positive correlation between jet power and accretion disk luminosity further supports the possibility of an accretion-jet connection in these high-redshift sources.

Neutrino quantum kinetics is a rapidly evolving field in computational astrophysics, with a primary focus on collective neutrino oscillations in core-collapse supernovae and post-merger phases of binary neutron star mergers. In recent years, there has been considerable debate concerning resolution dependence in numerical simulations. In this paper, we conduct a comprehensive resolution study in both angular- and spatial directions by using two independent schemes of quantum kinetic neutrino transport: finite volume and pseudospectral methods. We complement our discussion by linear stability analysis including inhomogeneous modes. Our result suggests that decreasing spatial resolutions underestimates the growth of flavor instability, and then leads to wrong asymptotic states of flavor conversions, which potentially has a critical impact on astrophysical consequences. We further delve into numerical results of low resolution simulations, that reveals the underlying mechanism responsible for numerical artifacts caused by insufficient resolutions. This study settles the debate on requirements of resolutions and serves as a guideline for numerical modeling of quantum kinetic neutrino transport.

Rapidly rotating newborn magnetars, which originate from binary neutron star (NS) mergers and serve as the central engines of short gamma-ray bursts (GRBs), may leave some imprints on their prompt gamma-ray lightcurves even though they are far from their radiating fireballs. A high-frequency quasi-periodic oscillation (QPO) would be a unique feature for the magnetar central engine, especially a hypermassive magnetar. By conducting a systematic analysis of the prompt gamma-ray lightcurves from 605 short GRBs observed by Fermi/GBM, we have identified such QPO signals in three GRBs (e.g., GRB 120323A, GRB 181222B, and GRB 190606A). The QPOs that peaked at $1258^{+6}_{-6}$ Hz for GRB 120323A, $623^{+4}_{-4}$ Hz for GRB 181222B, and $1410^{+4}_{-5}$ Hz for GRB 190606A are all with a confidence level above 5.2 $\sigma$. The high-frequency QPO signals of those three short GRBs may be caused by a hypermassive magnetar acting as the central engine in a binary neutron star merger of binary neutron star.

Star clusters provide unique advantages for investigating Galactic spiral arms, particularly due to their precise ages, positions, and kinematic properties, which are further enhanced by ongoing updates from the astrometric data. In this study, we employ the latest extensive catalogue of open clusters from Gaia DR3 to examine the positional deviations of clusters belonging to different age groups. Additionally, we employ dynamical simulations to probe the evolutionary behavior of spiral arm positions. Our analysis reveals an absence of a theoretical age pattern in the spiral arms traced by open clusters, and the pattern speeds of the spiral arms are consistent with the rotation curve. Both of these results do not align with the predictions of quasi-stationary density wave theory, suggesting a more dynamic or transient arm scenario for the Milky Way. From this perspective, combined with vertex deviation estimates, it appears that the Local arm is in a state of growth. In contrast, the Sagittarius-Carina arm and the Perseus arm exhibit opposing trends. Consequently, we speculate that the Galactic stellar disk does not exhibit a grand-design spiral pattern with a fixed pattern speed, but rather manifests as a multi-armed structure with arms that continuously emerge and dissipate.

This study comprehensively analyzes Atlas's current orbit, focusing on the secular and resonant perturbations caused by Prometheus, Pandora, and Saturn's oblateness. We performed numerical integration of the exact equations of motion for a dense ensemble of Atlas clone satellites. Through spectral analysis and interpretation of these orbits on dynamical maps, we identified the domain of the 54:53 Prometheus-Atlas and 70:67 Pandora-Atlas mean-motion resonances, showing that Atlas lies on the boundary of the separatrices of each of these resonances. We also identified the domains for the multiplets $\Psi_{1}$, $\Psi_{2}$, $\Psi_{3}$ and $\Psi_{4}$ associated with 70:67 resonance. Additionally, we explored the variation in Prometheus's eccentricity, demonstrating that as eccentricity increases (or decreases) in the 54:53 resonance domain correspondingly decreases (or increases). This combined analysis, between the above mappings, revealed qualitatively the overlap between the 54:53 and 70:67 resonances, which are responsible for the chaotic behavior of Atlas's orbit. We quantified chaotic motion in frequency space and found that the vicinity of Atlas is characterized by weak to moderate chaos, rather than strong chaos. Finally, we investigated Atlas's recent past, considering Prometheus's migration under the influence of Saturn's tidal forces. This analysis reveals several resonances crossed in the past, particularly focusing on the Atlas-Prometheus pair, which exhibited a co-orbital configuration.

Fast Radio Bursts (FRBs) are energetic millisecond radio bursts at cosmological distances, whose underlying engine is not identified. Among a sub-population that emit repeated radio bursts, a handful were associated with a persistent radio source (PRS) whose origin is unknown. Here we report the discovery of a compact flaring radio source (FRS) associated with a newly-active repeating FRB within one month after the first radio burst was detected. Its temporal and spectral characteristics differ from those of the PRSs but are similar to those of engine-powered supernovae and low-luminosity active galactic nuclei. We detected a spectral peak around $1.6\pm0.2$ GHz that is consistent with synchrotron self-absorption. Assuming equipartition, the magnetic field strength in the FRS is larger than the line-of-sight component constrained from the FRB Faraday rotation, suggesting a highly magnetized engine. The radius of the FRS is constrained to be $\sim0.03$ pc and the minimum total energy is $\sim~6.2\times{10}^{47}~{\rm ergs~}$. This FRS reveals the birth of a highly magnetized FRB engine, and hints that PRSs associated with other active FRBs may be in the later stage of evolution.

The observed spectral bump in cosmic-ray (CR) proton and helium spectra, along with the phase and amplitude evolution of CR dipole anisotropy, provide plausible yet indirect evidence for the presence of a nearby CR source. This study investigates the potential of giant molecular clouds (GMCs) located near the solar system to act as natural probes of CRs from the nearby source, with their gamma-ray emissions serving as indicators of spatial variations in CR flux within the solar neighborhood resulting from this source. We show that a nearby source, accounting for the CR data, could imprint distinct features on the $\gamma$-ray spectra of different GMCs. We expect that these features are detectable by LHAASO and upcoming high-energy $\gamma$-ray observatories, providing a powerful test for the hypothesized nearby source. Notably, we find that determining the energy dependence of the $\gamma$-ray spectral index offers a promising approach to investigate the nearby source and constrain its distance. Conversely, if the spectral bump is a widespread Galactic phenomenon, the energy dependence would exhibit uniformity across all GMCs, distinguishing the underlying mechanism accounting for the spectral bump from the scenario involving a nearby source.

We investigated simultaneous NICER plus NuSTAR observations of three neutron star low-mass X-ray binary 4U 1636-53, XTE J1739-285 and MAXI J1816-195 using the latest reflection models, with the seed photons feeding into the corona originating from either the neutron star (NS) or the accretion disk. We found that, for the sources in the hard spectral state, more than $\sim$ 50% of the NS photons enter into the corona if NS provides seed photons, while only $\sim$ 3%-5% disk photons go to the corona if seed photons come from the disk. This finding, together with the derived small height of the corona, favors the lamp-post geometry or boundary layer scenario where the corona is close to the central neutron star. Additionally, we found that the source of the seed photons has big influence in the significance of the NS radiation, especially for the soft spectral state. This result may help explain why the NS radiation in MAXI J1816-195 is weak in the previous work. More importantly, for the first time, we explored the properties of the corona in the NS systems with the compactness ($l-\theta$) diagram. We found that the corona in the NS systems all lie in the left side of the pair-production forbidden region, away from the predicted pair-production lines. This finding indicates that either the corona in these NS systems is not pair-dominated, possibly due to the additional cooling from NS photons, or the corona is composed of both thermal and non-thermal electrons.

In autumn 2023, a series of closely timed eruptive events were observed remotely and measured in situ. We studied analogous solar events, where several CMEs were launched partly from the same (active) regions near a CH. These events occurred in two episodes, separated by a full solar rotation, covering October 31-November 3 and November 27-28, 2023. Both episodes are linked to strong geomagnetic storms on November 4-5 and December 1-2, 2023. We aim to understand the complexity of these events and how the global magnetic field, solar wind conditions, and structural interactions relate to the observed geomagnetic effects. Using the GCS 3D reconstruction method, we derived each CME's motion direction and speed. These results were input into the DBM with enhanced latitudinal information (3D DBM), aiding in connecting in-situ measurements with solar surface structures for integrated interpretation. The first episode caused SAR arcs, with a three-step Dst index drop to -163 nT on November 5, 2023. Two CME-related shocks arrived close in time, separated by a SBC, followed by a short-duration flux rope-like structure. The second episode saw auroral lights and a two-step Dst index drop to -108 nT on December 1, 2023. A shock from one CME interacted with the magnetic structure of a preceding CME, again combined with an SBC. A clear flux rope structure from the shock-producing CME was detected. Both events showed distinct magnetic field 'ripples' and fluctuations in density and temperature following the SBC. This study compares two episodes of multiple eruptive events in November and December 2023. Interacting CME structures and SBC-related magnetic modulations contributed to the stronger geomagnetic impacts, particularly in the November 4-5, 2023 event. The highly tilted heliospheric current sheet may have further influenced the CMEs' impact at Earth.

Polarimetric observations of X-ray pulsars (XRPs) have provided us with the key to unlocking their geometrical properties. Thanks to the Imaging X-ray Polarimetry Explorer (IXPE) the geometries of several XRPs have been determined, providing new insights into their emission mechanisms and magnetic field structures. Previously, Vela X-1 has proven to be exceptional in demonstrating a clear energy dependence of its polarimetric properties, showing a 90$^{\circ}$ swing in the polarization angle (PA) between low and high energies. Due to the complex energy-dependent nature of the polarization properties, it was not possible to determine the pulsar geometry. In this work, we present the results of a detailed analysis of the pulse phase-resolved polarization properties of at different energies. By separating the polarimetric analysis into low and high energy ranges, we are able to disentangle the contributions of the soft and hard spectral components to the polarization, revealing the pulse phase dependence of polarization degree (PD) and PA in each energy band. The PA pulse phase dependence at high energies (5$-$8 keV) allows us, for the first time, to determine the pulsar geometry in Vela X-1. The fit with the rotating vector model gives an estimate for the pulsar spin position angle at around 127$^{\circ}$ and for the magnetic obliquity of 13$^{\circ}$. In order to explain the 90$^{\circ}$ swing in PA between high and low energies, we discuss two possible scenarios: a two-component spectral model and the vacuum resonance.

The sources of cosmic rays between the knee and the ankle are still debated. The Galactic wind and its termination shock have been proposed to contribute to this transition between Galactic and extragalactic origin, but another possibility is large-scale shock structures from local sources in the Milky Way. In this paper, we investigate CR transport in a time-dependent landscape of shocks in the Galactic halo. These shocks could result from local outbursts, e.g. starforming regions and superbubbles. CRs re-accelerated at such shocks can reach energies above the knee. Since the shocks are closer to the Galaxy than a termination shock and CRs escape downstream, they can propagate back more easily. With such outbursts happening frequently, shocks will interact. This interaction could adjust the CR spectrum, particularly for the particles that are able to be accelerated at two shocks simultaneously. The transport and acceleration of CRs at the shock is modeled by Stochastic Differential Equations (SDEs) within the public CR propagation framework CRPropa. We developed extensions for time-dependent wind profiles and for the first time connected the code to hydrodynamic simulations, which were run with the public Athena++ code. We find that, depending on the concrete realization of the diffusion tensor, a significant fraction of CRs can make it back to the Galaxy. These could contribute to the observed spectrum around and above the CR knee ($E \gtrsim 10\,\mathrm{PeV}$). In contrast to simplified models, a simple power-law does not describe the energy spectra well. Instead, for single shocks, we find a flat spectrum ($E^{-2}$) at low energies, which steepens gradually until it reaches an exponential decline. When shocks collide, the energy spectra transiently become harder than $E^{-2}$ at high energies.

White dwarfs are often found in close binaries with stellar or even substellar companions. It is generally thought that these compact binaries form via common envelope evolution, triggered by the progenitor of the white dwarf expanding after it evolved off the main-sequence and engulfing its companion. To date, a handful of white dwarfs in compact binaries with substellar companions have been found, typically with masses greater than around 50 M$_\mathrm{Jup}$. Here we report the discovery of two eclipsing white dwarf plus brown dwarf binaries containing very low mass brown dwarfs. ZTF J1828+2308 consists of a hot ($15900\pm75$ K) $0.610\pm0.004$ M$_{\odot}$ white dwarf in a 2.7 hour binary with a $0.0186\pm0.0008$ M$_{\odot}$ ($19.5\pm0.8$ M$_\mathrm{Jup}$) brown dwarf. ZTF J1230$-$2655 contains a cool ($10000\pm110$ K) $0.65\pm0.02$ M$_{\odot}$ white dwarf in a 5.7 hour binary with a companion that has a mass of less than 0.0211 M$_{\odot}$ (22.1 M$_\mathrm{Jup}$). While the brown dwarf in ZTF J1828+2308 has a radius consistent with its mass and age, ZTF J1230$-$2655 contains a roughly 20 per cent overinflated brown dwarf for its age. We are only able to reconstruct the common envelope phase for either system if it occurred after the first thermal pulse, when the white dwarf progenitor had already lost a significant fraction of its original mass. This is true even for very high common envelope ejection efficiencies ($\alpha_\mathrm{CE}\sim 1$), unless both systems have extremely low metallicities. It may be that the lowest mass companions can only survive a common envelope phase if it occurs at this very late stage.

NCORES was a large observing program on the ESO HARPS spectrograph, dedicated to measuring the masses of Neptune-like and smaller transiting planets discovered by the TESS satellite using the radial velocity technique. This paper presents an overview of the programme, its scientific goals and published results, covering 35 planets in 18 planetary systems. We present spectrally derived stellar characterisation and mass constraints for five additional TOIs where radial velocity observations found only marginally significant signals (TOI-510.01, $M_p=1.08^{+0.58}_{-0.55}M_\oplus$), or found no signal (TOIs 271.01, 641.01, 697.01 and 745.01). A newly detected non-transiting radial velocity candidate is presented orbiting TOI-510 on a 10.0d orbit, with a minimum mass of $4.82^{+1.29}_{-1.26}M_\oplus$, although uncertainties on the system architecture and true orbital period remain. Combining the NCORES sample with archival known planets we investigate the distribution of planet masses and compositions around and below the radius gap, finding that the population of planets below the gap is consistent with a rocky composition and ranges up to a sharp cut-off at $10M_\oplus$. We compare the observed distribution to models of pebble- and planetesimal-driven formation and evolution, finding good broad agreement with both models while highlighting interesting areas of potential discrepancy. Increased numbers of precisely measured planet masses in this parameter space are required to distinguish between pebble and planetesimal accretion.

In this letter we argue that the CPL parameterisation for the dark energy equation of state is biased towards preferring such model over the constant $w$ while the latter bounds are still compatible with LCDM. For that we compare constraints on the EoS parameters $w_0$ and early time type $w_a$ (CPL) against those with a late time parameterisation on $w_a$ (LZ) and the constant $w$ model, using CMB, Supernovae and BAO from DESI datasets. We found, the same as was the case with CPL model, preference for dynamical dark energy within the LZ model, but for values almost symmetrically distributed with respect to their LCDM limits. This is due to the fact that the presence of $w_0$ allows to recast each parametrisation into making it compensate the preference for $w\sim -1$ in the opposite direction. To further test our hypothesis, we fixed $w_0$ to -1 and followed a minimal approach by considering models that deviates by one free parameter, or we extend to more general models that either group both late and early effects, or allow the presence of two dark energy fluid alike and constant alike component. We found that all the variants, except the original CPL are still compatible with LCDM, with likelihoods peaking close to $w_0 = -1$, $w_a = 0$, or 0.68 for $\Omega_{\rm CC}$, with the constant $w$ and the late time $w_a$ having the smallest constraints. Although we found that the evidence from CPL is stronger than those for the more minimal cases, however the preference increases further for the more generalized parameterizations, while still staying compatible with LCDM in terms of the significance levels. We conclude that considering CPL model is not sufficient to test deviation from the standard model and that it is necessary to conduct further minimal or more general approaches to better understand the outcomes from model testing and inference methods.(abridged)

We study the effect of Spontaneous Lorentz Symmetry Breaking (SLSB) on Primordial Gravitational Waves (PGWs) generated during inflation. The SLSB is induced by a time-like Bumblebee vector field which is non-minimally coupled to the Ricci tensor in the Friedmann-Lemaître-Robertson-Walker (FLRW) background. The power spectrum and GW amplitude are computed to investigate how Lorentz violation leaves observable imprints. Our analysis contrasts the Lorentz-violating Bumblebee cosmology with standard cosmology in the context of primordial GW generation. We calculate the GW strain amplitude over frequencies $(10^{-10}~\mathrm{Hz}, 10^4~\mathrm{Hz})$, for a range of the dimensionless Lorentz-violating parameter, $ -10^{-3} \leq l \leq 10^{-4} $, which essentially comes from a slight sensitivity to the equation of state for dark energy. For positive $l$ values, the amplitude of GW shows a mild suppression compared to the standard cosmological scenario ($ l = 0 $). This effect could be observable with detectors like SKA, $\mu$-Ares, and BBO. Conversely, negative $ l $ values amplify the GW amplitude, enhancing detectability by both SKA, $\mu$-Ares, and BBO, as well as by THEIA and DECIGO. Notably, the GW strain amplitude increases by an order of magnitude as $ l $ moves from $0$ to $ -10^{-3} $, improving prospects for detection in high-sensitivity detectors like THEIA and DECIGO.

This study is aimed at identifying possible low-mass and sub-stellar companions to stars with well-determined metallicities. We investigate the multiplicity of metal-poor stars along with its impact on formation processes in the conditions of the early universe. Our goal is to look for wide common proper motion companions to metal-poor stars and study the binarity frequency at low metallicity with astrometry from large-scale catalogues (Gaia, VHS, and WISE). We used the stellar parameter determination from the latest release of Gaia to identify metal-poor stars over the entire sky. We combined the Gaia sample with other public catalogues and spectroscopic determinations for a given subsample to refine the stellar metallicities. We also considered other public catalogues of metal-poor stars to look for co-moving companions. We obtained our own high-resolution images of a subsample with the lucky imaging technique. We found a few bona fide co-moving systems among a sample of 610 metal-poor stars with metallicities below -1.5 dex in the full sky. We inferred a multiplicity rate below 3%, with 3sigma completeness for projected separations larger than 8 au, after taking into account incompleteness and any other limiting factors of our search. At closer separations, we found a minimum binary fraction of 20% that appears to be relatively independent of metallicity. We conclude that the multiplicity fraction of solar-type stars is relatively independent of metallicity for close-in companions with projected separations below ~8 au. Between 8 and 10000 au, the binary fraction of metal-poor stars drops significantly to a few percent and is significantly lower than the multiplicity derived for the solar-metallicity case. We interpret these similarities and differences as being due to the chemistry at work in molecular clouds as well as disruption effects attributed to the old age of subdwarfs.

Context. The MINCE (Measuring at Intermediate Metallicity Neutron-Capture Elements) project aims to provide high quality neutron-capture abundances measurements in several hundred stars at intermediate metallicity,-2.5 < [Fe/H] < -1.5. This project will shed light on the origin of the neutron-capture elements and the chemical enrichment of the Milky Way. Aims. The goal of this work is to chemically characterize the second sample of the MINCE project and compare the abundances with the galactic chemical evolution model at our disposal. Methods. We performed a standard abundance analysis based on 1D LTE model atmospheres on high-resolution and high-signal-to-noise-ratio UVES spectra. Results. We provide the kinematic classification (i.e., thin disk, thick disk, thin-to-thick disk, halo, Gaia Sausage Enceladus, Sequoia) of 99 stars and the atmospheric parameters for almost all stars. We derive the abundances for light elements (from Na to Zn) and neutron-capture elements (Rb, Sr, Y, Zr, Ba, La, Ce, Pr, Nd, Sm, Eu) in a subsample of 32 stars in the metallicity range -2.5 < Fe/H] < -1.00. In the subsample of 32 stars, we identify 8 active stars exhibiting (inverse) P-Cygni profile and one Li-rich star, CD 28-11039. We find a general agreement between the chemical abundances and the stochastic model computed for the chemical evolution of the Milky Way halo for the elements Mg, Ca, Si, Ti, Sc, Mn, Co, Ni, Zn, Rb, Sr, Y, Zr, Ba, La, and Eu . Conclusions. The MINCE project has already significantly increased the number of neutron-capture elements measurements in the intermediate metallicity range. The results from this sample are in perfect agreement with the previous MINCE sample. The good agreement between the chemical abundances and the chemical evolution model of the Galaxy supports the nucleosynthetic processes adopted to describe the origin of the n-capture elements.

Three methods for computing the total star formation rate of the Milky Way agree well with a reference value of $1.65\pm0.19$ M$_\odot$ yr$^{-1}$. They are then used to determine the radial dependence of the star formation rate and face-on map for the Milky Way. First, the method based on a model of star formation in Hi-GAL-defined dense clumps, adjusted for an increase in the gas-to-dust ratio with Galactocentric radius, predicts $1.65\pm0.61$ M$_\odot$ yr$^{-1}$. Second, the method using the 70 $\mu$m emission, commonly used in other galaxies, with a technique to assign distances to the extended emission, predicts $1.42^{+0.63}_{-0.44}$ M$_\odot$ yr$^{-1}$. Finally, a method based on theoretical predictions of star formation efficiency as a function of virial parameter, with masses corrected for metallicity dependence, applied to a catalog of molecular clouds also predicts a value in agreement at $1.47$ M$_\odot$ yr$^{-1}$. The three methods predict the radial variation of the star formation rate, with remarkably good agreement from the CMZ out to about 20 kpc. More differences were seen in face-on maps with a resolution of 0.5 kpc made with the three approaches and in comparisons to the local (within 3 kpc) star formation rate, indicating limitations of the methods when applied to smaller scales. The 70 $\mu$m star formation rate follows very closely the surface density of molecular gas, corrected for a metallicity-dependent CO conversion factor. A molecular gas depletion time of 1 Gyr is consistent with the data, as is a molecular Kennicutt-Schmidt relation with a power-law slope of $1.10 \pm 0.06$.

We developed, characterised, and verified an alignment method for the DESHIMA 2.0 instrument, an ultra wide-band spectrometer operating between 200-400 GHz, at the ASTE telescope. Due to the ultra-wide bandwidth of DESHIMA 2.0, we require the alignment to work across the entire spectral range. Moreover, alignment should be possible remotely, as on-site access is impractical. To fulfill these requirements we mounted the warm optics, consisting of a modified Dragonian dual reflector system, on a motor controlled hexapod. Crucial in the alignment procedure is our sky chopper, which allows fast beam switching. Importantly, it has a small entrance and exit aperture coupling to (cold) sky, which creates a measurable signal with respect to the warm cabin environment. By scanning the instrument beam across the entrance aperture of the sky chopper using the hexapod, we found the hexapod configuration that produced the lowest signal on our detectors, implying the beam is coupled fully to cold sky and not the warm cabin. We first characterised the alignment procedure in the laboratory, where we used a vat containing liquid nitrogen as the cold source behind the sky chopper. Then, we applied the alignment procedure to DESHIMA 2.0 at ASTE, using the sky as the cold source. We used observations of Mars to calculate the aperture efficiency. We did not recover the aperture efficiencies up to design values, which we suspect to be due to a raised sidelobe level or error beam pattern. However, we did find that the alignment procedure significantly improved the aperture efficiency compared to previously reported values of the aperture efficiency of DESHIMA at ASTE, which indicates the veracity of the alignment procedure.

White dwarf-main sequence (WDMS) binary systems are essential probes for understanding binary stellar evolution and play a pivotal role in constraining theoretical models of various transient phenomena. In this study, we construct a catalog of WDMS binaries using Gaia DR3's low-resolution BP/RP (XP) spectra. Our approach integrates a model-independent neural network for spectral modelling with Gaussian Process Classification to accurately identify WDMS binaries among over 10 million stars within 1 kpc. This study identify approximately 30,000 WDMS binary candidates, including ~1,700 high-confidence systems confirmed through spectral fitting. Our technique is shown to be effective at detecting systems where the main-sequence star dominates the spectrum - cases that have historically challenged conventional methods. Validation using GALEX photometry reinforces the reliability of our classifications: 70\% of candidates with an absolute magnitude $M_{G} > 7$ exhibit UV excess, a characteristic signature of white dwarf companions. Our all-sky catalog of WDMS binaries expands the available dataset for studying binary evolution and white dwarf physics and sheds light on the formation of WDMS.

We present a novel cosmological framework that unifies matter creation dynamics with thermodynamic principles. Starting with a single-component fluid characterized by a constant equation of state parameter, $\omega$, we introduce a generalized second law of thermodynamics by considering the entropy associated with the cosmic horizon. Imposing an adiabatic expansion condition uniquely determines the particle creation rate, $\Gamma$, a feature unprecedented in previous matter creation models. This mechanism yields a cosmology featuring phantom-like expansion while relying solely on a single constituent, which can be either a quintessence-like fluid or a non-exotic, non-relativistic dark matter component. Remarkably, this framework avoids the need for exotic physics while providing a consistent explanation for the accelerated expansion of the universe. Our results open new pathways for understanding the interplay between horizon thermodynamics, particle creation, and cosmic evolution, offering fresh insights into the nature of dark energy and its potential thermodynamic origins.

We compare current 1D and multi-dimensional atmosphere modelling approaches for massive stars to understand their strengths and shortcomings. We calculate averaged stratifications from selected 2D calculations for O stars -- corresponding to the spectral types O8, O4, and O2 -- to approximate them with 1D stellar atmosphere models using the PoWR model atmosphere code and assuming a fixed $\beta-$law for the wind regime. We then study the effects of our approximations and assumptions on current spectral diagnostics. In particular, we focus on the impact of an additional turbulent pressure in the subsonic layers of the 1D models. To match the 2D averages, the 1D stellar atmosphere models need to account for turbulent pressure in the hydrostatic equation. Moreover, an adjustment of the connection point between the (quasi-)hydrostatic regime and the wind regime is required. The improvement between the density stratification of 1D model and 2D average can be further increased if the mass-loss rate of the 1D model is not identical to those of the 2D simulation, but typically $\sim0.2\,$dex higher. Especially for the early type star, this implies a significantly more extended envelope with a lower effective temperature. Already the inclusion of a constant turbulence term in the solution of the hydrostatic equation sufficiently reproduces the 2D-averaged model density stratifications. The addition of a significant turbulent motion also smoothens the slope of the radiative acceleration term in the (quasi-)hydrostatic domain, with several potential implications on the total mass-loss rate inferred from 1D modelling. Concerning the spectral synthesis, the addition of a turbulence term in the hydrostatic equation mimics the effect of a lower surface gravity, potentially presenting a solution to the ``mass discrepancy problem'' between the evolutionary and spectroscopy mass determinations.

The interaction of TeV blazars emitted gamma-rays with the extragalactic background photons gives rise to a relativistic beam of electron-positron ($e^- e^+$) pairs propagating through the intergalactic medium, producing a cascade through up-scattering low-energy photons. Plasma instability is considered one of the underlying energy-loss processes of the beams. We employ particle-in-cell (PIC) simulations to study the plasma instabilities of ultra-relativistic pair beams propagating in a denser background plasma, using the parameters designed to replicate astrophysical jets under laboratory conditions. In an astrophysical scenario with a broad, dilute beam, electromagnetic instability can be disregarded because its growth rate is slower than that of electrostatic instability, indicating the electromagnetic modes are suppressed. We calculate the physical limit of density contrast at which a warm beam achieves suppression of electromagnetic instabilities in laboratory experiments, consistent with the physically relevant conditions for Blazar-induced beams. We have used a composite Cauchy distribution for the beam particles, which is more realistic in representing the non-Maxwellian nature of pair beams, improving upon previous studies. We investigate the interplay between the magnetic field forming from localized currents and transverse beam momentum spread. We extrapolate to the non-linear feedback of instability where the beam is energetically broadened. We observe that the instability generates a negligible angular broadening for Blazar-Induced beams.

Studying accretion-driven episodic outbursts in YSOs is key to understanding the later stages of star and planet formation. FU Orionis-type objects form a YSO subclass, distinguished by rapid, multi-magnitude increases in brightness at optical and near-infrared wavelengths. These outbursts may significantly impact the chemistry and molecular composition around eruptive stars. However, no comprehensive millimeter-wavelength line survey exists for more evolved (Class II) sources, unlike optical and near-infrared coverage. We conducted the first wideband millimeter spectral line survey of V1057 Cyg, a low-mass eruptive FUor with the highest observed peak accretion rate in its class. Using the IRAM 30-m telescope, we surveyed the 72-263 GHz range and complemented this with targeted spectra at 219, 227, 291, and 344 GHz with the APEX 12-m telescope. We conducted radiative transfer and population diagram analyses to get first estimates of the excitation temperatures and column densities. Several molecular species trace large-scale structures, and the position-velocity diagram of $^{12}$CO suggest episodic outburst activity, with outflow dynamical timescales on the order of tens of thousands of years. We identified simple molecules (C-, N-, O-, and S-bearing), deuterated species, molecular ions, and complex organic molecules. With over 30 molecular species (including isotopologues) detected, V1057 Cyg demonstrates rich chemistry for its evolutionary state, compared to other younger (Class 0/I) FUors. V1057 Cyg is a good candidate for future interferometric studies to resolve emission structures, to possibly constrain molecular freeze-out, and detect water and complex organic molecules. Our results highlight the importance of millimeter line surveys in complementing optical/near-infrared studies, improving statistics on molecular inventories in eruptive stars and their environments.

To reveal the origin of the mini-starbursts in the Milky Way, we carried out large-scale CO observations toward the RCW 106 giant molecular cloud (GMC) complex using the NANTEN2 4-m radio telescope operated by Nagoya University. We also analyzed the Mopra Southern Galactic plane CO survey and Herschel infrared continuum archival data. The RCW 106 GMC complex contains the radial velocity components of $-68$ km s$^{-1}$ and $-50$ km s$^{-1}$ reported by Nguyen et al. (2015). Focusing on the RCW 106 East and West region with the massive star formation having the bright infrared dust emission, we found that these regions have three different velocity components with $\sim 10$ km s$^{-1}$ differences. The two out of three velocity components show morphological correspondence with the infrared cold dust emission and connect with the bridge feature on a position-velocity diagram. Therefore, two molecular clouds (MCs) with $\sim 10$ km s$^{-1}$ differences are likely to be physically associated with massive star-forming regions in the GMC complex. Based on these observational results, we argue that mini-starbursts and massive star/cluster formation in the RCW 106 GMC complex are induced by supersonic cloud-cloud collisions in an agglomerate of molecular gas on the Scutum-Centurus arm.

Light Primordial Black Holes (LPBHs) with masses in the range $10$ g $\leq M_{\rm BH} \leq 10^9$ g, although they evaporate before Big Bang Nucleosynthesis, can play a significant role in the production of both Dark Matter and Dark Radiation. In particular, LPBHs can evaporate into light axions or axion-like particles (ALPs) with masses $m_a \lesssim$ MeV, contributing to the effective number of neutrino species, $\Delta N_{\rm eff}$. Additionally, heavy scalar particles known as moduli, predicted by String Theory, can be produced both via Hawking evaporation and through amplification by a mechanism called Superradiance Instability in the case of spinning PBHs. These moduli can subsequently decay into ALPs, further amplifying their abundance. In this work, we calculate the number density of ALPs in the presence of moduli enhanced by Superradiance for Kerr PBHs. Using current limits on $\Delta N_{\rm eff}$ from Planck satellite observations, we derive updated constraints on this scenario.

We present two transit observations of the $\sim$520K, 1.85R$_\oplus$, 4.0M$_\oplus$ super-Earth TOI-776b with JWST NIRSpec/G395H, resulting in a 2.8-5.2$\mu$m transmission spectrum. Producing reductions using the ExoTiC-JEDI and Eureka! pipelines, we obtain a median transit depth precision of 34ppm for both visits and both reductions in spectroscopic channels 30 pixels wide ($\sim$0.02$\mu$m). We find that our independent reductions produce consistent transmission spectra, however, each visit shows differing overall structure. For both reductions, a flat line is preferred for Visit 1 while a flat line with an offset between the NRS1 and NRS2 detectors is preferred for Visit 2; however, we are able to correct for this offset during our modeling analysis following methods outlined in previous literature. Using picaso forward models, we can rule out metallicities up to at least 100$\times$ solar with an opaque pressure of 10$^{-3}$ bar to $\geq$3$\sigma$ in all cases, however, the exact lower limit varies between the visits, with Visit 1 ruling out $\lesssim$100$\times$ solar while the lower limits for Visit 2 extend beyond $\sim$350$\times$ solar. Our results add to the growing list of super-Earth atmospheric constraints by JWST, which provide critical insight into the diversity and challenges of characterizing terrestrial planets.

We study the X-ray reverberation in active galactic nuclei (AGN) using the variational autoencoder (VAE), which is a machine-learning algorithm widely used for signal processing and feature reconstruction. While the X-ray reverberation signatures that contain the information of the accretion disk and the X-ray emitting corona are commonly analyzed in the Fourier domain, this work aims to extract the reverberation response functions directly from the AGN light curves. The VAE is trained using the simulated light curves that contain the primary X-rays from the lamp-post corona varying its height and the corresponding reflection X-rays from the disk. We use progressively more realistic light-curve models, such as those that include the effects of disk-propagating fluctuations and random noises, to assess the ability of the VAE to reconstruct the response profiles. Interestingly, the VAE can recognize the reverberation patterns on the light curves, hence the coronal height can be predicted. We then deploy the VAE model to the XMM-Newton data of IRAS 13224-3809 and directly estimate, for the first time, the response functions of this source in various observations. The result reveals the corona changing its height between $3~r_{\rm g}$ and $20~r_{\rm g}$, which is correlated with the source luminosity and in line with previous literature. Finally, we discuss the advantages and limitations of this method.

Black holes may accrete gas with angular momentum vectors misaligned with the black hole spin axis. The resulting accretion disks are subject to Lense-Thirring precession, and hence torque. Analytical calculations and simulations show that Lense-Thirring precession will warp, and, for large misalignments, fracture the disk. In GRMHD simulations, the warping or breaking occurs at $\lesssim10r_s$, where $r_s$ is the Schwarzschild radius. Considering that accretion disk spectra in the soft state of stellar-mass black holes are generally well modeled as multicolor blackbodies, the question arises as to how consistent warped and broken disks are with observations. Here, we analytically calculate thermal spectra of warped and broken disks with a warp or break radius at $10r_s$ for various disk inclinations. Due to self-irradiation and the projected area of the inclined disk regions, the spectra of inclined disks significantly deviate from multicolor blackbodies and do not follow the multicolor blackbody relation $\nu L_\nu\propto\nu^{\gamma}=\nu^{4/3}$ at low frequencies $\nu$. The power-law indices at low frequencies of the inclined disks vary with viewing angle; when viewed face-on, they vary between $\gamma\approx0.91-1.26$ for the warped disks and $\gamma\approx1.37-1.54$ for the broken disks depending on the inclination angle. The differences decrease when moving the location of the disk warp and break to larger radii; for inclined disks to emit as multicolor blackbodies, they must warp or break at radii $\geq50r_s$. Our results imply that accretion disks around black holes in the soft state warp or break at larger radii than suggested in GRHMD simulations.

We present an analytical model for density-split correlation functions, that probe galaxy clustering in different density environments. Specifically, we focus on the cross-correlation between density-split regions and the tracer density field. We show that these correlation functions can be expressed in terms of the two-point probability density function (PDF) of the density field, or equivalently, its bias function. We derive analytical predictions using three levels of approximation for the two-point PDF: a bivariate Gaussian distribution, a bivariate shifted log-normal distribution, and a prediction based on the Large Deviation Theory framework. Under spherical symmetry $\unicode{x2013}$ where spherical collapse dynamics apply, such as for count-in-cell densities with spherical top-hat smoothing $\unicode{x2013}$ LDT predicts the density two-point PDF in the large-separation regime relative to the smoothing radius. We validate our model against dark matter N-body simulations in real space, incorporating Poisson shot noise. Our results show that the LDT predictions outperform the log-normal approximation, and agrees with simulations on large scales within the cosmic variance of a typical DESI DR1 sample, despite relying on only one degree of freedom.

In the context of upcoming large-scale surveys like Euclid, the necessity for the automation of strong lens detection is essential. While existing machine learning pipelines heavily rely on the classification probability (P), this study intends to address the importance of integrating additional metrics, such as Information Content (IC) and the number of pixels above the segmentation threshold, to alleviate the false positive rate in unbalanced data-sets. In this work, we introduce a segmentation algorithm (U-Net) as a supplementary step in the established strong gravitational lens identification pipeline (Denselens), which primarily utilizes P$_{\rm mean}$ and IC$_{\rm mean}$ parameters for the detection and ranking. The results demonstrate that the inclusion of segmentation enables significant reduction of false positives by approximately 25 per cent in the final sample extracted from DenseLens, without compromising the identification of strong lenses. The main objective of this study is to automate the strong lens detection process by integrating these three metrics. To achieve this, a decision tree-based selection process is introduced, applied to the Kilo Degree Survey (KiDS) data. This process involves rank-ordering based on classification scores, filtering based on Information Content, and segmentation score. Additionally, the study presents 14 newly discovered strong lensing candidates identified by the U-Denselens network using the KiDS DR4 data.

We study linear scalar perturbations in single-field models of inflation featuring a non-attractor phase. These models lead to a peak in the curvature power spectrum that may result in the formation of primordial black holes. We develop a transfer-matrix formalism, analogous to the S-matrix program in quantum-field theory, that maps perturbations throughout the transitory phase. At scales smaller than the peak, the power spectrum features damped oscillations, and the duration of the transition sets the scale at which power-law damping switches to exponential damping. At scales larger than the peak, we demonstrate that a dip appears in the power spectrum if and only if the inflaton's velocity does not flip sign. We show that the amplitude at the dip always scales as the inverse square-rooted amplitude of the peak, and comment on the physical consequences of this universal relationship. We also test the robustness of our results with a few toy models and interpret them with an intuitive mechanical analogy.

Space weather, driven by solar flares and Coronal Mass Ejections (CMEs), poses significant risks to technological systems. Accurately forecasting these events and their impact on Earth's magnetosphere remains a challenge because of the complexity of solar-terrestrial interactions. This study applied artificial intelligence (AI) to predict the chain of events associated with the May $2024$ superstorm, including solar flares from NOAA active region 13644, Earth-directed CMEs, and a violent geomagnetic storm. Using magnetogram cut-outs, a Vision Transformer was able to classify the evolution of the active region morphologies, and a video-based deep learning method predicted the occurrence of solar flares; a physics-driven model improved the precision of CME travel-time prediction using coronal observations and solar wind measurements; and a data-driven method exploited these in situ measurements to sound alerts of the geomagnetic storm unrolled over time. The results showed unprecedented accuracy in predicting CME arrival with uncertainty as small as one minute. Moreover, these AI models outperformed traditional methods in predicting solar flares occurrences, onset, and recovery phases of the geomagnetic storm. These findings highlight the impressive potential of AI for space weather forecasting and as a tool to mitigate the impact of extreme solar events on critical infrastructure.

Massive star formation involves significant ionization in the innermost regions near the central object, such as gravitationally trapped H II regions, jets, ionized disks, or winds. Resolved observations of the associated continuum and recombination line emission are crucial for guiding theory. The next-generation Very Large Array (ngVLA) will enable unprecedented observations of thermal emission with 1 mas resolution, providing a new perspective on massive star formation at scales down to a few astronomical units at kiloparsec distances. This work presents synthetic interferometric ngVLA observations of the free-free continuum (93-GHz band), $\mathrm{H41\alpha}$, and $\mathrm{H38\alpha}$ recombination lines from ionized jets and disks around massive protostars. Using the sf3dmodels Python package, we generate gas distributions based on analytical models, which are then processed through the RADMC-3D radiative transfer code. Our results indicate that the ngVLA can easily resolve, both spatially and spectrally, the ionized jet from a 15 $\mathrm{M_\odot}$ protostar at 700 pc, distinguishing between collimated jets and wide-angle winds, and resolving their launching radii, widths, and any substructure down to a few astronomical units. Detailed studies of radio jets launched by massive protostars will be feasible up to distances of $\sim 2$ kpc. Furthermore, ngVLA will be able to study in detail the ionized disks around massive ($> 10~\mathrm{M_\odot}$) protostars up to distances from 4 to 12 kpc, resolving their kinematics and enabling the measurement of their central masses across the Galaxy. These observations can be conducted with on-source integrations of only a few hours.

Modern neural networks (NNs) often do not generalize well in the presence of a "covariate shift"; that is, in situations where the training and test data distributions differ, but the conditional distribution of classification labels remains unchanged. In such cases, NN generalization can be reduced to a problem of learning more domain-invariant features. Domain adaptation (DA) methods include a range of techniques aimed at achieving this; however, these methods have struggled with the need for extensive hyperparameter tuning, which then incurs significant computational costs. In this work, we introduce SIDDA, an out-of-the-box DA training algorithm built upon the Sinkhorn divergence, that can achieve effective domain alignment with minimal hyperparameter tuning and computational overhead. We demonstrate the efficacy of our method on multiple simulated and real datasets of varying complexity, including simple shapes, handwritten digits, and real astronomical observations. SIDDA is compatible with a variety of NN architectures, and it works particularly well in improving classification accuracy and model calibration when paired with equivariant neural networks (ENNs). We find that SIDDA enhances the generalization capabilities of NNs, achieving up to a $\approx40\%$ improvement in classification accuracy on unlabeled target data. We also study the efficacy of DA on ENNs with respect to the varying group orders of the dihedral group $D_N$, and find that the model performance improves as the degree of equivariance increases. Finally, we find that SIDDA enhances model calibration on both source and target data--achieving over an order of magnitude improvement in the ECE and Brier score. SIDDA's versatility, combined with its automated approach to domain alignment, has the potential to advance multi-dataset studies by enabling the development of highly generalizable models.

In this paper, we perform a dynamical systems study of the purely kinetic k-essence. Although these models have been studied in the past, a full study of the dynamics in the phase space incorporating the stability conditions for theoretical consistency is lacking. Our results confirm in a very rigorous and clear way that these models i) can not explain in a unified way the dark matter and dark energy components of the cosmic fluid and ii) are not adequate to explain the existing observational evidence, in particular the observed amount of cosmic structure.

The stochastic gravitational wave background (SGWB) is one of the main detection targets for future millihertz space-borne gravitational-wave observatories such as the \ac{LISA}, TianQin, and Taiji. For a single LISA-like detector, a null-channel method was developed to identify the SGWB by integrating data from the A and E channels with a noise-only T channel. However, the noise monitoring channel will not be available if one of the laser interferometer arms fails. By combining these detectors, it will be possible to build detector networks to search for SGWB via cross-correlation this http URL this work, we developed a Bayesian data analysis method based on \ac{TDI} Michelson-type channel. We then investigate the detectability of the TianQin-LISA detector network for various isotropic SGWB. Assuming a three-month observation, the TianQin-LISA detector network could be able to confidently detect SGWB with energy density as low as $\Omega_{\rm PL} = 6.0 \times 10^{-13}$, $\Omega_{\rm Flat} = 2.0 \times 10^{-12}$ and $\Omega_{\rm SP} = 1.2 \times 10^{-12}$ for power-law, flat and single-peak models, respectively.

We investigate the properties of the Schwarzschild black hole geometry involving leading one-loop long-distance quantum effects, which arise within the framework of effective field theories of gravity. Our analysis reveals that geodesic trajectories of both massive and massless particles can assume completely different behaviors depending on the sign assumed by the quantum contributions, in spite of their smallness. Moreover, we find that the positions of stable and unstable circular orbits are determined by an algebraic quartic equation, which we solve by developing a straightforward and analytic method. Additionally, we examine black hole shadows and rings by means of two different emission profile models, which account for quantum corrections to the innermost stable circular orbit and photon sphere radii. The Hawking temperature and the entropy of the black hole are also derived. Finally, we draw our conclusions.

The density fluctuations in the nearly homogeneous background in the very early universe are argued to be the origin of the cosmic structures we observe in our present universe. Along with many other structures, these fluctuations would have also given rise to primordial black holes at the end of unhindered gravitational collapse of high density matter blobs that developed due to fluctuations. We study here such a collapse in the inflationary epoch which has been assumed earlier to form primordial black holes. The potentials for inflation are chosen to be a general polynomial in its scalar field $V(\phi) \propto \phi^n$. Examining the dynamics of such a collapse, we find the parameter range where the apparent horizon does not form, thus resulting in the visibility of the final singularity of collapse for faraway external observers. This treatment is within the classical limits, dictated by Planck's constraints. The slow-roll parameters are analysed here to keep the relic abundance of the inflationary field high enough so that the abundance of produced primordial naked singularities (PNaSs) fall within the range of resolution of possible observational probes. $\textbf{key words}$: Unhindered gravitational collapse (UGC), Apparent Horizon (AH), Primordial black hole (PBH), Primordial naked singularity (PNaS).