Papers for Friday, Mar 08 2024

We conduct a thorough analysis of seismic and acoustic data from the so-called `Interstellar Meteor' which entered the Earth's atmosphere off the coast of Papua New Guinea on 2014-01-08. We conclude that both previously-reported seismic signals are spurious - one has characteristics suggesting a local vehicular-traffic based origin; whilst the other is statistically indistinguishable from the background noise. As such, previously-reported localisations based on this data are spurious. Analysis of acoustic data cannot provides a best fit location estimate which is very far ($\sim$170~km) from the reported fireball location. Accordingly, we conclude that material recovered from the seafloor and purported to be from the meteor is almost certainly unrelated to it, and is likely of more mundane (non-interstellar) origin.

We present new ALMA observations of CO, CN, CS, HCN and HCO$^{+}$ absorption seen against the bright and compact radio continuum sources of eight massive galaxies. Combined with archival observations, they reveal two distinct populations of molecular clouds, which we identify by combining CO emission and absorption profiles to unambiguously reveal each cloud's direction of motion and likely location. In galaxy disks, we see clouds with low velocity dispersions, low line of sight velocities and a lack of any systemic inflow or outflow. In galactic cores, we find high velocity dispersion clouds inflowing at up to 550 km/s. This provides observational evidence in favour of cold accretion onto galactic centres, which likely contributes to the fuelling of active galactic nuclei. We also see a wide range in the CO(2-1)/CO(1-0) ratios of the absorption lines. This is likely the combined effect of hierarchical substructure within the molecular clouds and continuum sources which vary in size with frequency.

The study of gas-phase metallicity and its spatial distribution at high redshift is crucial to understand the processes that shaped the growth and evolution of galaxies in the early Universe. Here we study the spatially resolved metallicity in three systems at $z\sim6-8$, namely A2744-YD4, BDF-3299, and COSMOS24108, with JWST NIRSpec IFU low-resolution ($R$ $\sim$ 100) spectroscopic observations. These are among the highest-$z$ sources in which metallicity gradients have been probed so far. Each of these systems hosts several spatial components in the process of merging within a few kiloparsecs, identified from the rest-frame UV and optical stellar continuum and ionised gas emission line maps. The sources have heterogeneous properties, with stellar masses log($M_*/M_\odot) \sim 7.6-9.3$, star formation rates (SFRs) $\sim1-15$ $M_\odot$ yr$^{-1}$, and gas-phase metallicities 12+log(O/H) $\sim 7.7-8.3$, which exhibit a large scatter within each system. Their properties are generally consistent with those of the highest-redshift samples to date ($z\sim3-10$), though the sources in A2744-YD4 and COSMOS24108 are at the high end of the mass-metallicity relation (MZR) defined by the $z\sim3-10$ sources. Moreover, the targets in this work follow the predicted slope of the MZR at $z\sim 6-8$ from most cosmological simulations. The gas-phase metallicity gradients are consistent with being flat in the main sources of each system. Flat metallicity gradients are thought to arise from gas mixing processes on galaxy scales, such as mergers or galactic outflows and SN winds driven by intense stellar feedback, which wash out any gradient formed in the galaxy. The existence of flat gradients at $z\sim6-8$ sets also important constraints on cosmological simulations, whose predictions on the cosmic evolution of metallicity gradients often differ significantly, especially at high redshift.

The connection between active galactic nuclei (AGN) and their host dark matter halos provides powerful insights into how supermassive black holes (SMBHs) grow and coevolve with their host galaxies. Here we investigate the impact of observational AGN selection on the AGN halo occupation distribution (HOD) by forward-modeling AGN activity into cosmological N-body simulations. By assuming straightforward relationships between the SMBH mass, galaxy mass, and (sub)halo mass, as well as a uniform broken power law distribution of Eddington ratios, we find that luminosity-limited AGN samples result in biased HOD shapes. While AGN defined by an Eddington ratio threshold produce AGN fractions that are flat across halo mass (unbiased by definition), luminosity-limited AGN fractions peak around galaxy-group-sized halo masses and then decrease with increasing halo mass. With higher luminosities, the rise of the AGN fraction starts at higher halo masses, the peak is shifted towards higher halo masses, and the decline at higher halo masses is more rapid. These results are consistent with recent HOD constraints from AGN clustering measurements, which find (1) characteristic halo mass scales of $\log M_{Vir}\sim$ 12 - 13 [$h^{-1}M_{\odot}$] and (2) a shallower rise of the number of satellite AGN with increasing halo mass than for the overall galaxy population. Thus the observational biases due to AGN selection can naturally explain the constant, characteristic halo mass scale inferred from large-scale AGN clustering amplitudes over a range of redshifts, as well as the measured inconsistencies between AGN and galaxy HODs. We conclude that AGN selection biases can have significant impacts on the inferred AGN HOD, and can therefore lead to possible misinterpretations of how AGN populate dark matter halos and the AGN-host galaxy connection.

We present new optical GTC/MEGARA seeing-limited (0.9") integral-field observations of NGC 5506, together with ALMA observations of the CO(3-2) transition at a 0.2" (25 pc) resolution. NGC 5506 is a luminous (bolometric luminosity of $\sim 10^{44}$ erg/s) nearby (26 Mpc) Seyfert galaxy, part of the Galaxy Activity, Torus, and Outflow Survey (GATOS). We modelled the CO(3-2) kinematics with 3D-Barolo, revealing a rotating and outflowing cold gas ring within the central 1.2 kpc. We derived an integrated cold molecular gas mass outflow rate for the ring of 8 M$_{\odot}$/yr. We fitted the optical emission lines with a maximum of two Gaussian components to separate rotation from non-circular motions. We detected high [OIII]$\lambda$5007 projected velocities (up to 1000 km/s) at the active galactic nucleus (AGN) position, decreasing with radius to an average 330 km/s around 350 pc. We also modelled the [OIII] gas kinematics with a non-parametric method, estimating the ionisation parameter and electron density in every spaxel, from which we derived an ionised mass outflow rate of 0.076 M$_{\odot}$/yr within the central 1.2 kpc. Regions of high CO(3-2) velocity dispersion, extending to projected distances of 350 pc from the AGN, appear to be the result from the interaction of the AGN wind with molecular gas in the galaxy's disc. Additionally, we find the ionised outflow to spatially correlate with radio and soft X-ray emission in the central kiloparsec. We conclude that the effects of AGN feedback in NGC 5506 manifest as a large-scale ionised wind interacting with the molecular disc, resulting in outflows extending to radial distances of 610 pc

We investigate the group-scale environment of 15 luminous quasars (luminosity $L_{\rm 3000}>10^{46}$ erg s$^{-1}$) from the Cosmic Ultraviolet Baryon Survey (CUBS) at redshift $z\approx1$. Using the Multi Unit Spectroscopic Explorer (MUSE) integral field spectrograph on the Very Large Telescope (VLT), we conduct a deep galaxy redshift survey in the CUBS quasar fields to identify group members and measure the physical properties of individual galaxies and galaxy groups. We find that the CUBS quasars reside in diverse environments. The majority (11 out of 15) of the CUBS quasars reside in overdense environments with typical halo masses exceeding $10^{13}{\rm M}_{\odot}$, while the remaining quasars reside in moderate-size galaxy groups. No correlation is observed between overdensity and redshift, black hole (BH) mass, or luminosity. Radio-loud quasars (5 out of 15 CUBS quasars) are more likely to be in overdense environments than their radio-quiet counterparts in the sample, consistent with the mean trends from previous statistical observations and clustering analyses. Nonetheless, we also observe radio-loud quasars in moderate groups and radio-quiet quasars in overdense environments, indicating a large scatter in the connection between radio properties and environment. We find that the most UV luminous quasars might be outliers in the stellar mass-to-halo mass relations or may represent departures from the standard single-epoch BH relations.

The majority of massive stars are expected to exchange mass or merge with a companion during their lives. This immediately implies that most supernovae (SNe) are from such post-mass-exchange objects. Here, we explore how mass accretion and merging affect the pre-SN structures of stars and their final fates. We use the stellar evolution code MESA, infer the outcome of core-collapse using a neutrino-driven SN model, and apply a rapid-accretion model. Our models cover initial masses from 11 to 70 Msun and the accreted mass ranges from 10-200% of the initial mass. We find that mass accretion in particular onto post-main-sequence (post-MS) stars can lead to a long-lived blue supergiant (BSG) phase. In comparison to genuine single stars, post-MS accretors have small core-to-total mass ratios, regardless of whether they end their lives as BSGs or cool supergiants (CSGs), and they can have genuinely different pre-SN core structures. As in single and binary-stripped stars, we find black-hole (BH) formation for the same characteristic CO core masses M_CO of ~7 Msun and >13 Msun. In models with the largest mass accretion, the BH-formation landscape as a function of M_CO is shifted by about 0.5 Msun to lower masses. We find a tight relation between our neutron-star (NS) masses and the central entropy of the pre-SN models, suggesting a universal relation that is independent of the evolutionary history of stars. Post-MS accretors explode both as BSGs and CSGs, and we show how to understand their pre-SN locations in the Hertzsprung--Russell diagram. Some BSGs that avoid the luminous-blue-variable (LBV) regime are predicted to collapse into BHs of up to 50 Msun while others explode in supernovae and eject up to 40 Msun, greatly exceeding ejecta masses from single stars. These masses can be even higher at lower metallicities, and they may fall into the pair-instability-supernova mass gap. [abridged]

We present the High-$z$ Evolution of Large and Luminous Objects (HELLO) project, a set of more than 30 high-resolution hydrodynamical cosmological simulations aimed to study Milky Way analogues ($M_\star\sim10^{10-11}$ $\mathrm{M}_\odot$) at high redshift, namely at $z=3.6$ (age $\sim$ 1.7 Gyr) and $z=2$ (age $\sim$ 3.3 Gyr). The HELLO project features an updated scheme for chemical enrichment and the addition of local photoionization feedback processes. Independently of redshift and stellar mass, all galaxies follow a similar evolutionary path: (i) first a smooth progression along the star formation main sequence, where galaxies grow in both stellar mass and size, (ii) a (short) period of intense star formation, which causes a contraction phase in the stellar size, until the galaxies reach their peak star formation rate (SFR), during this period we also witness a significant black hole growth, and (iii) the onset of declining SFRs, which is due to a mix of gas consumption, stellar feedback, and AGN feedback, but with AGN feedback still being subdominant with respect to stellar feedback for energy deposition. The exact phase in which a galaxy in our mass range can be found at a given redshift is set by its gas reservoir and assembly history. Finally, our galaxies are in excellent agreement with several various scaling relations observed with the Hubble Space Telescope and the James Webb Space Telescope, and hence can be used to provide the theoretical framework to interpret current and future observations from these facilities and shed light on the transition from star-forming to quiescent galaxies.

Aims. The goal of this work is to devise a description of the enrichment process in large-scale structure that explains the available observations and makes predictions for future measurements. Methods. We took a spartan approach to this study, employing observational results and algebra to connect stellar assembly in star-forming halos with metal enrichment of the intra-cluster and group medium. Results. On one hand, our construct is the first to provide an explanation for much of the phenomenology of metal enrichment in clusters and groups. It sheds light on the lack of redshift evolution in metal abundance, as well as the small scatter of metal abundance profiles, the entropy versus abundance anti-correlation found in cool core clusters, and the so-called Fe conundrum, along with several other aspects of cluster enrichment. On the other hand, it also allows us to infer the properties of other constituents of large-scale structure. We find that gas that is not bound to halos must have a metal abundance similar to that of the ICM and only about one-seventh to one-third of the Fe in the Universe is locked in stars. A comparable amount is found in gas in groups and clusters and, lastly and most importantly, about three-fifths of the total Fe is contained in a tenuous warm or hot gaseous medium in or between galaxies. We point out that several of our results follow from two critical but well motivated assumptions: 1) the stellar mass in massive halos is currently underestimated and 2) the adopted Fe yield is only marginally consistent with predictions from synthesis models and SN rates. Conclusions. One of the most appealing features of the work presented here is that it provides an observationally grounded construct where vital questions on chemical enrichment in the large-scale structure can be addressed. We hope that it may serve as a useful baseline for future works.

We present the direct imaging discovery of a substellar companion (a massive planet or low-mass brown dwarf) to the young, $\gamma$ Doradus-type variable star, HIP 39017 (HD 65526). The companion's SCExAO/CHARIS JHK ($1.1-2.4\mu$m) spectrum and Keck/NIRC2 L$^{\prime}$ photometry indicate that it is an L/T transition object. A comparison of the JHK+L$^{\prime}$ spectrum to several atmospheric model grids finds a significantly better fit to cloudy models than cloudless models. Orbit modeling with relative astrometry and precision stellar astrometry from Hipparcos and Gaia yields a semi-major axis of $23.8^{+8.7}_{-6.1}$ au, a dynamical companion mass of $30^{+31}_{-12}$~M$_J$, and a mass ratio of $\sim$1.9\%, properties most consistent with low-mass brown dwarfs. However, its mass estimated from luminosity models is a lower $\sim$13.8 $M_{\rm J}$ due to an estimated young age ($\lesssim$ 115 Myr); using a weighted posterior distribution informed by conservative mass constraints from luminosity evolutionary models yields a lower dynamical mass of $23.6_{-7.4}^{+9.1}$~M$_J$ and a mass ratio of $\sim$1.4\%. Analysis of the host star's multi-frequency $\gamma$ Dor-type pulsations, astrometric monitoring of HIP 39017b, and Gaia DR4 astrometry of the star will clarify the system age and better constrain the mass and orbit of the companion. This discovery further reinforces the improved efficiency of targeted direct imaging campaigns informed by long-baseline, precision stellar astrometry.

Dual quasars, two active supermassive black holes at galactic scales, represent crucial objects for studying the impact of galaxy mergers and quasar activity on the star formation rate (SFR) within their host galaxies, particularly at cosmic noon when SFR peaks. We present JWST/MIRI mid-infrared integral field spectroscopy of J074922.96+225511.7, a dual quasar with a projected separation of 3.8 kilo-parsec at a redshift $z$ of 2.17. We detect spatially extended [Fe II] 5.34$\rm \mu$m and polycyclic aromatic hydrocarbon (PAH) 3.3$\mu$m emissions from the star formation activity in its host galaxy. We derive the SFR of 10$^{3.0\pm0.2}$ M$_{\odot}$ yr$^{-1}$ using PAH 3.3$\mu$m, which is five times higher than that derived from the cutoff luminosity of the infrared luminosity function for galaxies at $z\sim2$. While the SFR of J0749+2255 agrees with that of star-forming galaxies of comparable stellar mass at the same redshifts, its molecular gas content falls short of expectations based on the molecular Kennicutt-Schmidt law. This discrepancy may result from molecular gas depletion due to the longer elevated stage of star formation, even after the molecular gas reservoir is depleted. We do not observe any quasar-driven outflow that impacts PAH and [Fe II]\ in the host galaxy based on the spatially resolved maps. From the expected flux in PAH-based star formation, the \feii\ line likely originates from the star-forming regions in the host galaxy. Our study highlights the stardust nature of J0749+2255, indicating a potential connection between the dual quasar phase and intense star formation activities.

The measurements of the bulk properties of most isolated neutron stars (INSs) are challenging tasks. Tang et al. (2020) have developed a new method, based on the equation of state (EoS) of neutron star (NS) material constrained by the observational data, to infer the gravitational masses of a few INSs whose gravitational redshifts are available. However, in that work, the authors only considered the constraints on the EoS from nuclear experiments/theories and the gravitational wave data of GW170817; the possible phase transition has not been taken into account. In this work, we adopt three EoS models (including the one incorporates a first-order strong phase transition) that are constrained by the latest multimessenger NS data, including in particular the recent mass\textendash radius measurements of two NSs by Neutron Star Interior Composition Explorer, to update the estimation of the gravitational masses of RBS 1223, RX J0720.4-3125, and RX J1856.5-3754. In comparison to our previous approach, the new constraints are tighter, and the gravitational masses are larger by about $0.1M_\odot$. All the inferred gravitational masses are within the range of the NS masses measured in other ways. We have also calculated the radius, tidal-deformability, and moment of inertia of these sources. The inclusion of the first-order strong phase transition has little influence on modifying the results.

The origin of the stellar Initial Mass Function (IMF) and how it may vary with galactic environment is a matter of debate. Certain star formation theories involve a close connection between the IMF and the Core Mass Function (CMF) and so it is important to measure this CMF in a range of locations in the Milky Way. Here we study the CMF of three Galactic Center clouds: G0.253+0.016 ("The Brick"), Sgr B2 (Deep South field) and Sgr C. We use ALMA 1 mm continuum images and identify cores as peaks in thermal dust emission via the dendrogram algorithm. We develop a completeness correction method via synthetic core insertion, where a realistic mass-dependent size distribution is used for the synthetic cores. After corrections, a power law of the form $\text{d}N/\text{d}\log M \propto M^{-\alpha}$ is fit to the CMFs above 2 M$_\odot$. The three regions show disparate CMFs, with the Brick showing a Salpeter-like power law index $\alpha=1.21\pm0.11$ and the other two regions showing shallower indices ($\alpha=0.92\pm0.09$ for Sgr C and $\alpha=0.66\pm0.05$ for Sgr B2-DS). Furthermore, we analyze the spatial distribution and mass segregation of cores in each region. Sgr C and Sgr B2-DS show signs of mass segregation, but the Brick does not. We compare our results to several other CMFs from different Galactic regions derived with the same methods. Finally, we discuss how these results may help define an evolutionary sequence of star cluster formation and can be used to test star formation theories.

Context. Known Mars trojans could be primordial small bodies that have remained in their present-day orbits for the age of the Solar System. Their orbital distribution is strongly asymmetric; there are over a dozen objects at the L5 point and just one at L4, (121514) 1999 UJ7. Most L5 trojans appear to form a collision-induced asteroid cluster, known as the Eureka family. Asteroid 2023 FW14 was recently discovered and it has a robust orbit determination that may be consistent with a Mars trojan status. Aims. Our aim is determine the nature and dynamical properties of 2023 FW14. Methods. We carried out an observational study of 2023 FW14 to derive its spectral class using the OSIRIS camera spectrograph at the 10.4 m Gran Telescopio Canarias. We investigated its possible trojan resonance with Mars using direct N-body simulations. Results. The reflectance spectrum of 2023 FW14 is not compatible with the olivine-rich composition of the Eureka family; it also does not resemble the composition of the Moon, although (101429) 1998 VF31 does. The Eureka family and 101429 are at the L5 point. The spectrum of 2023 FW14 is also different from two out of the three spectra in the literature of the other known L4 trojan, 121514, which are of C-type. The visible spectrum of 2023 FW14 is consistent with that of an X-type asteroid, as is the third spectrum of 121514. Our calculations confirm that 2023 FW14 is the second known L4 Mars trojan although it is unlikely to be primordial; it may remain in its present-day tadpole path for several million years before transferring to a Mars-crossing orbit. It might be a fragment of 121514, but a capture scenario seems more likely. Conclusions. The discovery of 2023 FW14 suggests that regular Mars-crossing asteroids can be captured as temporary Mars trojans.

For 3D magnetic reconnection to occur there must exist a volume within which the electric field component parallel to the magnetic field is non-zero. In numerical experiments, locations of non-zero parallel electric field indicate sites of 3D magnetic reconnection. If these experiments contain all types of topological feature (null points, separatrix surfaces, spines and separators) then comparing topological features with the reconnection sites reveals that all the reconnection sites are threaded by separators with the local maxima/minima of the integrated parallel electric along fieldlines coinciding with these separators. However, not all separators thread a reconnection site. Furthermore, there are different types of separator. Cluster separators are short arising within an individual weak magnetic field region and have negligible parallel electric field along them so are not associated with much reconnection. Intercluster separators connect a positive null point lying in one weak-field region to a negative null point that lies in a different weak-field region. Intercluster separators often thread enhanced regions of parallel electric field and are long. Since separators form the boundary between 4 globally-significant topologically-distinct domains, they are important sites of reconnection which can results in the global restructuring of the magnetic field. By considering the kinematic bifurcation models in which separators form it is possible to understand the formation of cluster and intercluster separators and explain their key properties.

High angular resolution imaging is an increasingly important capability in contemporary astrophysics. Of particular relevance to emerging fields such as the characterisation of exoplanetary systems, imaging at the required spatial scales and contrast levels results in forbidding challenges in the correction of atmospheric phase errors, which in turn drives demanding requirements for precise wavefront sensing. Asgard is the next-generation instrument suite at the European Southern Observatory's Very Large Telescope Interferometer (VLTI), targeting advances in sensitivity, spectral resolution and nulling interferometry. In this paper, we describe the requirements and designs of three core modules: Heimdallr, a beam combiner for fringe tracking, low order wavefront correction and visibility science; Baldr, a Zernike wavefront sensor to correct high order atmospheric aberrations; and Solarstein, an alignment and calibration unit. In addition, we draw generalisable insights for designing such system and discuss integration plans.

In modeling the potentials of quadruply lensed quasars, investigators often employ models for the stellar surface brightness profile of the lensing galaxy for the sole purpose of eliminating its contamination of the light from the quasar images and their hosts. When the center of that profile is used, it is usually as a weak prior on the center of the potential. But the central maxima in the light from single lensing galaxies lie closer the centers of the lens potentials than has heretofore been thought. New measurements are presented here of the positions of the compact central regions of lensing galaxies observed with the Hubble Space Telescope. Comparing these with modeled positions for the centers of the lensing potential (constrained only by the positions of the four quasar images) we find agreement consistent with the larger of either our measurement uncertainties or 1% of the radius of the Einstein ring.

We use FIRE-2 zoom simulations of Milky Way size disk galaxies to derive easy-to-use relationships between the observed circular speed of the Galaxy at the Solar location, $v_\mathrm{c}$, and dark matter properties of relevance for direct detection experiments: the dark matter density, the dark matter velocity dispersion, and the speed distribution of dark matter particles near the Solar location. We find that both the local dark matter density and 3D velocity dispersion follow tight power laws with $v_\mathrm{c}$. Using this relation together with the observed circular speed of the Milky Way at the Solar radius, we infer the local dark matter density and velocity dispersion near the Sun to be $\rho = 0.42\pm 0.06\,\mathrm{GeV\,cm^{-3}}$ and $\sigma_\mathrm{3D} = 280^{+19}_{-18}\,\mathrm{km\,s^{-1}}$. We also find that the distribution of dark matter particle speeds is well-described by a modified Maxwellian with two shape parameters, both of which correlate with the observed $v_{\rm c}$. We use that modified Maxwellian to predict the speed distribution of dark matter near the Sun and find that it peaks at a most probable speed of $250\,\mathrm{km\,s^{-1}}$ and begins to truncate sharply above $470\,\mathrm{km\,s^{-1}}$. This peak speed is somewhat higher than expected from the standard halo model, and the truncation occurs well below the formal escape speed to infinity, with fewer very-high-speed particles than assumed in the standard halo model.

Abbreviation. Thermal diffusion is one of the basic processes for the mobility and formation of species on cosmic dust grains. Recent laboratory measurements have found that the diffusion pre-exponential factor can differ from that for desorption by several orders of magnitude. We aim to evaluate the effect of the newly experimentally measured diffusion pre-exponential factor on the chemistry under cold molecular cloud conditions. We found that statistically, more than half of the total gas-phase and grain surface species are not affected by the new pre-exponential factor after a chemical evolution of 10$^5$ yr. The most abundant gas-phase CO and grain surface water ice are not affected by the new pre-exponential factor. For the grain surface species that are affected, compared to the commonly adopted value of the pre-exponential factor for diffusion used in the chemical models, they could be either overproduced or underproduced with the lower diffusion pre-factor used in this work. The former case applies to radicals and the species that serve as reactants, while the latter case applies to complex organic molecules (COMs) on the grain and the species that rarely react with other species. Gas-phase species could also be affected due to the desorption of the grain surface species. The abundance of some gas-phase COMs could be varied by over one order of magnitude depending on the adopted grain surface temperature and/or the ratio of diffusion to desorption energy in the model. Key species whose diffusion pre-exponential factor significantly affects the model predictions were also evaluated, and these specie include CH3OH, H2CO, and NO. The results presented in this study show that the pre-exponential factor is one of the basic and important parameters in astrochemical models.

Simulations of pre-supernova evolution suggest that some intense shell burning can be so active that, in extreme cases, it can merge with the outer shell, changing the initial conditions for the supernova explosion. However, such violent activity in the interior of stars has been difficult to confirm from observations of stars. Here we propose that the elemental composition of O-rich ejecta in supernova remnants can be a tool to test for this kind of intense shell burning activity in the final stages of progenitor evolution. As an example, we discuss the origin of "Mg-rich" ejecta in the supernova remnant N49B. A high Mg/Ne mass ratio $\gtrsim 1$ suggests that the Ne- or O-burning shell has broken into or merged with the outer shell before the collapse. Such Mg-rich (or Ne-poor) ejecta has been identified in some other supernova remnants, supporting the idea that some destratification process, such as a shell merger, does indeed occur in the interiors of some massive stars, although they may not be the majority. Our results suggest that X-ray observations of O-rich ejecta in core-collapse supernova remnants will be a unique tool to probe the shell burning activity during the final stage of a massive star's interior.

In our Galactic Center, about 10,000 to 100,000 stars are estimated to have survived tidal disruption events, resulting in partially disrupted remnants. These events occur when a supermassive black hole (SMBH) tidally interacts with a star, but not enough to completely disrupt the star. We use the 1D stellar evolution code Kepler and the 3D smoothed particle hydrodynamics code Phantom to model the tidal disruption of 1, 3, and 10 solar mass stars at zero-age (ZAMS), middle-age (MAMS), and terminal-age main-sequence (TAMS). We map the disruption remnants into Kepler in order to understand their post-distribution evolution. We find distinct characteristics in the remnants, including increased radius, rapid core rotation, and differential rotation in the envelope. The remnants undergo composition mixing that affects their stellar evolution. Whereas the remnants formed by disruption of ZAMS models evolve similarly to unperturbed models of the same mass, for MAMS and TAMS stars, the remnants have higher luminosity and effective temperature. Potential observational signatures include peculiarities in nitrogen and carbon abundances, higher luminosity, rapid rotation, faster evolution, and unique tracks in the Hertzsprung-Russell diagram

We report multi-frequency and multi-epoch VLBI studies of the sub-parsec jet in Sombrero galaxy (M 104, NGC 4594). Using Very Long Baseline Array data at 12, 22, 44, and 88 GHz, we study the kinematics of the jet and the properties of the compact core. The sub-parsec jet is clearly detected at 12 and 22 GHz, and the inner jet base is resolved down to $\sim70$ Schwarzschild radii ($R_{\rm s}$) at 44 GHz. The proper motions of the jet are measured with apparent sub-relativistic speeds of $0.20\pm0.08 c$ and $0.05\pm0.02 c$ for the approaching and the receding jet, respectively. Based on the apparent speed and jet-to-counter-jet brightness ratio, we estimate the jet viewing angle to be larger than $\sim37^{\circ}$, and the intrinsic speed to be between $\sim0.10 c$ and $0.40 c$. Their joint probability distribution suggests the most probable values of the viewing angle and intrinsic speed to be ${66^{\circ}}^{+4^\circ}_{-6^\circ}$ and $0.19\pm0.04 c$, respectively. We also find that the measured brightness temperatures of the core at 12, 22 and 44 GHz are close to the equipartition brightness temperature, indicating that the energy density of the radiating particles is comparable to the energy density of the magnetic field in the sub-parsec jet region. Interestingly, the measured core size at 88 GHz ($\sim25\pm5 R_{s}$) deviates from the expected frequency dependence seen at lower frequencies. This may indicate a different origin for the millimeter emission, which can explained by an Advection Dominated Accretion Flow (ADAF) model. This model further predicts that at 230 and 340 GHz, the ADAF may dominate the radio emission over the jet.

This paper shows that accretion of positronium plasma between 0.01 to 14s after the Big Bang could have created small black holes contributing at least 1 percent of the dark matter present today, with uncertainties ranging from 10 percent or more. General relativistic magnetohydrodynamic (GRMHD) simulations newly adapted to the early Universe confirm that accretion is due to magneto-rotational instability (MRI) in a rotating plasma. By contrast with Bondi accretion producing primordial masses bigger than the Sun, MRI could produce masses 10^{15-18} g observable by their Hawking radiation contributing to background gamma rays.

Impact craters are the primary geomorphic features on the surfaces of celestial bodies such as the Moon, and their formation has significant implications for the evolutionary history of the celestial body. The study of the impact crater formation process relies mainly on numerical simulation methods, with two-dimensional simulations capable of reproducing general patterns of impact processes while conserving computational resources. However, to mitigate the artificial reflections of shock waves at numerical boundaries, a common approach involves expanding the computational domain, greatly reducing the efficiency of numerical simulations. In this study, we developed a novel two-dimensional code SALEc-2D that employs the perfect matched layer (PML) method to suppress artificial reflections at numerical boundaries. This method enhances computational efficiency while ensuring reliable results. Additionally, we implemented MPI parallel algorithms in the new code to further improve computational efficiency. Simulations that would take over ten hours using the conventional iSALE-2D code can now be completed in less than half an hour using our code, SALEc-2D, on a standard computer. We anticipate that our code will find widespread application in numerical simulations of impact craters in the future.

Context: Magnetic fields can play crucial roles in high-mass star formation. Nonetheless, the significance of magnetic fields at various scales and their relationship with gas structures is largely overlooked. Aims: Our goal is to examine the relationship between the magnetic field and molecular gas structures within the Orion A giant molecular cloud at different scales and density regimes. Methods: We assess the gas intensity structures and column densities in Orion A by utilizing $^{12}$CO, $^{13}$CO, and C$^{18}$O from Nobeyama observations. Through comparing Nobeyama observations with {\it{Planck}} polarization observations on large scales ($\sim0.6$ pc) and JCMT polarization observations on small scales ($\sim0.04$ pc), we investigate how the role of magnetic fields change with scale and density. Results: We find a similar trend from parallel to perpendicular alignment with increasing column densities in Orion A at both large and small spatial scales. Besides, when changing from low-density to high-density tracers, the relative orientation preference changes from random to perpendicular. The self-similar results at different scales indicate that magnetic fields are dynamically important in both cloud formation and filament formation. However, magnetic fields properties at small scales are relative complicated, and the interplay between magnetic field and star-forming activities needs to be discussed case-by-case.

There is solid theoretical and observational motivation behind the idea of scale-invariance as a fundamental symmetry of Nature. We consider a recently proposed classically scale-invariant inflationary model, quadratic in curvature and featuring a scalar field non-minimally coupled to gravity. We go beyond earlier analytical studies, which showed that the model predicts inflationary observables in qualitative agreement with data, by solving the full two-field dynamics of the system -- this allows us to corroborate previous analytical findings and set robust constraints on the model's parameters using the latest Cosmic Microwave Background (CMB) data from Planck and BICEP/Keck. We demonstrate that scale-invariance constrains the two-field trajectory such that the effective dynamics are that of a single field, resulting in vanishing entropy perturbations and protecting the model from destabilization effects. We derive tight upper limits on the non-minimal coupling strength, excluding conformal coupling at high significance. By explicitly sampling over them, we demonstrate an overall insensitivity to initial conditions. We argue that the model \textit{predicts} a minimal level of primordial tensor modes set by $r \gtrsim 0.003$, well within the reach of next-generation CMB experiments. These will therefore provide a litmus test of scale-invariant inflation, and we comment on the possibility of distinguishing the model from Starobinsky and $\alpha$-attractor inflation. Overall, we argue that scale-invariant inflation is in excellent health, and possesses features which make it an interesting benchmark for tests of inflation from future CMB data.

We provide an analysis of a convolutional neural network's ability to identify the lensing signal of single dark matter subhalos in strong galaxy-galaxy lenses in the presence of increasingly complex source light morphology. We simulate a balanced dataset of 800,000 strong lens images both perturbed and unperturbed by a single subhalo ranging in virial mass between $10^{7.5} M_{\odot} - 10^{11}M_{\odot}$ and characterise the source complexity by the number of Sersic clumps present in the source plane ranging from 1 to 5. Using the ResNet50 architecture we train the network to classify images as either perturbed or unperturbed. We find that the network is able to detect subhalos at low enough masses to distinguish between dark matter models even with complex sources and that source complexity has little impact on the accuracy beyond 3 clumps. The model was more confident in its classification when the clumps in the source were compact, but cared little about their spatial distribution. We also tested for the resolution of the data, finding that even in conditions akin to natural seeing the model was still able to achieve an accuracy of 74% in our highest peak signal-to-noise datasets, though this is heavily dominated by the high mass subhalos. It's robustness against resolution is attributed to the model learning the flux ratio anomalies in the perturbed lenses which are conserved in the lower resolution data.

The fitting of spectral lines is a common step in the analysis of line observations and simulations. However, the observational noise, the presence of multiple velocity components, and potentially large data sets make it a non-trivial task. We present a new computer program Spectrum Iterative Fitter (SPIF) for the fitting of spectra with Gaussians or with hyperfine line profiles. The aim is to show the computational efficiency of the program and to use it to examine the general accuracy of approximating spectra with simple models. We describe the implementation of the program. To characterise its performance, we examined spectra with isolated Gaussian components or a hyperfine structure, also using synthetic observations from numerical simulations of interstellar clouds. We examined the search for the globally optimal fit and the accuracy to which single-velocity-component and multi-component fits recover true values for parameters such as line areas, velocity dispersion, and optical depth. The program is shown to be fast, with fits of single Gaussian components reaching on graphics processing units speeds approaching one million spectra per second. This also makes it feasible to use Monte Carlo simulations or Markov chain Monte Carlo calculations for the error estimation. However, in the case of hyperfine structure lines, degeneracies affect the parameter estimation and can complicate the derivation of the error estimates. The use of many random initial values makes the fits more robust, both for locating the global $\chi^2$ minimum and for the selection of the optimal number of velocity components.

To increase the number of sources with Very Long Baseline Interferometry (VLBI) astrometry available for comparison with the Gaia results, we have observed 31 young stars with recently reported radio emission. These stars are all in the Gaia DR3 catalog and were suggested, on the basis of conventional interferometry observations, to be non-thermal radio emitters and, therefore, good candidates for VLBI detections. The observations were carried out with the Very Long Baseline Array (VLBA) at two epochs separated by a few days and yielded 10 detections (a $\sim$30\% detection rate). Using the astrometric Gaia results, we have extrapolated the target positions to the epochs of our radio observations and compared them with the position of the radio sources. For seven objects, the optical and radio positions are coincident within five times their combined position errors. Three targets, however, have position discrepancies above eight times the position errors, indicating different emitting sources at optical and radio wavelengths. In one case, the VLBA emission is very likely associated with a known companion of the primary target. In the other two cases, we associate the VLBA emission with previously unknown companions, but further observations will be needed to confirm this.

A large number of mergers of binary black holes (BHs) have been discovered by gravitational wave observations since the first detection of gravitational waves 2015. Binary BH mergers are the loudest events in the universe, however their origin(s) have been under debate. There have been many suggestions for merging binary BHs. Isolated binary stars are one of the most promising origins. We have investigated the evolution of isolated binary stars ranging from zero metallicity (Population III stars or Pop III stars) to the solar metallicity by means of so-called rapid binary population synthesis simulation. We have found that binary BHs formed from isolated binary stars reproduce the redshift evolution of the merger rate density and the distribution of primary BH masses and mass ratios inferred by Gravitational-Wave Transient Catalog 3 (GWTC-3). Pop III stars have a crucial role in forming merging binary BHs in so-called the pair instability mass gap. Note that we choose the conventional prescription of pair instability mass loss, based on the standard $^{12}$C($\alpha$,$\gamma$)$^{16}$O reaction rate. Finally, we have shown the redshift evolution of the rate density of pair instability supernovae, and have predicted that a few pair instability supernovae would be discovered in the next few years. The discoveries would validate our results of merging binary BHs.

We aim to determine the $^{14}$N/$^{15}$N and $^{12}$C/$^{13}$C ratios for HCN in six starless and prestellar cores and compare the results between the direct method using radiative transfer modeling and the indirect double isotope method assuming a fixed $^{12}$C/$^{13}$C ratio. We present IRAM 30m observations of the HCN 1-0, HCN 3-2, HC15N 1-0 and H13CN 1-0 transitions toward six embedded cores. The ${}^{14}$N/${}^{15}$N ratio was derived using both the indirect double isotope method and directly through non-local thermodynamic equilibrium (NLTE) 1D radiative transfer modeling of the HCN emission. The latter also provides the ${}^{12}$C/${}^{13}$C ratio, which we compared to the local interstellar value. The derived ${}^{14}$N/${}^{15}$N ratios using the indirect method are generally in the range of 300-550. This result could suggest an evolutionary trend in the nitrogen fractionation of HCN between starless cores and later stages of the star formation process. However, the direct method reveals lower fractionation ratios of around $\sim$250, mainly resulting from a lower ${}^{12}$C/${}^{13}$C ratio in the range $\sim$20-40, as compared to the local interstellar medium value of 68. This study reveals a significant difference between the nitrogen fractionation ratio in HCN derived using direct and indirect methods. This can influence the interpretation of the chemical evolution and reveal the pitfalls of the indirect double isotope method for fractionation studies. However, the direct method is challenging, as it requires well-constrained source models to produce accurate results. No trend in the nitrogen fractionation of HCN between earlier and later stages of the star formation process is evident when the results of the direct method are considered.

The Ion Composition Analyzer (ICA) on the Rosetta spacecraft observed both the solar wind and the cometary ionosphere around comet 67P/Churyumov-Gerasimenko for nearly two years. However, observations of low energy cometary ions were affected by a highly negative spacecraft potential, and the ICA ion density estimates were often much lower than plasma densities found by other instruments. Since the low energy cometary ions are often the highest density population in the plasma environment, it is nonetheless desirable to understand their properties. To do so, we select ICA data with densities comparable to those of Rosetta's Langmuir Probe (LAP)/Mutual Impedance Probe throughout the mission. We then correct the cometary ion energy distribution of each energy-angle scan for spacecraft potential and fit a drifting Maxwell-Boltzmann distribution, which gives an estimate of the drift energy and temperature for 3521 scans. The resulting drift energy is generally between 11--18 eV and the temperature between 0.5--1 eV. The drift energy shows good agreement with published ion flow speeds from LAP during the same time period and is much higher than the cometary neutral speed. We see additional higher energy cometary ions in the spectra closest to perihelion, which can either be a second Maxwellian or a kappa distribution. The energy and temperature are negatively correlated with heliocentric distance, but the slope of the change is small. It cannot be quantitatively determined whether this trend is primarily due to heliocentric distance or spacecraft distance to the comet, which increased with decreasing heliocentric distance.

We explore properties and behavior of slow-decaying unipolar sunspot groups in the framework of the turbulent erosion model suggested by Petrovay and Moreno-Insertis (1997). The basic concept of the model is the suppression of a turbulent diffusivity inside a magnetic flux tube by strong magnetic fields. As a result, the outer turbulent plasma detaches magnetic features primarily from the external border of a magnetic flux tube. The radius of the tube exhibits inward progression at a constant rate. The model predicts older sunspots to decay slower and it seems to be very promising to explain the slow decay of long-living unipolar sunspot groups. By analyzing the magnetic structure associated with a sunspot, we did reveal a gradual decrease of the magnetic structure radius at a constant rate implying the validity of the model. However, in some cases the derived velocity of the radius decrease was too low: our calculations provided implausibly high estimations for the lifetime and maximal area of such sunspots. We discuss possible additional mechanisms affecting the decay rate of such peculiar sunspots.

In the classical grouping of large magnitude episodic variability of young accreting stars, FUORs outshine their stars by a factor of $\sim$ 100, and can last for up to centuries; EXORs are dimmer, and last months to a year. A disc Hydrogen ionisation Thermal Instability (TI) scenario was previously proposed for FUORs but required unrealistically low disc viscosity. In the last decade, many intermediate type objects, e.g., FUOR-like in luminosity and spectra but EXOR-like in duration were found. Here we show that the intermediate type bursters Gaia20eae, PTF14jg, Gaia19bey and Gaia21bty may be naturally explained by the TI scenario with realistic viscosity values. We argue that TI predicts a dearth (desert) of bursts with peak accretion rates between $\dot M \sim 10^{-6} M_\odot$/yr and $\dot M \sim 10^{-5} M_\odot$/yr, and that this desert is seen in the sample of all the bursters with previously determined $\dot M$ burst. Most classic EXORs (FUORs) appear to be on the cold (hot) branch of the S-curve during the peak light of their eruptions; thus TI may play a role in this class differentiation. At the same time, TI is unable to explain how classic FUORs can last for up to centuries, and over-predicts the occurrence rate of short FUORs by at least an order of magnitude. We conclude that TI is a required ingredient of episodic accretion operating at R < 0.1 au, but additional physics must play a role at larger scales. Knowledge of TI inner workings from related disciplines may enable its use as a tool to constrain the nature of this additional physics.

We report on the detailed characterization of the HD 77946 planetary system. HD 77946 is an F5 ($M_*$ = 1.17 M$_{\odot}$, $R_*$ = 1.31 R$_{\odot}$) star, which hosts a transiting planet recently discovered by NASA's Transiting Exoplanet Survey Satellite (TESS), classified as TOI-1778 b. Using TESS photometry, high-resolution spectroscopic data from HARPS-N, and photometry from CHEOPS, we measure the radius and mass from the transit and RV observations, and find that the planet, HD 77946 b, orbits with period $P_{\rm b}$ = $6.527282_{-0.000020}^{+0.000015}$ d, has a mass of $M_{\rm b} = 8.38\pm{1.32}$M$_\oplus$, and a radius of $R_{\rm b} = 2.705_{-0.081}^{+0.086}$R$_\oplus$. From the combination of mass and radius measurements, and the stellar chemical composition, the planet properties suggest that HD 77946 b is a sub-Neptune with a $\sim$1\% H/He atmosphere. However, a degeneracy still exists between water-world and silicate/iron-hydrogen models, and even though interior structure modelling of this planet favours a sub-Neptune with a H/He layer that makes up a significant fraction of its radius, a water-world composition cannot be ruled out, as with $T_{\rm eq} = 1248^{+40}_{-38}~$K, water may be in a supercritical state. The characterisation of HD 77946 b, adding to the small sample of well-characterised sub-Neptunes, is an important step forwards on our journey to understanding planetary formation and evolution pathways. Furthermore, HD 77946 b has one of the highest transmission spectroscopic metrics for small planets orbiting hot stars, thus transmission spectroscopy of this key planet could prove vital for constraining the compositional confusion that currently surrounds small exoplanets.

Our aim in this paper is to refine the orbital and physical parameters of the HATS-2 planetary system and study transit timing variations and atmospheric composition thanks to transit observations that span more than ten years and that were collected using different instruments and pass-band filters. We also investigate the orbital alignment of the system by studying the anomalies in the transit light curves induced by starspots on the photosphere of the parent star. We analysed new transit events from both ground-based telescopes and NASA's TESS mission. Anomalies were detected in most of the light curves and modelled as starspots occulted by the planet during transit events. We fitted the clean and symmetric light curves with the JKTEBOP code and those affected by anomalies with the PRISM+GEMC codes to simultaneously model the photometric parameters of the transits and the position, size, and contrast of each starspot. We found consistency between the values we found for the physical and orbital parameters and those from the discovery paper and ATLAS9 stellar atmospherical models. We identified different sets of consecutive starspot-crossing events that temporally occurred in less than five days. Under the hypothesis that we are dealing with the same starspots, occulted twice by the planet during two consecutive transits, we estimated the rotational period of the parent star and, in turn the projected and the true orbital obliquity of the planet. We find that the system is well aligned. We identified the possible presence of transit timing variations in the system, which can be caused by tidal orbital decay, and we derived a low-resolution transmission spectrum.

We have detected solar-like oscillations in the mid K-dwarf $\varepsilon$ Indi A, making it the coolest dwarf to have measured oscillations. The star is noteworthy for harboring a pair of brown dwarf companions and a Jupiter-type planet. We observed $\varepsilon$ Indi A during two radial velocity campaigns, using the high-resolution spectrographs HARPS (2011) and UVES (2021). Weighting the time series, we computed the power spectra and established the detection of solar-like oscillations with a power excess located at $5265 \pm 110 \ \mu$Hz -- the highest frequency solar-like oscillations so far measured in any star. The measurement of the center of the power excess allows us to compute a stellar mass of $0.782 \pm 0.023 \ M_\odot$ based on scaling relations and a known radius from interferometry. We also determine the amplitude of the peak power and note that there is a slight difference between the two observing campaigns, indicating a varying activity level. Overall, this work confirms that low-amplitude solar-like oscillations can be detected in mid-K type stars in radial velocity measurements obtained with high-precision spectrographs.

The variation mechanism of blazars is a long-standing unresolved problem. In this work, we present a scenario to explain diverse variation phenomena for ON 231, where the jet emissions are composed of the flaring and the less variable components (most probably from the post-flaring blobs), and the variation is dominated by shock-in-jet instead of the Doppler effect. We perform correlation analysis for the multiwavelength light curves and find no significant correlations. For optical band, ON 231 exhibits a harder when brighter (HWB) trend, and the trend seems to shift at different periods. Correspondingly, the correlation between polarization degree and flux exhibits a V-shaped behavior, and a similar translation relation during different periods is also found. These phenomena could be understood via the superposition of the flaring component and slowly varying background component. We also find that the slopes of HWB trend become smaller at higher flux levels, which indicates the energy-dependent acceleration processes of the radiative particles. For X-ray, we discover a trend transition from HWB to softer when brighter (SWB) to HWB. We consider that the X-ray emission is composed of both the synchrotron tail and the Synchrotron Self-Compton components, which could be described by two log-parabolic functions. By varying the peak frequency, we reproduce the observed trend transition in a quantitative manner. For $\gamma$-ray, we find the SWB trend, which could be explained naturally if a very-high-energy $\gamma$-ray background component exists. Our study elucidates the variation mechanism of intermediate synchrotron-peaked BL Lac objects.

We conducted a photometric and kinematic analysis of the young open cluster NGC 2345 using CCD \emph{UBV} data from 2-m Himalayan Chandra Telescope (HCT), \emph{Gaia} Data Release 3 (DR3), 2MASS, and the APASS datasets. We found 1732 most probable cluster members with membership probability higher than 70$\%$. The fundamental and structural parameters of the cluster are determined based on the cluster members. The mean proper motion of the cluster is estimated to be $\mu_{\alpha}cos\delta$ = ${-1.34}\pm0.20$ and $\mu_{\delta}$= $1.35\pm 0.21$ mas $yr^{-1}$. Based on the radial density profile, the estimated radius is $\sim$ 12.8 arcmin (10.37 pc). Using color-color and color-magnitude diagrams, we estimate the reddening, age, and distance to be $0.63\pm0.04$ mag, 63 $\pm$ 8 Myr, and 2.78 $\pm$ 0.78 kpc, respectively. The mass function slope for main-sequence stars is determined as $1.2\pm 0.1$. The mass function slope in the core, halo, and overall region indicates a possible hint of mass segregation. The cluster's dynamical relaxation time is 177.6 Myr, meaning ongoing mass segregation, with complete equilibrium expected in 100-110 Myr. Apex coordinates are determined as $-40^{\circ}.89 \pm 0.12, -44^{\circ}.99 \pm 0.15$. The cluster's orbit in the Galaxy suggests early dissociation in field stars due to its close proximity to the Galactic disk.

The process of forming a circumbinary planet is thought to be intimately related to the structure of the nascent circumbinary disc. It has been shown that the structure of a circumbinary disc depends strongly on 3-dimensional effects and on the detailed modelling of the thermodynamics. Here, we employ 3-dimensional hydrodynamical simulations, combined with a proper treatment of the thermal physics using the RADMC-3D radiation transport code, to examine the location of the snow line in circumbinary discs. The models have application to the circumbinary planets that have been discovered in recent years by the Kepler and TESS transit surveys. We find that the snow line is located in a narrow region of the circumbinary disc, close to the inner cavity that is carved out by the central binary, at typical orbital distances of $\sim 1.5-2$ AU for the system parameters considered. In this region, previous work has shown that both grain growth and pebble accretion are likely to be inefficient because of the presence of hydrodynamical turbulence. Hence, in situ planet formation interior to the snow line is unlikely to occur and circumbinary planets should preferentially be icy, not rocky.

Cross sections and rate coefficients for the Dissociative Recombination (DR) of the NS+ ion induced by collisions with low-energy electrons are reported for temperatures between 10 and 1000 K, relevant to a large range of interstellar cloud temperatures. Uncertainties are discussed for these rates. Comparisons are made with DR rates for the isovalent NO+ molecular ion which are found to be much faster. The present findings lead to a moderate dissociative reaction rate coefficient, smaller by a factor of 2 than the current estimates reported in the different kinetic databases for a temperature of 10 K. We consider that our rate coefficients obtained through multichannel quantum defect theory for NS+ are likely to be better than those displayed in the different kinetic databases.

Stellar activity and planetary effects induce radial velocity (RV) offsets and cause temporal distortions in the shape of the stellar line profile. Hence, accurately probing the stellar line profile offers a wealth of information on both the star itself and any orbiting planets. Typically, Cross-Correlation Functions (CCFs) are used as a proxy for the stellar line profile. The shape of CCFs, however, can be distorted by line blending and aliasing limiting the stellar and planetary physics that can be probed from them. Least-squares deconvolution (LSD) offers an alternative that directly fits the mean line profile of the spectrum to produce a high-precision profile. In this paper, we introduce our novel method ACID (Accurate Continuum fItting and Deconvolution) that builds on LSD techniques by simultaneously fitting the spectral continuum and line profile as well as performing LSD in effective optical depth. Tests on model data revealed ACID can accurately identify and correct the spectral continuum to retrieve an injected line profile. ACID was also applied to archival HARPS data obtained during the transit of HD189733b. The application of the Reloaded Rossiter-McLaughlin technique to both ACID profiles and HARPS CCFs shows ACID residual profiles improved the out-of-line RMS by over 5% compared to CCFs. Furthermore, ACID profiles are shown to exhibit a Voigt profile shape that better describes the expected profile shape of the stellar line profile. This improved representation shows that ACID better preserves the stellar and planetary physics encoded in the stellar line profile shape for slow rotating stars.

We report the identification of 89 new systems containing ultracool dwarf companions to main sequence stars and white dwarfs, using the citizen science project Backyard Worlds: Planet 9 and cross-reference between Gaia and CatWISE2020. Thirty-two of these companions and thirty-three host stars were followed up with spectroscopic observations, with companion spectral types ranging from M7-T9 and host spectral types ranging from G2-M9. These systems exhibit diverse characteristics, from young to old ages, blue to very red spectral morphologies, potential membership to known young moving groups, and evidence of spectral binarity in 9 companions. Twenty of the host stars in our sample show evidence for higher order multiplicity, with an additional 11 host stars being resolved binaries themselves. We compare this sample's characteristics with those of the known stellar binary and exoplanet populations, and find our sample begins to fill in the gap between directly imaged exoplanets and stellary binaries on mass ratio-binding energy plots. With this study, we increase the population of ultracool dwarf companions to FGK stars by $\sim$42\%, and more than triple the known population of ultracool dwarf companions with separations larger than 1,000 au, providing excellent targets for future atmospheric retrievals.

We have developed a method to determine the most reliable distances for a large group of planetary nebulae. For this purpose, we analyze the distances obtained from \textit{Gaia} parallaxes and three determinations of statistical distances. The most reliable distance is derived for 2211 objects, and uncertainties for these distances are calculated in a homogeneous way. Using our most reliable distances, we compare the distributions of Galactic heights of hydrogen-poor and hydrogen-rich central stars of planetary nebulae. We find that [WR] central stars are closer to the Galactic plane than hydrogen-rich central stars and than other hydrogen-poor central stars. The latter have a similar distribution to hydrogen-rich central stars, which is significantly different from the one of [WR] central stars. This result disagrees with the proposed evolutionary sequence for hydrogen-poor central stars.

We calculate the tensor bispectrum mediated by an excited scalar field during inflation and find that the bispectrum peaks in the squeezed configuration, which is different from that of gravitational waves induced by enhanced curvature perturbations re-entering the horizon in the radiation-dominated era. Measuring the bispectrum provides a promising way to distinguish the stochastic gravitational-wave background generated during inflation from that generated after inflation.

CRL 618 is a post-AGB star that has started to ionize its ejecta. Its central HII region has been observed over the last 40 years and has steadily increased in flux density at radio wavelengths. In this paper, we present data that we obtained with the Very Large Array in its highest frequency band (43 GHz) in 2011 and compare these with archival data in the same frequency band from 1998. By applying the so-called expansion-parallax method, we are able to estimate an expansion rate of 4.0$\pm$0.4 mas yr$^{-1}$ along the major axis of the nebula and derive a distance of 1.1$\pm$0.2 kpc. Within errors, this distance estimation is in good agreement with the value of ~900 pc derived from the expansion of the optical lobes.

We demonstrate that pairwise peculiar velocity correlations for galaxy clusters can be directly reconstructed from the kinematic Sunyaev-Zel'dovich (kSZ) signature imprinted in the CMB using a machine learning model with a gradient boosting algorithm trained on high-fidelity kSZ simulations. The machine learning model is trained using six to eight cluster features that are directly related to observables from CMB and large-scale structure surveys. We validate the capabilities of the approach in light of the presence of primary CMB, detector noise, and potential uncertainties in the cluster mass estimate and cluster center location. The pairwise velocity statistics extracted using the techniques developed here have the potential to elicit valuable cosmological constraints on dark energy, modified gravity models, and massive neutrinos with kSZ measurements from upcoming CMB surveys, including the Simons Observatory, CMB-S4 and CCAT, and the DESI and SDSS galaxy surveys.

We examine one-loop corrections from small-scale curvature perturbations to the superhorizon-limit ones in single-field inflation models, which have recently caused controversy. We consider the case where the Universe experiences transitions of slow-roll (SR) $\to$ intermediate period $\to$ SR. The intermediate period can be an ultra-slow-roll period or a resonant amplification period, either of which enhances small-scale curvature perturbations. We assume that the superhorizon curvature perturbations are conserved at least during each of the SR periods. Within this framework, we show that the superhorizon curvature perturbations during the first and the second SR periods coincide at one-loop level in the slow-roll limit.

Black-hole X-ray binaries exhibit different spectral and timing properties in different accretion states. The X-ray outburst of a recently discovered and extraordinarily bright source, Swift$~$J1727.8$-$1613, has enabled the first investigation of how the X-ray polarization properties of a source evolve with spectral state. The 2$-$8 keV polarization degree was previously measured by the Imaging X-ray Polarimetry Explorer (IXPE) to be $\approx$ 4% in the hard and hard intermediate states. Here we present new IXPE results taken in the soft state, with the X-ray flux dominated by the thermal accretion-disk emission. We find that the polarization degree has dropped dramatically to $\lesssim$ 1%. This result indicates that the measured X-ray polarization is largely sensitive to the accretion state and the polarization fraction is significantly higher in the hard state when the X-ray emission is dominated by up-scattered radiation in the X-ray corona. The combined polarization measurements in the soft and hard states disfavor a very high or low inclination of the system.

Molecular emission is used to investigate both the physical and chemical properties of protoplanetary disks. Therefore, to accurately derive disk properties, we need a thorough understanding of the behavior of the molecular probes we rely on. Here we investigate how the molecular line emission of N$_2$H$^+$, HCO$^+$, HCN, and C$^{18}$O compare to other measured quantities in a set of 20 protoplanetary disks. Overall, we find positive correlations between multiple line fluxes and the disk dust mass and radius. We also generally find strong positive correlations between the line fluxes of different molecular species. However, some disks do show noticeable differences in the relative fluxes of N$_2$H$^+$, HCO$^+$, HCN, and C$^{18}$O. These differences occur even within a single star-forming region. This results in a potentially large range of different disk masses and chemical compositions for systems of similar age and birth environment. While we make preliminary comparisons of molecular fluxes across different star-forming regions, more complete and uniform samples are needed in the future to search for trends with birth environment or age.

We propose the entropy estimator $H_Z$, calculated from global dynamical parameters, in an attempt to capture the degree of evolution of galaxy systems. We assume that the observed (spatial and velocity) distributions of member galaxies in these systems evolve over time towards states of higher dynamical relaxation (higher entropy), becoming more random and homogeneous in virial equilibrium. Thus, the $H_Z$-entropy should correspond to the gravitacional assembly state of the systems. This was tested in a sample of 70 well sampled clusters in the Local Universe whose gravitational assembly state, classified from optical and X-ray analysis of substructures, shows clear statistical correlation with $H_Z$. This estimator was also tested on a sample of clusters (halos) from the IllustrisTNG simulations, obtaining results in agreement with the observational ones.

Current imaging observations of protoplanetary disks using ALMA primarily focus on the sub-millimeter wavelength, leaving a gap in effective observational approaches for centimeter-sized dust, which is crucial to the issue of planet formation. The forthcoming SKA and ngVLA may rectify this deficiency. In this paper, we employ multi-fluid hydrodynamic numerical simulations and radiative transfer calculations to investigate the potential of SKA1-Mid, ngVLA, and SKA2 for imaging protoplanetary disks at sub-cm/cm wavelengths. We create mock images with ALMA/SKA/ngVLA at multi-wavelengths based on the hydrodynamical simulation output, and test different sensitivity and spatial resolutions. We discover that both SKA and ngVLA will serve as excellent supplements to the existing observational range of ALMA, and their high resolution enables them to image substructures in the disk's inner region ($\sim$ 5 au from the stellar). Our results indicate that SKA and ngVLA can be utilized for more extended monitoring programs in the centimeter waveband. While in the sub-centimeter range, ngVLA possesses the capability to produce high-fidelity images within shorter observation times ($\sim$ 1 hour on source time) than previous research, holding potential for future survey observations. We also discuss for the first time the potential of SKA2 for observing protoplanetary disks at a 0.7 cm wavelength.

We study gravitational and test-field perturbations for the two possible families of spherically symmetric black-hole mimickers that smoothly interpolate between regular black holes and horizonless compact objects accordingly to the value of a regularization parameter. One family can be described by the Bardeen-like metrics, and the other by the Simpson-Visser metric. We compute the spectrum of quasi-normal modes (QNMs) of these spacetimes enlightening a common misunderstanding regarding this computation present in the recent literature. In both families, we observe long-living modes for values of the regularization parameter corresponding to ultracompact, horizonless configurations. Such modes appear to be associated with the presence of a stable photon sphere and are indicative of potential non-linear instabilities. In general, the QNM spectra of both families display deviations from the standard spectrum of GR singular BHs. In order to address the future detectability of such deviations in the gravitational-wave ringdown signal, we perform a preliminary study, finding that third generation ground-based detectors might be sensible to macroscopic values of the regularization parameter.

We investigate the hypothesis that sexaquarks, hypothetical stable six-quark states, could be a significant component of the dark matter. We expand on previous studies of sexaquark cosmology, accounting for the possibility that some relevant interaction cross sections might be strongly suppressed below expectations based on dimensional analysis. We update direct-detection constraints on stable sexaquarks comprising a subdominant fraction of the dark matter, as well as limits on the annihilation of an antisexaquark component from Super-Kamiokande. We argue that the scenario where sexaquarks comprise a $O(1)$ fraction of the dark matter would require either a suppression of $O(10^{-19})$ in sexaquark interactions with baryons, combined with a very high yield of net sexaquark number from the quark-hadron transition, or else a very strong suppression of the cross section for antisexaquark annihilation on nucleons (24+ orders of magnitude below the QCD scale). Independently, we find that a sexaquark component comprising more than $O(10^{-3})$ of the dark matter can be excluded from direct-detection bounds, unless its scattering cross section is severely suppressed compared to the expected scale of strong and even electromagnetic interactions.

Gravitational lensing is the effect on a lightlike trajectory by the presence of matter, affecting its trajectory in spacetime. Gravitational lensing of gravitational waves can occur in geometric optics limit (when GW wavelength is much smaller than the Schwarzschild radius of the lens i.e. $\lambda_{GW} \ll$ R$^{\rm sc}_{\rm lens}$, multiple images with different magnifications are formed) known as strong-lensing or in wave optics limit (when the wavelength of GW is larger than the Schwarzschild radius i.e. R$^{\rm sc}_{\rm lens}$ $\lesssim \lambda_{GW} $, interfering signals produce beating pattern in the waveform envelope) known as micro-lensing. Currently, large sky-localization errors of GW sources and strong noise-PSD have barred us from evidencing lensed GWs. Considering this aspect, we have developed $\texttt{GLANCE}$, a novel technique to detect lensed GWs. We demonstrate that cross-correlation between the data pieces containing lensed signals shows a very specific trend. The strength of the cross-correlation signal can quantify the significance of the event(s) being lensed. Since lensing impacts the inference of the source parameters, primarily the luminosity distance for the strong lensing case, a joint parameter estimation of the source and lens-induced parameters is incorporated in $\texttt{GLANCE}$ using a Bayesian framework. We applied our method to simulated strongly lensed data and we have shown that $\texttt{GLANCE}$ not only can detect lensed GW signals but also can correctly infer the injected source and lens parameters even when one of the signals is below the match-filtered threshold SNR. This demonstrates the capability of $\texttt{GLANCE}$ for a robust detection of lensed GW signal from noisy data.

Different in situ satellite observations within 0.3 to 1 AU from the Sun reveal deviations in the thermodynamics of solar wind expansion. Specifically, these deviations challenge the applicability of the double adiabatic or CGL theory, indicating potential influences such as perpendicular heating and/or parallel cooling of ions. The study aims to investigate the plasma expansion phenomena using the Expanding Box Model (EBM) coupled with an ideal MHD description of the plasma. The primary objective is to understand the observed deviations from the CGL predictions, and how the expansion can affect the conservation of the adiabatic invariants, particularly focusing on the impact of transverse expansion on the CGL equations. To address the plasma expansion, we employed the Expanding Box Model (EBM) coupled with the ideal-MHD formalism used for CGL theory. This model provides a unique system of reference co-moving with the solar wind, allowing for the incorporation of transverse expansion into the double adiabatic equations. Solving the equations for different magnetic field profiles, we compute the evolution of anisotropy and plasma beta, which deviates from CGL predictions and empirical observations. This deviation is attributed to the plasma cooling effect induced by the Expanding Box Model (EBM). Results suggest that heating mechanisms play a crucial role in counteracting plasma cooling during expansion.

The Hawking process results in a monotonic decrease of the black hole mass, but a biased random walk of the black hole angular momentum. We demonstrate that this stochastic process leads to a significant fraction of primordial black holes becoming extremal Kerr black holes (EKBHs) of one to a few Planck masses regardless of their initial mass. For these EKBHs, the probability of ever absorbing a photon or other particle from the cosmic environment is small, even in the cores of galaxies. Assuming that EKBHs are stable, they behave as cold dark matter, and can comprise all of the dark matter if they are formed with the correct initial abundance.

We present the first time the profile of atmospheric optical turbulence has been measured using the transmitted beam from a satellite laser communication terminal. A Ring Image Next Generation Scintillation Sensor (RINGSS) instrument for turbulence profiling, as described in Tokovinin (MNRAS, 502.1, 2021), was deployed at the NASA/Jet Propulsion Laboratory's Table Mountain Facility (TMF) in California. The optical turbulence profile was measured with the downlink optical beam from the Laser Communication Relay Demonstration (LCRD) Geostationary satellite. LCRD conducts links with the Optical Communication Telescope Laboratory ground station and the RINGSS instrument was co-located at TMF to conduct measurements. Turbulence profiles were measured at day and night and atmospheric coherence lengths were compared with other turbulence monitors such as a solar scintillometer and Polaris monitor. RINGSS sensitivity to boundary layer turbulence, a feature not provided by many profilers, is also shown to agree well with a boundary layer scintillometer at TMF. Diurnal evolution of optical turbulence and measured profiles are presented. The robust correlation of RINGSS with other turbulence monitors demonstrates the concept of free-space optical communications turbulence profiling, which could be adopted as a way to support optical ground stations in a future Geostationary feeder link network. These results also provide further evidence that RINGSS, a relatively new instrument concept, is effective even in strong daytime turbulence and with reasonable ground layer sensitivity.

With the ongoing growth in radio communications, there is an increased contamination of radio astronomical source data, which hinders the study of celestial radio sources. In many cases, fast mitigation of strong radio frequency interference (RFI) is valuable for studying short lived radio transients so that the astronomers can perform detailed observations of celestial radio sources. The standard method to manually excise contaminated blocks in time and frequency makes the removed data useless for radio astronomy analyses. This motivates the need for better radio frequency interference (RFI) mitigation techniques for array of size M antennas. Although many solutions for mitigating strong RFI improves the quality of the final celestial source signal, many standard approaches require all the eigenvalues of the spatial covariance matrix ($\textbf{R} \in \mathbb{C}^{M \times M}$) of the received signal, which has $O(M^3)$ computation complexity for removing RFI of size $d$ where $\textit{d} \ll M$. In this work, we investigate two approaches for RFI mitigation, 1) the computationally efficient Lanczos method based on the Quadratic Mean to Arithmetic Mean (QMAM) approach using information from previously-collected data under similar radio-sky-conditions, and 2) an approach using a celestial source as a reference for RFI mitigation. QMAM uses the Lanczos method for finding the Rayleigh-Ritz values of the covariance matrix $\textbf{R}$, thus, reducing the computational complexity of the overall approach to $O(\textit{d}M^2)$. Our numerical results, using data from the radio observatory Long Wavelength Array (LWA-1), demonstrate the effectiveness of both proposed approaches to remove strong RFI, with the QMAM-based approach still being computationally efficient.

We propose a self-supervised learning model to denoise gravitational wave (GW) signals in the time series strain data without relying on waveform information. Denoising GW data is a crucial intermediate process for machine-learning-based data analysis techniques, as it can simplify the model for downstream tasks such as detections and parameter estimations. We use the blind-spot neural network and train it with whitened strain data with GW signals injected as both input data and target. Under the assumption of a Gaussian noise model, our model successfully denoises 38% of GW signals from binary black hole mergers in H1 data and 49% of signals in L1 data detected in the O1, O2, and O3 observation runs with an overlap greater than 0.5. We also test the model's potential to extract glitch features and loud inspiral compact binary coalescence signals a few seconds before the merger.

We propose a variant of Hamiltonian Monte Carlo (HMC), called the Repelling-Attracting Hamiltonian Monte Carlo (RAHMC), for sampling from multimodal distributions. The key idea that underpins RAHMC is a departure from the conservative dynamics of Hamiltonian systems, which form the basis of traditional HMC, and turning instead to the dissipative dynamics of conformal Hamiltonian systems. In particular, RAHMC involves two stages: a mode-repelling stage to encourage the sampler to move away from regions of high probability density; and, a mode-attracting stage, which facilitates the sampler to find and settle near alternative modes. We achieve this by introducing just one additional tuning parameter -- the coefficient of friction. The proposed method adapts to the geometry of the target distribution, e.g., modes and density ridges, and can generate proposals that cross low-probability barriers with little to no computational overhead in comparison to traditional HMC. Notably, RAHMC requires no additional information about the target distribution or memory of previously visited modes. We establish the theoretical basis for RAHMC, and we discuss repelling-attracting extensions to several variants of HMC in literature. Finally, we provide a tuning-free implementation via dual-averaging, and we demonstrate its effectiveness in sampling from, both, multimodal and unimodal distributions in high dimensions.

During particle collisions in the vicinity of the horizon of black holes, it is possible to achieve energies and temperatures corresponding to phase transitions in particle physics. It is shown that the sizes of the regions of the new phase are of the order of the Compton length for the corresponding mass scale. The lifetime is also on the order of the Compton time. It is shown that the inverse influence of the energy density in the electro-weak phase transition in collisions on the space-time metric can be neglected.