Papers for Thursday, Sep 23 2021

WR 140 is a long-period, highly eccentric Wolf-Rayet star binary system with exceptionally well-determined orbital and stellar parameters. Bright, variable X-ray emission is generated in shocks produced by the collision of the winds of the WC7pd+O5.5fc component stars. We discuss the variations in the context of the colliding-wind model using broad-band spectrometry from the RXTE, SWIFT, and NICER observatories obtained over 20 years and nearly 1000 observations through 3 consecutive 7.94-year orbits including 3 periastron passages. The X-ray luminosity varies as expected with the inverse of the stellar separation over most of the orbit: departures near periastron are produced when cooling shifts to excess optical emission in CIII $\lambda5696$ in particular. We use X-ray absorption to estimate mass-loss rates for both stars and to constrain the system morphology. The absorption maximum coincides closely with inferior conjunction of the WC star and provides evidence of the ion-reflection mechanism that underlies the formation of collisionless shocks governed by magnetic fields probably generated by the Weibel instability. Comparisons with K-band emission and HeI $\lambda$10830 absorption show that both are correlated after periastron with the asymmetric X-ray absorption. Dust appears within a few days of periastron suggesting formation within shocked gas near the stagnation point. X-ray flares seen in $\eta$ Carinae have not occurred in WR 140, suggesting the absence of large-scale wind inhomogeneities. Relatively constant soft emission revealed during the X-ray minimum is probably not from recombining plasma entrained in outflowing shocked gas.

COMPAS (Compact Object Mergers: Population Astrophysics and Statistics, https://compas.science) is a public rapid binary population synthesis code. COMPAS generates populations of isolated stellar binaries under a set of parametrised assumptions in order to allow comparisons against observational data sets, such as those coming from gravitational-wave observations of merging compact remnants. It includes a number of tools for population processing in addition to the core binary evolution components. COMPAS is publicly available via the github repository https://github.com/TeamCOMPAS/COMPAS/, and is designed to allow for flexible modifications as evolutionary models improve. This paper describes the methodology and implementation of COMPAS. It is a living document which will be updated as new features are added to COMPAS; the current document describes COMPAS v02.21.00.

Galaxy mergers are known to host abundant young massive cluster (YMC) populations, whose formation mechanism is still not well-understood. Here, we present a high-resolution galaxy merger simulation with explicit star formation and stellar feedback prescriptions to investigate how mergers affect the properties of the interstellar medium and YMCs. Compared with a controlled simulation of an isolated galaxy, the mass fraction of dense and high-pressure gas is much higher in mergers. Consequently, the mass function of both molecular clouds and YMCs becomes shallower and extends to higher masses. Moreover, cluster formation efficiency is significantly enhanced and correlates positively with the star formation rate surface density and gas pressure. We track the orbits of YMCs and investigate the time evolution of tidal fields during the course of the merger. At an early stage of the merger, the tidal field strength correlates positively with YMC mass, $\lambda_{\rm tid}\propto M^{0.71}$, which systematically affects the shape of the mass function and age distribution of the YMCs. At later times, most YMCs closely follow the orbits of their host galaxies, gradually sinking into the center of the merger remnant due to dynamical friction, and are quickly dissolved via efficient tidal disruption. Interestingly, YMCs formed during the first passage, mostly in tidal tails and bridges, are distributed over a wide range of galactocentric radii, greatly increasing their survivability because of the much weaker tidal field in the outskirts of the merger system. These YMCs are promising candidates for globular clusters that survive to the present day.

We train neural networks to perform likelihood-free inference from $(25\,h^{-1}{\rm Mpc})^2$ 2D maps containing the total mass surface density from thousands of hydrodynamic simulations of the CAMELS project. We show that the networks can extract information beyond one-point functions and power spectra from all resolved scales ($\gtrsim 100\,h^{-1}{\rm kpc}$) while performing a robust marginalization over baryonic physics at the field level: the model can infer the value of $\Omega_{\rm m} (\pm 4\%)$ and $\sigma_8 (\pm 2.5\%)$ from simulations completely different to the ones used to train it.

Eccentric millisecond pulsars (eMSPs) with white dwarf companions exhibit orbital eccentricities orders of magnitude larger than predicted by turbulent convection in the white dwarfs' red giant progenitors. The orbital periods of eMSPs cluster around $P=20-30$ d, remarkably close to the red giant convective eddy turnover time $t_{\rm eddy}$. We propose that the anomalously large eccentricities are resonantly driven by convective flows somehow made coherent when the turnover time matches the tidally locked red giant's spin period, which is also the tidal forcing period. Numerical simulations of rotating red giants and magnetic field studies of stars show some evidence for especially ordered flow patterns when the convective Rossby number $P/t_{\rm eddy}$ is of order unity. We show that resonant convection boosts eccentricities by a factor of $(t_{\rm nuc}/P)^{1/2}\approx 3\times 10^3$ over the random-walk values that characterize conventional MSPs, in good agreement with observations ($t_{\rm nuc}$ is the giant's nuclear burning time-scale). We also show how variations in the eddy turnover time arising from red giant metallicity variations can reproduce the observed effective width of the resonance, $\Delta P/P\approx 0.4$.

Supernova explosion and the associated neutron star natal kicks are important events on a pathway of a binary to become a gravitational wave source, an X-ray binary or a millisecond radio pulsar. Weak natal kicks often lead to binary survival, while strong kicks frequently disrupt the binary. In this article, we aim to further constrain neutron star natal kicks in binaries. We explore binary population synthesis models by varying prescription for natal kick, remnant mass and mass accretion efficiency. We introduce a robust statistical technique to analyse combined observations of different nature. Using this technique, we further test different models using parallax and proper motion measurements for young isolated radio pulsars and similar measurements for Galactic Be X-ray binaries. Our best model for natal kicks is consistent with both measurements and contains a fraction of $w=0.2\pm 0.1$ weak natal kicks with $\sigma_1 = 45^{+25}_{-15}$ km/s, the remaining natal kicks are drawn from the high-velocity component, same as in previous works: $\sigma_2 = 336$ km/s. We found that currently used models for natal kicks of neutron stars produced by electron capture supernova (combination of maxwellian $\sigma=265$ km/s and $\sigma = 30$ km/s for electron capture) are inconsistent or marginally consistent with parallaxes and proper motions measured for isolated radio pulsars. We suggest a new model for natal kicks of ecSN, which satisfy both observations of isolated radio pulsars and Be X-ray binaries.

In this work, we investigate the reliability of spectral synthesis methods in the estimation of the mean stellar age and metallicity, addressing the question of which signal-to-noise ratios (S/N) are needed to determine these quantities. To address this problem we used simulated spectra containing stellar and nebular emission, reproducing the evolution of a galaxy for a constant and exponentially declining star formation law. The spectra have been degraded to different S/N and analysed with three different spectral synthesis codes: FADO, STARLIGHT, and STECKMAP assuming similar fitting set-ups and the same spectral bases. For S/N > 5 all tools considered show a large diversity in the results. FADO and STARLIGHT find median differences in light-weighted mean stellar ages of ~0.1 dex, while STECKMAP shows a higher value of ~0.2 dex. For S/N > 50 the median differences in FADO are ~0.03 dex (~7%), a factor 3 and 4 lower than the 0.08 dex (~20%) and 0.11 dex (~30%) obtained from STARLIGHT and STECKMAP, respectively. Our results indicate that phases of high specific star formation rate (sSFR) in galaxies require analysis tools that do not neglect the nebular continuum emission in the fitting process, since purely stellar models would have strong problems in the estimation of star formation history, even in presence of high S/N spectra. The median values of these differences are of the order of 7% (FADO), 20% (STARLIGHT), and 30% (STECKMAP) for light-weighted quantities, and 20% (FADO), 60% (STARLIGHT), and 20% (STECKMAP) for mass-weighted quantities. That implies a severe overestimation of the mass-to-light ratio and stellar mass, even in the presence of a mild contribution from the nebular continuum. Our work underlines the importance of a self-consistent treatment of nebular emission, which is the only route towards a reliable determination of the assembly of any high-sSFR galaxy.

Axion-like particles can in principle be produced in the dense environment of neutron star mergers and core-collapse supernovae, and converted in gamma-rays in the magnetic field intervening between the event and the Earth. While this process has been studied for supernovae, there is no estimate of the gamma-ray signal expected from neutron star mergers. In this work we explore this new, exotic signature of the merger, and find that for a large region of the ALP parameter space its magnitude is comparable with that of a signal of similar nature from a SN. We show detection forecasts for these events, finding that they could be observable with the e-ASTROGAM telescope, thus opening a new window into both the astrophysics of these cataclysmic events, and of new particles beyond the standard model.

The Compton Spectrometer and Imager (COSI) is a balloon-borne compact Compton telescope designed to survey the $\gamma$-ray sky from 0.2 to 5 MeV. COSI's wide field-of-view (FOV) and excellent energy resolution from high-purity germanium detectors make it uniquely capable of probing this under-explored energy regime. In particular, it can facilitate understanding of stellar nucleosynthesis through studies of diffuse emission from the radioisotope $\mathrm{^{26}Al}$ at 1.809 MeV. In 2016, COSI was launched from Wanaka, New Zealand on a NASA superpressure balloon and flew for 46 days. The flight was a technologic and scientific success, boasting live detection and polarization studies of GRB160530A, spectral analysis of the Crab Nebula and the 511-keV positron annihilation emission at the Galactic Center, and detection of Cygnus X-1. This article details the first maximum-likelihood search for the 1.809 MeV signature of Galactic $\mathrm{^{26}Al}$ in the 2016 data. The analysis reveals a promising excess around the expected energies of an $\mathrm{^{26}Al}$ signature with 3.7$\sigma$ significance and a measured flux of (17.0 $\pm$ 4.9) $\times$ 10$^{-4}$ ph cm$^{-2}$ s$^{-1}$. Further exploration is currently underway to solidify the measurement.

We extract void catalogs from the Sloan Digital Sky Survey Data Release 16 (SDSS DR16) survey and also from the Millennium simulation. We focus our comparison on distribution of galaxies brighter than $M_r < -18$ inside voids and study the mean separation of void galaxies, distance from the void center, and the radial density profile. We find that mean separation of void galaxies depends on void size, as bigger voids have lower mean separation in both samples. However, void galaxies in the observation sample seem to have generally larger mean-distance than simulated ones at any given void size. In addition, observed void galaxies tend to reside closer to the void center than those in the simulation. This discrepancy is also shown in the density profile of voids. Regardless of the void size, the central densities of real void profiles are higher than the ones in the predicted simulated catalog.

In a previous paper, we showed that the asymmetric ejecta produced by (zero impact parameter) head-on collisions of carbon-oxygen white dwarfs allow these progenitor models for Type Ia supernovae (SNe Ia) to cover the observed two-dimensional (2D) distribution of Si II line depths (Branch plot). In this paper, we study the polarization signature associated with the 2D asymmetric ejecta of the collision model and a double-detonation model using similar TARDIS radiative transfer simulations along different lines of sight with a spherical photosphere, combined with a new 3D Monte Carlo polarization code. We show that the polarization $Q$ can be parametrized as a product $Q=Q_{\max}Q_{\rm{x}}$ of a radial structure component $Q_{\max}$ which is insensitive to the model specifics and is shown to be universally around $Q_{\max}\sim 5\%$, and a cancellation component $Q_{\rm{x}}$ which depends on the asymmetry details. The continuum polarization is found to be low for both the collision and double-detonation models with $Q\sim 0.5\%$. However, the irregular Si distribution in the 2D head-on collision model results in Si II line polarization reaching $Q\sim 3\%$ ($Q_{\rm{x}} \lesssim 50\%$) in tension with observations (mostly $\lesssim 1.2\%$). In contrast, we show that the double-detonation model also covers the Branch plot, and yet results in low line polarization $Q\lesssim 0.7\%$ ($Q_{\rm{x}} \sim 10\%$) consistent with previous results and most SNe Ia. These results strengthen the case for asymmetric explosions as progenitors of SNe Ia, emphasizing an additional requirement for large polarization cancellations to account for the low observed line polarizations.

The Abundance Matching Box for the Epoch of Reionization (AMBER) is a semi-numerical code for modeling the cosmic dawn. The new algorithm is not based on the excursion set formalism, but takes the novel approach of calculating the reionization-redshift field $z_\mathrm{re}(\boldsymbol{x})$ assuming that hydrogen gas encountering higher radiation intensity are photoionized earlier. Redshift values are assigned while matching the abundance of ionized mass according to a given mass-weighted ionization fraction $\bar{x}_\mathrm{i}(z)$. The code has the unique advantage of allowing users to directly specify the reionization history through the redshift midpoint $z_\mathrm{mid}$, duration $\Delta_\mathrm{z}$, and asymmetry $A_\mathrm{z}$ input parameters. The reionization process is further controlled through the minimum halo mass $M_\mathrm{min}$ for galaxy formation and the radiation mean free path $l_\mathrm{mfp}$ for radiative transfer. We implement improved methods for constructing density, velocity, halo, and radiation fields, which are essential components for modeling reionization observables. We compare AMBER with two other semi-numerical methods and find that our code more accurately reproduces the results from radiation-hydrodynamic simulations. The parallelized code is over four orders of magnitude faster than radiative transfer simulations and will efficiently enable large-volume models, full-sky mock observations, and parameter-space studies. AMBER will be made publicly available to facilitate and transform studies of the EoR.

Over the past decades, rest-frame ultraviolet (UV) observations have provided large samples of UV luminous galaxies at redshift (z) greater than 6, during the so-called epoch of reionization. While a few of these UV identified galaxies revealed significant dust reservoirs, very heavily dust-obscured sources at these early times have remained elusive. They are limited to a rare population of extreme starburst galaxies, and companions of rare quasars. These studies conclude that the contribution of dust-obscured galaxies to the cosmic star formation rate density at $z>6$ is sub-dominant. Recent ALMA and Spitzer observations have identified a more abundant, less extreme population of obscured galaxies at $z=3-6$. However, this population has not been confirmed in the reionization epoch so far. Here, we report the discovery of two dust-obscured star forming galaxies at $z=6.6813\pm0.0005$ and $z=7.3521\pm0.0005$. These objects are not detected in existing rest-frame UV data, and were only discovered through their far-infrared [CII] lines and dust continuum emission as companions to typical UV-luminous galaxies at the same redshift. The two galaxies exhibit lower infrared luminosities and star-formation rates than extreme starbursts, in line with typical star-forming galaxies at $z\sim7$. This population of heavily dust-obscured galaxies appears to contribute 10-25 per cent to the $z>6$ cosmic star formation rate density.

Star formation in half of massive galaxies was quenched by the time the Universe was three billion years old. Very low amounts of molecular gas appear responsible for this, at least in some cases, though morphological gas stabilization, shock heating, or activity associated with accretion onto a central supermassive black hole is invoked in other cases. Recent studies of quenching by gas depletion have been based upon upper limits that are insufficiently sensitive to determine this robustly, or stacked emission with its problems of averaging. Here we report 1.3mm observations of dust emission from six strongly lensed galaxies where star formation has been quenched, with magnifications of up to a factor of 30. Four of the six galaxies are undetected in dust emission, with an estimated upper limit on the dust mass of 0.0001 times the stellar mass, and by proxy (assuming a Milky Way molecular gas-to-dust ratio) 0.01 times the stellar mass in molecular gas. This is two orders of magnitude less molecular gas per unit stellar mass than seen in star forming galaxies at similar redshifts. It remains difficult to extrapolate from these small samples, but these observations establish that gas depletion is responsible for a cessation of star formation in some fraction of high-redshift galaxies.

The Compton Spectrometer and Imager (COSI) is a 0.2-5 MeV Compton telescope capable of imaging, spectroscopy, and polarimetry of astrophysical sources. Such capabilities are made possible by COSI's germanium cross-strip detectors, which provide high efficiency, high resolution spectroscopy and precise 3D positioning of photon interactions. Science goals for COSI include studies of 0.511 MeV emission from antimatter annihilation in the Galaxy, mapping radioactive elements from nucleosynthesis, determining emission mechanisms and source geometries with polarization, and detecting and localizing multimessenger sources. The instantaneous field of view (FOV) for the germanium detectors is >25% of the sky, and they are surrounded on the sides and bottom by active shields, providing background rejection as well as allowing for detection of gamma-ray bursts or other gamma-ray flares over >50% of the sky. We have completed a Phase A concept study to consider COSI as a Small Explorer (SMEX) satellite mission, and here we discuss the advances COSI-SMEX provides for astrophysics in the MeV bandpass.

The recently discovered population of interstellar objects presents us with the opportunity to characterize material from extrasolar planetary and stellar systems up close. The forthcoming Rubin Observatory Legacy Survey of Space and Time (LSST) will provide an unprecedented increase in sensitivity to these objects compared to the capabilities of currently operational observational facilities. In this paper, we generate a synthetic population of interstellar objects drawn from their galactic kinematics, and identify the distribution of impact parameters, eccentricities, hyperbolic velocities and sky locations of objects detectable with the LSST. This population is characterized by a clustering of trajectories in the direction of the solar apex and anti-apex, centered at orbital inclinations of $\sim90^\circ$. We identify the ecliptic or solar apex as the optimal sky locations to search for future interstellar objects as a function of survey limiting magnitude. Moreover, we identify the trajectories of detectable objects that will be reachable for $\textit{in situ}$ rendezvous with a dedicated mission with the capabilities of the forthcoming $\textit{Comet Interceptor}$ or proposed $\textit{BRIDGE}$ concept. By scaling our fractional population statistics with the inferred spatial number density, we estimate that the LSST will detect of order $\sim50$ interstellar objects over the course of its $\sim10$ year observational campaign. Furthermore, we find that there should be of order $\sim10$ and $\sim0.05$ reachable targets for missions with propulsion capabilities comparable to $\textit{BRIDGE}$ and $\textit{Comet Interceptor}$, respectively. These number estimates will be readily updateable when the number density and size frequency distribution of interstellar objects is better constrained.

Radial velocity (RV) surveys have discovered hundreds of exoplanetary systems but suffer from a fundamental degeneracy between planet mass $M_p$ and orbital inclination $i$. In this paper we break this degeneracy by combining RVs with complementary absolute astrometry taken from the \Gaia EDR3 version of the cross-calibrated \Hipparcos-\Gaia Catalog of Accelerations (HGCA). We use the Markov Chain Monte Carlo orbit code $\orvara$ to simultaneously fit literature RVs and absolute astrometry from the HGCA. We constrain the orbits, masses, and inclinations of nine single and massive RV companions orbiting nearby G and K stars. We confirm the planetary nature of six companions: HD 29021 b ($4.47_{-0.65}^{+0.67}\Mjup$), HD 81041 b ($7.24_{-0.37}^{+1.0}\Mjup$), HD 87883 b ($6.31_{-0.32}^{+0.31}\Mjup$), HD 98649 b ($9.7_{-1.9}^{+2.3}\Mjup$), HD 106252 b ($10.00_{-0.73}^{+0.78}\Mjup$), and HD 171238 b ($8.8_{-1.3}^{+3.6}\Mjup$). We place one companion, HD 196067 b ($12.5_{-1.8}^{+2.5}\Mjup$) on the planet-brown dwarf boundary, and two companions in the low mass brown dwarf regime: HD 106515 Ab ($18.9_{-1.4}^{+1.5}\Mjup$), and HD 221420 b (${20.6}_{-1.6}^{+2.0}\Mjup$). The brown dwarf HD 221420 b, with a semi-major axis of ${9.99}_{-0.70}^{+0.74}$ AU, a period of ${27.7}_{-2.5}^{+3.0}$ years, and an eccentricity of $0.162_{-0.030}^{+0.035}$ represents a promising target for high-contrast imaging. The RV orbits of HD 87883 b, HD 98649 b, HD 171238 b, and HD 196067 b are not fully constrained yet because of insufficient RV data. We find two possible inclinations for each of these orbits due to difficulty in separating prograde from retrograde orbits, but we expect this will change decisively with future Gaia data releases.

As part of our continuing study of light variability in proto-planetary nebulae (PPNe), we present the results from a long-term study of nine southern hemisphere objects. We have monitored their light variations over a nine-year interval from 2010-2018. These were supplemented by data from the ASAS-SN and ASAS-3 surveys, leading to combined light curves from 2000 to 2020. Pulsation periods were found in seven of the objects, although the three shortest must be regarded as tentative. The periods range from 24 to 73 days. When compared with the results of previous studies of the light variations in PPNe, we find that they show the same trends of shorter period and smaller light variations with higher temperatures. Luminosities were calculated based on the spectral energy distributions, reddening, and Gaia distances, and these confirm the identification of all but one as post-AGB objects. Three of the stars possess long-period variations of 5 to 19 years. These are most likely due to the periodic obscuration of the star by a disk, suggesting the presence of a binary companion and a circumbinary disk.

We present the ALMA detection of molecular outflowing gas in the central regions of NGC4945, one of the nearest starbursts and also one of the nearest hosts of an active galactic nucleus (AGN). We detect four outflow plumes in CO (3-2) at ~0.3" resolution that appear to correspond to molecular gas located near the edges of the known ionized outflow cone and its (unobserved) counterpart behind the disk. The fastest and brightest of these plumes has emission reaching observed line-of-sight projected velocities of over 450 km/s beyond systemic, equivalent to an estimated physical outflow velocity v>600 km/s for the fastest emission. Most of these plumes have corresponding emission in HCN or HCO+ (4-3). We discuss a kinematic model for the outflow emission where the molecular gas has the geometry of the ionized gas cone and shares the rotation velocity of the galaxy when ejected. We use this model to explain the velocities we observe, constrain the physical speed of the ejected material, and account for the fraction of outflowing gas that is not detected due to confusion with the galaxy disk. We estimate a total molecular mass outflow rate dMmol/dt~20 Msun/yr flowing through a surface within 100 pc of the disk midplane, likely driven by a combination of the central starburst and AGN.

The probability density function (PDF) of the logarithmic density contrast, $s=\ln (\rho/\rho_0)$, with gas density $\rho$ and mean density $\rho_0$, for hydrodynamical supersonic turbulence is well-known to have significant signatures of intermittency that monotonically increase with the turbulent Mach number, $\M$. By studying the mass- and volume-weighted $s$-PDF for an ensemble of 16 sub- to trans-Alf\'venic mean-field, supersonic, isothermal turbulence simulations, relevant to molecular gas in the cool interstellar medium, we show that a more intricate picture emerges for the intermittency of $s$. Using four independent measures of the intermittency we find hydrodynamical-like intermittency in the highly magnetised plasma for $\mathcal{M} \lesssim 4$. However, for $\mathcal{M} \gtrsim 4$, the signatures of intermittency disappear, leaving approximately lognormal $s$-statistics -- exactly the opposite of hydrodynamical turbulence in the high-$\mathcal{M}$ limit. To understand the $\mathcal{M} \lesssim 4$ intermittency we use one-dimensional (1D) pencil beams to explore the dynamics along and across the mean magnetic field, $\mathbf{B}_0$. We discuss kinetic, density and magnetic field fluctuations from the pencil beams, and identify physical sources of intermittency as single, strong shocks coupled to fast magnetosonic compressions that form along $\Bo$ and create large, volume-poor under-densities. These under-densities contribute significantly to the skewness of the $s$-PDF. We confirm this result independently using 1D fluid shock simulations. We discuss the Gaussianisation of the $\mathcal{M} \gtrsim 4$ $s$-fields through the lens of two phenomenologies: the self-similarity of the $s$-field and homogenisation of the dynamical timescales between the over- and under-dense regions in the compressible gas.

Targeted observations of possible exomoon host systems will remain difficult to obtain and time-consuming to analyze in the foreseeable future. As such, time-domain surveys such as Kepler, K2 and TESS will continue to play a critical role as the first step in identifying candidate exomoon systems, which may then be followed-up with premier ground- or space-based telescopes. In this work, we train an ensemble of convolutional neural networks (CNNs) to identify candidate exomoon signals in single-transit events observed by Kepler. Our training set consists of ${\sim}$27,000 examples of synthetic, planet-only and planet+moon single transits, injected into Kepler light curves. We achieve up to 88\% classification accuracy with individual CNN architectures and 97\% precision in identifying the moons in the validation set when the CNN ensemble is in total agreement. We then apply the CNN ensemble to light curves from 1880 Kepler Objects of Interest with periods $>10$ days ($\sim$57,000 individual transits), and further test the accuracy of the CNN classifier by injecting planet transits into each light curve, thus quantifying the extent to which residual stellar activity may result in false positive classifications. We find a small fraction of these transits contain moon-like signals, though we caution against strong inferences of the exomoon occurrence rate from this result. We conclude by discussing some ongoing challenges to utilizing neural networks for the exomoon search.

We present a spectrum of the planetary nebula M 2-36 obtained using the Ultra Violet and Visual Echelle Spectrograph (UVES) at the Very Large Telescope (VLT). 446 emission lines are detected. We perform an analysis of the chemical composition using multiple electron temperature ($T_{e}$) and density ($n_{e}$) diagnostics. $T_{e}$ and $n_{e}$ are computed using a variety of methods, including collisionally excited line (CEL) ratios, O$^{++}$ optical recombination lines (ORLs), and measuring the intensity of the Balmer jump. Besides the classical CEL abundances, we also present robust ionic abundances from ORLs of heavy elements. From CELs and ORLs of O$^{++}$, we obtain a new value for the Abundance Discrepancy Factor (ADF) of this nebula, being ADF(O$^{++})=$ 6.76 $\pm$ 0.50. From all the different line ratios that we study, we find that the object cannot be chemically homogeneous; moreover, we find that two-phased photoionization models are unable to simultaneously reproduce critical \ion{O}{ii} and [\ion{O}{iii}] line ratios. However, we find a three-phased model able to adequately reproduce such ratios. While we consider this to be a toy model, it is able to reproduce the observed temperature and density line diagnostics. Our analysis shows that it is important to study high ADF PNe with high spectral resolution, since its physical and chemical structure may be more complicated than previously thought.

We have studied the influence of an evolving gravitational potential of the Milky Way Galaxy on the orbital motion of 152 globular clusters with proper motions from the Gaia EDR3 catalogue and mean distances from Baumgardt and Vasiliev (2021). To construct a semicosmological evolving model potential with changing masses and sizes of the Galactic components, we have used the algorithm described in Haghi et al. (2015). The adopted axisymmetric three-component model potential of the Galaxy includes a spherical bulge, a flat Miyamoto--Nagai disk, and a spherical Navarro--Frenk--White dark matter halo.The orbits are integrated backward in time. We compare the orbital parameters of globular clusters derived in static and evolving potentials when integrating the orbits for 5 and 12 Gyr backward. For the first time we have studied the influence of separately a change in the masses and a change in the sizes of the Galactic components. The changes in the masses and sizes of the components are shown to act on the orbital parameters in the opposite way. At small Galactocentric distances this influence is maximally compensated for. The orbits of distant globular clusters and those with a large apocenter distance undergo the biggest changes. We show that on time scales up to $-5$~Gyr the orbits of globular clusters in the case of a potential with both changing masses and changing sizes of the components undergo, on average, minor changes compared to the case of a static potential. These changes fit into the limits of the statistical uncertainties caused by the errors in the data. So, on these time scales the Galactic potential may be deemed static. We provide tables with the orbital parameters of globular clusters derived in both static and evolving potentials.

Observation of fast radio bursts (FRBs) are rising very quickly with the advent of specialised instruments and surveys, and it has recently been shown that some of them repeat quasi-periodically. In particular, evidence of a $P=16.35$ day period has been reported for FRB 180916.J0158+65. We seek an explanation within the frame of our orbiting asteroid model, whereby FRBs are produced in the plasma wake of asteroids immersed in the wind of a pulsar or a magnetar. We used the data reported by the CHIME/FRB collaboration in order to infer the orbital characteristics of asteroid swarms, and performed parametric studies to explore the possible characteristics of the pulsar, its wind, and of the asteroids, under the constraint that the latter remain dynamically and thermally stable. We found a plausible configuration in which a young pulsar is orbited by a main $\sim 10^{-3}M_\odot$ companion with a period $3P = 49$d, three times longer than the apparent periodicity $P$. Asteroids responsible for FRBs are located in three dynamical swarms near the L3, L4 and L5 Lagrange points, in a 2:3 orbital resonance akin to the Hildas class of asteroids in the Solar system. In addition, asteroids could be present in the Trojan swarms at the L4 and L5 Lagrange points. Together these swarms form a carousel that explains the apparent $P$ periodicity and dispersion. We estimated that the presence of at least a few thousand asteroids, of size $\sim20$km, is necessary to produce the observed burst rate. We show how radius-to-frequency mapping in the wind and small perturbations by turbulence can suffice to explain downward-drifting sub-pulses, micro-structures, and narrow spectral occupancy.

We study mass accretion and ejection in the vicinity of massive star forming cores using high-resolution (5 au) 3D AMR numerical simulations. We investigate the mechanisms at the origin of outflows and characterise the properties of the disc forming around massive protostars. We include both protostellar radiative feedback via PMS evolutionary tracks and magnetic ambipolar diffusion. We studied 3 different cases: purely hydrodynamical, ideal MHD, and ambipolar diffusion. In the resistive models, we investigate the effects the initial amplitude of both magnetic field and rotation have on the properties of the massive protostellar system. We use simple criteria to identify the outflow and disc material and follow their evolution as the central star accretes mass up to 20 solar mass. The outflow is completely different when magnetic fields are introduced, so that magnetic processes are the main driver of the outflow up to stellar masses of ~20 solar mass. The disc properties depend on the physics included. The disc formed in the ideal and resistive runs show opposite properties in terms of plasma beta and of magnetic fields topology. While the disc in the ideal case is dominated by the magnetic pressure and the toroidal magnetic fields, the one formed in the resistive runs is dominated by the thermal pressure and has essentially vertical magnetic fields in the inner regions (R<200 au). We find that magnetic processes dominate the early evolution of massive protostellar systems (<20 solar mass) and shapes the accretion/ejection as well as the disc formation. Ambipolar diffusion is mainly at work at disc scales and regulates its properties. Our finding for the outflow and disc properties are reminiscent of low-mass star formation, suggesting that accretion and ejection in young massive and low-mass protostars are regulated by the same physical processes at the early stages.

We aim to characterize the magnetospheric accretion process in the young stellar object V807 Tau, one of the most stable dippers revealed by K2 in the Taurus star forming region. We performed photometric and spectropolarimetric follow-up observations of this system with CFHT/ESPaDOnS in order to investigate its variability over several rotational periods. We derive a 4.38 day period from the K2 light curve. This period is also seen in the radial velocity variations, ascribed to spot modulation. The narrow component of the He I 5876 {\AA} line as well as the red wing of the H{\beta} and H{\gamma} line profiles also vary in intensity with the same periodicity. The former traces the accretion shock at the stellar surface, and the latter is a signature of an accretion funnel flow crossing the line of sight. We derive a surface brightness and magnetic field topology from the modeling of Stokes I and V profiles, respectively, for photospheric lines and for the He I line. This reveals a bright spot at the stellar surface, located at a latitude of 60 deg, and a maximum field strength of about 2 kG. The magnetic field topology at the stellar surface is dominated by a dipolar component inclined by about 40 deg onto the spin axis. Despite of its clear and stable dipper behavior, we derive a relatively low inclination of about 50 deg for this system, which calls question the origin of the dips. This low inclination is also consistent with the absence of deep inverse P Cygni components in the line profiles. We conclude that magnetospheric accretion is ongoing in V807 Tau, taking place through non-axisymmetric accretion funnel flows controlled by a strong, tilted, and mainly dipolar magnetic topology. Whether an inner disk warp resulting from this process can account for the dipper character of this source remains to be seen, given the low inclination of the system.

For the first time, the argon abundance relative to hydrogen abundance (Ar/H) in the narrow line region of a sample of Seyfert 2 nuclei has been derived. In view of this, optical narrow emission line intensities of a sample of 64 local Seyfert 2 nuclei (z < 0.25) taken from Sloan Digital Sky Survey DR7 and measured by the MPA/JHU group were considered. We adopted the Te-method for AGNs, which is based on direct determination of the electron temperature, together with a grid of photoionization model results, built with the Cloudy code, to obtain a method for the derivation of the Ar/H abundance. We find that for a metallicity range of 0.2 < (Z/Zsolar) < 2.0, Seyfert 2 nuclei present Ar/H abundance ranging from 0.1 to 3 times the argon solar value, adopting log(O/H)=-3.31 and log(Ar/H)=-5.60. These range of values correspond to 8.0 < 12+log(O/H)< 9.0 and 5.4 < 12+log(Ar/H)< 6.9, respectively. The range of Ar/H and Ar/O abundance values obtained from our sample are in consonance with estimations from extrapolations of the radial abundance gradients to the central parts of the disk for four spiral galaxies. We combined our abundance results with estimates obtained from a sample of Hii galaxies, which were taken from the literature, and found that the Ar/O abundance ratio decreases slightly as the O/H abundance increases.

Studies of high redshift radio galaxies can shed light on the activity of active galactic nuclei (AGN) in massive elliptical galaxies, and on the assembly and evolution of galaxy clusters in the Universe. The vast majority of observed high redshift ($z>4.5$) AGN are quasars, with very few galaxies. J1606+3124 is a radio galaxy at a redshift of 4.56, at an era of one-tenth of the current age of the Universe. Very long baseline interferometry (VLBI) images reveal a two-sided jet structure with edge-brightened terminal hotspots separated by about 68 parsecs. No evidence for the presence of extended emission (relic of past activity) is found, suggesting that it might be a nascent radio source. We study the radio properties of J1606+3124, including radio spectrum, variability, core brightness temperature, jet proper motion. All observations consistently indicate that it is a GHz Peaked Spectrum (GPS) source, making it the highest redshift GPS galaxy known to date. The expansion velocity of the hotspots and the turnover in the radio spectrum suggest that J1606+3124 is a young (kinematic age of $\sim$3000 years) and developing radio source. Its ultra-high jet power gives it a good chance to grow into a large-scale double-lobe radio galaxy. Infrared observations reveal a gas- and dust-rich host galaxy environment, which may hinder the jet growth.

We present detailed stellar specific angular momentum ($j_*$) measurements of ten star-forming galaxies at $z\sim1.5-2$ using both high and low spatial resolution integral field spectroscopic data. We developed a code that simultaneously models the adaptive optics (AO) assisted observations from OSIRIS/SINFONI along with their natural seeing (NS) counterparts from KMOS at spatial resolutions of [$0.1-0.4$] arcsec and [$0.6-1.0$] arcsec respectively. The AO data reveals 2/10 systems to be mergers and for the remaining eight the mean uncertainties $\bar \Delta j_*$ decrease from 49% (NS), and 26.5% (AO), to 16% in the combined analysis. These $j_*$ measurements agree within 20% with simple estimates ($\tilde{j_*}$) calculated from the Hubble Space Telescope photometry and NS kinematics, however higher resolution kinematics are required to first identify these disks. We find that the choice of surface mass density model and the measurement of effective radius from photometry are the key sources of systematic effects in the measurement of $j_*$ between different analyses. Fitting the $j_*$ vs $M_*$ relations (Fall, 1983) with a fixed power-law slope of $\beta=2/3$, we find a zero-point consistent with prior NS results at $z\geq1$ within $\sim 0.3$ dex. Finally, we find a $\sim 0.38$ dex scatter about that relation that remains high despite the AO data so we conclude it is intrinsic to galaxies at $z>1$. This compares to a scatter of $\leq 0.2$ dex for disks at $z\simeq0$ pointing to a settling of the Fall relation with cosmic time.

The lack of short baselines, referred to as short-spacing problem (SSP), is a well-known limitation of the performance of radio interferometers, causing a reduction of the detected flux at increasing angular distances from the target. The very large number of antennas operated in the Atacama Large Millimeter/sub-millimeter Array (ALMA) generates situations for which the impact of the SSP takes a complex form, not simply measurable by a single number, such as the Maximal Recoverable Scale. In particular extended antenna configurations, complemented by a small group of closeby antennas at the centre of the array, may result in a double-humped baseline distribution with a significant gap between the two groups. In such cases one should adopt as effective maximal recoverable scale that associated with the extended array and use only the central array to recover missing flux, as one would do with single dish or ACA (Atacama Compact Array) observations. The impact of the missing baselines can be very important and may easily be underestimated, or even overlooked. The present study uses archival observations of the $^{29}$SiO(8-7) line emission of AGB star W Hya as an illustration. A critical discussion of the reliability of the observations away from the star is presented together with comments of a broader scope. Properties of the circumstellar envelope of W Hya within 15 au from the star, not mentioned in the published literature, are briefly described and compared with R Dor, an AGB star having properties very similar to W Hya.

When the pressure of particles accelerated at shock waves is no longer negligible compared to the kinetic pressure of the gas, the linear theory of diffusive shock acceleration breaks down. This is expected in particular when the shock sweeps up preexisting cosmic rays, or when multiple shocks reaccelerate successively the same particles. To describe these systems, one has to account for the nonlinear backreaction of the particles on the magnetohydrodynamic flow. Using an up-to-date semi-analytical model of particle reacceleration at nonlinear shocks, we show that the presence of prexisting energetic particles strongly affects the shock profile, in such a way that the reacceleration of non thermal particles or the acceleration of particles from the thermal bath becomes less efficient. We further describe the evolution of the distribution of particles after several shocks and study the properties of the asymptotic solution. We detail the case of identical shocks as well as more realistic scenarios, including the heating of the medium or superbubble environments. When the particles are efficiently confined in the acceleration region, it is generally found that the spectrum converges toward a concave solution after a few tens of shocks, with a spectral index around 3.5 at the highest energy. The postshock cosmic ray pressure reaches an asymptotic value of about 4-5% of the ram pressure of one shock. Most of the shock pressure is transferred to escaping particles.

Population III (Pop III) stars ended the cosmic Dark Ages and began early cosmological reionization and chemical enrichment. However, in spite of their importance to the evolution of the early Universe, their properties remain uncertain because of limitations to previous numerical simulations and the lack of any observational constraints. Here we investigate Pop III star formation in five primordial halos with 3D radiation-hydrodynamical cosmological simulations. We find that multiple stars form in each minihalo and that their numbers increase over time, with up to 23 stars forming in one of the halos. Radiative feedback from the stars generates strong outflows, deforms the surrounding protostellar disk, and delays star formation for a few thousand years. Star formation rates vary with halo and depend on mass accretion onto the disk, halo spin number, and the fraction of massive stars in the halo. Stellar masses in our models range from 0.1-37 \Ms, and of the 55 stars that form in our models twelve are $\rm > 10~ \Ms$ and most of the others are 1-10 \Ms. Our simulations thus suggest that Pop III stars have characteristic masses of 1-10 \Ms and a top-heavy IMF with dN/dM $\propto M_*^{-1.18}$. Up to 70\% of the stars are ejected from their disks by three-body interactions which, along with ionizing UV feedback, limits their final masses.

We aim to demonstrate that the presence and mass of an exoplanet can now be effectively derived from the astrometry of another exoplanet. We combined previous astrometry of $\beta$ Pictoris b with a new set of observations from the GRAVITY interferometer. The orbital motion of $\beta$ Pictoris b is fit using Markov chain Monte Carlo simulations in Jacobi coordinates. The inner planet, $\beta$ Pictoris c, was also reobserved at a separation of 96\,mas, confirming the previous orbital estimations. From the astrometry of planet b only, we can (i) detect the presence of $\beta$ Pictoris c and (ii) constrain its mass to $10.04^{+4.53}_{-3.10}\,M_{\rm Jup}$. If one adds the astrometry of $\beta$ Pictoris c, the mass is narrowed down to $9.15^{+1.08}_{-1.06}\,M_{\rm Jup}$. The inclusion of radial velocity measurements does not affect the orbital parameters significantly, but it does slightly decrease the mass estimate to $8.89^{+0.75}_{-0.75}\,M_{\rm Jup}$. With a semimajor axis of $2.68\pm0.02$\,au, a period of $1221\pm15$ days, and an eccentricity of $0.32\pm0.02$, the orbital parameters of $\beta$ Pictoris c are now constrained as precisely as those of $\beta$ Pictoris b. The orbital configuration is compatible with a high-order mean-motion resonance (7:1). The impact of the resonance on the planets' dynamics would then be negligible with respect to the secular perturbations, which might have played an important role in the eccentricity excitation of the outer planet.

Gaussian processes (GPs) are used widely in the analysis of astronomical time series. GPs with rational spectral densities have state-space representations which allow O(n) evaluation of the likelihood. We calculate analytic state space representations for the damped simple harmonic oscillator and the Mat\'ern 1/2, 3/2 and 5/2 processes.

Near-Earth asteroid (469219) Kamo'oalewa (aka 2016 HO3) is an Earth co-orbital and a potential space mission target. Its short-term dynamics is characterized by a periodic switching between quasi-satellite and horseshoe configurations. Due to its small diameter of only about 36 meters, the Yarkovsky effect may play a significant role in the long-term dynamics. In this work, we addressed this issue by studying the changes in the long-term motion of Kamo'oalewa caused by the Yarkovsky effect. We used an estimation of the magnitude of the Yarkovsky effect assuming different surface compositions and introduced the semi-major axis drift by propagating orbits of test particles representing the clones of the nominal orbit. Our simulations showed that the Yarkovsky effect may cause Kamo'oalewa to exit from the Earth co-orbital region a bit faster when compared to a purely gravitational model. Nevertheless, it still could remain an Earth companion for at least 0.5 My in the future. Our results imply that Kamo'oalewa is the most stable Earth's co-orbital object known so far, not only from a short-term perspective but also on long time scales.

The radio quasar luminosity function exhibits an upturn around $L_{6\rm\:GHz}=10^{23}$ W Hz$^{-1}$ that is well-modelled by a star-forming host galaxy population. This distribution leads some authors to cite star formation as the main radio emission mechanism in so-called radio-quiet quasars (RQQs). Understanding the origin of RQQ radio emission is crucial for our understanding of quasar feedback mechanisms -- responsible for the regulation of star-formation in the host galaxy -- and for understanding galaxy evolution as a whole. By observing RQQs that have been magnified by strong gravitational lensing, we have direct access to the RQQ population out to cosmic noon, where evidence for twin mini-jets has recently been found in a sub-\textmu Jy RQQ. Here we present radio observations of two lensed RQQs using the VLA at 5~GHz, the latest objects to be observed in a sample of quadruply-imaged RQQs above -30$^{\circ}$. In SDSS~J1004+4112 we find strong evidence for AGN-related radio emission in the variability of the source. In PG~1115+080 we find tentative evidence for AGN-related emission, determined by comparing the radio luminosity with modelled dust components. If confirmed in the case of PG~1115+080, which lies on the radio--FIR correlation, the result would reinforce the need for caution when applying the correlation to rule out jet activity and when assuming no AGN heating of FIR-emitting dust when calculating star formation rates. Our programme so far has shown that two of the faintest radio sources ever imaged show strong evidence for AGN-dominated radio emission.

In this work we generalize the idea of a gravitational phase transition or GPT at late times to allow for a modified gravity scenario in the early universe as well. The original GPT was shown to simultaneously relax the $H_0$ and $\sigma_8$ tensions and {\it Planck} internal inconsistencies. However, the primary results from GPT predictions implied disagreement with the data from the baryonic acoustic oscillations (BAO). Here we investigate whether the generalized GPT scenario could address the Hubble tension in the presence of the BAO data as well. We find that, despite the vastly enlarged gravitational parameter space, the BAO data strongly prefer the $\Lambda$CDM paradigm with a low inferred Hubble constant, $68.03\pm 0.76 $ km/s/Mpc, in tension with the local $H_0$ measurements from Riess et al., $H_0=74.03\pm 1.42$ km/s/Mpc. This failure of the generalized GPT scenario to host the P18-BAO-R19 trio is of significance and noticeably shrinks the space of possible gravitational solutions to the Hubble tension.

It has been recently demonstrated that both, a classical Schwarzschild black hole (BH), and a dense concentration of self-gravitating fermionic dark matter (DM) placed at the Galaxy centre, can explain the precise astrometric data (positions and radial velocities) of the S-stars orbiting SgrA*. This result encompasses the 17 best resolved S-stars, and includes the test of general relativistic effects such as the gravitational redshift in the S2-star. In addition, the DM model features another remarkable result: the dense core of fermions is the central region of a continuous density distribution of DM whose diluted halo explains the Galactic rotation curve. In this Letter, we complement the above findings by analyzing in both models the relativistic periapsis precession of the S2-star orbit. While the Schwarzschild BH scenario predicts a unique prograde precession for S2, in the DM scenario it can be either retrograde or prograde, depending on the amount of DM mass enclosed within the S2 orbit, which in turn is a function of the DM fermion mass. We show that all the current and publicly available data of S2 can not discriminate between the two models, but upcoming S2 astrometry close to next apocentre passage could potentially establish if SgrA* is governed by a classical BH or by a quantum DM system.

With the aim of unravelling the complexity of the morpho-kinematics of the circumstellar envelope (CSE) of Mira Ceti, we review, extend and possibly revisit ALMA millimetre observations of the emission of the SiO(5-4) and CO(3-2) molecular lines, including a new analysis of the optically thin $^{13}$CO(3-2) emission. In agreement with observations at shorter wavelengths, we give evidence for confinement of a dense gas volume within $\sim$50 au from the star and for a broad SiO line-width within $\sim$15 au. We show that the mass loss rate is episodic and takes the form of clumps having a very low SiO/CO abundance ratio. We evaluate the current mass loss rate as (8$\pm$4)$\times$10$^{-8}$ M$_\odot$ yr$^{-1}$ , much smaller than usually assumed. We argue that the SiO emission observed in the south-western quadrant is not related to the mechanism of generation of the nascent wind but results from dust grains outgassing SiO molecules, in support of an earlier interpretation in terms of a mass ejection that occurred eleven years before the observations. We remark that Mira Ceti is not a good archetype in terms of its wind: lower mass AGB stars, with a mass loss rate at the level of a few 10$^{-7}$ M$_\odot$ yr$^{-1}$ and preferably no companion are better suited for developing models of the very complex gas-dust chemistry at stake in the CSE of oxygen-rich AGB stars.

Galaxy angular-power spectrum and autocorrelation functions (ACFs) provide information about the distribution of matter by using galaxy counts as a proxy. In this study, we are going to estimate autocorrelation angular power spectrum and angular autocorrelation function for EMU-ASKAP 5 sigma sources and then compare them with results from NVSS. We will also use SUMSS data to compare ACF results using Landy-Szalay estimator. EMU-ASKAP will provide excellent opportunity to observe universe with high sensitivity and is likely going to observe millions of high redshift sources which will help in studying the clustering of the large scale structures, constraining cosmological parameters and exploring mysteries like the existence of a cosmic cold spot or the CMB cold spot as observed by both Planck and WMAP probes. We will discuss some possible ways, the CMB cold spot puzzle can be explored further by using the galaxy clustering, integral source count and galaxy bias analysis with a highly sensitive survey like EMU-ASKAP.

In this paper, we report the relative SNe contributions on the metal budget of the ICM of Abell 1837 galaxy cluster at redshift z $=$ 0.069. For this purpose, we analysed the hot ICM of the cluster and obtained radial metal distributions by using XMM-Newton archival data with total exposure $\sim$100 ks. These metal measurements consist of Mg, Si, S, Fe and Ni within 0.7 R$_{500}$ radius which is divided into three concentric annuli. In order to explain the observed metal abundance pattern in terms of relative supernova contributions, we used our newly developed code SNeRatio which utilizes theoretical nucleosynthesis models. This study covers the most recent 3D SNIa and SNcc yield tables. All combinations of these theoretical yields were fitted with our measured abundance ratios and statistically acceptable ones were selected. Each of these models were found to predict a uniform SNIa percentage contribution to the total SNe from the cluster center to the outskirts and form an SNIa ratio distribution with a mean 39 $\pm$ 14$\%$. This uniformity is consistent with the early enrichment scenario which assumes that the metal production processes begin in early phase of cluster formation, namely proto-cluster phase at epoch z $\geq$ 2.

In this decade astronomy is undergoing a paradigm shift to handle data from next generation observatories such as the Square Kilometre Array (SKA) or the Vera C. Rubin Observatory (LSST). Producing real time data streams of up to 10 TB/s and data products of the order of 600 Pbytes/year, the SKA will be the biggest civil data producing machine of the world that demands novel solutions on how these data volumes can be stored and analysed. Through the use of complex, automated pipelines the provenance of this real time data processing is key to establish confidence within the system, its final data products, and ultimately its scientific results. The intention of this paper is to lay the foundation for making an automated provenance generation tool for astronomical/data-processing pipelines. We therefore present a use case analysis, specific to the astronomical needs which addresses the issues of trust and reproducibility as well as other ulterior use cases which are of interest to astronomers. This analysis is subsequently used as the basis to discuss the requirements, challenges, and opportunities involved in designing both the tool and the associated provenance model.

Context. In asteroseismology the pulsation mode frequencies of a star are the fundamental data that are compared to theoretical predictions to determine a star's interior physics. Recent significant advances in the numerical, theoretical and statistical asteroseismic methods applied to main sequence stars with convective cores have renewed the interest in investigating the propagation of observational uncertainties within a forward asteroseismic modelling framework. Aims. We aim to quantify the impact of various choices made throughout the observational aspects of extracting pulsation mode frequencies in main sequence stars with gravity modes. Methods. We use a well-studied benchmark slowly pulsating B star, KIC 7760680, to investigate the sensitivity of forward asteroseismic modelling to various sources of observational uncertainty that affect the precision of the input pulsation mode frequencies. Results. We quantify the impact of the propagation of the observational uncertainties involved in forward asteroseismic modelling. We find that one of the largest sources of uncertainty in our benchmark star is in the manual building of period spacing patterns, such that the inclusion of a potentially ambiguous pulsation mode frequency may yield differences in model parameters of up to 10% for mass and age depending on the radial order of the mode. Conclusions. We conclude that future asteroseismic studies of main sequence stars with a convective core should quantify and include observational uncertainties introduced by the light curve extraction, iterative pre-whitening and the building of period spacing patterns, as these propagate into the final modelling results.

A superconducting microstrip half-wavelength resonator is proposed as a suitable band-pass filter for broadband moderate spectral resolution spectroscopy for terahertz (THz) astronomy. The proposed filter geometry has a free spectral range of an octave of bandwidth without introducing spurious resonances, reaches a high coupling efficiency in the pass-band and shows very high rejection in the stop-band to minimize reflections and cross-talk with other filters. A spectrally sparse prototype filter-bank in the band 300-400 GHz has been developed employing these filters as well as an equivalent circuit model to anticipate systematic errors. The fabricated chip has been characterized in terms of frequency response, reporting an average peak coupling efficiency of 27% with an average spectral resolution of 940.

The disk around HD 169142 has been suggested to host multiple embedded planets due to the range of structures observed in the dust distributions. We analyze archival ALMA observations of $^{12} \mathrm{CO \ (2-1)}$, $^{13} \mathrm{CO \ (2-1)}$, and $\mathrm{C}^{18} \mathrm{O \ (2-1)}$ to search for large-scale kinematic structures associated with other embedded planets in the outer disk. At 125 au, we identify a coherent flow from the disk surface to the midplane, traced by all three CO isotopologues, and interpret it as a meridional flow, potentially driven by an embedded planet. We use changes in the rotation speed of the gas to characterize the physical structure across this region, finding that at 125 au the CO emission traces regions of increased gas pressure, despite being at a surface density minimum. Developing a simple analytical model, we demonstrate that the physical structure of the gap can have non-trivial responses to changes in the surface density, consistent both with previous thermo-chemical models, and the conditions inferred observationally. Applying this technique to a range of sources will allow us to directly confront theoretical models of gap-opening in protoplanetary disks.

In theoretical models of galaxy evolution, AGN and star formation (SF) activity are closely linked and AGN feedback is routinely invoked to regulate galaxy growth. In order to constrain such models, we compare the hydrodynamical simulations IllustrisTNG and SIMBA, and the semi-analytical model SAG to the empirical results on AGN and SF at cosmic noon ($0.75 < z < 2.25$) reported in Florez et al. (2020). The empirical results are based on a large mass-complete sample drawn from 93,307 galaxies with and without high X-ray luminosity AGN ($L_X \gtrsim 10^{44}$ erg s$^{-1}$), selected from a 11.8 deg$^2$ area ($\sim 0.18$ Gpc$^3$ comoving volume at $z=0.75-2.25$). The main results of our comparisons are: (i) SAG and IllustrisTNG both qualitatively reproduce the empirical result that galaxies with high X-ray luminosity AGN have higher mean SFR, at a given stellar mass, than galaxies without such AGN. SAG, however, strongly over-produces the number density of high X-ray luminosity AGN by a factor of 10 to 100, while IllustrisTNG shows a lack of high X-ray luminosity AGN at high stellar mass ($M* > 10^{11} \ M_{\odot}$) at $z \sim 2$. (ii) In SIMBA, the mean SFR of galaxies with high X-ray luminosity AGN is lower than the SFR of galaxies without such AGN. Contrary to the data, many high X-ray luminosity AGN in SIMBA have quenched SF, suggesting that AGN feedback, or other feedback modes in galaxies with such AGN, might be too efficient in SIMBA.

Cosmic rays can penetrate planetary atmospheres driving the formation of prebiotic molecules, which are important for the origin of life. We calculate the Galactic cosmic ray fluxes in the habitable zone of five nearby, well-studied solar-type stars and at the orbits of 2 known exoplanets. We model the propagation of Galactic cosmic rays through the stellar winds using a combined 1.5D stellar wind and 1D cosmic ray transport model. We find that the habitable zone of 61 Cyg A has comparable Galactic cosmic ray fluxes to present-day Earth values. For the other four systems ($\epsilon$ Eri, $\epsilon$ Ind, $\xi$ Boo B and $\pi^1$ UMa), the fluxes are orders of magnitude smaller than Earth values. Thus, it is unlikely that any as-of-yet undetected Earth-like planets in their habitable zones would receive a higher radiation dose than is received on Earth. $\epsilon\,$Ind$\,$b, a Jupiter-like planet orbiting at $\sim$11au, receives higher Galactic cosmic ray fluxes than Earth. We find the suppression of Galactic cosmic rays is influenced by whether diffusion or advection dominates at GeV energies and at distances where the wind has reached its' terminal velocity. For advectively-dominated winds ($\sim$younger systems), varying the astrospheric size influences the suppression significantly. For diffusion-dominated systems ($\sim$older systems) the astrospheric size, and therefore knowledge of the ISM properties, are not very important. This reduces the Galactic cosmic ray flux uncertainties in the habitable zone for diffusion-dominated systems. Whether a system is advection- or diffusion-dominated can be determined from the stellar wind properties.

Structures in the solar corona are the main drivers of space weather processes that might directly or indirectly affect the Earth. Thanks to the most recent space-based solar observatories, with capabilities to acquire high-resolution images continuously, the structures in the solar corona can be monitored over the years with a time resolution of minutes. For this purpose, we have developed a method for automatic segmentation of solar corona structures observed in EUV spectrum that is based on a deep learning approach utilizing Convolutional Neural Networks. The available input datasets have been examined together with our own dataset based on the manual annotation of the target structures. Indeed, the input dataset is the main limitation of the developed model's performance. Our \textit{SCSS-Net} model provides results for coronal holes and active regions that could be compared with other generally used methods for automatic segmentation. Even more, it provides a universal procedure to identify structures in the solar corona with the help of the transfer learning technique. The outputs of the model can be then used for further statistical studies of connections between solar activity and the influence of space weather on Earth.

TOI-1266c is a recently discovered super-Venus in the radius valley orbiting an early M dwarf. However, its notional bulk density ($\sim$2.2 g cm$^{-3}$) is consistent with a large volatile fraction, suggesting that it might have volatile reservoirs that have survived billions of years at more than twice the Earth's insolation. On the other hand, the upper mass limit paints a picture of a cool super Mercury dominated by >50\% iron core ($\sim$9.2 g cm$^{-3}$) that has tiptoed up to the collisional stripping limit and into the radius gap. Here, we examine several hypothetical states for TOI-1266c using a combination of new and updated open-source atmospheric escape, radiative-convective, and photochemical models. We find that water-rich atmospheres with trace amounts of H$_{2}$ and CO$_{2}$ are potentially detectable (SNR $>\sim 5$) in less than 20 hours of JWST observing time. We also find that water vapor spectral features are not substantially impacted by the presence of high-altitude water or ice clouds due the presence of a significant amount of water above the cloud-deck, although further work with self-consistent cloud models is needed. Regardless of its mass, however, TOI-1266c represents a unique proving ground for several hypotheses related to the evolution of sub-Neptunes and Venus-like worlds, particularly those near the radius valley.

The era of multi-messenger astrophysics has arrived, leading to key new discoveries and revealing a need for coordination, collaboration, and communication between world-wide communities using ground and space-based facilities. To fill these critical needs, NASA's Goddard Space Flight Center and Marshall Space Flight Center are jointly proposing to establish a virtual Multi-Messenger Astrophysics Science Support Center that focuses entirely on community-directed services. In this article, we describe the baseline plan for the virtual Support Center which will position the community and NASA as an Agency to extract maximum science from multi-messenger events, leading to new breakthroughs and fostering increased coordination and collaboration.

We present a purely differential line-of-sight distance between M31 and M33 using ab-type RR Lyrae variables observed in each galaxy by the Hubble Space Telescope Advanced Camera for Surveys in the F606W filter. Using 1501 RR Lyraes in 13 M31 fields and 181 RR Lyraes in six M33 fields, and placing all of these stars on a uniform photometric scale with internally consistent corrections for metal abundance and extinction, we find a relative absolute distance modulus of D(m-M)_o = -0.298 +/- 0.016 in the sense of (m-M)_{o,M31} - (m-M)_{o,M33}. Adopting an absolute distance modulus of (m-M)_o=24.46 +/- 0.10 for M31 places M33 115 kpc beyond M31 in line-of-sight distance.

We study the clustering of Gravitational Wave (GW) merger events and Supernovae IA (SN), as cosmic tracers in Luminosity Distance Space. We modify the publicly available CAMB code to numerically evaluate auto- and cross- power spectra for the different sources, including Luminosity Distance Space distortion effects generated by peculiar velocities and lensing convergence. We perform a multitracer Fisher analysis to forecast expected constraints on cosmological and GW bias coefficients, using outputs from hydrodinamical N-body simulations to determine the bias fiducial model and considering future observations from the Vera Rubin Observatory and Einstein Telescope (ET), both single and in a 3 detector network configuration. We find that adding SN to the GW merger dataset considerably improves the forecast, mostly by breaking significant parameter degeneracies, with final constraints comparable to those obtainable from a Euclid-like survey. GW merger bias is forecasted to be detectable with good significance even in the single ET case.

We present results from MUSE observations following up on a 21-cm \ion{H}{i} absorption system detected with the Australian Square Kilometre Array Pathfinder radio telescope at redshift $0.4503$ towards the quasar PKS 1610-771. This \ion{H}{i} absorber has a column density $N_{HI} = 2.7 \pm 0.1 \times 10^{20} \cdot \rm{[T_{s}/100 K]} \cdot \rm{cm}^{-2}$, making it a likely Damped Lyman-$\alpha$ (DLA) system. We identify a galaxy group with four members (A, B, X and Y) at the same redshift as the \ion{H}{i} absorption system, with impact parameters ranging from less than 10\,kpc to almost 200\,kpc from the quasar sightline. \ion{Ca}{ii} and \ion{Na}{i} absorption is also seen in the MUSE spectrum of the background QSO, with velocities coinciding with the initial \ion{H}{i} $21$-cm detection, but tracing less dense and potentially warmer gas. This metal-line component aligns with the rotating ionized disc of galaxy B (impact parameter $18$ kpc from the QSO) and appears to be co-rotating with the galaxy disc, although outflowing gas cannot be directly excluded. In contrast, the $21$-cm \ion{H}{i} absorber is blueshifted relative to the galaxies nearest the absorber and has the opposite sign to the velocity field of galaxy B. Since galaxies A and B are separated by only $17$ kpc on the sky and $70$ km s$^{-1}$ in velocity, it is likely that the $21$-cm detection traces extragalactic clouds of gas formed from their interaction. This system represents a first case study of the cold gas detected in galaxy groups by future large $21$-cm absorption surveys, such as the First Large Absorption Survey in \ion{H}{i}.

High-resolution spectroscopic surveys of the Milky Way have entered the Big Data regime and have opened avenues for solving outstanding questions in Galactic Archaeology. However, exploiting their full potential is limited by complex systematics, whose characterization has not received much attention in modern spectroscopic analyses. In this work, we present a novel method to disentangle the component of spectral data space intrinsic to the stars from that due to systematics. Using functional principal component analysis on a sample of $18,933$ giant spectra from APOGEE, we find that the intrinsic structure above the level of observational uncertainties requires ${\approx}$10 Functional Principal Components (FPCs). Our FPCs can reduce the dimensionality of spectra, remove systematics, and impute masked wavelengths, thereby enabling accurate studies of stellar populations. To demonstrate the applicability of our FPCs, we use them to infer stellar parameters and abundances of 28 giants in the open cluster M67. We employ Sequential Neural Likelihood, a simulation-based Bayesian inference method that learns likelihood functions using neural density estimators, to incorporate non-Gaussian effects in spectral likelihoods. By hierarchically combining the inferred abundances, we limit the spread of the following elements in M67: $\mathrm{Fe} \lesssim 0.02$ dex; $\mathrm{C} \lesssim 0.03$ dex; $\mathrm{O}, \mathrm{Mg}, \mathrm{Si}, \mathrm{Ni} \lesssim 0.04$ dex; $\mathrm{Ca} \lesssim 0.05$ dex; $\mathrm{N}, \mathrm{Al} \lesssim 0.07$ dex (at 68% confidence). Our constraints suggest a lack of self-pollution by core-collapse supernovae in M67, which has promising implications for the future of chemical tagging to understand the star formation history and dynamical evolution of the Milky Way.

We present non-perturbative numerical relativity simulations of slowly contracting spacetimes in which the scalar field driving slow contraction is coupled to a second scalar field through an exponential non-linear sigma model-type kinetic interaction. These models are important because they can generate a nearly scale-invariant spectrum of super-Hubble density fluctuations fully consistent with cosmic microwave background observations. We show that the non-linear evolution rapidly approaches a homogeneous, isotropic and flat Friedmann- Robertson-Walker (FRW) geometry for a wide range of inhomogeneous and anisotropic initial conditions. Ultimately, we find, the kinetic coupling causes the evolution to deflect away from flat FRW and towards a novel Kasner-like stationary point, but in general this occurs on time scales that are too long to be observationally relevant.

Transforming canonical scalars to the Einstein frame can give a multi-field generalization of pole inflation (namely, a scalar with a divergent kinetic term) at vanishing field-dependent Planck mass. However, to obtain an attractor, the scalar potential must obey certain non-generic conditions. These are automatically satisfied in Quantum Field Theories with dimension-less couplings. The resulting models of pole inflation have special inflationary predictions determined by the full RG running of couplings. Acceptable predictions for the tensor/scalar ratio arise for perturbative but moderately large couplings, so we explore the possible QFT runnings: to confinement, to an IR fixed point, and to a UV fixed point.

Axion production from astrophysical bodies is a topic in continuous development, because of theoretical progress in the estimate of stellar emission rates and, especially, because of improved stellar observations. We carry out a comprehensive analysis of the most informative astrophysics data, revisiting the bounds on axion couplings to photons, nucleons and electrons, and reassessing the significance of various hints of anomalous stellar energy losses. We confront the performance of various theoretical constructions in accounting for these hints, while complying with the observational limits on axion couplings. We identify the most favorable models, and the regions in the mass/couplings parameter space which are preferred by the global fit. Finally, we scrutinize the discovery potential for such models at upcoming helioscopes, namely IAXO and its scaled versions.

As first noted by Robert Wagoner in the nineteen-seventies, if a scalar field is nonminimally coupled to the Ricci scalar and propagates at subluminal speeds, then there exists the possibility of scalar Cherenkov radiation from a moving particle. The mere observation of high-energy cosmic rays could in principle rule out the existence of such scalar fields since any particle moving faster than scalar perturbations would lose energy in the form of scalar waves until it moves slower than those. We compute in detail the energy loss to scalar waves and find that it scales with the square of the ultra-violet (UV) cutoff frequency of the effective field theory (EFT) of gravity. For dark-energy-motivated EFTs, the UV cutoff can be low, in which case that energy loss could always be negligible. In contrast, if viewed as a covariant theory valid at all scales or as an EFT valid at higher energies, perhaps even all the way up to the Planck scale, as may be the case if motivated by quantum-gravity perspectives, then the energy loss to scalar waves may diverge or become dramatically large. In this case, high-energy cosmic rays of extragalactic origin stringently constrain any conformally coupled scalar fields with non-canonical kinetic terms.

Under very general assumptions on the accretion flow geometry, images of a black hole illuminated by electromagnetic radiation display a sequence of photon rings (demagnified and rotated copies of the direct image) which asymptotically approach a purely theoretical critical curve - the outline of the black hole photon shell. To a distant observer, these images appear dominated by the direct emission, which forms a ring whose diameter is primarily determined by the effective radius of the emitting region. For that reason, connecting the image diameter seen by a distant observer to the properties of the underlying spacetime crucially relies on a calibration that necessarily depends on the assumed astrophysical source model. On the other hand, the diameter of the photon rings depends more on the detailed geometry of the spacetime than on the source structure. As such, a photon ring detection would allow for the spacetime metric to be probed in a less model-dependent way, enabling more robust tests of General Relativity (GR) and the Kerr hypothesis. Here we present the photon ring structure of several spherically symmetric black hole spacetimes and perform comparisons with the Schwarzschild/Kerr case. We offer our perspective on future tests of the spacetime metric with photon rings, discussing challenges and opportunities involved.