Papers for Friday, Oct 27 2023

We propose a universal approximation of the equation of state of superdense matter in neutron star (NS) interiors. It contains only two parameters, the pressure and the density at the center of the maximally massive neutron star. We demonstrate the validity of this approximation for a wide range of different types of equations of state, including both baryonic and hybrid models. Combined with recently discovered correlations of internal (density, pressure, and speed of sound at the center) and external (mass, radius) properties of a maximally massive neutron star, this approximation turns out to be an effective tool for determining the equation of state of superdense matter using astrophysical observations.

Accurate position and posture measurements of the freely-falling test mass are crucial for the success of spaceborne gravitational wave detection missions. This paper presents a novel laboratory-developed test mass motion readout that utilizes quadrant photodetectors to measure the translation and tilt of a test mass. Departing from conventional methods like Zeeman effect or AOM frequency shift modulation, the readout system employs the phase locking of two lasers to generate the dual-frequency heterodyne source. Notably, the out-of-loop sensitivity of the phase locking reaches below 30 pm/Hz1/2 within the frequency band of 1 mHz and 10 Hz. The system comprises three measurement interferometers and one reference interferometer, featuring a symmetric design that enables measurements of up to six degrees of freedom based on polarization-multiplexing and differential wavefront sensing. Ground-simulated experimental results demonstrate that the proposed system has achieved a measurement sensitivity of 4 pm/Hz1/2 and 2 nrad/Hz1/2 at 1 Hz, a resolution of 5 nm and 0.1 urad, a range of 200 um and 600 urad, respectively. These findings showcase the system's potential as an alternative method for precisely monitoring the motion of test masses in spaceborne gravitational wave detection missions and other applications requiring accurate positioning and multi-degrees-of-freedom sensing.

The origin of obscuration in Active Galactic Nuclei (AGN) is still an open debate. In particular, it is unclear what drives the relative contributions to the line-of-sight column densities from galaxy-scale and torus-linked obscuration. The latter source is expected to play a significant role in Unification Models, while the former is thought to be relevant in both Unification and Evolutionary Models. In this work, we make use of a combination of cosmological semi-analytic models and semi-empirical prescriptions for the properties of galaxies and AGN, to study AGN obscuration. We consider a detailed object-by-object modelling of AGN evolution, including different AGN light curves (LCs), gas density profiles, and also AGN feedback-induced gas cavities. Irrespective of our assumptions on specific AGN LC or galaxy gas fractions, we find that, on the strict assumption of an exponential profile for the gas component, galaxy-scale obscuration alone can hardly reproduce the fraction of $\log (N_{\rm H}/$cm$^{-2}) \geq 24$ sources at least at $z\lesssim3$. This requires an additional torus component with a thickness that decreases with luminosity to match the data. The torus should be present in all evolutionary stages of a visible AGN to be effective, although galaxy-scale gas obscuration may be sufficient to reproduce the obscured fraction with $22<\log (N_{\rm H}/$cm$^{-2})<24$ (Compton-thin, CTN) if we assume extremely compact gas disc components. The claimed drop of CTN fractions with increasing luminosity does not appear to be a consequence of AGN feedback, but rather of gas reservoirs becoming more compact with decreasing stellar mass.

We present some of the salient aspects of the scientific motivation for high resolution soft X-ray spectroscopy of early-type stars with the Line Emission Mapper X-ray Probe. The major strength of {\it LEM} for hot star physics is its large effective area, aided by the inherent energy resolution of its microcalorimeter that readily achieves resolving powers of 1000 and obviates the need for relatively inefficient dispersive optical elements. This increased sensitivity enables much fainter and more distant high mass stars to be observed than are accessible with present-day facilities, greatly increasing the pool of potential targets. For brighter sources, the sensitivity opens up time domain studies, wherein sufficient signal can be garnered in short order and exposure times, probing source variations on ks timescales. We argue that these capabilities of {\it LEM} will yield breakthroughs in all types of hot star systems, from understanding single OB and WR star winds and how they vary with metallicity, to probing the shocks of colliding wind systems and the magnetically channeled winds of magnetic OB stars. {\it LEM} will also study the energetics of WR star bubbles and feedback from their powerful pre-SN stellar winds.

The project CAESAR (Comprehensive spAce wEather Studies for the ASPIS prototype Realization) is aimed to tackle all the relevant aspects of Space Weather (SWE) and realize the prototype of the scientific data centre for Space Weather of the Italian Space Agency (ASI) called ASPIS (ASI SPace Weather InfraStructure). This contribution is meant to bring attention upon the first steps in the development of the CAESAR prototype for ASPIS and will focus on the activities of the Node 2000 of CAESAR, the set of Work Packages dedicated to the technical design and implementation of the CAESAR ASPIS archive prototype. The product specifications of the intended resources that will form the archive, functional and system requirements gathered as first steps to seed the design of the prototype infrastructure, and evaluation of existing frameworks, tools and standards, will be presented as well as the status of the project in its initial stage.

Context. The study of protoplanetary disks is fundamental to understand their evolution and interaction with the surrounding environment, and to constrain planet formation mechanisms. Aims. We aim at characterising the young binary system HD 34700 A, which shows a wealth of structures. Methods. Taking advantage of the high-contrast imaging instruments SPHERE at the VLT, LMIRCam at the LBT, and of ALMA observations, we analyse this system at multiple wavelengths. We study the rings and spiral arms morphology and the scattering properties of the dust. We discuss the possible causes of all the observed features. Results. We detect for the first time, in the H${\alpha}$ band, a ring extending from $\sim$65 au to ${\sim}$120 au, inside the ring already known from recent studies. These two have different physical and geometrical properties. Based on the scattering properties, the outer ring may consist of grains of typical size $a_{out} > 4 {\mu}m$, while the inner ring of smaller grains ($a_{in} <= 0.4 {\mu m}$). Two extended logarithmic spiral arms stem from opposite sides of the disk. The outer ring appears as a spiral arm itself, with a variable radial distance from the centre and extended substructures. ALMA data confirm the presence of a millimetric dust substructure centred just outside the outer ring, and detect misaligned gas rotation patterns for HD 34700 A and B. Conclusions. The complexity of HD 34700 A, revealed by the variety of observed features, suggests the existence of one or more disk-shaping physical mechanisms. Possible scenarios, compatible with our findings, involve the presence inside the disk of a yet undetected planet of several Jupiter masses and the system interaction with the surroundings by means of gas cloudlet capture or flybys. Further observations with JWST/MIRI or ALMA (gas kinematics) could shed more light on these.

We report on the detection of diffuse radio emission with peculiar morphology in the central region of the galaxy cluster Abell 2657. The most striking feature identified in our 144 MHz LOFAR image is a bifurcated radio arc that extends for a projected size of 150-200 kpc. From the analysis of XMM-Newton data, we find clear evidence of gas sloshing in the cluster and a possible dip in X-ray surface brightness between the two radio arcs which deserves confirmation. Interestingly, the synchrotron emission of the bifurcated radio arc is stretched along the sloshing spiral. We compare our observational results with numerical simulations of non-thermal components interacting with gas motions. We suggest that the detected emission may trace a radio bubble shredded by gas sloshing, where relativistic electrons and magnetic fields are expected to be stretched and stirred as a consequence of tangential flows induced by the spiralling gas motion. Lastly, we report on the presence of two thin (6-7 kpc in width) and parallel strands of radio emission embedded in the outer arc that are morphologically similar to the emerging population of non-thermal filaments observed in galaxy clusters, radio galaxies, and the Galactic centre. While this work further demonstrates the complex interplay between thermal and non-thermal components in the intracluster medium, follow-up observations in radio and X-rays are required to firmly determine the origin of the features observed in Abell 2657.

The next generation gravitational wave (GW) detectors - Einstein Telescope (ET) and Cosmic Explorer (CE), will have distance horizons up to $\mathcal{O}(10)$ Gpc for detecting binary neutron star (BNS) mergers. This will make them ideal for triggering high-energy neutrino searches from BNS mergers at the next generation neutrino detectors, such as IceCube-Gen2. We calculate the distance limits as a function of the time window of neutrino analysis, up to which meaningful triggers from the GW detectors can be used to minimize backgrounds and collect a good sample of high-energy neutrino events at the neutrino detectors, using the sky localization capabilities of the GW detectors. We then discuss the prospects of the next generation detectors to work in synergy to facilitate coincident neutrino detections or to constrain the parameter space in the case of non-detection of neutrinos. We show that good localization of GW events, which can be achieved by multiple third generation GW detectors, is necessary to detect a GW-associated neutrino event or put a meaningful constraint ($\sim 3\sigma$ confidence level) on neutrino emission models. Such a model independent analysis can also help constrain physical models and hence provide insights into neutrino production mechanisms in binary neutron star mergers.

This chapter provides an overview of tidal disruption events, aiming to provide an overview of both the theoretical and the observational state of the field, with the overarching goal of introducing them as tools to indirectly observe massive black holes in the Universe. We start by introducing the relevant theoretical concepts, physical scales and timescales with an emphasis on the classical framework and how this has been (and continues to be) improved since the inception of the field. We then cover the current and future prospects of observing TDEs through a variety of messengers, including photons across the electromagnetic spectrum, as well as gravitational waves and neutrino particles. More recent advancements in the field, including repeating TDEs as well as TDEs by stellar-mass black holes, are also highlighted.

During common envelope evolution, an initially weak magnetic field may undergo amplification by interacting with spiral density waves and turbulence generated in the stellar envelope by the inspiralling companion. Using 3D magnetohydrodynamical simulations on adaptively refined spherical grids with excised central regions, we study the amplification of magnetic fields and their effect on the envelope structure, dynamics, and the orbital evolution of the binary during the post-dynamical inspiral phase. About $95\%$ of magnetic energy amplification arises from magnetic field stretching, folding, and winding due to differential rotation and turbulence while compression against magnetic pressure accounts for the remaining $\sim 5\%$. Magnetic energy production peaks at a scale of $3a_\text{b}$, where $a_\text{b}$ is the semimajor axis of central binary's orbit. Because the magnetic energy production declines at large radial scales, the conditions are not favorable for the formation of magnetically-collimated bipolar jet-like outflows unless they are generated on small scales near the individual cores, which we do not resolve. Magnetic fields have a negligible impact on binary orbit evolution, mean kinetic energy, and the disk-like morphology of angular momentum transport, but turbulent Maxwell stress can dominate Reynolds stress when accretion onto the central binary is allowed, leading to an $\alpha$-disk parameter of $\simeq 0.034$. Finally, we discover accretion streams arising from the stabilizing effect of the magnetic tension from the toroidal field about the orbital plane, which prevents overdensities from being destroyed by turbulence and enables them to accumulate mass and eventually migrate towards the binary.

The dispersed remnants of stellar nurseries, stellar associations provide unparalleled samples of coeval stars critical for studies of stellar and planetary formation and evolution. The Carina Stellar Association is one of the closest stellar associations to Earth, and yet measurements of its age have varied from 13 to 45 Myr. We aim to update the age of Carina using the Lithium Depletion Boundary method. We obtain new measurements of the Li 6708 Angstrom, absorption feature in likely members using optical spectra from the Goodman HTS on SOAR and NRES on LCO. We detect the depletion boundary at M_K ~= 6.8 (M5), which corresponds to an age of 41(+3,-5) Myr. The age is consistent within uncertainties across six different models, including those that account for magnetic fields and spots. We also estimate the age through analysis of the group's overall variability, and by comparing the association members' CMD to stellar evolutionary models using a Gaussian Mixture Model, recovering ages consistent with the LDB. The resulting age agrees with the older end of previous age measurements and is consistent with the lithium depletion age for the neighboring Tucana-Horologium Moving Group.

We present a sample of 34 normal SNe II detected with the Zwicky Transient Facility, with multi-band UV light-curves starting at $t \leq 4$ days after explosion, as well as X-ray detections and upper limits. We characterize the early UV-optical colors and provide prescriptions for empirical host-extinction corrections. We show that the $t > 2\,$days UV-optical colors and the blackbody evolution of the sample are consistent with the predictions of spherical phase shock-cooling (SC), independently of the presence of `flash ionization" features. We present a framework for fitting SC models which can reproduce the parameters of a set of multi-group simulations without a significant bias up to 20% in radius and velocity. Observations of about half of the SNe II in the sample are well-fit by models with breakout radii $<10^{14}\,$cm. The other half are typically more luminous, with observations from day 1 onward that are better fit by a model with a large $>10^{14}\,$cm breakout radius. However, these fits predict an early rise during the first day that is too slow. We suggest these large-breakout events are explosions of stars with an inflated envelope or a confined CSM with a steep density profile, at which breakout occurs. Using the X-ray data, we derive constraints on the extended ($\sim10^{15}$ cm) CSM density independent of spectral modeling, and find most SNe II progenitors lose $<10^{-4} M_{\odot}\, \rm yr^{-1}$ a few years before explosion. This provides independent evidence the CSM around many SNe II progenitors is confined. We show that the overall observed breakout radius distribution is skewed to higher radii due to a luminosity bias. We argue that the $66^{+11}_{-22}\%$ of red supergiants (RSG) explode as SNe II with breakout radii consistent with the observed distribution of field RSG, with a tail extending to large radii, likely due to the presence of CSM.

Short-period giant planets are frequently found to be solitary compared to other classes of exoplanets. Small inner companions to giant planets with $P \lesssim$ 15 days are known only in five compact systems: WASP-47, Kepler-730, WASP-132, TOI-1130, and TOI-2000. Here, we report the confirmation of TOI-5398, the youngest compact multi-planet system composed of a hot sub-Neptune (TOI-5398 c, $P_{\rm c}$ = 4.77271 days) orbiting interior to a short-period Saturn (TOI-5398 b, $P_{\rm b}$ = 10.590547 days) planet, both transiting around a 650 $\pm$ 150 Myr G-type star. As part of the GAPS Young Object project, we confirmed and characterised this compact system, measuring the radius and mass of both planets, thus constraining their bulk composition. Using multidimensional Gaussian processes, we simultaneously modelled stellar activity and planetary signals from TESS Sector 48 light curve and our HARPS-N radial velocity time series. We have confirmed the planetary nature of both planets, TOI-5398 b and TOI-5398 c, alongside a precise estimation of stellar parameters. Through the use of astrometric, photometric, and spectroscopic observations, our findings indicate that TOI-5398 is a young, active G dwarf star (650 $\pm$ 150 Myr), with a rotational period of $P_{\rm rot}$ = 7.34 days. The transit photometry and radial velocity measurements enabled us to measure both the radius and mass of planets b, $R_b = 10.30\pm0.40 R_{\oplus}$, $M_b = 58.7\pm5.7 M_{\oplus}$, and c, $R_c = 3.52 \pm 0.19 R_{\oplus}$, $M_c = 11.8\pm4.8 M_{\oplus}$. TESS observed TOI-5398 during sector 48 and no further observations are planned in the current Extended Mission, making our ground-based light curves crucial for ephemeris improvement. With a Transmission Spectroscopy Metric value of around 300, TOI-5398 b is the most amenable warm giant (10 < $P$ < 100 days) for JWST atmospheric characterisation.

Sagittarius A* (Sgr A*), the supermassive black hole at the heart of our galaxy, provides unique opportunities to study black hole accretion, jet formation, and gravitational physics. The rapid structural changes in Sgr A*'s emission pose a significant challenge for traditional imaging techniques. We present dynamic reconstructions of Sgr A* using Event Horizon Telescope (EHT) data from April 6th and 7th, 2017, analyzed with a one-minute temporal resolution with the Resolve framework. This Bayesian approach employs adaptive Gaussian Processes and Variational Inference for data-driven self-regularization. Our results not only fully confirm the initial findings by the EHT Collaboration for a time-averaged source but also reveal intricate details about the temporal dynamics within the black hole environment. We find an intriguing dynamic feature on April 6th that propagates in a clock-wise direction. Geometric modelling with ray-tracing, although not fully conclusive, indicates compatibility with high-inclination configurations of about $\theta_o = 160^\circ$, as seen in other studies.

Understanding the connection between the properties of black holes (BHs) and their progenitors is interesting in many branches of astrophysics. Discovering BHs in detached orbits with luminous companions (LCs) promises to help create this map since the LC and BH progenitor are expected to have the same metallicity and formation time. We explore the possibility of detecting BH-LC binaries in detached orbits using photometric variations of the LC flux, induced by tidal ellipsoidal variation, relativistic beaming, and self-lensing. We create realistic present-day populations of detached BH-LC binaries in the Milky Way (MW) using binary population synthesis where we adopt observationally motivated initial stellar and binary properties, star formation history and present-day distribution of these sources in the MW based on detailed cosmological simulations. We test detectability of these sources via photometric variability by Gaia and TESS missions by incorporating their respective detailed detection biases as well as interstellar extinction. We find that Gaia (TESS) is expected to resolve ~700-1500 (~100-400) detached BH-LC binaries depending on the photometric precision and details of supernova physics. We find that ~369 BH-LC binaries would be common both in Gaia and TESS. Moreover, between ~80-270 (~70-290) of these BH-LC binaries can be further characterised using Gaia's radial velocity (astrometry) measurements.

We present new ALMA CO(2-1) observations tracing $2.2 \times 10^{10}$ M$_{\odot}$ of molecular gas in Abell 2390's brightest cluster galaxy, where half the gas is located in a one-sided plume extending 15 kpc out from the galaxy centre. This molecular gas has a smooth and positive velocity gradient, and is receding 250 km/s faster at its farthest point than at the galaxy centre. To constrain the plume's origin, we analyse our new observations alongside existing X-ray, optical and radio data. We consider the possibility that the plume is jet-driven with lifting aided by jet inflated X-ray bubbles. Alternatively, it may have formed following a gravitational disturbance. In this case, the plume may either be a trail of gas stripped from the main galaxy by ram pressure, or more recently cooled and infalling gas. The galaxy's star formation and gas cooling rate suggest the lifespan of its molecular gas may be low compared with the plume's age -- which would favour a recently cooled plume. Molecular gas in close proximity to the active galactic nucleus is also indicated by 250 km/s wide CO(2-1) absorption against the radio core, as well as previously detected CO(1-0) and HI absorption. This absorption is optically thick and has a line of sight velocity towards the galaxy centre of 200 km/s. We discuss simple models to explain its origin.

The existence of merging black hole-neutron star (BHNS) binaries has been ascertained through the observation of their gravitational wave (GW) signals. However, to date, no definitive electromagnetic (EM) emission has been confidently associated with these mergers. Such an association could help unravel crucial information on these systems, for example, their BH spin distribution, the equation of state (EoS) of NS and the rate of heavy element production. We model the multi-messenger (MM) emission from BHNS mergers detectable during the fourth (O4) and fifth (O5) observing runs of the LIGO-Virgo-KAGRA GW detector network, in order to provide detailed predictions that can help enhance the effectiveness of observational efforts and extract the highest possible scientific information from such remarkable events. Our methodology is based on a population synthesis-approach, which includes the modelling of the signal-to-noise ratio of the GW signal in the detectors, the GW-inferred sky localization of the source, the kilonova (KN) optical and near-infrared light curves, the relativistic jet gamma-ray burst (GRB) prompt emission peak photon flux, and the GRB afterglow light curves in the radio, optical and X-ray bands. The resulting prospects for BHNS MM detections during O4 are not promising, with a GW detection rate of $15.0^{+15.4}_{-8.8}$ yr$^{-1}$, but joint MM rates of $\sim 10^{-1}$ yr$^{-1}$ for the KN and $\sim 10^{-2}$ yr$^{-1}$ for the jet-related emission. In O5 we find an overall increase in expected detection rates by around an order of magnitude, owing to both the enhanced sensitivity of the GW detector network, and the coming online of future EM facilities. Finally, we discuss direct searches for the GRB radio afterglow with large-field-of-view instruments as a new possible follow-up strategy in the context of ever-dimming prospects for KN detection.

We present SPICE, a new suite of RHD cosmological simulations targeting the epoch of reionisation. The goal of these simulations is to systematically probe a variety of stellar feedback models, including "bursty" and "smooth" forms of supernova energy injection, as well as poorly-explored scenarios such as hypernova explosions and radiation pressure. Subtle differences in the behaviour of supernova feedback drive profound differences in reionisation histories, with burstier forms of feedback causing earlier reionisation. We also find that some global galaxy properties, such as the dust-attenuated luminosity functions and star formation main sequence, remain degenerate between models. Stellar feedback and its strength determine the morphological mix of galaxies emerging by z = 5 and that the reionisation history is inextricably connected to intrinsic properties such as galaxy kinematics and morphology. While star-forming, massive disks are prevalent if supernova feedback is "smooth", "bursty" feedback preferentially generates dispersion-dominated systems. Different modes of feedback produce different strengths of outflows, altering the ISM/CGM in different ways, and in turn strongly affecting the escape of LyC photons. We establish a correlation between galaxy morphology and LyC escape fraction, revealing that dispersion-dominated systems have escape fractions 10-50 times higher than their rotation-dominated counterparts at all redshifts. Dispersion-dominated systems should thus preferentially generate large HII regions as compared to their rotation-dominated counterparts. Since dispersion-dominated systems are more prevalent if stellar feedback is more explosive, reionisation occurs earlier in our simulation with burstier feedback. Statistical samples of post-reionisation galaxy morphologies probed with JWST, ALMA and MUSE can constrain stellar feedback and models of cosmic reionisation.

Despite solid theoretical and observational grounds for the pairing of supermassive black holes (SMBHs) after galaxy mergers, definitive evidence for the existence of close (sub-parsec) separation SMBH binaries (SMBHBs) approaching merger is yet to be found. This chapter reviews techniques aimed at discovering such SMBHBs in galactic nuclei. We motivate the search with a brief overview of SMBHB formation and evolution, and the gaps in our present-day theoretical understanding. We then present existing observational evidence for SMBHBs and discuss ongoing efforts to provide definitive evidence for a population at sub-parsec orbital separations, where many of the aforementioned theoretical gaps lie. We conclude with future prospects for discovery with electromagnetic (primarily time-domain) surveys, high-resolution imaging experiments, and low-frequency gravitational-wave detectors.

This text will appear as Section II of Chapter 5 of the book "Black Holes in the Era of Gravitational-Wave Astronomy". As a stand alone text, it serves as a brief overview of astrophysics and gravitational wave radiation of extreme mass ratio inspirals, or EMRIs. Topics covered consist of: dynamical and gas-assisted formation channels, basics of EMRI dynamics and gravitational radiation, and science potential for both astrophysics and fundamental physics.

Radiation from stars and AGN plays an important role in galaxy formation and evolution, and profoundly transforms the IGM, CGM & ISM. On-the-fly RT has started being incorporated in cosmological simulations, but the complex, evolving radiation spectra are often crudely approximated with a small number of broad bands with piece-wise constant intensity and a fixed photo-ionisation cross-section. Such a treatment is unable to capture the changes to the spectrum as light is absorbed while it propagates through a medium with non-zero opacity. This can lead to large errors in photo-ionisation and heating rates. We present a novel approach of discretising the radiation field in narrow bands, located at the edges of the typically used bands, in order to capture the power-law slope of the radiation field. In combination with power-law approximations for the photo-ionisation cross-sections, this model allows us to self-consistently combine radiation from sources with different spectra and accurately follow the ionisation states of primordial and metal species through time. The method is implemented in Gasoline2 in connection with Trevr2. We compare our new piece-wise power-law reconstruction to the piece-wise constant method in calculating the primordial chemistry photo-ionisation and heating rates under an evolving UVB and stellar spectrum, and find that our method reduces errors significantly, up to two orders of magnitude in the case of HeII ionisation. We apply our new spectral reconstruction method in RT post-processing of a cosmological zoom-in simulation, including radiation from stars and a live UVB, and find a significant increase in total neutral hydrogen mass in the ISM and the CGM due to shielding of the UVB and a low escape fraction of the stellar radiation. This demonstrates the importance of RT and an accurate spectral approximation in simulating the CGM-galaxy ecosystem.

$\phi$CDM models provide an alternative to the standard $\Lambda$CDM paradigm, while being physically better motivated. These models lead to a time-dependent speed of sound for dark energy that is difficult to replicate by $w$CDM parametrizations. We review the most up-to-date status of observational evidence for the $\phi$CDM models in this paper. We start with an overview of the motivation behind these classes of models, the basic mathematical formalism, and the different classes of models. We then present a compilation of recent results of applying different observational probes to constraining $\phi$CDM model parameters. Over the last twenty years, the precision of observational data has increased immensely, leading to ever tighter constraints. A combination of the recent measurements favors the spatially flat $\Lambda$CDM model, but a large class of $\phi$CDM models is still not ruled out.

James Webb Space Telescope NIRCam images have revealed 443 globular cluster (GC) candidates around the $z=0.0513$ elliptical galaxy VV 191a. NIRCam broadband observations are made at 0.9-4.5 $\mu$m using filters F090W, F150W, F356W, and F444W. Using photometry, the data is analyzed to present color-magnitude diagrams (CMDs) that suggest a fairly uniform population of GCs. Color histograms show a unimodal color distribution that is well fit by a single Gaussian, using color to primarily trace the metallicity. The findings show the sample's globular cluster luminosity function (GCLF) does not reach the turnover value and is, therefore, more luminous than what is typically expected, with an absolute AB magnitude, $M_{F090W} = -8.70$ mag, reaching within nearly one magnitude of the classical turnover value. We attribute this to the completeness in the sample. Models show that the mass estimate of the GCs detected tends to be more massive, reaching upward of $\simeq 10^7 M_{\odot}$. However, the results show that current GC models do not quite align with the data. We find that the models appear to be bluer than the JWST data in the reddest (F356W-F444W) filters and redder than the data in the bluest (F090W-F150W) filters and may need to be revised to improve the modeling of near-IR colors of old, metal-poor stellar populations.

The bright millisecond-duration radio burst from the Galactic magnetar SGR 1935+2154 in 2020 April was a landmark event, demonstrating that at least some fast radio burst (FRB) sources could be magnetars. The two-component burst was temporally coincident with peaks observed within a contemporaneous short X-ray burst envelope, marking the first instance where FRB-like bursts were observed to coincide with X-ray counterparts. In this study, we detail five new radio burst detections from SGR 1935+2154, observed by the CHIME/FRB instrument between October 2020 and December 2022. We develop a fast and efficient Bayesian inference pipeline that incorporates state-of-the-art Markov chain Monte Carlo techniques and use it to model the intensity data of these bursts under a flexible burst model. We revisit the 2020 April burst and corroborate that both the radio sub-components lead the corresponding peaks in their high-energy counterparts. For a burst observed in 2022 October, we find that our estimated radio pulse arrival time is contemporaneous with a short X-ray burst detected by GECAM and HEBS, and Konus-Wind and is consistent with the arrival time of a radio burst detected by GBT. We present flux and fluence estimates for all five bursts, employing an improved estimator for bursts detected in the side-lobes. We also present upper limits on radio emission for X-ray emission sources which were within CHIME/FRB's field-of-view at trigger time. Finally, we present our exposure and sensitivity analysis and estimate the Poisson rate for FRB-like events from SGR 1935+2154 to be $0.005^{+0.082}_{-0.004}$ events/day above a fluence of $10~\mathrm{kJy~ms}$ during the interval from 28 August 2018 to 1 December 2022, although we note this was measured during a time of great X-ray activity from the source.

Sagittarius A$^\ast$ is a compact radio source at the center of the Milky Way that has not conclusively shown evidence for the presence of a relativistic jet. Nevertheless, indirect methods at radio frequencies do indicate consistent outflow signatures. Brinkerink et al. (2015) found temporal shifts between frequency bands, called time-lags, which are associated with flares and/or outflows of the accretion system. It is possible to gain information on the emission and potential outflow mechanics by interpreting these time-lags. By means of combined general-relativistic magnetrohydrodynamical and radiative transfer modeling, we study the origin of the time-lags for magnetically arrested disc models at three black hole spins ($a_\ast$ = 0.9375, 0, -0.9375). The study also includes a targeted `slow light' study for one of the best-fitting `fast light' windows. We were able to recover the time-lags found by Brinkerink et al. (2015) in various windows of our simulated lightcurves. The theoretical interpretation of these most-promising time-lag windows is threefold; i) a magnetic flux eruption perturbs the jet-disc boundary and creates a flux tube, ii) the flux tube orbits and creates a clear emission feature, and iii) the flux tube interacts with the jet-disc boundary. The best-fitting windows have an intermediate (i=30$^\circ$/50$^\circ$) inclination and zero-BH-spin. The targeted `slow light' study did not yield better-fitting time-lag results, which indicates that the fast vs. slow light paradign is often not intuitively understood and is likely influential in timing-sensitive studies.

There are X-ray pulsating sources that are thought to be accretion disks around neutron stars. Such disks deserve a detailed analysis. In particular, the dipole magnetic field of the central star may penetrate the disk, which, in turn, leads to the appearance of an induced magnetic field inside the disk due to the frozen-in condition. The growth of the induced field can be limited by the turbulent diffusion of the field. In the present work, I calculate the induced field in this case. The problem is reduced to the induction equation with turbulent diffusion taken into account. I have found the analytical solution of this equation, and radial and vertical structures of the field were found simultaneously. The radial structure is close to the earlier predicted dependence on the difference in angular velocities between the magnetosphere and disk: $b \propto \Omega_{\rm s} - \Omega_{\rm k}$, while the vertical structure is close to a linear dependence of an induced field on the altitude above the equator: $b \propto z$. The possibility of the existence of non-stationary quasi-periodic components of an induced field is discussed.

Protostellar jets and outflows are signposts of active star formation. In H II regions, molecular tracers like CO only reveal embedded portions of the outflow. Outside the natal cloud, outflows are dissociated, ionized, and eventually completely ablated, leaving behind only the high-density jet core. Before this process is complete, there should be a phase where the outflow is partially molecular and partially ionized. In this paper, we capture the HH 900 outflow while this process is in action. New observations from the ERIS/SPIFFIER near-IR integral field unit (IFU) spectrograph using the K-middle filter ($\lambda$=2.06-2.34 $\mu$m) reveal H$_2$ emission from the dissociating outflow and Br-$\gamma$ tracing its ionized skin. Both lines trace the wide-angle outflow morphology but H$_2$ only extends $\sim$5000 au into the H II region while Br-$\gamma$ extends the full length of the outflow ($\sim$12,650 au), indicating rapid dissociation of the molecules. H$_2$ has higher velocities further from the driving source, consistent with a jet-driven outflow. Diagnostic line ratios indicate that photoexcitation, not just shocks, contributes to the excitation in the outflow. We argue that HH 900 is the first clear example of an evaporating molecular outflow and predict that a large column of neutral material that may be detectable with ALMA accompanies the dissociating molecules. Results from this study will help guide the interpretation of near-IR images of externally irradiated jets and outflows such as those obtained with the James Webb Space Telescope (JWST) in high-mass star-forming regions where these conditions may be common.

Three principal concepts regarding lunar formation have been examined: the accretion hypothesis, the mega-impact theory, and the multi-impact model. The multi-impact model amalgamates the salient facets of the mega-impact theory and the accretion hypothesis. As per this model, fragments of the terrestrial crust are ejected into space during collisions with numerous planetesimals (proto-asteroids) with diameters around 10-100 kilometers. This ejecta interacts with the accretion disk, augmenting its mass. Different models of lunar formation yield varied conclusions regarding the quantity of lunar water, its subsurface distribution, and isotopic composition. Geomorphological structures in the lunar polar regions (smoothed craters, landslides, regular patterns) suggest the presence of a substantial permafrost layer with an approximate thickness of a kilometer.

The temporal analysis of stellar activity evolution is usually dominated by a complex trade-off between model complexity and interpretability, often by neglecting the non-stationary nature of the process. Recent studies appear to indicate that the presence of multiple coexisting cycles in a single star is more common than previously thought. The correct identification of physically meaningful cyclic components in spectroscopic time series is therefore a crucial task, which cannot overlook local behaviors. Here we propose a decomposition technique which adaptively recovers amplitude- and frequency-varying components. We present our results for the solar activity as measured both by the sunspot number and the $K$-line emission index, and we consistently recover the Schwabe and Gleissberg cycles as well as the Gnevyshev-Ohl pattern probably related to the Hale cycle. We also recover the known 8-year cycle for 61 Cygni A, in addition to evidence of a three-cycles long pattern reminiscent of the Gnevyshev-Ohl rule. This is particularly interesting as we cannot discard the possibility of a relationship between the measured field polarity reversals and this Hale-like periodicity.

We report on the chemo-dynamical analysis of SPLUS J142445.34-254247.1, an extremely metal-poor halo star enhanced in elements formed by the rapid neutron-capture process. This star was first selected as a metal-poor candidate from its narrow-band S-PLUS photometry and followed up spectroscopically in medium-resolution with Gemini South/GMOS, which confirmed its low-metallicity status. High-resolution spectroscopy was gathered with GHOST at Gemini South, allowing for the determination of chemical abundances for 36 elements, from carbon to thorium. At [Fe/H]=-3.39, SPLUS J1424-2542 is one of the lowest metallicity stars with measured Th and has the highest logeps(Th/Eu) observed to date, making it part of the "actinide-boost" category of r-process enhanced stars. The analysis presented here suggests that the gas cloud from which SPLUS J1424-2542 was formed must have been enriched by at least two progenitor populations. The light-element (Z<=30) abundance pattern is consistent with the yields from a supernova explosion of metal-free stars with 11.3-13.4 Msun, and the heavy-element (Z>=38) abundance pattern can be reproduced by the yields from a neutron star merger (1.66Msun and 1.27Msun) event. A kinematical analysis also reveals that SPLUS J1424-2542 is a low-mass, old halo star with a likely in-situ origin, not associated with any known early merger events in the Milky Way.

Using the ONEDFEL code we perform Free Electron Laser simulations in the astrophysically important guide-field dominated regime. For wigglers' (Alfven waves) wavelengths of tens of meters and beam Lorentz factor $\sim 10^3$, the resulting coherently emitted waves are in the centimeter range. Our simulations show a growth of the wave intensity over fourteen orders of magnitude, over the astrophysically relevant scale of $\sim$ few kilometers. The signal grows from noise (unseeded). The resulting spectrum shows fine spectral sub-structures, reminiscent of the ones observed in Fast Radio Bursts (FRBs).

AU Mic is an active 24 Myr pre-main sequence M dwarf in the stellar neighborhood (d$=$9.7 pc) with a rotation period of 4.86 days. The two transiting planets orbiting AU Mic, AU Mic b and c, are warm sub-Neptunes on 8.5 and 18.9 day periods and are targets of interest for atmospheric observations of young planets. Here we study AU Mic's unocculted starspots using ground-based photometry and spectra in order to complement current and future transmission spectroscopy of its planets. We gathered multi-color LCO 0.4m SBIG photometry to study the star's rotational modulations and LCO NRES high-resolution spectra to measure the different spectral components within the integrated spectrum of the star, parameterized by 3 spectral components and their coverage fractions. We find AU Mic's surface has at least 2 spectral components, a $4000\pm15$ K ambient photosphere with cool spots that have a temperature of $3000\pm70$ K and cover $39\pm4\%$ percent of the surface, increasing and decreasing by 5$\%$ from the average throughout a rotation. We also detect a third flux component with a filling factor less than 0.5$\%$ and a largely uncertain temperature that we attribute to flare flux not entirely omitted in the time-averaged spectra. We include measurements of spot temperature and coverage fraction from both 2- and 3- temperature models, which we find agree with each other strongly. Our expanded use of various techniques to study starspots will help us better understand this system and may have applications for interpreting the transmission spectra for exoplanets transiting stars of a wide range of activity levels.

Magnetic fields are ubiquitous in the universe and are thought to play an important role in various astrophysical processes. Polarization of thermal dust emission from dust grains aligned with the magnetic field is widely used to measure the two-dimensional magnetic field projected onto the plane of the sky (POS), but the component along the line of sight (LOS) is not yet reliably constrained with dust polarization. Here, we introduce a new method to infer three-dimensional (3D) magnetic fields using thermal dust polarization and grain alignment physics. We first develop a physical model of thermal dust polarization using the modern grain alignment theory based on the magnetically enhanced radiative torque (MRAT) alignment theory. We then test this model with synthetic observations of magnetohydrodynamic (MHD) simulations of a filamentary cloud with our updated POLARIS code. Combining the tested physical polarization model with synthetic polarization, we show that the B-field inclination angle can be accurately constrained by the polarization degree from synthetic observations. Compared to the true 3D magnetic fields, our method with grain alignment is more accurate than the previous methods that assume uniform grain alignment. This new technique paves the way for tracing 3D B-fields using thermal dust polarization and grain alignment theory and for constraining dust properties and grain alignment physics.

Just 10 recurrent novae (RNe) - which erupt repeatedly on timescales shorter than one century - are known in our Galaxy. The most extreme RN known (located in the Andromeda galaxy), M31N 2008-12a, undergoes a nova eruption every year, and is surrounded by a vast nova "super-remnant", 134 pc in extent. Simulations predict that all RNe should be surrounded by similar vast shells, but previous searches have failed to detect them. KT Eri has recently been suggested to be a RN, and we have used the Condor Array Telescope to image its environs through multiple narrowband filters. We report the existence of a large ($\sim$ 50 pc diameter), H$\,\alpha$-bright shell centered on KT Eri, exactly as predicted. This strongly supports the claim that KT Eri is the 11th Galactic recurrent nova, and only the second nova known to be surrounded by a super-remnant. SALT spectra of the super-remnant demonstrate that its velocity width is consistent with that of M31-2008-12a.

White dwarfs that have accreted planetary materials provide a powerful tool to probe the interiors and formation of exoplanets. In particular, the high Fe/Si ratio of some white dwarf pollutants suggests that they are fragments of bodies that were heated enough to undergo large-scale melting and iron core formation. In the solar system, this phenomenon is associated with bodies that formed early and so had short-lived radionuclides to power their melting, and/or grew large. However, if the planetary bodies accreted by white dwarfs formed during the (pre)-main sequence lifetime of the host star, they will have potentially been exposed to a second era of heating during the star's giant branches. This work aims to quantify the effect of stellar irradiation during the giant branches on planetary bodies by coupling stellar evolution to thermal and orbital evolution of planetesimals. We find that large-scale melting, sufficient to form an iron core, can be induced by stellar irradiation, but only in close-in small bodies: planetesimals with radii $\lesssim$ 30 km originally within $\sim$ 2 AU orbiting a 1$-$3$\,M_{\odot}$ host star with solar metallicity. Most of the observed white dwarf pollutants are too massive to be explained by the accretion of these small planetesimals that are melted during the giant branches. Therefore, we conclude that those white dwarfs that have accreted large masses of materials with enhanced or reduced Fe/Si remain an indicator of planetesimal's differentiation shortly after formation, potentially linked to radiogenic heating.

Dwarf galaxies are important tracers of small-scale cosmological structure, yet much of our knowledge about these systems comes from the limited sample of dwarf galaxies within the Local Group. To make a comprehensive inventory of dwarf populations in the local Universe, we require effective methods for deriving distance estimates for large numbers of faint, low surface brightness objects. Here we test the surface brightness fluctuation (SBF) method, traditionally applied to brighter early-type galaxies, on a sample of 20 nearby dwarf galaxies detected in the COSMOS field. These objects are partially resolved in HST ACS images, and have confirmed redshift distances in the range 17-130 Mpc. We discuss the many model choices required in applying the SBF method, and explore how these affect the final distance estimates. Amongst other variations on the method, when applying the SBF method, we alter the standard equation to include a term accounting for the power spectrum of the background, greatly improving our results. For the most robust modelling choices, we find a roughly Gaussian SBF signal that correlates linearly with distance out to distances of 50-100 Mpc, but with only a fraction of the power expected. At larger distances, there is excess power relative to that predicted, probably from undetected point sources. Overall, obtaining accurate SBF distances to faint, irregular galaxies remains challenging, but may yet prove possible with the inclusion of more information about galaxy properties and point source populations, and the use of more advanced techniques.

Fullerenes, including \ce{C60} and \ce{C70}, have been detected in various astronomical environments. Understanding how their structures evolve over time is essential for gaining insights into their life cycle and making further observations. To address this, we conducted reactive molecular dynamics simulations to investigate the evolution of fullerenes in the circumstellar envelopes surrounding carbon-rich asymptotic giant branch stars. Our simulations employed a bottom-up chemistry scheme, wherein fullerenes grow by absorbing and condensing small carbon-based molecules. The results revealed the formation of different structures through heterogeneous reactions based on hydrogen concentration, leading to the emergence of onion-like nanostructures or single-layer fullerenes. To examine the impact of these structural changes on the infrared emission characteristics of fullerenes, we performed quantum chemical calculations. The results indicate that as fullerenes grow larger, additional emission features are introduced in the infrared spectrum. Moreover, two-layered fullerenes show noticeable blue-shift or weakening effects on the bands associated with out-of-plane vibration modes.

The two point correlation function (2PCF) is a powerful statistical tool to measure galaxy clustering. Although 2PCF has also been used to study the clustering of stars on parsec and sub-parsec scales, its physical implication is not clear on such non-linear scales. In this study, we use the Illustris-TNG50 simulation to study the connection between the 2PCF signals of accreted halo stars and the assembly histories of Milky Way-mass galaxies. We find, in general, the 2PCF signal increases with the increase in galactocentric radii, $r$, and with the decrease in the pair separations. Galaxies which assemble late on average have stronger 2PCF signals. With $z_{1/4}$, $z_{1/2}$ and $z_{3/4}$ defined as the redshifts when galaxies accreted one-fourth, half and three-fourths of their ex-situ stellar mass at today, we find all of them show the strongest correlations with the 2PCF signals at $r\sim0.2R_{200}$. $z_{3/4}$ shows the strongest correlations at all radii than those of $z_{1/4}$ or $z_{1/2}$, as later accreted stars preserve better clusterings. However, the correlations between the 2PCF signals at different radii and the galaxy formation times all have large scatters. The 2PCFs in velocity space show weaker correlations with the galaxy formation times within $0.38R_{200}$ than real space 2PCFs, and the scatter is considerably large. Both the real and velocity space 2PCFs correlate with the assembly histories of the host dark matter halos as well. Within $0.38R_{200}$, the real space 2PCF shows stronger correlations with the galaxy formation histories than with the halo formation histories, while the velocity space 2PCFs do not show large differences. We conclude that it is difficult to use 2PCF alone to precisely predict the formation times or assembly histories of galaxies.

We propose a new generative model of projected cosmic mass density maps inferred from weak gravitational lensing observations of distant galaxies (weak lensing mass maps). We construct the model based on a neural style transfer so that it can transform Gaussian weak lensing mass maps into deeply non-Gaussian counterparts as predicted in ray-tracing lensing simulations. We develop an unpaired image-to-image translation method with Cycle-Consistent Generative Adversarial Networks (Cycle GAN), which learn efficient mapping from an input domain to a target domain. Our model is designed to enjoy important advantages; it is trainable with no need for paired simulation data, flexible to make the input domain visually meaningful, and expandable to rapidly-produce a map with a larger sky coverage than training data without additional learning. Using 10,000 lensing simulations, we find that appropriate labeling of training data based on field variance requires the model to exhibit a desired diversity of various summary statistics for weak lensing mass maps. Compared with a popular log-normal model, our model improves in predicting the statistical natures of three-point correlations and local properties of rare high-density regions. We also demonstrate that our model enables us to produce a continuous map with a sky coverage of $\sim166\, \mathrm{deg}^2$ but similar non-Gaussian features to training data covering $\sim12\, \mathrm{deg}^2$ in a GPU minute. Hence, our model can be beneficial to massive productions of synthetic weak lensing mass maps, which is of great importance in future precise real-world analyses.

The Kessler syndrome refers to the escalating space debris from frequent space activities, threatening future space exploration. Addressing this issue is vital. Several AI models, including Convolutional Neural Networks (CNN), Kernel Principal Component Analysis (KPCA), and Model-Agnostic Meta-Learning (MAML), have been assessed with various data types. Earlier studies highlighted the combination of the YOLO object detector and a linear Kalman filter for object detection and tracking. Building on this, our project introduces CosmosDSR, a novel methodology combining YOLOv3 with an Unscented Kalman Filter for tracking satellites in sequential images, compared to a linear Kalman filter. Using the SPARK dataset from the University of Luxembourg for training and testing, the YOLOv3 precisely detected and classified all satellite categories (mAP=97.18%, F1=0.95) with few errors (TP=4163, FP=209, FN=237). Both CosmosDSR and the LKF tracked satellites accurately (UKF: MSE=2.83/RMSE=1.66, LKF: MSE=2.84/RMSE=1.66). Despite concerns of class imbalance and the absence of real images, the model shows promise. Future work should address these limitations, increase tracking sample size, and improve metrics. This research suggests the algorithm's potential in detecting and tracking satellites, paving the way for solutions to the Kessler syndrome.

We present a model-independent reconstruction of the early expansion and thermal histories of the universe, obtained from light element abundance measurements. The expansion history is tightly constrained around the onset of the Big Bang Nucleosynthesis (BBN). The temperature of photons is additionally constrained around the time of neutrino decoupling. Allowing for perturbations to the standard expansion rate, we find that the radiation energy density is constrained to within 15% of its $\Lambda$CDM value, and only 1% extra matter energy density is allowed around the epoch of BBN. We introduce a new and general analytic fitting formula for the temperature variation, which is flexible enough to reproduce the signal of large classes of beyond-CDM particle models that can alter the temperature through early-time energy injection. We present its constraints from BBN data and from the measurements of effective number of relativistic species and helium-4 abundance probed by the Cosmic Microwave Background radiation anisotropy. Our results provide clarity on the most fundamental properties of the early universe, reconstructed with minimal assumptions about the unknown physics that can occur at keV--MeV energy scales and can be mapped to broad classes of models of interest to cosmology.

In this study we estimate the stellar ages of LAMOST DR5 Red Giant Branch (RGB) stars based on the Gradient Boosting Decision Tree algorithm (GBDT). We used 2088 RGB stars extracted from the APOKASC-2 astero-seismological catalog as training data-set. After selecting the parameters highly correlated with age using GBDT, we apply the same GBDT method to the new catalog of more than 690,000 stars classified as RGB stars. The test data-set shows that the median relative error is around 0.3 $\%$ for the method. We also compare the predicted ages of RGB stars with other studies (e.g. based on APOGEE), and find that they are almost consistent. The final uncertainty is about 14 $\%$ compared to open clusters' ages. Then we present the spatial distribution of the RGB sample having an age determination and discuss some systematics. All these diagnostics show that one can apply the GBDT method to other stellar samples to estimate atmospheric parameters and age.

Absorption lines at high redshift in front of quasars are rare in the mm domain. Only five associated and five intervening systems are known. These bring very useful information complementary to emission lines, for instance, to distinguish between inflows and outflows. They are also good candidates to study the variations of the fundamental constants. We report here the search for molecules in emission and absorption in front of a sample of 30 targets, comprising 16 associated and 14 intervening HI 21-cm absorbers. The observations have been done with the IRAM-30m telescope, simultaneously at 3mm and 2mm, exploring CO ladder and HCO+ lines. Eight targets have been detected in emission, of which five are new. Their molecular gas masses range from 10^9 to 7 10^11 Mo. We also report four new detections in absorption. Two of the associated CO absorption line detections at high redshift (z=1.211 and 1.275) resulted from the high spatial resolution follow-up with NOEMA. The disparity between the mm molecular and HI 21-cm absorption lines for these and another intervening system detected in HNC at z = 1.275, is attributable to radio and mm sight lines tracing different media. Comparing HI and H2 in the 14 known high redshift molecular absorbers, associated HI absorption lines are broad, with multiple components and the molecular absorption corresponds to the broader and weaker 21-cm absorption component. This indicates two distinct phases: one near galaxy centers with a larger CO-to-HI abundance ratio, and another with lower molecular abundance in the outer regions of the galaxy. The comparison of interferometric and single dish observations shows that the detection of absorption requires sufficient spatial resolution to overcome the dilution by emission, and will be an important criterion for mm follow-up of 21-cm absorbers from ongoing large-scale surveys.

In this work we extend previous theoretical works to gain a better understanding of the origin of recently observed polarisation degree spectra of molecular clouds, which show a so-called V-shape, i.e. a pronounced minimum around 350 $\mu$m. For this purpose, we present results of semi-analytical dust polarisation models. We benchmark our model against dust polarisation radiative transfer calculations performed with POLARIS. We show that V-shaped polarisation spectra can only be obtained if two dust phases, one dense and cold and one warm and dilute phase, are present along the line of sight. In contrast to previous results, no correlation between the alignment efficiency of silicate grains and the dust temperature is required; carbon grains are assumed to be not aligned with the magnetic field. We find that the V-shape is the stronger pronounced the larger the density and temperature contrast between both phases is. Moreover, the destruction of carbon grains by UV radiation in the warm and dilute phase leads to a significantly more pronounced V-shape in the polarisation spectrum. Reducing the alignment efficiency in the cold and dense phase also results in a more pronounced V-shape, its effect, however, is smaller than that of the UV-induced carbon grain destruction. Furthermore, we present a first, self-consistent polarisation spectrum obtained from a 3D, magneto-hydrodynamical molecular cloud simulation. The spectrum matches well with our semi-analytical prediction demonstrating the potential of such complex 3D simulations to study polarisation spectra. Comparing our model results with actual observations indicates that carbon grain destruction in illuminated regions might be required to match these observations. Reducing the alignment efficiency of silicate grains in the cold and dense phase would further improve the match between both data, however, it appears to not be a necessity.

Many hot Jupiters may experience orbital decays, which are manifested as long-term transit timing variations. We have analyzed 7068 transits from the Transiting Exoplanet Survey Satellite (TESS) for a sample of 326 hot Jupiters. These new mid-transit time data allow us to update ephemerides for these systems. By combining the new TESS transit timing data with archival data, we search for possible long-term orbital period variations in these hot Jupiters using a linear and a quadratic ephemeris model. We identified 26 candidates that exhibit possible long-term orbital period variations, including 18 candidates with decreasing orbital periods and 8 candidates with increasing orbital periods. Among them, 12 candidates have failed in our leave-one-out cross-validation (LOOCV) test and thus should be considered as marginal candidates. In addition to tidal interaction, alternative mechanisms such as apsidal precession, R{\o}mer effect, and Applegate effect could also contribute to the observed period variations. The ephemerides derived in this work are useful for scheduling follow-up observations for these hot Jupiters in the future. The Python code used to generate the ephemerides is made available online.

We present evidence in support of the hypothesis that the young stellar object RNO 54 is a mature-stage FU Ori type source. The star was first cataloged as a ``red nebulous object" in the 1980s but appears to have undergone its outburst prior to the 1890s. Present-day optical and near-infrared spectra are consistent with those of other FU Ori type stars, both in the details of spectral line presence and shape, and in the overall change in spectral type from an FGK-type in the optical, to the M-type presented in the near-infrared. In addition, the spectral energy distribution of RNO 54 is well-fit by a pure-accretion disk model with parameters: $\dot{M} = 10^{-3.45\pm0.06}$ $M_\odot$ yr$^{-1}$, $M_* = 0.23\pm0.06 \ M_\odot$, and $R_\mathrm{inner} = 3.68\pm0.76 \ R_\odot$, though we believe $R_\mathrm{inner}$ is likely close to its upper range of $4.5 R_\odot$ in order to produce a $T_\mathrm{max} = 7000$ K that is consistent with the optical to near-infrared spectra. The resulting $L_\mathrm{acc}$ is $\sim 265 \ L_\odot$. To find these values, we adopted a source distance $d=1400$ pc and extinction $A_V=3.9$ mag, along with disk inclination $i=50$ deg based on consideration of confidence intervals from our initial disk model, and in agreement with observational constraints. The new appreciation of a well-known source as an FU Ori type object suggests that other such examples may be lurking in extant samples.

The aim of this paper is to present the implementation of two new CME models in the space weather forecasting tool, EUHFORIA. We introduce the two toroidal CME models analytically, along with their numerical implementation in EUHFORIA. One model is based on the modified Miller-Turner (mMT) solution, while the other is derived from the Soloviev equilibrium, a specific solution of the Grad-Shafranov equation. The magnetic field distribution in both models is provided in analytic formulae, enabling a swift numerical computation. After detailing the differences between the two models, we present a collection of thermodynamic and magnetic profiles obtained at Earth using these CME solutions in EUHFORIA with a realistic solar wind background. Subsequently, we explore the influence of their initial parameters on the time profiles at L1. In particular, we examine the impact of the initial density, magnetic field strength, velocity, and minor radius. In EUHFORIA, we obtained different thermodynamic and magnetic profiles depending on the CME model used. We found that changing the initial parameters affects both the amplitude and the trend of the time profiles. For example, using a high initial speed results in a fast evolving and compressed magnetic structure. The speed of the CME is also linked to the strength of the initial magnetic field due to the contribution of the Lorentz force on the CME expansion. However, increasing the initial magnetic field also increases the computation time. Finally, the expansion and integrity of the magnetic structure can be controlled via the initial density of the CME. Both toroidal CME models are successfully implemented in EUHFORIA and can be utilized to predict the geo-effectiveness of the impact of real CME events. Moreover, the current implementation could be easily modified to model other toroidal magnetic configurations.

Black hole X-ray binaries (BHBs) offer insights into extreme gravitational environments and the testing of general relativity. The X-ray spectrum collected by NICER offers valuable information on the properties and behaviour of BHBs through spectral fitting. However, traditional spectral fitting methods are slow and scale poorly with model complexity. This paper presents a new semi-supervised autoencoder neural network for parameter prediction and spectral reconstruction of BHBs, showing an improvement of up to a factor of 2,700 in speed while maintaining comparable accuracy. The approach maps the spectral features from the numerous outbursts catalogued by NICER and generalises them to new systems for efficient and accurate spectral fitting. The effectiveness of this approach is demonstrated in the spectral fitting of BHBs and holds promise for use in other areas of astronomy and physics for categorising large datasets.

A nova super-remnant (NSR) is an immense structure associated with a nova that forms when frequent and recurrent nova eruptions sweep up surrounding interstellar material (ISM) into a high density and distant shell. The prototypical NSR, measuring over 100 pc across, was discovered in 2014 around the annually erupting nova M31N 2008-12a. Hydrodynamical simulations demonstrated that the creation of a dynamic NSR by repeated eruptions transporting large quantities of ISM is not only feasible but that these structures should exist around all novae, whether the white dwarf (WD) is increasing or decreasing in mass. But it is only the recurrent nova (RNe) with the highest WD masses and accretion rates that should host observable NSRs. KT Eridani is, potentially, the eleventh RNe recorded in the Galaxy and is also surrounded by a recently unveiled H{\alpha} shell tens of parsecs across, consistent with a NSR. Through modelling the nova ejecta from KT Eri, we demonstrate that such an observable NSR could form in approximately 50,000 years, which fits with the proper motion history of the nova. We compute the expected H{\alpha} emission from the KT Eri NSR and predict that the structure might be accessible to wide-field X-ray facilities.

Discovering transiting exoplanets with long orbital periods allows us to study warm and cool planetary systems with temperatures similar to the planets in our own Solar system. The TESS mission has photometrically surveyed the entire Southern Ecliptic Hemisphere in Cycle 1 (August 2018 - July 2019), Cycle 3 (July 2020 - June 2021) and Cycle 5 (September 2022 - September 2023). We use the observations from Cycle 1 and Cycle 3 to search for exoplanet systems that show a single transit event in each year - which we call duotransits. The periods of these planet candidates are typically in excess of 20 days, with the lower limit determined by the duration of individual TESS observations. We find 85 duotransit candidates, which span a range of host star brightnesses between 8 < $T_{mag}$ < 14, transit depths between 0.1 per cent and 1.8 per cent, and transit durations between 2 and 10 hours with the upper limit determined by our normalisation function. Of these candidates, 25 are already known, and 60 are new. We present these candidates along with the status of photometric and spectroscopic follow-up.

Among highly irradiated exoplanets, some have been found to undergo significant hydrodynamic expansion traced by atmospheric escape. To better understand these processes in the context of planetary evolution, we propose NIGHT (the Near-Infrared Gatherer of Helium Transits). NIGHT is a high-resolution spectrograph dedicated to surveying and temporally monitoring He I triplet absorption at 1083nm in stellar and planetary atmospheres. In this paper, we outline our scientific objectives, requirements, and cost-efficient design. Our simulations, based on previous detections and modelling using the current exoplanet population, determine our requirements and survey targets. With a spectral resolution of 70,000 on a 2-meter telescope, NIGHT can accurately resolve the helium triplet and detect 1% peak absorption in 118 known exoplanets in a single transit. Additionally, it can search for three-sigma temporal variations of 0.4% in 66 exoplanets in-between two transits. These are conservative estimates considering the ongoing detections of transiting planets amenable to atmospheric characterisation. We find that instrumental stability at 40m/s, less stringent than for radial velocity monitoring, is sufficient for transmission spectroscopy in He I. As such, NIGHT can utilize mostly off-the-shelf components, ensuring cost-efficiency. A fibre-fed system allows for flexibility as a visitor instrument on a variety of telescopes, making it ideal for follow-up observations after JWST or ground-based detections. Over a few years of surveying, NIGHT could offer detailed insights into the mechanisms shaping the hot Neptune desert and close-in planet population by significantly expanding the statistical sample of planets with known evaporating atmospheres. First light is expected in 2024.

The general prediction that more than half of all CVs have evolved past the period minimum is in strong disagreement with observational surveys, which show that the relative number of these objects is just a few per cent. Here, we investigate whether a large number of post-period minimum CVs could detach because of the appearance of a strong white dwarf magnetic field potentially generated by a rotation- and crystallization-driven dynamo. We used the MESA code to calculate evolutionary tracks of CVs incorporating the spin evolution and cooling as well as compressional heating of the white dwarf. If the conditions for the dynamo were met, we assumed that the emerging magnetic field of the white dwarf connects to that of the companion star and incorporated the corresponding synchronization torque, which transfers spin angular momentum to the orbit. We find that for CVs with donor masses exceeding 0.04 Msun, magnetic fields are generated mostly if the white dwarfs start to crystallize before the onset of mass transfer. It is possible that a few white dwarf magnetic fields are generated in the period gap. For the remaining CVs, the conditions for the dynamo to work are met beyond the period minimum, when the accretion rate decreased significantly. Synchronization torques cause these systems to detach for several Gyrs even if the magnetic field strength of the white dwarf is just one MG. If the rotation- and crystallization-driven dynamo - which is currently the only mechanism that can explain several observational facts related to magnetism in CVs and their progenitors - or a similar temperature-dependent mechanism is responsible for the generation of magnetic field in white dwarfs, most CVs that have evolved beyond the period minimum must detach for several Gyrs at some point. This reduces the predicted number of semi-detached period bouncers by up to 60-80 per cent.

We present a campaign designed to train the GRANDMA network and its infrastructure to follow up on transient alerts and detect their early afterglows. In preparation for O4 II campaign, we focused on GRB alerts as they are expected to be an electromagnetic counterpart of gravitational-wave events. Our goal was to improve our response to the alerts and start prompt observations as soon as possible to better prepare the GRANDMA network for the fourth observational run of LIGO-Virgo-Kagra (which started at the end of May 2023), and future missions such as SM. To receive, manage and send out observational plans to our partner telescopes we set up dedicated infrastructure and a rota of follow-up adcates were organized to guarantee round-the-clock assistance to our telescope teams. To ensure a great number of observations, we focused on Swift GRBs whose localization errors were generally smaller than the GRANDMA telescopes' field of view. This allowed us to bypass the transient identification process and focus on the reaction time and efficiency of the network. During 'Ready for O4 II', 11 Swift/INTEGRAL GRB triggers were selected, nine fields had been observed, and three afterglows were detected (GRB 220403B, GRB 220427A, GRB 220514A), with 17 GRANDMA telescopes and 17 amateur astronomers from the citizen science project Kilonova-Catcher. Here we highlight the GRB 220427A analysis where our long-term follow-up of the host galaxy allowed us to obtain a photometric redshift of $z=0.82\pm0.09$, its lightcurve elution, fit the decay slope of the afterglows, and study the properties of the host galaxy.

We assess the impact of satellite glints -- rapid flashes produced by reflections of a sunlight from flat surfaces of rotating satellites -- on current and future deep sky surveys such as the ones conducted by the Zwicky Transient Facility (ZTF) and the Vera C. Rubin Observatory upcoming Legacy Survey of Space and Time (LSST). In addition to producing a large number of streaks polluting the images, artificial satellites and space debris also generate great amount of false point-source alerts hindering the search for new rapid astrophysical transients. To investigate the extent of this problem, we perform an analysis of isolated single frame events detected by ZTF in more than three years of its operation, and, using three different methods, assess the fraction of them related to artificial satellites to be at least 20\%. The satellites causing them occupy all kinds of orbits around the Earth, and the duration of flashes produced by their rotation is from a fraction of a second down to milliseconds, with mean all-sky rate of up to 80,000 per hour.

Dwarf galaxies are known to exhibit an unusual richness in numbers of globular clusters (GCs), property quantified by the specific frequency ($S_N$), which is high for dwarf and giant elliptical galaxies, but with a minimum for intermediate-mass galaxies. In this work we study the role that GC evolution has in setting this trend, for which we use ${\it N}$-body simulations to evolve GCs in dwarf galaxies and quantify their disruption efficiency. We selected five individual dwarf galaxies from a high-resolution cosmological simulation, which includes GC formation and follow-up of their paths inside the host galaxy. Then, the tidal history of each GC is coupled to NBODY6++GPU to produce ${\it N}$-body models that account for both, the interaction of GCs with their galactic environment and their internal dynamics. This results in a GC mass loss parameterization to estimate dissolution times and mass loss rates after a Hubble time. GC evolution is sensitive to the particular orbital histories within each galaxy, but the overall result is that the amount of mass that GC systems lose scales with the mass (and density) of the host galaxy, i.e., the GC mass loss efficiency is lowest in low-mass dwarfs. After a 12 Gyr evolution all simulated GC systems retain an important fraction of their initial mass (up to 25%), in agreement with the high GC to field star ratios observed in some dwarfs, and supports the scenario in which GC disruption mechanisms play an important role in shaping the GC specific frequency in dwarf galaxies.

In this paper we combine the Early Science radio continuum data from the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) Survey, with optical and near-infrared data and release the cross-matched catalogues. The radio data used in this work covers $0.86$ deg$^2$ of the COSMOS field, reaches a thermal noise of $1.7$ $\mu$Jy/beam and contains $6102$ radio components. We visually inspect and cross-match the radio sample with optical and near-infrared data from the Hyper Suprime-Cam (HSC) and UltraVISTA surveys. This allows the properties of active galactic nuclei and star-forming populations of galaxies to be probed out to $z \approx 5$. Additionally, we use the likelihood ratio method to automatically cross-match the radio and optical catalogues and compare this to the visually cross-matched catalogue. We find that 94 per cent of our radio source catalogue can be matched with this method, with a reliability of $95$ per cent. We proceed to show that visual classification will still remain an essential process for the cross-matching of complex and extended radio sources. In the near future, the MIGHTEE survey will be expanded in area to cover a total of $\sim$20~deg$^2$; thus the combination of automated and visual identification will be critical. We compare redshift distribution of SFG and AGN to the SKADS and T-RECS simulations and find more AGN than predicted at $z \sim 1$.

The discovery of the optical counterpart, along with the gravitational waves from GW170817, of the first binary neutron star merger, opened up a new era for multi-messenger astrophysics. Combining the GW data with the optical counterpart, also known as AT2017gfo, classified as a kilonova, has revealed the nature of compact binary merging systems by extracting enriched information about the total binary mass, the mass ratio, the system geometry, and the equation of state. Even though the detection of kilonova brought about a revolution in the domain of multi-messenger astronomy, since there has been only one kilonova from a gravitational wave detected binary neutron star merger event so far, this limits the exact understanding of the origin and propagation of the kilonova. Here, we use a conditional variational autoencoder trained on light curve data from two kilonova models having different temporal lengths, and consequently, generate kilonova light curves rapidly based on physical parameters of our choice with good accuracy. Once trained, the time scale for light curve generation is of the order of a few milliseconds, thus speeding up generating light curves by $1000$ times compared to the simulation. The mean squared error between the generated and original light curves is typically $0.015$ with a maximum of $0.08$ for each set of considered physical parameter; while having a maximum of $\approx0.6$ error across the whole parameter space. Hence, implementing this technique provides fast and reliably accurate results.

High-resolution Hubble Space Telescope (\textit{HST}) optical observations have been used to perform the deepest photometric study of the poorly studied Galactic globular cluster NGC 6284. The deep colour-magnitude diagram (CMD) that we obtained reaches 6 magnitudes below the main sequence turn-off. We provide the first determination of the gravitational centre ($C_{\rm grav}$) and density profile of the system from resolved stars. $C_{\rm grav}$ is significantly offset (by $1.5-3''$) from the values in the literature. The density profile shows the presence of a steep central cusp, unambiguously indicating that the cluster experienced the core-collapse phase. Updated values of the structural parameters and relaxation times of the system are provided. We also constructed the first high-resolution reddening map in the cluster direction, which allowed us to correct the evolutionary sequences in the CMD for the effects of differential reddening. Isochrone fitting to the corrected CMD provided us with new estimates of the cluster age, average colour excess, metallicity, and distance. We find an absolute age of $13.3 \pm 0.4$ Gyr, an average colour excess $E(B-V) = 0.32 \pm 0.01$, a metallicity [Fe/H]$= -1.36 \pm 0.01$, and a true distance modulus $(m-M)_0 = 15.61 \pm 0.04$ that sets the cluster distance at $13.2 \pm 0.2$ kpc from the Sun. The superb quality of the CMD allowed a clear-cut identification of the Red Giant Branch (RGB) bump, which is clearly distinguishable along the narrow RGB. The absolute magnitude of this feature turns out to be $\sim 0.2$ mag fainter than previous identification.

The Blanco DECam Bulge Survey (BDBS) provides near-ultraviolet to near-infrared photometry for ~250 million unique stars. By combining BDBS photometry with the latest Gaia astrometry, we characterize the chemo-dynamics of red clump stars across the BDBS footprint, using an unprecedented sample size and sky coverage. We construct a sample of ~2.3 million red clump giants in the bulge with photometric metallicities, BDBS photometric distances, and proper motions. We study the kinematics of the red clump stars as a function of sky position and metallicity, by investigating proper motion rotation curves, velocity dispersions, and proper motion correlations across the southern Galactic bulge. We find that metal-poor red clump stars exhibit lower rotation amplitudes, at ~29 km s$^{-1}$ kpc^{-1}. The peak of the angular velocity is ~39 km s^{-1} kpc^{-1} for [Fe/H] ~ -0.2 dex, exhibiting declining rotation at higher [Fe/H]. The velocity dispersion is higher for metal-poor stars, while metal-rich stars show a steeper gradient with Galactic latitude, with a maximum dispersion at low latitudes along the bulge minor axis. Only metal-rich stars ([Fe/H] >~ -0.5 dex) show clear signatures of the bar in their kinematics, while the metal-poor population exhibits isotropic motions with an axisymmetric pattern around Galactic longitude l = 0. This work reports the largest sample of bulge stars with distance, metallicity, and astrometry and shows clear kinematic differences with metallicity. The global kinematics over the bulge agrees with earlier studies. However, we see striking changes with increasing metallicity and for the first time, see kinematic differences for stars with [Fe/H]>-0.5, suggesting that the bar itself may have kinematics that depends on metallicity.

Radiation emitted by nonthermal particles accelerated during relativistic magnetic reconnection is critical for understanding the nonthermal emission in a variety of astrophysical systems, including blazar jets, black hole coronae, pulsars, and magnetars. By means of fully kinetic Particle-in-Cell (PIC) simulations, we demonstrate that reconnection-driven particle acceleration imprints an energy-dependent pitch-angle anisotropy and gives rise to broken power laws in both the particle energy spectrum and the pitch-angle anisotropy. The particle distributions depend on the relative strength of the non-reconnecting (guide field) versus the reconnecting component of the magnetic field ($B_g/B_0$) and the lepton magnetization ($\sigma_0$). Below the break Lorentz factor $\gamma_0$ (injection), the particle energy spectrum is ultra-hard ($p_< < 1$), while above $\gamma_0$, the spectral index $p_>$ is highly sensitive to $B_g/B_0$. Particles' velocities align with the magnetic field, reaching minimum pitch angles $\alpha$ at a Lorentz factor $\gamma_{\min \alpha}$ controlled by $B_g/B_0$ and $\sigma_0$. The energy-dependent pitch-angle anisotropy, evaluated through the mean of $\sin^2 \alpha$ of particles at a given energy, exhibits power-law ranges with negative ($m_<$) and positive ($m_>$) slopes below and above $\gamma_{\min \alpha}$, becoming steeper as $B_g/B_0$ increases. The generation of anisotropic pitch angle distributions has important astrophysical implications. We address their effects on regulating synchrotron luminosity, spectral energy distribution, polarization, particle cooling, the synchrotron burnoff limit, emission beaming, and temperature anisotropy.

We outline some of the highlights of the scientific case for the advancement of stellar high energy physics using the Line Emission Mapper X-ray Probe ({\it LEM}). The key to advancements with LEM lie in its large effective area -- up to 100 times that of the {\it Chandra} MEG -- and 1~eV spectral resolution. The large effective area opens up for the first time the ability to study time-dependent phenomena on their natural timescales at high resolution, such as flares and coronal mass ejections, and also opens the sky to much fainter targets than available to {\it Chandra} or {\it XMM-Newton}.

We investigate the viability of MHD waves, in particular acoustic p-modes, in causing strong current accumulation at the null points. We begin with a three-dimensional numerical setup incorporating a gravitationally stratifed solar atmosphere and an axially symmetric magnetic feld including a coronal magnetic null point. To excite waves, we employ wave drivers mimicking global p-modes. We found that most of the vertical velocity transmits through the Alfv\'en acoustic equipartition layer maintaining acoustic nature while a small fraction generates fast waves via the mode conversion process. The fast waves undergo almost total refection at the transition region due to sharp gradients in density and Alfv\'en speed. There are only weak signatures of Alfv\'en wave generation near the transition region due to fast-to-Alfv\'en mode conversion. Since the slow waves propagate with the local sound speed, they are not much afected by the density gradients at the transition region and undergo secondary mode conversion and transmission at the Alfv\'en-acoustic equipartition layer surrounding the null point, leading to fast wave focusing at the null point. These fast waves have associated perturbations in current density, showing oscillatory signatures compatible with the second harmonic of the driving frequency which could result in resistive heating and enhanced intensity in the presence of fnite resistivity. We conclude that MHD waves could be a potential source for oscillatory current dissipation around the magnetic null point. We conjecture that besides oscillatory magnetic reconnection, global p-modes could lead to the formation of various quasiperiodic energetic events.

The discovery of two interstellar objects passing through the Solar System, 1I/`Oumuamua and 2I/Borisov, implies that a galactic population exists with a spatial number density of order $\sim0.1$ au$^{-3}$. The forthcoming Rubin Observatory Legacy Survey of Space and Time (LSST) has been predicted to detect more asteroidal interstellar objects like 1I/`Oumuamua. We apply recently developed methods to simulate a suite of galactic populations of interstellar objects with a range of assumed kinematics, albedos and size-frequency distributions (SFD). We incorporate these populations into the objectsInField (OIF) algorithm, which simulates detections of moving objects by an arbitrary survey. We find that the LSST should detect between $\sim 0-70$ asteroidal interstellar objects every year (assuming the implied number density), with sensitive dependence on the SFD slope and characteristic albedo of the host population. The apparent rate of motion on the sky -- along with the associated trailing loss -- appears to be the largest barrier to detecting interstellar objects. Specifically, a relatively large number of synthetic objects would be detectable by the LSST if not for their rapid sky-motion ($>0.5^\circ$ d$^{-1}$). Therefore, algorithms that could successfully link and detect rapidly moving objects would significantly increase the number of interstellar object discoveries with the LSST (and in general). The mean diameter of detectable, inactive interstellar objects ranges from $\sim50 - 600$ m and depends sensitively on the SFD slope and albedo.

The information regarding how the intergalactic medium is reionized by astrophysical sources is contained in the tomographic three-dimensional 21 cm images from the epoch of reionization. In Zhao et al. (2022a) ("Paper I"), we demonstrated for the first time that density estimation likelihood-free inference (DELFI) can be applied efficiently to perform a Bayesian inference of the reionization parameters from the 21 cm images. Nevertheless, the 3D image data needs to be compressed into informative summaries as the input of DELFI by, e.g., a trained 3D convolutional neural network (CNN) as in Paper I (DELFI-3D CNN). Here in this paper, we introduce an alternative data compressor, the solid harmonic wavelet scattering transform (WST), which has a similar, yet fixed (i.e. no training), architecture to CNN, but we show that this approach (i.e. solid harmonic WST with DELFI) outperforms earlier analyses based on 3D 21 cm images using DELFI-3D CNN in terms of credible regions of parameters. Realistic effects, including thermal noise and residual foreground after removal, are also applied to the mock observations from the Square Kilometre Array (SKA). We show that under the same inference strategy using DELFI, the 21 cm image analysis with solid harmonic WST outperforms the 21 cm power spectrum analysis. This research serves as a proof of concept, demonstrating the potential to harness the strengths of WST and simulation-based inference to derive insights from future 21 cm light-cone image data.

In this work, we focus on the study of radiation induced desorption processes that occurred in acetonitrile ice irradiated by broadband X-rays (6 eV to 2 keV) monitored by FTIR spectroscopy at different radiation fluences. In a previous work, we used the PROCODA code to derive the chemical evolution of the ice. Here, we have obtained that the acetonitrile desorbed column density is at least two orders of magnitude larger than the desorbed column densities of daughter or granddaughter molecular species at chemical equilibrium stage. This indicates that total desorption column density is mainly governed by the father molecule, as also previously hypothesized in experimental studies. This occurs basically because the acetonitrile column density is larger than the other ones. In particular, at chemical equilibrium acetonitrile desorption column density represents almost 98\% of the total, while it is close to 1\% for H, CN and CH$_2$, the species with larger molecular desorption percentages at chemical equilibrium. Another derived quantity is what we called intrinsic desorption rate, which is a number per second for individual species. Some of the larger intrinsic desorption rates were: CH$_3$CN ($6.2\times 10^{-6}$), CN ($6.2\times 10^{-6}$), H ($5.7\times 10^{-6}$), CH$_2$ ($5.7\times 10^{-6}$) and C$_2$N$_2$ ($4.4\times 10^{-6}$). These results help to put constrain in astrochemical models and can be also useful to clarify some astronomical radio observations.

It is well known that damped superimposed oscillations at large scales in the primordial power spectrum can be generated in both single field and two field models. In single field inflationary models, these features typically arise due to deviations from the slow roll regime. On the other hand, in two field models, these features are generated due to a turn in the background trajectory in the field space. In this work, we demonstrate that both single field and two field models can produce identical features at large scales in the primordial power spectrum. To achieve this, we utilize the generalized slow roll approximation and successfully reconstruct single field models based on the featured power spectrum typically generated in two field models. To validate our methodology, we numerically calculate the power spectrum from the reconstructed potential and find a remarkable agreement with the power spectrum which is obtained from the two field model.

The advent of gravitational-wave astronomy is now allowing for the study of compact binary merger demographics throughout the Universe. This information can be leveraged as tools for understanding massive stars, their environments, and their evolution. One active question is the nature of compact binary formation: the environmental and chemical conditions required for black hole birth and the time delays experienced by binaries before they merge. Gravitational-wave events detected today, however, primarily occur at low or moderate redshifts due to current interferometer sensitivity, therefore limiting our ability to probe the high redshift behavior of these quantities. In this work, we circumvent this limitation by using an additional source of information: observational limits on the gravitational-wave background from unresolved binaries in the distant Universe. Using current gravitational-wave data from the first three observing runs of LIGO-Virgo-KAGRA, we combine catalogs of directly detected binaries and limits on the stochastic background to constrain the time-delay distribution and metallicity dependence of binary black hole evolution. Looking to the future, we also explore how these constraints will be improved at the Advanced LIGO A+ sensitivity. We conclude that, although binary black hole formation cannot be strongly constrained with today's data, the future detection (or a non-detection) of the gravitational-wave background with Advanced LIGO A+ will carry strong implications for the evolution of binary black holes.

We present a semiclassical non-perturbative approach for calculating the preheating process at the end of inflation. Our method involves integrating out the decayed particles within the path integral framework and subsequently determining world-line instanton solutions in the effective action. This enables us to obtain the effective action of the inflaton, with its imaginary part linked to the phenomenon of particle creation driven by coherent inflaton field oscillations. Additionally, we utilize the Bogoliubov transformation to investigate the evolution of particle density within the medium after multiple inflaton oscillations. We apply our approach to various final state particles, including scalar fields, tachyonic fields, and gauge fields. The non-perturbative approach provides analytical results for preheating that are in accord with previous methods.

We describe a realistic mechanism whereby black holes with significant QCD color charge could have formed during the early universe. Primordial black holes (PBHs) could make up a significant fraction of the dark matter if they formed well before the QCD confinement transition. Such PBHs would form by absorbing unconfined quarks and gluons, and hence could acquire a net color charge. We estimate the number of PBHs per Hubble volume with near-extremal color charge for various scenarios, and discuss possible phenomenological implications.

Orbital eccentricity and spin precession are precious observables to infer the formation history of binary black holes with gravitational-wave data. We present a post-Newtonian, multi-timescale analysis of the binary dynamics able to capture both precession and eccentricity over long inspirals. We show that the evolution of an eccentric binary can be reduced that of effective source on quasi-circular orbits, coupled to a post-Newtonian prescription for the secular evolution of the eccentricity. Our findings unveil an interplay between precession and eccentricity: the spins of eccentric binaries precess on shorter timescales and their nutation amplitude is altered compared to black holes on quasi-circular orbits, consequently affecting the so-called spin morphology. Even if binaries circularize by the time they enter the sensitivity window of our detectors, their spin orientations retain some memory of the past evolution on eccentric orbits, thus providing a new link between gravitational-wave detection and astrophysical formation. At the same time, we point out that residual eccentricity should be considered a source of systematics when reconstructing the past history of black-hole binaries using the spin orientations.

On the basis of a general action principle, we revisit the scale invariant field equation using the co-tensor relations by Dirac (1973). This action principle also leads to an expression for the scale factor $\lambda$, which corresponds to the one derived from the gauging condition, which assumes that a macroscopic empty space is scale-invariant, homogeneous, and isotropic. These results strengthen the basis of the scale-invariant vacuum (SIV) paradigm. From the field and geodesic equations, we derive, in current time units (years, seconds), the Newton-like equation, the equations of the two-body problem, and its secular variations. In a two-body system, orbits very slightly expand, while the orbital velocity keeps constant during expansion. Interestingly enough, Kepler's third law is a remarkable scale-invariant property.

This study uses a nonsingular Yukawa--modified potential to obtain a static and spherically symmetric black hole solution with a cosmological constant. Such Yukawa--like corrections are encoded in two parameters, $\alpha$ and $\lambda$, that modify Newton's law of gravity in large distances, and a deformation parameter $\ell_0$, which plays an essential role in short distances. The most significant effect is encoded in $\alpha$, which modifies the total black hole mass with an extra mass proportional to $\alpha M$, mimicking the dark matter effects at large distances from the black hole. On the other hand, the effect due to $\lambda$ is small for astrophysical values. We scrutinize the \textit{quasinormal} frequencies and shadows associated with a spherically symmetric black hole and the thermodynamical behavior influenced by the Yukawa potential. In particular, the thermodynamics of this black hole displays a rich behavior, including possible phase transitions. We use the WKB method to probe the \textit{quasinormal} modes of massless scalar, electromagnetic, and gravitational field perturbations. In order to check the influence of the parameters on the shadow radius, we consider astrophysical data to determine their values, incorporating information on an optically thin radiating and infalling gas surrounding a black hole to model the black hole shadow image. In particular, we consider Sgr A* black hole as an example and we find that its shadow radius changes by order of $10^{-9}$, meaning that the shadow radius of a black hole with Yukawa potential practically gives rise to the same result encountered in the Schwarzschild black hole. Also, in the eikonal regime, using astrophysical data for Yukawa parameters, we show that the value of the real part of the QNMs frequencies changes by $10^{-18}$.

The recent stochastic signal observed jointly by NANOGrav, PPTA, EPTA, and CPTA can be accounted for by scalar-induced gravitational waves (SIGWs). The source of the SIGWs is from the primordial curvature perturbations, and the main contribution to the SIGWs is from the peak of the primordial curvature power spectrum. To effectively model this peak, we apply the Taylor expansion to parameterize it. With the Taylor expansion parameterization, we apply Bayesian methods to constrain the primordial curvature power spectrum based on the NANOGrav 15-year data set. The constraint on the primordial curvature power spectrum possesses a degree of generality, as the Taylor expansion can effectively approximate a wide range of function profiles.

We compute the evolution of the entanglement entropy for a massless field within a spherical region throughout the inflationary period and the subsequent era of radiation domination, starting from the Bunch-Davies vacuum. The transition of each mode towards a squeezed state upon horizon exit during inflation and the additional squeezing when radiation domination sets in enhance the entanglement entropy. Shortly after the transition to the radiation-dominated era, a volume term develops and becomes the leading contribution to the entropy at late times, as is common for systems lying in squeezed states. We estimate the magnitude of the entropy and discuss its interpretation in the light of the quantum to classical transition for modes exiting the horizon during inflation. Our results raise the possibility that the quantum nature of weakly interacting fields, such as gravitational waves resulting from tensor modes during inflation, may be detectable in today's universe. On the other hand, an observer with no knowledge of the degrees of freedom beyond the horizon would interpret the entropy as thermal. From this point of view, the reheating after inflation would be a result of quantum entanglement.

Dark matter could accumulate around neutron stars in sufficient amounts to affect their global properties. In this work, we study the effect of a specific model for dark matter -- a massive and self-interacting vector (spin-1) field -- on neutron stars. We describe the combined systems of neutron stars and vector dark matter using Einstein-Proca theory coupled to a nuclear-matter term, and find scaling relations between the field and metric components in the equations of motion. We construct equilibrium solutions of the combined systems, compute their masses and radii and also analyse their stability and higher modes. The combined systems admit dark matter (DM) core and cloud solutions. Core solutions compactify the neutron star component and tend to decrease the total mass of the combined system. Cloud solutions have the inverse effect. Electromagnetic observations of certain cloud-like configurations would appear to violate the Buchdahl limit. This could make Buchdahl-limit violating objects smoking gun signals for dark matter in neutron stars. The self-interaction strength is found to significantly affect both mass and radius. We also compare fermion Proca stars to objects where the dark matter is modelled using a complex scalar field. We find that fermion Proca stars tend to be more massive and geometrically larger than their scalar field counterparts for equal boson masses and self-interaction strengths. Both systems can produce degenerate masses and radii for different amounts of DM and DM particle masses.

The $\phi$ meson and $\Omega$ baryon provide unique probes of the properties of the quark-gluon plasma (QGP) at hadronization in relativistic heavy-ion collisions. Using the quark recombination model with the quark phase-space information parameterized in a viscous blastwave, we perform Bayesian inference of the shear and bulk viscosities of the QGP at hadronization with a temperature of $T\sim 160$ MeV by analyzing the $\phi$ and $\Omega$ data in Au+Au collisions at $\sqrt{s_{\rm NN}}=$ 19.6-200 GeV and Pb+Pb collisions at $\sqrt{s_{\rm NN}}=$ 2.76 TeV, corresponding to a baryon chemical potential variation from $\mu_B\approx 0$ (at $\sqrt{s_{\rm NN}}= 2.76$ TeV) to $200$ MeV (at $\sqrt{s_{\rm NN}}= 19.6$ GeV). We find that the shear viscosity to enthalpy ratio $\eta T/(\epsilon +P)$ of the QGP at hadronization decreases as $\mu_B$ increases, with $\eta T/(\epsilon +P)\approx 0.18$ at $\mu_B=0$ and $\eta T/(\epsilon +P)\approx 0.08$ at $\mu_B=200$ MeV, while the corresponding specific bulk viscosity is essentially constant with $\zeta T/(\epsilon + P)=0.02\sim 0.04$ for $\mu_B<200$ MeV. Our results suggest that the QGP at hadronization ($T\sim 160$ MeV) with finite baryon density is more close to perfect fluid than that with zero baryon density.

In several classes of modified gravity theories, extra degrees of freedom are not completely screened in the interiors of stellar and substellar objects. In such theories, the hydrostatic equilibrium condition inside these objects is altered. Moreover, the interior structures of these objects might have a small pressure anisotropy induced by several physical phenomena, including rotation and magnetic fields. All these effects, both individually and collectively, induce changes in predicted stellar observables. Such changes have an impact on different phases of the stellar life cycle, starting from its birth to its death, covering almost all the branches of the Hertzsprung-Russell diagram. The aim of this work is to systematically review the current literature on the topic. We discuss the main results and constraints obtained on a class of modified gravity theories.

We investigate light propagation in the context of multiple gravitational lenses. Assuming these lenses are sufficiently spaced to prevent interaction, we focus on a linear alignment scenario of the transmitter, lenses, and receiver. Remarkably, in this axially-symmetric configuration, we can precisely solve the relevant diffraction integrals, which offers valuable analytical insights. The point-spread function (PSF) is affected by the number of lenses in the system and the distances between them. Even a single lens is useful for transmission either it is used as a part of the transmitter or acts on the receiver's side. We show that power transmission via a pair of lenses depends on the initial lens, influenced by both its mass and transmitter's position. The second lens plays an important role by focusing the signal to a much tighter spot. Yet in realistic lensing scenarios, the second lens changes the structure of the PSF on scales much smaller than the telescope, thus gain increase provided by the second lens is independent of its properties. We demonstrate that transmission via a pair of lenses benefits from gravitational amplification at both ends of the transmission link -- a finding with profound implications for applications targeting interstellar power transmission.