Papers for Thursday, Nov 09 2023

We present a look at Ookami, a project providing community access to a testbed supercomputer with the ARM-based A64FX processors developed by a collaboration between RIKEN and Fujitsu and deployed in the Japanese supercomputer Fugaku. We describe the project, provide details about the user base and education/training program, and present highlights from performance studies of two astrophysical simulation codes.

Debris discs are our best means to probe the outer regions of planetary systems. Many studies assume that planets lie at the inner edges of debris discs, akin to Neptune and the Kuiper Belt, and use the disc morphologies to constrain those otherwise-undetectable planets. However, this produces a degeneracy in planet mass and semimajor axis. We investigate the effect of a sculpting planet on the radial surface-density profile at the disc inner edge, and show that this degeneracy can be broken by considering the steepness of the edge profile. Like previous studies, we show that a planet on a circular orbit ejects unstable debris and excites surviving material through mean-motion resonances. For a non-migrating, circular-orbit planet, in the case where collisions are negligible, the steepness of the disc inner edge depends on the planet-to-star mass ratio and the initial-disc excitation level. We provide a simple analytic model to infer planet properties from the steepness of ALMA-resolved disc edges. We also perform a collisional analysis, showing that a purely planet-sculpted disc would be distinguishable from a purely collisional disc and that, whilst collisions flatten planet-sculpted edges, they are unlikely to fully erase a planet's signature. Finally, we apply our results to ALMA-resolved debris discs and show that, whilst many inner edges are too steep to be explained by collisions alone, they are too flat to arise through completed sculpting by non-migrating, circular-orbit planets. We discuss implications of this for the architectures, histories and dynamics in the outer regions of planetary systems.

Occultations provide indirect sensitivity to the number density of small Kuiper Belt objects (KBOs) too faint to directly detect telescopically. We present results from the Caltech HI-speed Multicolor camERA (CHIMERA) survey with the Palomar Hale Telescope, which monitored stars over the central 5'x5' of the M22 globular cluster along the ecliptic plane for serendipitous occultations by kilometer-scale KBOs over 63 hr across 24 nights at a 33 Hz frame rate simultaneously in i' and g'. We adapted dense-field photometry and occultation template fitting techniques to this dataset, finding a 95% confidence upper limit on the occultation rate corresponding to an ecliptic sky density of <10^7 deg^-2 of >1 km diameter classical KBOs. We discuss a few of the occultation-like light curve signatures at the edge of the sensitivity limit responsible for setting the upper bounds, and their likely nonviability as true occultations.

We present a uniform forward-modeling analysis of 90 late-M and L dwarfs in nearby young (~$10-200$ Myr) moving groups, the Pleiades, and the Hyades using low-resolution ($R\approx150$) near-infrared ($0.9-2.4$ $\mathrm{\mu m}$) spectra and the BT-Settl model atmospheres. We derive the objects' effective temperatures, surface gravities, radii, and masses by comparing our spectra to the models using a Bayesian framework with nested sampling and calculate the same parameters using evolutionary models. Assuming the evolutionary-based parameters are more robust, our spectroscopically inferred parameters from BT-Settl exhibit two types of systematic behavior for objects near the M-L spectral type boundary. Several are clustered around $T_\mathrm{eff} \approx 1800$ K and $\log g\approx5.5$ dex, implying impossibly large masses ($150-1400$ $M_\mathrm{Jup}$), while others are clustered around $T_\mathrm{eff}\gtrsim3000$ K and $\log g\lesssim3.0$ dex, implying non-physical low masses and unreasonably young ages. We find the fitted BT-Settl model spectra tend to overpredict the peak $J$ and $H$-band flux for objects located near the M-L boundary, suggesting the dust content included in the model atmospheres is insufficient to match the observations. By adding an interstellar medium-like reddening law to the BT-Settl model spectra, we find the fits between models and observed spectra are greatly improved, with the largest reddening coefficients occurring at the M-L transition. This work delivers a systematic examination of the BT-Settl model atmospheres and constitutes the largest spectral analysis of benchmark late-M and L-type brown dwarfs to date.

We conduct a systematic search for high-redshift galaxy overdensities at $4.9 < z_{\,\mathrm{spec}} < 8.9$ in both the GOODS-N and GOODS-S fields using JWST/NIRCam imaging from JADES and JEMS in addition to JWST/NIRCam wide field slitless spectroscopy from FRESCO. High-redshift galaxy candidates are identified using HST+JWST photometry spanning $\lambda = 0.4-5.0\ \mu\mathrm{m}$. We confirmed the redshifts for roughly a third of these galaxies using JWST/FRESCO spectroscopy over $\lambda = 3.9-5.0\ \mu\mathrm{m}$ through identification of either $\mathrm{H} \alpha$ or $\left[\mathrm{OIII}\right]\lambda5008$ around the best-fit photometric redshift. The rest-UV magnitudes and continuum slopes of these galaxies were inferred from the photometry: the brightest and reddest objects appear in more dense environments and thus are surrounded by more galaxy neighbors than their fainter and bluer counterparts, suggesting accelerated galaxy evolution within overdense environments. We find $17$ significant ($\delta_{\mathrm{gal}} \geq 3.04$, $N_{\mathrm{galaxies}} \geq 4$) galaxy overdensities across both fields ($7$ in GOODS-N and $10$ in GOODS-S), including the two highest redshift spectroscopically confirmed galaxy overdensities to date at $\left< z_{\mathrm{\,spec}} \right> = 7.955$ and $\left< z_{\mathrm{\,spec}} \right> = 8.222$ (representing densities around $\sim 6$ and $\sim 12$ times that of a random volume). We estimate the total halo mass of these large-scale structures to be $11.5 \leq \mathrm{log}_{10}\left(M_{\mathrm{halo}}/M_{\odot}\right) \leq 13.4$ using an empirical stellar mass to halo mass relation, which are likely underestimates as a result of incompleteness. These protocluster candidates are expected to evolve into massive galaxy clusters with $\mathrm{log}_{10}\left(M_{\mathrm{halo}}/M_{\odot}\right) \gtrsim 14$ by $z = 0$.

The astronomical community is grappling with the increasing volume and complexity of data produced by modern telescopes, due to difficulties in reducing, accessing, analyzing, and combining archives of data. To address this challenge, we propose the establishment of a coordinating body, an "entity," with the specific mission of enhancing the interoperability, archiving, distribution, and production of both astronomical data and software. This report is the culmination of a workshop held in February 2023 on the Future of Astronomical Data Infrastructure. Attended by 70 scientists and software professionals from ground-based and space-based missions and archives spanning the entire spectrum of astronomical research, the group deliberated on the prevailing state of software and data infrastructure in astronomy, identified pressing issues, and explored potential solutions. In this report, we describe the ecosystem of astronomical data, its existing flaws, and the many gaps, duplication, inconsistencies, barriers to access, drags on productivity, missed opportunities, and risks to the long-term integrity of essential data sets. We also highlight the successes and failures in a set of deep dives into several different illustrative components of the ecosystem, included as an appendix.

High-energy photons can produce electron-positron pairs upon interacting with the extragalactic background light (EBL). These pairs will in turn be deflected by the intergalactic magnetic field (IGMF), before possibly up-scattering photons of the cosmic microwave background (CMB), thereby initiating an electromagnetic cascade. The non-observation of an excess of GeV photons and an extended halo around individual blazars due to this electromagnetic cascade can be used to constrain the properties of the IGMF. In this work, we use publicly available data of 1ES 0229+200 by Fermi LAT and H.E.S.S. to constrain cosmological MHD simulations of various magnetogenesis scenarios, and find that all models without a strong space-filling primordial component or over-optimistic dynamo amplifications can be excluded at 95% confidence level. In fact, we find that the fraction of space filled by a strong IGMF has to be at least $f\gtrsim 0.67$, thus excluding most astrophysical production scenarios. Moreover, we set the lower limits $B_0>5.1\times 10^{-15}$ G ($B_0>1.0\times 10^{-14}$ G) of a space-filling primordial IGMF for a blazar activity time of $\Delta t = 10^4$ yr ($\Delta t = 10^7$ yr).

Recent years have seen excellent progress in modeling the entrainment of T $\sim$ $10^4$K atomic gas in galactic winds. However, the entrainment of cool, dusty T $\sim$ 10-100K molecular gas, which is also observed outflowing at high velocity, is much less understood. Such gas, which can be $10^5$ times denser than the hot wind, appears extremely difficult to entrain. We run 3D wind-tunnel simulations with photoionization self-shielding and evolve thermal dust sputtering and growth. Unlike almost all such simulations to date, we do not enforce any artificial temperature floor. We find efficient molecular gas formation and entrainment, as well as dust survival and growth through accretion. Key to this success is the formation of large amounts of 10^4K atomic gas via mixing, which acts as a protective "bubble wrap" and reduces the cloud overdensity to $\sim$ 100. This can be understood from the ratio of the mixing to cooling time. Before entrainment, when shear is large, t_mix/t_cool $\leq$ 1, and gas cannot cool below the "cooling bottleneck" at 5000K. Thus, the cloud survival criterion is identical to the well-studied purely atomic case. After entrainment, when shear falls, t_mix/t_cool > 1, and the cloud becomes multi-phase, with comparable molecular and atomic masses. The broad temperature PDF, with abundant gas in the formally unstable 50 K < T < 5000 K range, agrees with previous ISM simulations with driven turbulence and radiative cooling. Our findings have implications for dusty molecular gas in stellar and AGN outflows, cluster filaments, "jellyfish" galaxies and AGB winds.

Massive black hole binaries (MBHBs) are binary systems formed by black holes with mass exceeding millions of solar masses, expected to form and evolve in the nuclei of galaxies. The extreme compact nature of such objects determines a loud and efficient emission of Gravitational Waves (GWs), which can be detected by the Pulsar Timing Array (PTA) experiment in the form of a Gravitational Wave Background (GWB), i.e. a superposition of GW signals coming from different sources. The modelling of the GWB requires some assumptions on the binary population and the exploration of the whole involved parameter space is prohibitive as it is computationally expensive. We here train a Neural Network (NN) model on a semi-analytical modelling of the GWB generated by an eccentric population of MBHBs that interact with the stellar environment. We then use the NN to predict the characteristics of the GW signal in regions of the parameter space that we did not sample analytically. The developed framework allows us to quickly predict the level, shape and variance of the GWB signals produced in different universe realisations.

We present a sample of 88 candidate z~8.5-14.5 galaxies selected from the completed NIRCam imaging from the Cosmic Evolution Early Release Science (CEERS) survey. These data cover ~90 arcmin^2 (10 NIRCam pointings) in six broad-band and one medium-band imaging filter. With this sample we confirm at higher confidence early JWST conclusions that bright galaxies in this epoch are more abundant than predicted by most theoretical models. We construct the rest-frame ultraviolet luminosity functions at z~9, 11 and 14, and show that the space density of bright (M_UV=-20) galaxies changes only modestly from z~14 to z~9, compared to a steeper increase from z~8 to z~4. While our candidates are photometrically selected, spectroscopic followup has now confirmed 13 of them, with only one significant interloper, implying that the fidelity of this sample is high. Successfully explaining the evidence for a flatter evolution in the number densities of UV-bright z>10 galaxies may thus require changes to the dominant physical processes regulating star formation. While our results indicate that significant variations of dust attenuation with redshift are unlikely to be the dominant factor at these high redshifts, they are consistent with predictions from models which naturally have enhanced star-formation efficiency and/or stochasticity. An evolving stellar initial mass function could also bring model predictions into better agreement with our results. Deep spectroscopic followup of a large sample of early galaxies can distinguish between these competing scenarios.

The majority of massive disk galaxies in the local Universe show a stellar barred structure in their central regions, including our Milky Way. Bars are supposed to develop in dynamically cold stellar disks at low redshift, as the strong gas turbulence typical of disk galaxies at high redshift suppresses or delays bar formation. Moreover, simulations predict bars to be almost absent beyond $z = 1.5$ in the progenitors of Milky Way-like galaxies. Here we report observations of ceers-2112, a barred spiral galaxy at redshift $z_{\rm phot} \sim 3$, which was already mature when the Universe was only 2 Gyr old. The stellar mass ($M_{\star} = 3.9 \times 10^9 M_{\odot}$) and barred morphology mean that ceers-2112 can be considered a progenitor of the Milky Way, in terms of both structure and mass-assembly history in the first 2 Gyr of the Universe, and was the closest in mass in the first 4 Gyr. We infer that baryons in galaxies could have already dominated over dark matter at $z \sim 3$, that high-redshift bars could form in approximately 400 Myr and that dynamically cold stellar disks could have been in place by redshift $z = 4-5$ (more than 12 Gyrs ago).

We present a semi-analytic model for the growth, drift, desorption, and fragmentation of millimeter- to meter-sized particles in protoplanetary disks. Fragmentation occurs where particle collision velocities exceed critical fragmentation velocities. Using this criterion, we produce fragmentation regions in disk orbital radius-particle size phase space for particles with a range of material properties, structures, and compositions (including SiO$_2$, Mg$_2$SiO$_4$, H$_2$O, CO$_2$, and CO). For reasonable disk conditions, compact aggregate H$_2$O, CO$_2$, and CO ice particles do not reach destructive relative velocities and are thus not likely to undergo collisional fragmentation. Uncoated silicate particles are more susceptible to collisional destruction and are expected to fragment in the inner disk, consistent with previous work. We then calculate the growth, drift, and sublimation of small particles, initially located in the outer disk. We find that ice-coated particles can avoid fragmentation as they grow and drift inward under a substantial range of disk conditions as long as the particles are aggregates composed of 0.1 $\mu$m-sized monomers. Such particles may undergo runaway growth in disk regions abundant in H$_2$O or CO$_2$ ice depending on the assumed disk temperature structure. These results indicate that icy collisional growth to planetesimally-relevant sizes may happen efficiently throughout a disk's lifetime, and is particularly robust at early times when the disk's dust-to-gas ratio is comparable to that of the interstellar medium.

Accreting neutron stars differ from black holes by the presence of the star's own magnetic field, whose interaction with the accretion flow is a central component in understanding these systems' disk structure, outflows, jets, and spin evolution. It also introduces an additional degree of freedom, as the stellar dipole can have any orientation relative to the inner disk's magnetic field. We present a suite of 3D general-relativistic magnetohydrodynamic (GRMHD) simulations in which we investigate the two extreme polarities, with the dipole field being either parallel or antiparallel to the initial disk field, in both the accreting and propeller states. When the magnetosphere truncates the disk near or beyond the corotation radius, most of the system's properties, including the relativistic jet power, are independent of the star-disk relative polarity. However, when the disk extends well inside the corotation radius, in the parallel orientation the jet power is suppressed and the inner disk is less dense and more strongly magnetized. We suggest a physical mechanism that may account for this behavior - the interchange slingshot - and discuss its astrophysical implications.

We present measurements of the rest-frame UV spectral slope, $\beta$, for a sample of 36 faint star-forming galaxies at z ~ 9-16 discovered in one of the deepest JWST NIRCam surveys to date, the Next Generation Deep Extragalactic Exploratory Public (NGDEEP) Survey. We use robust photometric measurements for UV-faint galaxies (down to $M_{UV}$ ~ -16), originally published in Leung+23, and measure values of the UV spectral slope via photometric power-law fitting to both the observed photometry and to stellar population models obtained through spectral energy distribution (SED) fitting with Bagpipes. We obtain a median and 68% confidence interval for $\beta$ from photometric power-law fitting of $\beta_{PL} = -2.7^{+0.5}_{-0.5}$ and from SED-fitting, $\beta_{SED} = -2.3^{+0.2}_{-0.1}$ for the full sample. We show that when only 2-3 photometric detections are available, SED-fitting has a lower scatter and reduced biases than photometric power-law fitting. We quantify this bias and find that after correction, the median $\beta_{SED,corr} = -2.5^{+0.2}_{-0.2}$. We measure physical properties for our galaxies with Bagpipes and find that our faint ($M_{UV} = -18.1^{+0.7}_{-0.9}$) sample is low mass (${log}[M_{\ast}/M_\odot] = 7.7^{+0.5}_{-0.5}$), fairly dust-poor ($A_{v} = 0.1^{+0.2}_{-0.1}$ mag), and modestly young (${log[age]} = 7.8^{+0.2}_{-0.8}$ yr) with a median star formation rate of $\mathrm{log(SFR)} = -0.3^{+0.4}_{-0.4} M_\odot{/yr}$. We find no strong evidence for ultra-blue UV spectral slopes ($\beta$ ~ -3) within our sample, as would be expected for exotically metal-poor ($Z/Z_{\odot}$ < 10$^{-3}$) stellar populations with very high LyC escape fractions. Our observations are consistent with model predictions that galaxies of these stellar masses at z~9-16 should have only modestly low metallicities ($Z/Z_{\odot}$ ~ 0.1--0.2).

We perform a set of two-dimensional, non-relativistic, hydrodynamics simulations for supernova-like explosion associated with stellar core collapse of rotating massive stars to a system of a black hole and a disk connected by the transfer of matter and angular momentum. Our model of the central engine also includes the contribution of the disk wind. In this work, we specifically investigate the wind-driven explosion of rotating, large-mass progenitor stars with the zero-age main-sequence mass of $M_\mathrm{ZAMS}=20\,M_\odot$ from arXiv:2008.09132 . This study is carried out using the open-source hydrodynamic code Athena++, for which we implement a method to calculate self-gravity for axially symmetric density distributions. We, then, investigate the explosion properties and the $^{56}$Ni production as a function of (varying) some features of the wind injection. We find a large variety of explosion energy with $E_\mathrm{expl}$ ranging from $\sim 0.049\times10^{51}$~erg to $\sim 34\times10^{51}$~erg and ejecta mass $M_\mathrm{ej}$ from 0.58 to 6 $M_\odot$, which shows a bimodal distribution in high- and low-energy branches. We demonstrate that the resulting outcome of a highly- or sub-energetic explosion for a certain stellar structure is mainly determined by the competition between the ram pressure of the injected matter and that of the infalling envelope. In the nucleosynthesis analysis the $^{56}$Ni mass produced in our models goes from $< 0.2~M_\odot$ in the sub-energetic explosions to $2.1~M_\odot$ in the highly-energetic ones. These results are consistent with the observational data of stripped-envelope and high-energy SNe such as broad-lined type Ic SNe. However, we find a tighter correlation between the explosion energy and the ejecta mass than that observationally measured.

Context. Recent observations of close detached eclipsing M and K dwarf binaries have provided substantial support for magnetic saturation when stars rotate sufficiently fast, leading to a magnetic braking (MB) torque proportional to the spin of the star. Aims. We investigated here how strong MB torques need to be to reproduce the observationally-inferred relative numbers of white dwarf plus M dwarf post-common-envelope binaries under the assumption of magnetic saturation. Methods. We carried out binary population simulations with the BSE code adopting empirically-derived inter-correlated main-sequence binary distributions as initial binary populations and compared the simulation outcomes with observations. Results. We found that the dearth of extreme mass ratio binaries in the inter-correlated initial distributions is key to reproduce the large fraction of post-common-envelope binaries hosting low-mass M dwarfs (${\sim0.1-0.2}$ M$_\odot$). In addition, orbital angular momentum loss rates due to MB should be high for M dwarfs with radiative cores and orders of magnitude smaller for fully convective stars to explain the observed dramatic change of the fraction of short-period binaries at the fully convective boundary. Conclusions. We conclude that saturated but disrupted, that is, dropping drastically at the fully convective boundary, MB can explain the observations of both close main-sequence binaries containing M and K dwarfs and post-common-envelope binaries. Whether a similar prescription can explain the spin down rates of single stars and of binaries containing more massive stars needs to be tested.

The aim of this work is to create a complete list of sources exhibiting a long secondary period (LSP) in the ASAS-SN catalog of variable stars, and analyze the properties of this sample compared to other long period variables without LSP. We use the period-amplitude diagram to identify the 55572 stars showing an LSP, corresponding to 27% of the pulsating red giants in the catalog. We use the astrometric data from Gaia DR3 and the spectroscopic data provided by the APOGEE, GALAH, and RAVE surveys to investigate the statistical properties of the sample. We find that stars displaying an LSP have a spatial distribution that is more dispersed than the non-LSP giants, suggesting that they belong to an older population. Spectroscopically-derived ages seem to confirm this. The stars with an LSP also appear to be different in terms of C/O ratio from their non-LSP counterparts.

In many star-planet systems discovered so far, the innermost planet orbits within only a few stellar radii. In these systems, planets could become in-situ probes of the extended stellar magnetic field. Because they disturb the field as they move, they are expected to trigger flares in the corona. Potential differences to the energies and morphologies of intrinsic stellar flares are poorly constrained. However, as we expect planet-induced flares to correlate with the planet's orbital period, we can identify them from a clustering of flares in phase with the planet's orbit. We used the excellent phase coverage from Kepler and the Transiting Exoplanet Survey Satellite to find flaring star-planet systems, compile a catalog of all their flares, and measure how much they cluster in orbital phase. In the 1811 searched systems, we found 25 single stars with three or more flares each. We quantified the significance of the clustering in each system, and compared it against the theoretically expected power of magnetic interaction that leads to planet-induced flaring. Most systems do not show any clustering, consistent with low expected power. Those we expect to show clustering fall on two branches. An inactive one, without any signs of clustering, and a tentative active one, where the clustering becomes more pronounced as the expected power of interaction increases. The flares in HIP 67522 are prominently clustered (p<0.006). This young Hot Jupiter system is the most promising candidate for magnetic star-planet interaction in our sample.

The presence of distant protoplanets could explain the observed gaps in dust emission in protoplanetary disks. Here we derive a novel analytical model to describe the temporal decay of the pebble flux through a protoplanetary disk as a result of radial drift. This allows us to investigate the growth and migration of distant protoplanets throughout the lifespan of the disk. We find that early-formed Moon-mass protoplanets can grow to their pebble isolation mass between approximately $20$ and $80\,M_{\oplus}$ within less than $1\,\mathrm{Myr}$ in the $20$ to $80\,\mathrm{AU}$ region around solar-like stars. Subsequent fast migration at the early stages of gas accretion after pebble accretion has been halted nevertheless transports these giant planets into final orbits at $<\,$$10\,\mathrm{AU}$. However, our pebble decay model allows us to include a new pathway which can trigger the transition from pebble accretion to gas accretion after the pebble flux has decayed substantially. With this pebble decay pathway, we show that it is possible to form gas giants also beyond $10\,\mathrm{AU}$. The occurrence of these wide-orbit gas giants should be relatively low, since their core must attain sufficient mass to accrete gas before the pebble flux decays while avoiding excessive migration. Since these gas giants do not reach the pebble isolation mass, their heavy element content is typically less than $10\,M_{\oplus}$. Our results imply that the observed gaps in protoplanetary disks could be caused by distant protoplanets that reached the pebble isolation mass and then migrated, while gas giants in wide orbits, such as PDS 70 b and c, accreted their gas after the decay in the pebble flux.

Planetary Radio Interferometry and Doppler Experiment (PRIDE) is a multi-purpose experimental technique aimed at enhancing the science return of planetary missions. The technique exploits the science payload and spacecraft service systems without requiring a dedicated onboard instrumentation or imposing on the existing instrumentation any special for PRIDE requirements. PRIDE is based on the near-field phase-referencing Very Long Baseline Interferometry (VLBI) and evaluation of the Doppler shift of the radio signal transmitted by spacecraft by observing it with multiple Earth-based radio telescopes. The methodology of PRIDE has been developed initially at the Joint Institute for VLBI ERIC (JIVE) for tracking the ESA's Huygens Probe during its descent in the atmosphere of Titan in 2005. From that point on, the technique has been demonstrated for various planetary and other space science missions. The estimates of lateral position of the target spacecraft are done using the phase-referencing VLBI technique. Together with radial Doppler estimates, these observables can be used for a variety of applications, including improving the knowledge of the spacecraft state vector. The PRIDE measurements can be applied to a broad scope of research fields including studies of atmospheres through the use of radio occultations, the improvement of planetary and satellite ephemerides, as well as gravity field parameters and other geodetic properties of interest, and estimations of interplanetary plasma properties. This paper presents the implementation of PRIDE as a component of the ESA's Jupiter Icy Moons Explorer (JUICE) mission.

We report Chandra-ACIS observations of SN 2023ixf in M101 on day 13 and 86 since the explosion. The X-ray emission in both epochs are characterized by a high temperature plasma from the forward shocked region as a result of circumstellar interaction. We are able to constrain the absorption column density at both the Chandra epochs. The column density is much larger than that of the Galactic absorption column, and we attribute it to absorption by circumstellar matter. Combining this with the NuSTAR published measurement on day 4, we show that the column density declines as $t^{-2}$ between day 4 to day 13 and then evolves as $t^{-1}$. The unabsorbed $0.3-10$ keV luminosity also evolves as $t^{-1}$ during the Chandra epochs. At the first Chandra epoch we detect the Fe K-$\alpha$ fluorescent line at 6.4 keV indicating presence of cold material in the vicinity of the SN. The line is absent on day 86, consistent with the decreased column density by a factor of 7 between the two epochs. Our analysis indicates that during 10 years to 1.5 years before explosion, the progenitor was evolving with a constant mass-loss rate of $5.6\times 10^{-4}$ $M_\odot\,\rm yr^{-1}$. The X-ray measurements indicate asymmetry in the CSM.

The $230$\,GHz lightcurves of Sagittarius~A* (Sgr~A*) predicted by general relativistic magnetohydrodynamics and ray-tracing (GRRT) models in \citet{2022ApJ...930L..16E} have higher modulation index $M_{\Delta T}$ compared to observations. In this series of papers, we explore the origin of such large brightness variability. In this first paper, we performed large GRRT parameter surveys that span from the optically thin to the optically thick regimes, covering $R_{\rm Low}$ from $1$ to $60$. We find, depending on the model parameters that \emph{i}) increasing $R_{\rm Low}$ to a higher value could systematically reduce $M_{\Delta T}$, with $M_{\Delta T}$ consistent with the observed variability of Sgr~A* in some cases; and \emph{ii}) increasing $R_{\rm Low}$ would make $M_{\Delta T}$ increase to a higher value. Our analysis of GRRT image snapshots unravels the large $M_{\Delta T}$ for the $R_{\rm Low} = 1$ models mainly comes from the photon rings. However, secondary contributions from the accretion flow are also visible depending on the spin parameter. Our work demonstrates the importance of the electron temperature used for modelling radiatively inefficient accretion flows and places new constraints on the ion-electron temperature ratio. A more in-depth analysis for understanding the dependencies of $M_{\Delta T}$ on $R_{\rm Low}$ will be performed in subsequent papers.

We perform an improvement in a thermodynamical consistent model with density dependent quark masses ($m'_{u,d,s}$) by introducing effects of quark confinement/deconfinement phase transition, at high density regime and zero temperature, by means of the traced Polyakov loop ($\Phi$). We use realistic values for the current quark masses, provided by the Particle Data Group, and replace the constants of the interacting part of $m'_{u,d,s}$ by functions of $\Phi$, leading to a first order phase transition structure, for symmetric and stellar quark matter, with $\Phi$ being the order parameter. We show that the improved model points out the direction of the chiral symmetry restoration due to the emergence of a deconfined phase. In another application, we construct quark stars mass-radius profiles, obtained from this new model, and show to be possible to satisfy recent astrophysical observational data coming from the LIGO and Virgo Collaboration, and the NICER mission concerning the millisecond pulsars PSR J0030+0451, and PSR J0740+6620.

The CMB-S4 experiment is developing next-generation ground-based microwave telescopes to observe the Cosmic Microwave Background with unprecedented sensitivity. This will require an order of magnitude increase in the 100 mK detector count, which in turn increases the demands on the readout system. The CMB-S4 readout will use time division multiplexing (TDM), taking advantage of faster switches and amplifiers in order to achieve an increased multiplexing factor. To facilitate the design of the new readout system, we have developed a model that predicts the bandwidth and noise performance of this circuity and its interconnections. This is then used to set requirements on individual components in order to meet the performance necessary for the full system. We present an overview of this model and compare the model results to the performance of both legacy and prototype readout hardware.

In this work, we discuss the determination of the distance to the Large Magellanic Cloud (LMC) using the Leavitt Law, utilizing the public catalog of Classical Cepheid Variable stars from the observational project OGLE-IV (The Optical Gravitational Lensing Experiment Collection of Variable Stars), consisting of 4709 stars in the Large Magellanic Cloud. To determine the pulsation period of Cepheid Variable stars, we employ the computational algorithm \textit{Lomb-Scargle periodogram} modified for our data. Additionally, with the calculation of the period, we can derive a period-luminosity relation for Cepheid Variables in the Large Magellanic Cloud and, using an independent calibration distance, deduce their distance moduli. We also discuss some general theoretical concepts of the physical mechanism behind the oscillation of variable stars.

Semi-numerical models of reionization typically involve a large number of unknown parameters whose values are constrained by comparing with observations. Increasingly often, exploring this parameter space using semi-numerical simulations can become computationally intensive, thus necessitating the use of emulators. In this work, we present a likelihood emulator based on Gaussian Process Regression (GPR) for our semi-numerical reionization code, SCRIPT, and use it for parameter inference using mock 21 cm power spectrum data and Bayesian MCMC analysis. A unique aspect of our methodology is the utilization of coarse resolution simulations to identify high-probability regions within the parameter space, employing only a moderate amount of computational time. Samples drawn from these high-probability regions are used to construct the training set for the emulator. The subsequent MCMC using this GPR-trained emulator is found to provide parameter posteriors that agree reasonably well with those obtained using conventional MCMC. The computing time for the analysis, which includes both generation of training sets and training the emulator, is reduced by approximately an order of magnitude. This methodology is particularly advantageous in scenarios where one wants to use different parametrizations of reionization models and/or needs to start with broad prior distributions on the parameters, offering an efficient and effective means of parameter inference.

Spinning neutron stars, when observed as pulsars, are seen to undergo occasional spin-up events known as glitches. Despite several decades of study, the physical mechanisms responsible for glitches are still not well understood, but probably involve an interplay between the star's outer elastic crust, and the superfluid and superconducting core that lies within. Glitches will be accompanied by some level of gravitational wave emission. In this article, we review and critique proposed models that link gravitational wave emission to glitches, exploring both short duration burst-like emission, and longer-lived signals. We illustrate how detections (and in some cases, non-detections) of gravitational signals probe both the glitch mechanism, and, by extension, the behaviour of matter at high densities.

Internal dynamics and kinematics of galaxies have imprints on the line-of-sight velocity distribution~(LOSVD). Gauss-Hermite parametrisation allows one to identify the kinematics features of the system in terms of skewness~($h_3$) and broadness~($h_4$) deviations of a LOSVD. Such a method provides information about the type of orbits since a $h_3-\overline V$ correlation is a sign of elongated orbits, and the anti-correlation is a sign of circular or near-circular orbits. In previous works, analysis of the $h_3-\overline V$ relation provided a tool to identify a hidden bar or B/PS bulge~(edge-on, $\mathrm{PA}=90^\circ$) and to probe their strength. We prepared two $N$-body galaxy models with clear B/PS bulges: one has an ordinary bar~(the X model), and the second one has a barlens embedded into a bar~(the BL model) to investigate the mechanism of formation of $h_3$ features at any position of an observer. We show that the $h_3-\overline V$ correlation appears in the regions where bar and disc particles are mixing. We also reveal that the model with a barlens has an $h_3-\overline V$ anti-correlation in the centre, and we show that barlens-specific orbits are responsible for this signal. Moreover, this feature can be observed only for galaxies with compact bulges and barlenses. The results of this work are applicable for the interpretation of future Integral-field unit (IFU) data for real galaxies with B/PS bulges, especially for objects with barlenses.

We explore the reach of analytical models at one-loop in Perturbation Theory (PT) to accurately describe measurements of the galaxy power spectrum from numerical simulations in redshift space. We consider the validity range in terms of three different diagnostics: 1) the goodness of fit; 2) a figure-of-bias quantifying the error in recovering the fiducial value of a cosmological parameter; 3) an internal consistency check of the theoretical model quantifying the running of the model parameters with the scale cut. We consider different sets of measurements corresponding to an increasing cumulative simulation volume in redshift space. For each volume we define a median value and the associated scatter for the largest wavenumber where the model is valid (the $k$-reach of the model). We find, as a rather general result, that the median value of the reach decreases with the simulation volume, as expected since the smaller statistical errors provide a more stringent test for the model. This is true for all the three definitions considered, with the one given in terms of the figure-of-bias providing the most stringent scale cut. More interestingly, we find as well that the error associated with the $k$-reach value is quite large, with a significant probability of being as low as 0.1$\, h \, {\rm Mpc}^{-1}$ (or, more generally, up to 40% smaller than the median) for all the simulation volumes considered. We explore as well the additional information on the growth rate parameter encoded in the power spectrum hexadecapole, compared to the analysis of monopole and quadrupole, as a function of simulation volume. While our analysis is, in many ways, rather simplified, we find that the gain in the determination of the growth rate is quite small in absolute value and well within the statistical error on the corresponding figure of merit.

Cir X-1 is a neutron star X-ray binary characterized by strong variations in flux during its eccentric $\sim$16.6 days orbit. There are also strong variations in the spectral state, and historically it has shown both atoll and Z state properties. We observed the source with the Imaging X-ray Polarimetry Explorer during two orbital segments, 6 days apart, for a total of 263~ks. We find an X-ray polarization degree in these segments of $1.6\%\pm0.3\%$ and $1.4\%\pm0.3\%$ at polarization angles of $37^\circ\pm5^\circ$ and $-12^\circ\pm7^\circ$, respectively. Thus we observed a rotation of the polarization angle by $49^\circ\pm8^\circ$ along the orbit. Because variations of accretion flow, and then of the hardness ratio, are expected during the orbit, we also studied the polarization binned in hardness ratio, and found the polarization angle differing by $67^\circ\pm11^\circ$ between the lowest and highest values of the hardness ratio. We discuss possible interpretations of this result that could indicate a possible misalignment between the symmetry axes of the accretion disk and the Comptonizing region caused by the misalignment of the neutron star's angular momentum with respect to the orbital one.

Despite the ever-growing number of exoplanets discovered and the extensive analyses carried out to find their potential satellites, only two exomoon candidates, Kepler-1625b-i and Kepler-1708 b-i, have been discovered to date. A considerable amount of effort has been invested in the development of algorithms for modelling, searching, and detecting exomoons in exoplanetary light curves. In this work, we incorporate moon handling capabilities into the state-of-the-art and publicly available code, the Transit and Light Curve Modeller (TLCM). The code is designed for the analysis of transiting exoplanet systems with the inclusion of a wavelet-based noise handling algorithm. Here we present an updated version of TLCM that is capable of modelling a coplanar planet-moon system on an elliptical orbit around its host, accounting for mutual eclipses between the two bodies (and neglecting perturbative effects) -- a so-called photodynamic model. The key benefit of this framework is the ability for a joint analysis of multiple planet-moon transits. We demonstrate the necessity of this software on a case study of Kepler-1625b. Similarly to prior works, we conclude that there is no firm evidence of an exomoon in that system, by showing that temporally correlated noise can mimic apparent lunar transits.

The recently discovered super-Earth LP 890-9 c is an intriguing target for atmospheric studies as it transits a nearby, low-activity late-type M-dwarf star at the inner edge of the Habitable Zone. Its position at the runaway greenhouse limit makes it a natural laboratory to study the climate evolution of hot rocky planets. We present the first 3D-GCM exo-Venus model for a modern Venus-like atmosphere (92 bar surface pressure, realistic composition, H$_2$SO$_4$ radiatively-active clouds), applied to the tidally-locked LP 890-9c to inform observations by JWST and future instruments. If LP 890-9 c has developed into a modern exo-Venus, then the modelled temperatures suggest that H$_2$SO$_4$ clouds are possible even in the substellar region. Like on modern Venus, clouds on LP 890-9 c would create a flat spectrum. The strongest CO$_2$ bands in transmission predicted by our model for LP 890-9 c are about 10 ppm, challenging detection, given JWST estimated noise floor. Estimated phase curve amplitudes are 0.9 and 2.4 ppm for continuum and CO$_2$ bands, respectively. While pointing out the challenge to characterise modern exo-Venus analogues, these results provide new insights for JWST proposals and highlight the influence of clouds in the spectrum of hot rocky exoplanet spectra.

Ongoing observing projects like the James Webb Space Telescope (JWST) and future missions offer the chance to characterize Earth-like exoplanetary atmospheres. Thereby, M-dwarfs are preferred targets for transit observations, for example, due to their favorable planet-star contrast ratio. However, the radiation and particle environment of these cool stars could be far more extreme than what we know from the Sun. Thus, knowing the stellar radiation and particle environment and its possible influence on detectable biosignatures - particularly signs of life like ozone and methane - is crucial to understanding upcoming transit spectra. In this study, with the help of our unique model suite INCREASE, we investigate the impact of a strong stellar energetic particle event on the atmospheric ionization, neutral and ion chemistry, and atmospheric biosignatures of TRAPPIST-1e. Therefore, transit spectra for six scenarios are simulated. We find that a Carrington-like event drastically increases atmospheric ionization and induces substantial changes in ion chemistry and spectral transmission features: all scenarios show high event-induced amounts of nitrogen dioxide (i.e., at 6.2 $\mu$m), a reduction of the atmospheric transit depth in all water bands (i.e., at 5.5 -- 7.0 $\mu$m), a decrease of the methane bands (i.e., at 3.0 -- 3.5 $\mu$m), and depletion of ozone (i.e., at $\sim$ 9.6 $\mu$m). Therefore, it is essential to include high-energy particle effects to correctly assign biosignature signals from, e.g., ozone and methane. We further show that the nitric acid feature at 11.0 - 12.0 $\mu$m, discussed as a proxy for stellar particle contamination, is absent in wet-dead atmospheres.

Accreting neutron stars (NSs) represent a unique laboratory for probing the physics of accretion in the presence of strong magnetic fields ($B\gtrsim 10^8$ G). Additionally, the matter inside the NS itself exists in an ultra-dense, cold state that cannot be reproduced in Earth-based laboratories. Hence, observational studies of these objects are a way to probe the most extreme physical regimes. Here we present an overview of the field and discuss the most important outstanding problems related to NS accretion. We show how these open questions regarding accreting NSs in both low-mass and high-mass X-ray binary systems can be addressed with the High-Energy X-ray Probe (HEX-P) via simulated data. In particular, with the broad X-ray passband and improved sensitivity afforded by a low X-ray background, HEX-P will be able to 1) distinguish between competing continuum emission models; 2) provide tighter upper limits on NS radii via reflection modeling techniques that are independent and complementary to other existing methods; 3) constrain magnetic field geometry, plasma parameters, and accretion column emission patterns by characterizing fundamental and harmonic cyclotron lines and exploring their behavior with pulse phase; 4) directly measure the surface magnetic field strength of highly magnetized NSs at the lowest accretion luminosities; as well as 5) detect cyclotron line features in extragalactic sources and probe their dependence on luminosity in the super-Eddington regime in order to distinguish between geometrical evolution and accretion-induced decay of the magnetic field. In these ways HEX-P will provide an essential new tool for exploring the physics of NSs, their magnetic fields, and the physics of extreme accretion.

Some He-rich hot subdwarf stars (He-sdOBs) present high abundances of trans-iron elements, such as Sr, Y, Zr and Pb. Diffusion processes are important in hot subdwarf stars, and it is thought that the high abundances of heavy elements in these stars are due to the action of radiative levitation. However, during the formation of He-sdOBs, hydrogen can be ingested into the convective zone driven by the He-core flash. It is known that episodes in which protons are being ingested into He-burning convective zones can lead to neutron-capture processes and the formation of heavy elements. In this work we aim to explore for the first time if neutron-capture processes can occur in late He-core flashes happening in the cores of the progenitors of He-sdOBs. We compute a detailed evolutionary model of a stripped red-giant star with a stellar evolution code with a nuclear network comprising 32 isotopes. Then we post-process the stellar models in the phase of He and H burning with a post-processing nucleosynthesis code with a nuclear network of 1190 species that allows us to follow the neutron-capture processes in detail. We find the occurrence of neutron-capture processes in our model, with neutron densities reaching a value of $\sim5\times10^{12}\,{\rm cm}^{-3}$. We find that the trans-iron elements are enhanced in the surface by 1 to 2 dex as compared to initial compositions. Moreover, the relative abundance pattern $[{\rm X}_i/\rm{Fe}]$ produced by neutron-capture processes closely resembles those observed in some He-sdOBs, hinting at a possible self-synthesized origin of the heavy elements in these stars. We conclude that intermediate neutron-capture processes can occur during a proton ingestion event in the He-core flash of stripped red-giant stars. This mechanism offers a natural channel to produce the heavy elements observed in some of the He-sdOBs.

CONCERTO (CarbON CII line in post-rEionization and ReionizaTiOn) is a low-resolution Fourier transform spectrometer dedicated to the study of star-forming galaxies and clusters of galaxies in the transparent millimeter windows from the ground. It is characterized by a wide instantaneous 18.6 arcmin field of view, operates at 130-310 GHz, and was installed on the 12-meter Atacama Pathfinder Experiment (APEX) telescope at 5100 m above sea level. CONCERTO's double focal planes host two arrays of 2152 kinetic inductance detectors and represent a pioneering instrument to meet a state-of-the-art scientific challenge. This paper introduces the CONCERTO instrument and explains its status, shows the first CONCERTO spectral maps of Orion, and describes the perspectives of the project.

The International Liquid Mirror Telescope (ILMT) has recently become operational at the Devasthal Observatory of ARIES, Nainital, India. The ILMT observes in the Time delay integration (TDI) mode where the images are formed by electronically stepping the charges over the pixels of the CCD, along a column. Observations near the zenith impose certain constraints dependent on the latitude such as image deformation due to the star-trail curvature and differential speed. These effects make the stellar trajectories in the focal plane of the ILMT to be hyperbolic, which are corrected for by the introduction of a TDI optical corrector, designed specifically for the ILMT. Here, we report the first results on the effect of this corrector on the trajectories followed by the stars in the ILMT focal plane. Astrometrically calibrating nine nights of data recorded with the ILMT during its first commissioning phase, we find simple (nearly linear) relations between the CCD-y coordinate and the right ascension (RA) of stars and between the CCD-x coordinate and their declination (DEC), respectively, which confirms that the TDI corrector works very fine in converting the stellar trajectories into straight lines.

The International Liquid Mirror Telescope (ILMT) is a 4-meter survey telescope continuously observing towards the zenith in the SDSS g', r', and i' bands. This survey telescope is designed to detect various astrophysical transients (for example, supernovae) and very faint objects like multiply-imaged quasars and low surface brightness galaxies. A single scan of a 22$'$ strip of sky contains a large amount of photometric information. To process this type of data, it becomes critical to have tools or pipelines that can handle it efficiently and accurately with minimal human biases. We offer a fully automated pipeline generated in Python to perform aperture photometry over the ILMT data acquired with the CCD in Time Delayed Integration (TDI) mode. The instrumental magnitudes are calibrated with respect to the Pan-STARRS-1 catalogue. The light curves generated from the calibrated magnitudes will allows us to characterize the objects as variable stars or rapidly decaying transients.

In the era of sky surveys like Palomar Transient Factory (PTF), Zwicky Transient Facility (ZTF) and the upcoming Vera Rubin Observatory (VRO) and ILMT, a plethora of image data will be available. ZTF scans the sky with a field of view of 48 deg$^{2}$ and VRO will have a FoV of 9.6 deg$^{2}$ but with a much larger aperture. The 4m ILMT covers a 22$'$ wide strip of the sky. Being a zenith telescope, ILMT has several advantages like low observation air mass, best image quality, minimum light pollution and no pointing time loss. Transient detection requires all these imaging data to be processed through a Difference Imaging Algorithm (DIA) followed by subsequent identification and classification of transients. The ILMT is also expected to discover several known and unknown astrophysical objects including transients. Here, we propose a pipeline with an image subtraction algorithm and a convolutional neural network (CNN) based automated transient discovery and classification system. The pipeline was tested on ILMT data and the transients as well as variable candidates were recovered and classified.

The 4m International Liquid Mirror Telescope (ILMT) continuously scans a 22$'$ wide strip of the zenithal sky and records the images in three broadband filters (g', r' and i') using a 4K$\times$4K CCD camera. In about 10--12 hours of observations during a single night, $\sim$15 GB of data volume is generated. The raw images resulting from the observations in October--November 2022 have been pre-processed and astrometrically calibrated. In order to exploit the scientific capabilities of the ILMT survey data by the larger scientific community, we are disseminating the raw data (along with dark and flat fields) and the astrometrically calibrated data. These data sets can be downloaded by the users to conduct the scientific projects of their interest. In future, the data will be processed in near real-time and will be available via the ARIES data archive portal.

A very unique strength of the Devasthal Observatory is its capability of detecting optical transients with the 4-m International Liquid Mirror Telescope (ILMT) and to rapidly follow them up using the 1.3-m Devasthal Fast Optical Telescope (DFOT) and/or the 3.6-m Devasthal Optical Telescope (DOT), installed right next to it. In this context, we have inspected 20 fields observed during 9 consecutive nights in October-November 2022 during the first commissioning phase of the ILMT. Each of these fields has an angular extent of $22^\prime$ in declination by $9 \times 22^\prime$ in right ascension. Combining both a visual search for optical transients and an automatic search for these using an image subtraction technique (see the ILMT poster paper by Pranshu et al.), we report a total of 232 significant transient candidates. After consulting the Minor Planet Center database of asteroids, we could identify among these 219 positions of known asteroids brighter than $V=22$. These correspond to the confirmed positions of 78 distinct known asteroids. Analysis of the remaining CCD frames covering 19 more fields (out of 20) should lead to an impressive number of asteroids observed in only 9 nights. The conclusion is that in order to detect and characterize new supernovae, micro-lensing events, highly variable stars, multiply imaged quasars, etc. among the ILMT optical transients, we shall first have to identify all known and new asteroids. Thanks to its large diameter and short focal length (f/D $\sim$ 2.4), the ILMT turns out to be an excellent asteroid hunter.

Ultraluminous X-ray sources (ULXs) represent an extreme class of accreting compact objects: from the identification of some of the accretors as neutron stars to the detection of powerful winds travelling at 0.1-0.2 c, the increasing evidence points towards ULXs harbouring stellar-mass compact objects undergoing highly super-Eddington accretion. Measuring their intrinsic properties, such as the accretion rate onto the compact object, the outflow rate, the masses of accretor/companion -- hence their progenitors, lifetimes, and future evolution -- is challenging due to ULXs being mostly extragalactic and in crowded fields. Yet ULXs represent our best opportunity to understand super-Eddington accretion physics and the paths through binary evolution to eventual double compact object binaries and gravitational wave sources. Through a combination of end-to-end and single-source simulations, we investigate the ability of HEX-P to study ULXs in the context of their host galaxies and compare it to XMM-Newton and NuSTAR, the current instruments with the most similar capabilities. HEX-P's higher sensitivity, which is driven by its narrow point-spread function and low background, allows it to detect pulsations and broad spectral features from ULXs better than XMM-Newton and NuSTAR. We describe the value of HEX-P in understanding ULXs and their associated key physics, through a combination of broadband sensitivity, timing resolution, and angular resolution, which make the mission ideal for pulsation detection and low-background, broadband spectral studies.

We construct simulated galaxy data sets based on the High Energy X-ray Probe (HEX-P) mission concept to demonstrate the significant advances in galaxy science that will be yielded by the HEX-P observatory. The combination of high spatial resolution imaging ($<$20 arcsec FWHM), broad spectral coverage (0.2-80 keV), and sensitivity superior to current facilities (e.g., XMM-Newton and NuSTAR) will enable HEX-P to detect hard (4-25 keV) X-ray emission from resolved point-source populations within $\sim$800 galaxies and integrated emission from $\sim$6000 galaxies out to 100 Mpc. These galaxies cover wide ranges of galaxy types (e.g., normal, starburst, and passive galaxies) and properties (e.g., metallicities and star-formation histories). In such galaxies, HEX-P will: (1) provide unique information about X-ray binary populations, including accretor demographics (black hole and neutron stars), distributions of accretion states and state transition cadences; (2) place order-of-magnitude more stringent constraints on inverse Compton emission associated with particle acceleration in starburst environments; and (3) put into clear context the contributions from X-ray emitting populations to both ionizing the surrounding interstellar medium in low-metallicity galaxies and heating the intergalactic medium in the $z > 8$ Universe.

The hard X-ray emission from magnetars and other isolated neutron stars remains under-explored. An instrument with higher sensitivity to hard X-rays is critical to understanding the physics of neutron star magnetospheres and also the relationship between magnetars and Fast Radio Bursts (FRBs). High sensitivity to hard X-rays is required to determine the number of magnetars with hard X-ray tails, and to track transient non-thermal emission from these sources for years post-outburst. This sensitivity would also enable previously impossible studies of the faint non-thermal emission from middle-aged rotation-powered pulsars (RPPs), and detailed phase-resolved spectroscopic studies of younger, bright RPPs. The High Energy X-ray Probe (HEX-P) is a probe-class mission concept that will combine high spatial resolution X-ray imaging ($<5$ arcsec half-power diameter (HPD) at 0.2--25 keV) and broad spectral coverage (0.2--80 keV) with a sensitivity superior to current facilities (including XMM-Newton and NuSTAR). HEX-P has the required timing resolution to perform follow-up observations of sources identified by other facilities and positively identify candidate pulsating neutron stars. Here we discuss how HEX-P is ideally suited to address important questions about the physics of magnetars and other isolated neutron stars.

Constraining the primary growth channel of supermassive black holes (SMBH) remains one the most actively debated questions in the context of cosmological structure formation. Owing to the expected connection between SMBH spin parameter evolution and the accretion and merger history of individual black holes, population spin measurements offer a rare observational window into the SMBH cosmic growth. As of today, the most common method for estimating SMBH spin relies on modeling the relativistically broaden atomic profiles in the reflection spectrum observed in X-rays. In this paper, we study the observational requirements needed to confidently distinguish between the primary SMBH growth channels, based on their distinct spin-mass distributions predicted by the Horizon-AGN cosmological simulation. In doing so, we characterize outstanding limitations associated with the existing measurements and discuss the landscape of future observational campaigns, which can be planned and executed with future X-ray observatories. We focus our attention on the High-Energy X-ray Probe (HEX-P), a concept probe-class mission aimed to serve the high-energy community in the 2030s.

Both observational evidence and theoretical considerations from MHD simulations of jets suggest that the relativistic jets of active galactic nuclei (AGN) are radially stratified, with a fast inner spine surrounded by a slower-moving outer sheath. The resulting relativistic shear layers are a prime candidate for the site of relativistic particle acceleration in the jets of AGN and gamma-ray bursts (GRBs). In this article, we present outcomes of particle-in-cell simulations of magnetic-field generation and particle acceleration in the relativistic shear boundary layers (SBLs) of jets in AGN and GRBs. We investigate the effects of inverse Compton cooling on relativistic particles that are accelerated in the SBLs of relativistic jets including the self-consistent calculation of the radiation spectrum produced by inverse Compton scattering of relativistic electrons in an isotropic external soft photon field. We find that the Compton cooling can be substantial, depending on the characteristic energy (blackbody temperature and energy density) of the external radiation field. The produced Compton emission is highly anisotropic and more strongly beamed along the jet direction than the characteristic $1/\Gamma$ pattern expected from intrinsically isotropic emission in the comoving frame of an emission region moving along the jet with bulk Lorentz factor $\Gamma$. We suggest that this may resolve the long-standing problem of the Doppler Factor Crisis.

Measurements of the current expansion rate of the Universe, $H_0$, using standard candles, disagree with those derived from observations of the Cosmic Microwave Background (CMB). This discrepancy, known as the \emph{Hubble tension}, is substantial and suggests the possibility of revisions to the standard cosmological model (Cosmological constant $\Lambda$ and cold dark matter - LCDM). Dynamic dark energy (DE) models that introduce deviations in the expansion history relative to LCDM could potentially explain this tension. We used Type Ia supernovae (SNe) data to test a dynamic DE model consisting of an equation of state that varies linearly with the cosmological scale factor $a$. To evaluate this model, we developed a new statistic (the \ta\ statistic) used in conjunction with an optimization code that minimizes its value to obtain model parameters. The \ta\ statistic reduces bias errors (in comparison to the $\chi^2$ statistic) because it retains the sign of the residuals, which is meaningful in testing the dynamic DE model as the deviations in the expansion history introduced by this model act asymmetrically in redshift space. The DE model fits the SNe data reasonably well, but the available SNe data lacks the statistical power to discriminate between LCDM and alternative models. To further assess the model using CMB data, we computed the distance to the last scattering surface and compared the results with that derived from the \emph{Planck} observations. Although the simple dynamic DE model tested does not completely resolve the tension, it is not ruled out by the data and could still play a role alongside other physical effects.

To better understand the mixing and mass loss experienced by low-mass stars as they ascend the asymptotic giant branch (AGB), I have gathered from the literature the abundances of CNO and s-process elements in post-AGB stars in Galactic globular clusters. These species are mixed to the surface during third dredge-up (3DU) events, so their abundance should increase as the star ascends the AGB. Of the 17 stars in this sample, CNO abundances are available for 11. Of these, four are enhanced in CNO relative to the RGB stars from which they descended, which I take as evidence of 3DU on the AGB. The enhancement is mainly in the form of carbon. Of the six stars for which only heavy-element abundances are available, one shows s-process enhancements that previous authors have interpreted as evidence of 3DU. Combining these 17 stars with other recent samples reveals that most globular-cluster post-AGB stars have luminosities log (L/L_sun) ~ 3.25. They are the progeny of blue horizontal-branch (HB) stars in clusters with intermediate metallicity ([Fe/H] ~ -1.5). A second group consists of sub-luminous stars associated with high-metallicity clusters ([Fe/H] ~ -1.0) with red HBs. They may be burning helium, rather than hydrogen. A third group of hot, super-luminous stars is evolving quickly across the Hertzsprung-Russell diagram. Some of them may be merger remnants.

Accretion is a universal astrophysical process that plays a key role in cosmic history, from the epoch of reionization to galaxy and stellar formation and evolution. Accreting stellar-mass black holes in X-ray binaries are one of the best laboratories to study the accretion process and probe strong gravity -- and most importantly, to measure the angular momentum, or spin, of black holes, and its role as a powering mechanism for relativistic astrophysical phenomena. Comprehensive characterization of the disk-corona system of accreting black holes, and their co-evolution, is fundamental to measurements of black hole spin. Here, we use simulated data to demonstrate how key unanswered questions in the study of accreting stellar-mass black holes will be addressed by the {\it High Energy X-ray Probe} (\hexp). \hexp\ is a probe-class mission concept that will combine high spatial resolution X-ray imaging and broad spectral coverage ($0.2\mbox{--}80$keV) with a sensitivity superior to current facilities (including \xmm\ and \nustar) to enable revolutionary new insights into a variety of important astrophysical problems. We illustrate the capability of \hexp\ to: 1) measure the evolving structures of black hole binary accretion flows down to low ($\lesssim0.1\%$) Eddington-scaled luminosities via detailed X-ray reflection spectroscopy; 2) provide unprecedented spectral observations of the coronal plasma, probing its elusive geometry and energetics; 3) perform detailed broadband studies of stellar mass black holes in nearby galaxies, thus expanding the repertoire of sources we can use to study accretion physics and determine the fundamental nature of black holes; and 4) act as a complementary observatory to a range of future ground and space-based astronomical observatories, thus providing key spectral measurements of the multi-component emission from the inner accretion flows of BH-XRBs.

The large-scale gaseous shocks in the bulge of M31 can be naturally explained by a rotating stellar bar. We use gas dynamical models to provide an independent measurement of the bar pattern speed in M31. The gravitational potentials of our simulations are from a set of made-to-measure models constrained by stellar photometry and kinematics. If the inclination of the gas disk is fixed at $i = 77^{\circ}$, we find that a low pattern speed of $16-20\;\rm km\;s^{-1}\;kpc^{-1}$ is needed to match the observed position and amplitude of the shock features, as shock positions are too close to the bar major axis in high $\Omega_{b}$ models. The pattern speed can increase to $20-30\;\rm km\;s^{-1}\;kpc^{-1}$ if the inner gas disk has a slightly smaller inclination angle compared with the outer one. Including sub-grid physics such as star formation and stellar feedback has minor effects on the shock amplitude, and does not change the shock position significantly. If the inner gas disk is allowed to follow a varying inclination similar to the HI and ionized gas observations, the gas models with a pattern speed of $38\;\rm km\;s^{-1}\;kpc^{-1}$, which is consistent with stellar-dynamical models, can match both the shock features and the central gas features.

A fraction of the active supermassive black holes at the centers of galaxies in our Universe are capable of launching extreme kiloparsec-long relativistic jets. These jets are known multiband (radio to $\gamma$-ray) and multimessenger (neutrino) emitters, and some of them have been monitored over several decades at all accessible wavelengths. However, many open questions remain unanswered about the processes powering these highly energetic phenomena. These jets intrinsically produce soft-to-hard X-ray emission that extends from $E\sim0.1\,\rm keV$ up to $E>100\,\rm keV$. Simultaneous broadband X-ray coverage, combined with excellent timing and imaging capabilities, is required to uncover the physics of jets. Indeed, truly simultaneous soft-to-hard X-ray coverage, in synergy with current and upcoming high-energy facilities (such as IXPE, COSI, CTAO, etc.) and neutrino detectors (e.g., IceCube), would enable us to disentangle the particle population responsible for the high-energy radiation from these jets. A sensitive hard X-ray survey ($F_{8-24\,\rm keV}<10^{-15}\,\rm erg~cm^{-2}~s^{-1}$) could unveil the bulk of their population in the early Universe. Acceleration and radiative processes responsible for the majority of their X-ray emission would be pinned down by microsecond timing capabilities at both soft and hard X-rays. Furthermore, imaging jet structures for the first time in the hard X-ray regime could unravel the origin of their high-energy emission. The proposed Probe-class mission concept High Energy X-ray Probe (HEX-P) combines all these required capabilities, making it the crucial next-generation X-ray telescope in the multi-messenger, time-domain era. HEX-P will be the ideal mission to unravel the science behind the most powerful accelerators in the universe.

The Equation of State (EOS) of dense strongly-interacting matter can be probed by astrophysical observations of neutron stars (NS), such as X-ray detections of pulsars or the measurement of the tidal deformability of NSs during the inspiral stage of NS mergers. These observations constrain the EOS at most up to the density of the maximum-mass configuration, $n_\textrm{TOV}$, which is the highest density that can be explored by stable NSs for a given EOS. However, under the right circumstances, binary neutron star (BNS) mergers can create a postmerger remnant that explores densities above $n_\textrm{TOV}$. In this work, we explore whether the EOS above $n_\textrm{TOV}$ can be measured from gravitational-wave or electromagnetic observations of the postmerger remnant. We perform a total of twenty-five numerical-relativity simulations of BNS mergers for a range of EOSs and find no case in which different descriptions of the matter above $n_{\rm TOV}$ have a detectable impact on postmerger observables. Hence, we conclude that the EOS above $n_\textrm{TOV}$ can likely not be probed through BNS merger observations for the current and next generation of detectors.

In the era of multi-messenger astronomy, early classification of photometric alerts from wide-field and high-cadence surveys is a necessity to trigger spectroscopic follow-ups. These classifications are expected to play a key role in identifying potential candidates that might have a corresponding gravitational wave (GW) signature. Machine learning classifiers using features from parametric fitting of light curves are widely deployed by broker software to analyze millions of alerts, but most of these algorithms require as many points in the filter as the number of parameters to produce the fit, which increases the chances of missing a short transient. Moreover, the classifiers are not able to account for the uncertainty in the fits when producing the final score. In this context, we present a novel classification strategy that incorporates data-driven priors for extracting a joint posterior distribution of fit parameters and hence obtaining a distribution of classification scores. We train and test a classifier to identify kilonovae events which originate from binary neutron star mergers or neutron star black hole mergers, among simulations for the Zwicky Transient Facility observations with 19 other non-kilonovae-type events. We demonstrate that our method can estimate the uncertainty of misclassification, and the mean of the distribution of classification scores as point estimate obtains an AUC score of 0.96 on simulated data. We further show that using this method we can process the entire alert steam in real-time and bring down the sample of probable events to a scale where they can be analyzed by domain experts.

HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging ($<10"$ FWHM) and broad spectral coverage (0.2-80 keV) with an effective area far superior to current facilities' (including XMM-Newton and NuSTAR). These capabilities will enable revolutionary new insights into a variety of important astrophysical problems. We present scientific objectives and simulations of HEX-P observations of the Galactic Center (GC) and Bulge. We demonstrate the unique and powerful capabilities of the HEX-P observatory for studying both X-ray point sources and diffuse X-ray emission. HEX-P will be uniquely equipped to explore a variety of major topics in Galactic astrophysics, allowing us to (1) investigate broad-band properties of X-ray flares emitted from the supermassive black hole (BH) at Sgr A* and probe the associated particle acceleration and emission mechanisms; (2) identify hard X-ray sources detected by NuSTAR and determine X-ray point source populations in different regions and luminosity ranges; (3) determine the distribution of compact object binaries in the nuclear star cluster and the composition of the Galactic Ridge X-ray emission; (4) identify X-ray transients and measure fundamental parameters such as BH spin; (5) find hidden pulsars in the GC; (6) search for BH-OB binaries and hard X-ray flares from young stellar objects in young massive clusters; (7) measure white dwarf (WD) masses of magnetic CVs to deepen our understanding of CV evolution and the origin of WD magnetic fields; (8) explore primary particle accelerators in the GC in synergy with future TeV and neutrino observatories; (9) map out cosmic-ray distributions by observing non-thermal X-ray filaments; (10) explore past X-ray outbursts from Sgr A* through X-ray reflection components from giant molecular clouds.

Non-negative matrix factorization (NMF) is a dimensionality reduction technique that has shown promise for analyzing noisy data, especially astronomical data. For these datasets, the observed data may contain negative values due to noise even when the true underlying physical signal is strictly positive. Prior NMF work has not treated negative data in a statistically consistent manner, which becomes problematic for low signal-to-noise data with many negative values. In this paper we present two algorithms, Shift-NMF and Nearly-NMF, that can handle both the noisiness of the input data and also any introduced negativity. Both of these algorithms use the negative data space without clipping, and correctly recover non-negative signals without any introduced positive offset that occurs when clipping negative data. We demonstrate this numerically on both simple and more realistic examples, and prove that both algorithms have monotonically decreasing update rules.

HEX-P will launch at a time when the sky is being routinely scanned for transient gravitational wave, electromagnetic and neutrino phenomena that will require the capabilities of a sensitive, broadband X-ray telescope for follow up studies. These include the merger of compact objects such as neutron stars and black holes, stellar explosions, and the birth of new compact objects. \hexp\ will probe the accretion and ejecta from these transient phenomena through the study of relativistic outflows and reprocessed emission, provide unique capabilities for understanding jet physics, and potentially revealing the nature of the central engine.

The PRobe far-Infrared Mission for Astrophysics (PRIMA) is working to develop kinetic inductance detectors (KIDs) that can meet the sensitivity targets of a far-infrared spectrometer on a cryogenically cooled space telescope. An important ingredient for achieving high sensitivity is increasing the fractional-frequency responsivity. Here we present a study of the responsivity of aluminum KIDs fabricated at the Jet Propulsion Laboratory. Specifically, we model the KID's temporal response to pair-breaking excitations in the framework of the Mattis-Bardeen theory, incorporating quasiparticle recombination dynamics and the pair-breaking efficiency. Using a near-IR laser, we measure time-resolved photon pulses and fit them to our model, extracting the time-resolved quasiparticle density and the quasiparticle recombination lifetime. Comparing the fit to the known energy of the laser provides a measurement of the pair-breaking efficiency. In addition to photon-sourced excitations, it is important to understand the KID's response to phonon-sourced excitations from cosmic rays. We measure the rate of secondary cosmic rays detected by our devices, and predict the dead time due to cosmic rays for an array in L2 orbit. This work provides confidence in KIDs' robustness to cosmic ray events in the space environment.

We examine the relationship between metallicity and $J-K$ color for 64 benchmark late-M and L dwarfs, all of which are wide companions to higher mass stars, and 6 of which are new discoveries. We assess the correlation between the $\Delta(J-K)$ color anomaly (the difference of an object's $J-K$ color with the median color for field objects of the same spectral type) and the host star metallicity to investigate how metallicity affects ultracool photospheres. Using Spearman's rank correlation test and Student's t test, the late-M dwarf (L dwarf) sample's $\Delta(J-K)$ and metallicity show a positive correlation with 95\% (90\%) confidence level. A linear fit to color anomaly as a function of metallicity finds a slope of $0.17\pm0.07$ for the late-M dwarfs and a slope of $0.20^{+0.07}_{-0.08}$ for the L dwarfs. We also computed the $\Delta(J-K)$ versus metallicity relationship predicted by multi-metallicity model spectra generated using Drift-Phoenix. The modeled late-M dwarfs show a slope of 0.202$\pm$0.03, which is close to our observational results, but the modeled L dwarfs show a slope of 0.493$\pm$0.02, steeper than our observational results. Both our empirical results and the models indicate that more metal-rich objects should appear redder photometrically. We speculate that higher metallicity drives more condensate formation in these atmospheres, thus making these ultracool dwarfs appear redder.

Rapid identification of the optical counterparts of Neutron Star (NS) merger events discovered by gravitational wave detectors may require observing a large error region and sifting through a large number of transients to identify the object of interest. Given the expense of spectroscopic observations, a question arises: How can we utilize photometric observations for candidate prioritization, and what kinds of photometric observations are needed to achieve this goal? NS merger kilonova exhibits low ejecta mass (~5x10^-2 solar mass) and a rapidly evolving photospheric radius (with a velocity ~0.2c). As a consequence, these sources display rapid optical-flux evolution. Indeed, selection based on fast flux variations is commonly used for young supernovae and NS mergers. In this study, we leverage the best currently available flux-limited transient survey - the Zwicky Transient Facility Bright Transient Survey - to extend and quantify this approach. We focus on selecting transients detected in a 3-day cadence survey and observed at a one-day cadence. We explore their distribution in the phase space defined by g-r, g-dot, and r-dot. Our analysis demonstrates that for a significant portion of the time during the first week, the kilonova AT 2017gfo stands out in this phase space. It is important to note that this investigation is subject to various biases and challenges; nevertheless, it suggests that certain photometric observations can be leveraged to identify transients with the highest probability of being fast-evolving events. We also find that a large fraction (~0.75) of the transient candidates with |g-dot|>0.7 mag/day, are cataclysmic variables or active galactic nuclei with radio counterparts.

We report the discovery of a large-scale structure at z=3.44 revealed by JWST data in the EGS field. This structure, dubbed "Cosmic Vine", consists of 20 galaxies with spectroscopic redshifts at 3.43<z<3.45 and six galaxy overdensities with consistent photometric redshifts, making up a vine-like structure extending over a ~4x0.2 pMpc^2 area. The two most massive galaxies (M*~10^10.9 Msun) of the Cosmic Vine are found to be quiescent with bulge-dominated morphologies (B/T>70%). Comparisons with simulations suggest that the Cosmic Vine would form a cluster with halo mass >10^14 Msun at z=0, and the two massive galaxies are likely forming the brightest cluster galaxies (BCGs). The results unambiguously reveal that massive quiescent galaxies can form in growing large-scale structures at z>3, thus disfavoring the environmental quenching mechanisms that require a virialized cluster core. Instead, as suggested by the interacting and bulge-dominated morphologies, the two galaxies are likely quenched by merger-triggered starburst or AGN feedback before falling into a cluster core. Moreover, we found that the observed specific star formation rates of massive quiescent galaxies in z>3 dense environments are two orders of magnitude lower than that of the BCGs in the TNG300 simulation. This discrepancy potentially poses a challenge to the models of massive cluster galaxy formation. Future studies comparing a large sample with dedicated cluster simulations are required to solve the problem.

The CHIME radio telescope operates in the frequency bandwidth of 400 to 800 MHz. The CHIME/FRB collaboration has a data pipeline that analyzes the data in real time, suppresses radio frequency interferences (RFI) and searches for FRBs. However, the RFI removal techniques work best for broadband and narrow FRBs.We wish to create a RFI removal technique that works without making assumptions about the characteristics of the FRB signal. In this thesis we first explore the data of intensity generated by CHIME/FRB backend. After becoming familiar with the structure and organisation of data we present a new novel method for RFI removal using unsupervised machine learning clustering techniques by using multiple beams on CHIME telescope. We are trying to use the analogy of theory of interference for RFI removal by distinguishing near field RFI and far field astrophysical signals in the data. We explored many clustering techniques like K-means,DBSCAN etc but one technique called as HDBSCAN looks particularly promising. Using HDBSCAN clustering technique we have developed the new method for RFI removal. The removal technique upto this point has been developed by us using 3 beams of CHIME telescope. The new novel idea is still in it's incubatory phase and soon we will try to include more beams for our new RFI removal method. We have visually observed that RFI has been been considerably removed from our data. In future we are going to do more calculations to further measure the signal to noise ratio (SNR) of the FRB signal after RFI removal and we will use this technique to compare the SNR measured by current RFI removal technique at CHIME/FRB data pipeline.

The Galactic black hole GRS 1915+105 exhibits generic High-Frequency Quasi-periodic Oscillations (HFQPOs) at $\sim$ 67 Hz only during the radio-quiet 'softer' variability classes. We present the time-lag properties associated with HFQPOs in the wide energy band (3$-$60 keV) using all AstroSat observations. For the first time, we detect soft-lag of 6$-$25 keV band w.r.t 3$-$6 keV band for all 'softer' variability classes ($\delta$, $\omega$, $\kappa$ and $\gamma$). Moreover, our findings reveal that soft-lag increases gradually with the energy of the photons. These features are entirely opposite to the previous report of hard-lag obtained with the RXTE observations. The energy-dependent time-lag study exhibits a maximum soft-lag of $\sim$ 3 ms and $\sim$ 2.5 ms for the $\delta$ and $\omega$ classes respectively, whereas the $\kappa$ and $\gamma$ classes both exhibit a maximum soft-lag of $\sim$ 2.1 ms. We find a coherent lag-energy correlation for all four variability classes, where the amplitude of soft-lag increases with energy and becomes maximum at $\sim$ 18 keV. We interpret this observed soft-lag as the reflection of hard photons in the 'cooler' accretion disc. A generic lag-rms correlation implies that the soft-lag increases with the rms amplitude of the HFQPO. The wideband (0.7$-$50 keV) spectral study suggests a high value of the optical depth ($\tau$ $\sim$ 6.90$-$12.55) of the Comptonized medium and the magnitude of the soft-lag increases linearly with the increase in optical depth ($\tau$). We explain the observed time-lag features at the HFQPOs in the context of a possible accretion disc scenario.

In this work, we update and develop algorithms for KMTNet tender-love care (TLC) photometry in order to create an new, mostly automated, TLC pipeline. We then start a project to systematically apply the new TLC pipeline to the historic KMTNet microlensing events, and search for buried planetary signals. We report the discovery of such a planet candidate in the microlensing event MOA-2019-BLG-421/KMT-2019-BLG-2991. The anomalous signal can be explained by either a planet around the lens star or the orbital motion of the source star. For the planetary interpretation, despite many degenerate solutions, the planet is most likely to be a Jovian planet orbiting an M or K dwarf, which is a typical microlensing planet. The discovery proves that the project can indeed increase the sensitivity of historic events and find previously undiscovered signals.

We investigate how the properties of massive black hole binaries influence the observed properties of core galaxies. We compare the observed trend in stellar mass deficit as a function of total stellar mass in the core galaxy with predicted trends in IllustrisTNG. We calculate mass deficits in simulated galaxies by applying sub-grid, post-processing physics based on the results of literature N-body experiments. We find the median value of the posterior distribution for the minimum binary mass ratio capable of creating a core is 0.7. For the gas mass fraction above which a core is erased we find a median value of 0.6. Thus low mass ratio binaries do not contribute to core formation and gas-rich mergers must lead to star formation within the nucleus, ultimately erasing the core. Such constraints have important implications for the overall massive black hole binary population, black hole-galaxy co-evolution, and the origin of the gravitational wave background.

Primordial non-Gaussianity generated by additional fields present during inflation offers a compelling observational target for galaxy surveys. These fields are of significant theoretical interest since they offer a window into particle physics in the inflaton sector. They also violate the single-field consistency conditions and induce a scale-dependent bias in the galaxy power spectrum. In this paper, we explore this particular signal for light scalar fields and study the prospects for measuring it with galaxy surveys. We find that the sensitivities of current and future surveys are remarkably stable for different configurations, including between spectroscopic and photometric redshift measurements. This is even the case at non-zero masses where the signal is not obviously localized on large scales. For realistic galaxy number densities, we demonstrate that the redshift range and galaxy bias of the sample have the largest impact on the sensitivity in the power spectrum. These results additionally motivated us to explore the potentially enhanced sensitivity of Vera Rubin Observatory's LSST through multi-tracer analyses. Finally, we apply this understanding to current data from the last data release of the Baryon Oscillation Spectroscopic Survey (BOSS DR12) and place new constraints on light fields coupled to the inflaton.

Lightcurves of many classical novae deviate from the canonical "fast rise - smooth decline" pattern and display complex variability behavior. We present the first TESS-space-photometry-based investigation of this phenomenon. We use TESS Sector 41 full-frame images to extract a lightcurve of the slow Galactic nova V606 Vul that erupted nine days prior to the start of the TESS observations. The lightcurve covers the first of two major peaks of V606 Vul that was reached 19 days after the start of the eruption. The nova reached its brightest visual magnitude V=9.9 in its second peak 64 days after the eruption onset, following the completion of Sector 41 observations. To increase the confidence level of the extracted lightcurve, we performed the analysis using four different codes implementing the aperture photometry (Lightkurve, VaST) and image subtraction (TESSreduce, tequila_shots) and find good agreement between them. We performed ground-based photometric and spectroscopic monitoring to complement the TESS data. The TESS lightcurve reveals two features: periodic variations (0.12771d, 0.01mag average peak-to-peak amplitude) that disappeared when the source was within 1mag of peak optical brightness and a series of isolated mini-flares (with peak-to-peak amplitudes of up to 0.5mag) appearing at seemingly random times. We interpret the periodic variations as the result of azimuthal asymmetry of the photosphere engulfing the nova-hosting binary that was distorted by and rotating with the binary. Whereas we use spectra to associate the two major peaks in the nova lightcurve with distinct episodes of mass ejection, the origin of mini-flares remains elusive.

A model of baryogenesis is introduced where our usual visible Universe is a 3-brane coevolving with a hidden 3-brane in a multidimensional bulk. The visible matter and antimatter sectors are naturally coupled with the hidden matter and antimatter sectors, breaking the C/CP invariance and leading to baryogenesis occurring after the quark-gluon era. The issue of leptogenesis is also discussed. The symmetry breaking spontaneously occurs in relation to the presence of an extra scalar field supported by the $U(1)\otimes U(1)$ gauge group, which extends the conventional electromagnetic gauge field in the two-brane universe. Scalar waves also emerge as potential dark matter candidates and a means of constraining the model.

Neutron star binaries and their associated gravitational wave signal facilitate precision tests of General Relativity. Any deviation of the detected gravitational waveform from General Relativity would therefore be a smoking gun signature of new physics, in the form of additional forces, dark matter particles, or extra gravitational degrees of freedom. To be able to probe new theories, precise knowledge of the expected waveform is required. In our work, we consider a generic setup by augmenting General Relativity with an additional, massive scalar field. We then compute the inspiral dynamics of a binary system by employing an effective field theoretical approach, while giving a detailed introduction to the computational framework. Finally, we derive the modified gravitational waveform at next-to-leading order. As a consequence of our model-agnostic approach, our results are readily adaptable to a plethora of new physics scenarios, including modified gravity theories and scalar dark matter models.

We discuss the use of Low Gain Avalanche (LGAD) silicon detectors for two specific applications, namely measuring cosmic rays in space in collaboration with NASA] and beam properties and received doses for patients undergoing cancer treatment in flash beam therapy.

We present a combination of two quick guides aimed at summarizing relevant information about the CompOSE nuclear equation of state repository. The first is aimed at nuclear physicists and describes how to provide standard equation of state tables. The second quick guide is meant for users and describes the basic procedures to obtain customized tables with equation of state data. Several examples are included to help providers and users to understand and benefit from the CompOSE database.

We construct a theoretical framework to interpret the Hubble tension by means of a slow-rolling dynamics of a self-interacting scalar field. In particular, we split the Friedmann equation in order to construct a system for the three unknowns, corresponding to the Hubble parameter $H$, the scalar field $\phi$ and its self-interaction potential $V$, as functions of the redshift. In the resulting picture, the vacuum energy density is provided by a constant term in the potential $V(\phi)$, while the corresponding small kinetic term is responsible for reproducing the apparent variation of the Hubble constant $H_0$ with the redshift. The emerging solution depends on two free parameters, one of which is fixed to account for the discrepancy between the values of $H_0$ as measured by the Super Nova Ia Pantheon sample and the Planck satellite data, respectively. The other parameter is instead determined by a fitting procedure of the apparent Hubble constant variation across the data corresponding to a 40 bin analysis of the Super Nova Pantheon sample, in each of which $H_0$ has been independently determined. The fundamental result of the present analysis is the emerging Hubble parameter as function of the redshift, which correctly takes the Super Nova Ia prediction at $z=0$ and naturally approaches the profile predicted by a flat $\Lambda$CDM model corresponding to the cosmological parameters detected by Planck. It is remarkable that this achievement is reached without reducing the Super Nova Ia data to a single point for determining $H(z=0)$, but accounting for the distribution over their redshift interval of observation, via the binned analysis.