Papers for Thursday, Dec 21 2023

We investigate the detectability of gravitational waves that have been lensed by a spinless stellar-mass black hole, with respect to the advanced LIGO. By solving the full relativistic linear wave equations in the spacetime of a Schwarzschild black hole, we find that the strong gravity can create unique signals in the lensed waveform, particularly during the merger and ringdown stages. The differences in terms of fitting factor between the lensed waveform and best-fitted unlensed general relativity template with spin-precessing and higher-order multipoles are greater than $5\%$ for the lens black hole mass within $70M_{\odot}<M_{\rm lens}<133.33 M_{\odot}$ under advanced LIGO's sensitivity. This is up to 5 times more detectable than the previous analysis based on the weak field approximation for a point mass and covers most part of the black hole mass gap predicted by stellar evolution theory. Based on Bayesian inference, the lensing feature can be distinguished with a signal-to-noise ratio of 12.5 for $M_{\rm lens}=70 M_{\odot}$ and 19.2 for $M_{\rm lens}=250 M_{\odot}$, which is attainable for advanced LIGO.

A simple and minimal extension of the standard cosmological $\Lambda$CDM model in which dark matter experiences an additional long-range scalar interaction is demonstrated to alleviate the long lasting Hubble-tension while letting primordial nucleosynthesis predictions unaffected and passing by construction all current local tests of general relativity. The theoretical formulation of this $\Lambda\beta$CDM model and its comparison to astrophysical observations are presented to prove its ability to fit existing data and potentially resolve the tension.

Many inflationary theories predict a non-Gaussian spectrum of primordial tensor perturbations, sourced from non-standard vacuum fluctuations, modified general relativity or new particles such as gauge fields. Several such models also predict a chiral spectrum in which one polarization state dominates. In this work, we place constraints on the non-Gaussianity and parity properties of primordial gravitational waves utilizing the Planck PR4 temperature and polarization dataset. Using recently developed quasi-optimal bispectrum estimators, we compute binned parity-even and parity-odd bispectra for all combinations of CMB T-, E- and B-modes with $2\leq \ell<500$, and perform both blind tests, sensitive to arbitrary three-point functions, and targeted analyses of a well-motivated equilateral gravitational wave template (sourced by gauge fields), with amplitude $f_{\rm NL}^{ttt}$. This is the first time B-modes have been included in primordial non-Gaussianity analyses; they are found to strengthen constraints on the parity-even sector by $\simeq 30\%$ and dominate the parity-odd bounds, without inducing bias. We report no detection of non-Gaussianity (of either parity), with the template amplitude constrained to $f_{\rm NL}^{ttt}=900\pm 700$ (stable with respect to a number of analysis variations), compared to $1300\pm1200$ in Planck 2018. The methods applied herein can be reapplied to upcoming CMB datasets such as LiteBIRD, with the inclusion of B-modes poised to dramatically improve future bounds on tensor non-Gaussianity.

Early matter-dominated eras (EMDEs) are a natural feature arising in many models of the early universe and can generate a stochastic gravitational wave background (SGWB) during the transition from an EMDE to the radiation-dominated universe required by the time of Big Bang Nucleosynthesis. While there are calculations of the SGWB generated in the linear regime, no detailed study has been made of the nonlinear regime. We perform the first comprehensive calculation of GW production in the nonlinear regime, using a hybrid $N$-body and lattice simulation to study GW production from both a metastable matter species and the radiation produced in its decay. We find that nonlinearities significantly enhance GW production up to frequencies at least as large as the inverse light-crossing time of the largest halos that form prior to reheating. The resulting SGWB is within future observational reach for curvature perturbations as small as those probed in the cosmic microwave background, depending on the reheating temperature. Out-of-equilibrium dynamics could further boost the induced SGWB, while a fully relativistic gravitational treatment is required to resolve the spectrum at even higher frequencies.

We present a new galaxy cluster search in the COSMOS field through the use of the Adaptive Matched Identifier of Clustered Objects (AMICO). We produced a new cluster and group catalogue up to $z=2$, by performing an innovative application of AMICO with respect to previous successful applications to wide-field surveys, in terms of depth (down to $r < 26.7$), small area covered ($1.69 deg^2$ of unmasked area) and redshift extent. This sample, and the comparative analysis we performed with the X-rays, allowed for the calibration of mass-proxy scaling relations up to $z=2$ and down to less than $10^{13} M_{sun}$ and constitutes the base for the refinement of the cluster model for future applications of AMICO, like the analysis of upcoming Euclid data. AMICO is based on an optimal linear matched filter and detects clusters in photometric galaxy catalogues using galaxy location, photometric redshift and, in the simplest case, one galaxy property. We used one magnitude as galaxy property, avoiding explicit use of galaxy colour, and performed 3 independent runs in the r, Y and H bands using both COSMOS2020 and COSMOS2015 galaxy catalogues. The final catalogue resulting from matching the results of the three runs contains 1269 and 666 candidate clusters with $S/N >3.0$ and $>3.5$, respectively. Most of the unmatched ones have $S/N <3.5$ which can be chosen as cut for a more robust sample. We assigned X-ray properties to our detections via matching with a public X-ray group sample and by estimating, for unmatched detections, X-ray properties at the location of AMICO candidates based on Chandra+XMM-Newton data. 622 are the candidates with X-ray flux estimate. This large sample allowed for the calibration of the scaling relations between AMICO mass-proxies and X-ray mass and the study of their redshift dependence for the selection of the most stable photometric bands.

The streaming instability (SI) is a leading candidate for planetesimal formation, which can concentrate solids through two-way aerodynamic interactions with the gas. The resulting concentrations can become sufficiently dense to collapse under particle self-gravity, forming planetesimals. Previous studies have carried out large parameter surveys to establish the critical particle to gas surface density ratio ($Z$), above which SI-induced concentration triggers planetesimal formation. The threshold $Z$ depends on the dimensionless stopping time ($\tau_s$, a proxy for dust size). However, these studies neglected both particle self-gravity and external turbulence. Here, we perform 3D stratified shearing box simulations with both particle self-gravity and turbulent forcing, which we characterize via $\alpha_D$ that measures turbulent diffusion. We find that forced turbulence, at amplitudes plausibly present in some protoplanetary disks, can increase the threshold $Z$ by up to an order of magnitude. For example, for $\tau_s = 0.01$, planetesimal formation occurs when $Z \gtrsim 0.06$, $\gtrsim 0.1$, and $\gtrsim 0.2$ at $\alpha_D = 10^{-4}$, $10^{-3.5}$, and $10^{-3}$, respectively. We provide a single fit to the critical $Z$ as a function of $\alpha_D$ and $\tau_s$ required for the SI to work (though limited to the range $\tau_s = 0.01$--0.1). Our simulations also show that planetesimal formation requires a mid-plane particle-to-gas density ratio that exceeds unity, with the critical value being independent of $\alpha_D$. Finally, we provide the estimation of particle scale height that accounts for both particle feedback and external turbulence.

We identify 182 flares on 158 stars within 100 pc of the Sun in both the near-ultraviolet (NUV: 1750-2750 \r{A}) and far-ultraviolet (FUV: 1350-1750 \r{A}) using high-cadence light curves from the Galaxy Evolution Explorer (GALEX). Ultraviolet (UV) emission from stellar flares plays a crucial role in determining the habitability of exoplanetary systems. However, whether such UV emission promotes or threatens such life depends strongly on the energetics of these flares. Most studies assessing the effect of flares on planetary habitability assume a 9000 K blackbody spectral energy distribution that produces more NUV flux than FUV flux ($R \equiv F_{\rm FUV} / F_{\rm NUV} \approx \frac{1}{6}$). Instead, we observe the opposite with the excess FUV reaching $R \approx \frac{1}{2} - 2$, roughly $3-12$ times the expectation of a 9000 K blackbody. The ratio of FUV to NUV time-integrated flare energies is 3.0 times higher on average than would be predicted by a constant 9000 K blackbody during the flare. Finally, we find that the FUV/NUV ratio at peak tentatively correlates ($\sim 2 \sigma$ significance) both with total UV flare energy and with the G - RP color of the host star. On average, we observe higher FUV/NUV ratios at peak in $E_{\text{UV}}>10^{32}$ erg flares and in flares on fully convective stars.

We describe a custom outlier rejection algorithm for JWST/NIRSpec integral field spectroscopy. This method uses a layered sigma clipping approach that adapts clipping thresholds based upon the spatial profile of the science target. We find that this algorithm produces a robust outlier rejection while simultaneously preserving the signal of the science target. Originally developed as a response to unsatisfactory initial performance of the jwst pipeline outlier detection step, this method works either as a standalone solution, or as a supplement to the current pipeline software. Comparing leftover (i.e., not flagged) artifacts with the current pipeline's outlier detection step, we find that our method results in one fifth as many residual artifacts as the jwst pipeline. However, we find a combination of both methods removes nearly all artifacts -- an approach that takes advantage of both our algorithm's robust outlier rejection and the pipeline's use of individual dithers. This combined approach is what the TEMPLATES Early Release Science team has converged upon for our NIRSpec observations. Finally, we publicly release the code and Jupyter notebooks for the custom outlier rejection algorithm.

Mass loss plays a crucial role in the lives of massive stars, especially as the star leaves the main sequence and evolves to the red supergiant (RSG) phase. However, the physical processes that trigger mass-loss events in RSGs are not well understood. Recently, we showed that adding a static wind to a MARCS atmospheric model can accurately reproduce observed extensions in the atmospheres of RSGs. In this work, we compute synthetic observables that match new interferometric data of the RSGs AH Sco, KW Sgr, V602 Car, CK Car, and V460 Car obtained with VLTI/MATISSE and GRAVITY. We computed model spectra and visibilities and found the best-fit model, mass-loss rate, and best-fit angular Rosseland diameter for the observations. We matched our model to the data, covering a wavelength range of $1.8-5.0\,\mu$m, which corresponds to the $K$, $L,$ and $M$ bands. Our models reproduce the spectro-interferometric data over this wide wavelength range, including extended atmospheric layers of CO, H$_2$O, and SiO. We obtain Rosseland angular diameters between $3.0<\theta_{\mathrm{Ross}}<5.5$ mas and mass-loss rates of $-6.5<\log \dot{M}/M_{\odot}\mathrm{yr}^{-1}<-4$. The partial pressure of SiO relative to the gas pressure and the SiO 4.0$\,\mu$m line intensity increase between 2 and 3 stellar radii. The relative intensity depends on the luminosity used for our models, since the more luminous models have a higher mass-loss rate. This work further demonstrates that our MARCS+wind model can reproduce the observed physical extension of RSG atmospheres for several spectral diagnostics spanning a broad wavelength range. We reproduce both spectra and visibilities of newly obtained data as well as provide temperature and density stratifications that are consistent with the observations. With the MATISSE data, we newly include the extension of SiO layers as a precursor of silicate dust.

The halo of the Milky Way galaxy hosts multiple dynamically coherent substructures known as stellar streams that are remnants of tidally disrupted systems such as globular clusters (GCs) and dwarf galaxies (DGs). A particular case is that of the Jhelum stream, which is known for its complex morphology. Using the available data from Gaia DR3, we extracted a region on the sky that contains Jhelum. We then applied the novel Locally Aligned Ant Technique (LAAT) on the position and proper motion space of stars belonging to the selected region to highlight the stars that are closely aligned with a local manifold in the data and the stars belonging to regions of high local density. We find that the overdensity representing the stream in proper motion space is composed of two components, and show the correspondence of these two signals to the previously reported narrow and broad spatial components of Jhelum. We made use of the radial velocity measurements provided by the $S^5$ survey to confirm, for the first time, a separation between the two components in radial velocity. We show that the narrow and broad components have velocity dispersions of $4.84^{+1.23}_{-0.79}$~km/s and $19.49^{+2.19}_{-1.84}$~km/s, and metallicity dispersions of $0.15^{+0.18}_{-0.10}$ and $0.34^{+0.13}_{-0.09}$, respectively. These measurements, and the difference in component widths, could be explained with a scenario where Jhelum is the remnant of a GC embedded within a DG that were accreted onto the Milky Way during their infall. Although the properties of Jhelum can be explained with this merger scenario, other progenitors of the narrow component remain possible such as a nuclear star cluster or a DG. To rule these possibilities out, we would need more observational data of member stars of the stream. Our analysis highlights the importance of the internal structure of streams with regards to their formation history.

The theoretical oscillation frequencies of even the best asteroseismic models of solar-like oscillators show significant differences from observed oscillation frequencies. Structure inversions seek to use these frequency differences to infer the underlying differences in stellar structure. While used extensively to study the Sun, structure inversion results for other stars have so far been limited. Applying sound-speed inversions to more stars allows us to probe stellar theory over a larger range of conditions, as well as look for overall patterns that may hint at deficits in our current understanding. To that end, we present structure inversion results for 12 main-sequence solar-type stars with masses between 1M$_\odot$ and 1.15M$_\odot$. Our inversions are able to infer differences in the isothermal sound speed in the innermost 30% by radius of our target stars. In half of our target stars, the structure of our best-fit model fully agrees with the observations. In the remainder, the inversions reveal significant differences between the sound-speed profile of the star and that of the model. We find five stars where the sound speed in the core of our stellar models is too low and one star showing the opposite behavior. For the two stars which our inversions reveal the most significant differences, we examine whether changing the microphysics of our models improves them and find that changes to nuclear reaction rates or core opacities can reduce, but do not fully resolve, the differences.

We explore the mass content of galaxies residing in galaxy clusters at z=0 in the EAGLE hydrodynamical simulation as well as the galaxies' mass build-up through cosmic time. We use a galaxy catalogue generated with the HBT+ algorithm, which identifies subhaloes consistently over time by tracking their dynamical evolution throughout the simulation. The satellite subhalo-to-stellar mass relation (SHSMR) is well described by a double power-law. At stellar masses $9<\log m_\star/\mathrm{M}_\odot<10$, satellites have 20-25% the subhalo mass of central galaxies at fixed stellar mass. At high stellar masses the satellite SHSMR is consistent with that of centrals. The satellite SHSMR decreases steeply for satellites closer to the cluster centre, even in projection, broadly consistent with recent weak lensing measurements. The scatter in the satellite SHSMR is larger than that of central galaxies at all cluster masses and cluster-centric distances $R<R_\mathrm{200m}$. The SHSMR scatter decreases with stellar mass by about 12% over an order of magnitude, but this dependence can be explained by the mixing of infall times. There is significant dark matter preprocessing; the most recent infallers into massive clusters had already lost up to 50% of their dark matter by the time of infall, particularly if they fell in indirectly as satellites of another host. On the contrary, on average satellite galaxies are still gaining stellar mass at the time of infall and they do so for another 2 Gyr afterwards, although we see evidence of a slowing growth for indirect infallers. Overall, pre- and post-processing each have similar impacts on the satellite SHSMR. Finally, we provide a simple prescription to infer the mean mass loss experienced by satellites as a function of cluster-centric distance based on a comparison to central galaxies, convenient for observational weak lensing measurements. [abridged]

We present a detailed long-term study of the single M6 III giant RZ~Ari to obtain direct and simultaneous measurements of the magnetic field, activity indicators, and radial velocity in order to infer the origin of its activity. We study its magnetic activity in the context of stellar evolution, and for this purpose, we also refined its evolutionary status and Li abundance. In general, for the M giants, little is known about the properties of the magnetic activity and its causes. RZ~Ari posses the strongest surface magnetic field of the known Zeeman-detected M giants and is bright enough to allow a deep study of its surface magnetic structure. The results are expected to shed light on the activity mechanism in these stars.

One of the longstanding goals in the framework of inflation is the construction of tools that can be used to classify models in theory space. An idea that has been put forward in this context is to consider the energy dependent scaling behavior of observables to characterize different models. We implement this approach in the framework of hilltop and hilltop-squared inflation by analyzing their observables when the small-field approximation is not imposed and the energy scale $\mu$ of these models is varied as a free parameter, subject to observational constraints. We show that the scalar spectral tilt and the tensor ratio $r$ exhibit $\mu$-dependent scaling behavior and that the scaling exponents as functions of $\mu$ in turn lead to functional forms that are model dependent. Scaling relations of the type discussed here are of interest as characteristics of the inflationary theory space as well as in the context of the post-inflationary reheating process. We further observe a bifurcation behavior in the behavior of $p$-families in the spectral-tensor plane for a critical value of $\mu$.

Quasi-periodic oscillations (QPOs) have been detected in many Fermi-detected bright blazars. In this letter, we report multiple QPOs detected in a non-blazar AGN PKS 0521-36 searched over the entire 15 years of Fermi-LAT data. QPOs are detected at 268 days, at 295 days, and at 806 days timescales with more than 3$\sigma$ significance. The QPO detected at 806 days happens to be the third harmonic of QPO at 268 days. The time scales are consistent in both Lomb-Scargle and Wavelet analysis. Furthermore, the Gaussian Process modeling of the light curve is performed with stochastically driven damped harmonic oscillator (SHO) and damped random walk (DRW) modeling to uncover the presence of QPOs. The constructed power spectral density (PSD) exhibits two QPOs, with observed timescales of approximately 283 days and 886 days. This is the first non-blazar AGN where the long-term QPO is detected. Earlier studies show this source has a weak beamed jet. The exact cause for these QPOs remains unclear. We also assembled the $\gamma$-ray QPO detected in various blazar and tested the QPO time scale dependent on the black hole mass. No significant correlation is found.

Molecular emission from the galactic and extragalactic interstellar medium (ISM) is often used to determine the physical conditions of the dense gas. However, even from spatially resolved regions, the observed molecules are not necessarily arising from a single component. Disentangling multiple gas components is often a degenerate problem in radiative transfer studies. In this paper we investigate the use of the non-negative matrix factorization (NMF) approach as a means to recover gas components from a set of blended line intensity maps of molecular transitions which may trace different physical conditions. We run a series of experiments on synthetic datasets designed to replicate conditions in two very different environments: galactic pre-stellar cores and the ISM in high redshift galaxies. We find that the NMF algorithm often recovers the multiple components resembling those used in the data-generating process, provided that the different components have similar column densities. When NMF fails to recover all the individual components it does however group together the most similarly emitting ones. We further found that initialisation and regularisation are key factors in the efficiency of the NMF algorithm.

The majority of massive stars are formed in multiple systems and will interact with companions via mass transfer. This interaction typically leads to the primary shedding its envelope and the formation of a "stripped star". Classically, stripped stars are expected to quickly contract to become hot UV-bright helium stars. Surprisingly, recent optical surveys have unveiled a large number of stripped stars that are larger and cooler, appearing "puffed-up" and overlapping with the Main Sequence (MS). Here, we study the evolutionary nature and lifetimes of puffed-up stripped (PS) stars using stellar-evolution code MESA. We computed grids of binary models at four metallicities from Z = 0.017 to 0.0017. Contrary to previous assumptions, we find that stripped stars regain thermal equilibrium shortly after the end of mass transfer. Their further contraction is determined by the rate at which the residual H-rich envelope is depleted, with the main agents being H-shell burning (dominant) and mass-loss in winds. The duration of the PS star phase is 1$\%$ of the total lifetime and up to 100 times more than thermal timescale. We explored several relevant factors: orbital period, mass ratio, winds, and semiconvection. We carried out a simple population estimation, finding that $\sim$0.5-0.7 $\%$ of all the stars with $\log (L/L_{\rm \odot}$) $>$ 3.7 are PS stars. Our results indicate that tens to hundred of PS stars may be hiding in the MS population, disguised as normal stars: $\sim$100 in the Small Magellanic Cloud alone. Their true nature may be revealed by low surface gravities, high N enrichment, and likely slow rotations

WDS 03286+2523 BRT 133, is a double-star system that has been under observation since 1896. In this study, we present new measurements of the position angle and separation of the system, utilizing data obtained from a web telescope with a Charged Couple Device (CCD) camera, Gaia EDR3, and historical records. We determined that the position angle and separation are 222.4{\deg} and 5.35", respectively, indicating a slight increase from the previous values of 222{\deg} and 5.34" measured in 2004. We also employed the parallax and the ratio of proper motion metric (rPM) values of the system to assess its binarity. This analysis showed that the system may be gravitationally bound and with a long orbital period.

Accurate atomic data and plasma models are essential for interpreting the upcoming high-quality spectra from missions like XRISM and Athena. Estimating physical quantities, like temperature, abundance, turbulence, and resonance scattering factor, is highly dependent on the underlying atomic data. We use the AtomDB tool variableapec to estimate the impact of atomic data uncertainties in Einstein A coefficients, collisional rate coefficient, ionization and recombination rates in H-, He- and Li-like iron in modeling the spectrum of Perseus observed by Hitomi. The best-fit temperature, abundance, resonance scattering factor, and turbulence including atomic data uncertainties, varied approximately 17%, 35%, 30%, and 3%, respectively, from the best-fit temperature, abundance, resonance scattering factor, and turbulence estimated without atomic data uncertainties. This indicates that, approximately 32%, 35%, and 25% of the best-fit temperatures, abundances, and resonance scattering factors, including uncertainties lie outside the 3$\sigma$ error regions of their corresponding best-fit values computed with zero atomic data error. Expanding the energy range to 1.8-20.0 keV shows less variability, with 26% of the abundances and 22% of the resonance scattering factors lying outside the 3$\sigma$ error of the best-fit values. We also studied correlations between physical parameters and atomic rate uncertainties to identify key atomic quantities requiring precise lab measurements. We report negative correlations between best-fit temperature and z (1s.2s $^{3}\rm S_{1}\rightarrow 1s^{2}$) collisional rate coefficient, abundance and y (1s.2p $^{3}\rm P_{1}\rightarrow 1s^{2}$) collisional rate coefficient, abundance and z collisional rate coefficient, and positive correlation between resonance scattering factor and w (1s.2p $^{1}\rm P_{1}\rightarrow 1s^{2}$) collisional rate coefficient.

We present spectroscopic data for 16369 stellar targets within and/or toward 38 dwarf spheroidal galaxies and faint star clusters within the Milky Way halo environment. All spectra come from observations with the multi-object, fiber-fed echelle spectrographs M2FS at the Magellan/Clay telescope or Hectochelle at the MMT, reaching a typical limiting magnitude G < 21. Data products include processed spectra from all observations and catalogs listing estimates -- derived from template model fitting -- of line-of-sight velocity (median uncertainty 1.1 km/s) effective temperature (234 K), (base10 logarithm of) surface gravity (0.52 dex in cgs units), [Fe/H] (0.38 dex) and [Mg/Fe] (0.24 dex) abundance ratios. The sample contains multi-epoch measurements for 3720 sources, with up to 15 epochs per source, enabling studies of intrinsic spectroscopic variability. The sample contains 6078 likely red giant stars (based on surface gravity), and 4494 likely members (based on line-of-sight velocity and Gaia-measured proper motion) of the target systems. The number of member stars per individual target system ranges from a few, for the faintest systems, to ~ 850 for the most luminous. For most systems, our new samples extend over wider fields than have previously been observed; of the likely members in our samples, 823 lie beyond twice the projected halflight radius of their host system, and 42 lie beyond 5 Rhalf.

We explore a novel, exotic physics, modality in multi-messenger astronomy. We are interested in exotic fields emitted by the mergers and their direct detection with a network of atomic clocks. We specifically focus on the rubidium clocks onboard satellites of the Global Positioning System. Bursts of exotic fields may be produced during the coalescence of black hole singularities, releasing quantum gravity messengers. To be detectable such fields must be ultralight and ultra-relativistic and we refer to them as exotic low-mass fields (ELFs). Since such fields possess non-zero mass, the ELF bursts lag behind the gravitational waves emitted by the very same merger. Then the gravitational wave observatories provide a detection trigger for the atomic clock networks searching for the feeble ELF signals. ELFs would imprint an anti-chirp transient across the sensor network. ELFs can be detectable by atomic clocks if they cause variations in fundamental constants. We report our progress in the development of techniques to search for ELF bursts with clocks onboard GPS satellites. We focus on the binary neutron star merger GW170817 of August 17, 2017. We find an intriguing excess in the clock noise post LIGO gravitational wave trigger. Potentially the excess noise could be explained away by the increased solar electron flux post LIGO trigger.

We investigate dipole asymmetries in four large radio surveys, each spanning more than 80\% of the sky. Two of them, the Very Large Array Sky Survey (VLASS) and the Rapid ASKAP Continuum Survey (RACS), have recently yielded dipoles that appear incongruent with each other as well as seem inconsistent with previous radio survey dipoles and the Cosmic Microwave Background (CMB) dipole. Because these radio surveys have large overlaps in sky coverage, comprising hence large majority of common radio sources, one would not expect significant differences between their radio dipoles, irrespective of their underlying source of origin. We examine here in detail these radio dipoles, to ascertain the source of incongruency amongst them. We find the VLASS and RACS data to be containing some declination-dependent systematics, seemingly in the vicinity of the declination limit of each survey. We show that the effects of such systematics can be mitigated by restricting the declination limits of the respective survey during the dipole determination. A weighted mean of the sky coordinates of thus derived dipoles from the four radio surveys lies within $1.2\sigma$ of the CMB dipole direction. However, the amplitude appears significantly larger, $3.7\pm 0.6$ times or more than the CMB dipole. This puts in doubt not only the conventional wisdom that the genesis of all these dipoles, including that of the CMB dipole, is due to the Solar peculiar motion, it also raises uncomfortable questions about the Cosmological Principle (CP), the basis of the standard $\Lambda$CDM cosmological model.

We present detailed abundance results based on UVES high dispersion spectra for 7 very and extremely metal-poor stars in the Large Magellanic Cloud. We confirm that all 7 stars, two of which have [Fe/H] $\leq$ --3.0, are the most metal-poor stars discovered so far in the Magellanic Clouds. The element abundance ratios are generally consistent with Milky Way halo stars of similar [Fe/H] values. We find that 2 of the more metal-rich stars in our sample are enhanced in r-process elements. This result is in contrast with Reggiani et al. (2021), where all nine metal-poor LMC stars, which have higher [Fe/H] values than our sample, were found to be r-process element rich. The absence of r-process enrichment in stars with lower [Fe/H] values is consistent with a minimum delay timescale of $\sim$100 Myr for the neutron star binary merger process to generate substantial r-process enhancements in the LMC. We find that the occurrence rate of r-process enhancement (r-I or r-II) in our sample of very and extremely metal-poor stars is statistically indistinguishable from that found in the Milky Way's halo, although including stars from the Reggiani et al (2021) sample hints at a larger r-II frequency the LMC. Overall, our results shed light on the earliest epochs of star formation in the LMC that may be applicable to other galaxies of LMC-like mass.

Bisei town, located in the west part of Japan, is known as a place where the local community protects its beautiful night sky from light pollution through its unique ordinances and the efforts of the local residents. It is also important to monitor in the quantity and quality of light pollution for precise measurement of astronomical observations. The fluorescent lamps in the city were gradually replaced with light emitting diode (LED) lamps. In order to investigate how much light pollution is affecting astronomical observation, we analyzed the archival photometric and spectroscopic data taken by the 101cm telescope that has been installed at Bisei Astronomical Observatory (BAO) since 2006. As a result, we found that there is no significant variability in sky brightness in optical bands, but from spectroscopic observation, we observed a blue humps around 4500 \AA originating from LED lights from 2017 to 2023. The brightness of light pollution observed at BAO is not varied but the origin of light has gradually changed from fluorescent lamps to LED lamps.

Estimating precise metallicity of M dwarfs is a well-known difficult problem due to their complex spectra. In this work, we empirically calibrate the metallicity using wide binaries with a F, G, or K dwarf and a M dwarf companion. With 1308 FGK+M wide binaries well observed by LAMOST, we calibrated M dwarf's [Fe/H] by using the Stellar LAbel Machine (SLAM) model, a data-driven method based on support vector regression (SVR). The [Fe/H] labels of the training data are from FGK companions in range of [-1,0.5] dex. The Teffs are selected from Li et al. (2021), spanning [3100,4400] K. The uncertainties in SLAM estimates of [Fe/H] and Teff are ~0.15 dex and ~40 K, respectively, at snri > 100, where snri is the signal-to-noise ratio (SNR) at i-band of M dwarf spectra. We applied the trained SLAM model to determine the [Fe/H] and Teff for ~630,000 M dwarfs with low-resolution spectra in LAMOST DR9. Compared to other literature also using FGK+M wide binaries for calibration, our [Fe/H] estimates show no bias but a scatter of ~ 0.14-0.18 dex. However, the [Fe/H] compared to APOGEE shows a systematic difference of ~ 0.10-0.15 dex with a scatter of ~ 0.15-0.20 dex. While the Teff compared to APOGEE has a bias of 3 K with a scatter of 62 K, it is systematically higher by 180 K compared to other calibrations based on the bolometric temperature. Finally, we calculated the zeta index for 1308 M dwarf secondaries and presents a moderate correlation between zeta and [Fe/H].

Transition-edge sensors (TESs) are useful devices for detecting photons from sub-millimeter radiation to gamma rays, which is typically operate at a current bias point. The problem of large-scale array applications of TES is the low-temperature multiplexed readout based on superconducting quantum interference device (SQUID). The most mature technology currently is the time-division multiplexing SQUID (TDM). To provide TDM with appropriate current bias, we design a Configurable Ultra-Low Noise Current Source (CLCS), which is based on the feedback structure of ultra-low noise instrumentation amplifiers and low-noise, high-resolution (20 bits) digital-to-analog converter (DAC). The high-impedance output of the CLCS avoids the issue of impedance mismatch. CLCS has an ultra-high resolution of 10 nA in the $0$ to 5 mA current output range. To test the performance of the CLCS, we use three TESs, which have different structure, to conduct I-V testing, and then compare the results with the commercial power supply module SIM928. On the other hand, we compare the output noise level of CLCS with SIM928 and analyze the total system noise at different current bias of TES. All the above measurement and analysis validate that the performance of CLCS meets the experimental requirements.

We present the analysis of new, deep $Chandra$ observations (130~ks) of the galaxy cluster Abell~2495. This object is known for the presence of a triple offset between the peaks of the intracluster medium (ICM), the brightest cluster galaxy (BCG), and the warm gas glowing in H$\alpha$ line. The new $Chandra$ data confirm that the X-ray emission peak is located at a distance of $\sim$6.2 kpc from the BCG, and at $\sim$3.9 kpc from the H$\alpha$ emission peak. Moreover, we identify two generations of X-ray cavities in the ICM, likely inflated by the central radio galaxy activity. Through a detailed morphological and spectral analysis we determine that the power of the AGN outbursts ($P_{cav} = 4.7\pm1.3\times10^{43}$~erg~s$^{-1}$) is enough to counterbalance the radiative losses from ICM cooling ($L_{cool} = 5.7\pm0.1\times10^{43}$~erg~s$^{-1}$). This indicates that, despite a fragmented cooling core, Abell~2495 still harbors an effective feedback cycle. We argue that the offsets are most likely caused by sloshing of the ICM, supported by the presence of spiral structures and a probable cold front in the gas at $\sim$58 kpc east of the center. Ultimately, we find that the outburst interval between the two generations of X-ray cavities is of the order of the dynamical sloshing timescale, as already hinted from the previous $Chandra$ snapshot. We thus speculate that sloshing may be able to regulate the timescales of AGN feedback in Abell~2495, by periodically fuelling the central AGN.

Magnetic reconnection is a fundamental mechanism through which energy stored in magnetic fields is released explosively on a massive scale, they could be presented as eruptive or confined flares, depending on their association with coronal mass ejections (CMEs). Several previous works have concluded that there is no correlation between flare duration and flare class, however, their sample sizes are skewed towards B and C classes; they hardly represent the higher classes. Therefore, we studied a sample without extreme events in order to determine the correlation between flare duration and flare type (confined and eruptive). We examined $33$ flares with classes between M5 to X5 within $45^{\circ}$ of the disk centres, using data from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI). We find that the linear correlation between flare class against flare duration by full width half maximum (FWHM) in general is weak ($r=0.19$); however, confined flares have a significant correlation ($r=0.58$) compared to eruptive types ($r=0.08$). Also, the confined M class flares' average duration is less than half of the eruptive flares. Similarly, confined flares have a higher correlation ($r=0.89$) than eruptive flares ($r=0.60$) between flare classes against magnetic reconnection flux. In this work, a balanced sample size between flare types is an important strategy for obtaining a reliable quantitative comparison.

Using a volume- and mass-limited (D < 30 Mpc, log (M_star/M_sun) $\geq 9.75$) sample of 155 barred S0-Sd galaxies, I determine the fraction with secondary structures within their bars. Some 20 +/- 3% have a separate inner bar, making them double-barred; an identical fraction have nuclear rings, with 11^{+3}_{-2}% hosting both. The inner-bar frequency is a strong, monotonic function of stellar mass: only 4^{+3}_{-2}% of barred galaxies with log (M_star/M_sun) = 9.75-10.25 are double-barred, while 47 +/- 8% of those with log (M_star/M_sun) > 10.5 are. The nuclear-ring frequency is a strong function of absolute bar size: only 1^{+2}_{-1}% of bars with semi-major axes < 2 kpc have nuclear rings, while 39^{+6}_{-5}% of larger bars do. Both inner bars and nuclear rings are absent in very late-type (Scd--Sd) galaxies. Inner bar size correlates with galaxy stellar mass, but is clearly offset to smaller sizes from the main population of bars. This makes it possible to define "nuclear bars" in a consistent fashion, based on stellar mass. There are eight single-barred galaxies where the bars are nuclear-bar-sized; some of these may be systems where an outer bar failed to form, or previously double-barred galaxies where the outer bar has dissolved. Inner bar size is even more tightly correlated with host bar size, which is likely the primary driver. In contrast, nuclear ring size is only weakly correlated with galaxy mass or bar size, with more scatter in size than is true of inner bars.

The upcoming extremely large telescopes will have to deal with the so-called ''pupil fragmentation'' effect: for what concerns the Extremely Large Telescope (ELT), the presence of thick spider legs supporting the secondary mirror may induce unseen phase discontinuities across the pupil sectors that could limit the performance of the adaptive optics correction. In this context, we propose a wavefront sensor (WFS), the CiaoCiao WFS, consisting in a rotational shearing interferometer to sense phase differences between the pupil sectors. In this work, we present the CiaoCiao WFS concept and the first analyses carried out through numerical simulations. In particular, we analyze the performance of such a wavefront sensor in case the phase discontinuities are induced by low-wind effect during observations with the Multiconjugate adaptive Optics Relay For ELT Observations (MORFEO).

We study the formation of primordial black holes (PBH) with ultra-slow-roll inflation when stochastic effects are important. We use the $\Delta N$ formalism and simplify the stochastic equations with an analytical constant-roll approximation. Considering a viable inflation model, we find the spatial profile of the PBH compaction function numerically for each stochastic patch, without assumptions about Gaussianity or the radial profile. The stochastic effects that lead to an exponential tail for the density distribution also make the compaction function very spiky, unlike assumed in the literature. Naively using collapse thresholds found for smooth profiles, the PBH abundance is enhanced by up to a factor of $10^9$, and the PBH mass distribution is spread over three orders of magnitude in mass. The results point to a need to redo numerical simulations of PBH formation with spiky profiles.

Accurate estimation of photometric redshifts (photo-$z$) is crucial in studies of both galaxy evolution and cosmology using current and future large sky surveys. In this study, we employ Random Forest (RF), a machine learning algorithm, to estimate photo-$z$ and investigate the systematic uncertainties affecting the results. Using galaxy flux and color as input features, we construct a mapping between input features and redshift by using a training set of simulated data, generated from the Hubble Space Telescope Advanced Camera for Surveys (HST-ACS) and COSMOS catalogue, with the expected instrumental effects of the planned China Space Station Telescope (CSST). To improve the accuracy and confidence of predictions, we incorporate inverse variance weighting and perturb the catalog using input feature errors. Our results show that weighted RF can achieve a photo-$z$ accuracy of $\rm \sigma_{NMAD}=0.025$ and an outlier fraction of $\rm \eta=2.045\%$, significantly better than the values of $\rm \sigma_{NMAD}=0.043$ and $\rm \eta=6.45\%$ obtained by the widely used Easy and Accurate Zphot from Yale (EAZY) software which uses template-fitting method. Furthermore, we have calculated the importance of each input feature for different redshift ranges and found that the most important input features reflect the approximate position of the break features in galaxy spectra, demonstrating the algorithm's ability to extract physical information from data. Additionally, we have established confidence indices and error bars for each prediction value based on the shape of the redshift probability distribution function, suggesting that screening sources with high confidence can further reduce the outlier fraction.

The nature of the emission region around Sagittarius A* (Sgr A*), the supermassive black hole at the Galactic Center, remains under debate. A prediction of jet models is that a frequency-dependent shift in the position of the radio core (core-shift) of active galactic nucleii occurs when observing emission dominated by a highly collimated relativistic outflow. We use millimeter Very Long Baseline Interferometry to study the frequency-dependent position of Sgr A*'s radio core, estimate the core-shift for different emission models, investigate the core-shift evolution as a function of viewing angle and orientation, and study its behaviour in the presence of interstellar scattering. We simulate images of the emission around Sgr A* for accretion inflow models (disks) and relativistic outflow models (jets). They are based on three-dimensional general relativistic magnetohydrodynamic simulations. We create flux density maps at 22, 43 and 86 GHz sampling different viewing angles and orientations, and examine the effects of scattering. Jet-dominated models show significantly larger core-shifts (in some cases by a factor of 16) than disk-dominated models, intermediate viewing angles (i=30, 45 degrees) show the largest core-shifts. Our jet models follow a power-law relation for the frequency dependent position of Sgr A*'s core. Their core-shifts decrease as the position angle increases from 0 to 90 degrees. Disk models do not fit well a power-law relation and their core-shifts are insensitive to changes in viewing angle. We place an upper limit of 241.65 +-1.93 microarcseconds per cm for the core-shift of jet models including refractive scattering. Our jet models agree with earlier predictions of AGN with conical jets, and the core-shift is retrievable even in the presence of interstellar scattering.

Observational constraints on dust properties in protoplanetary disks are key to better understanding disks' evolution. We continue our exploration of the protoplanetary disk around AB Aur by characterizing its dust properties. We present ALMA observations at 2.2 mm and VLA observations at 6.8 mm. Together with previous ALMA and NOEMA observations at 0.87 and 1.1 mm, these observations are used to compute global spectral index profiles as well as spectral index maps. On the interpretation side, we present the results of a simple isothermal slab model to help constrain dust properties along the ring of continuum emission. We also present results of dust radiative transfer calculations based on a disc-planet hydrodynamical simulation to explain how the azimuthal contrast ratio of the ring emission varies with millimeter wavelength. The spectral energy distribution and the radial profiles of the spectral index indicate that the radiation from the compact source towards the center is not dominated by dust thermal emission, but most likely by free-free emission originating in the radio jet: it constitutes 93% of the emission at 6.8 mm, and 37% at 0.87 mm. The protoplanetary disk has a typical spectral index of 2.3. We estimate a dust disk mass of 8$\rm \times 10^{-5}$ M$\rm _{\odot}$ which, assuming a mean gas-to-dust ratio of 40, gives a total disk mass of 3.2$\rm \times 10^{-3}$ M$\rm _{\odot}$. The azimuthal contrast ratio of the ring outside the millimeter cavity is smaller at 2.2 mm than at 1.1 mm, in agreement with previous findings. The VLA image shows several knots of $5\sigma$ emission all along the ring, which are consistent with the ring emission being nearly axisymmetric at that wavelength. The decrease in the azimuthal contrast ratio of the ring emission from 0.87 to 6.8 mm can be explained by a dust-losing decaying vortex at the outer edge of a planet gap.

The characterization of exoplanetary atmospheres via transit spectroscopy is based on the comparison between the stellar spectrum filtered through the atmosphere and the unadulterated spectrum from the occulted stellar region. The disk-integrated spectrum is often used as a proxy for the occulted spectrum, yet they differ along the transit chord depending on stellar type and rotational velocity. This is refereed to as the Rossiter-McLaughlin (RM) effect, which is known to bias transmission spectra at high spectral resolution when calculated with the disk-integrated stellar spectrum. Recently, it was shown that the first claimed atmospheric signal from an exoplanet cannot arise from absorption in the core of the sodium doublet, because the features observed at high resolution are well reproduced by the RM effect. However, it remains unclear as to whether the detection made at medium spectral resolution with the HST arises from the smoothed RM signature or from the wings of the planetary absorption line. More generally, the impact of the RM effect at medium and low spectral resolution remains poorly explored. To address this question, we simulated realistic transmission spectra in a variety of systems using the EVaporating Exoplanets code. We find that the RM effect should not bias broadband atmospheric features, such as hazes or molecular absorption, measured with the JWST/NIRSPEC (prism mode) at low resolution. However, absorption signatures from metastable helium or sodium measured at medium resolution with the JWST/NIRSPEC (G140H mode) or HST/STIS can be biased, especially for planets on misaligned orbits across fast rotators. In contrast, we show that the Na signature originally reported in HD209458b, an aligned system, cannot be explained by the RM effect, supporting a planetary origin.

Understanding the nature of repeating FRBs is crucial to probe the physics of FRBs. In this work, we analyze the statistics of waiting time between bursts of three repeating FRBs from four data sets. We find a universally pronounced dependency of the waiting times on the previous time interval (denoted as $\lambda_0$). We observe a temporal clustering where short waiting times tend to be followed by short ones, and long by long. This memory dependency is manifested in the conditional mean waiting time as well as in the conditional mean residual time to the next burst, both of which increase in direct proportion to $\lambda_0$. Consequently, the likelihood of experiencing a subsequent FRB burst within a given time window after the preceding burst is significantly influenced by the burst history. We reveal that, for the first time, these memory effects are present in the scale-invariant preconditioned waiting time distribution. We show that the memory effect provides a unified description of waiting times which may account for both the repeating FRBs and the apparent non-repeating FRBs (i.e. only observed one time). These results shed new light on the mechanism of FRBs.

The fluctuations generated by Inflation are Gaussian in the simplest models, but may be non-Gaussian in more complex models. Since these fluctuations seed the large-scale structure, any primordial non-Gaussianity of local type will leave an imprint on the tracer power spectrum on ultra-large scales. In order to combat the problem of growing cosmic variance on these scales, we use a multi-tracer analysis that combines different tracers of the matter distribution to maximise any primordial signal. In order to illustrate the advantages that can be brought by multi-tracing future surveys, we consider two pairs of (galaxy survey, 21cm intensity mapping survey), one at high redshift ($1\le z\le2$) and one at very high redshift ($2\le z\le5$). The 21cm surveys are in interferometer mode, and are idealised versions of HIRAX and PUMA. We implement foreground avoidance filters and use non-trivial models of the interferometer thermal noise. The galaxy surveys are idealised versions of Euclid and MegaMapper. Via a simple Fisher forecast we illustrate the potential of the multi-tracer. Our results show a $\sim 20-70\%$ improvement in precision on local primordial non-Gaussianity from the multi-tracer.

Ultralight axion or axionlike particles are one of the most promising candidates for dark matter because they are a well-motivated solution for the theoretical strong $CP$ problem and observational issues on small scales, i.e. the core-cusp problem and the satellite problem. A tiny coupling of axions and photons induces birefringence. We propose the differential birefringence measurements of multiple images of gravitationally lensed fast radio burst (FRB) systems as probes of the Galactic axion dark matter (ADM) background. In addition to general advantages of lensing systems, i.e. alleviating systematics and intrinsic astrophysical dependencies, precise measurements of lensing time delay and polarization angle in gravitationally lensed FRB systems make them a more robust and powerful probe. We show that, with a single lensed FRB system (which may be detected in large numbers in the SKA era), the axion-photon coupling under the ADM background could be constrained to be $g_{a\gamma} < 7.3 \times 10^{-11}~ \mathrm{GeV^{-1}}$ for an axion mass $m_a\sim10^{-20}~\mathrm{eV}$. This will be of great significance in achieving synergistic searches of the Galactic ADM with other astrophysical probes and laboratorial experiments.

The Laser Interferometer Space Antenna (LISA) is scheduled to launch in the mid 2030s, and is expected to observe gravitational-wave candidates from massive black-hole binary mergers, extreme mass-ratio inspirals, and more. Accurately inferring the source properties from the observed gravitational-wave signals is crucial to maximise the scientific return of the LISA mission. BILBY, the user-friendly Bayesian inference library, is regularly used for performing gravitational-wave inference on data from existing ground-based gravitational-wave detectors. Given that Bayesian inference with LISA includes additional subtitles and complexities beyond it's ground-based counterpart, in this work we modify BILBY to perform parameter estimation with LISA. We show that full nested sampling can be performed to accurately infer the properties of LISA sources from transient gravitational-wave signals in a) zero-noise and b) idealized instrumental noise. By focusing on massive black-hole binary mergers, we demonstrate that higher order multipole waveform models can be used to analyse a year's worth of simulated LISA data, and discuss the computational cost and performance of full nested sampling compared with techniques for optimising likelihood calculations, such as the heterodyned likelihood.

We measure the two point correlation function (CF) of 1357 galaxy clusters with a mass of $\log_{10}{M_{200}}\geq 13.6$~\hm~and at a redshift of $z \leq 0.125$. This work differs from previous analyses in that it utilizes a spectroscopic cluster catalogue, $\mathtt{SDSS-GalWCat}$, to measure the CF and detect the baryon acoustic oscillation (BAO) signal. Unlike previous studies which use statistical techniques, we compute covariance errors directly by generating a set of 1086 galaxy cluster lightcones from the GLAM $N$-body simulation. Fitting the CF with a power-law model of the form $\xi(s) = (s/s_0)^{-\gamma}$, we determine the best-fit correlation length and power-law index at three mass thresholds. We find that the correlation length increases with increasing the mass threshold while the power-law index is almost constant. For $\log_{10}{M_{200}}\geq 13.6$~\hm, we find $s_0 = 14.54\pm0.87$~\h~and $\gamma=1.97\pm0.11$. We detect the BAO signal at $s = 100$~\h~with a significance of $1.60 \sigma$. Fitting the CF with a $\Lambda$CDM model, we find $D_\mathrm{V}(z = 0.089)\mathrm{r}^{fid}_d/\mathrm{r}_d = 267.62 \pm 26$ \h, consistent with Planck 2015 cosmology. We present a set of 108 high-fidelity simulated galaxy cluster lightcones from the high-resolution \U~N-body simulation, employed for methodological validation. We find $D_\mathrm{V}(z = 0.089)/r_d = 2.666 \pm 0.129$, indicating that our method does not introduce any bias in the parameter estimation for this small sample of galaxy clusters.

Ground-based, high-resolution and space-based, low-resolution spectroscopy are the two main avenues through which transiting exoplanet atmospheres are studied. Both methods provide unique strengths and shortcomings, and combining the two can be a powerful probe into an exoplanet's atmosphere. Within a joint atmospheric retrieval framework, we combined JWST NIRSpec/G395H secondary eclipse spectra and Gemini South/IGRINS pre- and post-eclipse thermal eclipse observations of the hot Jupiter WASP-77A b. Our inferences from the IGRINS and NIRSpec data sets are consistent with each other, and combining the two allows us to measure the gas abundances of H$_2$O and CO as well as the vertical thermal structure with higher precision than either data set provided individually. We confirm WASP-77A b's subsolar metallicty ([(C+O)/H]=-0.61$^{+0.10}_{-0.09}$) and solar C/O ratio (C/O = 0.57$^{+0.06}_{-0.06}$). The two types of data are complementary, and our abundance inferences are mostly driven by the IGRINS data while inference of the thermal structure is driven by the NIRSpec data. Our ability to draw inferences from the post-eclipse IGRINS data is highly sensitive to the number of singular values removed in the detrending process, potentially due to high and variable humidity. We also search for signatures for atmospheric dynamics in the IGRINS data and find that propagated ephemeris error can manifest as both an orbital eccentricity or a strong equatorial jet. Neither are detected when using more up-to-date ephemerides. However, we find moderate evidence of thermal inhomogeneity and measure a cooler nightside that presents itself in the later phases after secondary eclipse.

Variable accretion has been well studied in evolved stages of low-mass stars formation. However, the accretion history in the initial phases of star formation is still a seldom studied topic. The outflows and jets emerging from protostellar objects could shed some light onto their accretion history. We consider the recently studied case of W43-MM1, a protocluster containing 46 outflows driven by 27 protostellar cores. The outflow kinematics of the individual cores and associated knots in W43-MM1 indicate episodic protostellar ejection. We took the observed parameters of an individual core system (core #8) and performed 3D hydrodynamic simulations of such system including episodic changes in the velocity of the outflow. The simulations consist of a collimated jet emerging from a core taking into account one- and two-velocity modes in the variation of the ejection velocity of the jet. In addition, we investigated the effect of including the precession of the jet to the one- and two-velocity mode models. From the simulations, we constructed position-velocity diagrams and compared them with the observations. We find that including a second mode in the ejection velocity, as well as the precession, are required to explain the positions of the outflow knots and other position-velocity features observed in the outflow of core #8 in W43-MM1.

It is shown that the acceleration of particles by a powerful relativistic jet associated with the activity of a supermassive black hole in the Galactic center several million years ago may explain the observed cosmic ray spectrum at energies higher than $10^{15}$ eV. The accelerated particles are efficiently confined in the extended magnetized gas halo created by the supernova and central black hole activity just after the Galaxy formation. We found that both the heavy and light chemical composition of ultra-high energy cosmic rays can be consistent with observations.

Context. The identification of bright QSOs is of great importance to probe the intergalactic medium and address open questions in cosmology. Several approaches have been adopted to find such sources in currently available photometric surveys, including machine learning methods. However, the rarity of bright QSOs at high redshifts compared to contaminating sources (such as stars and galaxies) makes the selection of reliable candidates a difficult task, especially when high completeness is required. Aims. We present a novel technique to boost recall (i.e., completeness within the considered sample) in the selection of QSOs from photometric datasets dominated by stars, galaxies, and low-z QSOs (imbalanced datasets). Methods. Our method operates by iteratively removing sources whose probability of belonging to a noninteresting class exceeds a user-defined threshold, until the remaining dataset contains mainly high-z QSOs. Any existing machine learning method can be used as underlying classifier, provided it allows for a classification probability to be estimated. We applied the method to a dataset obtained by cross-matching PanSTARRS1, Gaia, and WISE, and identified the high-z QSO candidates using both our method and its direct multi-label counterpart. Results. We ran several tests by randomly choosing the training and test datasets, and achieved significant improvements in recall which increased from 50% to 85% for QSOs with z>2.5, and from 70% to 90% for QSOs with z>3. Also, we identified a sample of 3098 new QSO candidates on a sample of 2.6x10^6 sources with no known classification. We obtained follow-up spectroscopy for 121 candidates, confirming 107 new QSOs with z>2.5. Finally, a comparison of our candidates with those selected by an independent method shows that the two samples overlap by more than 90% and that both methods are capable of achieving a high level of completeness.

When a star undergoes core collapse, a vast amount of energy is released in a ~10 s long burst of neutrinos of all species. Inverse beta decay in the star's hydrogen envelope causes an electromagnetic cascade which ultimately results in a flare of gamma rays - an "echo" of the neutrino burst - at the characteristic energy of 0.511 MeV. We study the phenomenology and detectability of this flare. Its luminosity curve is characterized by a fast, seconds-long, rise and an equally fast decline, with a minute- or hour-long plateau in between. For a near-Earth star (distance D<1 kpc) the echo will be observable at near future gamma ray telescopes with an effective area of 10^3 cm^2 or larger. Its observation will inform us on the envelope size and composition. In conjunction with the direct detection of the neutrino burst, it will also give information on the neutrino emission away from the line of sight and will enable tests of neutrino propagation effects between the stellar surface and Earth.

Turbulence is a key process in many astrophysical systems. In this work we explore the statistics of thermal and kinetic energy of isothermal, supersonic, turbulent gas. We develop analytic formulas for the PDF of thermal and kinetic energies and their joint PDF. We compare these analytical models with a suite of simulations with a fixed resolution of $1024^3$ cells across 4 different Mach numbers (1, 2, 4, 8) and three different driving patterns (compressive, mixed, solenoidal). We discover an interesting jump discontinuity in the thermal energy PDF, which carries onto the joint PDF.

The Euclid mission is poised to make unprecedented measurements in cosmology from the distribution of galaxies with strong Halpha spectral emission lines. Accurately interpreting this data requires understanding the imprints imposed by the physics of galaxy formation and evolution on galaxy clustering. In this work we utilize a semi-analytical model of galaxy formation (SAGE) to explore the necessary components for accurately reproducing the clustering of Euclid-like samples of Halpha emitters. We focus on developing a Halo Occupation Distribution (HOD) prescription able to reproduce the clustering of SAGE galaxies. Typically, HOD models assume that satellite and central galaxies of a given type are independent events. We investigate the need for conformity, i.e. whether the average satellite occupation depends on the existence of a central galaxy of a given type. Incorporating conformity into HOD models is crucial for reproducing the clustering in the reference galaxy sample. Another aspect we investigate is the radial distribution of satellite galaxies within haloes. The traditional density profile models, NFW and Einasto profiles, fail to accurately replicate the small-scale clustering measured for SAGE satellite galaxies. To overcome this limitation, we propose a generalization of the NFW profile, thereby enhancing our understanding of galaxy clustering.

The MeerKAT International GigaHertz Tiered Extragalactic Exploration (MIGHTEE) is one of the MeerKAT large survey projects, designed to pathfind SKA key science. MIGHTEE is undertaking deep radio imaging of four well observed fields (COSMOS, XMM-LSS, ELAIS S1 and CDFS) totaling 20 square degrees to $\mu$Jy sensitivities. Broadband imaging observations between 880--1690 MHz yield total intensity continuum, spectro-polarimetry, and atomic hydrogen spectral imaging. Early science data from MIGHTEE are being released from initial observations of COSMOS and XMM-LSS. This paper describes the spectro-polarimetric observations, the polarization data processing of the MIGHTEE early science fields, and presents polarization data images and catalogues. The catalogues include radio spectral index, redshift information and Faraday rotation measure synthesis results for 13,271 total intensity radio sources down to a polarized intensity detection limit of $\sim$20 $\mu$Jy\,bm$^{-1}$. Polarized signals were detected from 324 sources. For the polarized detections we include a catalogue of Faraday Depth from both Faraday Synthesis and $Q$, $U$ fitting, as well as total intensity and polarization spectral indices. The distribution of redshift of the total radio sources and detected polarized sources are the same, with median redshifts of 0.86 and 0.82 respectively. Depolarization of the emission at longer-wavelengths is seen to increase with decreasing total-intensity spectral index, implying that depolarisation is intrinsic to the radio sources. No evidence is seen for a redshift dependence of the variance of Faraday Depth.

We derive constraints on the injection of free-streaming dark radiation after big bang nucleosynthesis (BBN) by considering the decay of a massive hidden sector particle into dark radiation. Such a scenario has the potential to alleviate the Hubble tension by introducing a new energy component to the evolution of the early universe. We employ observations of the cosmic microwave background (CMB) from $\textit{Planck}$ 2018 and SPT-3G, measurements of the primordial deuterium abundance, Pantheon+ Type Ia supernovae data, and baryon acoustic oscillation (BAO) measurements from BOSS DR12 to constrain these decay scenarios. Pre-recombination decays are primarily restricted by observations of the CMB via their impact on the effective number of relativistic species. On the other hand, long-lived decay scenarios in which the massive particle lifetime extends past recombination tend to decrease the late-time matter density inferred from the CMB and are thus subject to constraints from Pantheon+ and BAO. We find that, when marginalizing over lifetimes of $\tau_Y = [10^{-12.08}, 10^{-1.49}]$ Gyr, the decaying particle is limited at $2\sigma$ to only contribute a maximum of $3\%$ of the energy density of the universe. With limits on these decays being so stringent, neither short-lived nor long-lived scenarios are successful at substantially mitigating the Hubble tension.

This is a review of the current status of studies of cosmological inflation, extracted from Chapter 23 of the 2023 edition of the `Review of Particle Physics': R.L. Workman et al. (Particle Data Group), Prog. Theor. Exp. Phys., 2022, 083C01 (2022) and 2023 update.

Stars can be ripped apart by tidal forces in the vicinity of a massive black hole, causing luminous flares classified as tidal disruption events (TDEs). These events could be contributing to the mass growth of intermediate-mass black holes, while new samples from ongoing transient surveys can provide useful information on this otherwise undetectable growth channel. This work aims to study the demographics of TDEs by modeling the co-evolution of black holes and their galactic environments in a cosmological framework. We use the semi-analytic galaxy formation model L-Galaxies, which follows the evolution of galaxies as well as of massive black holes, including multiple scenarios for black hole seeds and growth, spin evolution, and binary black hole dynamics. Time-dependent TDE rates are associated with each black hole depending on the galaxy environment, following the solutions to the 1-D Fokker Planck equation solved with PhaseFlow. Our model produces TDE volumetric rates that are in agreement with the latest optical sample of 33 TDEs and previous X-ray samples. This agreement requires a high occupation fraction of nuclear star clusters with black holes since these star reservoirs host the majority of TDEs at all mass regimes. Unlike previous studies, we predict that TDE rates are an increasing function of black hole mass up to a peak of ${\sim}\, 10^{6.5}$M$_{\odot}$, beyond which rates drop following a shallow power-law distribution. We also discuss implications for the black hole spin distribution at the event horizon suppression and the cumulative growth due to TDEs. Our results highlight the need for time-dependent TDE rates, especially towards the low-mass regimes of the intermediate-mass black holes and dwarf galaxies.

Matter at ultra-high densities finds a physical realization inside neutron stars. One key property is their maximum mass, which has far-reaching implications for astrophysics and the equation of state of ultra dense matter. In this work, we employ Bayesian analysis to scrutinize the mass distribution and maximum mass threshold of galactic neutron stars. We compare two distinct models to assess the impact of assuming a uniform distribution for the most important quantity, the cosine of orbital inclination angles ($i$), which has been a common practice in previous analyses. This prevailing assumption yields a maximum mass of $2.25$~$M_\odot$ (2.15--3.32~$M_\odot$ within $90\%$ confidence), with a strong peak around the maximum value. However, in the second model, which indirectly includes observational constraints of $i$, the analysis supports a mass limit of $2.56^{+0.87}_{-0.58}~M_\odot$ ($2\sigma$ uncertainty), a result that points in the same direction as some recent results gathered from gravitational wave observations, although their statistics are still limited. This work stresses the importance of an accurate treatment of orbital inclination angles, and contributes to the ongoing debate about the maximum neutron star mass, further emphasizing the critical role of uncertainties in the individual neutron star mass determinations.

Primordial Black Holes (PBHs) could explain some fraction of dark matter and shed light on many areas of early-universe physics. Despite over half a century of research interest, a PBH population has so far eluded detection. The most competitive constraints on the fraction of dark matter comprised of PBHs ($f_{\rm DM}$) in the $(10^{-9}-10)M_{\odot}$ mass-ranges come from photometric microlensing and bound $f_{\rm DM}\lesssim10^{-2}-10^{-1}$. With the advent of the Roman Space Telescope with its sub-milliarcsecond (mas) astrometric capabilities and its planned Galactic Bulge Time Domain Survey (GBTDS), detecting astrometric microlensing signatures will become routine. Compared with photometric microlensing, astrometric microlensing signals are sensitive to different lens masses-distance configurations and contains different information, making it a complimentary lensing probe. At sub-mas astrometric precision, astrometric microlensing signals are typically detectable at larger lens-source separations than photometric signals, suggesting a microlensing detection channel of pure astrometric events. We use a Galactic simulation to predict the number of detectable microlensing events during the GBTDS via this pure astrometric microlensing channel. We find that the number of detectable events peaks at $\approx 10^{3} f_{\rm DM}$ for a population of $ 1 M_{\odot}$ PBHs and tapers to $\approx 10f_{\rm DM}$ and $\approx 100f_{\rm DM}$ at $10^{-4}M_{\odot}$ and $10^{3}M_{\odot}$, respectively. Accounting for the distinguishability of PBHs from Stellar lenses, we conclude the GBTDS will be sensitive and PBH population at $f_{\rm DM}$ down to $\approx10^{-1}-10^{-3}$ for $(10^{-1}-10^{2})M_{\odot}$ likely yielding novel PBH constraints.

The Telescope Array Collaboration recently reported the detection of a cosmic-ray particle, ``Amaterasu", with an extremely high energy of $2.4\times10^{20}$ eV. Here we investigate its probable charge and the locus of its production. Interpreted as a primary iron nucleus or slightly stripped fragment, the event fits well within the existing paradigm for UHECR composition and spectrum. Using the most up-to-date modeling of the Galactic magnetic field strength and structure, and taking into account uncertainties, we identify the likely volume from which it originated. We estimate a localization uncertainty on the source direction of 6.6\% of $4\pi$ or 2726 deg$^2$. The uncertainty of magnetic deflections and the experimental energy uncertainties contribute about equally to the localization uncertainty. The maximum source distance is 8-50 Mpc, with the range reflecting the uncertainty on the energy assignment. We provide sky maps showing the localization region of the event and superimpose the location of galaxies of different types. There are no candidate sources among powerful radio galaxies. An origin in AGNs or star-forming galaxies is unlikely but cannot be completely ruled out without a more precise energy determination. The most straightforward option is that Amaterasu was created in a transient event in an otherwise undistinguished galaxy.

SN 2021adxl is a slowly evolving, luminous, Type IIn supernova with asymmetric emission line profiles, similar to the well-studied SN 2010jl. We present extensive optical, near-ultraviolet, and near-infrared photometry and spectroscopy covering ~1.5 years post discovery. SN 2021adxl occurred in an unusual environment, atop a vigorously star-forming region that is offset from its host galaxy core. The appearance of Ly{\alpha}, O II, as well as the compact core, would classify the host of SN 2021adxl as a Blueberry galaxy, analogous to the higher redshift Green Pea galaxies. Using several abundance indicators, we find a metallicity of the explosion environment of only 10% solar, the lowest reported metallicity for a Type IIn SN environment. SN 2021adxl reaches a peak magnitude of r ~ -20.2 mag and since discovery, SN 2021adxl has faded by only ~4 magnitudes in the r band with a cumulative radiated energy of ~1.5e50 erg over 18 months. SN 2021adxl shows strong signs of interaction with a complex circumstellar medium, seen by the detection of X-rays, revealed by the detection of coronal emission lines, and through multi-component hydrogen and helium profiles. In order to further understand this interaction, we model the H{\alpha} profile using a Monte-Carlo electron scattering code. The blueshifted high-velocity component is consistent with emission from a radially thin, spherical shell resulting in the broad emission components due to electron scattering. Using the velocity evolution of this emitting shell, we find that the SN ejecta collide with circumstellar material of at least 5 Msun, assuming a steady-state mass-loss rate of 4-6e-3 Msun per year for the first ~200 days of evolution. Continuing the observations of SN 2021adxl may reveal signatures of dust formation or an infrared excess, similar to that seen for SN 2010jl.

Dynamical encounters of stellar-mass black holes (BHs) in a disc of compact objects around a supermassive BH (SMBH) can accelerate the formation and coalescence of BH binaries. It has been proposed that binary-single encounters among BHs in such discs can lead to an excess of highly-eccentric BH mergers. However, previous studies have neglected how the disc velocity dispersion and the SMBH's tidal field affect the 3-body dynamics. We investigate the outcomes of binary-single encounters considering different values of the disc velocity dispersion, and examine the role of the SMBH's tidal field. We then demonstrate how their inclusion affects the properties of merging BH binaries. We perform simulations of 4-body encounters (i.e. with the SMBH as fourth particle) using the highly-accurate, regularized code TSUNAMI, which includes post-Newtonian corrections up to order 3.5PN. The disc velocity dispersion controls how orbits in the disc are aligned and circular, and determines the relative velocity of the binary-single pair before the encounter. As the velocity dispersion decreases, the eccentricity of post-encounter binaries transitions from thermal to superthermal, and binaries experience enhanced hardening. The transition between these two regimes happens at disc eccentricities and inclinations of order e ~ i ~ 10^-4. These distinct regimes correspond to a disc dominated by random motions, and one dominated by the Keplerian shear. The inclusion of the SMBH's tidal field and the disc velocity dispersion can significantly affect the number of GW mergers, and especially the number of highly-eccentric inspirals. These can be up to ~2 times higher at low velocity dispersion, and ~12 times lower at high velocity dispersions. The spin-orbit alignment is influenced by the tidal field exclusively at high velocity dispersions, effectively inhibiting the formation of anti-aligned binary BHs.

Over the past decade, advancement of observational capabilities, specifically the Atacama Large Millimeter/submillimeter Array (ALMA) and SPHERE instrument, alongside theoretical innovations like pebble accretion, have reshaped our understanding of planet formation and the physics of protoplanetary disks. Despite this progress, mysteries persist along the winded path of micrometer-sized dust, from the interstellar medium, through transport and growth in the protoplanetary disk, to becoming gravitationally bound bodies. This review outlines our current knowledge of dust evolution in circumstellar disks, yielding the following insights: $\bullet$ Theoretical and laboratory studies have accurately predicted the growth of dust particles to sizes that are susceptible to accumulation through transport processes like radial drift and settling. $\bullet$ Critical uncertainties in that process remain the level of turbulence, the threshold collision velocities at which dust growth stalls, and the evolution of dust porosity. $\bullet$ Symmetric and asymmetric substructure are widespread. Dust traps appear to be solving several long-standing issues in planet formation models, and they are observationally consistent with being sites of active planetesimal formation. $\bullet$ In some instances, planets have been identified as the causes behind substructures. This underlines the need to study earlier stages of disks to understand how planets can form so rapidly. In the future, better probes of the physical conditions in optically thick regions, including densities, turbulence strength, kinematics, and particle properties will be essential for unraveling the physical processes at play.

We perform a phenomenological comparison of the gravitational wave (GW) spectrum expected from cosmic gauge string networks and superstring networks comprised of multiple string types. We show how violations of scaling behavior and the evolution of the number of relativistic degrees of freedom in the early Universe affect the GW spectrum. We derive simple analytical expressions for the GW spectrum from superstrings and gauge strings that are valid for all frequencies relevant to pulsar timing arrays (PTAs) and laser interferometers. We analyze the latest data from PTAs and show that superstring networks are consistent with 32~nHz data from NANOGrav, but are in tension with 3.2~nHz data unless the strings evolve in only about 10\% of the volume of the higher-dimensional space. We also point out that while gauge string networks are excluded by NANOGrav-15 data at $3\sigma$, they are completely compatible with EPTA and PPTA data. Finally, we study correlations between GW signals at PTAs and laser interferometers.

We employ the formalism developed in \cite{Mentasti:2023gmg} and \cite{Bartolo_2022} to study the prospect of detecting an anisotropic Stochastic Gravitational Wave Background (SGWB) with the Laser Interferometer Space Antenna (LISA) alone, and combined with the proposed space-based interferometer Taiji. Previous analyses have been performed in the frequency domain only. Here, we study the detectability of the individual coefficients of the expansion of the SGWB in spherical harmonics, by taking into account the specific motion of the satellites. This requires the use of time-dependent response functions, which we include in our analysis to obtain an optimal estimate of the anisotropic signal. We focus on two applications. Firstly, the reconstruction of the anisotropic galactic signal without assuming any prior knowledge of its spatial distribution. We find that both LISA and LISA with Taiji cannot put tight constraints on the harmonic coefficients for realistic models of the galactic SGWB. We then focus on the discrimination between a galactic signal of known morphology but unknown overall amplitude and an isotropic extragalactic SGWB component of astrophysical origin. In this case, we find that the two surveys can confirm, at a confidence level $\gtrsim 3\sigma$, the existence of both the galactic and extragalactic background if both have amplitudes as predicted in standard models. We also find that, in the LISA-only case, the analysis in the frequency domain (under the assumption of a time average of data taken homogeneously across the year) provides a nearly identical determination of the two amplitudes as compared to the optimal analysis.

We consider the effect of isospin-violating dark matter-nucleon interactions on direct detection constraints in the regime of small dark matter mass and large scattering cross section. Isospin-violation can lead to both reductions in sensitivity (due to a reduced cross section for scattering with nuclei in the detector) and enhancements in sensitivity (due to a reduced cross section for scattering in the overburden). Isospin-violating effects can thus open up some closed regions of parameter space, while closing off other regions.

Models with radiative symmetry breaking typically feature strongly supercooled first-order phase transitions, which result in an observable stochastic gravitational wave background. In this work, we analyse the role of higher order thermal corrections for these transitions, applying high-temperature dimensional reduction to a theory with dimensional transmutation. In particular, we study to what extent high-temperature effective field theories (3D EFT) can be used. We find that despite significant supercooling down from the critical temperature, the high-temperature expansion for the bubble nucleation rate can be applied using the 3D EFT framework, and we point out challenges in the EFT description. We compare our findings to previous studies, and find that the next-to-leading order corrections obtained in this work have a significant effect on the predictions for GW observables, motivating a further exploration of higher order thermal effects.

It has been known for quite sometime that the Neutron Stars (NS) can play a role of the Dark Matter (DM) detectors due to many uniques features of NS. We apply these (previously developed) ideas to a specific form of the DM when it is represented by a composite object, rather than by a local fundamental field (such as WIMPs). To be more precise we consider the so-called axion quark nuggets (AQN) dark matter model, when the ``non-baryonic" dark matter in fact is made of quarks and gluons which are in dense quark phase (similar to the old idea of the Witten's strangelets). We argue that the interaction of the AQNs with NS material may lead to many profound observable effects, which dramatically different from conventional picture when DM particles are represented by weakly interacting WIMPs. In particular, we argue that the AQNs may serve as the triggers for the magnetic reconnection to heat the NS surface. This effect may strongly alleviate (or even completely remove) the observed inconsistencies between the predicted and observed surface temperatures for many old NS. This heating mechanism is always accompanied by the hard X ray emission, which may serve as an indicator of the proposed mechanism.

We compare two versions of the GW150914 gravitational wave signal analysis by the LIGO/Virgo collaboration. The first version was published in 2016 by this collaboration along with their announcement of the first experimental detection of gravitational waves. It was based on the gravitational wave waveforms with the fully non-linear general-relativistic treatment of the coalescing two-body problem. The second analysis of this signal by the same authors, published in 2017, was based on the quadrupole post-Newtonian (PN) flat spacetime approximation of General Relativity. The authors had shown that the PN-based mass estimation of the system coincide with that obtained by using rigorous relativistic treatment in their first publication. In our view, this coincidence implies that the rigorous non-linear theory for gravitational waveforms of coalescing blackhole binaries does not fully account for the difference between the source and detector reference frames - because the PN-approximation, which is used for the comparison, does not make any distinction between these two reference frames: by design and by the principles and conditions for building the PN-approximation. We discuss possible implications of this conflict and find that the accuracy of most of the previously estimated characteristic (chirp) masses of coalescing binary blackhole systems is likely to be affected by a substantial systematic error. The corresponding luminosity distances of these sources also turn out to be overestimated.

The TREX-DM detector, a low background chamber with microbulk Micromegas readout, was commissioned in the underground laboratory of Canfranc (LSC) in 2018. Since then, data taking campaigns have been carried out with Argon and Neon mixtures, at different pressures from 1 to 4 bar. By achieving a low energy threshold of 1 keV$_{ee}$ and a background level of 80 counts keV$^{-1}$ Kg$^{-1}$ day$^{-1}$ in the region from 1 to 7 keV$_{ee}$, the experiment demonstrates its potential to search for low-mass WIMPs. Two of the most important challenges currently faced are the reduction of both, background level and energy threshold. With respect to the energy threshold, recently a new readout plane is being developed, based on the combination of Micromegas and GEM technologies, aiming to have a pre-amplification stage that would permit very low energy thresholds, close to the single-electron ionization energy. With respect to the background reduction, apart from studies to identify and minimize contamination population, a high sensitivity alpha detector is being developed in order to allow a proper material selection for the TREX-DM detector components. Both challenges, together with the optimization of the gas mixture used as target for the WIMP detection, will take TREX-DM to explore regions of WIMP's mass below 1 GeV c$^{-2}$.

Recently, the author and collaborators proposed a method to construct a new conserved charge different from the Noether one for general relativistic field theory on curved space-time with energy-momentum tensor covariantly conserved, and that the new conserved charge describes the entropy of the system. As concrete evidence of the proposals, it was shown that such a new conserved charge indeed exists for several classic gravitational systems, and that the proposed entropy density computed in them satisfies the local Euler's relation and the first law of thermodynamics concurrently and non-perturbatively with respect to the Newton constant. These developments are reviewed including brief discussions of physical implications of the local thermodynamic relations.

Directional detection is the dedicated strategy to demonstrate that DM-like signals measured by direct detectors are indeed produced by DM particles from the galactic halo. The experimental challenge of measuring the direction of DM-induced nuclear recoils with (sub-)millimeter tracks has limited, so far, the maximal directional reach to DM masses around $100~\rm{GeV}$. In this paper, we expose the MIMAC detector to three different neutron fields and we develop a method to reconstruct the direction of the neutron-induced nuclear recoils. We measure an angular resolution better than $16^\circ$ for proton recoils down to a kinetic energy of $4~\rm{keV}$ and for carbon recoils down to a kinetic energy of $5.5~\rm{keV}$. For the first time, a detector achieves the directional measurement of proton and carbon recoils with kinetic energies in the keV range without any restriction on the direction of the incoming particle. This work demonstrates that directional detection is around the corner for probing DM with masses down to $\mathcal{O}(1~\rm{GeV})$.

We report the first detection of optical emission from the shell-type Galactic supernova remnant (SNR) G108.2$-$0.6. We obtained H$\alpha$ images and long-slit spectra using the 1.5-m RTT150 telescope to examine the morphological and spectral characteristics of the SNR. We detected several filaments along its north and south regions, which is consistent with its SNR nature. The spectra exhibit [SII]/H$\alpha$ ratios in the range of 0.4$-$1.1, indicating emission from shock-heated gas. The oxygen doublet emission lines [OI]$\lambda$6300, $\lambda$6363 detected in the south region also support the indicator of the presence of shocks. We estimate the electron density using the [SII] 6716/6731 ratio ranging from 15 to 1800 cm$^{-3}$. The spectra show a relatively low shock velocity of $V_{\rm s}$ $\sim$ 80 km s$^{-1}$ with the pre-shock cloud density of $n_{\rm c}$ $\sim$18$-$57 cm$^{-3}$. The H$\alpha$/H$\beta$ ratios show significant variation across the observed regions with extinction $E(B-V)$ ranging from 0.22 to 1.65. We also analyzed the archival HI data and estimated the kinematic distance to the SNR of $\sim$0.8 kpc and dynamical age as $\sim$70$\pm$10 kyr of G108.2$-$0.6.

The initial density of dark matter (DM) particles, otherwise secluded from the standard model (SM), may be generated at reheating, with an initial temperature ratio for internal thermalizations, $\xi_i=T_{\rm DM,i}/T_{\rm SM,i}$. This scenario necessarily implies inflaton-mediated scatterings between DM and SM after reheating, with a rate fixed by the relic abundance of DM and the reheat temperature. These scatterings can be important for an inflaton mass and reheat temperature as high as $\mathcal{O}(10^7 {~\rm GeV})$ and $\mathcal{O}(10^9{~\rm GeV})$, respectively, since the thermally averaged collision terms become approximately independent of the inflaton mass when the bath temperature is larger than the mass. The impact of these scatterings on DM cosmology is studied modeling the perturbative reheating physics by a gauge-invariant set of inflaton interactions upto dimension-5 with the SM gauge bosons, fermions and the Higgs fields. It is observed that an initially lower (higher) DM temperature will rapidly increase (decrease), even with very small couplings to the inflaton. There is a sharp lower bound on the DM mass below which the relic abundance cannot be satisfied due to faster back-scatterings depleting DM quanta to SM particles. For low DM masses, the CMB constraints become stronger due to the collisions for $\xi_i<1$, probing values as small as $\mathcal{O}(10^{-4})$, and weaker for $\xi_i>1$. The BBN constraints become stronger due to the collisions for lower DM masses, probing $\xi_i$ as small as $\mathcal{O}(0.1)$, and weaker for higher DM mass. Thus inflaton-mediated collisions with predictable rates, relevant even for high-scale inflation models, can significantly impact the cosmology of light DM.

In gravitational-wave astronomy, extreme-mass-ratio-inspiral (EMRI) sources for the upcoming LISA observatory have the potential to serve as high-precision probes of astrophysical environments in galactic nuclei, and of potential deviations from general relativity (GR). Such ``beyond vacuum-GR'' effects are often modeled as perturbations to the evolution of vacuum EMRIs under GR. Previous studies have reported unprecedented constraints on these effects by examining the inference of one effect at a time. However, a more realistic analysis would require the simultaneous inference of multiple beyond vacuum-GR effects. The parameters describing such effects are generally significantly correlated with each other and the vacuum EMRI parameters. We explicitly show how these correlations remain even if any modeled effect is absent in the actual signal, and how they cause inference bias when any effect in the signal is absent in the analysis model. This worsens the overall measurability of the whole parameter set, challenging the constraints found by previous studies, and posing a general problem for the modeling and inference of beyond vacuum-GR effects in EMRIs.

Investigation of neutrino spin oscillation in the gravitational fields of black holes(BH) is one of the interesting topics in neutrino physics. On the other hand, in recent years, many studies have been devoted to the exploration of different physical phenomena in higher dimensions. Noncommutative geometry has also been in the focus of researchers in the past years to explore deeper and more accurate the structure of space time. In this work, the neutrino spin oscillation in the noncommutative higher dimensions gravitational fields of Schwarzschild and Reissner-Nordstrom metrics are studied. The effects of noncommutativity of space are calculated and its role in different dimensions are discussed. Finally upper bounds on noncommutativity parameter are obtained.

We show that a phase transition may take place in the early Universe at a temperature $T_*$ via a Standard Model singlet scalar field which happens to couple to right handed neutrinos (RHN) resulting a temperature dependent mass for them that finally relaxes to a constant value after electroweak phase transition (EWPT). As a result, a requisite amount of lepton asymmetry can be produced at a temperature close to $T_*$ satisfying the observed baryon asymmetry of the Universe via sphaleron process even when the zero temperature masses of the RHNs fall in sub GeV regime providing a testable scenario for leptogenesis. Interestingly, the framework is also capable of predicting a primordial lepton asymmetry (generated at a temperature below the EWPT), as hinted by helium abundance measuring experiments, bearing a correlation with early phase of leptogenesis.

We argue that the Starobinsky model of inflation, realised via an $R^2$ term in the Lagrangian, can originate from quantum effects due to a tower of light species. By means of two separate arguments, we show how this implies that the scale of the $R^2$ term must be of order of the species scale $\Lambda_s$, namely the energy at which gravity becomes strongly coupled. We discuss the implications and challenges of this scenario for inflation, inflationary reheating, and string theory embeddings. In this context, we collect strong evidence to conclude that Starobinsky inflation lies in the Swampland.