Papers for Tuesday, Nov 05 2024

Many massive binary systems undergo mass and angular momentum transfer over the course of their evolution. This kind of interaction is expected to deeply affect the properties of the mass donor and mass gainer and to leave various observational signatures. The most common smoking guns of a past mass transfer episode are notably rapid rotation of the mass gainer and altered surface chemical abundances of the stripped mass donor star. Quantitative observational studies of evolved massive binaries are crucial to gain insight into poorly constrained parameters of binary evolution models such as the fraction of mass lost by the mass donor that is actually accreted by the mass gainer. Yet, drawing conclusions about a past mass transfer episode requires a detailed analysis of all aspects of a binary system which sometimes leads to unexpected results. In this contribution, we review the existing observational evidence for past mass exchange events in massive main-sequence and post main-sequence binaries.

The quasar OJ~287 has shown large flares since 1888, following a pattern that arises in a supermassive black hole binary when the secondary hits the accretion disk of the primary, and releases a hot bubble of gas at every disk crossing. A complete mathematical solution of the flare sequence produced a list of future flares, the latest happening in the summer of 2022. Here I look into the origin of the idea that the lack of seeing the 2022 flare is a theoretical problem. During the summer OJ~287 cannot be observed by ground-based optical telescopes. In a paper published in 2021, ahead of the 2022 observing campaign, this was clearly stated. The often repeated claim that there is a "missing flare problem", is a misunderstanding, as no detection was possible with the current instrumentation.

Evaluation of the Voigt function, a convolution of a Lorentzian and a Gaussian profile, is essential in various fields such as spectroscopy, atmospheric science, and astrophysics. Efficient computation of the function is crucial, especially in applications where the function may be called for an enormous number of times. In this paper, we present a highly efficient novel algorithm and its Fortran90 implementation for the practical evaluation of the Voigt function with accuracy in the order of 1.0e-6. The algorithm uses improved fits based on Chebyshev subinterval polynomial approximation for functions in two variables. The algorithm significantly outperforms widely-used competitive algorithms in the literature, in terms of computational speed, making it highly suitable for real-time applications and large-scale data processing tasks. The substantial improvement in efficiency positions the present algorithm and computer code as a valuable tool in relevant scientific domains. The algorithm has been adopted and implemented in the Meudon PDR code at Paris Observatory and is recommended for similar applications and simulation packages.

$\texttt{bayes_spec}$ is a Bayesian spectral line modeling framework for astrophysics. Given a user-defined model and a spectral line dataset, $\texttt{bayes_spec}$ enables inference of the model parameters through different numerical techniques, such as Monte Carlo Markov Chain (MCMC) methods, implemented in the PyMC probabilistic programming library. The API for $\texttt{bayes_spec}$ is designed to support astrophysical researchers who wish to ``fit'' arbitrary, user-defined models, such as simple spectral line profile models or complicated physical models that include a full physical treatment of radiative transfer. These models are ``cloud-based'', meaning that the spectral line data are decomposed into a series of discrete clouds with parameters defined by the user's model. Importantly, $\texttt{bayes_spec}$ provides algorithms to determine the optimal number of clouds for a given model and dataset.

A formulation for the parametric instability of electromagnetic (EM) waves in magnetized pair plasma is developed. The linear growth rate of induced Compton scattering is derived analytically for frequencies below the cyclotron frequency for the first time. We identify three modes of density fluctuation: ordinary, charged, and neutral modes. In the charged mode, the ponderomotive force separates charges (electrons and positrons) longitudinally, in contrast to the nonmagnetized case. We also recognize two effects that significantly reduce the scattering rate for waves polarized perpendicular to the magnetic field: (1) the gyroradius effect due to the magnetic suppression of particle orbits, and (2) Debye screening for wavelengths larger than the Debye length. Applying this to fast radio bursts (FRBs), we find that these effects facilitate the escape of X-mode waves from the magnetosphere and outflow of a magnetar and neutron star, enabling 100\% polarization as observed. Our formulation provides a foundation for consistently addressing the nonlinear interaction of EM waves with magnetized plasma in astrophysics and laser physics.

Massive star-forming regions exhibit a rich chemistry with complex gas distributions, especially on small scales. While surveys have yielded constraints on typical gas conditions, they often have coarse spatial resolution and limited bandwidths. Thus, to establish an interpretative framework for these efforts, detailed observations that simultaneously provide high sensitivity, spatial resolution, and large bandwidths for a subset of diverse sources are needed. Here, we present wideband (32 GHz) Submillimeter Array observations of four high-mass star-forming regions (G28.20-0.05, G20.08-0.14 N, G35.58-0.03, W33 Main) at subarcsecond resolution, where we detect and spatially-resolve 100s of lines from over 60 molecules, including many complex organic molecules (COMs). The chemical richness of our sample is consistent with an evolutionary sequence from the line-rich hot cores and HC HII regions of G28.20-0.05 and G20.08-0.14 N to the more chemically-modest UC HII regions in G35.58-0.03, followed by the molecule-poor HII region W33 Main. We detect lines across a range of excitation conditions (Eu=20 to >800 K) and from numerous isotopologues, which enables robust estimates of gas properties. We derive nearly constant COM column density ratios that agree with literature values in other low- and high-mass protostellar cores, supporting the idea that COM abundances are set during the pre-stellar phase. In all regions, we identify spatial offsets among different molecular families, due to a combination of source physical structure and chemistry. In particular, we find potential evidence of carbon grain sublimation in G28.20-0.05 and identify an elemental oxygen gradient and rich sulfur-chemistry in G35.58-0.03. Overall, these results demonstrate that the SMA's wide bandwidth is a powerful tool to untangle the complex molecular gas structures associated with massive star formation.

Salt clouds are predicted to be common on warm exoplanets, but their optical properties are uncertain. The Exoplanet Cloud Ensemble Scattering System (ExCESS), a new apparatus to measure the scattering intensity and degree of linear polarization (DOLP) for an ensemble of particles, is introduced here and used to study the light scattering properties of KCl cloud analogs. ExCESS illuminates particles with a polarized laser beam (532 nm) and uses a photomultiplier tube detector to sweep the plane of illumination. Scattering measurements for KCl particles were collected for three size distributions representative of modeled clouds for the warm exoplanet GJ 1214b. Our measurements show that Lorenz-Mie calculations, commonly used to estimate the light scattering properties of assumedly spherical cloud particles, offer an inaccurate depiction of cubic and cuboid shaped KCl particles. All of our measurements indicate that Lorenz-Mie scattering overestimates the backscattering intensity of our cloud analogs and incorrectly predicts the scattering at mid-phase angles (~90 degrees) and preferential polarization state of KCl scattered light. Our results align with the general scattering properties of non-spherical particles and underscore the importance of further understanding the effects that such particles will have on radiative transfer models of exoplanet atmospheres and reflected light observations of exoplanets by the upcoming Nancy Grace Roman Space Telescope and Habitable Worlds Observatory.

A promising way to test the physics of the accelerated expansion of the Universe is by studying the growth rate of matter fluctuations, which can be parameterized by the matter energy density parameter to the power $\gamma$, the so-called growth index. It is well-known that the $\Lambda$CDM cosmology predicts $\gamma=0.55$. However, using observational data, Ref. \citep{Nguyen:2023fip} measured a much higher $\gamma=0.633^{+0.025}_{-0.024}$, excluding the $\Lambda$CDM value within $3.7\sigma$. In this work, we analyze whether Dark Energy (DE) with the Equation of State (EoS) parameter described by the CPL parametrization can significantly modify $\gamma$ with respect to the $\Lambda$CDM one. Besides the usual Smooth DE (SDE) scenario, where DE perturbations are neglected on small scales, we also consider the case of Clustering Dark Energy (CDE), which has more potential to impact the growth of matter perturbations. In order to minimally constrain the background evolution and assess the largest meaningful $\gamma$ distribution, we use data from $32$ Cosmic Chronometers, $H(z$), data points. In this context, we found that both SDE and CDE models described by the CPL parametrization can not provide a significant number of $\gamma$ samples compatible with the value determined in Nguyen et al. (2023). Therefore, explaining the measured value of $\gamma$ is a challenge for DE models. Moreover, we present new fitting functions for $\gamma$, which are more accurate and general than the one proposed in Linder (2005) for SDE, and, for the first time, fitting functions for CDE models.

Large scientific institutions, such as the Space Telescope Science Institute, track the usage of their facilities to understand the needs of the research community. Astrophysicists incorporate facility usage data into their scientific publications, embedding this information in plain-text. Traditional automatic search queries prove unreliable for accurate tracking due to the misidentification of facility names in plain-text. As automatic search queries fail, researchers are required to manually classify publications for facility usage, which consumes valuable research time. In this work, we introduce a machine learning classification framework for the automatic identification of facility usage of observation sections in astrophysics publications. Our framework identifies sentences containing telescope mission keywords (e.g., Kepler and TESS) in each publication. Subsequently, the identified sentences are transformed using Term Frequency-Inverse Document Frequency and classified with a Support Vector Machine. The classification framework leverages the context surrounding the identified telescope mission keywords to provide relevant information to the classifier. The framework successfully classifies usage of MAST hosted missions with a 92.9% accuracy. Furthermore, our framework demonstrates robustness when compared to other approaches, considering common metrics and computational complexity. The framework's interpretability makes it adaptable for use across observatories and other scientific facilities worldwide.

Classical Wolf-Rayet stars are descendants of massive OB-type stars that have lost their hydrogen-rich envelopes, and are in the final stages of stellar evolution, possibly exploding as type Ib/c supernovae. It is understood that the mechanisms driving this mass-loss are either strong stellar winds and or binary interactions, so intense studies of these binaries including their evolution can tell us about the importance of the two pathways in WR formation. WR 138 (HD 193077) has a period of just over 4 years and was previously reported to be resolved through interferometry. We report on new interferometric data combined with spectroscopic radial velocities in order to provide a three-dimensional orbit of the system. The precision on our parameters tend to be about an order of magnitude better than previous spectroscopic techniques. These measurements provide masses of the stars, namely $M_{\rm WR} = 13.93\pm1.49M_{\odot}$ and $M_{\rm O} = 26.28\pm1.71M_{\odot}$. The derived orbital parallax agrees with the parallax from \textit{Gaia}, namely with a distance of 2.13 kpc. We compare the system's orbit to models from BPASS, showing that the system likely may have been formed with little interaction but could have formed through some binary interactions either following or at the start of a red supergiant phase, but with the most likely scenario occurring as the red supergiant phase starts for a $\sim 40M_\odot$ star.

Understanding planetary habitability is one of the major challenges of the current scientific era, particularly given the discovery of a large and diverse terrestrial exoplanet population. Discerning the primary factors that contribute to planetary habitability may be extracted through a detailed examination of the terrestrial planets within the Solar System, most particularly Venus, Earth, and Mars, and the evolution of their interiors and atmospheres through time. Here, we provide a detailed description of the fundamental properties of these three planets, the effects of solar evolution, and the potential contributions of these various aspects toward driving their evolutionary pathways. We argue that evolution of Venus, Earth, and Mars provide essential templates from which a more comprehensive approach toward the study of planetary habitability may be derived.

Coronal Mass Ejections (CMEs) are subject to changes in their direction of propagation, tilt, and other properties as they interact with the variable solar wind. We investigated the heliospheric propagation of 15 Earth-impacting CMEs observed during April 2010 to August 2018 in the field of view (FOV) of the Heliospheric Imager (HI) onboard the STEREO. About half of the 15 events followed self-similar expansion up to 40 $R_\odot$. The remaining events showed deflection either in latitude, longitude, or a tilt change. Only two events showed significant rotation in the HI1 FOV. We also use toroidal and cylindrical flux rope fitting on the in situ observations of interplanetary magnetic field (IMF) and solar wind parameters to estimate the tilt at L1 for these two events. Although the sample size is small, this study suggests that CME rotation is not very common in the heliosphere. We attributed the observed deflections and rotations of CMEs to a combination of factors, including their interaction with the ambient solar wind and the influence of the ambient magnetic field. These findings contribute to our understanding of the complex dynamics involved in CME propagation and highlight the need for comprehensive modeling and observational studies to improve space weather prediction. In particular, HI observations help us to connect observations near the Sun and near Earth, improving our understanding of how CMEs move through the heliosphere.

Pulsating stars are universally recognized as precise distance indicators and tracers of stellar populations. Their variability, combined with well-defined relationships between pulsation properties and intrinsic evolutionary parameters such as luminosity, mass, and age, makes them essential for understanding galactic evolution and retrieving star formation histories. Therefore, accurate modeling of pulsating stars is crucial for using them as standard candles and stellar population tracers. This is the first paper in the "Stellar Pulsation and Evolution: a Combined Theoretical Renewal and Updated Models" (SPECTRUM) project, which aims to present an update of Stellingwerf's hydrodynamical pulsation code, by adopting the latest radiative opacity tables commonly used in stellar evolution community. We assess the impact of this update on pulsation properties, such as periods, instability strip topology, and light curve shapes, as well as on Period Wesenheit and Period-Luminosity relations for Classical Cepheids and RR Lyrae stars, comparing the results with those derived using older opacity data. Our results indicate that the opacity update introduces only minor changes: instability strip boundary locations shift by no more than $100K$ in effective temperature, and pulsation periods vary within $1\sigma$ compared to previous evaluations. Light curves exhibit slight differences in shape and amplitude. Consequently, the theoretical calibration of the Cepheid or RRL-based extragalactic distance scale remains largely unaffected by the opacity changes. However, achieving consistency in opacity tables between stellar evolution and pulsation codes is a significant step toward a homogeneous and self-consistent stellar evolution and pulsation framework.

Context. The influence of magnetic fields on stellar evolution remains unresolved. It has been proposed that if there is a large-scale magnetic field in the stellar interior, torsional waves could arise, efficiently transporting angular momentum. In fact, the observed variations in the rotation periods of some magnetic stars may be attributed to these torsional waves' standing waves. Aims. To demonstrate the existence of torsional waves through modeling of the rotational period variations. Method. We conduct an eigenmode analysis of standing waves based on one-dimensional magnetohydrodynamic equations. The internal magnetic field structures are parametrically represented to treat poloidal fields with different degrees of central/surface concentration. The obtained frequencies are compared with the observed frequencies of the rotational period variations, thereby constraining the internal magnetic field structures. Results. The 67.6 years exhibited by CU Vir is reproduced for surface-concentrated magnetic field structures. The rotational period variations of all ten magnetic stars analyzed in this study are inconsistent with a centrally concentrated magnetic field. Conclusions. Torsional waves can reproduce the observations of rotational period variations. The large-scale magnetic fields within magnetic stars would be concentrated on the surface.

The Water Cherenkov Detector Array (WCDA) is one of the components of Large High Altitude Air Shower Observatory (LHAASO) and can monitor any sources over two-thirds of the sky for up to 7 hours per day with >98\% duty cycle. In this work, we report the detection of two outbursts of the Fanaroff-Riley I radio galaxy NGC 1275 that were detected by LHAASO-WCDA between November 2022 and January 2023 with statistical significance of 5.2~$\sigma$ and 8.3~$\sigma$. The observed spectral energy distribution in the range from 500 GeV to 3 TeV is fitted by a power-law with a best-fit spectral index of $\alpha=-3.37\pm0.52$ and $-3.35\pm0.29$, respectively. The outburst flux above 0.5~TeV was ($4.55\pm 4.21)\times~10^{-11}~\rm cm^{-2}~s^{-1}$ and ($3.45\pm 1.78)\times~10^{-11}~\rm cm^{-2}~s^{-1}$, corresponding to 60\%, 45\% of Crab Nebula flux. Variation analysis reveals the variability time-scale of days at the TeV energy band. A simple test by one-zone synchrotron self-Compton model reproduces the data in the gamma-ray band well.

Far-infrared (FIR) surveys are critical to probing the co-evolution of black holes and galaxies, since of order half the light from accreting black holes and active star formation is emitted in the rest-frame infrared over $0.5\lesssim z \lesssim 10$. For deep fields with areas of 1 deg$^2$ or less, like the legacy surveys GOODS, COSMOS, and CANDELS, source crowding means that sub-arcsecond resolution is essential. In this paper we show with a simulation of the FIR sky that measurements made with a small telescope (2 m) at low angular resolution yield biased results, and we demonstrate the scientific value of a space mission that would offer sub-arcsecond resolution. We envisage a facility that would provide high-resolution imaging and spectroscopy over the wavelength range $25-400\,\mu$m, and we present predictions for an extragalactic survey covering $0.5\,\hbox{deg}^2$. Such a survey is expected to detect tens of thousands of star-forming galaxies and thousands of Active Galactic Nuclei (AGN), in multiple FIR lines (e.g. [CII], [OI], [CI]) and continuum. At the longest wavelengths (200-400$\,\mu$m), it would probe beyond the reionization epoch, up to $z\sim 7$-8. A combination of spectral resolution, line sensitivity, and broad spectral coverage would allow us to learn about the physical conditions (temperature, density, metallicity) characterizing the interstellar medium of galaxies over the past $\sim 12$ billion years and to investigate galaxy-AGN co-evolution.

Observations of the Cosmic Microwave Background (CMB) radiation have made significant contributions to our understanding of cosmology. While temperature observations of the CMB have greatly advanced our knowledge, the next frontier lies in detecting the elusive B-modes and obtaining precise reconstructions of the CMB's polarized signal in general. In anticipation of proposed and upcoming CMB polarization missions, this study introduces a novel method for accurately determining the angular power spectrum of CMB B-modes. We have developed a Neural Network-based approach to enhance the performance of the Internal Linear Combination (ILC) technique. Our method is applied to the frequency channels of the proposed ECHO (Exploring Cosmic History and Origins) mission and its performance is rigorously assessed. Our findings demonstrate the method's efficiency in achieving precise reconstructions of CMB B-mode angular power spectra, with errors constrained primarily by cosmic variance.

A space-dependent mean for cosmological perturbations negates the ansatz of statistical homogeneity and isotropy, and hence ergodicity. In this work, we construct such a primordial mean of scalar perturbations from an alternative quantum initial state (coherent state) and examine the associated power and bi-spectra. A multitude of cosmological tests based on these spectra are discussed. We find that current cosmological data doesn't favor a primordial mean over large scales and strong constraints arise from the limit on bispectrum from Planck data. At small scales, this hypothesis can be tested by future observables such as $\mu$-distortion of CMB.

This article describes condensation of the elements and use of condensation temperatures (Tcond) to interpret the volatility trend of the Earth. Major points are: (1) a listing of updated 50% Tcond for all natural elements and Pu at 1e-2 to 1e-8 bar pressure for solar composition matter. (2) The Tcond are mainly controlled by the Gibbs energy of condensation reactions and also by the Gibbs energy of ideal mixing if elements (compounds) condense in a solution. The Gibbs energy change of non-ideal solution (activity coefficients not equal to 1) is a secondary effect. (3) The theoretically correct relationship between Tcond and fraction condensed is derived from mass balance and chemical thermodynamic considerations. (4) The maximum amount of element condensed per 1/T, is at the inflection point in the logistic (sigmoid) curve for an element, which is also at (or close to) the 50% Tcond. (5) Plots of normalized elemental abundances versus 50% Tcond (volatility trends) are qualitative indicators of elemental fractionations due to volatility. (6) Volatility trend plots for average elemental abundances in CM, CO, CV, CR, H, L, LL, EH, EL chondrites show different trends for moderately and highly volatile elements, which may be linear, curved, a step function, or plateau. Comparison of three abundance sets for CM and CV chondrites shows trends depend on which elements are plotted, which data sources are used, and which temperature range is considered. (7) Proposed mechanisms for volatile element depletion in carbonaceous chondrites and the Earth are reviewed. (8) Possible implications of volatile element abundances in the bulk silicate Earth are discussed.

In this work, we present a framework for estimating and evaluating uncertainty in deep-attention-based classifiers for light curves for variable stars. We implemented three techniques, Deep Ensembles (DEs), Monte Carlo Dropout (MCD) and Hierarchical Stochastic Attention (HSA) and evaluated models trained on three astronomical surveys. Our results demonstrate that MCD and HSA offers a competitive and computationally less expensive alternative to DE, allowing the training of transformers with the ability to estimate uncertainties for large-scale light curve datasets. We conclude that the quality of the uncertainty estimation is evaluated using the ROC AUC metric.

We report the results of a spectroscopic survey of candidate T subdwarfs identified by the Backyard Worlds: Planet 9 program. Near-infrared spectra of 31 sources with red $J-W2$ colors and large $J$-band reduced proper motions show varying signatures of subsolar metallicity, including strong collision-induced H$_2$ absorption, obscured methane and water features, and weak K I absorption. These metallicity signatures are supported by spectral model fits and 3D velocities, indicating thick disk and halo population membership for several sources. We identify three new metal-poor T subdwarfs ([M/H] $\lesssim$ $-$0.5), CWISE J062316.19+071505.6, WISEA J152443.14$-$262001.8, and CWISE J211250.11-052925.2; and 19 new "mild" subdwarfs with modest metal deficiency ([M/H] $\lesssim$ $-$0.25). We also identify three metal-rich brown dwarfs with thick disk kinematics. We provide kinematic evidence that the extreme L subdwarf 2MASS J053253.46+824646.5 and the mild T subdwarf CWISE J113010.07+313944.7 may be part of the Thamnos population, while the T subdwarf CWISE J155349.96+693355.2 may be part of the Helmi stream. We define a metallicity classification system for T dwarfs that adds mild subdwarfs (d/sdT), subdwarfs (sdT), and extreme subdwarfs (esdT) to the existing dwarf sequence. We also define a metallicity spectral index that correlates with metallicities inferred from spectral model fits and iron abundances from stellar primaries of benchmark T dwarf companions. This expansion of the T dwarf classification system supports investigations of ancient, metal-poor brown dwarfs now being uncovered in deep imaging and spectroscopic surveys.

Key nuclear inputs for the astrophysical r process simulations are the weak interaction rates. Consequently, the accuracy of these inputs directly affects the reliability of nucleosynthesis modeling. Majority of the stellar rates, used in simulation studies, are calculated invoking the Brink Axel (BA) hypothesis. The BA hypothesis assumes that the strength functions of all parent excited states are the same as for the ground state, only shifted in energies. However, BA hypothesis has to be tested against microscopically calculated state by state rates. In this project we study the impact of the BA hypothesis on calculated stellar \b{eta} decay and electron capture rates. Our investigation include both Unique First Forbidden (U1F) and allowed transitions for 106 neutron rich trans iron nuclei ([27, 77] less than equal to [Z, A] less than equal to [82, 208]). The calculations were performed using the deformed proton-neutron quasiparticle randomphase approximation (pn QRPA) model with a simple plus quadrupole separable and schematic interaction. Waiting-point and several key r process nuclei lie within the considered mass region of the nuclear chart.

The CNO cycle is the main source of energy in stars more massive than our Sun. It defines the energy production and the duration contributes in determining the lifetime of massive stars. The cycle is an important tool for the determination of the age of globular clusters. Radiative capture p plus 14N 15O plus {\gamma}, at energies of astrophysical interest, is one of the important processes in the CNO cycle. In this project, we apply a potential model to describe both non resonant and resonant reactions in the channels where radiative capture occurs through electric E1 transitions. We employed the R matrix method to describe the reactions going via M1 resonant transitions, when it was not possible to correctly reproduce the experimental data by a potential model. The partial components of the astrophysical S factor are calculated for all possible electric and magnetic dipole transitions in 15O. The linear extrapolated S factor at zero energy (S(0)) is in good agreement with earlier reported values for all types of transitions considered in this work. Based on the value of the total astrophysical S factor, depending on the collision energy, we calculate the nuclear reaction rates for p plus 14N 15O plus {\gamma}. The computed rates are in good agreement with the results of the NACRE II Collaboration and the most recent existing measurements.

We report our counterpart identification study for two high-energy, Gold neutrino events IC-130127A and IC-131204A listed in the IceCube Event Catalog of Alert Tracks. Within the events' 90\% positional uncertainty regions, we respectively find PKS~2332$-$017 and PMN J1916$-$1519. The first source is a flat-spectrum radio quasar at redshift $z= 1.18$ and the second a blazar of an uncertain type with photometric $z= 0.968$. As they correspondingly had a $\gamma$-ray flare temporally coincident with the arrival times of IC-130127A and IC-131204A, we identify them as the respective neutrino emitters. Detailed analysis of the $\gamma$-ray data for the two blazars, obtained with the Large Area Telescope (LAT) onboard {\it the Fermi Gamma-ray Space Telescope (Fermi)}, is conducted. The two flares respectively from PKS~2332$-$017 and PMN~J1916$-$1519 lasted $\sim$4\,yr and $\sim$4\,month, and showed possible emission hardening by containing high-energy $\sim$2--10\,GeV photons in the emissions. Accompanying the flare of PKS~2332$-$017, optical and MIR brightening variations were also observed. We discuss the properties of the two sources and compare the properties with those of the previously reported (candidate) neutrino-emitting blazars.

Long-duration gamma-ray bursts (GRBs) are thought to be from core collapse of massive stars, and a rapidly spinning magnetar or black hole may be formed as the central engine. The extended emission in the prompt emission, flares and plateaus in X-ray afterglow, are proposed to be as the signature of central engine re-activity. However, the directly evidence from observations of identifying the central engines remain an open question. In this paper, we systemically search for long-duration GRBs that consist of bumps in X-ray afterglow detected by Swift/XRT, and find that the peak time of the X-ray bumps exhibit bimodal distribution (defined as early and late bumps) with division line at $t=7190$ s. Although we cannot rule out that such a bimodality arises from selection effects. We proposed that the long-duration GRBs with an early (or late) bumps may be originated from the fall-back accretion onto a new-born magnetar (or black hole). By adopting MCMC method to fit the early (or late) bumps of X-ray afterglow with the fall-back accretion of magnetar (or black hole), it is found that the initial surface magnetic filed and period of magnetars for most early bumps are clustered around $5.88\times10^{13}$ G and $1.04$ ms, respectively. Meanwhile, the derived accretion mass of black hole for late bumps is range of $[4\times10^{-4}, 1.8\times10^{-2}]~M_{\odot}$, and the typical fall-back radius is distributed range of $[1.04, 4.23]\times 10^{11}$ cm which is consistent with the typical radius of a Wolf-Rayet star. However, we also find that the fall-back accretion magnetar model is disfavored by the late bumps, but the fall-back accretion of black hole model can not be ruled out to interpret the early bumps of X-ray afterglow.

We present a study of the multiwavelength (MW) variability of the blazar AO 0235+164 based on the radio-to-$\gamma$-ray data covering a long time period from 1997 to 2023. The radio data are represented by the 1-22 GHz measurements from the RATAN-600 radio telescope, the 5 and 8 GHz data from the RT-32 telescopes, and the 37 GHz data from the RT-22 telescope. The optical measurements in the $R$-band were collected with the 1-m Zeiss-1000 and 0.5-m AS-500/2 telescopes. Additionally we used the archive data at 230~GHz from the SMA and the $\gamma$-ray data in the 0.1-100 GeV band from the Fermi-LAT point source 4FGL-DR2 catalogue. The variability properties during four epochs containing major flares and one epoch of relatively low activity were analysed. A significant correlation ($\geq\!2\sigma$) between the radio, optical, and $\gamma$-ray bands is found for all these periods with time delays from 0 to 1.7 yrs. The relation between time delay and frequency is described by a linear law with a negative slope of -10 day/GHz. The discovered properties of MW variability for the low activity period and for flaring states suggest that the mechanisms dominating the radio-$\gamma$-ray variations are not substantially different. The detected quasi-periodic oscillations of about 6 and 2 years are tentative, as the time span of the observations includes fewer than 4 full cycles for the radio and optical data and only about 3 cycles for the Fermi-LAT data. The physical parameters of the radio jet were obtained using the Hedgehog model applied to the average radio spectrum of AO 0235+164 in the range 0.1-300 GHz. The effectiveness of replacing electrons with protons in the synchrotron radio emission of relativistic jets is shown for describing the nature of blazars and the generation of high energy neutrinos.

The clustering dipole in the 2MASS galaxy survey converges on a scale of ~400Mpc to the local peculiar velocity inferred from the Cosmic-Microwave-Background dipole. I show that this limits the graviton mass in Yukawa theories of gravity to less than 5x10^{-32}eV. The new limit is 2.5x10^8 times tighter than the latest constraint from gravitational waves detected by the LIGO-Virgo-KAGRA collaboration.

The evolution and distribution of metals within galaxies are critical for understanding galactic evolution and star formation processes, but the mechanisms responsible for shaping this distribution remain uncertain. In this study we carry out high-resolution simulations of an isolated Milky Way-like galaxy, including a star-by-star treatment of both feedback and element injection. We include seven key isotopes of observational and physical interest, and which are distributed across different nucleosynthetic channels. After running the simulations to statistical steady state, we examine the spatial and temporal statistics of the metal distributions and their fluctuations. We show that these statistics reflect a mixture properties dependent on the large-scale structure of the galaxy and those that vary depending on the particular nucleosynthetic channel that dominates production of a particular isotope. The former ensure that different elements are highly-correlated with one another even if they have different nucleosynthetic origins, and their spatial correlations vary together in time. The latter means that the small variations between elements that are present naturally break them into nucleosynthetic familiars, with elements that originate from different channels correlating better with each other than with elements with different origins. Our findings suggest both challenges and opportunities for ongoing efforts to use chemical measurements of gas and stars to unravel the history and physics of galaxy assembly.

The magnetic chemically peculiar Ap stars exhibit an extreme spread of rotational velocities, the reason of which is not well understood. Ap stars with rotational periods of 50 days or longer are know as super-slowly rotating Ap (ssrAp) stars. Photometrically variable Ap stars are commonly termed alpha2 Canum Venaticorum (ACV) variables. Our study aims at enlarging the sample of known ssrAp stars using data from the Zwicky Transient Facility (ZTF) survey to enable more robust and significant statistical studies of these objects. Using selection criteria based on the known characteristics of ACV variables, candidate stars were gleaned from the ZTF catalogues of periodic and suspected variable stars and from ZTF raw data. ssrAp stars were identified from this list via their characteristic photometric properties, Delta a photometry, and spectral classification. The final sample consists of 70 new ssrAp stars, which mostly exhibit rotational periods between 50 and 200 days. The object with the longest period has a rotational period of 2551.7 days. We present astrophysical parameters and a Hertzsprung-Russell diagram for the complete sample of known ssrAp stars. With very few exceptions, the ssrAp stars are grouped in the middle of the main sequence with ages in excess of 150 Myr. ZTF J021309.72+582827.7 was identified as a possible binary star harbouring an Ap star and a cool component, possibly shrouded in dust. With our study, we enlarge the sample of known ssrAp stars by about 150%, paving the way for more in-depth statistical studies.

Small-scale brightenigs are ubiquitous, dynamic and energetic phenomena found in the chromopshere. An advanced filter-detection algorithm applied to high-resolution observations from the Interface Region Imaging Spectrograph enables the detection of these brightenings close to the noise level. This algorithm also tracks the movement of these brightenings and extracts their characteristics. This work outlines the results of an in-depth analysis of a quiet-Sun dataset including a comparison of a brighter domain - associated with a super-granular boundary - to the quiescent inter-network domains. Several characteristics of brightenings from both domains are extracted and analysed, providing a range of sizes, durations, brightness values, travel distances, and speeds. The ``Active" quiet-Sun events tend to travel shorter distances and at slower speeds along the plane-of-sky than their ``True" quiet-Sun counterparts. These results are consistent with the magnetic field model of super-granular photospheric structures and the magnetic canopy model of the chromosphere above. Spectroscopic analyses reveal that BPs demonstrate blue-shift (as well as some bi-directionality) and that they may rise from the chromosphere into the TR. We believe these bright points to be magnetic in nature, are likely the result of magnetic reconnection, and follow current sheets between magnetic field gradients, rather than along magnetic field lines themselves.

In this work, we focus on two important aspects of modern cosmology: reheating and Hubble constant tension within the framework of a unified model, namely, quintessential inflation connecting the early inflationary era and late-time cosmic acceleration. In the context of reheating, we use instant preheating and gravitational reheating, two viable reheating mechanisms when the evolution of the universe is not affected by an oscillating regime. After obtaining the reheating temperature, we analyze the number of $e$-folds and establish its relationship with the reheating temperature. This allows us to connect, for different quintessential inflation models, the reheating temperature with the spectral index of scalar perturbations, thereby enabling us to constrain its values. In the second part of this article, we explore various alternatives to address the $H_0$ tension, a discrepancy which indicates a possible revision of the $\Lambda$CDM model. Initially, we establish that quintessential inflation alone cannot mitigate the Hubble tension by solely deviating from the concordance model at low redshifts. The introduction of a phantom fluid, capable of increasing the Hubble rate at the present time, becomes a crucial element in alleviating the Hubble tension, resulting in a deviation from the $\Lambda$CDM model only at low redshifts. On a different note, by utilizing quintessential inflation as a source of early dark energy, thereby diminishing the physical size of the sound horizon close to the baryon-photon decoupling redshift, we observe a reduction in the Hubble tension. This alternative avenue, which has the same effect of a cosmological constant changing its scale close to the recombination, sheds light on the nuanced interplay between the quintessential inflation and the Hubble tension, offering a distinct perspective on addressing this cosmological challenge.

We estimate the magnetic field in the jets of the recently discovered 7 Mpc long Porphyrion system. We use non-detection of the system in gamma-rays to derive a lower bound on the co-moving magnetic field strength at the level of ~10 nG. This value is consistent with recent estimates of magnetic fields in the filaments of the Large Scale Structure. We discuss the possibility that, instead of being the extreme case of a radio jet formation scenario, Porphyrion actually traces a very-high-energy gamma-ray beam emitted by an active galactic nucleus. In such a model, jets do not need to spread into the voids of the Large Scale Structure to appear straight on a very large distance range, and several anomalies of the standard radio jet scenarios can be solved at once.

Reheating in inflationary cosmology is essential for understanding the early universe, influencing particle production, thermalization, and the primordial power spectrum. Crucial quantities defined during the reheating epoc, such as the equation of state parameter $\omega_{re}$, reheating temperature $T_{re}$, and the number of $e$-folds $N_{re}$, affect inflationary observables like the scalar spectral index $n_s$ and the tensor-to-scalar ratio $r$. We analyze two classes of inflationary models: generalized $\alpha$-attractor models and the $\alpha$-Starobinsky generalization. These models, motivated by supergravity and string theory, exhibit attractor behavior, ensuring strong predictions and have been studied extensively before. A salient novelty of this study, compared to previous works, is the inclusion of an analytical expression for the reheating temperature, $T_{\text{re}}$, which makes it a dynamical quantity. This is crucial for determining all the cosmological quantities analyzed in this work. Our results show a universal scaling behavior for a tightly bounded $T_{re}$ in both models. We believe this is the first time that $T_{re}$ is so closely determined. This work complements previous Bayesian and numerical studies by providing detailed numerical and analytical insights into the evolution of cosmological observables and reheating parameters, offering also constraints on inflationary models based on observational data.

We present the Atacama Large Millimeter/submillimeter Array Band 7 observations of the CO (J=3-2) line emission of the protostellar system HH 212 at $\sim$24 au spatial resolution and compare them to those of the SiO (J=8-7) and SO (J=8-7) line emission reported in the literature. We find that the CO line traces four distinct regions: (1) an outer outflow shell, (2) a rotating wind region between the SiO and CO shells, (3) the shocked and wide-angle inner X-wind inside a SiO shell, and (4) the jet. The origin of the CO outer outflow shell could be associated with the entrained material of the envelope, or an extended disk wind. The rotating wind, which is shocked, is launched from a radius of 9-15 au, slightly exterior to that of the previously detected SO shell, which marks the boundary where the wide-angle X-wind is interacting with and shocking the disk wind. Additionally, the SO is found to be mixed with the CO emission within the thick and extended rotating wind region. The large scale CO shocked wind coexists with the SO emission near the upper portion of the inner shocked region converged on top of the inner SiO knots. The CO jet is traced by a chain of knots with roughly equal interval, exhibiting quasi-periodicity, as reported in other jets in the literature.

Radio astronomy observatories, such as the Dominion Radio Astrophysical Observatory in Penticton, British Columbia, try to limit radio frequency interference to observe incredibly faint astronomical signals. These protective measures include placing observatories in geographically remote locations, the implementation of radio-frequency-interference-free quiet zones, or removal of interference in data processing. In 2018, we set out to explore how necessary radio-quiet zones are, by studying the radio frequency emission around the Observatory and around our local environment in Calgary, Alberta. We studied five well-used radio frequency bands and found the emission to be variable and environment dependent. While the radio frequency environment has changed since then, as a consequence of increased satellite activity and other forms of emission, we present these results as documentation of the past environment with the aim to redo the measurements. Overall, as there is use from both public and private services across the radio spectrum, protective measures at astronomical observatories are essential to reduce radio frequency interference.

The Bondi-Hoyle-Lyttleton (BHL) accretion model is widely used to describe how a compact object accretes material from a companion's stellar wind in binary systems. However, this classical model becomes inaccurate when the wind velocity ($v_\mathrm{w}$) is comparable to or less than the orbital velocity ($v_\mathrm{o}$), predicting nonphysical accretion efficiencies above unity. This limits its applicability to systems with low wind-to-orbital velocity ratios ($w= v_\mathrm{w}/v_\mathrm{o} \leq 1$), such as symbiotic systems. We revisit the BHL model and introduce a geometric correction factor that accounts for the varying orientation of the accretion cylinder relative to the wind direction. This correction ensures physically plausible accretion efficiencies ($\eta\leq 1$) for all $w$ in circular orbits. Our modified model naturally predicts the flattening of the accretion efficiency observed in numerical simulations for $w<1$, without the need for ad hoc adjustments. We also peer into the implications of our model for the less-explored case of eccentric orbits, highlighting the key role of the geometric correction factor in shaping the accretion process. We compare our predictions with numerical simulations, finding good agreement for a wide range of parameters. Applications to the symbiotic star R Aqr and the X-ray binary LS 5039 are presented. This improved model offers a more accurate description of wind accretion in binary systems, with implications for stellar evolution, population synthesis, and observational data interpretation.

Searches for ultra-high energy ($E_\nu \geq 10$ PeV) cosmogenic and astrophysical neutrinos (UHENs) have been conducted by several experiments over the last two decades. The Askaryan Radio Array (ARA), located near the geographical South Pole, was one of the first two experiments that used radio antennas sensitive to orthogonal polarizations for detection of neutrino-induced Askaryan radiation. ARA comprises five independent autonomous stations, with an additional low threshold phased array merged with station 5, which were deployed at a depth of 100-200 m over the period 2012-2018, corresponding to a total livetime of more than 27 station years. In this article, we present a brief overview of the detector, its detection technique, and discuss a few of its major achievements with a focus on the current status of the array-wide UHEN search. We expect to produce the most sensitive results on the neutrino flux by any existing in-ice neutrino experiment below 1000 EeV energy.

The Ultra Violet Imaging Telescope (UVIT) onboard India's first dedicated multiwavelength satellite \textit{AstroSat} observed a significant fraction of the sky in the ultraviolet with a spatial resolution of 1.4\arcsec. We present a catalog of the point sources observed by UVIT in the far ultraviolet (FUV; 1300-1800 Å) and near ultraviolet (NUV; 2000-3000 Å). We carried out astrometry and photometry of 428 field pointings in the FUV and 54 field pointings in the NUV band, observed in 5 filter bands in each channel respectively, covering an area of about 63 square degrees. The final catalog contains about 102,773 sources. The limiting magnitude(AB) of the F148W band filter, that has the largest number of detections is $\sim21.3$. For the NUV channel, we find the limiting magnitude at around $\sim23$. We describe the final catalog and present the results of the statistical analysis.

The radio galaxy NGC 1275, located at the central region of Perseus cluster, is a well-known very high-energy (VHE) gamma-ray emitter. The Major Atmospheric Cherenkov Experiment Telescope has detected two distinct episodes of VHE (E > 80 GeV) gamma-ray emission from NGC 1275 during 2022 December and 2023 January. The second outburst, observed on 2023 January 10, was the more intense of the two, with flux reaching 58$\%$ of the Crab Nebula flux above 80 GeV. The differential energy spectrum measured between 80 GeV and 1.5 TeV can be described by a power law with a spectral index of $\Gamma = - 2.90 \pm 0.16_{stat}$ for both flaring events. The broadband spectral energy distribution derived from these flares, along with quasisimultaneous low-energy counterparts, suggests that the observed gamma-ray emission can be explained using a homogeneous single-zone synchrotron self-Compton model. The physical parameters derived from this model for both flaring states are similar. The intermediate state observed between two flaring episodes is explained by a lower Doppler factor or magnetic field, which subsequently returned to its previous value during the high-activity state observed on 2023 January 10.

The center-to-limb variations (CLV) of transition region line Gaussian fit parameters in solar plage are reported for the first time. The Si iv 1402.77 A line observed by Interface Region Imaging Spectrograph (IRIS) is used. The spectral intensity increases linearly from the disk center to the solar limb. Similarly, the non-thermal velocity also increases linearly from 23.6 km/s (at the disk center) to 30.9 km/s (at the solar limb). On the other hand, the Doppler velocity decreases from 8.9$\pm$1.0 km/s at the disk center to 0.0 km/s at the limb. This CLV pattern in solar plages is consistent with the CLV pattern reported in the quiet-Sun (QS). However, the average values of the parameters in the solar plage are significantly higher than in the QS. The intensity and non-thermal velocity increase linearly with the magnetic field at the disk center while the Doppler velocity does not depend on the magnetic field. Due to the line-of-sight effect, the plasma column depth increases towards the solar limb which leads to a linear increase in the spectral intensity. Further, the increasing plasma column depth towards the solar limb adds more and more unresolved motions, and as a result, the non-thermal velocity increases from the disk center to the solar limb. In the solar plages, the higher plasma density due to the strong magnetic field leads to the higher intensity and non-thermal velocity compared to QS and coronal hole (CH)

We presented the first photometric analysis of the V1961 Cyg and V0890 Lyr binary systems. We observed and analyzed these systems at an observatory in France as part of the Binary Systems of South and North (BSN) Project. We extracted and collected the times of minima from the observations and literature and presented a new ephemeris for each system. Due to the few observations about these systems over the years, both O-C diagrams were fitted linearly. The PHysics Of Eclipsing BinariEs (PHOEBE) Python code and the Markov Chain Monte Carlo (MCMC) method were used to light curve solutions. The light curve solution required a cold starspot on the hotter component in the V1961 Cyg binary system. We compared and have close agreements between our mass ratios' results from the light curve analysis processes and a new method based on the light curve derivative. We estimated the absolute parameters using an empirical relationship between the semi-major axis and orbital period for contact binary systems. The results show V1961 Cyg and V0890 Lyr are W-type contact binary systems. We displayed stars and systems' positions in the M-L, M-R, and logM_{tot}-logJ_0 diagrams. We also presented a new relationship between mass ratio and luminosity ratio.

With the ongoing characterisation of the atmospheres of exoplanets by the JWST, we are unveiling a large diversity of planetary atmospheres, both in terms of composition and dynamics. As such, it is necessary to build coherent atmospheric models for exoplanetary atmospheres to study their dynamics in any regime of thickness, stratification and rotation. However, many models only partially include the Coriolis acceleration with only taking into account the local projection of the rotation vector along the vertical direction (this is the so-called "Traditional Approximation of Rotation") and do not accurately model the effects of the rotation when it dominates the stratification. In this contribution, we report the ongoing efforts to take the full Coriolis acceleration into account for the transport of momentum and the mixing of chemicals. First, we show how the horizontal local component of the rotation vector can deeply modifies the instabilities of horizontal sheared flows and the turbulence they can trigger. Next, we show how the interaction between waves and zonal winds can be drastically modified because of the modification of the wave damping or breaking when taking into account the full Coriolis acceleration. These works are devoted to improve the parameterization of waves and turbulent processes in global atmospheric models.

The problem of analytical estimation of the Lyapunov exponents and Lyapunov timescales of the motion in multiplets of interacting nonlinear resonances is considered. To this end, we elaborate a unified framework, based on the separatrix map theory, which incorporates both an earlier approach for the first fundamental model of perturbed resonance (given by the perturbed pendulum Hamiltonian) and a new one for its second fundamental model (given by the perturbed Andoyer Hamiltonian). Within this framework, new accurate estimates for the Lyapunov timescales of the inner and outer subsystems of the Solar planetary system are presented and discussed.

We present two cases of Ly$\alpha$ changing-look (CL) quasars (J1306 and J1512) along with two additional candidates (J1511 and J1602), all discovered serendipitously at $z >2$ through the Dark Energy Spectroscopic Instrument (DESI) and the Sloan Digital Sky Survey (SDSS). It is the first time to capture CL events in Ly$\alpha$ at high redshift, which is crucial for understanding underlying mechanisms driving the CL phenomenon and the evolution of high-redshift quasars and galaxies. The variability of all four sources is confirmed by the significant change of amplitude in the $r$ band ($|r_{\rm DESI}-r_{\rm SDSS}| >0.5 \ \rm mag$). We find that the accretion rate in the dim state for these CL objects corresponds to a relatively low value ($\mathscr{\dot M} \approx 2\times10^{-3}$), which suggests that the inner region of the accretion disk might be in transition between the Advection Dominated Accretion Flow ($\mathscr{\dot M}<10^{-3}\sim 10^{-2}$) and the canonical accretion disk (optically thick, geometrically thin). However, unlike in C {\sc iv} CL quasars in which broad Ly$\alpha$ remained, the broad C {\sc iv} may still persist after a CL event occurs in Ly$\alpha$, making the physical origin of the CL and ionization mechanism event more puzzling and interesting.

We present 850 $\mu$m polarization observations of the IC 348 star-forming region in the Perseus molecular cloud as part of the B-fields In STar-forming Region Observation (BISTRO) survey. We study the magnetic properties of two cores (HH 211 MMS and IC 348 MMS) and a filamentary structure of IC 348. We find that the overall field tends to be more perpendicular than parallel to the filamentary structure of the region. The polarization fraction decreases with intensity, and we estimate the trend by power-law and the mean of the Rice distribution fittings. The power indices for the cores are much smaller than 1, indicative of possible grain growth to micron size in the cores. We also measure the magnetic field strengths of the two cores and the filamentary area separately by applying the Davis-Chandrasekhar-Fermi method and its alternative version for compressed medium. The estimated mass-to-flux ratios are 0.45-2.20 and 0.63-2.76 for HH 211 MMS and IC 348 MMS, respectively, while the ratios for the filament is 0.33-1.50. This result may suggest that the transition from subcritical to supercritical conditions occurs at the core scale ($\sim$ 0.05 pc) in the region. In addition, we study the energy balance of the cores and find that the relative strength of turbulence to the magnetic field tends to be stronger for IC 348 MMS than HH 211 MMS. The result could potentially explain the different configurations inside the two cores: a single protostellar system in HH 211 MMS and multiple protostars in IC 348 MMS.

We present a comprehensive analysis of the region containing the large smooth patch on comet Tempel 1, focusing on its spectral and morphological characteristics and those of its surroundings. Utilizing observational data from the Deep Impact and Stardust-NExT missions, an updated stereophotoclinometry-based shape model, and numerical simulations, we aim to investigate the origin and evolution of this feature. Our study characterizes the morphological changes between the two mission visits, determining that the smooth patch has a thickness of approximately 25 meters. This patch is embedded in a cliff with an average height of 50 meters and exhibits a lobate U-shape morphology. Our findings support the previously suggested idea that an ice flow phenomenon is compatible with the observations. Moreover, our simulations indicate that a single phenomenon could link both the large and secondary smooth patches and the mass wasting feature observed on the comet's opposite northern face. We propose that a cryovolcano-like event may be responsible for this smooth feature, although more evidence is needed to support this hypothesis.

We present the results of deep radio observations of 7 nearby large galaxies observed using the upgraded Giant Metrewave Radio Telescope (uGMRT) 0.3-0.5 GHz receivers with an angular resolution of $\sim$10 arcsec. The achieved sensitivities of these observations range from $\approx$15 to 50 $\mu$Jy/beam which is $\approx$3-4 factor lower than the previous observations at these frequencies. For 2 galaxies (NGC3344 and NGC3627) with moderate inclination angles, significant diffuse emissions are seen for the first time. Detected radio halos in the vertical direction are significantly larger in our 0.4 GHz maps than compared to the observations at $\sim$1.5 GHz for 4 nearly edge-on galaxies - NGC3623, NGC4096, NGC4594, and NGC4631. For these 4 galaxies, significantly larger halos are also detected along the galaxy disk. For NGC3623 and NGC4594, we could detect elongated radio disks which was not seen before. We also present new uGMRT images of NGC3344 and NGC3623 at 1.3 GHz and a new VLA image of NGC3627 at 1.5 GHz. We fitted an exponential function to the flux densities along different cross-cuts and found a significantly wider distribution at 0.4 GHz uGMRT images than compared to the high-frequency images at $\sim$1.5 GHz. Using maps at 0.144, 0.4, and $\sim$1.5 GHz, we made spectral index maps of the 7 sample galaxies and found steepening of the spectrum up to a value of $\sim$ -1.5 in the halo regions of the galaxies.

With the ever-increasing number of light curve solutions of contact binary systems increasing number of potential bright red nova progenitors are being reported. There remains, however, only one confirmed event. In the present study we undertake a comprehensive review of orbital stability of contact binary systems considering the effects of the stellar internal composition (metallicity) and age on the evolution of the gyration radius and its effect on the instability mass ratio of contact binaries. We find that both metallicity and age have an independent effect on orbital stability with metal poor and older systems being more stable. The combined effects of age and metallicity are quite profound such that for most systems with primaries of solar mass or greater which are halfway or more through the main sequence lifespans have instability mass ratio at levels where the secondary component would be below the hydrogen fusion mass limit. We find that from the currently available solutions we cannot confidently assign any system as unstable. Although we identify 8 potential red nova progenitors all have methodological or astrophysical concerns which lower our confidence in designating any of them as potential merger candidates.

We study the activity evolution of the main-belt comet 324P/La Sagra over time and the properties of its emitted dust. We performed aperture photometry on images taken by a wide range of telescopes at optical and thermal infrared wavelengths between 2010 and 2021. We derived the combined scattering cross section of the nucleus and dust (when present) as a function of time, and we derived the thermal emission properties. Fitting an IAU H-G phase function to the data obtained when 324P was likely inactive, we derived an absolute nucleus magnitude $H_R = (18.4 \pm 0.5)$ mag using $G = 0.15 \pm 0.12$. The activity of 324P/La Sagra during the 2015 perihelion passage has significantly decreased compared to the previous perihelion passage in 2010, and it decreased even further during the 2021 perihelion passage. This decrease in activity may be attributed to mantling or to the depletion of volatile substances. The $Af\rho$ profile analysis of the coma of the main-belt comet suggests a near-perihelion transition from a lower-activity pre-perihelion to a higher-activity post-perihelion steady state. We calculate a dust geometric albedo in the range of (2 - 45)%, which prevents us from constraining the spectral type of 324P/La Sagra, but we found an indication of dust superheating at 4.5 micrometers.

In this paper, we present a semi-empirical calibration between the oxygen abundance and the $N2$ emission-line ratio for Low Ionization Nuclear Emission Regions (LINERs). This relation was derived by comparing the optical spectroscopic data of 118 nuclear spaxels classified as LINERs using three different BPT diagrams from the Mapping Nearby Galaxies survey (MaNGA) and sub-classified as weak (wAGN, 84 objects) and strong (sAGN, 34 objects) AGN (active galactic nucleus) from the WHAN diagnostic diagram and photoionization model results obtained with the {\sc cloudy} code assuming gas accretion into a black hole (representing an AGN). We found that our wAGN LINERs exhibit an oxygen abundance in the range of $8.50 \lesssim \mathrm{12+\log(O/H)} \lesssim 8.90 $, with an average value of $\mathrm{12+\log(O/H)}=8.68$, while our sAGN LINERs exhibit an oxygen abundance in the range of $8.51 \lesssim \: \mathrm{12+\log(O/H)} \: \lesssim \: 8.81 $, with an average value of $\mathrm{12+\log(O/H)}=8.65$. Our abundance estimations are in good agreement with those derived for another two different samples one of them with 463 Seyfert 2 objects and the other with 43 LINERs galaxies ionized by post-AGB stars, showing that the assumptions of our models are likely suitable for wAGN and sAGN LINERs. A relation between the equivalent width of the observed H$\alpha$ emission-line and the estimated ionization parameter provided by models was obtained. Our results also suggest that LINERs does not show a clear correlation between oxygen abundances and the stellar mass of the hosting galaxies.

Variations in scaling behavior in the flux and emissions of gravitational lensed quasars can provide valuable information about the dynamics within the sources and their cosmological evolution with time. Here, we study the multifractal behavior of the light curves of 14 lensed quasars with multiple images in the $r$ band, with redshift ranging from 0.657 to 2.730, in the search for potential differences in nonlinearity between the signals of the quasar multiple images. Among these lensed systems, nine present two images, two present three images, and three present four images. To this end, we apply the wavelet transform-based multifractal analysis formalism called Wavelet Transform Modulus Maxima (WTMM). We identify strong multifractal signatures in the light curves of the images of all analyzed lensed quasar systems, independently of the number of images, with a significant difference between the degree of multifractality of all the images and combinations. We have also searched for a possible connection between the degree of multifractality and the characteristic parameters related to the quasar source and the lensing galaxy. These parameters include the Einstein ring radius and the accretion disk size and the characteristic timescales related to microlensing variability. The analysis reveals some apparent trends, pointing to a decrease in the degree of multifractality with the increase of the quasar's source size and timescale. Using a larger sample and following a similar approach, the present study confirms a previous finding for the quasar Q0957+561.

Future cosmic microwave background (CMB) experiments are primarily targeting a detection of the primordial $B$-mode polarisation. The faintness of this signal requires exquisite control of systematic effects which may bias the measurements. In this work, we derive requirements on the relative calibration accuracy of the overall polarisation gain ($\Delta g_\nu$) for LiteBIRD experiment, through the application of the blind Needlet Internal Linear Combination (NILC) foreground-cleaning method. We find that minimum variance techniques, as NILC, are less affected by gain calibration uncertainties than a parametric approach, which requires a proper modelling of these instrumental effects. The tightest constraints are obtained for frequency channels where the CMB signal is relatively brighter (166 GHz channel, $\Delta {g}_\nu \approx 0.16 \%$), while, with a parametric approach, the strictest requirements were on foreground-dominated channels. We then propagate gain calibration uncertainties, corresponding to the derived requirements, into all frequency channels simultaneously. We find that the overall impact on the estimated $r$ is lower than the required budget for LiteBIRD by almost a factor $5$. The adopted procedure to derive requirements assumes a simple Galactic model. We therefore assess the robustness of obtained results against more realistic scenarios by injecting the gain calibration uncertainties, according to the requirements, into LiteBIRD simulated maps and assuming intermediate- and high-complexity sky models. In this case, we employ the so-called Multi-Clustering NILC (MC-NILC) foreground-cleaning pipeline and obtain that the impact of gain calibration uncertainties on $r$ is lower than the LiteBIRD gain systematics budget for the intermediate-complexity sky model. For the high-complexity case, instead, it would be necessary to tighten the requirements by a factor $1.8$.

The symbiotic X-ray binary GX 1+4 possesses a number of peculiar properties that have been studied since the early 1970s. In particular, the orbital period has been a point of debate for many years, until radial velocity measurements were able to settle the debate. These radial velocity findings have so far not been confirmed using X-ray data, even though multiple factors would cause a periodic variation on the same timescale as the orbital period at these energies. Because the orbit of GX 1+4 is eccentric and not seen face-on, changes in the accretion rate and column density along the line of sight could cause a periodic variation in the spin-frequency measurements, X-ray light curves, and hardness ratios of the source. Furthermore, for a high inclination of the orbital plane, the neutron star could be eclipsed by the companion, which would lead to periodic decreases in brightness. We used data from a number of different X-ray telescopes to search directly for periodicity by applying the Lomb-Scargle and epoch-folding approaches to long-term light-curve and spin-frequency measurement data of the source. We support our findings using folded light curves, hardness ratios, and images. We find that our results agree with the radial velocity findings, and we form a self-consistent model that is supported by folded hardness-ratios and light curves. We find that the source is clearly detected in X-rays during the predicted eclipse. Motivated by this absence of an eclipse in the system, we constrain the inclination of the system to $\sim 76^\circ-84^\circ$ and the mass of the neutron star in the system to $\sim1.23M_\odot - 1.45M_\odot$ using the constraints on the red giant mass and surface gravity provided in the literature. Furthermore, we constrain the radius of the red giant to $\sim 60R_\odot - 150R_\odot$.

We aim at characterizing the X-ray-to-optical/near-infrared broad-band emission of luminous QSOs in the first Gyr of cosmic evolution to understand whether they exhibit differences compared to the lower-\textit{z} QSO population. Our goal is also to provide for these objects a reliable and uniform catalog of SED fitting derivable properties such as bolometric and monochromatic luminosities, Eddington ratios, dust extinction, strength of the hot dust emission. We characterize the X-ray/UV emission of each QSO using average SEDs from luminous Type 1 sources and calculate bolometric and monochromatic luminosities. Finally we construct a mean SED extending from the X-rays to the NIR bands. We find that the UV-optical emission of these QSOs can be modelled with templates of $z\sim$2 luminous QSOs. We observe that the bolometric luminosities derived adopting some bolometric corrections at 3000 Å ($BC_{3000\textÅ}$) largely used in the literature are slightly overestimated by 0.13 dex as they also include reprocessed IR emission. We estimate a revised value, i.e. $BC_{3000\textÅ}=3.3 $ which can be used for deriving $L_\text{bol}$ in \textit{z} $\geq$ 6 QSOs. A sub-sample of 11 QSOs is provided with rest-frame NIR photometry, showing a broad range of hot dust emission strength, with two sources exhibiting low levels of emission. Despite potential observational biases arising from non-uniform photometric coverage and selection biases, we produce a X-ray-to-NIR mean SED for QSOs at \textit{z} $\gtrsim$ 6, revealing a good match with templates of lower-redshift, luminous QSOs up to the UV-optical range, with a slightly enhanced contribution from hot dust in the NIR.

The appearance of the jets and lobes of some radio galaxies makes it difficult to assign them to a known class of objects. This is often due to the activity of the central engine and/or interactions with the environment, as well as projection effects. We analyse the radio data for an apparently asymmetric radio source 4C70.19, which is associated with the giant elliptical galaxy NGC6048. The source shows distorted radio jets and lobes, one of which bends by 180 degrees. The aim of our study is to explain the nature of the observed distortions. We used LOFAR, Effelsberg, and VLA radio data in a wide range of frequencies. At high frequencies, we also used radio polarimetry to study the properties of the magnetic fields. Additionally, we made use of optical, infra-red, and X-ray data. Polarisation data suggest shearing of the magnetic fields at points where the jets bend. The low-frequency LOFAR map at 145 MHz, as well as the sensitive single-dish Effelsberg map at 8.35 GHz, reveal previously undetected diffuse emission around the source. The rotation measure (RM) derived from the polarimetric data allowed us to estimate the density of the medium surrounding the source, which agrees with typical densities of the intergalactic medium or the outer parts of insterstellar halos. We propose that the southern jet is bent in the same manner as the northern one, but that it is inclined to the sky plane. Both these bends are likely caused by the orbital motion within the galaxy group, as well as interactions with the intergalactic medium. Our analyses suggest that, despite its complex morphology, 4C70.19 seems to be intrinsically symmetric with a physical extent of up to 600 kpc, and that the diffuse emission detected in our high-sensitivity maps is related to radio plumes that are expanding behind the source.

PSR B1259-63 is a gamma-ray binary system with a 48 ms radio pulsar orbiting around an O9.5Ve star, LS 2883, in a highly eccentric ~3.4 yr long orbit. Close to the periastron the system is detected from radio up to the TeV energies due to the interaction of LS 2883 and pulsar's outflows. The observations of last 4 periastra passages taken in 2010-2021 demonstrate periastron to periastron variability at all wavelength, probably linked to the state of the decretion disk. In this paper we present the results of our optical, radio and X-ray observational campaigns on PSR B1259-63 performed in 2024 accompanied with the analysis of the publicly available GeV FERMI/LAT data. We show that this periastron passage was characterised by the early flaring of X-rays before the periastron passage and GeV emission after the periastron passage, which can be explained by a larger size of the decretion disk as supported by the optical observations. The structure of the GeV flare is also in agreement with the disruption of the large dense disk. The possible X-ray/radio correlation was observed only during the post-periastron rise of X-ray and radio emission.

In this work we investigate the effects of the environment on the evolution of void galaxies. In particular, we study their morphology and explore its dependence with their location within the void where the galaxies reside, as well as with properties of the void, such as void size or galaxy number-density. The sample of void galaxies that we use in this study is based on the catalogue of cosmic voids and void galaxies in the SDSS-DR7. Since we are interested into study the morphology of void galaxies, we select galaxies in the redshift range 0.005$\leq$z$\leq$0.080, and use the public galaxy morphologies for SDSS with Deep Learning algorithms to divide the sample between early- and late-type void galaxies. We analyse the fraction of galaxies of each morphology type as a function of the void-centric distance, the size of the voids, and the density of galaxies in each void. There is a higher abundance of late-type galaxies with respect to early-type galaxies within voids, which remains nearly constant from the inner to the outer part of the voids. We do not find any dependence of the fraction of early- and late-type galaxies with respect to the size of the voids or the number-density of galaxies in the voids. Galaxies in voids follow the morphology-density relation, in the sense that the majority of the galaxies in voids (the most under-dense large-scale environments) are late-type galaxies. However, we find no difference between voids with lower or higher volume number-density of galaxies: the fraction of early- and late-type galaxies do not depend on the density of the voids. The physical processes responsible for the evolution from late towards earlier types (such as external environmental quenching) are not sufficiently effective in voids or so slow (internal secular quenching) that their contributions do not appear in the morphology-density relation.

We propose a novel microlensing event search method that differs from either the traditional time domain method, astrometric microlensing, or the parallax microlensing method. Our method assumes that stars with nearly identical "genes" - normalized Spectral Energy Distributions (SED) bear the same luminosity within the intrinsic scatter due to stellar properties. Given a sample of stars with similar normalized SEDs, the outliers in luminosity distribution can be considered microlensing events by excluding other possible variations. In this case, we can select microlensing events from archive data rather than time domain monitoring the sky, which we describe as static microlensing. Following this concept, we collect the data from Gaia DR3 and SDSS DR16 from the northern galactic cap at high galactic latitudes. This area is not preferable for normal microlensing search due to the low stellar density and, therefore, low discovery rate. By applying a similarity search algorithm, we find 5 microlensing candidates in the Galactic halo.

Context. Kinematically decoupled cores (KDCs) are often found in the centers of early-type galaxies. Aims. We aim to investigate the kinematics, structure, and stellar populations of the KDC residing in the early-type galaxy NGC 4494 to understand its formation. Methods. We used long-slit spectroscopic data obtained with the FORS2 instrument on the VLT to measure the stellar kinematics and stellar populations. We performed a spectroscopic decomposition to disentangle the properties of the KDC from those of the host galaxy and construct models of the observed rotation curve. Results. The rotation curve is characterized by two symmetric dips at |R|=6", where the rotation velocity drops to zero. Contrary to previous studies that explained the decoupled structure as a rapidly co-rotating disk, our analysis clearly shows that it is a counter-rotating component. A counter-rotating core is indeed needed to reproduce the observed dip in the velocity curve. The properties of the stellar populations of the decoupled core and the main galaxy are very similar: old stars (12-13 Gyr) with slightly super-solar metallicities (0<[Z/H]<0.15 dex) and alpha-enhanced (0 <[alpha/Fe]< 0.15 dex). Conclusions. Our results indicate that the counter-rotating component is a disk of about 1 kpc in diameter that is obscured by dust in the central 0.12 kpc. The properties of its stellar populations suggest that it formed from the same material as the main stellar body of the host galaxy. This could have happened via internal processes such as the precession of a pre-existing rotating core, or, alternatively, via gas accretion in retrograde orbits followed by star formation. In the latter scenario, the accretion event occurred almost simultaneously with the formation of the galaxy, using material that had the same composition as the gas from which the stars in the main body of the galaxy were formed.

Fast-mode magnetohydrodynamic (MHD) waves in the solar corona are often known to be produced by solar flares and eruptive prominences. We here simulate the effect of the interaction of an external perturbation on a magnetic null in the solar corona which results in the formation of a current sheet (CS). Once the CS undergoes a sufficient extension in its length and squeezing of its width, it may go unstable to the formation of multiple impulsive plasmoids. Eventually, the plasmoids merge with one another to form larger plasmoids and/or are expelled from the sheet. The formation, motion and coalescence of plasmoids with each other and with magnetic Y-points at the outer periphery of the extended CS are found to generate wave-like perturbations. An analysis of the resultant quasi-periodic variations of pressure, density, velocity and magnetic field at certain locations in the model corona indicate that these waves are predominantly fast-mode magnetoacoustic waves. For typical coronal parameters, the resultant propagating waves carry an energy flux of $\mathrm{10^{5}~\mathrm{erg~cm^{-2}~s^{-1}}}$ to a large distance of at least 60 Mm away from the current sheet. In general, we suggest that both waves and reconnection play a role in heating the solar atmosphere and driving the solar wind and may interact with one another in a manner that we refer to as a $"$Symbiosis of WAves and Reconnection (SWAR)$"$.

Fast radio bursts (FRBs) represent one of the most intriguing phenomena in modern astrophysics. However, their classification into repeaters and non-repeaters is challenging. Here, we present the application of the graph theory Minimum Spanning Tree (MST) methodology as an unsupervised classifier of repeaters and non-repeaters FRBs. By constructing MSTs based on various combinations of variables, we identify those that lead to MSTs that exhibit a localized high density of repeaters at each side of the node with the largest betweenness centrality. Comparing the separation power of this methodology against known machine learning methods, and with the random expectation results, we assess the efficiency of the MST-based approach to unravel the physical implications behind the graph pattern. We finally propose a list of potential repeater candidates derived from the analysis using the MST.

JWST, despite not being designed to observe astrophysical phenomena that vary on rapid time scales, can be an unparalleled tool for such studies. If timing systematics can be controlled, JWST will be able to open up the sub-second infrared timescale regime. Rapid time-domain studies, such as lag measurements in accreting compact objects and Solar System stellar occultations, require both precise inter-frame timing and knowing when a time series begins to an absolute accuracy significantly below 1s. In this work we present two long-duration observations of the deeply eclipsing double white dwarf system ZTF J153932.16+502738.8, which we use as a natural timing calibrator to measure the absolute timing accuracy of JWST's clock. From our two epochs, we measure an average clock accuracy of $0.12\pm0.06$s, implying that JWST can be used for sub-second time-resolution studies down to the $\sim100$ms level, a factor $\sim5$ improvement upon the pre-launch clock accuracy requirement. We also find an asymmetric eclipse profile in the F322W2 band, which we suggest has a physical origin.

This paper describes a new way of determining the high-latitude solar rotation rate statistically from simultaneous observations of many polar faculae. In this experiment, I extracted frames from a movie made previously from flat-fielded images obtained in the 6767 A continuum during February 1997-1998 and used those frames to construct space-time maps from high-latitude slices of the favorably oriented south polar cap. These maps show an array of slanted tracks whose average slope indicates the east-west speed of faculae at that latitude, Ls. When the slopes are measured and plotted as a function of latitude, they show relatively little scatter 0.01-02 km/s from a straight line whose zero-speed extension passes through the Sun's south pole. This means that the speed, v(Ls), and the latitudinal radius, R cos(Ls), approach 0 at the same rate, so that their ratio gives a nearly constant synodic rotation rate 8.6 deg/day surrounding the Sun's south pole. A few measurements of the unfavorably oriented north polar cap are consistent with these measurements near the south pole.

The worlds of Data Science (including big and/or federated data, machine learning, etc) and Astrophysics started merging almost two decades ago. For instance, around 2005, international initiatives such as the Virtual Observatory framework rose to standardize the way we publish and transfer data, enabling new tools such as VOSA (SED Virtual Observatory Analyzer) to come to existence and remain relevant today. More recently, new facilities like the Vera Rubin Observatory, serve as motivation to develop efficient and extremely fast (very often deep learning based) methodologies in order to fully exploit the informational content of the vast Legacy Survey of Space and Time (LSST) dataset. However, fundamental changes in the way we explore and analyze data cannot permeate in the "astrophysical sociology and idiosyncrasy" without adequate training. In this talk, I will focus on one specific initiative that has been extremely successful and is based on "learning by doing": the La Serena School for Data Science. I will also briefly touch on a different successful approach: a series of schools organized by the Spanish Virtual Observatory. The common denominator among the two kinds of schools is to present the students with real scientific problems that benefit from the concepts / methodologies taught. On the other hand, the demographics targeted by both initiatives vary significantly and can represent examples of two "flavours" to be followed by others.

Measuring the Hubble constant (H$_0$) is one of the most important missions in astronomy. Nevertheless, recent studies exhibit differences between the employed methods. Fast radio bursts (FRBs) are coherent radio transients with large dispersion measures (DM) with a duration of milliseconds. DM$_{\rm IGM}$, DM in the intergalactic medium (IGM), could open a new avenue for probing H$_0$. However, it has been challenging to separate DM contributions from different components (i.e., the IGM and the host galaxy plasma), and this hampers the accurate measurements of DM$_{\rm IGM}$ and hence H$_0$. We adopted a method to overcome this problem by using the temporal scattering of the FRB pulses due to the propagation effect through the host galaxy plasma (scattering time). The scattering-inferred DM in a host galaxy improves the estimate of DM$_{\rm IGM}$, which in turn leads to a better constraint on H$_0$. In previous studies, a certain value or distribution has conventionally been assumed of the dispersion measure in host galaxies (DM$_{\rm h}$). We compared this method with ours by generating 100 mock FRBs, and we found that our method reduces the systematic (statistical) error of H$_0$ by 9.1% (1%) compared to the previous method. We applied our method to 30 localized FRB sources with both scattering and spectroscopic redshift measurements to constrain H$_0$. Our result is H$_0$=74$_{-7.2}^{+7.5}$ km s$^{-1}$ Mpc$^{-1}$, where the central value prefers the value obtained from local measurements over the cosmic microwave background. We also measured DM$_{\rm h}$ with a median value of $103^{+68}_{-48}$ pc cm$^{-3}$. The reduction in systematic error is comparable to the Hubble tension ($\sim10$%). Combined with the fact that more localized FRBs will become available, our result indicates that our method can be used to address the Hubble tension using future FRB samples.

The complex astrophysical processes leading to the formation of binary black holes and their eventual merger are imprinted on the spins of the individual black holes. We revisit the astrophysical distribution of those spins based on gravitational waves from the third gravitational wave transient catalog GWTC-3, (Abbott et al. 2023a), looking for structure in the two-dimensional space defined by the dimensionless spin magnitudes of the heavier ($\chi_1$) and lighter ($\chi_2$) component black holes. We find support for two distinct subpopulations with greater than $95\%$ credibility. The dominant population is made up of black holes with small spins, preferring $\chi_1 \approx 0.2$ for the primary and $\chi_2 \approx 0$ for the secondary; we report signs of an anticorrelation between $\chi_1$ and $\chi_2$, as well as as evidence against a subpopulation of binaries in which both components are nonspinning. The subdominant population consists of systems in which both black holes have relatively high spins and contains $20^{+18}_{-18}\%$ of the binaries. The binaries that are most likely to belong in this subpopulation are massive and slightly more likely to have spin-orientations aligned with the orbital angular momentum--potentially consistent with isolated binary formation channels capable of producing large spins, like chemically homogeneous evolution. This hint of a rapidly spinning subpopulation hinges on GW190517, a binary with large and well-measured spins. Our results, which are enabled by novel hierarchical inference methods, represent a first step towards more descriptive population models for black hole spins, and will be strengthened or refuted by the large number of gravitational wave detections expected in the next several years.

Primordial oscillatory features in the power spectrum of curvature perturbations are sensitive probes of the dynamics of the early Universe and can provide insights beyond the standard inflationary scenario. While these features have been the focus of extensive studies using cosmic microwave background anisotropy data, large-scale structure surveys now provide the opportunity to probe their effects at smaller scales with higher precision. In this paper, we present a complete description of the nonlinear model for primordial oscillatory features in the context of time-sliced perturbation theory extending the results already presented in the literature. We derive analytical expressions including novel contributions such as the mixed term between primordial oscillations and baryon acoustic oscillations, and we also calculate the corrections arising from the specific envelope of the oscillatory pattern, corresponding to a scale-dependent amplitude. These results are compared with N-body simulations using the COLA method and show consistent behaviour across different scales. Although the corrections are found to be small, they represent an important step towards fully characterising the nonlinear imprints of primordial features on the matter power spectrum. Our results offer new predictions for future cosmological surveys that seek to detect these subtle signatures in the matter distribution.

Cosmic dust plays a crucial role in the evolution of galaxies, significantly influencing star formation and the interstellar medium. However, in active galactic nuclei (AGN), the role and origin of dust remain poorly understood. High-resolution X-ray spectroscopy is a powerful tool for probing the properties of dust in AGN. NGC 6860, an X-ray bright type-1 quasar, is an ideal target for investigating the connection between dust and winds in AGN. It exhibits reddening and X-ray absorption by both dust and winds. By modeling high-resolution X-ray spectra from XMM-Newton and Chandra observations, we determine the properties of dust and outflows in this AGN. Our analysis finds four photoionized components, outflowing with velocities of 50-300 km/s. The first two are relatively highly ionized with logxi = 3.4 and logxi = 2.9. The results of our photoionization modeling suggest that these two components are thermally unstable. The third component is ionized, with logxi = 2.3 and is located further away from the central black hole. The fourth component is less ionized, and is possibly located in the host galaxy. The application of dust models enables us to probe the abundance and location of the dust in NGC 6860. Our findings suggest that dust absorption and reddening originates from the extended narrow-line region and its host galaxy.

Recent observations of volume-limited samples of magnetic white dwarfs (WD) have revealed a higher incidence of magnetism in older WDs. Specifically, these studies indicate that magnetism is more prevalent in WDs with fully or partially crystallized cores compared to those with entirely liquid cores. This has led to the recognition of a crystallization-driven dynamo as an important mechanism for explaining magnetism in isolated WDs. However, recent simulations challenged the capability of this mechanism to match both the incidence of magnetism and the field strengths detected in WDs. In this letter, we explore an alternative hypothesis for the surface emergence of magnetic fields in isolated WDs. WDs with masses $\gtrsim 0.55 M_\odot$ are the descendants of main-sequence stars with convective cores capable of generating strong dynamo magnetic fields. This idea is supported by asteroseismic evidence of strong magnetic fields buried within the interiors of red giant branch stars. Assuming that these fields are disrupted by subsequent convective zones, we have estimated magnetic breakout times for WDs. Due to the significant uncertainties in breakout times stemming from the treatment of convective boundaries and mass loss rates, we cannot provide a precise prediction for the emergence time of the main-sequence dynamo field. However, we can predict that this emergence should occur during the WD phase for WDs with masses $\gtrsim 0.65 M_\odot$. We also find that the magnetic breakout is expected to occur earlier in more massive WDs, consistently with observations from volume-limited samples and the well-established fact that magnetic WDs tend to be more massive than non-magnetic ones. Moreover, within the uncertainties of stellar evolutionary models, we find that the emergence of main-sequence dynamo magnetic fields can account for a significant portion of the magnetic WDs.

Context. Many Milky Way globular clusters (GCs) host multiple stellar populations, challenging the traditional view of GCs as single-population systems. It has been suggested that second-generation stars could form in a disk from gas lost by first-generation stars or from external accreted gas. Aims. We investigate how the introduction of a second stellar generation affects mass loss, internal mixing, and rotational properties of GCs in a time-varying Galactic tidal field and different orbital configurations. Methods. We conducted direct N-body simulations of GCs on three types of orbits derived from the observed Milky Way GCs. We evolved the clusters for 8 Gyr in the time-varying Galactic potential of the IllustrisTNG-100 cosmological simulation. After 2 Gyr, we introduced a second stellar generation, comprising 5% of the initial mass of the first generation, as a flattened disk of stars. For comparison, we ran control simulations using a static Galactic potential and isolated clusters. Results. We present the mass loss, structural evolution, and kinematic properties of GCs with two stellar generations, focusing on tidal mass, half-mass radii, velocity distributions, and angular momentum. Conclusions. Our results show that the mass loss of GCs depends primarily on their orbital parameters, with tighter orbits leading to higher mass loss. The Galaxy's growth resulted in tighter orbits, meaning GCs lost less mass than if its mass had always been constant. The initially flattened second-generation disk became nearly spherical within one relaxation time. However, whether its distinct rotational signature was retained depends on the orbit: for the long radial orbit, it vanished quickly; for the tube orbit, it lasted several Gyr; but for the circular orbit, rotation persisted until the present day

Recent theoretical work and targeted observational studies suggest that filaments are sites of galaxy preprocessing. The aim of the WISESize project is to directly probe galaxies over the full range of environments to quantify and characterize extrinsic galaxy quenching in the local Universe. In this paper, we use GALFIT to measure the infrared 12$\mu$m ($R_{12}$) and 3.4$\mu$m ($R_{3.4}$) effective radii of 603 late-type galaxies in and surrounding the Virgo cluster. We find that Virgo cluster galaxies show smaller star-forming disks relative to their field counterparts at the $2.5\sigma$ level, while filament galaxies show smaller star-forming disks to almost $1.5\sigma$. Our data, therefore, show that cluster galaxies experience significant effects on their star-forming disks prior to their final quenching period. There is also tentative support for the hypothesis that galaxies are preprocessed in filamentary regions surrounding clusters. On the other hand, galaxies belonging to rich groups and poor groups do not differ significantly from those in the field. We additionally find hints of a positive correlation between stellar mass and size ratio for both rich group and filament galaxies, though the uncertainties on these data are consistent with no correlation. We compare our size measurements with the predictions from two variants of a state-of-the-art semi-analytic model (SAM), one which includes starvation and the other incorporating both starvation and ram-pressure stripping (RPS). Our data appear to disfavor the SAM, which includes RPS for the rich group, filament, and cluster samples, which contributes to improved constraints for general models of galaxy quenching.

Whether considering rare astrophysical events on cosmological scales or unresolved stellar populations, accurate models must account for the integrated contribution from the entire history of star formation upon which that population is built. Here, we describe the second version of POSYDON, an open-source binary population synthesis code based on extensive grids of detailed binary evolution models computed using the MESA code, which follows both stars' structures as a binary system evolves through its complete evolution from the zero-age main sequence, through multiple phases of mass transfer and supernovae, to their death as compact objects. To generate synthetic binary populations, POSYDON uses advanced methods to interpolate between our large, densely spaced grids of simulated binaries. In our updated version of POSYDON, we account for the evolution of stellar binaries across a cosmological range of metallicities, extending from $10^{-4}\,Z_{\odot}$ to $2\,Z_{\odot}$, including grids specifically focused on the Small and Large Magellanic Clouds ($0.2\,Z_{\odot}$ and $0.45\,Z_{\odot}$). In addition to describing our model grids and detailing our methodology, we outline several improvements to POSYDON. These include the incorporation of single stars in stellar populations, a treatment for stellar mergers, and a careful modeling of "reverse-mass transferring" binaries, in which an once-accreting star later becomes a donor star. Our simulations are focused on binaries with at least one high-mass component, such as those that host neutron stars and black holes, and we provide post-processing methods to account for the cosmological evolution of metallicity and star formation as well as rate calculations for gravitational wave events, gamma-ray bursts, and other transients.

Model mis-specification (e.g. the presence of outliers) is commonly encountered in astronomical analyses, often requiring the use of ad hoc algorithms (e.g. sigma-clipping). We develop and implement a generic Bayesian approach to linear regression, based on Student's t-distributions, that is robust to outliers and mis-specification of the noise model. Our method is validated using simulated datasets with various degrees of model mis-specification; the derived constraints are shown to be systematically less biased than those from a similar model using normal distributions. We demonstrate that, for a dataset without outliers, a worst-case inference using t-distributions would give unbiased results with $\lesssim\!10$ per cent increase in the reported parameter uncertainties. We also compare with existing analyses of real-world datasets, finding qualitatively different results where normal distributions have been used and agreement where more robust methods have been applied. A Python implementation of this model, t-cup, is made available for others to use.

The way we look at the sky is connected to the cosmological paradigm embraced by the society we live in. On the other hand, several astronomical concepts reinforce the idea of a common humanity. Yet, scientific outreach is frequenty reaching out only to a specific part of the world population, often excluding people living in extreme social vulnerability, victims of violence and prejudice, fighting for their lives and for the right of living according to their traditions. We present two outreach projects, developed in Brazil, funded by the Office of Astronomy for Development (OAD) of the International Astronomical Union (IAU), i.e. 'Under Other Skies' and 'OruMbya', which tackle the importance of ethno-astronomy, and the collaboration with leaders and cultural agents of marginalised communities. We also describe an educational project born in the favela of Cantagalo Pavão Pavaãzinho (PPG), in Rio de Janeiro, during the COVID19 pandemic, which started a collaboration with local educators and artists to offer classes of astronomy and English language to children in the favela

The Newtonian restricted three-body problem involving a positive primary point mass, $m_+$, and a negative secondary point mass, $m_-$, in a circular orbit, and a positive or negative tertiary point mass, $m_3$, with $m_+ > |m_-| \gg |m_3|$, is solved. Five Lagrange points are found for $m_3$, three of which are coplanar with $m_+$ and $m_-$, and two of which are not, a subtle consequence of the gravitational repulsion from $m_-$. All Lagrange points are linearly unstable, except for one point in the regime $m_+ \gtrsim 8.4 |m_-|$, which is linearly stable and collinear with $m_+$ and $m_-$.

Recent nonmagnetized studies of binary neutron star mergers have indicated the possibility of identifying equation of state features, such as a phase transition or a quark-hadron crossover, based on the frequency shift of the main peak in the postmerger gravitational wave spectrum. By performing a series of general relativistic, magnetohydrodynamic simulations we show that similar frequency shifts can be obtained due to the effect of the magnetic field. The existing degeneracy can either mask or nullify a shift due to a specific equation of state feature, and therefore the interpretation of observational data is more complicated than previously thought, requiring a more complete treatment that would necessarily include the neutron star's magnetic field.

The oscillation modes of neutron star (NS) merger remnants, as encoded by the kHz postmerger gravitational wave (GW) signal, hold great potential for constraining the as-yet undetermined equation of state (EOS) of dense nuclear matter. Previous works have used numerical relativity simulations to derive quasi-universal relations for the key oscillation frequencies, but most of them omit the effects of a magnetic field. We conduct full general-relativistic magnetohydrodynamics simulations of NSNS mergers with two different masses and two different EOSs (SLy and ALF2) with three different initial magnetic field topologies (poloidal and toroidal only, confined to the interior, and "pulsar-like": dipolar poloidal extending from the interior to the exterior), with four different initial magnetic field strengths. We find that the magnetic braking and magnetic effective turbulent viscosity drives the merger remnants towards uniform rotation and increases their overall angular momentum loss. This causes the remnant to contract and the angular velocity of the quadrupole density oscillation to increase in such a way that it rotates faster than the fluid itself, in stark contrast with nonmagnetized simulations. As a result, the $f_2$ frequency of the dominant postmerger GW mode shifts upwards over time. The overall shift is up to ~ 200Hz for the strongest magnetic field we consider and ~ 50Hz for the median case and is therefore detectable in principle by future GW observatories, which should include the magnetic field in their analyses.

Richardson-Lucy deconvolution is widely used to restore images from degradation caused by the broadening effects of a point spread function and corruption by photon shot noise, in order to recover an underlying object. In practice, this is achieved by iteratively maximizing a Poisson emission likelihood. However, the RL algorithm is known to prefer sparse solutions and overfit noise, leading to high-frequency artifacts. The structure of these artifacts is sensitive to the number of RL iterations, and this parameter is typically hand-tuned to achieve reasonable perceptual quality of the inferred object. Overfitting can be mitigated by introducing tunable regularizers or other ad hoc iteration cutoffs in the optimization as otherwise incorporating fully realistic models can introduce computational bottlenecks. To resolve these problems, we present Bayesian deconvolution, a rigorous deconvolution framework that combines a physically accurate image formation model avoiding the challenges inherent to the RL approach. Our approach achieves deconvolution while satisfying the following desiderata: I deconvolution is performed in the spatial domain (as opposed to the frequency domain) where all known noise sources are accurately modeled and integrated in the spirit of providing full probability distributions over the density of the putative object recovered; II the probability distribution is estimated without making assumptions on the sparsity or continuity of the underlying object; III unsupervised inference is performed and converges to a stable solution with no user-dependent parameter tuning or iteration cutoff; IV deconvolution produces strictly positive solutions; and V implementation is amenable to fast, parallelizable computation.

As millimeter-wave cosmology experiments refine their optical chains, precisely characterizing their optical materials under cryogenic conditions becomes increasingly important. For instance, as the aperture sizes and bandwidths of millimeter-wave receivers increase, the design of antireflection coatings becomes progressively more constrained by an accurate measure of material optical properties in order to achieve forecasted performance. Likewise, understanding dielectric and scattering losses is relevant to photon noise modeling in presently-deploying receivers such as BICEP Array and especially to future experiments such as CMB-S4. Additionally, the design of refractive elements such as lenses necessitates an accurate measure of the refractive index. High quality factor Fabry-Pérot open resonant cavities provide an elegant means for measuring these optical properties. Employing a hemispherical resonator that is compatible with a quick-turnaround 4 Kelvin cryostat, we can measure the dielectric and scattering losses of low-loss materials at both ambient and cryogenic temperatures. We review the design, characterization, and metrological applications of quasioptical cavities commissioned for measuring the dielectric materials in the BICEP3 (95 GHz) and BICEP Array mid-frequency (150 GHz) optics. We also discuss the efforts to improve the finesse of said cavities, for better resolution of degenerate higher order modes, which can provide stronger constraints on cavity parameters and sample material thickness.

The quark star is such an exotic star of our Universe. The limiting mass for quark stars essentially depends on rotational frequency apart from bag constant and other fundamental parameters. The analytical results obtained agree with the results of several relevant numerical estimates as well as observational evidence. Primordial black hole (PBH) is another hypothetical candidate of compact astrophysical objects. We explore the combined effect of PBH evaporation and the baryon-dark matter (DM) interaction in the 21cm scenario. We address both upper and lower bounds on several PBH and DM parameters using the observational excess (-500^{+200}_{-500} mK) of EDGES's experimental results. A similar investigation has been carried out in the framework of interacting dark energy (IDE) models. We consider three IDE models and eventually measure the allowed limits of IDE coupling parameters for individual cases. Keeping in view of the 21cm scenario, we also explore the multimessenger signals from possible rare decay of fundamental Heavy Dark Matters (HDM). HDM can undergo QCD cascade decay to produce leptons or $\gamma$ as end products. One of the multimessenger signals could be the source of ultra high energy neutrino ($\sim$PeV) signals at the IceCube detector whereas the other signal attributes to the cooling/heating of the baryons due to HDM decay and corresponding influences in the global 21cm signal. The consequence of late time decay of such HDMs may also have significant implications on the aspect of matter-antimatter asymmetry. The mass and lifetime of such Dark Matter particles have been obtained by performing a $\chi^2$ analysis with the PeV neutrino data of IceCube and finally, the amount of baryon asymmetry produced in the Universe is estimated if caused by Dark Matter decay.

Assuming that a cosmological model can describe the whole Universe history, we look for the conditions of a cosmological bounce thus in agreement with late time observations. Our approach involves casting such a theory into General Relativity with curvature ($\Omega_{\kappa}$), matter ($\Omega_{m}$), radiation ($\Omega_{r}$) and an effective dark fluid ($\Omega_{d}$) and formulating the corresponding field equations as a 2D dynamical system, wherein phase space points corresponding to extrema of the metric function are constrained by observational data. We show that if this effective dark fluid density is positive at the bounce, these observational constraints imply its occurrence in the future at a redshift $z<-0.81$ whatever the cosmological model (dark energy, brane, $f(R)$, etc.) corresponding to this effective dark fluid and even with a positive curvature. Hence, the effective dark fluid density must be negative at the bounce such as it arises for $z>-0.81$ and thus possibly in the past. Observations also impose that the dark fluid effective density can change sign only within the redshift range $0.54<z<0.61$. We then proceed by examining 3 cosmological models: a non linear dark fluid model, a Randall Sundrum brane model and a $f(R)=R+mR^n+\Lambda$ model. For each of them, we examine the conditions for (1) a bounce at early time, (2) with a negative effective dark fluid energy density, (3) this having to change sign within the above specified redshift interval. We find that none of these three models satisfy all three constraints. We conclude that while a negative effective dark fluid energy density required by observational constraints for a bounce at early times facilitates this bounce, the requirement for $\Omega_d$ to change sign and become positive within the above specified narrow redshift interval proves exceedingly challenging to satisfy these same constraints.

We present the characterization of cosmogenic muon backgrounds for the Colorado Underground Research Institute (CURIE), located in the Edgar Experimental Mine (EEM) in Idaho Springs, Colorado. The CURIE facility at the EEM offers a versatile shallow underground environment, with accessible horizontal tunnel access and stable rock formations ideal for low-background physics experiments. We have measured the total underground muon flux in two locations, Site 0 and Site 1, yielding values of $\phi$ = 0.246 $\pm$ 0.020$_{sys.}$ $\pm$ 0.012$_{stat.}$ and 0.239 $\pm$ 0.025$_{sys.}$ $\pm$ 0.010$_{stat.}$ $\mu\text{/}m^{2}\text{/}s$, respectively. We have utilized GEANT4 and PROPOSAL Monte Carlo simulations with Daemonflux and MUTE to model the muon flux at both sites, as well as an additional future location. We find good agreement between measurement and simulations, demonstrating the first instance of this computational framework being successfully used for depths $<$ 1 km.w.e. The measured underground flux corresponds to a factor of 700 reduction compared to the sea level flux. Additionally, we present a new depth-intensity relationship to normalize the mountain overburden to an equivalent flat depth, enabling direct comparison with other underground facilities. We report an average equivalent vertical depth of 0.415 $\pm$ 0.027 km.w.e. Based on our measurements, this work highlights the facility's capability for hosting low-background experiments, addressing the demand for shallow underground research spaces.

In this article we calculate the reheating temperature in the cosmological scenarios where heavy scalar particles are gravitationally produced, due to a conformally coupled interaction between a massive scalar quantum field and the Ricci scalar, during the oscillations of the inflaton field. We explore two distinct cases, namely the one in which these particles decay during the domination of the inflaton's energy density and the other one where the decay occurs after this phase. For each scenario, we have derived formulas to calculate the reheating temperatures based on the energy density of the produced particles and their decay rate. We establish bounds for the maximum reheating temperature, defined as the temperature reached by the universe when the decay of gravitationally produced particles concludes at the onset of the radiation-dominated epoch. Finally, we use the Born approximation to find analytic formulas for the reheating temperature.

In this work, we study the gravitational collapse procedure in generalized Vaidya spacetime with Bose-Einstein condensate dark matter density profile. We use the generalized Vaidya metric to simulate the spacetime of a big star and subsequently obtain the field equations. Then we proceed to determine the star system's mass parameter by solving the field equations. Then the gravitational collapse mechanism is investigated using the derived solutions. Investigating the nature of the singularity (if formed) as the end state of the collapse is the main goal. Dark matter in the form of Bose-Einstein condensate is expected to play a crucial role in the fate of the collapse. We see that there is a possibility of the formation of both black holes and naked singularities as the end state of the collapse depending upon the initial conditions. The junction conditions are derived with a Vaidya exterior and a Friedmann interior and some important insights are obtained. A Penrose diagram showing the causal relations between the spacetimes is generated and studied in detail.

Experiments conducted since 2018, using three geographically spaced synchronized radio telescopes, and a radio interferometer, indicate the presence of anomalous narrow bandwidth pulse pairs, conjectured to be sourced from a celestial direction near the star Rigel. Many explanatory hypotheses are possible. In the current work, a measurement method is proposed and implemented to attempt to provide high levels of statistical power of narrowband pulse pair observations, while minimizing interferometer instrument adjustments that might bias the experiment. Using the proposed method, twenty pulse pairs having statistical power at 5 to 10 standard deviations, and one pulse pair at 22 standard deviations of mean shift of pulse pair count, were observed in the prior celestial direction range, while using other celestial directions as an experimental comparison group. High levels of standard deviations of pulse pair count mean shift, observed in this 92 day experiment, imply the falsification of a Gaussian noise hypothesis. Alternate and auxiliary hypotheses, and further experiments, are sought to try to explain the narrow bandwidth pulsed signals.

Silicon isotopic ratios measured in meteoritic presolar grains can provide useful information about the nucleosynthesis origin of these isotopes if the rates of nuclear reactions responsible for their production are known. One of the key reactions determining the Si isotopic abundances is 29Si(p,gamma)30P. Its reaction rate is not known with sufficient precision due in part to some ambiguous resonance strength values. In the present work, the strength of the E_p = 416.9 keV resonance has been measured with high precision using the activation technique. The new strength of omega_gamma = 219 +- 16 meV can be used in updated reaction rate estimations and astrophysical models.