Papers for Thursday, Feb 20 2025

Low-mass active galactic nuclei (AGNs) can provide important constraints on the formation and evolution of supermassive black holes (SMBHs), a central challenge in modern cosmology. To date only small samples of intermediate-mass black holes (IMBHs, $M_{BH}<10^5M_{\odot}$) and 'lesser' supermassive black holes (LSMBHs, $M_{BH}<10^6M_{\odot}$) have been identified. Our present study of NGC 3259 at D=27 Mpc with the Binospec integral field unit spectrograph complemented with Keck Echelle Spectrograph and Imager observations demonstrates the need for and the power of the spectroscopic follow-up. NGC 3259 hosts a black hole with a mass of $M_{BH}=(1.7-4.1)\times10^5M_{\odot}$, inferred from multi-epoch spectroscopic data, that accretes at 1% of the Eddington limit as suggested by the analysis of archival XMM-Newton observations. It is the second nearest low-mass AGN after the archetypal galaxy NGC 4395. The spectroscopic data reveals a variable broad $H\alpha$ profile that is likely the result of asymmetrically distributed broad-line region (BLR) clouds or BLR outflow events. X-ray observations and the absence of an optical power-law continuum suggest partial obscuration of the accretion disk and hot corona by a dust torus. We estimate that the Sloan Digital Sky Survey could only detect similar objects to D=35 Mpc. A detailed photometric analysis of NGC 3259 using HST images provides a central spheroid stellar mass estimate 25 times lower than expected from the $M_{BH}-M^*_{sph}$ relation, making this galaxy a strong outlier. This discrepancy suggests divergent growth pathways for the central black hole and spheroid, potentially influenced by the presence of a bar in the galaxy. Finally, we demonstrate that the DESI and 4MOST surveys will detect low-accretion rate IMBHs and LSMBHs and the sensitivity of future X-ray instruments (such as AXIS and Athena) will secure their classification.

The timing argument (TA) aims to find the total mass of the Local Group (LG) from the relative motions of the Milky Way (MW) and Andromeda Galaxy (M31). However, the classical TA always overestimates the LG mass, presumably because it does not account for the hierarchical scenario and other interactions such as that with the Large Magellanic Cloud (LMC). We focus on the impact of the recent major merger at M31 by using three merger models to find the peculiar motion of M31 within the simple two-body and point-mass scenario of TA. We found that the merger correction may affect the TA mass by either plus or minus 10-15% depending on the M31 tangential motion, which has very large uncertainties. If we consider a M31 merger configuration that reduces the TA mass by 10-15% to which we add the impact due to the LMC infall into the MW as reported in the literature, the TA mass would be found consistent with the LG mass from Hubble-Lemaitre flow. Galaxies are expected to experience about 16 major mergers each since z=11.5. Assuming all these mergers have similar impact on the TA mass as the most recent M31 merger, the ratio of LG mass to TA mass would be $0.85^{+0.65}_{-0.37}$ and such a TA mass is consistent with all the LG mass estimates. Our result also agrees with the findings using LG analogues in the cosmological simulations. We find that the TA mass estimate is limited by the hierarchical scenario, since it not possible to track the progenitors of both MW and M31 through so many mergers. We conclude that the MW-M31 dynamical system is far too complex to be modelled as a simple two-body point mass system.

Internal gravity waves (IGWs) have been shown to contribute to the transport of chemical elements in stars with a convective core and radiative envelope. Recent 2D hydrodynamical simulations of convection in intermediate-mass stars have provided estimates of the chemical mixing efficiency of such waves. The chemical diffusion coefficient from IGW mixing is described by a constant A times the squared wave velocity. The value of A, however, remains unconstrained by such simulations. This work aims at investigating what values A can take in order to reproduce the observed nitrogen surface abundances of the most nitrogen-enriched massive stars. Furthermore, we discuss the prevalence of IGW mixing compared to rotational mixing. We provide an implementation of these mixing profiles predicted from hydrodynamical simulations in the one-dimensional stellar evolution code MESA. We compute evolution tracks for stars between 3 and 30Msun with this new implementation for IGW mixing and study the evolution for the surface abundances of isotopes involved in the CNO cycle, particularly the N14 isotope. We show that this 1D framework predicting the chemical diffusion coefficient from IGW mixing yields consistent morphologies of the mixing profile in comparison with hydrodynamical simulations. We find that the value of A must increase with mass in order to reproduce the most nitrogen-enriched stars. Assuming these calibrated values for A, mixing by IGWs is a potential mechanism to reproduce well-mixed stars without needing rapid rotation. We have provided observational limits on the efficiency of IGW mixing for future theoretical studies. Future asteroseismic modelling efforts taking IGW mixing into account will be able to place additional constraints on the convective core mass, as our models predict that the convective core should be significantly more massive if IGW mixing is indeed efficient.

An open issue about multiple stellar populations in globular clusters (GCs) is the possible existence of metallicity spreads in first generation (FG) stars. Recent estimates based on HST pseudo-colours map (PCM) derived unlikely large spreads in [Fe/H] from spreads in the colour col=m_{F275W}-m_{F814W}. The inferred metallicity spreads for many GCs are comparable or even larger than those observed in dwarf galaxies. This result is clearly unexpected and at odds with the birth time of stars in dwarf galaxies, spanning several billion years, as opposed to very short formation times of the stellar component in GCs (a few million years). The contradiction is corroborated by the comparison of the widths of red giant branches in both classes of objects. Moreover, the so called spreads in FG stars estimated from the PCMs are always larger than the intrinsic metallicity spreads derived from spectroscopy. We used 30 pairs of FG stars with similar parameters in 12 GCs to highlight that a constant displacement in Delta col corresponds to variable differences in [Fe/H] up to 0.2 dex, depending on the GC. Providing for the first time quantitative measurements of the extension in Delta col of the sequences of FG and SG stars, we found no relation between metallicity spreads previously derived and extension of FG stars. We found that the length of the FG region correlates with the average global metallicity of GCs, and not with the observed metallicity spreads. The extension of FG stars also correlates with the extension of SG stars, and the global mass of the GCs. Our findings seriously challenge the scenario claiming more inhomogeneous mixing among FG stars, invalidating previous speculations in the literature.

Supermassive black holes at the centers of galaxies occasionally disrupt stars or consume stellar-mass black holes that wander too close, producing observable electromagnetic or gravitational wave signals. We examine how mass segregation impacts the rates and distributions of such events. Assuming a relaxed stellar cluster, composed of stars and stellar-mass black holes, we show that the tidal disruption rate of massive stars ($m\gtrsim M_\odot$) is enhanced relative to their abundance in the stellar population. For stars up to $m\approx3M_\odot$, this enhancement is roughly $m/M_\odot$ and it is driven by segregation within the sphere of influence. Stars with masses $m\gtrsim3M_\odot$, if relaxed, are predominantly scattered by more massive stellar-mass black holes, leading to a constant enhancement factor of $\approx 10$, independent of mass. This aligns with observational evidence suggesting an over-representation of massive stars in tidal disruption events. For stellar-mass black holes, we predict an enhancement factor scaling as $m_\bullet^{1/2}$ for plunges and $m_\bullet^{3/2}$ for extreme-mass-ratio inspirals (EMRIs). The power of one-half in both cases reflects the shorter relaxation times of heavier black holes, allowing them to segregate into the sphere of influence from greater distances, thereby increasing their abundance. The additional power in the EMRIs' rate arises from the tendency of heavier black holes to circularize and sink inward more efficiently. Finally, we estimate the rate of main sequence star inspirals and find that it favors low-mass stars ($m\lesssim M_\odot$). This seems compatible with the observationally estimated rate of quasi-periodic eruptions.

We present initial results from extremely well-resolved 3D magnetohydrodynamical simulations of idealized galaxy clusters, conducted using the AthenaPK code on the Frontier exascale supercomputer. These simulations explore the self-regulation of galaxy groups and cool-core clusters by cold gas-triggered active galactic nucleus (AGN) feedback incorporating magnetized kinetic jets. Our simulation campaign includes simulations of galaxy groups and clusters with a range of masses and intragroup and intracluster medium properties. In this paper we present results that focus on a Perseus-like cluster. We find that the simulated clusters are self-regulating, with the cluster cores staying at a roughly constant thermodynamic state and AGN jet power staying at physically reasonable values ($\simeq 10^{44}-10^{45}$~erg/s) for billions of years without a discernible duty cycle. These simulations also produce significant amounts of cold gas, with calculations having strong magnetic fields generally both promoting cold gas formation and allowing cold gas out to much larger clustercentric radii ($\simeq 100$~kpc) than simulations with weak or no fields ($\simeq 10$~kpc), and also having more filamentary cold gas morphology. We find that AGN feedback significantly increases the strength of magnetic fields at the center of the cluster. We also find that the magnetized turbulence generated by the AGN results in turbulence where the velocity power spectra are tied to AGN activity whereas the magnetic energy spectra are much less impacted after reaching a stationary state.

In the last decade of Active Galactic Nuclei (AGN) monitoring programs, the Metsähovi Radio Observatory detected multiple times seven powerful flaring narrow-line Seyfert 1 (NLS1) galaxies at 37 GHz. Several hypotheses have been proposed, but the understanding of this unique phenomenon is still far. To look at the case from a different point of view, we performed an emission line analysis of the optical spectra, with the aim of identifying similarities among the sources, that can be in turn possibly tied with the radio behavior. Our data were obtained with the Gran Telescopio Canarias. The results we obtained show that six out of seven sources have typical properties for the NLS1 class, and one of them is an intermediate Seyfert galaxy. We found on average black hole masses above the median value for the class (> 10$^7$ M$_\odot$), and a strong Fe II emission, which could be a proxy for an intense ongoing accretion activity. Although interesting, the characteristics we found are not unusual for these kind of AGN: the optical spectra of our sources do not related with their unique radio properties. Therefore, further multi-wavelength studies will be necessary to narrow the field of hypotheses for this peculiar phenomenon.

We search for parameters defined from photometric images to quantify the ex situ stellar mass fraction of galaxies. We created mock images using galaxies in the cosmological hydrodynamical simulations TNG100, EAGLE, and TNG50 at redshift $z=0$. We define a series of parameters describing their structures. In particular, the inner and outer halo of a galaxy are defined by sectors ranging from $45-135$ degrees from the disk major axis, and with radii ranging from $3.5-10$ kpc and $10-30$ kpc, respectively, to avoid the contamination of disk and bulge. The surface brightness and colour gradients are defined by the same sectors along the minor axis and with similar radii ranges. We used the Random Forest method to create a model that predicts $f_{\rm exsitu}$ from morphological parameters. The model predicts $f_{\rm exsitu}$ well with a scatter smaller than 0.1 compared to the ground truth in all mass ranges. The models trained from TNG100 and EAGLE work similarly well and are cross-validated; they also work well in making predictions for TNG50 galaxies. The analysis using Random Forest reveals that $\nabla \rho_{\rm outer}$, $\nabla (g-r)_{\rm outer}$, $f_{\rm outerhalo}$ and $f_{\rm innerhalo}$ are the most influential parameters in predicting $f_{\rm exsitu}$, underscoring their significance in uncovering the merging history of galaxies. We further analyse how the quality of images will affect the results by using SDSS-like and HSC-like mock images for galaxies at different distances. Our results can be used to infer the ex situ stellar mass fractions for a large sample of galaxies from photometric surveys.

We present the discovery of the variable optical counterpart to PSR J2055+1545, a redback millisecond pulsar, and the first radial velocity curve of its companion star. The multi-band optical light curves of this system show a $0.4$$-$$0.6 \ \mathrm{mag}$ amplitude modulation with a single peak per orbit and variable colours, suggesting that the companion is mildly irradiated by the pulsar wind. We find that the flux maximum is asymmetric and occurs at orbital phase $\simeq0.4$, anticipating the superior conjunction of the companion (where the optical emission of irradiated redback companions is typically brightest). We ascribe this asymmetry, well fit with a hot spot in our light curve modelling, to irradiation from the intrabinary shock between pulsar and companion winds. The optical spectra obtained with the \textit{Gran Telescopio Canarias} reveal a G-dwarf companion star with temperatures of $5749 \pm 34 \ \mathrm{K}$ and $6106 \pm 35 \ \mathrm{K}$ at its inferior and superior orbital conjunctions, respectively, and a radial velocity semi-amplitude of $385 \pm 3 \ \mathrm{km}\ \mathrm{s}^{-1}$. Our best-fit model yields a neutron star mass of $1.7^{+0.4}_{-0.1} \ \mathrm{M_{sun}}$ and a companion mass of $0.29^{+0.07}_{-0.01} \ \mathrm{M_{sun}}$. Based on the close similarity between the optical light curve of PSR~J2055$+$1545 and those observed from PSR J1023+0038 and PSR J1227-4853 during their rotation-powered states, we suggest this system may develop an accretion disc in the future and manifest as a transitional millisecond pulsar.

Context. (469219) Kamo`oalewa is a small near-Earth asteroid, which is currently a quasi-satellite of the Earth. Lightcurve measurements also reveal a rotation period of only about 30 minutes. This asteroid has been selected as the target of the Tianwen-2 sample-return mission of the China National Space Administration. Aims. The first goal of this paper is to observe and improve the orbit determination of (469219) Kamo`oalewa, and better determine the Yarkovsky effect acting on it. The second goal is to estimate the thermal inertia of the asteroid, taking advantage of an improved Yarkovsky effect determination. Methods. Our observational campaign imaged the asteroid from the Loiano Astronomical Station and from the Calar Alto Observatory, in March 2024. We also accurately re-measured a precovery detection from the Sloan Digital Sky Survey from 2004. New astrometry was later used in a 7-dimensional orbit determination, aimed at estimating both the orbital elements and the Yarkovsky effect. Thermal inertia is later studied by using the ASTERIA, a new method that is suitable to estimate thermal inertia of small asteroids. Results. We detected a semi-major axis drift of $(-67.35 \pm 4.70) \times 10^{-4}$ au My$^{-1}$ due to the Yarkovsky effect, with a high signal-to-noise ratio of 14. The new orbit solution also significantly reduced the position uncertainty for the arrival of the Tianwen-2 spacecraft. By using different models for the physical parameters of Kamo`oalewa, the ASTERIA model estimated the thermal inertia at $\Gamma = 150^{+90}_{-45}$ J m$^{-2}$ K$^{-1}$ s$^{-1/2}$ or $\Gamma = 181^{+95}_{-60}$ J m$^{-2}$ K$^{-1}$ s$^{-1/2}$.

We present an analysis of millimeter CO observations to search and quantify signatures of molecular gas outflows. We exploit the large sample of $0.5 < z < 2.6$ galaxies observed as part of the PHIBSS1/2 surveys with the IRAM Plateau de Bure interferometer, focusing on the 154 typical massive star-forming galaxies with CO detections (mainly CO(3-2), but including also CO(2-1) and CO(6-5)) at signal-to-noise (SNR) > 1.5 and available properties (stellar mass, star formation rate, size) from ancillary data. None of the individual spectra exhibit a compelling signature of CO outflow emission even at high SNR > 7. To search for fainter outflow signatures, we carry out an analysis of stacked spectra, including the full sample, as well as subsets, split in terms of stellar mass, redshift, inclination, offset in star formation rate (SFR) from the main sequence, and AGN activity. None of the physically motivated subsamples show any outflow signature. We report a tentative detection in a subset statistically designed to maximize outflow signatures. We derive upper limits on molecular gas outflow rate and mass loading factors $\eta$ based on our results and find $\eta \leq$ 2.2-35.4, depending on the subsample. Much deeper CO data and observations of alternative tracers are needed to decisively constrain the importance of cold molecular gas component of outflows relative to other gas phases.

As bound stellar systems orbit within a galaxy, stars may be tidally stripped to form streams of stars that nearly follow the orbit of their progenitor system. Stellar streams provide one of the most promising avenues for constraining the global mass distribution of the Milky Way and the nature of dark matter (DM). The stream stars' kinematic "track" enables inferring large-scale properties of the DM distribution, while density variations and anomalies provide information about local DM clumps (e.g., from DM subhalos). Using precise astrometric data from the Gaia Mission, which enables clean selections of Milky Way stream stars, we now know of a few streams with perturbations and density anomalies. A full accounting of the density tracks and substructures within all >100 Milky Way stellar streams will therefore enable powerful new constraints on DM. However, methods for discovering and characterizing membership of streams are heterogeneous and often highly customized to individual streams. Here we present a new, flexible framework for modeling stellar stream density and membership. Our framework allows us to include off-track or non-Gaussian components to the stream density, meaning we can capture anomalous features (such as the GD-1 steam's spur). We test our model on GD-1, where we characterize previously-known features and provide the largest catalog of probable member stars to date (1689 stars). Our framework (built on JAX and numpyro) provides a path toward uniform analysis of all Milky Way streams, enabling tight constraints on the Galactic mass distribution and its dark matter.

Accretion is the dominant contribution to the cosmic massive black hole density in the Universe today. Yet, modelling it in cosmological simulations is challenging due to the dynamic range involved, as well as the theoretical uncertainties of the underlying mechanisms driving accretion from galactic to black hole horizon scales. We present a simple, flexible parametrization for gas inflows onto massive black holes in order to manage this uncertainty in large-volume cosmological simulations. This is done as part of the "Learning the Universe'' collaboration, which aims to jointly infer the initial conditions and physical processes governing the evolution of the Universe using a Bayesian forward-modelling approach. To allow such a forward-modelling, we update the prescription for accretion with a two-parameter free-fall based inflow estimate that allows for a radius-dependent inflow rate and add a simple model for unresolved accretion disks. We use uniform resolution cosmological hydrodynamical simulations and the IllustrisTNG framework to study the massive black hole population and its dependence on the introduced model parameters. Once the parameters of the accretion formula are chosen to result in a roughly similar redshift zero black hole mass density, the differences caused by the details in the accretion formula are moderate in the supermassive black hole regime, indicating that it is difficult to distinguish between accretion mechanisms based on luminous active galactic nuclei powered by supermassive black holes. Applying the same models to intermediate mass black holes at high redshift, however, reveals significantly different accretion rates in high redshift, moderate luminosity active galactic nuclei and different frequencies and mass distributions of intermediate mass black hole mergers for the same black hole formation model.

Making the most of next-generation galaxy clustering surveys requires overcoming challenges in complex, non-linear modelling to access the significant amount of information at smaller cosmological scales. Field-level inference has provided a unique opportunity beyond summary statistics to use all of the information of the galaxy distribution. However, addressing current challenges often necessitates numerical modelling that incorporates non-differentiable components, hindering the use of efficient gradient-based inference methods. In this paper, we introduce Learning the Universe by Learning to Optimize (LULO), a gradient-free framework for reconstructing the 3D cosmic initial conditions. Our approach advances deep learning to train an optimization algorithm capable of fitting state-of-the-art non-differentiable simulators to data at the field level. Importantly, the neural optimizer solely acts as a search engine in an iterative scheme, always maintaining full physics simulations in the loop, ensuring scalability and reliability. We demonstrate the method by accurately reconstructing initial conditions from $M_{200\mathrm{c}}$ halos identified in a dark matter-only $N$-body simulation with a spherical overdensity algorithm. The derived dark matter and halo overdensity fields exhibit $\geq80\%$ cross-correlation with the ground truth into the non-linear regime $k \sim 1h$ Mpc$^{-1}$. Additional cosmological tests reveal accurate recovery of the power spectra, bispectra, halo mass function, and velocities. With this work, we demonstrate a promising path forward to non-linear field-level inference surpassing the requirement of a differentiable physics model.

There are a few different mechanisms that can cause white dwarf stars to vary in brightness, providing opportunities to probe the physics, structures, and formation of these compact stellar remnants. The observational characteristics of the three most common types of white dwarf variability are summarized: stellar pulsations, rotation, and ellipsoidal variations from tidal distortion in binary systems. Stellar pulsations are emphasized as the most complex type of variability, which also has the greatest potential to reveal the conditions of white dwarf interiors.

The interaction between planets and their host stars is governed by the forces of gravity, radiation, and magnetic fields. For planets orbiting their stars at distances of approximately 10 stellar radii or less, these effects are significantly intensified. Such interactions can be investigated through a combination of photometric, spectroscopic, and spectropolarimetric studies spanning wavelengths from X-rays to radio frequencies. When a hot planet resides within the star's sub-Alfvénic radius, magnetic star-planet interactions (SPI) become possible, often observable as stellar activity enhancements influenced by the planet's orbital motion rather than stellar rotation alone. Such interactions offer a unique perspective on the atmospheric erosion and magnetospheric characteristics of close-in this http URL behavior and impacts of these magnetic interactions are highly sensitive to the magnetic fields of both the planet and its host star. This interplay can influence the magnetic activity of both bodies and has implications for the planet's irradiation levels, orbital migration, and the star's rotational dynamics. By employing phase-resolved observational methods on an expanding sample of hot Jupiter (HJ) systems, researchers can now extend these studies to other compact star-planet systems, including smaller planets in the habitable zones of M dwarfs. Efforts to comprehend magnetic SPI have led to extensive advancements in theoretical research and computational modeling. These efforts include investigations into the space weather environments of close-in giant exoplanets. Utilizing hydrodynamical (HD) and magnetohydrodynamical (MHD) simulations, researchers aim to provide both qualitative and quantitative descriptions of SPI. In this chapter, we first review notable SPI detections before summarizing the current understanding of the underlying physical mechanisms driving SPI.

We examine the decay of perturbations in an infinite homogeneous self-gravitating model with a Maxwellian distribution function (DF) when weak collisions are present. In collisionless systems within the stable parameter range, the eigenvalue spectrum consists of a continuous set of real frequencies associated with van Kampen modes, which are singular eigenfunctions of the stellar DF. An initial perturbation in the stellar density and gravitational potential decays exponentially through a superposition of these modes, a phenomenon known as Landau damping. However, the perturbation in the stellar DF does not decay self-similarly; it becomes increasingly oscillatory in velocity space over time, indicating the absence of eigenfunctions corresponding to the Landau damping eigenfrequencies. Consequently, we refer to perturbations undergoing Landau damping as quasi-modes rather than true eigenmodes. Even rare collisions suppress the formation of steep DF gradients in velocity space. Ng & Bhattacharjee (2021) demonstrated that introducing collisions eliminates van Kampen modes and transforms Landau quasi-modes into true eigenmodes forming a complete set. As the collision frequency approaches zero, their eigenfrequencies converge to those of the collisionless Landau quasi-modes. In this study, we investigate the behavior of the eigenfunction of the least-damped aperiodic mode as the collision frequency approaches zero. We derive analytic expressions for the eigenfunction in the resonance region and for the damping rate as a function of collision frequency. Additionally, we employ the standard matrix eigenvalue problem approach to numerically verify our analytical results.

Statistical studies of the circumgalactic medium (CGM) using Sunyaev-Zeldovich (SZ) observations offer a promising method of studying the gas properties of galaxies and the astrophysics that govern their evolution. Forward modeling profiles from theory and simulations allows them to be refined directly off of data, but there are currently significant differences between the thermal SZ (tSZ) observations of the CGM and the predicted tSZ signal. While these discrepancies could be inherent, they could also be the result of decisions in the forward modeling used to build statistical measures off of theory. In order to see effects of this, we compare an analysis utilizing halo occupancy distributions (HODs) implemented in halo models to simulate the galaxy distribution against a previous studies which weighted their results off of the CMASS galaxy sample, which contains nearly one million galaxies, mainly centrals of group sized halos, selected for relatively uniform stellar mass across redshifts between $0.4<z<0.7$. We review some of the implementation differences that can account for changes, such as miscentering, one-halo/two-halo cutoff radii, and mass ranges, all of which will need to be given the proper attention in future high-signal-to-noise studies. We find that our more thorough model predicts a signal $\sim 25\%$ stronger than the one from previous studies on the exact same sample, resulting in a $33\%$ improved fit for non-dust-contaminated angular scales. Additionally, we find that modifications that change the satellite fraction even by just a few percents, such as editing the halo mass range and certain HOD parameters, result in strong changes in the final signal. Although significant, this discrepancy from the modeling choices is not large enough to completely account for the existing disagreements between simulations and measurements.

The possibility that dark matter could be primordial black holes is discussed with an emphasis on the most commonly studied inflationary dynamics that could have produced them.

Accurate visualization of double star astrometric data is essential for effective analysis and interpretation. This article presents a Python toolkit designed for astronomers who need to plot measurements from diverse sources -- historical, Gaia DR3, and the Las Cumbres Observatory (LCO) network -- while maintaining a 1:1 aspect ratio to avoid visually distorting the data. The toolkit is composed of three scripts: one that handles polar coordinates (P.A., separation), one for Cartesian (X, Y) coordinates, and another with the option to include predicted theoretical points. This paper describes the purpose, functionality, and usage of these scripts, including example figures, installation guides, and licensing information. This toolkit has been used by the author and collaborators in published and submitted research on double star systems, demonstrating its versatility for both professional and student-driven investigations.

For the first time, we have determined the spatial distribution of magnetic waveguides and resonant cavities at different heights in the sunspot atmosphere. We applied a decomposition of time cubes of EUV/UV sunspot images obtained in the SDO/AIA temperature channels into narrowband components in the form of wave sources. The methods of pixelized wavelet filtering and oscillation mode decomposition were used. For all studied sunspots the presence of selected bands in the spectra was shown. Each band corresponds to oscillations forming spatial waveguides in the volume of the sunspot atmosphere. The formation of waveguide bundles in the height from photospheric to coronal levels is shown. The regions of the waveguides with maximum oscillation power, where resonant cavities are formed, are identified. Their detection is an experimental proof of the theory of resonant layers, previously proposed to explain the presence of significant harmonics in the oscillation spectrum. The different shapes of the cavities reflect the structure of the magnetic tubes along which the waves propagate. The distribution of sources in the height layers indicates the influence of the wave cutoff frequency caused by the inclinations of the magnetic field lines. We discuss the possibility of upward wave transport due to periodic amplification of the oscillation power in the detected cavities.

Venus' atmosphere -- specifically its clouds buoyed up 40 to 60 km above the surface -- has long been suspected to encompass a biosphere where Earth-like living organisms could grow and flourish. This idea has been recently rekindled by the observation (signal-to-noise ratio of about 15$\sigma$) of a phosphine (PH$_3$) absorption-line profile against the thermal background from deeper, hotter layers of the atmosphere. There is a chance that this observation could be a sign of life, because the PH$_3$ gas observed on Earth originates mostly in decaying organic material. Furthermore, it has been shown that there is no other natural process on Venus that could otherwise produce the observed PH$_3$ absorption line. On the other hand, cosmic rays and the particle cascades they produce in the Earth's atmosphere are hazardous to living organisms, because the ionizing radiation produced in air showers can blow apart chemical molecules and disrupt biochemical processes, causing cells to die or undergo dangerous mutations. Compared to Earth, the hypothesized biosphere of Venus could be exposed to substantially more ionizing radiation. This is because Venus has no protective intrinsic magnetic field, orbits closer to the Sun, and the entire eventual habitable region lies in the clouds high in the atmosphere. Thereby, if the clouds were sterilized there would be no reservoir of deeper life that can recolonize afterwards. In this communication we study the effects of particle cascades in the venusian atmosphere using the AIRES simulation package properly configured. We show that the effects of cosmic radiation in the habitable zone would be comparable to those on the Earth's surface and so would not have any hazardous effect on possible venusian microorganisms.

We present the discovery of the radio afterglow of the most distant ultra-long gamma-ray burst (GRB) detected to date, GRB~220627A at redshift $z=3.084$. Its prompt gamma-ray light curve shows a double-pulse profile, with the pulses separated by a period of quiescence lasting ${\sim} 15\,$min, leading to early speculation it could be a strongly gravitationally lensed GRB. However, our analysis of the $\textit{Fermi}$/GBM spectra taken during the time intervals of both pulses show clear differences in their spectral energy distributions, disfavouring the lensing scenario. We observed the radio afterglow from $7$ to $456\,$d post-burst: an initial, steep decay ($F_{\nu} \propto t^{-2}$) is followed by a shallower decline ($F_{\nu} \propto t^{-1/2}$) after ${\sim} 20\,$d. Our afterglow modelling shows that these radio properties can be explained by the presence of a slow, wide ejecta component in addition to a fast, narrow ejecta component, consistent with the picture of a highly-collimated jet and its thermal cocoon decelerating into the ambient medium. The properties of the cocoon point toward a progenitor with a large stellar radius, supporting the blue supergiant scenario proposed for ultra-long GRBs. We also conducted an independent test of the lensing hypothesis via Very Long Baseline Interferometry (VLBI) observations at ${\sim} 12\,$d post-burst by searching, for the first time, for multiple images of the candidate lensed GRB afterglow. Our experiment highlighted the growing need for developments in real-time correlation capabilities for time-critical VLBI experiments, particularly as we advance towards the SKA and ngVLA era of radio astronomy.

Neutrino flavor evolution inside a core-collapse supernova is a topic of active research. The core of a supernova is an intense source of neutrinos and antineutrinos. Self-interaction among neutrinos (as well as antineutrinos) gives rise to a rich phenomenology not seen in terrestrial situations. In studies of the dynamics of flavor evolution in such environments, the gravitational effects are generally ignored. Although the curvature outside a dense core does not deviate much from a flat space, the spin of the neutrinos can still couple to the torsion of the spacetime. These extra degrees of freedom of curved spacetime have interaction strengths that are proportional to the density of the neutrinos and the other fermions \cite{Chakrabarty:2019cau} \cite{Barick:2023qjq} as well as the coupling constants of the spin-torsion interaction. We have studied the effects of such interactions in flavor evolution inside a core-collapse supernova \cite{Ghose:Manuscript}. The self-interaction gets modified by the spin-torsion interaction and the oscillation dynamics is modified. We have seen that there are noticeable changes in the flavor dynamics when the neutrino density is uniform. We have also studied the effects of such interaction in a realistic core-collapse supernova (CCSN). As neutrino astronomy enters the precision era, this study will shed light on the potential of neutrino fluxes from CCSN to probe the neutrino-neutrino interaction.

Potentially Hazardous Asteroids (PHAs), a special subset of Near-Earth Objects, are both dangerous and scientifically valuable. PHAs that truly undergo close approaches with the Earth (dubbed CAPHAs) are of particular interest and extensively studied. The concept and study of CAPHA can be extended to other Solar system planets, which have significant implications for future planet-based observations and explorations. In this work, we conduct numerical simulations that incorporate the Yarkovsky effect to study the transformation of main belt asteroids into CAPHAs of terrestrial planets, using precise nominal timesteps, especially to ensure the reliability of the results for Mercury and Venus. Our simulations predict a total of 1893 Mercury-CAPHAs, 3014 Venus-CAPHAs, 3791 Earth-CAPHAs and 18066 Mars-CAPHAs, with an occurrence frequency of about 1, 9, 15 and 66 per year, respectively. The values for Mars-CAPHAs are consistent with our previous work, which were based on simulations with a larger nominal timestep. The predicted occurrence frequency and velocity distribution of Earth-CAPHAs are in reasonable agreement with the observed population of Earth-CAPHAs. We also find that certain asteroids can be caught in close approach with different planets at different times, raising an interesting possibility of using them as transportation between terrestrial planets in the future.

T-type brown dwarfs present an opportunity to explore atmospheres teeming with molecules such as H2O, CH4 and NH3, which exhibit a wealth of absorption features in the mid-infrared. With JWST, we can finally explore this chemistry in detail, including for the coldest brown dwarfs that were not yet discovered in the Spitzer era. This allows precise derivations of the molecular abundances, which in turn informs our understanding of vertical transport in these atmospheres and can provide clues about the formation of cold brown dwarfs and exoplanets. This study presents the first JWST/MRS mid-IR spectrum (R ~ 1500-3000) of a T-dwarf: the T8.5+T9 brown dwarf binary WISE J045853.90+643451.9. We fit the spectrum using a parameterized P-T profile and free molecular abundances (i.e., a retrieval analysis), treating the binary as unresolved. We find a good fit with a cloud-free atmosphere and identify H2O, CH4 and NH3 features. Moreover, we make the first detections of HCN and C2H2 (at 13.4$\sigma$ and 9.5$\sigma$ respectively) in any brown dwarf atmosphere. The detection of HCN suggests intense vertical mixing ($K_{zz}\sim10^{11}$cm$^2$s$^{-1}$), challenging previous literature derivations of $K_{zz}$ values for T-type brown dwarfs. Even more surprising is the C2H2 detection, which cannot be explained with existing atmospheric models for isolated objects. This result challenges model assumptions about vertical mixing, and/or our understanding of the C2H2 chemical network, or might hint towards a more complex atmospheric processes such as magnetic fields driving aurorae, or lightning driving ionization. These findings open a new frontier in studying carbon chemistry within brown dwarf atmospheres.

Red supergiants (RSGs) represent a late evolutionary stage of massive stars. Recent observations reveal that the observed luminosity range of RSGs in young open clusters is wider than expected from single star evolution models. Binary evolution effects have been suggested as a possible explanation. Here, we analyse 3670 detailed binary-evolution models, as well as corresponding single-star models, to probe the contribution of binary mass transfer and binary mergers on the luminosity distribution of RSGs in star clusters with ages up to 100 Myr. We confirm that the expected luminosity range of RSGs in a coeval population can span a factor of ten, as a consequence of mergers between two main-sequence stars, which reproduces the observed red supergiant luminosity ranges in rich clusters well. While the luminosity increase as consequence of mass transfer is more limited, it may help to increase the number of overluminous RSGs. However, our results also demonstrate that binary effects alone are insufficient to account for the number of RSGs found with luminosities of up to three times those predicted by current single-star models. We discuss observational accuracy, rotational mixing, age spread, and intrinsic RSG variability as possible explanations. Further observations of RSGs in young open clusters, in particular studies of their intrinsic brightness variability, appear crucial for disentangling these effects.

The spontaneous breaking of a discrete symmetry can lead to the formation of domain walls in the early Universe. In this work, we explore the impact of bias directions on the dynamics of $Z_N$ domain walls, mainly focusing on the $N = 3$ model with a biased potential. Utilizing the Press-Ryden-Spergel method, we numerically investigate the dynamics of domain walls with lattice simulations. We find notable differences in the dynamics of domain walls due to bias directions. Our results indicate that the annihilation time depends not only on the vacuum energy difference $\delta V$ but also on bias directions described by the relative potential difference $ \zeta $.

Purpose: RR Lyrae stars are important distance indicators. They are usually present in globular clusters where they were first discovered. The study of their properties and distribution in our Galaxy and external galaxies constitutes a modern field of astrophysical research. The aim of this paper is checking the possibility that the observed distribution of RR Lyrae stars in the Galactic bulge derives from orbitally decayed globular clusters (GCs). Methods: To reach the aim of the paper I made use of the comparison of observational data of RR Lyrae in the Galactic bulge with the distribution of GCs in the Milky Way (MW) as coming from theoretical models under a set of assumptions. Results: I obtain the expected numbers and distributions of RR Lyrae in the Galactic bulge as coming from an initial population of globular clusters at varying some characteristic parameters of the GC population and compare to observational data. Conclusion: The abundance of RR Lyrae distribution in the Galactic bulge and their radial distribution is likely still too uncertain to provide a straight comparison with theoretical models. Despite this, it can be stated that a significant fraction of the `foreground' RR Lyrae present in the MW originate from orbitally evolved and dissolved GCs.

The large abundance of electrically neutral particles has a remarkable impact on the dynamics of many astrophysical plasmas. Here, we use a two-fluid model that includes charge-neutral elastic collisions and Hall's current to study the propagation of magnetohydrodynamic (MHD) waves in weakly ionized plasmas. we derive the dispersion relation for small-amplitude incompressible transverse waves propagating along the background magnetic field. Then, we focus on the polarization relations fulfilled by the eigenmodes and their corresponding ratios of magnetic to kinetic energies, and we study their dependence on the relations between the oscillation, collision and cyclotron frequencies. For low wave frequencies, the two components of the plasma are strongly coupled, the damping due to the charge-neutral interaction is weak and the effect of Hall's term is negligible. However, as the wave frequency increases, phase shifts between the velocity of charges, the velocity of neutrals, and the magnetic field appear, leading to enhanced damping. The effect of collisions on the propagation of waves strongly depends on their polarization state, with the left-handed circularly polarized ion-cyclotron modes being more efficiently damped than the linearly polarized Alfvén waves and the right-handed circularly polarized whistler modes. Moreover, the equipartition relation between the magnetic energy and the kinetic energy of Alfvén waves does not hold in general when the collisional interaction and Hall's current are taken into account, with the magnetic energy usually dominating over the kinetic energy. This theoretical result extends previous findings from observational and numerical works about turbulence in astrophysical scenarios.

In the last few years, NICER data has enabled mass and radius inferences for various pulsars, and thus shed light on the equation of state for dense nuclear matter. This is achieved through a technique called pulse profile modeling. The importance of the results necessitates careful validation and testing of the robustness of the inference procedure. In this paper, we investigate the effect of sampler choice for X-PSI (X-ray Pulse Simulation and Inference), an open-source package for pulse profile modeling and Bayesian statistical inference that has been used extensively for analysis of NICER data. We focus on the specific case of the high-mass pulsar PSR J0740+6620. Using synthetic data that mimics the most recently analyzed NICER and XMM-Newton data sets of PSR J0740+6620, we evaluate the parameter recovery performance, convergence, and computational cost for MultiNest's multimodal nested sampling algorithm and UltraNest's slice nested sampling algorithm. We find that both samplers perform reliably, producing accurate and unbiased parameter estimation results when analyzing simulated data. We also investigate the consequences for inference using the real data for PSR J0740+6620, finding that both samplers produce consistent credible intervals.

We present a full-spectrum linear fitting method, SEW, for stellar population synthesis based on equivalent widths (EWs) to extract galaxy properties from observed spectra. This approach eliminates the need for prior assumptions about dust attenuation curves, which are instead derived as outputs of the fitting process. By leveraging the invariance of EWs and employing the Discrete Penalised Least Squares (DPLS) method to extract EWs, we address the nonlinear aspects of the fitting process by linearising the matrix equations. This enables accurate recovery of key parameters, stellar age, metallicity and dust attenuation, even under systematic calibration biases and varying attenuation conditions. Rigorous testing with mock spectra across signal-to-noise ratios (S/N = 5-30) and calibration biases demonstrates the robustness of method. The derived attenuation curves align closely with input models, and stellar population parameters are recovered with minimal bias. To facilitate adoption, we implement this method as a Python extension package for \texttt{pPXF} (\texttt{pPXF-SEW}). Our work addresses critical degeneracies in traditional spectral fitting and enhances the reliability of extragalactic studies.

Context. Pre-stellar cores are the birthplaces of Sun-like stars and represent the initial conditions for the assembly of protoplanetary systems. Due to their short lifespans, they are rare. In recent efforts to increase the number of such sources identified in the Solar neighbourhood, we have selected a sample of 40 starless cores from the publicly available core catalogs of the Herschel Gould Belt survey. In this work, we focus on one of the sources that stands out for its high central density: Corona Australis 151. Aims. We use molecular lines that trace dense gas (n>=10^6 cm-3) to confirm the exceptionally high density of this object, to study its physical structure, and to understand its evolutionary stage. Methods. We detected the N2H+ 3-2 and 5-4 transitions, and the N2D+ 3-2, 4-3, and 6-5 lines with the APEX telescope. We use the Herschel continuum data to infer a spherically symmetric model of the core's density and temperature. This is used as input to perform non-local-thermodynamic-equilibrium radiative transfer to fit the observed five lines. Results. Our analysis confirms that this core is characterised by very high densities (a few x 10^7 cm-3 at the centre) and cold temperatures. We infer a high deuteration level of N2D+/N2H+=0.50, indicative of an advanced evolutionary stage. In the large bandwidth covered by the APEX data, we detect several other deuterated species, including CHD2OH, D2CO, and ND3. We also detect multiple sulphurated species that present broader lines with signs of high-velocity wings. Conclusions. The observation of high-velocity wings and the fact that the linewidths of N2H+ and N2D+ become larger with increasing frequency can be interpreted either as an indication of supersonic infall motions developing in the central parts of a very evolved pre-stellar core or as the signature of outflows from a very low luminosity object (VeLLO). *SHORTENED*

Supermassive black holes (SMBHs) are found at the centre of every massive galaxy, with their masses tightly connected to their host galaxies through a co-evolution over cosmic time. For massive ellipticals, the SMBH mass ($M_\text{BH}$) strongly correlates with the central stellar velocity dispersion ($\sigma_e$), via the $M_\text{BH}-\sigma_e$ relation. However, SMBH mass measurements have traditionally relied on central stellar dynamics in nearby galaxies ($z < 0.1$), limiting our ability to explore the SMBHs across cosmic time. In this work, we present a self-consistent analysis combining 2D stellar dynamics and lens modelling of the Cosmic Horseshoe gravitational lens system ($z = 0.44$), one of the most massive galaxies ever observed. Using integral-field spectroscopic data from MUSE and high-resolution imaging from HST, we model the radial arc and stellar kinematics, constraining the galaxy's central mass distribution and SMBH mass. Bayesian model comparison yields a $5\sigma$ detection of an ultramassive black hole (UMBH) with $\log_{10}(M_\text{BH}/M_{\odot}) = 10.56^{+0.07}_{-0.08} \pm (0.12)^\text{sys}$, consistent across various systematic tests. Our findings place the Cosmic Horseshoe $\sim$$1.5\sigma$ above the $M_\text{BH}-\sigma_e$ relation, supporting an emerging trend observed in BGCs and other massive galaxies. This suggests a steeper $M_\text{BH}-\sigma_e$ relationship at the highest masses, potentially driven by a different co-evolution of SMBHs and their host galaxies. Future surveys will uncover more radial arcs, enabling the detection of SMBHs over a broader redshift and mass range. These discoveries will further refine our understanding of the $M_\text{BH}-\sigma_e$ relation and its evolution across cosmic time.

The direction of extensive air showers can be used to determine the source of gamma quanta and plays an important role in estimating the energy of the primary particle. The data from an array of non-imaging Cherenkov detector stations HiSCORE in the TAIGA experiment registering the number of photoelectrons and detection time can be used to estimate the shower direction with high accuracy. In this work, we use artificial neural networks trained on Monte Carlo-simulated TAIGA HiSCORE data for gamma quanta to obtain shower direction estimates. The neural networks are multilayer perceptrons with skip connections using partial data from several HiSCORE stations as inputs; composite estimates are derived from multiple individual estimates by the neural networks. We apply a two-stage algorithm in which the direction estimates obtained in the first stage are used to transform the input data and refine the estimates. The mean error of the final estimates is less than 0.25 degrees. The approach will be used for multimodal analysis of the data from several types of detectors used in the TAIGA experiment.

Some sub-Neptune planets may host habitable conditions; for example "Hycean" worlds with H2 envelopes over liquid water oceans can maintain potentially hospitable pressures and temperatures at their surface. Recent JWST observations of K2-18b and TOI-270d have shown that such worlds could be compelling targets for biosignature searches, given their extended scale heights and therefore large atmospheric signatures. Methylated biosignatures, a broad group of gases that can be generated by biological attachment of a CH3 group to an environmental substrate, have been proposed as candidate signs of life for Earth-like exoplanets. However, methyl halides (CH3 + halogen) have not yet been robustly examined with self-consistent photochemical and spectral models for planets with H2-dominated atmospheres. Here we demonstrate that methyl chloride (CH3Cl), predominantly produced by marine microbes, could be detected using JWST in tens of transits or fewer for Hycean planets, comparable to detection requirements for other potential atmospheric biosignatures. The threshold atmospheric mixing ratio for detectability is $\sim$10 ppm, which can accumulate with global fluxes comparable to moderately productive local environments on Earth.

Ultra-faint dwarf galaxies, which can be detected as resolved satellite systems of the Milky Way, are critical to understanding galaxy formation, evolution, and the nature of dark matter, as they are the oldest, smallest, most metal-poor, and most dark matter-dominated stellar systems known. Quantifying the sensitivity of surveys is essential for understanding their capability and limitations in searching for ultra-faint satellites. In this paper, we present the first study of the image-level observational selection function for Kilo-Degree Survey (KiDS) based on the Synthetic UniveRses For Surveys (surfs)-based KiDS-Legacy-Like Simulations. We generate mock satellites and simulate images that include resolved stellar populations of the mock satellites and the background galaxies, capturing realistic observational effects such as source blending, photometric uncertainties, and star-galaxy separation. The matched-filter method is applied to recover the injected satellites. We derive the observational selection function of the survey in terms of the luminosity, half-light radius, and heliocentric distance of the satellites. Compared to a catalogue-level simulation as used in previous studies, the image-level simulation provides a more realistic assessment of survey sensitivity, accounting for observational limitations that are neglected in catalogue-level simulations. The image-level simulation shows a detection loss for compact sources with a distance $d \gtrsim 100~\rm kpc$. We argue that this is because compact sources are more likely to be identified as single sources rather than being resolved during the source extraction process.

Aims: We characterize and quantify this multi-scale flow for a prototypical high-mass star-forming region. Methods: In a multi-scale analysis from parsec to ~50au scales, we combined multiple single-dish and interferometric observations to study the gas flow from large-scale sizes of several parsec (Mopra) via intermediate-scale filamentary gas flows (ALMA-IMF) to the central cores (ALMA DIHCA and configuration 10 data). The highest-resolution multi-configuration ALMA dataset achieved a spatial resolution of 0.027''x0.022'' or 50au. Results: This multi-scale study allows us to follow the gas from the environment of the high-mass star-forming region (~2pc) via intermediate-scale (~0.25pc) filamentary gas flows down to the innermost cores within the central few 1000au. The intermediate-scale filaments connect spatially and kinematically to the larger-scale cloud as well as the innermost cores. We estimate a filamentary mass inflow rate around 10^-3M_sun/yr, feeding into the central region that hosts at least a dozen mm cores. While the flow from the cloud via the filaments down to 10^4au appears relatively ordered, within the central 10^4au the kinematic structures become much more complicated and disordered. We speculate that this is caused by the interplay of the converging infalling gas with feedback processes from the forming central protostars. Conclusions: This multi-scale study characterises and quantifies the hierarchical gas flow from clouds down to the central protostars for a prototypical infrared dark cloud with several embedded cores at an unprecedented detail. While comparatively ordered gas flows are found over a broad range of scales, the innermost area exhibits more disordered structures, likely caused by the combination of inflow, outflow and cluster dynamical processes.

We measure radial stellar age gradients in the relatively isolated gas-rich dwarf irregular WLM, combining JWST NIRCam and NIRISS imaging with six archival Hubble fields over semi-major axis equivalent distances of 0$\lesssim$R$_{SMA}$$\lesssim$4 kpc ($\lesssim$3R$_{hl}$). Fitting lifetime star formation histories (SFHs) to resolved color-magnitude diagrams (CMDs), radial age gradients are quantified using $\tau_{90}$ and $\tau_{50}$, the lookback times to form 90\% and 50\% of the cumulative stellar mass. We find that globally, the outskirts of WLM are older on average, with ($\delta$$\tau_{90}$, $\delta$$\tau_{50}$)/$\delta$R$_{SMA}=$(0.82$^{+0.10}_{-0.10}$, 1.60$^{+0.23}_{-0.22}$) Gyr/kpc (stat.), in good agreement with simulations. However, we also detect an azimuthal dependence of radial stellar age gradients, finding that stars on the leading edge of WLM (relative to its proper motion) are both younger and have a flatter age gradient compared to the trailing edge. This difference persists over 0.6$\lesssim$R$_{SMA}$$\lesssim$3.2 kpc ($\sim$0.5$-$2.5R$_{hl}$) and lookback times up to $\sim$8 Gyr, and is robust to assumed stellar evolutionary model. Our results are consistent with star formation triggered by ram pressure stripping from a circumgalactic and/or intergalactic medium, suggested by recent HI observations. If confirmed, processes typifying dense environments, such as ram pressure stripping, may be more relevant to the evolution of isolated galaxies than previously thought.

Spectropolarimetric inversions of solar observations are fundamental for the estimation of the magnetic field in the solar atmosphere. However, instrumental noise, computational requirements, and varying levels of physical realism make it challenging to derive reliable solar magnetic field estimates. In this study, we present a novel approach for spectropolarimetric inversions based on Physics Informed Neural Networks (PINNs) to infer the photospheric magnetic field under the Milne-Eddington approximation (PINN ME). Our model acts as a representation of the parameter space, mapping input coordinates (t, x, y) to the respective spectropolarimetric parameters, which are used to synthesize the corresponding stokes profiles. By iteratively sampling coordinate points, synthesizing profiles, and minimizing the deviation from the observed stokes profiles, our method can find the set of Milne-Eddington parameters that best fit the observations. In addition, we directly include the point-spread-function to account for instrumental effects. We use a predefined parameter space as well as synthetic profiles from a radiative MHD simulation to evaluate the performance of our method and to estimate the impact of instrumental noise. Our results demonstrate that PINN ME achieves an intrinsic spatio-temporal coupling, which can largely mitigate observational noise and provides a memory-efficient inversion even for extended fields-of-view. Finally, we apply our method to observations and show that our method provides a high spatial coherence and can resolve small-scale features both in strong- and weak-field regions.

Most of the space projects or large observatories do have official tools like simulators, end-to-end pipelines developed during years by a large team of contributors. They are like {\em cathedrals}. In this paper, we show that very simplistic code using basic operators provided by high level language like GDL allows to write quickly high quality code to process raw data into scientifically validated outputs. This is {\em bazaar}. In this paper we argument why we consider large infrastructure should be designed to allow small ones to benefit from it and allow to graft better alternative processing at very low cost.

We present a multi-wavelength analysis of three candidate active galactic nuclei (AGNs) in low-mass galaxies in the Boötes field with the aim of improving constraints on the occupation fraction of low-mass black holes (BHs). Galaxies with low stellar masses ($M_{\star} < 10^{9.5} M_{\odot}$) are particularly interesting hosts for AGNs as they may contain BHs that have not grown significantly since the epoch of their formation in the early Universe. Using archival data from the Chandra X-ray Observatory, we find three X-ray luminous low-mass galaxies and assess whether they host AGNs. We find one of these sources to be variable in the X-ray and compute its X-ray light curve and spectrum. We compute the X-ray, mid-infrared, and [O III] luminosities and compare them to established AGN luminosity relationships in the literature. We then fit various star-forming, dust emission, and AGN templates to the spectral energy distributions (SEDs). The star formation rates estimated from the SED fits are unable to explain the observed X-ray luminosities of the candidates, providing more support for the presence of AGNs. By analysing the deviation from linear relationships between X-ray and mid-infrared luminosities, we find these systems to be obscured (with $\log N_{\rm H}[{\rm {cm^{-2}}}] \sim 22.7, > 25.0$, and $24.4$, respectively). We employ the scaling relationship between BH mass and stellar velocity dispersion to estimate the BH masses as $\sim 10^5 - 10^6 M_{\odot}$ and accreting at Eddington ratios $10^{-2} < \lambda_{\rm Edd} <10^{-1}$.

Dipole mode suppression is an observed behavior of solar-like oscillations in evolved stars. This study aims to search for depressed dipole modes in giant stars using data from the Transiting Exoplanet Survey Satellite (TESS) and investigate when the suppression starts to emerge. We study a sample of 8,651 TESS-evolved stars and find 179 stars with significant dipole mode depression by comparing the oscillation amplitudes of radial and dipole modes. Notably, 11 of them are located near the base of the red-giant branch, indicating that mode suppression appears earlier than the point inferred in previous studies with the Kepler data. These findings provide new evidence for the dipole mode suppression in giant stars, particularly in subgiants.

Microcalorimeter instruments aboard future X-ray observatories will require an anti-coincidence (anti-co) detector to veto charged particle events and reduce the non-X-ray background. We have developed a large-format, TES-based prototype anti-coincidence detector that is particularly suitable for use with spatially-extended (~ 10 cm^2}) TES microcalorimeter arrays, as would be used for a future large field-of-view X-ray missions. This prototype was developed in the context of the Line Emission Mapper (LEM) probe concept, which required a ~ 14 cm^2 anti-co detector with > 95% live time and a low-energy threshold below 20 keV. Our anti-co design employs parallel networks of quasiparticle-trap-assisted electrothermal feedback TESs (QETs) to detect the athermal phonon signal produced in the detector substrate by incident charged particles. We developed multiple prototype anti-co designs featuring 12 channels and up to 6300 QETs. Here we focus on a design utilizing tungsten TESs and present characterization results. Broad energy range measurements have been performed (4.1 keV -- 5.5 MeV). Based on noise and responsivity measurements, the implied low-energy threshold is < 1 keV and a live time fraction of > 96% can be achieved up to 5.5 MeV. We also find evidence of mm-scale-or-better spatial resolution and discuss the potential utility of this for future missions. Finally, we discuss the early development of a soild-state physics model of the anti-co towards understanding phonon propagation and quasiparticle production in the detector.

We present universal formulas for particle production from gravitational inhomogeneities. In the massless limit the result is strikingly simple and completely determined by the two-point function of the energy-momentum tensor that is fixed up to a constant - the central charge - for conformally coupled scalars, massless fermions and gauge fields. This result can be applied to any conformally coupled theory, weakly or strongly interacting, unifying previous derivations for fields of different spin and for scalar and tensor perturbations. We derive the results using the Schwinger method of 1PI effective action and through Bogoliubov transformations that allows to compute exclusive information on the distribution of particles. We then apply these results to stochastic backgrounds of scalar and tensor perturbations that can be generated by various phenomena such us inflationary perturbations and first order phase transitions. Differently from particle production usually considered in cosmology this mechanism allows for the production of massless fields. In particular the abundance induced by inhomogeneities can easily reproduce the dark matter abundance if scalar perturbations produced from inflation are enhanced at short scales.

Generalizing the result of H. Ellis who embedded a warp bubble in the background of a black hole, we introduce a warp bubble in a de Sitter universe. We show that under certain conditions (namely, that the bubble is moving in the radial direction at a velocity equal to the speed of the expansion of the universe), it is possible for the bubble to have strictly non--negative Eulerian energy density and satisfy the averaged weak and null energy conditions (though they are violated locally). We also prove a more generic theorem that if perturbations of vacuum energy produce at least some underdense regions in all reference frames, they always result in local violations of NEC and WEC. We discuss the implications of these results and their possible applications to models of dark energy like "dark fluid" and quintessence, as well as to physical systems like Casimir cavities and analog gravity setups.

During inflation an axion field coupled to a gauge field through a Chern-Simons term can trigger the production of gauge quanta due to a tachyonic instability. The amplification of the gauge field modes exponentially depends on the velocity of the axion field, which in turn slows down the rolling of the axion field when backreaction is taken into account. To illustrate how the strength of the Chern-Simons coupling and the slope of the axion potential influence the particle production, in this paper we consider a toy model in which the axion field is a spectator with a linear potential. In the strong backreaction regime, the energy density of the gauge field quasiperiodically oscillates. The steep slope of the axion potential linearly increases the peak amplitude of the energy density while the strong coupling linearly decreases the peak amplitude. Additionally, we calculate the energy spectrum of gravitational waves.

Lorentz invariance is the cornerstone of relativity theory. Its implications have been verified experimentally with a variety of approaches. The detection of a muon at extremely high energy detected by the ARCA detector in the Mediterranean sea, the most energetic particle directly measured up to date, allows to put additional constraints on Lorentz non-invariant theories. The prediction of some of those theories is that the lifetimes of particles in the laboratory frame 'decrease' rather than 'increase' with increasing $\gamma$. In this frame the sheer fact that the muon traversed the whole ARCA detector puts a lower limit on the muon lifetime in the laboratory frame, that implies upper limits on Lorentz violating parameters.

In the minimal gauged B-L extension of the Standard Model, we demonstrate that PeV-scale dark matter (DM) and the baryon asymmetry of the Universe (BAU) can be simultaneously explained through the three right-handed neutrinos (RHNs) present in the theory. The DM candidate undergoes decay into light neutrinos, providing an explanation for the observed IceCube events, while the other two RHNs generate the BAU via leptogenesis. The breaking of gauge symmetry gives rise to detectable gravitational waves (GWs) from decaying cosmic strings (CS), making this framework testable at several future GW detectors-despite being beyond the reach of conventional collider experiments due to the extremely weak coupling. The symmetry-breaking scale establishes a connection between particle masses, couplings, and the GW spectrum, offering a unified and predictive scenario.

This study presents a novel optimisation technique for atomic structure calculations using the Flexible Atomic Code, focussing on complex multielectron systems relevant to $r$-process nucleosynthesis and kilonova modelling. We introduce a method to optimise the fictitious mean configuration used in the Flexible Atomic Code, significantly improving the accuracy of calculated energy levels and transition properties for lanthanide and actinide ions. Our approach employs a Sequential Model-Based Optimisation algorithm to refine the fictitious mean configuration, iteratively minimising the discrepancy between calculated and experimentally determined energy levels. We demonstrate the efficacy of this method through detailed analyses of Au II, Pt II, Pr II, Pr III, Er II, and Er~III, representing a broad range of atomic configurations. The results show substantial improvements in the accuracy of the calculated energy levels, with average relative differences to the NIST data reduced from 20-60\% to 10\% or less for the ions studied. Transition wavelength calculations exhibit exceptional agreement with experimental data, with about 90\% of the calculated values falling within 10\% of measurements for Pr and Er ions. While improvements in transition probability calculations are observed, the calculated transition probabilities (log($gf$) values) still show significant discrepancies compared to the experimental data, with root mean square deviations of approximately 1.1-1.4 dex for Pr and Er ions. We extend our optimisation technique to systematic calculations of singly and doubly ionised lanthanides, achieving accuracies comparable to or surpassing those of \textit{ab-initio} atomic structure codes. The method's broad applicability across the lanthanide series demonstrates its potential for enhancing opacity calculations and spectral modelling in astrophysical contexts.

This work explores dyonic black bounce (BB) solutions within the framework of General Relativity (GR), coupled with nonlinear electrodynamics (NLED) and scalar fields (SFs). Previous research has employed NLED and SFs to obtain BB solutions in GR; however, these solutions typically assume the presence of either magnetic monopoles or electric charges exclusively as components of the Maxwell-Faraday tensor. In this study, we examine static and spherically symmetric BB solutions that incorporate both magnetic and electric components, forming what are known as dyon solutions. A dyon is a particle characterized by the coexistence of both magnetic and electric charges. We determine the NLED Lagrangian density and the scalar field potential that produce these solutions and analyze the associated gravitational configurations, focusing on horizons, the behavior of the metric function, and spacetime regularity as described by the Kretschmann scalar. Notably, we present the first BB solution derived from the coupling of a linear electromagnetic Lagrangian and a scalar field with an associated potential as the matter source. This work broadens the class of non-singular geometries in the literature and opens new avenues for investigating dyonic BB solutions within the context of other modified gravity theories.

We extend the projected sensitivity of LDMX for sub-GeV dark matter (DM) to the case of dark photons produced through higher order electromagnetic moments. These moments arise from loop diagrams involving portal matter fields, along with the gauge fields of new symmetry groups. Due to the Lorentz structures, in particular the momentum dependence, of these additional interactions, the kinematic distributions expected at missing momentum/energy experiments vary with model in addition to dark photon mass. By considering four additional types of interactions -- magnetic and electric dipole, charge radius, and anapole moment -- we show that LDMX Phase-II is expected to probe the relic target of these additional dark photon models. We compare the analytic with the numerical methods for calculating the dark bremsstrahlung cross section, and compute the kinematic distributions for each model. The potential for model discrimination in the scenario of non-zero signal events at LDMX is discussed. We find that there is a degeneracy between the dark photon mass and model, which can be partially broken by considering both the energy and the transverse momentum of the recoil electron.

In a recent paper [R. Dale. R. Lapiedra, and J. A. Morales-Lladosa, Phys. Rev. D {\bf 107}, 023506 (2023)] a cosmic-like Clauser-Horne-Shimony-Holt (CHSH) inequality was proved for the temperature fluctuations $\delta T$ of the perturbed Cosmic Microwave Background (CMB), assuming local realism. This inequality can be tested from observational data. In fact, no violation for it has been found from the CMB data provided by the COBE satellite in different sky directions. This is a result which, being negative, is not conclusive in relation to the possible violation of the CHSH inequality in a cosmological context. So, the preceding analysis needs to be extended by using more precise current CMB data, like those provided by WMAP and Planck satellites. This is a task of considerable importance but, technically, much more involved in data treatments. In this work, assuming again local realism behind measurements and observational data, this extension is accomplished. The result is that a sound violation of the CHSH inequality is found, which would mean the failure of the assumed local realism in accordance with the quantum origin of the primordial temperature fluctuations in the framework of standard inflation and the orthodox interpretation of the Quantum Mechanics.

The Starobinsky model was born in a cosmological scenario where conformally coupled matter quantum field fluctuations on the vacuum drive a non trivial semiclassical energy momentum tensor quadratic in curvature. The presence of an unstable de Sitter solution of the semiclassical Einstein equations contributed to spread the idea that the early universe could have experienced an inflationary epoch. Effective "$R + R^2$" models of gravity have later gained much attention since their predictions are in very good agreement with the measurements of CMB data and tensor to scalar ratio bounds. In this paper we observe how the Starobinsky model can be well approximated by the asymptotically free quadratic gravity on a part of a renormalization group trajectory (below some high UV scale) which is free from tachyonic instabilities, if a definition of ``physical'' running is employed.