Papers for Monday, Aug 04 2025

The formation of dark-matter halos from small cosmological perturbations generated in the early universe is a highly non-linear process typically modeled through N-body simulations. In this work, we explore the use of deep learning to segment and classify proto-halo regions in the initial density field according to their final halo mass at redshift $z=0$. We compare two architectures: a fully convolutional neural network (CNN) based on the V-Net design and a U-Net transformer. We find that the transformer-based network significantly outperforms the CNN across all metrics, achieving sub-percent error in the total segmented mass per halo class. Both networks deliver much higher accuracy than the perturbation-theory-based model \textsc{pinocchio}, especially at low halo masses and in the detailed reconstruction of proto-halo boundaries. We also investigate the impact of different input features by training models on the density field, the tidal shear, and their combination. Finally, we use Grad-CAM to generate class-activation heatmaps for the CNN, providing preliminary yet suggestive insights into how the network exploits the input fields.

JWST has revealed a new high-redshift population called little red dots (LRDs). Since LRDs may be in the early phase of black hole growth, identifying them in the early universe is crucial for understanding the formation of the first supermassive black holes. However, no robust LRD candidates have been identified at $z>10$, because commonly-used NIRCam photometry covers wavelengths up to $\sim5\,{\rm \mu m}$ and is insufficient to capture the characteristic V-shaped spectral energy distributions (SEDs) of LRDs. In this study, we present the first search for $z\gtrsim10$ LRD candidates using both NIRCam and MIRI imaging from COSMOS-Web, which provides the largest joint NIRCam-MIRI coverage to date ($0.20\,{\rm deg^2}$). Taking advantage of MIRI/F770W to remove contaminants, we identify one robust candidate, CW-LRD-z10 at $z_{\rm phot}=10.5^{+0.7}_{-0.6}$ with $M_{\rm UV}=-19.9^{+0.1}_{-0.2}\,{\rm mag}$. CW-LRD-z10 exhibits a compact morphology, a distinct V-shaped SED, and a non-detection in F115W, all consistent with being an LRD at $z\sim10$. Based on this discovery, we place the first constraint on the number density of LRDs at $z\sim10$ with $M_{\rm UV}\sim-20$ of $1.2^{+2.7}_{-1.0}\times10^{-6}\,{\rm Mpc^{-3}\,mag^{-1}}$, suggesting that the fraction of LRDs among the overall galaxy population increases with redshift, reaching $\sim3\%$ at $z\sim10$. Although deep spectroscopy is necessary to confirm the redshift and the nature of CW-LRD-z10, our results imply that LRDs may be a common population at $z>10$, playing a key role in the first supermassive black hole formation.

We investigate the kilonova emission resulting from outflows produced in a three-dimensional (3D) general-relativistic magnetohydrodynamic (GRMHD) simulation of a hypermassive neutron star (HMNS) remnant. We map the outflows into the FLASH hydrodynamics code to model their expansion in axisymmetry, and study the effects of employing different $r$-process heating rates. Except for the highest heating rate prescription, we find no significant differences with respect to overall ejecta dynamics and morphology compared to the simulation without heating. Once homologous expansion is attained, typically after $\sim$ 2s for these ejecta, we map the outflows to the Sedona radiative transfer code and compute the spectral evolution of the kilonova and broadband light curves in various LSST bands. The kilonova properties depend on the remnant lifetime, with peak luminosities and peak timescales increasing for longer-lived remnants that produce more massive ejecta. For all models, there is a strong dependence of both the bolometric and broadband light curves on the viewing angle. While the short-lived (12ms) remnant produces higher luminosities when viewed from angles closer to the pole, longer-lived remnants (240ms and 2.5s) are more luminous when viewed from angles closer to the equator. Our results highlight the importance of self-consistent, long-term modeling of merger ejecta, and taking viewing-angle dependence into account when interpreting observed kilonova light curves. We find that magnetized outflows from a HMNS -- if it survives long enough -- could explain blue kilonovae, such as the blue emission seen in AT2017gfo.

We present predictions for redshift-space peculiar velocity statistics in the Lagrangian and Eulerian formulations of the effective field theory (EFT) of large-scale structure. We compute 2-point pairwise velocity statistics up to the second moment at next-to-leading (1-loop) order, showing that they can be modeled together with redshift-space galaxy densities with a consistent set of EFT coefficients. We show that peculiar velocity statistics have a distinct dependence on long-wavelength bulk flows that necessitates a variation on the usual infrared (IR) resummation procedure used to model baryon acoustic oscillations (BAO) in galaxy clustering. This can be implemented recursively in powers of the velocity in both the Lagrangian and Eulerian frameworks. We validate our analytic calculations against fully nonlinear N-body simulations, demonstrating that they can be used to recover the growth rate at better than percent level precision, well beyond the statistical requirements of upcoming peculiar velocity surveys and measurements of the kinetic Sunyaev-Zeldovich (kSZ) effect. As part of this work, we release $\texttt{velocisaurus}$, a fast $\texttt{Python}$ code for computing EFT predictions of peculiar velocity statistics.

We report on the discovery of GDR3_526285 ($Gaia$ DR3 Source ID 5262850721755411072), a star with $\rm[Fe/H] = -4.82 \pm 0.25$ and one of the lowest metal ($\text{atomic number} > 2$) mass fractions ever found ($Z_{\rm GDR3\_526585} \lesssim 1.0 \times 10^{-6}$). We first identified it as an ultra metal-poor (UMP; $\rm[Fe/H] < -4$) red giant-branch (RGB) star candidate in the $Gaia$ BP/RP (XP) spectro-photometric catalog ($Gaia$ $G$ magnitude $\approx$15). A combination of multi-band photometry and high-resolution spectroscopic analysis under local thermodynamic equilibrium confirmed the status of GDR3_526285 as a distant ($\approx$24 kpc from the Sun) RGB star ($T_{\rm eff} = 4596\,{\rm K}$, $\log g = 0.88$) in the Milky Way's outer halo. We obtain only an upper limit for the carbon abundance of $\rm[C/H] < -4.32$, resulting in $\rm[C/Fe] < +0.50$. A correction for the evolutionary carbon depletion ($\Delta \rm[C/Fe] = +0.68$) brings the nominal carbon-to-iron ratio upper limit to $\rm[C/Fe]_{\rm cor} < +1.18$. Given its extraordinarily low [C/H], GDR3_526285 likely formed from gas cooled via dust grains rather than fine structure line cooling. The kinematics of GDR3_526285 suggests that this star was either dynamically perturbed by the infall of the Magellanic system or was formerly a member of the Magellanic Clouds and was later stripped by the Milky Way. Our results showcase the potential of an all-sky search for low-metallicity targets with $Gaia$ XP and confirm that the methodology described here is an useful "treasure map" for finding additional UMP stars.

This paper presents the first study of the most massive globular cluster (GC) in the Milky Way, omega Centauri, employing recently acquired JWST deep images. By combining these data with archival Hubble Space Telescope (HST) images, we derived proper motions (PMs) for a significant portion of the JWST field. Our analysis of the colour-magnitude diagram (CMD) reveals two prominent sequences extending from a magnitude F322W2 ~ 17.5 to the bottom of the main sequence (MS). These sequences correspond to the two main stellar populations of omega Centauri: the bMS (He-rich) and rMS (He-normal) populations. The two sequences intersect at the MS knee (F322W2 ~ 19.5) and change positions for lower magnitudes, with the bMS luminosity function (LF) ending at least ~0.5 magnitudes brighter than the rMS LF. We identified a third group of stars (named gMS) along the main sequence located between the two primary ones and conducted a detailed analysis of the LFs and MFs for these three stellar populations. The LFs of these sequences show similar trends, with the rMS being the most populated and the bMS the least. The MFs display distinct power-law slopes: the rMS is well fitted by a single power-law while the gMS and the bMS are characterised by MFs steeper than that of the rMS for masses larger than 0.2 solar masses and flatter MFs for smaller masses. The flattening around ~0.2 solar masses for the gMS and the bMS might be a real feature of the MFs of these populations or due to uncertainties in the adopted mass-luminosity relationship (MLR). The variation in the slope of the MFs of the gMS and bMS contributes to the steepening (flattening) of the combined MF for masses higher (lower) than 0.2 solar masses.

The Gaia mission is transforming our view of the Milky Way by providing distances towards a billion stars, and much more. The third data release includes nearly a million spectra from its Radial Velocity Spectrometer (RVS). Identifying unexpected features in such vast datasets presents a significant challenge. It is impossible to visually inspect all of the spectra and difficult to analyze them in a comprehensive way. In order to supplement traditional analysis approaches, and in order to facilitate deeper insights from these spectra, we present a new dataset together with an interactive portal that applies established self-supervised metric learning techniques, dimensionality reduction, and anomaly detection, to allow researchers to visualize, analyze, and interact with the Gaia RVS spectra in straightforward but under-utilized manner. We demonstrate a few example interactions with the dataset, examining groupings and the most unusual RVS spectra, according to our metric. This combination of methodology and public availability enables broader exploration, and may reveal yet-to-be-discovered stellar phenomena.

In this paper, we analyze the potential variation of the gravitational constant $G$ using data from strong gravitational lensing systems and Type Ia supernovae. Testing $G(z)$ parameterizations where $G(z) = G_0(1 + G_1z)$ and $G(z) = G_0(1 + z)^{G_1}$, we also account for the influence of $G$ on the luminosity of SNe Ia through the Chandrasekhar mass-luminosity relation. Only the flat universe hypothesis is considered. Constraints from 158 lensing systems and the Pantheon+ sample show no significant evidence of $G$ variation. However, although the results are compatible with no variation, the errors are not yet sufficiently restrictive to rule out any variation of $G$ with high statistical confidence. This study highlights the viability of using combined astrophysical data to probe variations in fundamental constants, suggesting that future surveys could refine these constraints.

Upcoming direct-imaging missions like the Habitable Worlds Observatory (HWO) aim to characterize dozens of Earth-like exoplanets by capturing their reflected-light spectra. However, traditional atmospheric retrieval frameworks are too computationally intensive to explore the high-dimensional parameter spaces such missions will generate. Here, we present a one-dimensional convolutional neural network (1D CNN), trained on over one million synthetic, noise-injected spectra simulating Archean, Proterozoic, and Modern Earth analogs, as observed by LUVOIR-B (0.2-2.0 $\mu$m) and HabEx/SS (0.2-1.8 $\mu$m). Our model simultaneously infers six molecular abundances (including biosignatures O$_2$ and O$_3$) along with radius, gravity, surface pressure, and temperature. Inference on unseen test data is performed via Monte Carlo Dropout, enabling uncertainty estimation across thousands of realizations within seconds. The network performs best where spectral features are prominent, accurately recovering CH$_4$ and CO$_2$ in Archean atmospheres and O$_2$ and O$_3$ in Modern cases, while avoiding false positives and outputting near-zero abundances in scenarios of true absence such as Archean O$_2$ and O$_3$. Interpretation via Integrated Gradients confirms that the model bases its predictions on physically meaningful features, including the Fraunhofer A band for O$_2$, and the Hartley-Huggins band for O$_3$. Credibility curve analysis indicates that O$_3$ remains retrievable across a wide range of stellar types and distances, while O$_2$ is detectable out to 12 pc around FG stars. These results elevate the CNN from proof of concept to a mission-ready retrieval engine, capable of processing direct-imaging spectra with HWO on an operational cadence.

While much work has gone into associating neutrino emission with various sources, very few sources have emerged. With the recent publication of IceCube Event Catalog (IceCat-1), the IceCube neutrino observatory has released a list of the most promising astrophysical neutrino events since operations began in 2010. Using the archival data from the High Altitude Water Cherenkov (HAWC) gamma-ray observatory, we perform a coincidence search for gamma rays and neutrinos using a Bayesian Block algorithm with the public IceCube alerts from IceCat-1 and the Astrophysical Multi-messenger Observatory Network (AMON). Of the 350 alerts considered, 25 detections were found, with 1 coinciding with the flaring HAWC source Markarian 421, an active galactic nuclei. We present the performance of this method and a discussion of physics implications.

We compute the full cosmic trajectories of the early Universe across the QCD phase diagram as the plasma cools from $T\simeq500\,$MeV to $30\,$MeV, assuming $\beta$-equilibrated matter. The trajectories are obtained by simultaneously solving baryon-number, electric-charge, and lepton-asymmetry conservation, closed by a state-of-the-art lattice-QCD equation of state: a fourth-order Taylor expansion in the chemical potentials that merges the latest $(2\!+\!1)$-flavor susceptibilities with charm-quark contributions, thus delivering a consistent $(2\!+\!1\!+\!1)$-flavor equation of state. Results are compared with an ideal quark-gluon plasma and with a hadron-resonance gas to highlight interaction effects. Two cases of primordial lepton asymmetries are analyzed: a symmetric configuration $(\ell_e=\ell_\mu=\ell_\tau=\ell/3)$ and an asymmetric one $(\ell_e=0,\;\ell_\mu=-\ell_\tau)$. Increasing $|\ell|$ systematically drives the trajectories toward larger values of $\mu_B$ and more negative $\mu_Q$. In the asymmetric case, a non-monotonic bounce develops when the $\tau$ chemical potential reaches $m_\tau$, generating a maximum in $\mu_B(T)$, the position of which depends on $\ell_\tau$. Assuming a modest $\mu_{Q}$-dependence of the lattice-QCD critical end point estimates (obtained at $\mu_{Q} = 0$), the trajectories for all lepton asymmetries explored ($|\ell|\lesssim 0.1$) lie to their left, implying that in a standard cosmological scenario the QCD transition is almost certainly a smooth crossover. Nevertheless, we estimate the magnitude of baryon and lepton asymmetries needed to obtain a cosmic trajectory closer to the QCD critical point, providing inputs for future studies of the strong-interaction epoch.

HD~5501, a hitherto little studied eclipsing binary with an early A-type primary, has been caught in a short-lived, astrophysically interesting phase of its binary evolution. Recent photometric and spectroscopic observations, including photometric data from {\it TESS}, show it has a highly variable light curve as well as complex spectral variability, particularly in both the absorption and emission components at H~$\alpha$. Our current campaign, including both professional and amateur observers, has determined that the primary is evolving rapidly across the Hertzsprung gap and that, unusually in the case of mass transfer, the orbital period is declining with a characteristic time-scale $P/\dot{P} \approx$ 170,000 years. Significantly, the orbit is eccentric and it appears that mass transfer from the primary to the secondary occurs only near periastron. Modeling indicates the presumed B7 V secondary to be surrounded by an accretion torus, which likely has dynamically chaotic variations in size and shape. Our analysis further implies the presence of a circumbinary disc or shell supplied by mass loss through the Lagrange $L_3$ point. That mass loss appears to account for most of the emission at H$\alpha$. We describe how this astrophysically interesting system may yield valuable information about binary star evolution at the onset of Roche-lobe overflow, as well as insights into eccentricity-modifying mechanisms such as the Soker mechanism.

We present a comprehensive multiwavelength analysis of GRB 240825A, a bright gamma-ray burst (GRB) detected by Fermi and Swift, with a prompt duration ($T_{\rm 90}$ ~ 4 sec in 50-300 keV) near the boundary separating short and long GRBs, prompting a detailed investigation into its classification and progenitor. Using classical prompt metrics (duration, minimum variability timescale (MVT), lag, and spectral hardness) and modern classification techniques (machine-learning (ML) based t-SNE, support vector machine, energy-hardness-duration, and $\epsilon \equiv E_{\gamma,\mathrm{iso},52} / E_{p,z,2}^{5/3}$), we find GRB 240825A exhibits hybrid characteristics. The short MVT (13.830 $\pm$ 1.574 ms), rest-frame duration, and ML-based classification indicate a merger-like or ambiguous nature, while its energetics and position on the Amati relation favor a collapsar origin. We conducted deep optical and NIR photometric and spectroscopic late-time search for an associated supernova (SN)/kilonova (KN) and the host galaxy using 10.4 m GTC and 8.4 m binocular LBT telescopes. No bright SN (like SN 1998bw) is detected down to stringent limits (e.g., $m_r > 26.1$ mag at 17.59 days), despite a redshift of $z$ = 0.659 measured from GTC spectroscopy. Host galaxy SED modeling with Prospector indicates a massive, dusty, and star-forming galaxy-typical of collapsar GRB hosts, though with low sSFR and large offset. We compare these findings with hybrid events like GRB 211211A, GRB 230307A, GRB 200826A, including SNe-GRBs, and conclude that GRB 240825A likely originated from a massive star collapse, with the associated supernova obscured by a dusty host environment or low luminosity SN with absolute magnitude M$_{V}$ fainter than -18.0. This study emphasizes the need for multiwavelength follow-up and a multi-layered classification to determine GRB progenitors.

Observations of WASP-107b suggest a metal-rich and carbon-deprived atmosphere with an extremely hot interior based on detections of SO$_2$, H$_2$O, CO$_2$, CO, NH$_3$, and CH$_4$. In this paper, we aim to determine the reliability of a 1D radiative-convective photochemical-equilibrium (1D-RCPE) retrieval method in inferring atmospheric properties of WASP-107b. Our grid of radiative-convective balanced pressure-temperature profiles and 1D photochemical equilibrated models covers a range of metallicities (Z), carbon-to-oxygen ratios (C/O), intrinsic temperatures (T$_{int}$), and eddy diffusion coefficients (K$_{zz}$). We obtain good fits with our 1D-RCPE retrievals based on a few molecular features of H$_2$O, CO$_2$, SO$_2$, and CH$_4$, but find no substantial contribution of NH$_3$. We find that the degeneracy between metallicity, cloud pressure, and a model offset is broken by the presence of strong SO$_2$ features, confirming that SO$_2$ is a robust metallicity indicator. We systematically retrieve sub-solar C/O based on the relative amplitude of a strong CO$_2$ feature with respect to the broad band of H$_2$O, which is sensitive to a wavelength-dependent scattering slope. We find that high-altitude clouds obscure the CH$_4$-rich layers, preventing the retrievals from constraining T$_{int}$, but that higher values of K$_{zz}$ can transport material above the cloud deck, allowing a fit of the CH$_4$ feature. However, T$_{int}$ and K$_{zz}$ can vary substantially between retrievals depending on the adopted cloud parametrization. We conclude that the 1D-RCPE retrieval method can provide useful insights if the underlying grid of forward models is well understood. We find that WASP-107b's atmosphere is enriched in metals (3 to 5 times solar) and carbon-deprived (C/O <= 0.20). However, we lack robust constraints on the intrinsic temperature and vertical mixing strength.

With over two dozen detections in the Milky Way, double neutron stars (DNSs) provide a unique window into massive binary evolution. We use the POSYDON binary population synthesis code to model DNS populations and compare them to the observed Galactic sample. By tracing their origins to underlying single and binary star physics, we place constraints on the detailed evolutionary stages leading to DNS formation. Our study reveals a bifurcation within the well-known common envelope formation channel for DNSs, which naturally explains an observed split in the orbital periods of the Galactic systems. The two sub-channels are defined by whether the donor star has a helium core (Case B mass transfer) or a carbon-oxygen core (Case C) at the onset of the common envelope, with only the helium core systems eventually merging due to gravitational wave-modulated orbital decay. However, producing DNSs through both sub-channels requires either a generous core definition of $\simeq$ 30% H-fraction or a high common envelope ejection efficiency of $\alpha_{\rm CE}\gtrsim1.2$. By testing different supernova kick velocity models, we find that galactic DNSs are best reproduced using a prescription that favors low velocity kicks ($\lesssim 50 \, \rm km/s$), in agreement with previous studies. Furthermore, our models indicate that merging DNSs are born from a stripped progenitor with a median pre-supernova envelope mass $\sim$ 0.2$M_{\odot}$. Our results highlight the value of detailed evolutionary models for improving our understanding of exotic binary star formation.

Powered by supermassive black holes at their centers, quasars are among the most luminous objects in the Universe, serving as important probes of cosmic history and galaxy evolution. The size of the accretion disc surrounding the black hole is a critical parameter for understanding quasar physics and their potential use as standard candles in cosmology. However, direct measurements of accretion disc sizes have so far been confined to the Local Universe ($z<0.2$), limiting our understanding of quasars during the peak of cosmic activity. Here, we report the first direct measurement of the accretion disc size in the quasar QSO J0455-4216 at $z=2.66$, when the Universe was only $\sim2$ Gyrs old. Medium-band filters mounted on the MPG/ESO 2.2-metre telescope at La Silla Observatory were used to isolate continuum emission regions during a six-month monitoring campaign. The light curves exhibit pronounced variability features and enabled the detection of inter-band time delays from different parts of the disc. We mapped the disc and located its ultraviolet-emitting outermost region at $3.02^{+0.33}_{-0.57}$ light-days from the black hole ($\sim 500$ AU). Given a supermassive black hole 900 million times the mass of the Sun, these measurements validate accretion disc theory at an unprecedented redshift and pave the way for efficient black hole mass estimates, reducing decades-long spectroscopic reverberation campaigns to just a few years or less.

Soft X-ray emission from neutron stars affords powerful diagnostic tools for uncovering their surface and interior properties, as well as their geometric configurations. In the atmospheres of neutron stars, the presence of magnetic fields alters the photon-electron scattering cross sections, resulting in non-trivial angular dependence of intensity and polarization of the emergent signals. This paper presents recent developments of our Monte Carlo simulation, MAGTHOMSCATT, which tracks the complex electric field vector for each photon during its transport. Our analysis encompasses the anisotropy and polarization characteristics of X-ray emission for field strengths ranging from non-magnetic to extremely magnetized regimes that are germane to magnetars. In the very low field domain, we reproduced the numerical solution to the radiative transfer equation for non-magnetic Thomson scattering, and provided analytical fits for the angular dependence of the intensity and the polarization degree. These fits can be useful for studies of millisecond pulsars and magnetic white dwarfs. By implementing a refined injection protocol, we show that, in the magnetar regime, the simulated intensity and polarization pulse profiles of emission from extended surface regions becomes invariant with respect to the ratio of photon ($\omega$) and electron cyclotron ($\omega_{\rm B}$) frequencies once $\omega / \omega_{\rm B} \lesssim 0.01$. This circumvents the need for simulations pertinent to really high magnetic field strengths, which are inherently slower. Our approach will be employed elsewhere to model observational data to constrain neutron star geometric parameters and properties of emitting hot spots on their surfaces.

Stellar coronagraphs designed for high-contrast imaging of exoplanets inevitably introduce a small amount of instrumental polarization, called \emph{secondary polarization}. At the contrast levels required to detect and characterize terrestrial planets, these effects may become significant. Instrumentally induced polarization is often referred to as ``incoherent," yet this use of the term lacks rigor. This work uses Jones calculus and vector field simulations, including interactions with dielectric surfaces to show that the secondary polarization is fully coherent with the input field, but it does not interfere with it due to orthogonality. A key consequence of the coherence secondary polarization is that the process of creating a dark hole in the primary polarization tends to also significantly mitigate the intensity corresponding to the secondary polarization, called the \emph{secondary intensity}, in the dark hole region. This reduction of the secondary intensity may lead to relaxed polarization design requirements in future coronagraphs. Additionally, if the contrast is sufficient to make the secondary intensity non-negligible, modulation schemes to separate the planet from the instrumental light need to account for the modulation of the secondary intensity.

The Subaru-Asahi StarCam is a high-sensitivity live-streaming camera for meteor observation, installed on the dome of the Subaru Telescope at the summit area of Maunakea, Hawai'i. Although it was originally intended to share the Maunakea night sky with the public, including the local Hawai'i community, the system quickly demonstrated its potential for scientific research, owing to its highly sensitive video capabilities and the exceptional fraction of clear nights at the site. The core of the StarCam system features a Sony FX3 camera body paired with an F1.4 wide-angle lens, offering a field of view of 70 deg by 40 deg. Leveraging a state-of-the-art, high-sensitivity CMOS sensor and a bright lens, the system is capable of capturing stars as faint as magnitude 8 in real-time, with an effective frame rate of 15--30 fps. Live streaming via YouTube began in April 2021, and the feed is constantly monitored by more than a hundred viewers at any given nighttime. This has enabled the camera to be used not only for observing regular meteor showers but also for monitoring scientifically important phenomena such as fireballs or unexpected meteor outbursts. Notable scientific achievements include: 1) Detection of the new Arid meteor shower in 2021, 2) Identification of a sub-peak activity in the Gamma-Perseid meteor shower (2021), 3) Detection of the 2022 Tau-Herculid meteor shower outburst, 4) Confirmation of the activity of the Andromedid meteor shower (2021), and 5) Multiple detections of meteor cluster phenomena. We discuss the potential and the future scope of StarCam as an open-access, real-time data platform for citizen science in meteor observations.

Any population of artificial radio broadcasts in a galaxy contributes to its integrated radio luminosity. If this radio emission is bright enough, inhabited galaxies themselves form a cosmic population of artificial radio galaxies. We can detect these broadcasts individually or set constraints from their collective emission. Using the formalism in Paper I and II, I set bounds on the artificial radio galaxy population using both of these methodologies. Measured radio source counts set limits on radio broadcasts across the radio spectrum, including the first Search for Extraterrestrial Intelligence (SETI) constraints at ~250 GHz. I compare these with commensal limits from background galaxies in the fields of large SETI surveys. The field limits are more powerful, but generally only over a limited luminosity range and for frequencies with dedicated SETI surveys. The limits are weaker when broadcasts clump into discrete hosts that are themselves extremely rare. I find that the abundance of Kardashev Type III radio broadcast populations is less than one in 10^17 stars, about one in a million large galaxies. I also examine limits for a power-law distribution in broadcast luminosity.

It is generally believed that long duration gamma-ray bursts (GRBs) originate from the core collapse of rapidly spinning massive stars and at least some of them are powered by hyper-accreting black holes. However, definite proofs about the progenitor and central engine of these GRBs have not been directly observed in the past. Here we report the existence of a Quasi-Periodic Oscillation (QPO) signature with periodic frequency $\sim$0.02 Hz in the early X-ray afterglow phase of GRB 220711B. Such a low-frequency QPO likely signals the precession of a relativistic jet launched from a GRB hyper-accreting black hole central engine. The energy injection signature from the \textbf{late} X-ray observations (from $5\times 10^2s\sim 1\times10^4s$) is consistent with the precession hypothesis. The prompt $\gamma$-ray light curve does not show any QPO signature, suggesting that the X-ray flaring emission in the early afterglow phase and prompt emission likely originate from different accretion processess, indicating that the progenitor stars of GRBs have a core-envelope structure with a stratified angular momentum distribution and the late-time accretion disk likely has a misalignment with respect to the rotation axis of the black hole. Such a misalignment is not expected in a canonical collapsar model. As a result, the QPO signature in GRB 220711B may reveal a new formation channel of long GRBs, possibly a stellar-merger-induced core collapse, with the orbital angular momentum of the binary misaligned with the spin axis of the collapsing star.

The $\gamma$-ray light curve of long-duration GRB 220711B, is characterized by a multi-peaked structure with a duration lasting $\sim$105 seconds. More interestingly, the X-ray afterglow light curve is composed of a plateau emission smoothly connected with a $\sim t^{-2}$ segment overlapping some flares followed by an extremely steep decay. By analysing the light curves of both prompt emission and X-ray afterglow, no high-confidence-level quasi-periodic oscillation (QPO) signals are found in the light curves of the prompt emission (e.g., BAT and GBM), but it is found that a QPO signal at $\sim$ 50 s above 6$\sigma$ confidence level indeed exist in the X-ray afterglow. Here, we propose that a supra-massive magnetar as the central engine of GRB 220711B with precession motion is a good interpretation of the features of the X-ray emission. The initial plateau emission and followed decay segment, as well as the extremely steep-decay segment, are consistent with the physical process of supra-massive magnetar spin-down and then collapse into black hole. Moreover, the QPO signal in the X-ray emission can be explained as an effect of the precession motion of the magnetar. If this is the case, one can derive various magnetar parameters such as the initial period ($P_{\rm{0}}$) and surface magnetic field strength ($B_{\rm{p}}$) within a pseudo-redshift range of [1.08, 4.27]. By considering beaming corrections with jet opening angle $5^{\circ}$, we find that $P_{\rm{0}}$ and $B_{\rm{p}}$ lie within the range of [1.87, 6.25] ms and [$1.47\times 10^{16}$, $3.09\times 10^{16}$] G, respectively. The parameter of $B_{\rm{p}}$ is slightly larger than that of other typical long-duration GRBs, but $P_{\rm{0}}$ fall in a reasonable range.

The first detection of an optical counterpart to a gravitational wave signal revealed that collaborative efforts between instruments with different specializations provide a unique opportunity to acquire impactful multi-messenger data. We present results of such a joint search with the Dark Energy Camera (DECam) and Prime Focus Spectrograph (PFS) for the optical counterpart of the LIGO-Virgo-KAGRA event S250328ae, a binary black hole merger candidate of high significance detected at a distance of 511$\pm$82 Mpc and localized within an area of 3 (15) square degrees at 50% (90%) confidence. We observed the 90% confidence area with DECam and identified 36 high-confidence transient candidates after image processing, candidate selection, and candidate vetting. We observed with PFS to obtain optical spectra of DECam candidates, Swift-XRT candidates, and potential host galaxies of S250328ae. In total, 3897 targets were observed by seven pointings covering ~50% of the 90% confidence area. After template fitting and visual inspection, we identified 12 SNe, 159 QSOs, 2975 galaxies, and 131 stars. With the joint observations of DECam and PFS, we found variability in 12 SNe, 139 QSOs, 37 galaxies, and 2 stars. We do not identify any confident optical counterparts, though the association is not ruled out for three variable candidates that are not observed by PFS and 6 QSO candidates without clear variability if the optical counterpart of S250328ae is faint. Despite the lack of confident optical counterparts, this paper serves as a framework for future collaborations between wide-field imagers and multi-object spectrographs to maximize multi-messenger analyses.

Using a 3D non-linear mean-field solar dynamo model, we investigate the magnetic helicity flux and magnetic twist, and tilt parameters of bipolar magnetic regions (BMRs) emerging from the solar convection zone due to the magnetic buoyancy instability. The twist and tilt of the BMR magnetic field are modeled as a result of an effective electromotive force along the rising part of the toroidal magnetic field. This force generates the poloidal field that tilts the whole magnetic configuration. We find that variations of BMR's twist and tilt determine the magnitude and the sign of the magnetic helicity flux on the solar surface. The model shows that the helicity flux associated with the BMR's tilt/twist is the dominant contribution to the BMR helicity at the beginning of the BMR's evolution, while the effect of differential rotation is the main source of the helicity flux at the final stage of the BMR's evolution. We discuss the implications of these effects on the basic properties and variations of the hemispheric helicity rule of active regions on the solar surface.

The Habitable Worlds Observatory (HWO), a flagship ultraviolet/optical/infrared space telescope recommended by the National Academies' Pathways to Discovery in Astronomy and Astrophysics, will require detector technologies capable of supporting significantly larger pixel-count arrays than previous missions. Microwave Kinetic Inductance Detectors (MKIDs), naturally suited to microwave multiplexing readout, are already in use across several balloon-borne missions with FPGA-based systems. To transition this capability to space, we are developing a radiation-hardened detector readout system that builds directly on the technical and environmental requirements defined by the PRIMA mission. PRIMA serves as a critical pathfinder, informing the radiation tolerance, resource constraints, and on-board processing capabilities needed for HWO. In this work, we present our current results on algorithm implementation, hardware architecture, and firmware development using the radiation-hardened AMD Kintex Ultrascale FPGA, aligning with PRIMA's stringent specifications to ensure compatibility with future space-based observatories like HWO.

The Solar System hosts the most studied and best understood major and minor planetary bodies - and the only extraterrestrial bodies to have been visited by spacecraft. The Solar System therefore provides important constraints on both the initial stages of planetary growth, communicated to us by its surviving planetesimal populations, and for the final result of the planet formation process represented by the architecture of the system and properties of the individual planets. We review here models of planetesimal formation in the outer Solar System as well as the wealth of recent observational constraints that has been used to formulate and refine modern planetesimal formation theory.

Core-collapse supernovae drive nucleosynthesis under extreme thermodynamic conditions, and complex mechanisms are at work prompting the transport of heavy elements from deep stellar interiors into outer layers. We present spatially resolved X-ray spectroscopy of Cassiopeia A's (Cas A) northeastern (NE) jet using the archival 1 Ms Chandra/ACIS observations, and focusing on three fingers of the jet. We report the highest Cr/Fe mass ratio (Cr/Fe $\sim0.14$) ever observed in Cas A, localized in a compact region within the southernmost finger in the NE jet. Comparisons with nucleosynthesis models indicate that the NE jet originated approximately at the boundary separating the complete Si burning layer from the incomplete Si-burning layer. We also find that mixing from different layers is needed to explain the chemical composition of the three fingers in the NE jet. We also detect significant differences in the physical and chemical properties among the three fingers analyzed of the NE jet. In particular, we find that, unlike the other two, the southernmost finger originated from a slightly more peripheral region of the explosion. Moreover, while the northern and central fingers lie almost in the plane of the sky, the southernmost finger is moving in a different direction, showing a velocity along the line of sight of $\sim2100$ km s$^{-1}$ towards the observer, with a tilt angle of $\sim16$\textdegree. These findings highlight the NE jet's role in ejecting material from the deepest explosive burning layers, providing new insights into the asymmetries originating in the inner layers of core-collapse supernovae.

The 21 cm radiation of neutral hydrogen provides crucial information for studying the early universe and its evolution. To advance this research, countries have made significant investments in constructing large low-frequency radio telescope arrays, such as the Low Frequency Array (LOFAR) and the Square Kilometre Array Phase 1 Low Frequency (SKA1-low). These instruments are pivotal for radio astronomy research. However, challenges such as ionospheric plasma interference, ambient radio noise, and instrument-related effects have become increasingly prominent, posing major obstacles in cosmology research. To address these issues, this paper proposes an efficient signal processing method that combines wavelet transform and mathematical morphology. The method involves the following steps: Background Subtraction: Background interference in radio observation signals is eliminated. Wavelet Transform: The signal, after removing background noise, undergoes a two-dimensional discrete wavelet transform. Threshold processing is then applied to the wavelet coefficients to effectively remove interference components. Wavelet Inversion: The processed signal is reconstructed using wavelet inversion. Mathematical Morphology: The reconstructed signal is further optimized using mathematical morphology to refine the results. Experimental verification was conducted using solar observation data from the Xinjiang Observatory and the Yunnan Observatory. The results demonstrate that this method successfully removes interference signals while preserving useful signals, thus improving the accuracy of radio astronomy observations and reducing the impact of radio frequency interference (RFI).

A gas giant forms a small gas disk called a "circumplanetary disk (CPD)" around the planet during its gas accretion process. The small gas disk contains dust particles like those in a protoplanetary disk, and these particles could be the building material of large moons. A young T Tauri star PDS 70 has two gas accreting planets, and continuum emission from one of the forming planets, PDS 70 c, has been detected by ALMA Bands 6 and 7, which is considered as the dust thermal emission from its CPD. We reproduce the emission with both bands and predict how the dust emission will be observed by ngVLA by expanding the range of the wavelength from submillimeter to centimeter. We find that the flux density of the dust thermal emission can be detected with ngVLA at Band 6 (3 mm) and probably with Band 5 (7 mm) as well. We also find that the size and shape of the CPD can be constrained by observations of ngVLA Band 6 with reasonable observation time.

A subset of low-mass giants ($<2.2\,M_{\odot}$) exhibit anomalous lithium enhancement behavior, which is still an open topic. Given that more massive giants retain more surface lithium, increasing mass by accreting circumstellar matter could be a channel to enrich lithium. We evaluate this process in the current work. Using MESA, we construct a model of matter accretion, including mass loss, that evolves a star from the main sequence turnoff to the red giant branch tip. The mean accretion rate is estimated from the upper limit of the accreted mass and the evolutionary time of the star during this period, and a grid of accretion rates is constructed. We separately consider their effects on the lithium enhancement of giants, both in terms of the mass and the composition of accretion. Accreting matter with higher lithium abundances has a promoting effect on the lithium enhancement of giants. The accreted matter with excess lithium alleviates the dilution of lithium in the convective envelope during the first dredge-up. The added mass results in lower temperatures at the bottom of the convective envelope, which likewise weakens the depletion of surface lithium. Weak accretion of circumstellar matter is a possible route to lithium enhancement for giants, and it predicts an upper limit on the lithium abundance of $\rm \sim 2.5\,dex$. However, the mass increment it requires poses a potential challenge to real astrophysical environments. Such accretion suppresses lithium dilution and depletion of the star during the first dredge-up, thus exhibiting lithium enhancement behavior.

We investigate the geometrical effects affecting the production and absorption of gamma-ray radiation emitted in inverse Compton scattering in the synchrotron-self-Compton process. We evaluate the effect of the anisotropy of the radiation field seen by the scattering electrons homogeneously distributed in the emission region. Next, we also consider inhomogeneous distribution of electrons and investigate the effect of it in the spherically symmetric emission region. We also study a cylindrical shape of the emission region and its effect on the isotropy of the emitted radiation. We obtain simple numerical factors that scale the emission for different assumptions about the geometry of the emission region and the distribution of the emitting electrons. For a 3D Gaussian spatial distribution of the electrons we obtain 0.222 times lower flux than for homogeneous emission region. Finally, we also evaluate the absorption of the radiation produced in the different scenarios, and compare the full calculations with the two most commonly assumed simplifications. We find that for cases when the absorption is lesser than by one order of magnitude, the full calculations for homogeneous sphere can be well approximated with homogeneously-emitting slab, while the absorption in the case of 3D Gaussian distribution of electrons is significantly weaker.

Studying stream interaction regions (SIRs), from their inception and the dynamics of their development, can provide insight into solar-terrestrial connections. Some in-situ instruments on the Solar Orbiter (SolO) space mission are designed to measure solar wind (SW) and interplanetary magnetic field parameters along the flight path. These instruments are ideal for studying the dynamics of SIR evolution at heliocentric distances of 0.28-1.0 AU and with changes in heliolatitude of 0^{\circ} - 33^{\circ}. To address the challenges of promptly identifying SIRs and predicting their arrival time on Earth, we consider using trigger events from the Radio and Plasma Wave (RPW)/SolO instrument, which are transmitted in telemetry data packages. We suggest that multiple activations of the trigger mode (SBM1 mode) in the RPW instrument over an interval of up to four hours may reflect the fine structure of large-scale events in SW. Such events can serve as markers for the spacecraft's location within the SIR. In this regard, the 2023 analysis revealed that multiple activations of the SBM1 trigger mode throughout the day accounted for more than 50\% of the total number of days for which such events were recorded. Of this number, 63\% were events when the trigger algorithm was prompted repeatedly within a time interval of up to four hours. A comparison of the registration times of SBM1 trigger events with the SW parameters obtained from the SWA-PAS and MAG instruments showed that repeated activations of the trigger algorithm occurred at the stream interface surface when a high-speed SW stream and a formed compression region were present.

We present an observational evidence supporting the scenario that the protogalactic angular momenta play the most decisive role in molding the optical sizes of present galaxies. Analyzing the NASA-Sloan Atlas catalog in the redshift range of $0.02\le z<0.09$, we observationally determine the probability density distributions, $p(r_{50})$ and $p(r_{90})$, where $r_{50}$ and $r_{90}$ denote the galaxy sizes enclosing $50\%$ and $90\%$ of their $r$-band luminosities, respectively. Both of the distributions are found to be well described by a bimodal Gamma mixture model, which is consistent with the recent numerical results. Classifying the local galaxies by their ratios, $r_{50}/r_{90}$, we also show that for the case of late-type galaxies with $r_{50}/r_{90}\ge 0.45$ both of $p(r_{50})$ and $p(r_{90})$ exhibit no bimodal feature, following a unimodal Gamma model. Assuming the existence of a linear causal correlation between $\{r_{50},r_{90}\}$ of the late-type galaxies and the primordial spin factor, $\tau$, defined as the degree of misalignments between the initial tidal and protogalaxy inertia tensors, we reconstruct the probability density distributions, $p(\tau)$, directly from the observationally determined $p(r_{50})$ and $p(r_{90})$ of the late-type galaxies, and show excellent agreements with the real distributions of $\tau$ which were determined at the protogalactic stages by numerical experiments. A critical implication of our result on reconstructing the initial conditions from observable galaxy sizes is discussed.

Many Galactic globular clusters (GCs) originated in diverse host galaxies before being subsequently incorporated into the Milky Way through hierarchical galaxy assembly. Identifying their origins is crucial for revealing galaxy properties at early times. Traditional classification methods relying on dynamical properties face inherent uncertainties stemming from the evolving Galactic potential and complex merger histories. Chemically driven classification confronts a distinct obstacle: multiple populations - abundance variations in light elements of GC members. In this Letter, we identify primordial populations exhibiting lower [Al/Fe] as reliable tracers of their birth environments' chemical evolution. A clear chemical dichotomy emerges between in-situ and accreted GC populations at [Fe/H] > -1.5, particularly in the [Mg/Fe]-[Al/Fe] plane, indicating that their progenitor galaxies have experienced fundamentally different enrichment histories. While our chemically driven classification demonstrates general consistency with dynamically driven classifications, notable discrepancies emerge: NGC 288 and M4 are reclassified as in-situ, and Terzan 9 as accreted. This chemically driven GC classification provides promising application for Galactic archaeology.

The progenitors of Type II-P supernovae (SNe) are generally considered to be red supergiants; however, the so-called "red supergiant problem" indicates that a deeper investigation into the progenitors of this class of SNe is necessary. SN 2009ib and SN 2012ec are two Type II-P SNe for which progenitor candidates have been identified in pre-explosion images. In this work, we use new, late-time Hubble Space Telescope observations to search for the disappearance of these two candidates and confirm their nature. In the case of SN 2009ib, the late-time high-resolution imaging reveals that the progenitor candidate is in fact a blend of multiple unresolved stars. Subsequent difference imaging shows no significant change in brightness at the SN's position even years after the explosion. These findings indicate that the flux from the previously identified source is dominated by unresolved field stars, with little to no contribution from the genuine progenitor. In the case of SN 2012ec, a comparison of pre-explosion and late-time images reveals that the progenitor candidate faded by about 0.6 mag in the F814W band seven years after the explosion, confirming the disappearance of the progenitor.

We present the results of a search for megaparsec-scale sources in the NVGRC catalog of candidates of giant radio source (GRS) based on the NVSS sky survey. We visually inspected 370 NVGRC sources, as well as radio sources falling within a neighborhood of about one square degree around the target object. In the studied sample, 48% of objects were classified as giant radio sources, 14% as sources with a projected linear size of less than 0.72 Mpc, and 38\% as physically unrelated objects combined by the recognition algorithm into one radio source. We identified 197 gaints, of which 72 radio sources are known GRGs or GRQs, and 125 sources were identified by us as GRS for the first time. Comparing the proportion of FRI giants in four redshift bins, we found that for z<0.05, the proportions of FRI and FRII sources were approximately equal, but already at z>0.15 the proportion of FRI giants decreases sharply. The predominance of FRII giants in the GRS lists is most likely due to observational selection due to the sensitivity limit of existing radio surveys. Comparing the NVSS and VLASS cutouts, we found that 33% of sources can be classified as fadded. 25% of the sources show a restart of the radio source phase. 38% of the sources have deformed radio lobes. Our GRS sample includes 74% of galaxies, 15% of IR-excess galaxies, which, according to the WISE photometric data, can be attributed to quasars, and 11% of quasars. When visually examining the optical survey cutouts, we noted the presence of close neighbors for the hosts and/or their belonging to known groups or clusters of galaxies. Close neighbors at a distance of less than 50 kpc were found for 39% of radio sources, and 28% of sources are part of groups or clusters of galaxies. Thus, about 70% of gaints are in a fairly dense environment, and this proportion may be higher.

We compute the two-loop effective field theory (EFT) power spectrum of dark matter density fluctuations in $\Lambda$CDM using the recently proposed COBRA method (Bakx. et al, 2025). With COBRA, we are able to evaluate the two-loop matter power spectrum in $\sim 1$ millisecond at $ \sim 0.1 \%$ precision on one CPU for arbitrary redshifts and on scales where perturbation theory applies. As an application, we use the nonlinear matter power spectrum from the Dark Sky simulation to assess the performance of the two-loop EFT power spectrum compared to the one-loop EFT power spectrum at $z=0$. We find that, for volumes typical for Stage IV galaxy surveys, $V = 25 \,(\text{Gpc}/h)^3$, the two-loop EFT can provide unbiased cosmological constraints on $\Omega_m,H_0$ and $A_s$ using scales up to $k_\text{max}=0.26\, h/\text{Mpc}$, thereby outperforming the constraints from the one-loop EFT ($k_\text{max}=0.11\, h/\text{Mpc}$). The Figure of Merit on these three parameters increases by a factor $\sim 1.9$ and the one-dimensional marginalized constraints improve by $\sim35\%$ for $\Omega_m$, $\sim20\%$ for $H_0$ and $\sim 15\%$ for $A_s$.

The substellar initial mass function (IMF) and the formation mechanisms of brown dwarfs (BDs) remain key open questions in star formation theory. IMF characterization in a large number of star-forming regions (SFRs) is essential for constraining these processes. We aim to identify and spectroscopically confirm very low-mass members of the Corona Australis (CrA) SFR to refine its substellar census, determine its low-mass IMF, and compare it to other clusters. Using deep I-band photometry from SuprimeCam/Subaru and data from the VISTA Hemisphere Survey, we identified low-mass BD candidates in CrA. We subsequently obtained NIR spectra of 173 of these candidates with KMOS/VLT, as well as optical spectra for 8 kinematic candidate members using FLOYDS/LCO. The kinematic candidates are confirmed as low-mass stellar members with spectral types M1 to M5. In contrast, all 173 BD candidates observed with KMOS are identified as contaminants. Although the follow-up yielded no new substellar members, it places strong constraints on the number of undetected substellar objects in the region. Combined with literature data, this enables us to derive the substellar IMF, which is consistent with a single power-law slope of alpha = 0.95+-0.06 in the range 0.01-1 MSun or alpha = 0.33+-0.19 in the range 0.01-0.1 MSun. The star-to-BD ratio in CrA is about 2. We also provide updated IMFs and star-to-BD ratios for Lupus3 and ChaI from the SONYC survey, reflecting revised distances from Gaia. Finally, we estimate surface densities and median FUV fluxes for 6 SFRs and clusters and compare their substellar populations as a function of environmental properties. The IMF and star-to-BD ratio show no clear dependence on stellar density or ionizing flux from the massive stars. A combined effect - where one factor enhances and the other suppresses BD formation - also appears unlikely. (Abridged)

Cosmic microwave background data from the Planck satellite, combined with baryon acoustic oscillation measurements from the Dark Energy Spectroscopic Instrument and Type Ia supernovae from various samples, provide hints of dynamical dark energy (DE). These results indicate a peak in the DE density around $z\sim 0.4-0.5$, with the highest significance observed when using the supernovae from the Dark Energy Survey. In this Letter, we show that this peak does not necessarily imply a true crossing of the phantom divide if the measured effective DE is not a single component, but a combination of standard and negative quintessence. The latter is characterized by negative energy density and positive pressure, both decreasing in absolute value and tending to 0 in the future. For appropriate values of the parameters, negative quintessence is relevant at intermediate redshifts and becomes subdominant in front of standard quintessence around $z\sim 0.4-0.5$, giving rise to the aforementioned peak in the DE density. We find that our model is preferred over $\Lambda$CDM at a $3.27\sigma$ CL, which is comparable to the level of exclusion found with the Chevallier-Polarski-Linder parametrization. Our analysis leaves open the possibility of negative quintessence and other exotic fields existing in the low-energy universe, potentially playing a significant role in cosmic dynamics.

The space-based CUbesat Solar Polarimeter (CUSP) mission aims to measure the linear polarization of solar flares in the hard X-ray band by means of a Compton scattering polarimeter. CUSP will allow to study the magnetic reconnection and particle acceleration in the flaring magnetic structures of our star with its unprecedented sensitivity to solar flare polarization. CUSP is a project in the framework of the Alcor Program of the Italian Space Agency aimed to develop new CubeSat missions. It has been proposed as a constellation of a two Cubesat mission to monitor the Sun for Space Weather, and will proceed with a single-satellite asset in its baseline implementation. In the frame of CUSP's Phase B study, that started in December 2024 for a 1-year period, we present the development status of this dual-phase polarimeter. Preliminary laboratory results using two chains of acquisition will be discussed. The first chain of acquisition, based on the Hamamatsu R7600 multi-anode photomultiplier tubes coupled to plastic scintillator bars and read out by the MAROC-3A ASIC, is used to detect the Compton scattering of incoming photons. On the other hand, GAGG crystals coupled to avalanche photo-diodes with a readout based on the SKIROC-2A ASIC are used to absorb the scattered photons. By reconstructing the azimuthal scattering direction for many incoming photons, one can infer the linear polarization degree and angle of the source. We will discuss the calibration results obtained with our prototype detector by using well-known radioactive isotopes, allowing us to assess the performances of our detector over the full 25-100 keV energy range.

The CUbesat Solar Polarimeter (CUSP) project is a CubeSat mission orbiting the Earth aimed to measure the linear polarization of solar flares in the hard X-ray band by means of a Compton scattering polarimeter. CUSP will allow to study the magnetic reconnection and particle acceleration in the flaring magnetic structures of our star. CUSP is a project in the framework of the Alcor Program of the Italian Space Agency aimed to develop new CubeSat missions. CUSP undergoing the Phase B started in December 2024 that will last for 12 month. The Compton polarimeter of the CUSP payload performs coincidence measurements between plastic scintilaltors and GaGG(Ce) crystals to derive the polarization of X-rays. These sensors are readout by Multi Anode Photomultiplier Tubes (MAPMTs) and Avalanche Photodiodes (APDs) respectively. Both sensors need an HV power supply up to -1~kV (for the MAPMT) and +500~V (for the APD). We tested precision regulated High Voltage DC/DC Converters by HVM Technology Inc. with Sub-Miniature Case Size ($0.85''\times0.85''\times0.60''$) of the SMHV series. These modules are compact and suited for CubeSat missions.

Lorentz symmetry is a cornerstone of modern physics, and testing its validity remains a critical endeavor. In this work, we analyze the photon time-of-flight and time-shift data from LHAASO observations of Gamma-Ray Burst GRB 221009A to search for signatures of Lorentz violation. We employed the DisCan (dispersion cancellation) method with various information entropies as cost functions, designating the results obtained with Shannon entropy as our representative outcome. This choice is attributed to the parameter-free statistical properties of Shannon entropy, which has demonstrated remarkable stability as we continually refine and enhance our methodology. In the absence of more detailed data and physical context, it provides more stable and reliable results. We constrain the energy scale associated with Lorentz invariance violation. Our results yield 95\% confidence level lower limits of $E_{\text{QG},1} > 5.4 \times 10^{19} \, \text{GeV}$ (subluminal) and $E_{\text{QG},1} > 2.7 \times 10^{19} \, \text{GeV}$ (superluminal) for the linear case ($n$=1), and $E_{\text{QG},2} > 10.0 \times 10^{12} \, \text{GeV}$ (subluminal) and $E_{\text{QG},2} > 2.4 \times 10^{12} \, \text{GeV}$ (superluminal) for the quadratic case ($n$=2). Subsequently, we incorporated WCDA photons and the Knuth binning method to further optimize and complement our approach, while also performing filter using information entropies. Furthermore, we demonstrate that employing different information entropy measures as cost functions does not alter the order of magnitude of these constraints.

The CUbesat Solar Polarimeter (CUSP) project is an Earth-orbiting CubeSat mission designed to measure the linear polarization of solar flares in the hard X-ray band using a Compton scattering polarimeter. CUSP will enable the study of magnetic reconnection and particle acceleration within the Sun's flaring magnetic structures. This project is being developed within the framework of the Italian Space Agency's Alcor Program, which aims to foster new CubeSat missions. CUSP entered its Phase B in December 2024, a phase scheduled to last 12 months. This paper reports on the current status of the CUSP mission design, mission analysis, and payload scientific performance.

The magnitude gap between the central and satellite galaxies encodes information about the mass accretion history of a dark matter halo, and serves as a useful observational probe for the mass distribution in a halo. In this work, we perform the first weak lensing test of the connections between the magnitude gap and the halo profile. We measure the halo profiles of isolated central galaxies (ICGs) selected primarily from the SDSS Main Galaxy Sample. Halo mass and concentration are inferred by fitting stacked lensing profiles in bins of central luminosity, $L_\mathrm{c}$, and the central-satellite magnitude gap, $L_\mathrm{gap}$. We detect dependence on the magnitude gap in both halo properties. The dependence is the strongest in the ICG luminosity range of $10^{10.3}<L_\mathrm{c}[h^{-2}L_\odot]\leq 10^{10.7}$, where halos with smaller gaps have higher masses and lower concentrations. When $10^{10.7} <L_c[h^{-2}L_\odot] \leq 10^{11.1}$, however, no significant gap dependence is detected. In the range of $10^{9.9}<L_\mathrm{c}[h^{-2}L_\odot] \leq 10^{10.3}$, a disordering of the gap dependence is marginally observable. We compare the observational results with predictions by two lightcone catalogs built from the Illustris TNG300 and the Millennium simulations. The gap dependence in the two mock samples show overall consistency with observations, but neither matches them in all $L_\mathrm{c}$ bins to a quantitative level. We also compare the significance of the gap dependence on halo mass and concentration and find that our measurement prefers gap dependence in both parameters, while the halo mass dependence is preferred over the concentration if only one of the two dependencies is allowed.

We present the first detailed chemical abundances for seven GD-1 stream stars from Subaru/HDS spectroscopy. Atmospheric parameters were derived via color calibrations ($T\rm_{eff}$) and iterative spectroscopic analysis. LTE abundances for 14 elements ($\alpha$, odd-Z, iron-peak, n-capture) were measured. Six stars trace the main orbit, one resides in a `blob'. All exhibit tightly clustered metallicities ([Fe/H] = -2.38, {\bf intrinsic dispersion smaller than 0.05 dex, average uncertainty is about 0.13 dex}). While one star shows binary mass transfer signatures, the other six display consistent abundance patterns (dispersions $<$ uncertainties). Their iron-peak elements (Sc, Cr, Mn, Ni) match Milky Way halo stars. In contrast, Y and Sr are systematically lower than halo stars of similar [Fe/H]. Significantly, six stars show consistently enhanced [Eu/Fe] $\sim$ 0.60 ($\sigma$ = 0.08). A tight Ba-Eu correlation (r = 0.83, p=0.04) exists, with [Ba/Fe] = -0.03 $\pm$ 0.05, indicating a common r-process origin. This extreme chemical homogeneity strongly supports an origin from a single disrupted globular cluster. The lack of light-element anti-correlations may stem from our sample size or the progenitor's low mass.

Double-peaked \oiii~profiles could potentially indicate kiloparsec-scale dual AGNs. We analyze long-term optical light curves of 35 type 1 AGNs with such features from our recent catalog in Zheng et al. (2025). These light curves are obtained from the Catalina Sky Survey and modeled using a Damped Random Walk (DRW) process. A control sample of 210 normal type 1 AGNs matched in redshift, intrinsic luminosity, and black hole mass is also studied. If the double-peaked \oiii~are caused by two type 1 AGNs (dual type 1 AGN), then the combined variability from the two AGNs would be expected to differ from that of a single type 1 AGN. However, there is no statistically significant difference in the variability timescale $\tau$ and intrinsic variability amplitude $\sigma$ between these double-peaked AGNs and the control sample of 210 normal type 1 AGNs. Crucially, computer simulations reveal that dual AGN systems systematically produce lower variability amplitudes than single AGNs, which is inconsistent with the observed variability properties of our double-peaked \oiii~sample. Moreover, simulations suggest that the fraction of dual type 1 AGNs is $\sim$ 3\%, indicating that double-peaked \oiii~may not be a reliable indicator of dual type 1 AGNs in these systems. However, this does not rule out the possibility that some objects may still host dual AGNs involving other combinations, such as type 1+type 2 AGNs. Future studies with larger samples and higher-quality light curves will help clarify the true nature of these systems.

Deflection of light along the optical path is a major source of image degradation for ground-based telescopes. Methods have been developed to measure upper atmospheric seeing based on models of the turbulence in the atmosphere, but due to boundary conditions, transmission within telescope enclosures is more complex. The Multi-beam Optical Seeing Sensor (MOSS) directly measures the component of the image quality degradation from inhomogeneity of the index of refraction within the telescope dome. MOSS outputs four near-parallel beams of light that travel along the optical path and are imaged by the telescope's detector, landing like starlight on the telescope's focal plane. By using a strobed light source, we can 'freeze' the instantaneous index variations transverse to the optical path. This system captures both 'dome' and 'mirror' seeing. Through plotting the standard deviation of differential motion between pairs of beams, MOSS enables characterization of the length scale of turbulence within the dome. The temporal coherence of temperature gradients can be probed with different pulse lengths, and the spatial coherence by comparing pairs at different separations across the aperture of the telescope. Optical path turbulence measurements, alongside other telemetry metrics, will guide thermal and airflow management to optimize image quality. A MOSS prototype was installed in the 1.2 meter Auxiliary Telescope (AuxTel) at the Vera C. Rubin Observatory in Chile, and preliminary data constrain the optical path turbulence with a lower bound of 1.4 arcseconds. The optical path turbulence varied throughout the night of observing.

The Sagittarius Dwarf Galaxy is undoubtedly being disrupted in the tidal field of the Milky Way. The Milky Way disc is also found to be in a state of disequilibrium. The role of the Sagittarius in driving or contributing to this disequilibrium has been extensively investigated. Most of these studies, however, assume an initially near-equilibrium disc. It was also hypothesized that the passage of Sagittarius could have increased the star-forming activity in the Solar Neighbourhood. We check whether galaxies that have undergone cosmological evolution are affected by interactions analogous to those between the Sagittarius and the Milky Way. We use the high-resolution simulation TNG50 to look for pairs similar to the Milky Way and Sagittarius. We search within redshift z=1-0 for discs from the MW/M31 sample that interacted with a satellite more massive than 10 billion Msun, had a pericenter smaller than 50 kpc, and was on an approximately polar orbit. We exclude cases where, within 1 Gyr of the pericenter, a similar interaction occurred. In 90 percent of cases, a passage of the Sagittarius analogue had no significant effect on either the vertical velocity field of the disc or the star formation history. A response in vertical stellar kinematics can be found mostly in cold discs and mildly correlates with the strength of interactions. For star formation, the studied interactions had an effect only when little to no star formation was ongoing prior to the interaction, often due to previously disturbed star-forming discs, e.g., from AGN activity. Our results indicate that stellar discs in TNG50 are frequently vertically perturbed preceding pericenter passages of Sagittarius analogues. Future studies using other simulations and extragalactic surveys will help establish whether vertical disequilibrium is a common feature of disc galaxies or an artifact of the specific setup studied.

The origin of large scale magnetic fields in the Universe is widely thought to be from early Universe processes, like inflation or phase transitions. These magnetic fields evolve via magnetohydrodynamic processes until the epoch of recombination. When structures begin to form in the later Universe, the conservation of magnetic flux amplifies the magnetic fields via the adiabatic collapse of gravitationally bound gas clouds hosting the magnetic fields and moves them to smaller scales. In this work, we have semi-analytically studied this forward cascade effect, considering simple models of gravitational collapse of structures. We find that this simple model is able to reproduce the general qualitative features of the evolution of the magnetic field spectrum as seen from magnetized cosmological simulations.

The non-linear relation between the UV and X-ray luminosity in quasars has been studied for decades. However, as we lack a comprehensive model able to explain it, its investigation still relies on observational efforts. This work focuses on optically selected quasars detected by eROSITA. We present the properties of the sources collected in the eROSITA early data release (eFEDS) and those resulting from the first six months of eROSITA all-sky survey (eRASS1). We focus on the subset of quasars bright enough in the optical/UV band to avoid an ''Eddington bias'' towards X-ray brighter-than-average spectral energy distributions. The final samples include 1,248 and 519 sources for eFEDS and eRASS1, up to redshift $z\approx3$ and $z\approx1.5$, respectively. We found that the X-ray$-$UV luminosity relation shows no significant evolution with redshift, and its slope is in perfect agreement with previous compilations of quasar samples. The intrinsic dispersion of the relation is about 0.2 dex, which is small enough for possible cosmological applications. However, the limited redshift range and statistics of the current samples do not allow us to obtain significant cosmological constraints yet. We show how this is going to change with the future releases of the eROSITA data.

Estimating properties of star clusters from unresolved broadband photometry is a challenging problem that is classically tackled by spectral energy distribution (SED) fitting methods that are based on simple stellar population (SSP) models. However, because of their exponential scaling, grid-based methods suffer from computational limitations. In addition, stochastic latent variables in the model can make the computation of the likelihood function intractable. These limitations can be overcome by modern generative deep learning methods that offer flexible and powerful tools for modeling high-dimensional posterior distributions and fast inference from learned data. We present a normalizing flow approach for the inference of cluster age, mass, and reddening from Hubble Space Telescope (HST) broadband photometry. In particular, we explore our network's behavior on an inference problem that has been analyzed in previous works. We used the SED modeling code CIGALE to create a dataset of synthetic photometric observations for $5 \times 10^6$ mock star clusters. Subsequently, this data set was used to train a coupling-based flow in the form of a conditional invertible neural network (cINN) to predict posterior probability distributions for cluster age, mass, and reddening from photometric observations. We predicted cluster parameters for the 'Physics at High Angular resolution in Nearby GalaxieS' (PHANGS) Data Release 3 catalog. To evaluate the capabilities of the network, we compared our results to the publicly available PHANGS estimates and found that the estimates agree reasonably well. We demonstrate that normalizing flow methods can be a viable tool for the inference of cluster parameters, and argue that this approach is especially useful when latent variables make the computation of the likelihood intractable and in scenarios that require efficient density estimation.

We searched for young asteroid families -- those with ages t_age < 10 Myr and at least three members -- using the proper element catalog from Nesvorny et al. (2024). Our approach employed the Hierarchical Clustering Method (HCM) in a five-dimensional space of proper orbital elements: semimajor axis, eccentricity, inclination, proper nodal longitude, and proper perihelion longitude. The proper longitudes were calculated for various times in the past. Any convergence of these angles at times t < 10 Myr ago was automatically identified by our algorithm as a clustering event in 5D space at time t. Using this method, we successfully recovered all previously known young families (over 40) and discovered 63 additional ones. The formation ages of these families were determined through backward orbital integrations. To validate orbital convergence, we applied three different methods and obtained generally consistent results. Notably, the vast majority of identified young families have the formation ages t_age < 1 Myr. The number and properties of these families provide valuable constraints on the frequency of recent large cratering or catastrophic collisions, offering new insights into the ongoing collisional evolution of the main asteroid belt. Alternatively, at least some of the families identified here could have been produced by the spin-up and rotational fission of their parent bodies. Future studies should address the relative importance of collisions and rotational fission for young asteroid families identified here.

We investigate a relativistic cosmological model with background rotation, sourced by a non-perfect fluid with anisotropic stress. A modified version of the CLASS Boltzmann code is employed to perform MCMC analyses against Cosmic Microwave Background (CMB) and late-time datasets. The results show that current CMB data constrain the present-day rotation parameter to be negligible. As a consequence, the derived cosmological parameters remain consistent with the standard $\Lambda$CDM values. In contrast, late-time probes such as Type Ia supernovae (SNe) and Baryonic Acoustic Oscillations (BAO) allow for a higher level of rotation and yield an increased Hubble constant. However, this comes at the cost of a higher $\sigma_8$, which remains in tension with DES-Y3 measurement. Combining CMB, SNe and BAO data confirms the preference for non-rotation.

We present a novel formation channel for supermassive black hole (SMBH) binaries in the early Universe, driven by primordial black holes (PBHs). Using high-resolution hydrodynamical simulations, we explore the role of massive PBHs ($m_{\rm BH} \sim 10^6 M_\odot$) in catalyzing the formation of direct-collapse black holes (DCBHs), providing a natural in situ pathway for binary SMBH formation. PBHs enhance local overdensities, accelerate structure formation, and exert thermal feedback on the surrounding medium via accretion. Lyman-Werner (LW) radiation from accreting PBHs suppresses H$2$ cooling, shifting the dominant gas coolant to atomic hydrogen. When combined with significant baryon--dark matter streaming velocities ($v_{\rm b\chi} \gtrsim 0.8 \sigma_{\rm b\chi}$, where $\sigma_{\rm b\chi}$ is the root-mean-square streaming velocity), these effects facilitate the formation of dense, gravitationally unstable, atomically cooling gas clouds in the PBH wake. These clouds exhibit sustained high inflow rates ($\dot{M}_{\rm infall} \gtrsim 10^{-2}-10^{-1} M_\odot \mathrm{yr}^{-1}$), providing ideal conditions for DCBH formation from rapidly growing supermassive stars of $\sim 10^5 M_\odot$ at redshift $z\sim 10-20$. The resulting systems form SMBH binaries with initial mass ratios $q\sim O(0.1)$ and separations of $\sim 10$ pc. Such PBH--DCBH binaries provide testable predictions for JWST and ALMA, potentially explaining high-$z$ sources such as Little Red Dots, and represent gravitational-wave sources for future missions like LISA and TianQin, bridging early-Universe black hole physics, multi-messenger astronomy, and dark matter theory.

The CUbesat Solar Polarimeter (CUSP) aims to measure the linear polarization of solar flares in the 25-100 keV X-ray band using a Compton scattering polarimeter. CUSP will allow us to study the magnetic reconnection and particle acceleration in the flaring magnetic structures of our star by providing high-sensitivity polarization measurements. CUSP is a project in the framework of the Alcor Program of the Italian Space Agency aimed to develop innovative CubeSat technologies and missions. As part of CUSPs Phase B study, which began in December 2024 and will continue for one year, we present the development status of the Geant4 based simulator to accurately simulate the detectors response and initial results on the sensitivity of the instrument. Geant4 Monte Carlo simulation is used to assess the physical interactions of the source photons with the detector and the passive materials. We implemented a detailed CUSP Mass Model within Geant4 to simulate and estimate the instruments sensitivity, correcting the geometric effects of the instrument. We also evaluated the effect of backscattering shielding on the sensitivity to optimize the mass model of the instrument.

The Earth's earliest magnetic field may have originated in a basal magma ocean, a layer of silicate melt surround the core that could have persisted for billions of years. Recent studies show that the electrical conductivity of liquid with a bulk silicate Earth composition exceeds 10000 S/m at basal magma ocean conditions, potentially surprising the threshold for dynamo activity. Over most of its history however, the basal magma ocean is more enriched in iron than the bulk silicate Earth, due to iron's incompatibility in the mineral assemblages of the lower mantle. Using ab-initio molecular dynamics calculations, we examine how iron content affects the silicate dynamo hypothesis. We investigate how the electrical conductivity of silicate liquid changes with iron enrichment, at pressures and temperatures relevant for Earth's basal magma ocean. We also compute the electronic contribution to the thermal conductivity , to evaluate convective instability of basal magma oceans. Finally, we apply our results to model the thermal and magnetic evolution of Earth's basal magma ocean over time.

Despite many attempts, the origin of UV emission line and continuum in contact binary stars remains unclear. We present a substantial UV spectroscopic analysis of VW Cephei, a late-type contact binary system, using 46 low-resolution spectra from the International Ultraviolet Explorer (IUE) in the wavelength range 1150-1978 Å. By modelling continuum and emissions lines in individual spectra, we report the significant detection of OIII] (1660 and 1666 Å) and SiIV (1393 and 1402 Å) line complexes. We observe that UV fluxes for both continuum and emission lines like CIV, OIII], CII and SiIV vary significantly (fractional rms variability up to 45%) from hours to years. In addition, line widths also change by hundreds of kilometres/sec. The UV flux variabilities observed in the continuum bands and line emissions are uncorrelated. However, most of the flux values follow the binary orbital period observed from optical data. Our analysis indicates that, while the variation in continuum flux may be attributed to a heated photosphere, the line width measurements indicate that the emission lines are likely formed in the dynamical clouds associated with Roche lobe overflow. We estimate the mass transfer rate of $ \dot{M} = (0.82 \pm 0.01) \times 10^{-7} \ M_{\odot} {yr^{-1}}$ from UV line fluxes, which is in good agreement with optical studies.

Axion inflation is a well-motivated model of cosmic inflation with a rich phenomenology. The abundant production of gauge fields during axion inflation notably sources a stochastic gravitational-wave (GW) background signal, which nourishes the hope that future GW searches might have a chance to probe the model. In this paper, we scrutinize GW production during axion inflation in the gradient expansion formalism (GEF), a powerful numerical technique that captures the nonlinear dynamics of the system in the limit of vanishing axion gradients. We focus on axion inflation coupled to a pure Abelian gauge sector, i.e., pure axion inflation (PAI), and perform the first-ever comprehensive parameter scan of GW production in the Abelian PAI model close to the onset of strong backreaction. Remarkably enough, we find that GW signals within the reach of future GW interferometers can only be realized in parameter regions that also lead to strong backreaction and that are in conflict with the upper limit on $\Delta N_{\rm eff}$, i.e., the allowed energy density of dark radiation. This observation defines a clear target for future lattice studies of axion inflation that may confirm or improve the predictions of our GEF benchmark.

We aim to characterize the physical and activity properties of the interstellar comet 3I/ATLAS through spectroscopic and photometric observations during the first month after its discovery. We performed time-series photometry and long-slit spectroscopy between 2 and 29 July 2025 using multiple ground-based telescopes. Photometric data were calibrated against field stars from the ATLAS and APASS catalogs, and Fourier analysis was applied to derive the comet's rotational period. Spectral data were obtained using the SALT telescope and Nordic Optical Telescope. We report a spin period of $16.16 \pm 0.01$ h with a lightcurve amplitude of approximately 0.3 mag. The comet exhibits increasing dust activity and reddening colors during the observation period, with no visible tail detected, likely due to viewing geometry and low dust production. Dust mass loss rates are estimated between 0.3 and 4.2 kg s^-1, consistent with weakly active distant comets. Spectral colors are similar to those of outer Solar System comets and differ from previously reported values for 3I/ATLAS. The morphological and photometric properties of 3I/ATLAS are consistent with a weakly active comet of outer Solar System origin, despite its interstellar provenance. Continued monitoring around perihelion is necessary to track changes in activity, color, which will provide insights into the evolution of interstellar materials under solar radiation.

We present a catalog of 8545 and 19,257 unique DA white dwarfs observed in SDSS Data Release 19 and previous SDSS data releases, respectively. This is the largest catalog of both spectroscopic and photometric measurements of DA white dwarfs available to date, and we make this catalog and all code used to create it publicly available. We measure the apparent radial velocity, spectroscopic effective temperature and surface gravity, and photometric effective temperature and radius for all objects in our catalog. We validate our measurements against other published white dwarf catalogs. For apparent radial velocities, surface gravities, and effective temperatures measured from spectra with signal-to-noise ratios $>50$, our measurements agree with published SDSS white dwarf catalogs to within 7.5 km/s, 0.060 dex, and $2.4\%$, respectively. For radii and effective temperatures measured with Gaia photometry, our measurements agree with other published Gaia datasets to within $0.0005$ $R_\odot$ and $3\%$, respectively. We use this catalog to investigate systematic discrepancies between white dwarfs observed in SDSS-V and previous generations of SDSS. For objects observed in both SDSS-V and previous generations, we uncover systematic differences between measured spectroscopic parameters depending on which set of survey data is used. On average, the measured apparent radial velocity of a DA white dwarf is $11.5$ km/s larger and the surface gravity is $0.015$ dex smaller when a white dwarf's spectroscopic parameters are measured using SDSS-V data compared to using data from previous generations of SDSS. These differences may be due to changes in the wavelength solution across survey generations.

Dark matter in the form of macroscopic composites is largely unconstrained at masses of $\sim 10^{11}- 10^{17}$ g. In this mass range, dark matter may collide with planetary bodies, depositing an immense amount of energy and leaving dramatic surface features that remain detectable on geological timescales. In this paper, we show that Ganymede, the largest Jovian moon, provides a prime target to search for dark matter impacts due to its differentiated composition and Gyr-old surface. We study the effects of dark matter collisions with Ganymede first with analytic estimates, finding that in a large region of parameter space, dark matter punches through Ganymede's conductive ice sheet, liberating sub-surface material. This sub-surface material may be compositionally different from the surface ice, providing a key observable with which to discriminate asteroid impacts from those caused by dark matter. We confirm our analytic estimates with dedicated simulations of dark matter impacts using iSALE, a multi-material impact code. We then discuss potential detection prospects with two missions currently en route to the Jovian system, Europa Clipper and JUICE, finding that these missions may have the ability not only to identify signs of life on the Galilean moons, but signs of dark matter as well.

The mechanisms controlling the relative heating and energization of electrons and protons during magnetic reconnection are explored. Simulations are carried out with the kglobal model, which produces bulk heating and the extended powerlaw distributions of both species that have been documented in observations. The simulations have been carried out with a range of proton-to-electron mass ratios and upstream temperatures to isolate the factors that control energy gain. The simulations reveal that when the upstream temperatures of the two species are equal, the proton heating and energization exceeds that of electrons and that this is a consequence of the much larger energy gain of protons on their first entry into the reconnection exhaust. The effective energy gain of protons on exhaust entry scales as $m_iC_A^2$ since the protons counterstream at the Alfvén speed $C_A$ while the initial electron energy gain is smaller by the factor $(\beta_{e0}m_e/m_i)^{1/2}$. Since Fermi reflection during flux rope merger dominates energy gain in large-scale reconnecting systems and the rate of energy gain is proportional to energy, protons continue to gain energy faster than electrons for the duration of the simulations, leading to temperature increments of protons exceeding that of electrons and the non-thermal energy content of protons also exceeding that of electrons.

Measurement of eccentricity in low-mass binary systems through gravitational waves is crucial to distinguish between various formation channels. Detecting eccentricity in these systems is challenging due to a lack of accurate eccentric waveform models and the high computational cost of Bayesian inferences. We access the eccentricities of six previously observed low-mass gravitational wave events using publicly available data from the first four observing runs of the LIGO and Virgo collaboration. We analyze the events using the new eccentric waveform model, SEOBNRv5EHM, and compare our results with the existing model, TEOBResumS-Dali. We also present the first eccentricity constraints for GW190814. To improve accuracy, we include higher-order modes in both models and optimize inference using efficient marginalization and parallelization techniques. We find that GW200105 exhibits non-negligible eccentricity, with a measured eccentricity of $e=0.135^{+0.019}_{-0.088}$ at 20 Hz (90% credible level) for TEOBResumS-Dali and $e=0.125^{+0.029}_{-0.082}$ for SEOBNRv5EHM, given a uniform eccentricity prior from 0 to 0.2. This provides moderate support for the eccentric hypothesis, with a Bayes factor of $\sim10-15$ in favor of the eccentric model. With a uniform log prior on eccentricity, the Bayes factor is reduced to 2.35. The remaining five sources are consistent with low eccentricity, with 90% upper limits from $e \leq 0.011$ to $e \leq 0.066$. We find no support for non-negligible eccentricity in GW190814.

We investigate the implications of neutron star observations for understanding the origin of nucleon mass using a framework that combines three complementary approaches: the equation of state based on parity doublet structure for hadronic matter below $2n_0$, the Nambu-Jona-Lasinio (NJL) model for quark matter above $5n_0$, and a model-independent analysis of the intermediate density region based on fundamental physical principles. By systematically exploring parameter spaces and comparing theoretical predictions with recent observational constraints, we establish constraints on the chiral invariant mass. Our results suggest that more than a half of the nucleon mass originates from sources beyond spontaneous chiral symmetry breaking, challenging conventional understanding of nucleon mass generation. These constraints arise solely from fundamental physical principles and observational data, independent of specific assumptions about the nature of the quark-hadron transition, providing robust insights into the microscopic origin of hadron masses.

The post-inflationary production of supermassive particles can have profound implications for the thermal history of the universe and may leave observable imprints in the gravitational wave (GW) background. In scenarios where the inflaton couples predominantly to heavy fields, say right-handed neutrino (RHN), non-perturbative mechanisms such as parametric resonance can lead to their efficient production, even when their masses exceed the inflaton mass. Once produced, the RHNs emit gravitons through bremsstrahlung as they decay into the Standard Model (SM) particles via $N\rightarrow \ell + H$, enabled by the unavoidable minimal coupling to gravity, sourcing a stochastic GW background. We study this mechanism within the framework of $\alpha-$attractor inflationary models, highlighting how the resulting GW spectrum carries indirect imprints of the heavy sector and the post-inflationary dynamics. This offers an observational window into otherwise inaccessible supermassive particles and provides a powerful probe of high-scale physics beyond the SM.

The concept of inverse energy cascades has played a central role in the development of turbulence theory, with applications in two-dimensional and quasi-two-dimensional flows. We examine the presence or absence of inverse energy cascades in rotating stably stratified flows constrained to anisotropic yet fully three-dimensional domains, in a range of parameters that are relevant for planetary atmospheres. In particular, we focus on regimes with aspect ratios, Rossby, and Froude numbers similar to those found in the Earth's and other planets atmospheres. Our results show that, under certain conditions, inverse energy cascades can indeed emerge from the dry fluid dynamics solely, suggesting that this process can play a role in intermediate-scale atmospheric self-organization processes.

The detection of gravitational waves from extreme-mass-ratio inspirals (EMRIs) in space-borne antennas like LISA and Taiji promises deep insights into strong-field gravity and black hole astrophysics. However, the complex, non-convex likelihood landscapes of EMRI signals (compounded by instrumental noises) have long hindered reliable parameter estimation based on traditional Markov Chain Monte Carlo (MCMC) methods, which often fail to escape local optima or require impractical computational costs. To address this critical bottleneck, we introduce Flow-Matching Markov Chain Monte Carlo (FM-MCMC), a pioneering Bayesian framework that synergizes continuous normalizing flows (CNFs) with parallel tempering MCMC (PTMCMC). By leveraging CNFs to rapidly explore high-dimensional parameter spaces and PTMCMC for precise posterior sampling, FM-MCMC achieves unprecedented efficiency and accuracy in recovering EMRI intrinsic parameters. By enabling real-time, unbiased parameter inference, FM-MCMC unlocks the full scientific potential of EMRI observations, and would serve as a scalable pipeline for precision gravitational-wave astronomy.

We investigate the connection between thermodynamic phase transitions and quasi-normal modes (QNMs) in charged black holes with a positive curvature constant, within the framework of $F(R)$-Euler-Heisenberg gravity. Nonlinear electromagnetic fields lead to rich thermodynamic phase structures and significantly affect the QNMs of massless scalar fields. By analyzing the QNMs spectrum, we find that the transition point marking the disappearance of divergence in the QNMs slope parameter $K$ aligns with the change of the thermodynamic phase structure described by the heat capacity, within the bounds of computational uncertainty. This precise matching holds under variations of curvature parameters and charge. Furthermore, we show that larger angular quantum number $l$ diminishes this correspondence, while higher overtone number $n$ restores it beyond a threshold. These findings demonstrate that thermodynamic phase transitions of black holes carry embedded dynamical information, uncovering a fundamental link between black hole thermodynamic and dynamical properties.

By reentering into laser interferometers, scattered or stray light introduces non-linear noise. This is a major limitation of precision interferometers as preventing such parasitic light is nearly impossible. Thus, substantial effort is put into mitigating the reentering of these fields in various ways. Ground-based laser interferometric gravitational wave detectors employ such mitigation techniques to reduce otherwise restrictive stray light noise. However, they are now reaching sensitivities where conventional mitigation techniques reach limitations. Further improvements planed for future observatories are placing even more demanding constraints on tolerable stray light power. We previously presented tunable coherence as a possible technique to ease these constraints and suppress unwanted coherent interference. For these promising demonstrations, the remaining coherence length and achievable suppression in length-constrained layouts was limited, among other things, by the used pseudo-random-noise phase modulation frequency. In this work, we demonstrate stray light suppression and cavity performance at modulation frequencies up to 10 GHz. This reduces the remaining coherence to a few centimeter in an interferometer, and even to the scale of the laser wavelength in a cavity. We further present a first demonstration of tunable coherence in a power-recycled Michelson interferometer, successfully suppressing stray light in a more complex topology.

The future space-based gravitational wave observatories are expected to provide unprecedented opportunities to explore intricate characteristics of black hole binaries, particularly for extreme mass-ratio inspirals (EMRIs), in which a stellar-mass compact object slowly inspirals into a supermassive black hole. These systems are very prominent sources for testing gravity in the strong gravity fields and for probing potential deviations from general relativity, including those arising from the presence of fundamental scalar fields. In this work, we examine the impact of a scalar charge carried by the inspiraling object within the context of EMRIs. We focus on generic orbits that present both eccentricity and inclination to evaluate how these parameters affect the modifications induced by the scalar charge to the gravitational wave signal. Our results demonstrate that the inclusion of orbital inclination, in particular, enhances the detectability of scalar field effects by introducing richer waveform features that deviate from the purely general relativistic case. The interplay among scalar charge, eccentricity and inclination provides a more complete sampling of the black hole spacetime, suggesting that EMRIs with such generic orbits represent compelling systems for stringently constraining or discovering new fundamental fields through future gravitational wave observations.

We present new supernova (SN 1987A) cooling bounds on sub-MeV fermionic dark matter with effective couplings to electrons. These bounds probe the parameter space relevant for direct detection experiments in which dark matter can be absorbed by the target material, showing strong complementarity with indirect searches and constraints from dark matter overproduction. Crucially, our limits exclude the projected sensitivity regions of current and upcoming direct detection experiments. Since these conclusions are a priori not valid for light mediators, we extend our analysis to this case. We show that sub-GeV mediators can be produced resonantly both in supernova cores and in the early Universe, altering the SN 1987A analysis for effective couplings. Still, a combination of supernova cooling constraints and limits from dark matter overproduction excludes the entire parameter space relevant for direct detection in this case.