Papers for Wednesday, May 13 2026

We study the practical implementation of zero-order-hold (ZOH) transcriptions for spacecraft trajectory optimisation, identifying a set of design principles that render them robust across a broad class of dynamical settings without problem-specific tuning. The contributions are fourfold: (i) a thorough study of the forward--backward shooting construction, denoted $\mathrm{ZOH}_\alpha$; (ii) a redundant four-dimensional throttle parameterization that eliminates the singularity of the control influence matrix along ballistic arcs; (iii) a softmax time-grid encoding that avoids ordering constraints on segment durations while preserving full differentiability; and (iv) the TOPS benchmark (Trajectory Optimisation Problems in Space), a suite of 28 problems spanning four dynamical models, two-body Cartesian, modified equinoctial elements, circular restricted three-body, and solar sailing, designed to be extended over time.

The unexpectedly high abundance of bright, blue, super-early galaxies ($z\gtrsim10$) has challenged most pre-JWST models of early galaxy formation and motivated a wide range of proposed explanations. We systematically investigate whether galaxy clustering can discriminate among representative scenarios that reproduce the observed UV luminosity function. Using the Shin-Uchuu dark-matter-only simulation, we populate $z \approx 11$ halos with galaxies according to solutions based on i) attenuation-free, ii) feedback-free bursts, iii) bursty star formation, and iv) primordial black hole models. For each model, we compute the two-point correlation function and predict the galaxy bias for flux-limited samples at different thresholds in the $-20 < {\rm M_{UV}} < -16$ magnitude range. We find that all models predict similar bias values ($b \approx 7$) for faint galaxies (${\rm M_{UV}}\approx-16$), but diverge at ${\rm M_{UV}}\lesssim-18$, as the underlying halo-mass to ${\rm M_{UV}}$ relations differ significantly. In particular, the primordial black hole scenario predicts an almost luminosity-independent bias, whereas the other models generally predict increasing bias with luminosity, reaching $b \approx 14$ for ${\rm M_{UV}} \approx -19$. Current observational estimates of the bias cannot yet rule out any of the models at a significant statistical confidence. More precise measurements from future JWST programs, together with improved theoretical predictions, will be required to break the present degeneracies. Ideally, constraints from a complete sample of galaxies with ${\rm M_{UV}} < -18$ would probe the knee of the $b({\rm M_{UV}})$ function, taking advantage of the difference in model predictions and strengthening our analysis. Although requiring further refinement, galaxy clustering is confirmed to be a promising probe of the physical origin of the JWST high-redshift luminosity function.

The International Astronomical Union 2015 Resolution B2 (IAU2015GARB2) has resolved the long-standing problem of zero-point constants for the absolute and apparent bolometric magnitude scales and opened a new window in fundamental astrophysics. The empirical zero-point constants of the bolometric corrections, $C_2(\xi)$, and the absolute/apparent magnitudes, $C_\xi/c_\xi$, for the {\it Gaia} passbands were obtained from 88 {\it Gaia} XP spectra, and absolute bolometric/filtered magnitudes. The individual zero-point constants $\langle C_{\rm 2}\rangle$ of the bolometric corrections ($BC_\xi$) for each star revealed weighted averages of $\langle C_{\rm 2}(G)\rangle=0.8677\pm0.0109$ mag, $\langle C_{\rm 2}(G_{\rm BP})\rangle=1.0449\pm0.0116$ mag, and $\langle C_{\rm 2}(G_{\rm RP})\rangle=2.0510\pm0.0087$ mag. Furthermore, $C_{\rm Bol}=71.197425...$ mag and $c_{\rm Bol} =-18.997351...$mag announced by IAU2015GARB2, and using the definition of $C_{\rm 2}=C_{\rm Bol}-C_{\xi}=c_{\rm Bol}-c_{\xi}$, where the subscript $2$ indicate the wavelength ranges of two in which one is for bolometric and the other for one of the three filters, the zero-point constants of magnitudes for {\it Gaia} filters as $C_{\rm G}=70.1525\pm0.0109$ mag and $c_{\rm G}=-19.8651\pm0.0105$ mag, $C_{\rm G_{\rm BP}}=70.1525\pm0.0116$ mag and $c_{\rm G_{\rm BP}}=-20.0423\pm0.0116$ mag, and $C_{\rm G_{\rm RP}}=69.1464\pm0.0087$ mag and $c_{\rm G_{\rm RP}}=-21.0484\pm0.0087$ mag, if $L_{\xi}$ and $f_{\xi}$ are in SI units in case no extinctions. Lastly, spectroscopic $BC$s for {\it Gaia} magnitudes of 88 stars and the spectroscopic $BC-T_{\rm eff}$ relation for each {\it Gaia} filter are presented.

The standard theory of galaxy formation predicts that all galaxies should contain dark matter, yet a handful of recently discovered galaxies appear to lack it, challenging our understanding of galaxy formation. We investigate whether such dark-matter deficient objects can be identified from their baryonic properties alone, analogously to the radial-acceleration relation, which tightly links baryon and dark matter distributions in spiral galaxies. Using a sample of ultra-diffuse and dwarf spheroidal galaxies -- systems whose baryonic properties resemble those of the confirmed dark-matter-deficient galaxies -- we systematically search for a formula to predict baryonic fractions from stellar mass, effective radius, distance to the host, and the host's baryonic mass. We find that baryonic fraction correlates most strongly with the gravitational acceleration expected from baryons alone, $a_\mathrm{bar}$, or equivalently, with mean surface brightness, following an approximately $a_\mathrm{bar}^{-1}$ dependence. This scaling resembles the radial-acceleration relation but differs in functional form and applies to a different galaxy population. Strikingly, the dark-matter-deficient galaxies occupy the extreme end of the correlation. This suggests that they result from standard formation processes operating at unusual intensities rather than from exotic mechanisms. Importantly, the correlation predicts that all ultra-diffuse galaxies brighter than approximately 25 mag arcsec$^{-2}$ in the $g$-band should have very low dark matter content, offering a straightforward observational criterion for identifying these rare objects.

Observational abundances of CEMP stars with patterns in between those produced by the rapid and slow nucleosynthesis processes (CEMP-rs stars) are currently invoked as evidence of synthesis via the intermediate process in the early AGB evolutionary phase of metal-poor low mass stars. Nevertheless, discriminating between r+s- and i-process hypotheses requires high-precision abundances obtained through advanced spectral modelling techniques. Theoretical models of the i-process have become more robust, incorporating refined stellar modelling and nuclear reaction physics, providing ranges of probable elemental abundances and isotopic ratios predictions to be confronted with observational determinations. We performed a new analysis of a high resolution and high S/N UVES spectrum of TYC 6044-714-1. We derived accurate effective temperature and highly precise atmospheric parameters, element abundances, and isotopic ratios using state-of-the-art 1D non-LTE and 3D non-LTE spectral line modelling. Using the latest AGB nucleosynthesis models, we assessed the possibility of the i-process to act aside the s-process. We find that TYC~6044-714-1 was likely born as a normal in-situ halo star about 13 Gyr ago, pre-enriched by the r-process through a standard Galactic chemical-evolution pathway. The s+r model provides the best overall reproduction of the observed heavy-element abundance pattern and Ba isotopic ratios, yielding excellent agreement across all three s-process peaks. While i+s+r models with increasing overshooting efficiency improve the fit for specific elements, they do not consistently reproduce the full abundance pattern. The i+s+r models require extreme and physically implausible conditions, and predict s-process Ba fractions inconsistent with those inferred from isotopic ratios of the 4934 Å resonance line. We conclude that the pure s+r scenario is the most plausible explanation.

We present a uniform spectroscopic characterization of 625 F, G, and K stars hosting 859 confirmed exoplanets using high-resolution archival optical spectra from the Tillinghast Reflector Echelle Spectrograph (TRES). We use the neural network spectral code uberMS, which combines spectra with broadband photometry to estimate precise and accurate stellar parameters. We determine stellar effective temperatures, surface gravities, radii, luminosities, projected rotational velocities, [Fe/H] abundances, and [$\alpha$/Fe] enrichments for most confirmed planet hosts observed by TRES. This uniform catalog can be used for a broad range of astrophysical studies, particularly to explore links between stellar [$\alpha$/Fe] and a suite of observed exoplanet properties. Combining our metallicity measurements with galactic kinematics, we identify 58 planet hosts that are likely members of the thick disk. We investigate the chemical environments of giant-planet formation by comparing the [$\alpha$/Fe] distributions of giant-planet host stars across different metallicity regimes. We find that subsolar metallicity giant-planet hosts are significantly enhanced in [$\alpha$/Fe] relative to Fe-rich giant-planet hosts and to the average Fe-poor field star, at high statistical significance. This suggests that enhanced $\alpha$-element abundances may partially compensate for low-Fe content and thus enable the formation of giant planets in metal-poor environments. We additionally compare the [$\alpha$/Fe] distributions of single- and multi-planet hosts and find modest evidence that $\alpha$-enhanced stars may preferentially host multi-planet systems. Finally, we recover previously observed trends between stellar metallicity and planetary eccentricity.

We present a framework for inferring the dark matter halo masses of quasars and [O III]-emitting galaxies from JWST/NIRCam Wide Field Slitless Spectroscopy (WFSS) clustering measurements at z approximately 6. Using the FLAMINGO-10k N-body simulation, we construct mock realizations of quasar and galaxy catalogs that incorporate realistic selection functions, spatial coverage, and sensitivity limits matched to the ASPIRE survey. These mocks enable accurate measurements of the quasar-galaxy cross-correlation and galaxy auto-correlation functions, with covariance matrices derived from 1000 realizations that capture both cosmic variance and bin-to-bin correlations. We employ Bayesian inference to fit the correlation functions and infer the minimum halo masses for quasars and galaxies. Our results demonstrate that Poisson pair-count uncertainties, commonly adopted in high-redshift clustering studies, significantly underestimate the true measurement errors. The dominant missing component is cosmic variance: even the diagonal of the full covariance matrix exceeds the Poisson expectation, with off-diagonal bin-to-bin correlations contributing a smaller additional correction. In particular, 1) the commonly used Poisson error on the correlation functions underestimates the true uncertainty by a factor of approximately 3; 2) the uncertainties on the inferred minimum halo masses are underestimated by a factor of approximately 1.5-3 when adopting Poisson errors instead of the full covariance matrix; 3) the inferred QSO halo mass is robust to whether central and satellite [O III]-emitters share a common mass threshold. Our framework provides a more complete error budget for JWST/WFSS clustering analyses, enabling robust constraints on the host halo masses and duty cycles of high-redshift quasars and emission-line galaxies.

We constrain uncorrelated primordial isocurvature perturbations using a combination of large- and small-scale cosmological probes, with the small-scale data provided by the ultraviolet luminosity function (UVLF) -- a measure of number density of galaxies as a function of UV brightness. We consider several isocurvature modes, including cold dark matter, baryon, neutrino density, neutrino velocity, and dark radiation perturbations. The isocurvature power spectrum is modeled using two independent parameterizations: a broken power law and a running power law, without fixing the spectral index a priori. Our analysis combines large-scale data from the Cosmic Microwave Background (CMB), baryon acoustic oscillations, and Type Ia supernovae with small-scale constraints from UVLF measurements obtained by \textit{HST} and \textit{JWST}. The UVLF probes matter fluctuations over a continuous range of intermediate scales, $k \sim 0.5$--$10~\mathrm{Mpc}^{-1}$ over a wide range of redshift $4\lesssim z \lesssim 13$, providing a direct handle on structure formation in a regime where constraints on the scale dependence of isocurvature perturbations remain comparatively limited. Our result represents the first UVLF-based constraint on model-agnostic isocurvature perturbations carried by various components. We construct $68\%$ and $95\%$ credible envelopes in $k$-space for the allowed isocurvature power and find good agreement between the envelopes for the $95\%$ envelope across a wide range of scales, indicating that our constraints are mostly insensitive to the assumed power-law form.

The cross-correlation between tracers of large-scale structure, such as galaxies or quasars, and the thermal Sunyaev-Zel'dovich (tSZ) signal yields a measure of the bias-weighted mean electron pressure, $\langle b_\mathrm{h} P_\mathrm{e} \rangle$, where $b_\mathrm{h}$ is the halo bias and $P_\mathrm{e}$ is the electron pressure. With a model for the bias, one can derive the thermal history, $\mathrm{d}y/\mathrm{d}z$, where $y$ is the Compton parameter and $z$ is redshift. We explore how these quantities depend on redshift, cosmology, and the physics of galaxy formation using the \flamingo\ suite of cosmological hydrodynamical simulations, which spans a range of cosmological parameters and baryonic feedback implementations in volumes of up to $(2.8\,\text{Gpc})^3$. We find that $\langle b_\mathrm{h} P_\mathrm{e} \rangle$ depends steeply on $S_8 \equiv \sigma_8\sqrt{\Omega_\mathrm{m}/0.3}$, with an effective scaling $\langle b_\mathrm{h} P_\mathrm{e} \rangle \propto S_8^{\epsilon(z)}$, where the exponent $\epsilon(z) \approx 3$ over the redshift range $0.1 \leq z \leq 1$. Compared with existing cross-correlation measurements using tracer samples from SDSS, BOSS, eBOSS, DES, and DESI cross-correlated with tSZ measurements from Planck, we find that models with a low-$S_8$ cosmology and strong feedback are preferred, with a joint fit yielding $S_8 = 0.72^{+0.03}_{-0.03}$ and a normalised group-mass halo baryon fraction $f_b(10^{13}\,M_\odot, z=0.1)/(\Omega_b/\Omega_m) = 0.10^{+0.09}_{-0.05}$ . Contrary to most probes of feedback which sample smaller scales (e.g., X-ray measurements), we show that feedback boosts $\langle b_\mathrm{h} P_\mathrm{e} \rangle$, thus providing a novel test of feedback models. Overall, our results show the thermal history provides a route to jointly constrain cosmological parameters and test models of galaxy formation.

As part of the ongoing work of the $R$-Process Alliance (RPA), detailed abundance measurements of 29 heavy elements in three metal-poor stars, 2MASS J14592981$-$3852558, 2MASS J19445483$-$4039459, and 2MASS J15211026$-$0607566, are presented based on an analysis of high-resolution ($R\sim 80,000$), high signal-to-noise ``portrait'' spectra from the Magellan Inamori Kyocera Echelle (MIKE) spectrograph on the Magellan-Clay Telescope at Las Campanas Observatory. The selected targets were identified as $r$-process-enhanced metal-poor stars in previous RPA snapshot analyses. They have also been linked to possible chemodynamically tagged groups, indicating that the stars may have formed in dwarf galaxies that were later accreted into the Milky Way halo. These stars have also been tentatively linked to the Thamnos structure. The detailed chemical abundances in this work confirm that 2MASS J14592981$-$3852558 and J15211026$-$0607566 are $r$-II stars, while 2MASS J19445483$-$4039459 is found to lie just below the threshold for $r$-I status. The $r$-II stars show signs of slight enhancement in fission fragments compared to 2MASS J19445483$-$4039459. Based on radioactive age dating with Th, the $r$-process material in the two $r$-II stars is found to be old (with ages $>10$ Gyr); neither star shows signs of an actinide boost. The varying elemental compositions suggest that these stars likely did not originate in the same environment, though each could be consistent with originating in the Thamnos progenitor.

Venus and Earth are similar in bulk properties yet followed dramatically different climatic trajectories. Reconstructing Venus's climate evolution requires understanding how rotation, obliquity, eccentricity, and solar luminosity shaped incident energy and the atmospheric response. Here we present latitude-orbital phase maps of incident solar flux for Venus at the present epoch and at an age of 0.5 Gyr, when the Sun was fainter and Venus may have occupied a different dynamical state. We explore slow- and fast-rotator regimes, moderate obliquity (10deg), and elevated eccentricity (e=0.15-0.30), motivated by dynamical studies of plausible limits. To translate flux maps into climate-relevant quantities, we apply an idealized atmospheric energy-balance framework with global (0-D) and latitude-dependent (1-D) formulations calibrated to modern Venus. This framework defines a radiative relaxation timescale that links forcing variability to thermal response. The resulting diagnostics connect orbital forcing to surface energy balance and assess seasonal and orbital variability relative to Venus's extreme greenhouse state. Our results show that early Venus could experience substantial redistribution of insolation across latitude and orbital phase, but orbit-averaged incident flux varies only modestly across the explored parameter space, leaving atmospheric opacity as the dominant control on surface temperature. Insolation variations therefore act mainly as modulators rather than primary drivers of climate state, with their expression governed by the competition between forcing and radiative adjustment timescales. The insolation maps and response diagnostics provide boundary conditions for future 3-D climate simulations of early Venus, including regimes in which temperate surface conditions may have been sustained.

Lensed supernovae (SNae) are among the most eagerly anticipated transients expected from the Legacy Survey of Space and Time (LSST). Quadruply lensed SNae permit more highly constrained models than "mere" doubles. The quadruply lensed SN 2025wny offers multiple lessons on how one might respond to an alert. The full benefits of such rare events are best achieved with immediate spectroscopic and photometric followup, within hours rather than days. This in turn requires on-the-fly modeling to predict the position(s) and magnitudes of trailing images and to "pre-cover" any leading images that might have been too faint to trigger an alert and that cannot be detected in the triggering exposure. This paper sets out a proposed protocol for exploiting similar alerts. A list of quadruply lensed candidate hosts must first be supplied in advance to one or more brokers, along with on-the-fly software (an example of which is given) to determine whether an SN near an incipient host is strongly lensed, and whether quadruply or doubly. The brokers would then broadcast the positions and time delays (or "pre-lays") that permit "pre-covery'' of leading images, "re-covery'' of trailing images, and possibly, extraction of a rough lightcurve from prior LSST exposures. The scheme is illustrated (and some potential problems identified) using preliminary data for SN 2025wny presented by three independent teams. It employs software based on the geometric Witt-Wynne lens model and Falor's exact, forward, differentiable solution thereof.

An important open question in exoplanet studies is whether planets leave detectable chemical fingerprints on their host stars. While several studies have suggested possible planetary chemical signatures in planet-hosting stars, their origin remains debated because of stellar birth conditions and evolutionary effects. Wide binaries, whose components share a common formation environment, provide an ideal testbed for identifying planetary signatures. Such signatures are often characterized by differential abundance trends with condensation temperature (Tc), which traces the partitioning between gaseous and rocky planetary material. We investigate whether these trends are associated with planetary architectures in wide binaries. We obtained high-resolution NIR spectra of four planet-hosting wide binaries. We measured abundances for both components and analyzed differential abundances in each system. We also compiled literature measurements for planet-hosting and non-hosting wide binaries and compared their Tc trends. WASP-160 A/B and WASP-127/TYC 4916-897-1 exhibit significant abundance trends with Tc, while HD 20782/HD 20781 shows a weaker correlation and K2-54/K2-54 B is consistent with a flat relation. The trends are diverse, including both volatile- and refractory-enhanced patterns in planet-hosting stars. Literature comparisons indicate that extreme Tc slopes may occur more frequently among planet-hosting wide binaries, particularly at large separations, although the statistics remain limited by sample size and definition. Our results indicate that chemical signatures in planet-hosting wide binaries are not universal but vary across systems. While planetary architectures may be associated with some host-star abundance patterns, multiple processes are likely to contribute. Larger samples are essential for disentangling planetary signatures from stellar and binary effects.

We present the Survey Footprint Explorer (v2.5.0), a browser-based interactive tool for visualising and comparing the sky footprints of major astronomical imaging surveys. The tool is implemented entirely in client-side JavaScript and requires no server infrastructure, making it immediately accessible from any modern web browser. Thirteen survey footprints are currently included: Euclid DR1, LSST Wide-Fast-Deep, the Nancy Grace Roman HLWAS and HLTDS (full and deep tiers), DESI Legacy Imaging Survey DR9, the Dark Energy Survey (DES), the Subaru Hyper Suprime-Cam survey (HSC), the Kilo-Degree Survey (KiDS), the Ultraviolet Near-Infrared Optical Northern Survey (UNIONS), the eROSITA All-Sky Survey (eRASS1), and the Atacama Cosmology Telescope Legacy (ACT) survey spanning wavelengths from X-ray to near-infrared and covering footprints from 7.7 deg$^{2}$ to 21,524.4 deg$^{2}$. Survey footprints are encoded as Multi-Order Coverage (MOC) maps and rendered via two complementary views: an interactive globe powered by Aladin Lite v2, and a full-sky equirectangular projection. All MOC intersection calculations, including multi-survey overlap area computation and per-source membership testing, are performed client-side. Users may upload source catalogues in CSV or TSV format and download an augmented version with boolean survey membership columns appended. The link to access the tool is provided at the end of the Summary section.

We present a radio continuum study of photometrically selected cosmic noon (0.5<z<3) post-starburst galaxies (PSBs) in the UKIDSS Deep Survey (UDS) field to assess if radio-mode Active Galactic Nuclei (AGN) are linked to the quenching of star formation at cosmic noon. Our cross-matching using the deep Very Large Array (VLA) imaging at 1.4 GHz results in a mean radio detection fraction ($f_{det}$) of only 0.8$\%$ for PSBs above a radio luminosity threshold of $L_{\rm 1.4 GHz} \geq 10^{24}$ W Hz$^{-1}$, increasing to 5$\pm2\%$ for massive PSBs with stellar masses M$_*>10^{11}$M$_\odot$. Massive PSBs have a comparable detection fraction to that of massive quiescent galaxies ($f_{det}=8\pm1\%$), and both classes have lower fractions than that of massive star-forming galaxies ($f_{det}=13\pm1\%$) in the same field. The radio luminosities of detected PSBs, ${\rm L}_{1.4}\sim 10^{22.8}-10^{24.9}$W/Hz, exceed those from star formation by a median factor of 37 indicative of a possible AGN origin. Their compact morphologies ($\lesssim15$ kpc at $z_{med}=1.5$) suggest low-luminosity AGN with less powerful jets. Stacking the undetected PSBs reveals a weak radio detection ($3.9\sigma$) in the highest mass bin (M$_*>10^{11}$M$_\odot$). In contrast, 1.4 GHz detected quiescent galaxies have radio luminosities reaching radio-loud levels, and a higher prevalence of extended morphologies indicative of large-scale jetted AGN. The AGN contribution is also detected in stacked measurements of quiescent galaxies. Overall, our results support a short radio AGN duty cycle for PSBs, characterized by weak radio jets, suggesting radio-driven maintenance mode feedback may become important at older ages.

In this study, we report partly simultaneous XMM-Newton and NuSTAR observations of the bursting, dipping low mass X-ray binary, 4U 1323-62 obtained in 2024. 4U 1323-62 is one of the well-known persistent bursters, with bursts occurring roughly every three hours. It is also one of the few sources for which the orbital period is known, and shows dips in X-rays. In this paper, we report the detection of 12 unique bursts with XMM-Newton and NuSTAR, 6 of them observed jointly. We detected two double burst events, one with the NuSTAR and another one observed with both missions. Based on the long-term behavior of 4U 1323-62, we unveil a cyclic trend in its burst rate, with a period of about 10 years. During our observations we detected 10 X-ray dips with a periodicity of 2.942 hours, in line with previous measurements. We also present the results of the time resolved X-ray spectral analysis of the bursts and show the limits on the cooling of the corona heated by the burst emission. We also found a 0.898 +/- 0.017 Hz quasi-periodic oscillation (QPO) during the non-bursting and non-dipping times confirming previous detections.

Ross~318 is an M3.5V red dwarf exhibiting significant magnetic activity and a stellar rotation period of $\sim51.5$\,d. In this work we present a systematic re-analysis of radial velocities (RV) from CARMENES and decade-long HIRES observations, integrated with TESS space-based photometry. We identify a terrestrial-mass planet, Ross~318\,b, with an orbital period $P = (39.6299 \pm 0.29)$\,d and a minimum mass $M\sin i = (6.21 \pm 0.62)M_{\oplus}$. The dynamical nature of the signal is confirmed by its temporal coherence over a 15-year baseline and its achromaticity between visible and near-infrared channels. TESS photometry from Sectors 18, 19, 24, and 25 (218.6\,d total baseline, 66\,983 cadences) reveals no transit at $P = 39.63$\,d (FAP $> 10\%$, BLS). An injection-and-recovery test demonstrates that a $2200$\,ppm transit signal corresponding to a $1.74R_{\oplus}$ body would have been detected with Signal-to-Pink-Noise Ratio SPNR $> 12$, ruling out a transiting geometry with high confidence. The orbital inclination is constrained to $i < 88.5^\circ$. With an incident stellar flux $S_{eff} \approx 0.58\,S_\oplus$ and bolometric luminosity $L_* = (0.01478 \pm 0.00122)L_{\odot}$, Ross~318\,b falls within the Conservative Habitable Zone, making it one of the most interesting temperate Super-Earths orbiting an M-dwarf.

51 Pegasi harbors the first confirmed extrasolar planet orbiting a Sun-like star. Decades of continued radial velocity (RV) observations have since uncovered signatures of an additional distant companion in the system from a shallow radial acceleration. We present new constraints on the mass and separation of a potential outer companion based on a synthesis of RVs, absolute astrometry, and new high-contrast imaging. Our analysis combines 31 years of new and previously published RV measurements from the OHP/ELODIE, Lick/Hamilton, Keck/HIRES, and APF/Levy spectrographs; a $\sim$25-year baseline of absolute astrometry from Hipparcos and Gaia; and deep imaging from Keck/NIRC2 and HST/WFPC2. We find evidence for curvature in the RVs, which when combined with non-detections from imaging and astrometry point to a super-Jupiter at $\simeq$15--100 AU or brown dwarf companion at $\approx$20--170 AU. However, the inferred radial acceleration of the host star is driven primarily by the Lick/Hamilton dataset and its slope is consistent with long-term instrument drift, calling into question the nature of the long-period signal. If an outer companion is present, it could explain the origin of the inner hot Jupiter if 51 Peg b arrived at its current location through high-eccentricity migration. On the other hand, if the signal is spurious, the exceptional baseline rules out Jovian planets within $\sim$10 AU and most brown dwarfs within several tens of AU, implying that the system is devoid of massive companions. Continued RV and astrometric monitoring together with high-contrast imaging can be used to distinguish these scenarios.

Modern astrophysical studies rely heavily on complex data analysis pipelines; however, published descriptions often lack the detail required for computational reproducibility. In this work, we present an information-theoretic framework to quantify how effectively a method can be reconstructed from its written description. By treating algorithmic reconstruction as a probability distribution generated by Large Language Models (LLMs), we utilize Shannon entropy and Jensen-Shannon divergence to measure how strongly text constrains the hypothesis space of valid implementations. We demonstrate this approach through a case study of Trans-Neptunian Object (TNO) spectral reconstruction from sparse photometry. By prompting frontier LLMs with varying levels of manuscript text (Title, Abstract, and Methods), we find that while increasing text successfully clarifies the overall algorithmic structure, it fails to eliminate variance at the implementation level. This persistent variance establishes an "entropy floor," demonstrating that multiple divergent implementations remain consistent with explicit instructions. To evaluate practical reproducibility, we convert these reconstructed algorithms into executable pipelines. Our results reveal that, while LLMs easily recover core functional methodologies, they systematically fail to infer the tacit expert knowledge required for strict scientific calibration. This pilot study demonstrates that LLMs can be repurposed as a zero-shot diagnostic tool to audit methodological transparency, helping authors identify missing structural constraints and preserve scientific integrity in an era of automated research.

We present a neural-network-based data processing pipeline for Baikal-GVD, designed to improve event reconstruction quality and accelerate neutrino candidates selection. The pipeline comprises three stages: fast suppression of extensive air shower events, suppression of noise optical modules activations, and extraction of high confidence neutrino candidates. All three networks employ a transformer architecture that exploits inter-hit correlations through the attention mechanism. Applied sequentially, the pipeline achieves orders-of-magnitude speedup over the standard reconstruction chain. Moreover, noise suppression neural network surpasses the accuracy of algorithmic noise suppression algorithms and provides estimate for time residuals of the signal hits, which is crucial for identification of track-like hits. We address the domain shift between Monte Carlo simulations and experimental data by incorporating a domain adaptation technique, demonstrating improved agreement between the two domains. The resulting framework enables near-real-time event classification, with direct applications to multi-messenger alert systems and diffuse neutrino flux measurements.

An update of the evidence that radio galaxies and clusters of galaxies are more common than average near the plane of the de Vaucouleurs Local Supercluster shows that in the distance range 100 to 200Mpc objects whose positions are correlated with the plane of the Local Supercluster include galaxies that are exceptionally luminous at two microns, radio galaxies, and clusters of galaxies. There can be little doubt about this property of cosmic structure. I also argue for detection of this correlation for the galaxies at 400Mpc distance that are exceptionally luminous at two microns. It will be interesting to learn whether these results are expected in the standard cosmology.

We present new empirically grounded forecasts for the detectability of the stochastic gravitational-wave background anisotropies assuming a population of stellar-mass compact binary coalescences as its source. We quantified the discovery potential using simulations based on the Euclid Flagship Galaxy Catalogue and LIGO-Virgo-KAGRA observational constraints in combination with detailed theoretical modelling. We considered the multi-messenger cross-correlation with galaxies as well as the gravitational wave-only cross-correlation across observation-time bins. For compact binaries up to redshift $z<3$, we found that an angular resolution of $\theta = 4.1$ deg ($\ell \geq 44$) is required for discovery within five years of observation via cross-correlation with a galaxy catalogue that is complete up to limiting magnitude $i < 24.7$ and has redshift uncertainties $\sigma_z = 0.003 (1+z)$. Extending the time range to ten years alleviates that requirement to $\theta = 6.5$ deg ($\ell \geq 28$). We also showed that binning the galaxies in redshift allows us to reconstruct the evolution of the kernel, which can be used to further constrain compact binary population models. Discovery without a multi-messenger tracer has proven significantly more challenging, requiring exclusion of the loudest events, $\theta = 1.8$ deg ($\ell \geq 95$), and a favourable coalescence rate. In light of the plans being carried out in the community for ongoing and upcoming galaxy surveys, this work bodes well for the multi-messenger discovery and exploration of the stochastic gravitational-wave background in the era of next-generation observatories such as the Einstein Telescope and Cosmic Explorer.

The JAGB method has been proposed in recent years as a possible distance indicator for galaxies in the Local Group and beyond. However, the nature of the stars populating the J region, and the conditions required for the direct application of this method, still need to be clarified. We investigate the robustness of the JAGB method through a detailed theoretical analysis of the stars populating the J region of the (J-Ks, J) diagram. The main goal is to identify the properties of the corresponding J luminosity function (JLF) that are minimally affected by the previous evolutionary history of the host galaxy, particularly its metal enrichment history. We use a population synthesis approach based on AGB stellar evolution models coupled consistently with dust formation in the stellar wind. Synthetic stellar distributions in the (J-Ks, J) diagram and the related JLFs are calculated for different assumptions on the metallicity evolution of the interstellar medium, in order to study how the JLF depends on the efficiency of metal enrichment. We find that the JAGB population is dominated by stars formed between about 1 and 6 Gyr ago, while stars formed outside this interval contribute only marginally to the JAGB region. The shape of the JLF strongly depends on the metal enrichment history, and the position of the J-band peak varies by more than 0.3 mag among the different cases explored. Conversely, the mean J-band magnitude, MavJ, is much less sensitive to the previous history of the galaxy and therefore represents a more reliable distance indicator. For all the cases investigated we find MavJ = -6.2 +/- 0.05 mag. We also discuss the uncertainties related to the still poorly constrained mass-loss process experienced by low-mass stars during the red giant branch phase.

M71 is a nearby, metal-rich globular cluster at low Galactic latitude, where field contamination and spatially variable extinction complicate colour-magnitude diagrams (CMDs) and the identification of cluster member variable stars. Our aims are (i) to construct a homogeneous census of variable stars in M71 by refining their periods and classifications and identifying new candidates, and (ii) to derive a decontaminated, differentially dereddened CMD to constrain its physical properties. We obtained Johnson-Kron-Cousins $VI$ time-series CCD photometry and reduced it using difference image analysis. Cluster membership was established from \textit{Gaia}~DR3 proper motions, and a differential-reddening correction was applied across the field of view. The resulting CMD, cleaned of field stars, was compared with tailored isochrones to estimate age ($12.9^{+0.9}_{-0.8}$ Gyr), metallicity ([Fe/H] =$-0.88^{+0.13}_{-0.15}$), mean reddening ($E(B-V)$ = $0.21 \pm 0.02$), and distance modulus ($(m-M)_{0}$ = $13.01 \pm 0.06$). Variable stars were identified using two complementary approaches: a periodogram-free string-length scan refined with phase dispersion minimisation, and a robust inter-site screening based on median statistics combined with a generalised Lomb-Scargle significance criterion. We identified 21 variable stars not previously reported in the Catalog of Variable Stars in Globular Clusters and provided their periods, amplitudes, classifications, membership status, and light curves. This combined strategy yields a consistent picture of M71, expanding its known variable-star population and confirming parameters typical of metal-rich Galactic disk globular clusters.

The Laser Interferometer Lunar Antenna (LILA) is a proposed gravitational-wave project aiming to take full advantage of the Moon's environment to access the deci-Hz band and detect intermediate-mass black hole (IMBH) binaries of mass $\sim 10^2-10^6 \, M_{\odot}$ (arXiv:2508.11631). With an observational period of 4 years, LILA can extend its IMBH detection horizon to the very early Universe, directly probing the first population of massive black holes ($z \sim 20-30$). LILA could also detect intermediate-mass-ratio inspiral systems with a total mass of $\sim 10^4 - 10^6 \, M_{\odot}$ and a mass ratio of $\sim 10^{-4} - 10^{-2}$. LILA can discover IMBH binaries months to years before merger with measurable eccentricity residuals retained from their formation, providing crucial early warning for multi-messenger and multi-band follow-up. The high SNR ($\gtrsim 100$) events detectable with LILA would enable strong-field tests of gravity. With these capabilities, LILA will provide important insights into the formation and evolution of massive black holes, as well as the astrophysical environments and evolutionary pathways of black hole binaries. LILA will also complement current LIGO/Virgo/KAGRA detections of pair-instability mass gap events, hierarchical merger candidates, and light IMBH mergers, while expanding the upper envelope of discovered black holes with stellar origin to masses of $\gtrsim 250 \, M_{\odot}$.

We present the optical design of OPTICAM-ARG, a multi-channel instrument for the simultaneous acquisition of images in three spectral bands at the Cassegrain focus of an f/8.5 telescope, covering the 0.35 to 1.00 um wavelength range. The converging beam delivered by the telescope is spectrally separated by two dichroics into three channels, blue, green, and red, each incorporating a dedicated three-lens focal reducer, an interchangeable SDSS filter stage, and an sCMOS detector. The focal reducers establish an effective focal length of approximately 9.1 m, a uniform plate scale of 22.6 arcsec/mm, and a field of view of 8.4 arcmin x 8.4 arcmin per channel, consistent with the typical seeing conditions at the site. Operation of the dichroics in a converging beam introduces off-axis aberrations, which are mitigated through wedge angles applied to their second surface and optimized as part of the global design. Optical performance is assessed through exact ray tracing using RMS spot radii and encircled energy metrics, with EE50 values further expressed in terms of an equivalent FWHM to enable direct comparison with atmospheric seeing and to evaluate sensitivity to manufacturing tolerances.

Most stars host short-period planets that are expected to be engulfed during post-main-sequence expansion. The dissolution of engulfed planets has been proposed as a possible mechanism for producing stars enriched in lithium and refractory elements. We perform three-dimensional hydrodynamical simulations of a Jupiter-like planet engulfed within a stellar envelope using the Seven-League Hydro code. Unlike previous studies that represent the planet as a point mass or rigid sphere, we adopt a wind-tunnel setup that resolves the planet's gaseous structure. We find that a continuous mass-ablation process operates during planetary engulfment, contrary to the common assumption that destruction occurs at a specific depth due to ram pressure, tidal forces, or thermal evaporation. The ablation rate scales nearly linearly with the wind momentum flux and is largely insensitive to the Mach number, consistent with an analytical model based on Kelvin-Helmholtz instability developing at the planetary surface. We define efficiency coefficients for drag and ablation, finding pressure-drag coefficients of 0.44-0.56 and smaller ablation efficiencies of 0.054-0.11. Applying these coefficients to a numerically integrated inspiral through a stellar profile, we find that continuous ablation could lead to complete dissolution of the planet within the convective envelope, producing observable lithium enrichment at the stellar surface. Our results provide prescriptions for drag and mass loss that enable large parameter-space studies of planetary engulfment and suggest that chemical enrichment may occur over a broader range of stellar parameters than previously thought.

Low-angular-momentum, axisymmetric, inviscid accretion flows onto a black hole have been studied using the vertical equilibrium disc model, considering multiple pseudo-Schwarzschild potentials and two thermodynamic equations of state. A multi-component galactic potential-representing stellar, dark matter, and hot-gas contributions-is incorporated to assess environmental effects on the accretion dynamics. In our earlier work, it is found that the effect of multi-component galactic potential on the accretion flow onto a rotating black hole under similar framework of analysis, significantly varies over different standard disc models, being most pronounced in the vertical equilibrium (VE) disc model. Thus it may be interesting to find whether such variation occur for different choices of pseudo potentials too. To begin with, in this work we consider accretion flow onto a non-rotating blackhole with VE geometry. Through the analysis of transonic behaviour and eigenvalue-based critical point classification, we demonstrate that, for all selected black hole potentials, the galactic potential profoundly influences the locations of critical points, the shock-allowed parameter space, shock-location, shock-driven flow variables, and acoustic surface gravity.

The internal dust attenuation of the Hii region reduces the observed emission-line fluxes. Turbulent density fields within each Hii region change the degree of the line-of-the-sight obscuration of the emission-line fluxes. In this paper, we implement the dust Monte-Carlo radiative transfer in the latest M3D code, creating the emission-line maps attenuated by the internal turbulent dust obscuration with the varying Mach numbers. The internal density and temperature fluctuations of Hii regions make the radiative transfer of hydrogen lines neither Case A nor Case B conditions, resulting in the global H{\alpha} to H\b{eta} ratio of approximately 3.02-3.03, differing from the widely-used value of 2.86. This deviation from Case B is because the temperature of these Hii regions is cooler than 10,000 K. We further derive the internal nebular attenuation curve from the attenuated Hydrogen lines, finding that the clumpy structures within Hii regions do not change the slope of the internal attenuation curve. This is because the heavy dust obscuration of dense clumps is canceled out by the high in-situ production of emission-line intensities.

Identifying universal, topology-independent thresholds in the coronal magnetic fields at onset of solar eruptions is crucial for physics-based prediction of eruptions. To this end, we systematically analyze the evolution of magnetic energy and helicity in twelve high-fidelity 3D magnetohydrodynamic simulations where eruptions are triggered by magnetic reconnection. The simulations encompass a comprehensive parameter space, including bipolar and quadrupolar configurations, sheared arcades and pre-existing flux ropes, and various photospheric driving motions. We find that the ratio of current-carrying helicity to total relative helicity $(H_j/H_r)$ exhibits a remarkably consistent threshold of $0.38 \pm 0.04$ at eruption onset across all cases, with a coefficient of variation of only $\sim 10$\%. This threshold specifically characterizes the critical conditions at eruption onset and is largely independent of the subsequent temporal evolution, making it the most robust eruptivity indicator identified. In contrast, other normalized helicity and energy metrics show greater scatter. Crucially, we further find that $H_j/H_r$ does not necessarily achieve its peak at the eruption onset time and its post-eruption evolution diverges based on magnetic topology: it continues to increase in bipolar configurations due to tether-cutting reconnection, which transforms sheared arcade into the erupting current-carrying magnetic flux, but decreases in quadrupolar configurations as breakout reconnection peels off the erupting flux. These results highlight the helicity ratio as a promising and consistent eruptivity indicator and provide new insights into its dynamic evolution due to different reconnections.

Context. Giant Low Surface Brightness galaxies, such as Malin 1, host extended discs exceeding 100 kpc. Their formation and evolution remain debated, with interactions with satellite galaxies and accretion streams proposed as key contributors. Malin 1 hosts satellites and exhibits two giant stellar streams, likely the result of past interactions. Aims. We investigate the orbital dynamics of Malin 1's satellites and their possible connections with observed stellar streams, testing their nature with different formation scenarios. Methods. We constructed gravitational potentials using optical and HI data, including stellar, gaseous, and dark matter components, and explored a wide parameter space while testing NFW and ISO halo profiles. Results. Some scenarios produced bound solutions. The ISO halo model ($M_{\text{Virial}} \approx 2.6 \times 10^{12}~M_{\odot}$) favours bound satellite orbits more than the NFW model ($M_{\text{Virial}} \approx 1.4 \times 10^{12}~M_{\odot}$). Giant stellar streams could be substructures of some satellite galaxies along their leading and trailing trajectories. The most distant Malin 1 satellite could have reached pericenter $\sim 1.6$ Gyr ago, while closer companions interacted as early as $\sim 100$ Myr ago. At the same time, one close companion displays both leading and trailing arms in radial and polar orbits. Furthermore, we also identify some unbound solutions linking satellites with streams. Conclusions. Satellites and stream alignment indicate that past interactions shaped Malin 1's morphology. Our modelling constrains progenitors and orbital histories, providing insights into the dynamical evolution of gLSBGs. Findings are consistent with recent studies using Malin 1 kinematic data.

The well-observed Crab pulsar helps one to uncover the underlying knowledge about pulsar evolution. The routine evolution model simultaneously describes the spin-down caused by the magnetic dipole radiation (MDR) and gravitational wave radiation (GWR), damping of the free-body precession owing to the bulk viscosity, and GWR-induced quenching of the magnetic inclination angle $\chi$. We explore the pulsar evolution based on this routine model supplemented with the effects of shear viscosity, r-mode, electromagnetic torque, and accretion, respectively, with the stellar thermal evolution as an important input. The impact of shear viscosity on radio-pulsar evolution is negligible, as it only slightly increases the magnetic inclination angle and promotes spin-down in magnetars. Under the observational limit for its saturation amplitude, the r-mode also turns out to be completely negligible. Yet, the electromagnetic torque (under certain conditions), along with the accretion based on our three-dimensional fallback disk accretion model, are all shown to suppress the growth of the magnetic inclination angle. When applied to the Crab pulsar, the routine model best reproduces the magnetic inclination angle $\chi$, the spin period $P$, and the spin period derivative $\Dot{P}$ simultaneously, indicating the important role of bulk viscosity. The inclusion of the electromagnetic torque and accretion works even worse, suggesting these two factors perhaps are overestimated for Crab pulsar. Intriguingly, the calculated magnetic inclination angle derivative $\Dot{\chi}$ is $(6.3\times 10^{-3} - 0.3)\, {\rm degree/century}$ with the routine model, also in agreement with the observed tiny $\Dot{\chi} = 0.62\, {\rm degree/century}$.

The historic detection of gravitational waves from the electromagnetically bright binary neutron star merger GW170817 enabled the first standard siren measurement of Hubble's constant ($H_0$). The accuracy and precision of this measurement depends crucially on how well the merger inclination angle is constrained, given its strong covariance with luminosity distance ($D_L$). Modeling the light-curve of the jet's afterglow provides constraints on inclination, but is highly dependent on the similarly uncertain jet opening angle. Past studies have improved on this by invoking high-resolution radio observations, obtained through very long baseline interferometry (VLBI). We present a Bayesian visibility-plane model-fitting framework that provides a more informed and robust measurement of the viewing geometry of GW170817 and of $H_0$, by including all relevant VLBI data, robustly handling systematic uncertainties and rigorously sampling model parameter space. By fitting new hydrodynamical afterglow models with a continuum of jet geometries, we obtain a viewing angle of $18.^{\circ}3-20.^{\circ}3$ (for a fixed cosmology with $D_L=40.7$ Mpc, as used in most previous analyses). We extend our framework to fit for $D_L$ and $H_0$ directly, and marginalize over an ensemble of plausible peculiar velocity corrections to obtain viewing angle $16.^{\circ}8-19.^{\circ}2$, $D_L=44.0\pm1.6$ Mpc and $H_0=65.5\pm4.4$ km s$^{-1}$ Mpc$^{-1}$. Notably, the peak of our $H_0$ posterior is within $0.5\sigma$ of the early-Universe Planck $H_0$ value, but $1.7\sigma$ from the late-Universe SH0ES measurement. We discuss potential caveats and the implications of this result in the context of the current discrepancy between early and late-Universe measurements of the Hubble constant.

The thermal state of active galactic nucleus (AGN) coronae is commonly characterized by the electron temperature $kT_{\rm e}$, the Thomson optical depth $\tau$, and the geometry of the Comptonizing medium. We compile a literature sample of Seyfert galaxies with broadband X-ray constraints obtained under slab geometry and with directly reported $kT_{\rm e}$ and $\tau$. To interpret these data, we develop a Monte Carlo radiative transfer calculation for bottom-illuminated slab coronae and show that the appropriate effective Compton parameter for slab geometry is $y=(4\theta+16\theta^2)\tau$, where $\theta = kT_{\rm e}/m_{\rm e}c^2$. We find that the cleaned AGN sample lies along a narrow anti-correlated ridge in the $kT_{\rm e}-\tau$ plane, corresponding to a nearly constant $y$ with mean $\langle y \rangle=0.414$ and logarithmic dispersion of only 0.10 dex. Radiative-equilibrium boundaries computed for slab disk-corona systems further show that reproducing this ridge requires a predominantly coronal dissipation fraction $f$. We therefore suggest that luminous AGN slab coronae occupy a stable Comptonization branch broadly governed by slab radiative balance, and that the observed $kT_{\rm e}-\tau$ locus provides a new constraint on how accretion power is partitioned between the disk and the corona.

Gravitational-wave (GW) signals from compact binary coalescences (CBCs) enable independent measurements of the Hubble constant \(H_0\) via the spectral siren method, which critically depends on an accurate model of the source-frame mass distribution. While the primary mass function has been extensively studied, the impact of the secondary mass distribution on cosmological inference has been largely overlooked. Here, we perform a joint inference of population and cosmological parameters using 142 confident CBC detections from GWTC-4.0, adopting a new parametric model that flexibly describes features in both the component-mass spectrum and the pairing function, with particular emphasis on the secondary masses. We find \(H_0 = 71.4^{+13.8}_{-13.4} \;\mathrm{km\,s^{-1}\,Mpc^{-1}}\) (68\% CL) from spectral sirens alone, and \(H_0 = 73.5^{+9.2}_{-7.2} \;\mathrm{km\,s^{-1}\,Mpc^{-1}}\) when combined with the bright siren GW170817. Compared to the standard LVK Fullpop-4.0 analysis, these constraints represent improvements of \(\sim29.8\%\) and \(\sim22.2\%\) in \(H_0\) uncertainty, respectively. The enhanced precision is driven by previously unmodeled features, including peaks near \(18\,M_\odot\) and \(65\,M_\odot\) as well as mass-dependent pairing transitions at \(28\,M_\odot\) and \(52\,M_\odot\). Our results demonstrate that the secondary mass function is also a key ingredient for precision standard siren cosmology.

High spatial resolution observations reveal that some protoplanetary disks host multiple ring-gap pairs at large stellocentric radii, yet their physical origin remains unsettled. We present a multi-wavelength analysis of the V1094 Sco disk using Atacama Large Millimeter/submillimeter Array Band 6 continuum and $^{12}$CO and $^{13}$CO $J=2-1$ emission, together with a Very Large Telescope/SPHERE near-infrared scattered light image. The continuum image shows four narrow dust ring-gap pairs extending to exceptionally large radii ($r \sim 380$ au), while the CO isotopologues trace a spatially extended gas disk ($r \sim 760$ au) in Keplerian rotation. From the dust ring widths, we place conservative upper limits on the turbulent viscosity parameter, $\alpha \lesssim 10^{-3}$ and potentially $\lesssim 10^{-4}$, implying weak turbulence. The ensemble of gap widths and depths is inconsistent with a simple one-planet-per-gap interpretation. At $r \simeq 100$ au, a double gap and its scattered light counterpart are consistent with multi-gap excitation by a single low-mass companion of $(55 \pm 35)\,M_{\oplus}$. At $r \simeq 170-230$ au, the outer ring system shows regular spacing and no clear scattered light counterpart, indicating mechanisms that operate primarily at the disk midplane. These outer rings are quantitatively compatible with secular gravitational instability. V1094 Sco therefore supports a hybrid pathway in which weak turbulence in an extended disk allows secular gravitational instability to assemble long-lived midplane dust concentrations that can cradle planet formation beyond $\sim 100$ au, alongside planet-driven substructures at intermediate radii.

Light propagating through a perturbed spacetime could imprint the underlying gravitational waveform directly onto electromagnetic observables. In this Letter, we develop a covariant perturbative framework for polarized photon propagation in generic curved spacetimes, and derive a compact expression for the observable polarization-angle (PA) swing during Kerr ringdown, explicitly demonstrating its time-domain locking to the quasi-normal modes. We confirm this behavior using dynamical ray-tracing calculations for a broad class of photon trajectories. Photons grazing the strong-field region exhibit an achromatic, damped PA oscillation that tracks the ringdown, with a phase set by the mode's angular structure. The swing amplitude can reach $\sim 10^{\circ}$ and leaves distinctive signatures in spatially resolved autocorrelations. These results open a new polarimetric window onto black hole mergers and ringdown.

Gamma-ray bursts (GRBs) are the universe's most energetic phenomena (isotropic luminosity $\sim 10^{51} - 10^{54}$ ergs/s) lasting for a very short duration ($\sim$ milliseconds - a few seconds). Even after an average of one GRB detected per day, their emission mechanism remains contentious. Inferences drawn from the empirical modelling of the GRB spectrum are often inconclusive. Some studies favor the emission from a thermal blast of hot plasma, while others suggest a synchrotron emission originating from a rapid acceleration of particles at the expense of the burst energy. Under these scenarios, the spectral width of the burst ($\mathcal{W}$), which is measured at half maxima, is expected to decrease with time. We show that for the GRB 220426A and GRB 230812B, $\mathcal{W}$ increases with time, raising serious concerns regarding the validity of these emission models. The results instead offer strong evidence that the GRB prompt phase involves the development of multiple emission zones, whose relative contributions change over time.

Galaxy rotation curves provide a direct test of how baryonic matter and dark matter combine to determine the mass profiles of disk galaxies. In ultralight or fuzzy dark matter models, numerical simulations predict a central solitonic core surrounded by an outer halo, but the population-level relation between the core and the host halo remains an important modelling choice. We present a hierarchical Bayesian pipeline for fitting soliton-plus-NFW rotation-curve models to the SPARC database while treating the core-halo scaling exponent as a global free parameter. The model uses a Schive-normalized soliton, a regularized NFW envelope with a smooth transition, halo-mass priors tied to $V_{\rm flat}$, and stellar-to-halo-mass information. We apply the pipeline to 106 SPARC galaxies, including 26 systems with bulges, and sample the resulting 346-dimensional posterior with JAX/NumPyro NUTS. The free-scaling run has zero divergences and $\hat r \simeq 1.000$ for the global parameters. The posterior reaches the upper edge of the standard mass prior and the lower edge of the scaling prior, with $\log_{10}(m_\phi/{\rm eV})=-19.20^{+0.12}_{-0.11}$ and $\alpha=0.014^{+0.023}_{-0.011}$. This boundary behaviour persists after removing UGC06787 and after widening the high-mass stellar-to-halo-mass prior. Within the adopted Schive-normalized model and standard SPARC fuzzy-dark-matter prior range, the selected SPARC sample does not identify an interior population-level soliton component. The main contribution is the hierarchical inference framework and the diagnostic workflow for recognizing boundary solutions in full-sample rotation-curve analyses.

Dense, compact circumstellar media (CSM) are required to power strongly interacting supernovae, yet their physical origin remains uncertain. We present a systematic study of binary stellar evolution models computed with MESA, demonstrating that Case C mass transfer, initiated after core helium ignition, can naturally produces the dense, nearby CSM inferred in interacting events. Across a grid of binary models, we find that donors of 10--20 solar masses in binaries with separations of approximately 1000--2700 solar radius undergo late-stage Roche-lobe overflow within ~10^3 yr prior to core collapse, ejecting ~0.01--0.2 solar masses and forming CSM extending to ~10^16--10^18 cm. Our results suggest that the Case C mass transfer may account for ~13% of all core-collapse supernova (CCSN) progenitors, rather than representing a rare channel. A subset of these Case C binaries produces CSM properties that are quantitatively in agreement with those inferred for interacting supernovae such as SN 2014C. In contrast to earlier binary interactions or single-star mass loss, Case C transfer operates at the right time and scale to shape the immediate pre-supernova environment without requiring ad hoc eruptive mechanisms. Our results identify late-stage binary interaction as a robust and physically motivated channel for producing the dense CSM that powers interacting supernovae.

The first generation of stars, Population III (Pop III), is believed to be massive, with some potentially having masses in the range 140 M$_\odot$ to 270 M$_\odot$ and capable of exploding as a pair-instability supernova (PISN). Such events release large amounts of energy and produce substantial quantities of metals, suggesting that they should leave characteristic signatures in the abundance patterns of extremely metal-poor (EMP) stars observed in the local Universe. No clear imprint of PISNe is seen in the local EMP star population, implying either that these events were rare or that stars forming from PISN-enriched gas had metallicities too high to find them in the EMP population. Previous work explored the latter possibility by investigating the enrichment by PISNe with masses and explosion energies at the upper end of the theoretical range (270 M$_\odot$, $10^{53}$ erg). Here, we complement that work at the opposite extreme: Pop III stars at the lower mass (140 M$_\odot$) and explosion energy ($5\cdot 10^{51}$ erg) limit. Using a cosmological hydrodynamic simulation, we self-consistently track the formation of Pop III stars, their radiative and mechanical feedback, and the subsequent formation of second-generation stars in metal-enriched gas. We find that all second-generation stars are exclusively internally enriched by their progenitor within the same halo, thereby imprinting the abundance pattern of a single first-generation star. The median [Fe/H] abundance of second-generation stars is ~ -5.5 which is 2.9 dex smaller than in the high-energy PISN case. Our results demonstrate that if Pop III PISNe were common, we would expect to find stars with the characteristic odd-even abundance pattern produced by PISNe within the observed EMP population. Their absence in observations therefore strongly disfavours PISNe as the dominant channel of early metal enrichment.

We analyzed 11 epochs of archival Atacama Large Millimeter/submillimeter Array (ALMA) data to investigate flux density variability of Sgr A* at 340 GHz. In one epoch, the light curve exhibits two short-timescale components with characteristic periods of ~30 min and ~50 min. While the corresponding peaks in the periodogram are highly significant under a white-noise assumption, their significance decreases below 3 \sigma when red-noise variability is taken into account, and we therefore do not regard them as statistically significant periodic detections. Nevertheless, the observed timescales are comparable to the orbital period near the innermost stable circular orbit of Sgr A*, and the light curve shows phase-dependent structure and amplitude evolution consistent with orbital modulation. We find that the variability is well described by a model involving multiple orbiting hotspots with decaying emission. This interpretation suggests that both periodic and non-periodic variability in Sgr A* may arise from a common physical origin in orbiting structures within the accretion flow, providing a unified framework for its millimeter variability.

We present new Doppler images of the K0 subgiant primary component of the RS CVn-type binary UX Arietis (UX Ari), derived from time-series spectra obtained in November--December of 2017 and 2024. Observations demonstrate that some spectral lines of the K0 IV component exhibit rapid changes on timescales of 1-2 hours, which seem not to be resulting from spot activity, meanwhile other spectral lines show no such fast variations. Through an investigation, we find that the Ca I 6439 $\unicode{x212B}$ profile shows variation that follows the rotational modulation of spots. Using this line as a reference, we derive the least-squares deconvolution (LSD) profile from the selected lines of each spectrum so as to generate a more reliable Doppler image, which is consistent with the shape of the corresponding Ca I 6439 $\unicode{x212B}$ line. The Doppler images are separately reconstructed from the Ca I 6439 $\unicode{x212B}$ and the LSD profiles for each dataset, and the surface maps are in good agreement with each other. All of the surface maps show dominant starspot structure at mid-to-high latitudes with appendages extending to the equator, while their locations differ by about 0.5 in the rotational phase between 2017 and 2024. In 2017 November-December, the main starspot group appears to be spatially associated with a large flare event just half a month later. Through the cross-correlation method, we have derived a weak anti-solar differential rotation for the primary component of UX Ari, while its equator belt is well tidally locked.

The Cherenkov Telescope Array Observatory (CTAO) and the Vera C. Rubin Observatory are set to transform our understanding of the universe over the next decade. These two observatories have multiple areas of complementarity in their scientific applications, ranging from constraints on cosmological parameters to studies of asteroid occultations. The most opportune area of synergy probably lies in the field of time-domain astronomy. Due to their sensitivity and saturation limits, it will be difficult for the two observatories to conduct joint studies of variable and transient sources in the Milky Way. However, they could offer a fresh and rich perspective on non-thermal extragalactic sources, in particular gamma-ray bursts, active galactic nuclei and jetted tidal disruption events. Among these sources lie the best candidates for multi-messenger research into the origin of TeV-PeV neutrinos and multi-EeV cosmic rays. Thus, combined with multi-wavelength observations by X-ray satellites and wide-field gamma-ray instruments, the synergy between Rubin and the CTAO could provide answers to some of the most important questions in astroparticle physics. This scientific potential comes with a challenge: selecting a few alerts from the ten million issued by Rubin each night to repoint the CTAO telescopes. We use the variability of blazars over timescales ranging from a few days to several years as a case study to demonstrate how to address this challenge using the Fink broker of Rubin.

We introduce a new general-relativistic timing observable that measures the breaking of reflection symmetry in photon arrival times caused by black hole spin. Using backward ray tracing in the Kerr spacetime, we construct time-delay maps across the observer image plane and define a mirror-paired asymmetry based on photons arriving from opposite sides of the projected spin axis. In the Schwarzschild limit ($a=0$), the asymmetry vanishes to numerical precision, providing a stringent validation test of the method. For rotating black holes, Kerr rotation breaks the left-right propagation symmetry of null geodesics, producing systematic differences between prograde and retrograde photon trajectories and resulting in a nonzero mirror-paired timing asymmetry, $A_t$. We find that $A_t$ increases with spin and depends strongly on observer inclination and emission radius, with the largest signals arising from emission close to the black hole and from intermediate to high inclinations. Converting the dimensionless asymmetry into physical units yields timing offsets ranging from seconds to hours for representative supermassive black hole systems. Unlike traditional timing analyses based on spatially integrated signals, the observable introduced here isolates directional information encoded in Kerr photon propagation and provides a physically motivated timing signature of black hole rotation. We discuss the implications of this effect for strong-gravity timing studies and X-ray reverberation mapping.

Accurate and comprehensive H2 pressure-induced broadening data for CO2 infrared lines over a wide temperature range are essential for modeling atmospheric opacity of exoplanets. However, available data are currently limited, some of which are affected by large uncertainties. In this work, H2 induced pressure-broadening and pressure-shift coefficients were determined at room temperature for the entire nu3 band of CO2 in the 4.3 micrometer spectral region using a high-resolution Fourier transform spectrometer. In addition, requantized molecular dynamics simulations of the CO2-H2 system were performed using an accurate intermolecular potential. These simulations provide theoretical predictions of H2-broadening coefficients for CO2 lines over a temperature range of 200-1000 K and for rotational quantum number up to J=120. The predicted results show very good agreement with the experimental data, with difference of less than 3%, well below the precision required for exoplanet atmosphere studies. This work provides the first accurate and comprehensive dataset of H2 broadening coefficients for CO2 lines, suitable for modeling of H2-rich exoplanetary atmospheres.

In this work, using the simulator VPLanet, we analyze the spin evolution of some selected exoplanets due to the tidal interaction with their host star. For a rocky planet, two spin conditions are possible, the trapped rotation and the fast rotation, referring to the cases of achieved and non achieved tidal trapping, respectively. We focus on planets whose spin condition is not obvious, because no study is needed for planets which are undoubtedly fast rotators or undoubtedly trapped rotators; moreover, we consider only exoplanets that are interesting from an astrobiological perspective. The current spin conditions of the considered planets are hypothesized, taking into account the age of the host star. Inferences regarding planetary climate and habitability, which is defined by the possibility of stably sustaining the liquid water on the surface, are also discussed. Results of this work show that Kepler62f, Kepler1126c and Kepler1544b are expected to be fast rotators regardless of the orbital eccentricity; the spin condition of Kepler186f, Kepler62e, and Kepler442b cannot be determined without constraints on the eccentricity, which are currently unavailable; Kepler440b is expected to be tidally trapped.

Rubble-pile asteroids can form through the self-gravitational reaccumulation of fragments produced during large-scale collisions. To investigate how differentiated bodies are disrupted and how iron-rich rubble piles may form, we performed smoothed particle hydrodynamics simulations of impacts between differentiated asteroids with molten or solidified interiors. Our results show that catastrophic disruption produces a sheet-like structure in which core and mantle materials are stretched and subsequently fragment under self-gravity. The resulting fragments exhibit nearly identical iron-rock mass ratios, indicating that catastrophic disruption naturally generates numerous compositionally similar fragments. The largest remnant formed in such events is therefore an iron-rich rubble pile assembled from these mixed fragments, whereas remnants formed through mantle stripping retain a layered structure with an iron core and rocky mantle. We further find that fragment production is sensitive to material strength and the equation of state: mantle strength reduces the number of small fragments, while core strength suppresses catastrophic disruption when the core is solid. These results imply that iron-rich rubble-pile asteroids can form only when the iron core is molten. Our findings provide a unified framework for the formation of metal-rich asteroids such as (16) Psyche and the (22) Kalliope system, and offer predictions for the surface and internal structure that the NASA Psyche mission may test.

A method for real-time solar flare detection and characterization using ground-based Very Low Frequency (VLF, 15-45 kHz) data is presented. The D-region, the ionosphere's lowest region, is monitored by VLF waves propagating in the Earth-Ionosphere waveguide. The D-region electron density increases during sudden surges in X-ray radiation from solar flares. This subsequently enhances HF absorption. By seeking trend changes in VLF phase data, an incremental algorithm finds solar flares. 82.7% of M and X solar flares are detected within one fourth of their rise time. In addition, several VLF transmitters are monitored simultaneously. Combining information from their phase variations leads to an estimation of the Sun's X-ray flux. Last, propagation models such as LMP or LWPC are combined with the VLF measurements to compute D-region electron density profiles. This method and its implementation in a new Python package are a step towards building a more resilient system for flare detection and alerts. Its reliance on ground-based data alone ensures an easy maintenance and a backup in case a satellite failure. It also provides alerts comparable to or faster than those obtained through satellite data, due to shortened data latency.

The origin of diffuse neutrinos and $\gamma$-rays is unknown, and galaxy clusters hosting AGN and starburst galaxies are the most probable sources of these cosmic messengers. In this work, we investigate the diffuse $\gamma$-ray and neutrino emission from the Virgo, Perseus, and Coma clusters using a detailed numerical method, combining MHD simulations with Monte Carlo methods. The MHD simulation provides the distributions of temperature, gas, and magnetic field in clusters. The Monte Carlo simulations are used to investigate the cosmic-ray (CR) propagation in ICM and subsequently the secondaries stemming from CRs. Our primary assumption is that CR injection scales with the gas density of clusters, providing a physically motivated approximation. High-density regions in clusters are associated with strong turbulence and prominent shock structures, making them natural sites for efficient CR acceleration. Our predicted $\gamma$-ray flux from the individual clusters lies well below the present LHAASO upper limits. The MAGIC observations of the central source NGC $1275$ of the Perseus cluster are significantly higher than our results. Further, we estimated the cumulative $\gamma$-ray and neutrino fluxes from clusters with masses $\gtrsim 5\times 10^{13}, M_{\odot}$ in the local Universe (within $500$ Mpc). The diffuse $\gamma$-ray flux reported by the Fermi-LAT collaboration is significantly higher than our results. Our predictions are consistent with IceCube's existing upper limits on the unresolved neutrino flux from galaxy clusters ($M > 10^{14}, M_{\odot}$) up to $z = 2$.

We calculate the high-energy gamma-ray and neutrino emissions from galaxy clusters like Perseus that host active galactic nuclei (AGNs). Our primary objective is to distinguish the emission from the central source, such as NGC$1275$, from the diffuse emission originating in the outskirts of the Perseus cluster. Due to a unique magnetic-field configuration, CRs with energy $\leq 10^{17}$ eV can be confined within these structures over cosmological time scales, and generate secondary particles, including neutrinos and gamma-rays, through interactions with the background gas and photons. We employ three-dimensional cosmological magnetohydrodynamical simulations of structure formation to model the turbulent intracluster medium (ICM). We propagate CRs in intracluster medium (ICM) and intergalactic medium using multi-dimensional Monte Carlo simulations, considering all relevant photohadronic, photonuclear, and hadronuclear interactions. We also include the cosmological evolution of sources like Perseus. By comparing our results with the existing upper limits from IceCube for galaxy clusters and the sensitivity of CTA, we predict that these observatories could potentially establish a new class of astrophysical sources capable of emitting high-energy multi-messenger signals. We also compute the contribution from clusters like Perseus to the diffuse neutrino and gamma-ray background.

Dynamical capture in dense stellar environments is a promising channel for producing eccentric compact binary mergers. Although there have been no confident detections of eccentric mergers to date, a few candidates show indications of non-negligible in-band eccentricity upon re-analysis of the data. By assuming an observed eccentric event originates from a dynamical gravitational wave (GW) capture, we show that it is possible to identify the host environment using the eccentricity and mass posteriors. In particular, the eccentricity posterior can be mapped to posteriors on key capture parameters, such as the relative velocity at infinity and the impact parameter. By comparing these with the expected velocity distributions of different astrophysical environments, we can place constraints on the likely host. Assuming that it originated from a GW capture, we applied this framework to the neutron star-black hole merger GW200105. By comparing with the velocity dispersion distributions of neutron stars in the cores of globular clusters (GCs) and nuclear star clusters (NSCs), we find the probability that GW200105 merged in a GC (NSC) to be 29% (71%). As we anticipate detecting several eccentric mergers in the future, this method can provide a valuable astrophysical diagnostic of their host environments on a single-event basis; this can be straightforwardly generalized to a population of eccentric binaries. The formalism we develop is also applied to GW190521, but is less constraining for that event. Lastly, we infer a GW decay time from capture to merger of 11-156 days for GW200105.

We carry out a search for high energy muon neutrino emission from the galaxy cluster Abell 119, motivated by a recent detection of GeV gamma rays from this cluster using the Fermi-LAT telescope, which hinted at a hadronic origin. For this purpose, we used the 10-year muon track data from 2008-2018, provided by the IceCube Collaboration and implement the unbinned maximum likelihood emission. We do not find any statistically significant excess and the test statistics is consistent with a null result. We then obtain upper limits (at 95\% confidence level) on the differential muon neutrino energy flux from this cluster, whose value is equal to $2.42 \times 10^{-10}~\mathrm{GeV}~\mathrm{cm}^{-2}~\mathrm{s}^{-1}~\mathrm{sr}^{-1}$ at 100 TeV. This limit is about 1.2 times lower than the predicted neutrino flux required to explain the hadronic origin of the galaxy cluster emission, thus marginally ruling it out. Therefore, additional data from future neutrino detectors should be able to definitively rule out a hadronic origin for the observed gamma-ray emission in Abell 119.

High-resolution ground-based solar imaging relies heavily on multi-object multi-frame blind deconvolution to correct for atmospheric turbulence. However, the traditional joint maximum likelihood estimation methods in which object and the atmospheric aberrations are estimated together face some problems. In this paper, we introduce a marginal estimator for the multi-object multi-frame blind deconvolution problem. By employing a framework to marginalize over the observed objects, we develop a reconstruction method that offers several distinct advantages over joint estimation. First, the marginalization provides enhanced regularization that naturally accounts for object uncertainty, successfully preventing the reconstruction algorithm from erroneously assigning noise to high-order aberrations. Second, the marginal estimator yields more contrast control, as it is much less sensitive to the hyperparameters dictating the power spectral density (PSD) of the object. This robustness allows these hyperparameters to be optimized, enabling a ``plug-and-play'' deployment that removes the need for manual tuning. Finally, we demonstrate that the proposed method is accessible and simple to implement, requiring only the addition of a log-determinant term to the traditional merit function. With minimal modifications required for existing blind deconvolution pipelines, the estimator has been fully integrated into the open-source torchmfbd package for its use by the solar physics community.

Robust age measurements for isolated neutron stars (NSs) are not easily available. That is why, often the characteristic age $\tau_\mathrm{ch}=P/2\dot P$ is used as a proxy. Here $P$ is the spin period of the NS and $\dot P$ is the time derivative of $P$. Additional assumptions related to the initial properties and spin-down evolution are made to derive $\tau_\mathrm{ch}$. As a result, it is expected that $\tau_\mathrm{ch}$ is an upper limit for the real age $\tau_\mathrm{real}$. Recently, Chrimes et al. presented measurements of kinematic ages $\tau_\mathrm{kin}$ for several magnetars. Surprisingly, for the majority of these sources $\tau_\mathrm{kin}>\tau_\mathrm{ch}$. We present a simple model including a realistic approximation for the magnetic field decay in magnetars and a simple phenomenological description of the field re-emergence after an episode of fallback after the birth of a NS. We demonstrate that this simple model can explain the observed relation $\tau_\mathrm{kin}>\tau_\mathrm{ch}$ for realistic sets of parameters.

Dwarf carbon stars are dominated by members of the Galactic halo and are thus likely carbon-enhanced metal-poor stars. In this work, a sample of 879 bona fide dwarf carbon stars are characterized by their ground-based light curves, and p<15 d modulation is found to be significant in 31 objects (3.5%), consistent with starspots and rotation in tidally-locked, post-common envelope binaries. Among these is an unambiguous halo star that is eclipsing every 1.224 d, and where the 30% eclipse depth rules out a white dwarf occulter. Available Gaia data do not indicate any tertiary in the eclipsing system, but this remains a possibility and follow-up data are necessary to determine the evolutionary history of this first eclipsing binary among carbon-enhanced stars. Four of the variable sources exhibit clear multi-year, quasi-sinusoidal trends indicative of magnetic-activity and starspot cycles in rapidly-rotating, dynamo-rejuvenated stars. These data support a picture where carbon pollution results from wind capture prior to Roche lobe overflow, and the orbital period distribution appears to be moderately shifted to longer periods than carbon-normal, low-mass stars in similar binaries. The band-combined approach adopted in this work may be more sensitive than prior work using single-bandpass light curves, where at most 19 of 34 binary candidates published by Roulston et al. (2021) are independently confirmed here.

We study how constraints on the abundance of ultralight axions (ULAs) from cosmic microwave background (CMB) data depend on their nonlinear modelling. We focus on the axion mass range $10^{-25} \leq m/\rm{eV} \leq 10^{-23}$, where the axion Jeans scale falls in the quasi-linear regime probed by CMB lensing, making constraints highly sensitive to the choice of nonlinear prescription. We show that the inferred constraints depend significantly on the choice of nonlinear model, which must therefore be treated carefully. Performing Markov Chain Monte Carlo (MCMC) analyses with \Planck\, 2018, ACT DR6 and DESI DR2 BAO data, we find naive nonlinear modelling of non-cold matter can produce an artificial preference for a subdominant ULA dark matter component with mass $m \approx 10^{-24}\,$eV. This arises from a lensing-like enhancement of the CMB power spectrum.

We present a statistical study of 130 solar flares (B to X class) that lack soft X-ray quasi-periodic pulsations and show no kink oscillations of nearby coronal loops visible in SDO/AIA 171~Å~images. The aim is to investigate whether decayless kink oscillations of coronal loops respond to nearby flaring activity. Using the Fractional Anisotropy-based Video Motion Magnification technique, we detected low-amplitude decayless oscillations in all 130 loops before, during, and after each flare, confirming their ubiquitous nature. Oscillation periods are found to range from 122~s to 268~s, and the projected displacement amplitudes are 0.023--0.111~Mm. No amplitude--period correlation is found. For each event, we estimated the amplitude before, during, and after the flare. Across all flare classes, the average amplitude remains unchanged. However, in some specific cases, the oscillation amplitude may exhibit minor changes. For B-, C-, and M-class flares, the fraction of events with an amplitude change exceeding 10% is approximately 23%, 41%, and 36%, respectively. In M-class flares, such minor amplitude increases occur four times more often than decreases; in X-class flares (only six events), decreases dominate by a factor of three. The fraction of events that exhibit an increase in the amplitude of more than 20% appears to be highest when the loop centre is located at a distance of 100--120~Mm from the flare site, reaching 33% (6 out of 18 events). Overall, the amplitude of decayless kink oscillations does not undergo a major change in response to nearby flares, especially for less powerful classes, suggesting that flare-related processes such as blast waves and reconnection inflows have little effect on the energy supply to oscillating loops.

The Hybrid Elevated Radio Observatory for Neutrinos, or HERON, is a newly proposed ultrahigh energy Earth-skimming tau neutrino detector. Ultrahigh energy tau neutrinos which skim the Earth may produce $\tau$-leptons which escape into the atmosphere and initiate up-going extensive air showers. The HERON concept consists of 24 compact phased radio arrays, embedded within a larger sparse array of 360 standalone antennas, distributed along a mountain range and designed to capture the radio emission of these up-going extensive air showers. Due to the high elevation observation sites and the long propagation length of radio, HERON achieves a very large instantaneous effective area towards the horizon, and thus excels at the detection of astrophysical transient events such as gamma-ray bursts. With the excellent pointing resolution offered by the sparse array, HERON would be capable of conducting UHE neutrino astronomy and could be incorporated into the broader network of multi-messenger instruments. Here, we detail the HERON concept and describe the science which can be accomplished with it.

Fast radio bursts (FRBs) are intense, short-duration radio transients of mysterious origin. They have been detected across a wide range of frequencies from 110 MHz to 8 GHz. Their spectral properties, remaining poorly understood, are essential for understanding the intrinsic radiation mechanism and propagation effects. Here, we report the discovery of a periodic modulation in the central emission frequency of FRB 20240114A, based on more than one thousand bursts collected by an ultra-wideband receiving system. The burst central frequencies reveals a significant modulation with a period of $\sim 112$ days. The statistical significance of this detected periodicity exceeds $6\sigma$ for both the Lomb-Scargle and phase-folding methods. Within a single period, the central emission frequency exhibits a systematic drift from lower to higher values. We evaluate several physical mechanisms for this unique spectral evolution. The free-free absorption together with cyclotron resonant absorption in a binary system or free precession models could potentially explain such behavior. The discovery of this periodic frequency modulation unveils a new layer of complexity in the underlying radiation mechanism and propagation effect of FRBs.

The epoch of reionisation is a key phase in cosmic history, but its detailed evolution remains poorly constrained by current cosmic microwave background (CMB) observations. We investigate whether the kinetic Sunyaev--Zel'dovich (kSZ) effect can discriminate among reionisation histories consistent with current large-scale CMB constraints. Using histories derived from Planck data, we compute the corresponding kSZ angular power spectra within an analytical framework, separating late-time and patchy contributions and accounting for uncertainties in both the ionisation history, $x_e(z)$, and astrophysical parameters constrained by the LORELI II simulations. The allowed histories fall into two broad classes, `short' and `long' duration reionisation, yielding distinct kSZ signatures. Uncertainties from $x_e(z)$ and astrophysical parameters produce comparable amounts of dispersion, yet the two classes remain clearly separable, with variations within each class at the $\sim$10\% level. Current kSZ measurements ($\sim$0--3 $\mu$K$^2$) are not yet precise enough to distinguish between these scenarios, although they tend to favor a `short' reionisation. The kSZ effect thus provides a promising probe of reionisation beyond optical depth constraints. In particular, a measurement of the kSZ power spectrum at $\ell \sim 2000$ with $\sim$0.4 $\mu$K$^2$ sensitivity would discriminate between `short' and `long' reionisation scenarios.

We investigate whether atmosphere models traditionally used for massive stars with strong winds can produce synthetic spectra morphologically similar to those of Little Red Dots (LRDs). We compute atmosphere models and synthetic spectra with the code CMFGEN. The models assume a thermalized radiation field at the inner boundary, parameterized by a temperature varying between 5000 and 12000~K. We adopt a typical luminosity of 1e10 Lsun. The models are spherical, assume an expanding atmosphere, and are computed under non-LTE conditions and for several metallicities. The spectral energy distribution (SED) is different from a blackbody, with a blue optical spectrum. Broad hydrogen emission lines are produced, their wings being formed by electron scattering. The SED near the Balmer and Paschen limit is rather continuous. A Balmer break is predicted for the coolest temperature models provided the wind density is reduced. The SED and Balmer decrement of most LRDs is reproduced by the models, provided they are dust-attenuated with Av~1.9-2.7. Assuming the absorbed luminosity is re-radiated in the infrared, the energy output at these wavelengths is consistent with observational constraints. The models predict FeII, oxygen and calcium lines. OI lines at 8446 A and 1.129 um are produced mostly by Lybeta fluorescence. The strength of emission lines from metals depends on input temperature, metallicity, and details of the radiative transfer models. CMFGEN atmosphere models predict a large number of spectral properties observed in many LRDs. They struggle to simultaneously produce a genuine Balmer break and strong emission lines. Whether they are more relevant or not to explain LRDs' spectra compared to alternative models is unclear, leaving open the question of the physical conditions in LRDs.

Active galactic nuclei (AGN) profoundly affect the interstellar medium of their host galaxies through intense radiation fields and powerful winds. Characterising this feedback is essential for understanding galaxy formation and evolution. Here we revisit the origin of proximate damped Lyman-$\alpha$ absorbers (PDLAs), which trace cold gas within 3000 km/s of the quasar redshift, and interpret their kinematics and physical properties within a unified framework. We searched the SDSS DR16 database for low-ionisation metal absorption-line systems at the quasar redshift (referred to as ProxSys). This approach enables us to identify and classify different types of proximate absorbers, including so-called Ghostly systems, coronagraphic DLAs (DLA-Cor), standard DLAs, and sub-DLAs, based on the presence of strong Lyman-alpha absorption, partial covering signatures, or excited atomic transitions such as SiII*. We find that about 13% of ProxSys belong to the Ghostly or DLA-Cor classes and exhibit strong absorption from excited species. The different classes of ProxSys form a continuous sequence characterised by decreasing SiII*, CIV, and NV absorption strengths and dust content. Their velocity distributions reveal multiple kinematic components. Standard DLAs cluster within 1000km/s of the quasar systemic redshift, consistent with gas in the host galaxy, whereas Ghostly and SiII* bearing systems display broader distributions, including outflows reaching -2000 km/s and a smaller population of inflowing clouds up to +1200 km/s. Median stacked spectra confirm that Ghostly and coronagraphic systems arise in dense, compact gas partially covering the quasar emission regions. These results support a scenario in which cold, dense clouds participate in a dynamic cycle of inflow and outflow in the vicinity of quasars, consistent with chaotic cold accretion.

Infrared dark clouds (IRDCs) contains cold dense gas at the earliest stage of massive star and cluster formation. In studying the IRDCs, a universal and fundamental task is to resolve their internal hierarchical structures. Various packages and algorithms were developed for this purpose, but with most of them mainly focused on certain individual steps in data processing. In this work, we build a more automatic procedure for multi-band structure measurement HONKAI (Hierarchical cOre ideNtification and Kinematic property AssIgnment), which can resolve the elemental components including cores and clumps, disentangle the velocity components in spectral data, measure their physical properties, and generate a catalogue for all the measured properties. We use {\sc honkai} for a joint study towards three IRDCs observed in 850 $\mu$m dust continuum with James Clerk Maxwell Telescope (JCMT) and the $^{13}CO$ $(1-0)$ data cube with the Purple Mount Observatory 14-m telescope. 193 dense cores in 16 clumps are identified. As major dynamical properties, a large amount of the cores (136 out of 193) are measured to have large virial ratio of $R_{\rm vir}>1$, but their mass-size relation is bellow the threshold for massive star formation. Meanwhile, core mass function (CMF) also exhibits a steeper slope towards high-mass end compared to more evolved core samples. These three properties in accordance suggest that although many IRDC cores are self-gravitating, only a small fraction are seemingly possible to form high-mass stars. In subsequent core evolution, some further mass assembly trend may be involved to facilitate the high-mass star formation.

We report the discovery and characterisation of the multi-planetary system around TOI-4311, a K dwarf kinematically between the Galactic thick disk and Hercules stream. TOI-4311 hosts an ultra-short-period super-Earth (P$\sim$0.99 d, $1.376\substack{+0.077\\-0.080}$ R$_\oplus$) and a longer period sub-Neptune (P$\sim$15 d, $2.47\substack{+0.12\\-0.11}$ R$_\oplus$) that was first detected in the TESS photometry. Using follow-up observations with CHEOPS and HARPS, we refine the planetary radius of both planets, derive the mass of planet b ($4.5\substack{+1.5\\-1.4}$ M$_\oplus$) and confirm the planetary nature of planet c. Intriguingly, a third periodic signal is clearly detected in our HARPS RVs that we cannot link to stellar activity. This signal could be attributed to a third planet (P$\sim$38 d, Msin(i)=$26.4\substack{+6.3\\-6.8}$ M$_\oplus$) in the system, however with the current photometric dataset we do not find a transit. Our dynamical analysis highlights that this potential outer planet would remain stable. Using the precise radius and mass for TOI-4311 b we model its interior structure and find that it is very dense given the host star's galactic kinematics and chemistry. Hence this system could challenge current formation theories and provide insights into planet formation across the galaxy.

Stellar rotation on the main sequence is a complex function of mass and age, displaying multiple regimes whose physical origin remains only partially understood. In particular, the connection between the diversity of observed rotation rates and the internal structure and thermodynamic properties of stellar interiors is still unclear. We investigated how the depth of the convective zones and the degree of plasma coupling, quantified through the plasma coupling parameter, relate to the observed rotation rates of solar-mass stars. We used a grid of $1 \, M_\odot$ MESA stellar models with a wide range of metallicities to identify the best-matching models for 243 main-sequence stars with measured rotation periods. We then examined correlations between their rotation rates and both the structural properties of the convective zones and the corresponding convective plasma coupling parameter. For this sample, rotation rates show only weak correlations with either the convective-zone depth or the plasma coupling parameter when considered independently. However, during the first two-thirds of the main-sequence lifetime, the correlation strengthens when both factors are considered jointly through a combined convective coupling index, indicating a moderate and statistically significant relationship. For older stars, these correlations weaken and lose significance, although the thermodynamic component becomes relatively more influential. These trends suggest that microphysical plasma properties may contribute to the regulation of angular momentum loss and may be connected to the onset of weakened magnetic braking.

We hydrodynamically simulate a core-collapse supernova (CCSN) explosion by launching three pairs of jets in the framework of the jittering-jets explosion mechanism (JJEM), and reproduce a morphology of two opposite circum-jet rings and a bar of dense gas perpendicular to the rings' axis, resembling these morphological features in the CCSN remnant SNR G11.2-0.3. The first pair of wide jets is very energetic; it triggers the explosion and inflates two bubbles that compress the material in an expanding shell. The bubbles also compress material in a plane perpendicular to the jet axis. The second pair of wide jets removes material from this plane, beside along a bar that is on an axis perpendicular to the two pairs' axes. The jets of the third pair, now of narrow jets, penetrate the expanding shell and compress material to their sides to form two opposite rings. These morphological features are qualitatively similar to those observed in the point-symmetric CCSNN remnant G11.2-0.3. As competing theoretical CCSN explosion mechanisms cannot explain point-symmetric CCSN remnants, our study provides support for the claim that the JJEM is the primary explosion mechanism of CCSNe.

We present a novel method for extracting moving objects from TESS data using machine learning. Our approach uses two stacked 3D U-Nets with skip connections, which we call a W-Net, to filter background and identify pixels containing moving objects in TESS image time-series data. By augmenting the training data through rotation of the image cubes, our method is robust to differences in speed and direction of asteroids, requiring no assumptions for either parameter range which are typically required in "shift-and-stack" type algorithms. We also developed a novel method for learned data scaling that we call Adaptive Normalization, which allows the neural network to learn the ideal range and scaling distribution required for optimal data processing. We built a code for creating TESS training data with asteroid masks that served as the foundation of our effort (tess-asteroid-ml), which we publicly released for the benefit of the community. Our method is not limited to TESS, but applicable for implementation in other similar time-domain surveys, making it of particular interest for use with data from upcoming missions such as the Nancy Grace Roman Space Telescope and NEOSurveyor.

The Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) will deliver an unprecedented Type Ia supernova (SN) sample, making photometric calibration systematics a dominant source of uncertainty in dark energy constraints. We perform a comprehensive analysis of calibration systematic effects in LSST, quantifying how uncertainties in the LSST passbands propagate into biases in SN distance moduli and, consequently, the dark energy equation of state parameters. Specifically, we examine how the inferred values and uncertainties of $w_0$ and $w_a$ shift as a function of the amplitude of passband systematics. For linear passband tilts, we find that the best-fit ($w_0$,$w_a$) shifts by $\sim$0.025$\sigma$ and the $w_0-w_a$ contour area increases by $\sim$5% for each 1%/100nm increase in tilt, while for quadratic passband tilts, our results are less conclusive and warrant further exploration. This analysis will help inform the calibration accuracy required for LSST to achieve its goals in constraining dark energy.

We present a non-parametric, model-independent reconstruction of the cosmological background and perturbation dynamics in non-minimally coupled theories of gravity. Within the Effective Field Theory of dark energy framework, we reconstruct the time-dependent cosmological constant, $\Lambda(t)$, and the non-minimal coupling function, $\Omega(t)$, from cosmological data. To ensure stability, we apply a correlated smoothness prior that restricts the reconstruction to the space of sufficiently smooth functions. Using CMB, DESI BAO, Type Ia supernovae, CMB-ISW lensing cross-correlations, and large-scale 3x2pt DES Year 3 data, we find a $2.8\sigma$ hint for a non-minimal coupling. For the dark energy equation of state, our results indicate a preference for the existence of crossing of the phantom divide, $w_{DE}=-1$, at $z<0.8$. The non-minimal coupling effect stabilizes dark energy perturbations, providing a viable physical interpretation of the phantom crossing scenario. Our work paves the way for model-agnostic searches for signatures of modified gravity in cosmological data.

Interplanetary dust in the inner solar system originates from multiple sources, including short-period comets and main-belt asteroids. In this work, we focus specifically on the dynamical evolution of asteroid-derived dust using N-body simulations that incorporates solar gravity, planetary perturbations, radiation pressure, Poynting-Robertson drag and solar wind forces. We quantify dust fluxes for Mars, Venus and Mercury across an important mass range, which are essential inputs for ablation process on Mars/Venus and for contributing in the impact process on Mercury. We have also derived impact velocity distributions and compared with existing literature. In addition, we examine how close-encounter velocities depend on the orbital elements linking dust energetics directly to the orbital architecture of the dust population. Our results show that the calibrated asteroidal flux agrees excellently with the scaled Grün model for Mars (0.04 orders of magnitude offset) and Venus (0.09 orders), and with the Müller (2002) model for Mercury (0.04 orders). The velocity distributions reveal a decoupling between flux and impact velocity: low-eccentricity grains dominate the flux, while high-eccentricity grains control the high-velocity tail. These findings have direct implications covering: (i) For atmosphere-less bodies like Mercury, the high-velocity tail affects impact processes and exosphere generation; (ii) For Mars and Venus, the flux-dominated low-velocity population determines meteoroid ablation rates and metal layer formation; (iii) Our calibrated fluxes provide inputs for comparison with future observations from different missions and also, for modeling impact-driven surface modification across the inner solar system.

We present an update to the frequency analysis method for measuring the properties of a galactic bar. The method involves computing the fundamental frequencies of orbits in rotating, N-body-derived potential models, classifying the stars as members of bar supporting orbits, and finding the extent of the apo-centre distribution. In this work, we apply an updated classification criterion designed to isolate the so-called "Warm" inner Lindblad resonance (ILR) orbits. These orbits have been shown to contain the looped x1 orbits, which dominate the "shoulder regions" of the bar and largely contribute to the radial extent. We apply this method to existing Gaia, APOGEE, and OGLE data of more than 200,000 stars to constrain the properties of the Milky Way bar. We find that multiple bar lengths and pattern speeds are consistent with the data to within 5 percent.

The Galactic Centre gamma-ray excess (GCE) - an anomalous ~ 2-5 GeV Fermi-LAT signal around SgrA$^{\star}$ - has remained without a consensus interpretation for more than fifteen years. Dark-matter annihilation and unresolved millisecond-pulsar populations remain the leading candidates, yet neither incorporates the past activity of SgrA$^{\star}$ recorded by the Fermi and eROSITA bubbles (FEB). We propose a unified scenario in which both the GCE and the FEB are fossil imprints of a single past episode of SgrA$^{\star}$ activity: a precessing parabolic Blandford-Znajek jet launched from a tilted, magnetically arrested disc during a ~7.5 Myr active phase ending ~ 2.6 Myr ago. The jet both inflated the kpc-scale FEB and injected hadronic cosmic rays contributing to the GCE flux. The model rests on three independently motivated inputs: the EHT-proposed ~ $35^{\circ}$ tilt of the SgrA$^{\star}$ spin axis from the Galactic rotation axis, Lense-Thirring precession of the disc through ~5 azimuthal cycles during the active phase, and a two-zone cosmic-ray transport prescription through the CMZ and bulge with standard inner-Galaxy diffusion coefficients. Internal consistency is verified by checking that the proton Larmor radius confines cosmic rays to the jet column and that the gamma-ray optical depth toward the Galactic Centre is negligible. Comparison with current GCE observations yields a spin-dependent hadronic contribution: for the EHT-favoured SgrA$^{\star}$ spin a$^{\star}$ = 0.9, we find an irreducible hadronic floor of ~ 3-14% of the observed GCE surface brightness across the inner ten degrees, highlighting a previously unexplored component relevant for comprehensive models of the GCE.

We present a detailed chemical abundance analysis of the eclipsing binary system V505 Per. High resolution spectra were analyzed using the MOOG spectrum analysis code, and we determined abundances not only for iron and lithium but also for Si, Na, Ca, Mn, and Ni, elements that have not previously been analyzed in detail for this system. Abundances were computed across 15 temperature points using model atmospheres, with stellar parameters refined by minimizing abundance trends with excitation potential. We determined effective temperatures of T_eff = 6650 +/- 50 K for the primary and T_eff = 6550 +/- 50 K for the secondary, with iron abundances of [Fe/H] = -0.10 +/- 0.06 and [Fe/H] = -0.19 +/- 0.07, respectively. Most [X/Fe] ratios are consistent with solar values, though manganese is deficient. Our analysis of the effective temperatures shows that both stars lie on the hot edge of the lithium dip, consistent with Koenigsberger et al. (2025), which may help resolve the inconsistency noted of the stars lithium abundance within the dip by Baugh et al. (2013).

Cosmic voids provide a low-density environment where the scalar fifth force predicted by $\fR$ modified gravity (MG) is least screened. We present a semi-analytical calculation of the monopole, dipole, and quadrupole of the void-galaxy cross-correlation function $\xi^{s}(s,\mu)$ in redshift space for the Hu-Sawicki $\fR$ model ($n=1$), combining the scale-dependent growth factor from the scalaron degree of freedom with nonlinear spherical shell dynamics. The framework applies to any metric $\fR$ theory for which $\Geff(k,a)/G$ can be specified in the quasi-static limit. Our key results are: (1)~the monopole deviation from $\lcdm$ grows from $+2.8\%$ for large voids ($r_v = 30\;\Mpc$) to $+29.7\%$ for small voids ($r_v = 11.7\;\Mpc$) at $\fRz = 10^{-5}$ -- a distinctive size-dependent signature of the Compton-scale scalaron response associated with chameleon screening, with $\lambda_C \approx 8\;\Mpc$; (2)~nonlinear evolution amplifies the modified-gravity signal by $\mathcal{A}_0 \approx 4$, bringing it within reach of ongoing and upcoming wide-field spectroscopic surveys, such as DESI, Subaru PFS, Euclid, and the Roman Space Telescope; (3) the gravitational potential contains a finite-range Yukawa component, producing a radially dependent dipole signature that is complementary to the density and velocity multipoles; (4) the signal weakens with redshift as the scalaron Compton wavelength shrinks, but remains potentially detectable at Stage-IV spectroscopic void samples. We show that the void-scale transition in the modified-gravity response, the joint sensitivity to density, velocity, and fifth-force contributions, and the nonlinear amplification around void shells make redshift-space void-galaxy multipoles a powerful semi-analytical probe of f(R) gravity and related inhomogeneous dark energy scenarios.

We studied the properties of star formation and the characteristics of young stars in a quiet region located beyond the outskirts of the prominent star-forming cluster NGC 346 in the Small Magellanic Cloud (SMC). Utilising observations from the Hubble Space Telescope across the broad V and I bands, as well as the narrow Halpha band, we identified populations with ages of roughly 10, 60, 400 Myr and of 5 Gyr through isochrone comparison. We successfully identified 137 bona fide pre-main sequence (PMS) candidates exhibiting Halpha excess with a significance level of 5 sigma, accompanied by an Halpha line emission equivalent width exceeding 20 Å. Physical parameters for these PMS stars were determined, including mass, age, accretion luminosity, and mass accretion rate. Most PMS stars have an age around 16 Myr and an average mass of 0.80 \pm 0.16 M_sun. The median mass accretion rate for all 137 PMS stars is estimated to be about 8.0 x 10^(-9) M_sun/yr. While this rate is lower than that observed in the NGC 346 cluster itself, it is comparable with those measured for PMS stars in low-density star-forming regions in the SMC, despite the absence of apparent clustering and nebulosity. Furthermore, our analysis reveals that the ratios of accreting and non-accreting PMS stars to non-PMS stars and their mass accretion rate correlate with their distance from a group of hot massive stars in the vicinity. This suggests that the ultraviolet radiation emitted by these massive stars might erode the circumstellar discs of nearby PMS stars. Lastly, the overlap between our studied region and observations from the James Webb Space Telescope reveals that some of the identified PMS stars display near-infrared excess.

Cosmic bulk flow--the volume-averaged peculiar velocity of matter--serves as a fundamental test of the Cosmological Principle when probed on gigaparsec (Gpc) scales. Historically, however, measurements of cosmic bulk flow have been limited to $R\lesssim 100\ h^{-1}{\rm Mpc}$. We present an application of kinetic Sunyaev-Zel'dovich (kSZ) velocity reconstruction to constrain the bulk flow on cosmological scales, over a volume of effective radius $R\sim2000\ h^{-1} {\rm Mpc}$. We use the WISE$\times$SuperCOSMOS and unWISE galaxy catalogs, combined with CMB temperature maps from Planck to reconstruct large-scale velocities in six tomographic bins spanning $0.1\lesssim z \lesssim 1.5$. We place some of the tightest upper limits to date on bulk velocity at $200 \lesssim R\,[h^{-1}{\rm Mpc}]\lesssim 2000$, finding results fully consistent with the $\Lambda$CDM bulk flow expectation. Our unWISE constraints are in strong tension with the CatWISE quasar number-count dipole measurement if that dipole is due to a coherent bulk flow $\sim 370\ {\rm km\,s^{-1}}$ at $R\sim1000\ h^{-1}{\rm Mpc}$. We also derive constraints on the matter power spectrum at low-$k$ ($k\lesssim10^{-3}\, {\rm Mpc}^{-1}$) with low-$z$ ($z\sim 1$) galaxy samples. Alongside these cosmological constraints, we introduce a novel approach to map the optical depth bias--an inherent astrophysical degeneracy in kSZ velocity reconstruction--across different data combinations. Our work bridges the theoretical gap between bulk flow and kSZ-reconstructed velocities, and expands the horizon of bulk velocity measurements out to Gpc scales.

We present an automatic method based on machine-learning convolutional neural network (CNN) architecture to detect Lyman alpha emitters (LAE) hidden in the Data Release 1 spectroscopic dataset of the Dark Energy Spectroscopic Instrument (DESI). Those LAEs mostly have incorrect redshift estimations because the current DESI pipeline is not designed to detect and measure the redshifts of galaxies at $z>2$. To uncover those sources, we first visually inspect thousands of DESI spectra and construct a sample, consisting of both LAEs and non-LAEs, for training and testing the CNN-based model to (1) detect LAEs in DESI spectra and (2) determine their Ly$\alpha$ redshifts. The final model yields $95.2\%$ purity and $95.9\%$ completeness for detecting LAEs. We apply this model to approximately $2\times10^{6}$ spectra of sources targeted as emission-line galaxies and detect 19,685 LAEs from $z\sim2$ to $3.5$ within 12 minutes with a single GPU, illustrating the high efficiency of this model for identifying LAEs. The detected LAEs are mostly at the bright end of the luminosity function with Ly$\alpha$ luminosity $L_{\rm Ly\alpha} \gtrsim 10^{43}$ erg/s. The high signal-to-noise composite spectrum of the detected LAEs further shows various spectral features, including P-Cygni profiles of metal lines and MgII emission lines, possible indicators of Lyman continuum escape fraction, revealing the rich astrophysical information in this LAE sample. Finally, this sample can be used to train and validate the pipelines for redshift determination of LAEs for the preparation of the DESI-II survey.

We present results from the Big Mysteries Survey, a large-scale survey conducted through the American Physical Society's Physics Magazine on foundational and controversial topics in contemporary physics. The survey provides a snapshot of physicists' views on issues in cosmology, black-hole physics, quantum mechanics, quantum gravity, and anthropic coincidences. A central finding is that several positions often described publicly as field-wide ``consensus'' views are, in practice, supported by much narrower majorities or by pluralities rather than majorities.

We develop the Bogolyubov coefficient formalism for gravitational production of fermions with time-dependent mixing, which allows us to study a prototype neutrino system. The neutrino masses and mixings depend on the scalar field values, i.e. the Higgs or singlet scalar expectation values. These are time-dependent in the Early Universe and, due to de Sitter fluctuations, can reach very large values during inflation. As a result, gravitational production of all types of neutrinos can be much enhanced. We obtain an upper bound on the abundance of active and sterile neutrinos produced by classical gravity, $Y \lesssim 10^{-11}$.

Hints of cosmic microwave background polarization rotation ($\Delta\vartheta \sim 10^{-3}$ rad) are commonly attributed to late-time dynamics of ultralight axions. We show that such ultralight degrees of freedom are not required. Polarization rotation naturally arises as a geometric interface phase acquired when photons cross interfaces between topologically distinct dark sector vacua. The effect is a discrete phase shift fixed by the normalization of a wall-supported electromagnetic Chern--Simons interaction and protected by an emergent $1$-form symmetry of the low energy effective theory. This mechanism reproduces the familiar adiabatic rotation induced by light axion domain walls, but persists for arbitrarily thin walls where the axion is heavy or absent. In this regime the rotation manifests as a Pancharatnam phase localized at vacuum interfaces, independent of redshift and photon frequency below a natural ultraviolet cutoff. Cosmic birefringence thus emerges as a probe of vacuum structure in the dark sector, rather than of light-field dynamics.

We propose a novel broadband strategy to search for axions by leveraging observables controlled by the axion field squared. We present a practical implementation of this concept for probing the axion--photon coupling. This is done by operating a dc SQUID at the flux sweet spot, where the voltage depends quadratically on the magnetic flux, and using lock-in modulation to evade low-frequency noise. The proposed setup is ultra-broadband, spanning over 15 orders of magnitude in axion mass, with further expansion of the mass range possible. The projected sensitivity is $|g_{a\gamma\gamma}| \gtrsim 10^{-16} \text{ GeV}^{-1}$, orders of magnitude better than current bounds, and largely independent of axion mass. We discuss the sources of systematic background and a nulling technique to reduce them to an acceptable level. We also discuss how our strategy could be adapted to probe the axion-fermion coupling, as well as to detect other dark matter candidates such as dark photons.

Understanding stochastic inflation, and in particular the systematic computation of controlled corrections from first principles, remains an important open problem. In this work, we address this problem from two complementary perspectives. First, we derive the effective field theory governing long-wavelength modes from the reduced density matrix of a coarse-grained description. In this framework, locality in time follows from the thin-shell approximation, while locality in space is recovered dynamically in the super-Hubble regime. The resulting open effective field theory contains both dissipative and diffusive operators, with diffusion dominating as the coarse-graining scale is pushed into the infrared. This construction reproduces the usual Fokker-Planck equation at leading order and allows us to compute its corrections, including subleading contributions to the stochastic dynamics. Second, we study the evolution of the density matrix under changes of the coarse-graining scale. We show that this flow is governed by a Polchinski-type renormalisation group equation formulated directly for the density matrix. Dissipative and diffusive operators are generated dynamically along the flow, and the resulting effective action matches the Schwinger-Keldysh description. We derive a generalised Fokker-Planck equation directly from the renormalisation group flow, systematically incorporating subleading corrections and recovering the results obtained in the open effective field theory approach.

Purpose: Characterize superfluid-superconducting vortex states at arbitrary pressures with $T_{cp}\neq T_{cn}$, assuming both proton and neutron mean-fields are formed by spin-0 Cooper pairs. Method: The existing mean-field theory is extended to account for $T_{cp}\neq T_{cn}$. The pressure dependence of the pairing gap energy $\Delta_{\alpha0}$ is quantitatively established on the basis of the effective chiral field theory. To link $T_{c\alpha}$ with $\Delta_{\alpha0}$, I use the weak-coupling result $T_{c\alpha}\approx0.57\Delta_{\alpha0}$. A quadratic scaled-temperature ($T/T_{cp}$) dependence of the thermodynamic magnetic field is postulated in analogy with pure superconductors. The $T/T_{c\alpha}$-dependence of the gap $\Delta_{\alpha T}$ is inferred from the many-body approximations for the pure neutron matter. Results: An empirical $T/T_{c\alpha}$-dependence for the mean-field is constructed to account for the interplay between the condensation and the magnetic energies. The superfluid entrainment is found to increase the size of the vortex core and to decrease the effective magnetic penetration depth. The size of the neutron vortex core is found to be larger than the magnetic penetration depth in the outer core. Conclusions: The usual approximation of infinitely thin vortex line (the London's approximation) for the neutron vortex is found to be irrelevant in the entire outer core and for the proton vortex is found to be limited to vicinity of the crust-core transition. The developed mean-field theory paves the way to study the vortex microscopic structure, the angular momentum, the magnetization and the vortex-fluxtube interaction energy.

Modern gravitational wave astronomy relies on modeling tasks that often require months of graduate-level effort, including building fast waveform surrogates from expensive numerical relativity simulations, modeling orbital dynamics of black holes, fitting merger remnant properties and constructing template banks. These problems demand extreme precision to support detection and parameter inference, with state-of-the-art models achieving $\lesssim 10^{-4}$ relative error. We study whether state-of-the-art LLM coding agents can perform such end-to-end scientific modeling, where success requires constructing models with stringent accuracy criteria and reasoning about physical systems. We introduce gwBenchmarks, a suite of eight tasks grounded in gravitational wave analytic calculations and numerical simulations collectively representing over $10^8$ core-hours of compute. The tasks span interpolation, regression, and high-dimensional time-series modeling, requiring a combination of numerical methods, machine learning, and physics-informed approaches. In preliminary experiments, agents frequently relied on proxy metrics, partial evaluation, or fabricated results to spuriously complete tasks. We therefore implement an external pre-defined framework to gauge agent progress. Evaluating twelve coding agents, we find no consistent winner. On the easiest task, multiple agents converge to the same cubic spline solution, with one rediscovering a coordinate transformation widely used in the literature. On harder tasks like analytic waveform modeling, all agents fall 1-2 orders of magnitude short of domain requirements and exhibit systematic failures, including metric misuse, constraint violations, and result fabrication. Our code, data, and website are publicly available.

The population of compact binaries encodes information about their astrophysical origins and the expansion of the universe. Hierarchical Bayesian methods infer these properties by combining single-event posteriors. As catalogs grow, however, this approach becomes computationally expensive and is subject to increasing Monte Carlo uncertainty. We introduce Dingo-Pop, a simulation-based framework that infers population posteriors directly from gravitational-wave strain data. The data for each event are embedded into low-dimensional tokens and combined using a transformer trained on simulated catalogs subject to selection effects. This enables (i) population inference without per-event Monte Carlo sampling noise, (ii) amortization across variable catalog sizes using a single network, and (iii) end-to-end inference in about one second. We train a network for catalog sizes of 25 to 1000 events, and obtain well-calibrated posteriors consistent with traditional methods. By avoiding per-event analyses that can take hours to days, Dingo-Pop enables new classes of large-scale injection studies; as an application, we examine how spectral-siren Hubble constant uncertainties change with catalog size.

We compute the graviton absorption and emission rates by hydrogen atoms in line with the results obtained by Weinberg, Gould, Dyson and other authors. The spontaneous emission of gravitons by the hydrogen atoms has a tiny undetectable rate, while the absorption rate of gravitons is much higher and is proportional to the number of hydrogen atoms and to the graviton luminosity. The graviton luminosity of Sun, or a typical star, is induced by the scattering of electrons and protons in a completely ionised hydrogen plasma at the core of the Sun and their energies are in the eV to keV range. We suggest measuring the excess in the ratio of the photon luminosities from interstellar hydrogen atoms that is induced due to the absorption of gravitons. The excess in the ratio of photon luminosities would indicate the presence of gravitons.

We develop a potential-independent cosmographic framework, in which cosmographic parameters are promoted to dynamical variables within a closed autonomous system. Although the cosmographic hierarchy is formally infinite, we achieve closure by mapping potential slow-roll parameters onto the kinematic phase space within General Relativity with a minimally coupled scalar field. Within this framework, we perform a stability analysis and show that inflationary (quasi-de Sitter) solutions arise as natural attractors, while stiff-fluid configurations act as repellers without invoking the slow-roll approximation. To describe the transition to standard Big Bang evolution, we extend the system to include a radiation component and a phenomenological decay term. This leads to a generalized, potential-independent description of reheating characterized by an effective equation of state $w_{\rm eff}$. We demonstrate that the radiation-dominated phase is the late-time attractor of the extended system. These results provide a unified kinematical description of the expansion history from inflation through reheating, bridging cosmography and scalar field dynamics.

Dynamic alignment in magnetohydrodynamic (MHD) turbulence is usually interpreted as a cascade-wide tendency of Elsasser increments to become increasingly collinear at smaller scales. We argue instead that the standard measurements mainly detect a conditional survival effect of intense events. In high-resolution Johns Hopkins MHD simulations, the typical folded Elsasser-increment angle remains only modestly below the random-orientation baseline and shows no evidence for a rigid, monotone, volume-filling ordering of the cascade. Much smaller angles appear primarily in the strongest Elsasser-amplitude events, while conditioning on current density leaves the angle close to its unweighted behavior. Shuffled-null tests show that this reduction is caused by a genuine negative covariance between event amplitude and angular misalignment, not by weighting alone. Cross-scale angular correlations are measurable but decaying, indicating partial and non-rigid persistence of the local alignment field. A finite-time state-retention test directly supports the proposed mechanism: high-amplitude large-angle events leave their amplitude--angle sector faster than high-amplitude small-angle events, while incoming transitions continually replenish the large-angle sector. NASA Wind solar-wind observations show the same angle--amplitude hierarchy and negative covariance in Taylor-sampled Elsasser increments. These results indicate that dynamic alignment, as measured by conventional weighted diagnostics, is best understood as selective sampling of longer-lived intense small-angle events, not as a cascade-wide alignment of typical MHD fluctuations.

Large curvature perturbations generated during slow first-order phase transitions are a promising source of primordial black holes. However, recent analyses suggested that the mechanism is ruled out once the density contrast and the formation threshold are evaluated in the same gauge. In this work, we show that this mechanism remains viable: after a supercooled transition, reheating can be sufficiently slow that the Universe enters an early matter-dominated era, during which even small overdensities grow and collapse into primordial black holes. An interesting feature of this scenario is that the black holes are produced with large spins.

Over the past two decades, the rapid surge in data-intensive computational techniques for statistical modeling may have had the effect of diminishing the use of applied mathematics in causal scientific inquiry. In this paper, co-authored by an astrophysicist, a mathematician, and philosophers, we assess the hazards of neglecting the branch of mathematics that constructs models to address causal questions in favor of statistical modeling alone. Causality is relevant in all branches of science and is often elucidated through applied mathematics. Here, we illuminate the idea with examples drawn from space physics and medical sciences. We examine causal questions to demonstrate how applied mathematical and statistical methods may differentiate between two fundamental facets of causality, i.e., mechanistic and difference-making. Understanding such foundational differences in causality may, in some cases, help explain discrepant or erroneous research results. Most importantly, understanding the relationship between causality and analytical approaches used in science has the potential to strengthen the rigor and reliability of scientific inquiry through optimal selection of mathematical and/or statistical methods.

GW240925 and GW250207 are two loud gravitational-wave signals from binary black hole coalescences observed with network signal-to-noise ratios $\sim 32$ and $\sim 69$, respectively, by the LIGO Hanford--LIGO Livingston--Virgo network. Gravitational-wave signals from coalescing binaries have characteristic phase and amplitude evolution predicted by general relativity. These signal waveforms, together with measured instrumental calibration uncertainties, are used to infer source parameters. However, for sufficiently loud detections it is possible to constrain the calibration of the detectors directly using the signals themselves. We present the first informative astrophysical measurements of gravitational-wave detector calibration. For GW240925, we verify the inference of Hanford calibration from the astrophysical signal through cross-checks with known calibration errors obtained from in-situ measurements. At the time of GW250207, the Hanford detector was not fully stabilized, leading to elevated calibration uncertainties; thus, astrophysical calibration is essential to obtain accurate data and to enable source localization. These well-localized, high signal-to-noise observations have the potential to offer precise measurements of source properties, stringent tests of general relativity, and informative dark siren measurements, provided that calibration uncertainties are properly incorporated. As detector sensitivity improves, astrophysical calibration will become an increasingly valuable complement to in-situ calibration measurements. Obtaining accurate calibration will be essential for precision gravitational-wave science.

Advanced adaptive optics (AO) systems can use Fourier-type wavefront sensing to correct optical distortions encountered in ground-based telescopes, AO-assisted retinal imaging, and free-space optical communications (FSOC). Recently, a novel Fourier-type wavefront sensor (WFS) known as the iQuad WFS has been introduced. Its design features a focal plane tessellation with a four-quadrant phase mask (FQPM) that incorporates a $\pm \pi/2$ phase shift between adjacent quadrants. In this work, we establish a comprehensive mathematical framework for the iQuad WFS, including its forward models and linearizations based on the Fréchet derivative. We reveal a connection between the iQuad WFS and the 2d finite Hilbert transform and demonstrate that the linear iQuad WFS operator is self-adjoint - a unique property among Fourier-type WFSs. Additionally, we introduce the double iQuad WFS, a two-path configuration that combines two rotated iQuad WFSs. This design addresses the limitations of the single iQuad WFS by suppressing poorly-seen phase components. Moreover, the double setup simplifies the mathematical modeling. We also highlight iQuad similarities to the widely used pyramid wavefront sensor (PWFS). Finally, we extend the concept of modulation to the iQuad WFS, further enhancing its versatility. The theoretical analysis presented here lays the groundwork for the development of fast and robust model-based wavefront reconstruction algorithms for the iQuad WFS, paving the way for future applications in AO instruments.

We show that the dissipation of small-scale perturbations through diffusion damping after neutrino decoupling lowers the present-day neutrino temperature compared to the expected value of $1.96\,{\text{K}}$. This reduces the relic neutrino abundance by an amount controlled by the integral of the primordial curvature power spectrum $\Delta_{\cal R}^2(k)$. We find that a relic neutrino detection by PTOLEMY can set limits $\Delta_{\cal R}^2(k) \lesssim {\cal O}(0.1)$ on scales $k \lesssim 3 \times 10^5\,{\text{Mpc}^{-1}}$, complementary to limits from Big Bang Nucleosynthesis, spectral distortions, pulsar timing arrays, and future dark ages 21-cm observations.

Dynamical systems techniques are a powerful tool to analyse systems of ordinary differential equations, written in an appropriate form. For a given theory of gravity, the cosmological field equations typically lead to a system of ordinary differential equations. Casting these cosmological equations into the form of a dynamical system requires a careful choice of the dynamical variables. Despite this being a critical step, relatively little is said about this process in the literature. We discuss how different variable choices affect the information that can be extracted from the Friedmann equations. We begin by reviewing the standard cosmological model with dark matter, radiation, and dark energy, and include quintessence models. We revisit well-known models with an exponential potential using new variables. This discussion is then extended to models with scalar fields and more intricate coupling terms.

We present the results of a large number of simulation studies regarding the power of various goodness-of-fit as well as non-parametric two-sample tests for multivariate data. In two dimensions this includes both continuous and discrete data, in higher dimensions continuous data only. In general no single method can be relied upon to provide good power, any one method may be quite good for some combination of null hypothesis and alternative and may fail badly for another. Based on the results of these studies we propose a fairly small number of methods chosen such that for any of the case studies included here at least one of the methods has good power. The studies were carried out using the R packages MD2sample and MDgof, available from CRAN.

The OH$^+$ ($X ^3\Sigma^-$) radical cation has been investigated by combining a 4 K 22-pole ion trap apparatus with high-resolution IR and THz radiation sources. Applying different types of action spectroscopic methods, the fundamental vibrational band in the 3 $\mu$m range and the spin manifold of the $N=1 \leftarrow 0$ rotational transition around 1 THz have been extended and refined. Additionally, the spin manifold of the $N=2 \leftarrow 1$ rotational transition, scattered around 2 THz, has been measured for the first time with microwave accuracy. Although all hyperfine components of the pure rotational transitions are affected by considerable Zeeman splittings, a simulation of their contours allowed us to extract the field-free center frequencies with high accuracy. A global fit combining rovibrational and pure rotational transitions from the literature with those newly obtained in this work was performed, leading to improvements in the spectroscopic constants of OH$^+$, particularly those in the ground vibrational state.

Basilisk is an open-source astrodynamics simulation framework widely used for spacecraft guidance, navigation, and control (GN&C) research and development. Despite its flexibility and computational capabilities, configuring Basilisk consistently across heterogeneous development environments presents practical challenges due to dependency management, operating system compatibility, and software configuration requirements. This paper presents a Docker-based containerization workflow for Basilisk that encapsulates the complete build environment, dependencies, and simulation infrastructure within a portable container image. The workflow is demonstrated through a progression of simulation scenarios of increasing complexity, from standalone orbital dynamics scripts to BSKSim-based attitude dynamics and control simulations with Monte Carlo analysis. The BSKSim class hierarchy, dynamics model architecture, flight software implementation, and scenario execution patterns are described in detail. The presented workflow provides a self-contained implementation reference for GN&C engineers and researchers seeking reproducible and portable Basilisk simulation environments. This work expands upon a workshop presentation delivered at the 46th Rocky Mountain AAS GN&C Conference, February 2024, available at this https URL.