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Physics Astrophysics

astro-ph Watch Astrophysics

Tuesday 28 April

High Energy Astrophysical Phenomena

The GMRT High-Resolution Southern Sky Survey for pulsars and transients – VIII: Orbital Variability and the Evolution of a 1-Day He-WD Millisecond Pulsar J2101-4802

Ankita Ghosh, Bhaswati Bhattacharyya, David L. Kaplan et al. (+8 more)

We present timing and orbital phase-resolved polarimetry of the millisecond pulsar (MSP) J2101$-$4802, having a spin period of 9.48~ms and dispersion measure (DM) $25.05\ \mathrm{pc\ cm^{-3}}$ discovered with the Giant Meter Radio Telescope (GMRT). From the phase-connected timing of this MSP spanning 3.7 years, we identify that PSR J2101-4802 is in a $\sim$1-day binary orbit with a likely helium-white-dwarf (He-WD) companion having a median companion mass of $\simeq0.15\, M_\odot$, consistent with canonical recycling in the Galactic field. The timing solution further reveals an unusually large orbital period derivative, $\dot{P}_b$ ($\sim10^{-11}\,{\rm s\,s}^{-1}$), compared to typical Galactic-field MSP–HeWD binaries, which cannot be explained by the contributions from kinematic effects (Shklovskii and Galactic acceleration) or general-relativistic damping. Using wideband, full-Stokes observations, we also trace the linear and circular polarization variation across the orbital phase and fit a rotating-vector model (RVM) to its position-angle swing across the pulse phase, yielding constraints on the emission geometry (magnetic inclination and impact angle) of this system. The combination of a $\sim$1-day orbit, $\sim0.15\,M_\odot$ companion, modest spin-down power, unusually large $\dot{P}_b$, and phase-locked magnetized intrabinary plasma signatures suggests that PSR~J2101$-$4802 represents a transitional system linking redback-like spiders to detached He–WD MSP binaries.
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All authors Ankita Ghosh, Bhaswati Bhattacharyya, David L. Kaplan, David A. Smith, Andrew Lyne, Jayanta Roy, Laila Vleeschower, Gabriella Agazie, Lankeswar Dey, Sangita Kumari, Ujjwal Panda

Earth and Planetary Astrophysics

Disc lifetime distribution as a function of the mass of host star

Susanne Pfalzner, Furkan Dincer, Nienke van der Marel et al. (+1 more)

The lifetime of protoplanetary discs is a critical factor for planet formation. Although the mean disc lifetime provides an estimate of the typical period available for planet formation, it does not capture the substantial variability in individual disc lifetimes or their dependence on host star mass. This study addresses these limitations by deriving the disc lifetime distribution as a function of stellar mass. Our results reveal a pronounced mass-dependence. Performing a phenomenological fit using a Weibull distribution, we find the maxima of the distributions at $t_{max}^H =$3.72 Myr for high-mass stars ($\approx$ 1.00–3.00 $M_{\odot}$) and $t_{max}^L =$ 7.20 Myr for low-mass stars ($\approx$ 0.01–0.20 $M_{\odot}$) assuming an initial disc fraction of $f_{init} = 0.8$. All distributions are broad (typically 3.2 Myr $< \sigma <$ 4.7 Myr), with the distribution for low-mass stars being somewhat broader. Our analysis indicates that not all stars are initially surrounded by a disc (60% $< f_{init} <$ 90% at cluster zero age), and that the initial disc fraction is even lower ($f_{init} \approx$ 40%) for higher-mass stars. The potential mechanisms responsible for the observed spread and mass-dependence of disc lifetime distributions and initial disc fractions are discussed. Our primary aim is to demonstrate the methodology; more robust constraints will require improved data on mass-dependent disc fractions. Nevertheless, the derived mass-dependent disc lifetime distributions can already serve as a valuable input or a benchmark for planet-formation synthesis models.
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All authors Susanne Pfalzner, Furkan Dincer, Nienke van der Marel, Frank W. Wagner

Earth and Planetary Astrophysics

Oxygen Isotopic Compositions of Chondrules as Probes of Solar Protoplanetary Disk Formation

Sota Arakawa, Takayuki Ushikubo and Ryosuke T. Tominaga

Chondrules are thought to have formed during transient flash-heating events in dust-enriched regions of the solar protoplanetary disk. Although laboratory studies have characterized the oxygen isotopic compositions of chondritic materials, quantitative interpretations based on simulations of disk formation and evolution remain limited. Here, we perform one-dimensional simulations of disk formation and evolution by solving a diffusion–advection equation with mass infall from the parental cloud core. We compute the temporal evolution of oxygen isotopic compositions using an experimentally derived isotope-exchange model. We examine how the oxygen isotopic signatures of the disk depend on the radial distribution of infalling material and the composition of the parental cloud core. We find that the oxygen isotopic compositions of carbonaceous-chondrite chondrules can be reproduced if either (i) the radial extent of mass infall onto the disk is moderate ($\sim 10~{\rm au}$), or (ii) it is large ($> 10~{\rm au}$) and the parental cloud core was ice-depleted and/or experienced weaker CO self-shielding than is commonly assumed. We further suggest the scenario that the observed bimodal trends in oxygen isotopic composition and redox state reflect the partial escape of H$_{2}$O vapor from chondrule-forming regions during heating. In contrast, if ordinary-chondrite chondrules formed inside the snow line under background temperatures of $\lesssim 500~{\rm K}$, their oxygen isotopic compositions may be difficult to explain within the present disk-evolution model, because oxygen isotopic exchange between silicates and vapor species proceeds efficiently only in the inner disk at $T \gtrsim 500$–$600~{\rm K}$.
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Earth and Planetary Astrophysics

Revealing a Systematic High-latitude Current Sheet at Jupiter

Yan Xu, Zhonghua Yao, Frederic Allegrini et al. (+7 more)

Based on models derived from Earth's magnetotail, other planets with dipole magnetic fields, including Mercury, Jupiter, and Saturn, were expected to possess similar magnetotail configurations. In this traditional picture, the majority of plasma is confined near the magnetic equator within a plasma sheet (or plasma disc), whereas higher-latitude regions feature strong magnetic fields that are open to the solar wind, forming magnetospheric lobes. However, auroral observations and recent simulations have shown that Jupiter's magnetic topology differs markedly from this picture, particularly in its high-latitude regions where magnetic field lines are predominantly closed. This discrepancy calls for a re-examination of high-latitude magnetospheric structure at Jupiter. Here, using Juno measurements acquired between 2016 and 2022, we show that Jupiter's nightside high latitudes host a persistent current-sheet-like structure above about 40 degrees magnetic latitude near midnight. This structure contains internally sourced oxygen and sulfur ions and exhibits azimuthal magnetic signatures opposite to the bend-back of the equatorial current sheet. These findings indicate that the canonical picture of planetary magnetotail architecture requires revision. Our results provide new insight into the architecture of rapidly rotating magnetospheres and offer a framework for interpreting magnetospheric structures at exoplanets.
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All authors Yan Xu, Zhonghua Yao, Frederic Allegrini, Shengyi Ye, Binzheng Zhang, Zhili Zeng, Enhao Feng, Jiuwen Sun, William Dunn, Scott Bolton

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th

Simple Analytical Solutions of the Wheeler-DeWitt Equation in the Classical Hamilton-Jacobi Limit

Naoto Maki, Chia-Min Lin and Kazunori Kohri

We investigate the Wheeler-DeWitt equation for a flat, homogeneous, and isotropic Universe containing a canonical scalar field with a potential. We show that under the constraint $|\Psi|=1$, where the Wheeler-DeWitt equation exactly becomes the classical Hamilton-Jacobi equation, the form of the potential is completely determined depending on the value of the operator ordering parameter. Furthermore, we demonstrate that the classified potentials admit simple forms, such as the exponential, quadratic with a negative cosmological constant, and cosine-type potential with a negative cosmological constant. Several of these have already been explored in the context of inflation or dark energy. Finally, focusing on the system with the cosine-type potential and a negative cosmological constant in the classified potentials, we derive the analytical solutions for the scale factor and the scalar field and discuss the cosmological implications.
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Astrophysics of Galaxies

Spectral Evolution and Transient Broad-Line Features in the Isolated AGN UNAM-KIAS 613

Edgar Cortes-Suárez, Paola Marziani, Héctor Manuel Hernández-Toledo et al. (+2 more)

We present multi-epoch optical spectroscopy of the isolated elliptical galaxy UNAM-KIAS 613, hosting a low-luminosity Type 1 AGN. Analysis of archival Sloan Digital Sky Survey (SDSS) data from 2006 reveals a distinctive double-peaked broad H$\alpha$ profile, tentatively modeled by a relativistic accretion disk. Follow-up observations in 2018 and 2023 show the disappearance of the red and blue wings, leaving only a single-peaked, central broad component. No significant continuum variability is detected in ASAS-SN and Catalina light curves over 2012-2025, and multi-wavelength data (radio, mid-IR, X-ray) confirm a sub-Eddington, radio-quiet AGN (Eddington ratio $\approx$0.03-0.04, black hole mass $\approx$10$^{7.2}$ M$\odot$). We propose that the double-peak structure is in reality transient, and arose from a one-time bipolar outflow event rather than a stable disk or from a Tidal Disruption Event. The mid-IR SED and radio luminosity place UK 613 on the boundary between AGN and star formation dominance, suggesting residual star formation, while we have found that the isolated environment seems to be prone to the rejuvenation of ellipticals by recent ($\lesssim$ 1 Gyr) cold gas. We also examined its location within the cosmic web with the aim of identifying possible distinctive effects imprinted on its spectroscopic properties. Ultimately, our results are consistent that UNAM-KIAS 613 might have under gone a ”turn-off” of the accretion disk emitting region or a transition between a radiatively-inefficient and radiatively-efficient accretion mode, and highlight the complex interplay of disk, outflow, host processes and environment in low-accretion, low-black hole mass AGNs, an AGN population still largely unexplored to-date.
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All authors Edgar Cortes-Suárez, Paola Marziani, Héctor Manuel Hernández-Toledo, Miguel Ángel Aragón-Calvo, Castalia Alenka Negrete

Instrumentation and Methods for Astrophysics · Cross-listed from cs.CV

Towards Seamless Lunar Mosaics: Deep Radiometric Normalization for Cross-Sensor Orbital Imagery Using Chandrayaan-2 TMC Data

Pratincha Singh, Jai Gopal Singla, Prashant Hemrajani et al. (+3 more)

Radiometric inconsistencies remain a major challenge in generating seamless lunar mosaics from multi-mission orbital imagery due to variability in illumination geometry, sensor characteristics, and acquisition conditions. This paper presents a deep learning-based radiometric normalization framework for multi-mission lunar mosaics constructed primarily from ISRO's Chandrayaan-2 Terrain Mapping Camera (TMC) data, supplemented with auxiliary imagery from the SELENE (Kaguya) mission. The proposed approach employs a conditional generative adversarial network (cGAN) comprising a U-Net-based generator and a PatchGAN discriminator to learn a nonlinear radiometric mapping from conventionally mosaicked lunar imagery to a photometrically consistent reference derived from LROC Wide Angle Camera (WAC) data. A patch-based training strategy with overlap-aware inference is adopted to enable scalable processing of large-area mosaics while preserving structural continuity across tile boundaries. Quantitative evaluation using Structural Similarity Index (SSIM), Peak Signal-to-Noise Ratio (PSNR), and Root Mean Square Error (RMSE) demonstrates consistent improvements over traditional histogram-based normalization techniques. The proposed framework achieves enhanced tonal uniformity, reduced seam artifacts, and improved structural coherence across multi-source lunar datasets. These results highlight the effectiveness of learning-based radiometric normalization for large-scale planetary mosaicking and demonstrate its potential for generating high-fidelity lunar surface maps from heterogeneous orbital imagery.
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All authors Pratincha Singh, Jai Gopal Singla, Prashant Hemrajani, Nitant Dube, Amithabh, Hinal Patel

Cosmology and Nongalactic Astrophysics

Multi-tracers, multi-surveys: a joint Fisher analysis of DESI+PFS

Nhat-Minh Nguyen

Marginalizing over 11 effective-field-theory (EFT) nuisance parameters per tracer per redshift bin degrades cosmological precision in one-loop analyses of galaxy power-spectrum multipoles in redshift space. Simulation-based priors (SBP) tighten these parameters but rely on N-body simulations and halo-occupation-distribution (HOD) models. We consider a multi-tracer Fisher analysis as a complementary approach: auto- and cross-power spectra jointly constrain cosmology, galaxy bias and stochasticity through two channels – within a survey and across overlapping surveys – combined in a volume-partitioned joint Fisher analysis. We forecast across the $14{,}000\;\mathrm{deg}^2$ Dark Energy Spectroscopic Instrument (DESI) footprint, including the $\sim\!1{,}200\;\mathrm{deg}^2$ Prime Focus Spectrograph (PFS) overlap at $z\in[0.6,1.6]$ with up to 4 tracers (PFS-ELG, DESI-ELG, DESI-LRG, DESI-QSO). We vary a common $\ln(10^{10}A_s)$, $M_{\nu}$ and ${\Omega}_m$, holding $h$, ${\omega}_b$ and $n_s$ fixed. Adding internal-DESI cross-spectra to DESI auto-spectra reduces the errors on the derived $f{\sigma}_8(z=1.1)$, $M_{\nu}$ and ${\Omega}_m$ by 7.1%, 3.5% and 3.8%, respectively, at $k_{\rm max}=0.20\,h\,\mathrm{Mpc}^{-1}$. Adding PFS auto- and cross-spectra to this complete DESI multi-tracer analysis further tightens these errors by 3.8%, 2.6% and 3.2%, respectively, after marginalizing over residual cross-population stochasticity. The clustering likelihood alone constrains the linear and quadratic biases and the shot noise. For these parameters it provides a complementary test of inference using SBP, while the counterterms remain weakly constrained. The framework extends to any number of overlapping spectroscopic surveys.
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Astrophysics of Galaxies

The Impact of Elliptical Broad-Line Regions on Reverberation-Based Black Hole Mass Estimates

Jiancheng Wu, Haicheng Feng, Qingwen Wu et al. (+1 more)

The virial factor $f$ is critical for accurate supermassive black hole (SMBH) mass measurements using reverberation mapping (RM) and the radius–luminosity ($R$–$L$) relation, yet its value remains highly uncertain. While traditional models assume axisymmetric broad-line region (BLR) geometries, growing evidence suggests that BLRs may possess more complex, asymmetric structures. We systematically investigate the impact of elliptical-disk BLR geometries on SMBH mass determinations through comprehensive numerical simulations. By computing emission-line profiles, emissivity-weighted time lags, and the corresponding virial factor $f$ over a wide range of eccentricities, orientations, and inclinations, we find that even in purely virialized systems, geometric effects alone can cause $f$ to vary by more than an order of magnitude and can mimic observational signatures typically attributed to radiation pressure. Additionally, local broadening introduces further systematic uncertainties in velocity width measurements, biasing $f$ by up to a factor of $\sim$3. Asymmetric BLR configurations also induce a scatter of $\sim$0.18 dex in the $R$–$L$ relation due to projection effects, comparable to the intrinsic scatter observed in RM studies. These results challenge the conventional attribution of RM uncertainties to non-virial motions or radiation pressure, and instead highlight the fundamental role of BLR geometry in SMBH mass measurements.
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All authors Jiancheng Wu, Haicheng Feng, Qingwen Wu, Xinwu Cao

Astrophysics of Galaxies

Constraining the nature of active galactic nuclei through circumgalactic Lya emission at z=2-3

Shiwu Zhang, Zheng Cai, Fabrizio Arrigoni Battaia et al. (+8 more)

We present a comprehensive analysis of circumgalactic Lya nebulae around 59 unobscured and 26 obscured quasars at z=2-3, observed with the Keck Cosmic Web Imager (KCWI), to constrain the nature of active galactic nuclei (AGN) at cosmic noon. We find that Lya nebulae around unobscured quasars are significantly less symmetric having a symmetry parameter of a_w=0.2-0.6 and more spatially extended having a scale length of r_h=10.7+/-0.5 kpc than those around obscured quasars (a_w=0.6-0.8; r_h=6.6-7.7 kpc).Unobscured quasars also exhibit steeply declining velocity dispersion profiles with the slope of -4.3+/-0.4 km s^-1 kpc^-1, indicative of large-scale outflows, whereas obscured quasars display flat profiles (-0.2+/-0.7 and -0.6+/-0.4 km s^-1 kpc^-1). The degree of quasar obscuration appears to be intrinsically linked to nebular asymmetry and extent, a relationship that could be in tension with the standard orientation-based AGN unified model, as it expects unobscured-quasar nebulae to be more symmetric and compact. These results naturally fit the evolutionary scenario, where AGN feedback drives a transition from an obscured to an unobscured phase-progressively redistributing gas to larger radii, introducing anisotropy, and driving turbulence. Taken together, our findings favor the evolutionary scenario over the purely orientation-based unified model for quasars at cosmic noon.
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All authors Shiwu Zhang, Zheng Cai, Fabrizio Arrigoni Battaia, Sebastiano Cantalupo, Mingyu Li, Ben Wang, Yuduo Guo, Aura Obreja, Haibin Zhang, Zihao Li, Donghui Quan

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Gauge Theoretic Signal Processing II: Zero-Latency Whitening for Early Warning Pipelines

James Kennington, Joshua Black, Zach Yarbrough et al. (+9 more)

Low-latency gravitational-wave search pipelines provide early-warning alerts for multimessenger astrophysical transients. Current pipelines whiten the data stream using acausal, linear-phase filters, which require a look-ahead buffer that introduces several seconds of algorithmic latency. Eliminating this latency requires causal, minimum-phase whitening filters using only past data. However, operating causal filters under non-stationary noise is non-trivial: the drifting power spectral density must be tracked without degrading the matched-filter signal-to-noise ratio (SNR), filter updates must preserve the minimum-phase condition, and the altered phase response must be compensated to maintain sky-localization accuracy. In Paper I we introduced a gauge theoretic signal processing framework and showed that the minimum-phase connection on the manifold of power spectra provides a geometrically exact update rule for causal filters. Here we validate that framework numerically and operationally, demonstrating that parallel transport along this connection strictly preserves the minimum-phase property while exactly conserving the matched-filter SNR. We numerically certify the flatness of this connection, showing that the optimal filter is a path-independent state function of the instantaneous noise. Through an injection campaign on O3 data with 15,347 binary black hole signals across the LIGO-Virgo network, we confirm that this architecture preserves the detection sensitivity and inter-detector timing and phase accuracy of the linear-phase baseline. Implementing the framework in the production sgnl pipeline reduces whitening latency by 1.0 s (33%) at a 4-second noise estimation cadence, confirmed in controlled tests and on live O3 replay data at production scale. Stride reduction experiments show that up to 91% of baseline trigger latency can be eliminated with sub-second pipeline cadence.
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All authors James Kennington, Joshua Black, Zach Yarbrough, Yun-Jing Huang, Chad Hanna, Leo Tsukada, Amanda Baylor, Olivia Godwin, Prathamesh Joshi, Cody Messick, Surabhi Sachdev, Ron Tapia

Earth and Planetary Astrophysics · Cross-listed from physics.geo-ph

A magnetotelluric image of the Curnamona Province and the adjacent Delamerian Orogen margin: new insights into the crustal architecture

Wenping Jiang, Michael Doublier, Russell Korsch et al. (+4 more)

We have used new magnetotelluric data collected in the Curnamona Province and the adjacent part of the Delamerian Orogen margin to image electrical conductivity structures and to inform the understanding of the crustal architecture within the regional geological context. The preferred 3D resistivity model confirms, and resolves in greater detail, crustal-scale conductive features that have been mapped by the long-period data collected at half-degree spacing as part of the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP), that is, the prominent Curnamona Province Conductor and the two Nackara Arc conductors. The new model reveals that the eastern Nackara Arc (ENAC) conductor continues as the Broken Hill Conductor (BHC) into the Curnamona Province. Regional geological considerations suggest that its formation is possibly linked to rifting/extension in the early Cambrian. Although we recognise that the east-west trending Wilcannia Conductor could be a possible continuation of the ENAC-BHC zone, integration with recently acquired deep seismic reflection data and evaluation of the geological setting lead us to suggest that they are not genetically linked. We suggest that the Wilcannia Conductor is younger and most likely is related to late Delamerian (~500 Ma) or Siluro-Devonian magmatism. Finally, these conductivity anomalies may represent large-scale trans-crustal structures that control the emplacement of low volume alkaline ultramafic magmas, and show a spatial relationship with certain mineral deposit types, suggesting a possible control on the distribution and formation of metallogenic provinces/belts in the region. This will be further investigated in future work.
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All authors Wenping Jiang, Michael Doublier, Russell Korsch, Andy Clark, Malcolm Nicoll, Adrian Hitchman, Yanbo Cheng

High Energy Astrophysical Phenomena

Non-Monotonic Rotation Imprint on Time-Integrated Neutrino Spectral Moments in a 15\,$M_\odot$ Core-Collapse Supernova Sequence

Nicolas Viaux

We study the early post-bounce neutrino signal of the published Garching $15\,M_\odot$ rotating core-collapse supernova (CCSN) sequence consisting of non-rotating (NR), slowly rotating (SR, $\Omega_0=0.5$ rad\,s$^{-1}$), and fast-rotating (FR, $\Omega_0=150$ rad\,s$^{-1}$, artificially boosted ${\sim}300{\times}$) three-dimensional models. We present a new analysis of these publicly available simulation data; no new simulations were performed. Our central result, for this specific model sequence, is that SR and FR shift the integrated spectral moments in opposite directions relative to NR: FR drives the spectra toward softer, more-pinched states, while SR moves them weakly toward harder, less-pinched states. Placed in a spectral-shift plane $(\Delta\langle E\rangle_L,\,\Delta\alpha_L)$, NR sits at the origin, and SR and FR occupy diagonally opposite quadrants, making the non-monotonic response immediately visible as an anti-correlation in two spectral dimensions simultaneously. The focus is the accretion interval $t_{\rm pb}=0.05$–$0.30$\,s, where the rotation imprint is strongest. Quantitatively, fast rotation produces $\Delta\langle E_{\nu_e}\rangle_L=-0.513$\,MeV and $\Delta\alpha_{\nu_e}=+0.161$, with corresponding shifts $\Delta\langle E_{\bar\nu_e}\rangle_L=-0.440$\,MeV and $\Delta\alpha_{\bar\nu_e}=+0.173$; the SR shifts are an order of magnitude smaller and in the opposite sense. The fast-rotation signature is coherent across all $15\,488$ lines of sight and is established during early accretion. With only three models from a single progenitor family, this result is a phenomenological characterization of one published sequence and a suggestive indication of a non-monotonic, possibly strongly nonlinear, rotational response within this sequence; the functional form and generality of the dependence on $\Omega_0$ remain unconstrained.
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Monday 27 April

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Strong-field signatures of a regular black hole in an Einasto dark matter halo

Mohsen Fathi and Faizuddin Ahmed

We investigate the strong-field phenomenology of a static and spherically symmetric regular black hole supported by an Einasto dark matter (DM) distribution. For the exponential Einasto profile, the geometry is controlled by a single dimensionless halo parameter $a$, and we restrict the analysis to the black hole branch $0<a\leq a_{\rm crit}\simeq0.388$. We study both timelike and null geodesics, including the effective potential, circular orbits, ISCO radius, orbital period, periapsis advance, photon sphere, shadow radius, effective photon force, and representative photon trajectories. We also construct image-plane intensity profiles and face-on thin-disk images in a static-emitter approximation. The analysis reveals a hierarchy of strong-field sensitivity. Timelike observables remain largely degenerate with the Schwarzschild limit along most of the black hole branch, while the photon sphere scale, shadow diameter, and residual optical structures provide the most sensitive response to the Einasto halo near the critical black hole regime. A comparison with the EHT shadow-scale measurements shows that the full branch is consistent with Sgr A* at the $1\sigma$ level, whereas M87* mildly disfavors values very close to criticality. These results indicate that the most promising signatures of the Einasto halo are not expected from ordinary timelike orbital quantities, but from near-critical photon propagation and its imprint on the optical appearance.
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Solar and Stellar Astrophysics

V446 Cephei: a $\beta$ Cep pulsator in a multiple system

A. Moharana, J. Southworth, K. Pavlovski et al. (+7 more)

$\beta$ Cep stars in eclipsing binary (EB) systems give us an opportunity to put observational constraints on their structure and stellar parameters. We present a comprehensive analysis of the $\beta$ Cep star in the EB V446 Cep, using TESS photometry and HERMES spectra. We calculate the stellar and orbital parameters using light curve modelling and spectral disentangling. The EB has an orbital period of $3.808567 \pm 0.000012$ d and a mass ratio of $0.1550 \pm 0.0012$. We find the $\beta$ Cep star to have a mass of $10.68 \pm 0.06$ $\mathrm{M_{\odot}}$, a radius of $5.864 \pm 0.033$ $\mathrm{R}_{\odot}$, and a $T_{\rm eff}$ of $24220 \pm 180$ K. The secondary has a mass of $1.657 \pm 0.017$ $\mathrm{M_{\odot}}$, a radius of $1.530 \pm 0.014$ $\mathrm{R}_{\odot}$, and a $T_{\rm eff}$ of $9080 \pm 390$ K. We also extract the abundances of C, N, O, Mg, and Si for the $\beta$ Cep star, which are found to be consistent with galactic OB binaries. We identified 21 distinct pulsation frequencies, with the dominant mode at 10.24324 d$^{-1}$, which corresponds to a near-harmonic of the system's orbital frequency. The two stars in the EB have asynchronous rotation, with both stars rotating faster than the orbital frequency. We detect a companion to the EB using eclipse timing variations and period changes of the dominant pulsation frequency. We calculate the minimum mass of this tertiary companion to be $4.11 \pm 0.32$ $\mathrm{M_{\odot}}$ which is on an orbit of 2303$\pm$69 d around the EB. Using spectral energy distributions and MIST isochrones, we conclude that V446 Cep is either a co-evolving hierarchical 2+2 quadruple or a triple system where the third body is a compact object.
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All authors A. Moharana, J. Southworth, K. Pavlovski, A. Miszuda, R. S. Rathour, K. G. Hełminiak, F. Marcadon, D. M. Bowman, T. B. Pawar, A. Tkachenko

Astrophysics of Galaxies

Symmetric kiloparsec-scale radio knots in NGC 7213: evidence for a confined weak jet and recurrent nuclear activity

G. Bruni, F. Panessa, E. Kammoun et al. (+9 more)

Low-luminosity active galactic nuclei (LLAGNs) often host weak radio jets whose propagation is shaped by the surrounding interstellar medium. We investigate the nearby LLAGN NGC7213 to assess its ability to launch collimated outflows beyond the nucleus and to characterise the origin and variability of newly identified radio components from parsec to kiloparsec scales. We present new MeerKAT, uGMRT, ATCA, and Australian Long Baseline Array (LBA) observations from 300 MHz to 9 GHz. We analyse the morphology and spectra of the kiloparsec-scale emission and use LBA monitoring to probe the parsec-scale core. We discover a pair of compact radio knots located symmetrically at a projected distance of ~5 kpc north and south of the nucleus. The knots have nearly identical flux densities and flat radio spectra from 300 MHz to at least 5.5 GHz, with no significant spectral or geometric asymmetry. The LBA monitoring shows that the nuclear source remains unresolved at all epochs, constraining the 8 GHz emission to sub-parsec scales, and reveals significant variability on decade-long and month-long timescales, including a flux-density increase of ~40 mJy over six months. The symmetry, spectra, and physical properties of the kiloparsec-scale knots support their interpretation as compact termination shocks of a weak or intermittent jet launched by NGC7213 and confined by the dense, disturbed interstellar medium. The unresolved, variable parsec-scale core indicates that the high-frequency radio variability originates in the innermost jet region, likely linked to a recent increase in nuclear activity. NGC7213 is therefore a nearby example of how weak jets in low-accretion AGN can produce both compact nuclear variability and symmetric kiloparsec-scale structures in complex environments.
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All authors G. Bruni, F. Panessa, E. Kammoun, A. L. Thakur, C. Reynolds, R. Ricci, M. Wieringa, S. Bianchi, A. De Rosa, G. Matt, F. Nicastro, F. Ursini

Earth and Planetary Astrophysics

Exploring the Impact of Tilted Magnetic Dipoles on the Atmospheric Dynamics of Hot Jupiters: Towards an Improved Magnetohydrodynamic Framework

James Fecanin, Hayley Beltz, John Allen et al. (+1 more)

The atmospheres of hot Jupiters lie in a dynamical regime without a solar system analogue. The strongly irradiated daysides reach temperatures sufficiently hot for substantial thermal ionization of atmospheric species, resulting in flows that can interact with the planetary magnetic field. These magnetic effects can significantly impact wind speeds, atmospheric temperatures, and large-scale circulation patterns. Previous work combining 3D atmospheric models and magnetic prescriptions has shown the impact of magnetic effects on temperature and velocity profiles are dependent on local atmospheric properties as well as the set of assumptions employed by the magnetic prescription. In this work, we examine a commonly employed magnetic model–a perfectly aligned dipole–in 3D General Circulation Models (GCMs) and extend this framework to allow for tilting of the deep-seated internal magnetic dipole field relative to the axis of rotation. We find that the inclusion of a tilted dipole introduces pronounced north-south asymmetries into the temperature profile leading to latitudinally shifted hotpots and deflection of winds that would otherwise be axially symmetric. We additionally simulate JWST/NIRSpec phase curves. We find that the strength of the magnetic field has the most significant effect on the simulated phase curves, with stronger magnetic fields increasing the amplitude of the phase curve and reducing the hot spot offset. Our model can provide qualitative insight into how the magnetic dipole strength or orientation may influence the large scale atmospheric dynamics and represents one of the most sophisticated incorporations of magnetic effects in GCMs for hot Jupiter atmospheres to date.
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All authors James Fecanin, Hayley Beltz, John Allen, Thaddeus Komacek

Solar and Stellar Astrophysics

The Unstable Chromosphere: Effects of the Thermal Farley-Buneman Instability Across a Broad Range of Solar Chromospheric Conditions

Samuel Evans, Meers Oppenheim, Juan Martínez-Sykora et al. (+1 more)

In the coldest regions of the solar atmosphere, lingering discrepancies between models and observations may be caused by the Thermal Farley-Buneman Instability (TFBI). This meter-scale, electrostatic, collisional, multifluid plasma instability converts energy from neutral flows into turbulent motions and heating. In the neutral frame of reference, these neutral flows manifest as an electric field which can drive the TFBI. In this work, we simulate the TFBI across a broad range of solar chromospheric conditions. We find clear proportionality between between TFBI-driven relative temperature increases of charged species ($\Delta T_{s}^{\text{(turb)}} / T_{s}^{(0)}$) and driving electric field strength relative to the theoretical threshold field required for TFBI growth. We also discover a correlation between relative driving field strength and turbulent motions. Additionally, the TFBI consistently causes average current density to rotate towards the driving field, with Pederson/ambipolar component ($\vec{J} \cdot \hat{E}^{(0)}$) increasing by up to roughly 60% while the Hall component ($\vec{J} \cdot \hat{E}^{(0)} \times \hat{B}$) decreases in magnitude by up to roughly 80%. Meanwhile, we find TFBI-driven turbulence increases neutral heating rates by $(43\pm7)\%$ on average, with 85% (28/33) of simulations having mean increase more than 29%, and a flat line of best fit suggesting zero correlation with driving field.
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All authors Samuel Evans, Meers Oppenheim, Juan Martínez-Sykora, Alexander Green

Earth and Planetary Astrophysics · Cross-listed from physics.space-ph

Solar Energetic Particle Reflection by Precursor ICMEs: Multi-spacecraft Observations of Bi-Directional Electron Beams at 1 AU

Lucas Liuzzo, Wenwen Wei, Andrew R. Poppe et al. (+2 more)

We present case studies of two impulsive solar energetic electron (SEE) events during which particles at energies from 1-600 keV were detected by THEMIS-ARTEMIS orbiting the Moon, Wind at Earth's first Lagrange point, and (for one event) STEREO-A located at 1 AU, off the Sun-Earth line. The SEEs were initially highly anisotropic, traveling outward along the magnetic field with distinct energy-time dispersion. For one event, the spectra contained inverse velocity dispersion (IVD) signatures, whereby electrons at intermediate energies arrived to the spacecraft before those at higher energies. Similar features were recently discovered within 1 AU for energetic protons; this represents the first IVD detection for energetic electrons at Earth's orbital distance. During both events, a second beam of counter-streaming electrons was detected after a short time. Based on the time-delay in the detections at various energies, the path traveled by these counter-streaming electrons was on the order of 1-2 AU. We show that an interplanetary coronal mass ejection (ICME) passed the spacecraft a few days prior to the onset of each event and was located beyond 1 AU when the SEEs were detected, suggesting that the electrons were part of the same population, but reflected off the shock front of these precursor ICMEs. In the context of solar system exploration, this represents an unidentified hazard for astronaut safety beyond low-Earth orbit: although the initial phase of impulsive SEE events typically stream anti-Sunward, ICMEs located beyond Earth provide a mechanism for hazardous particles to travel Sunward during extreme events.
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All authors Lucas Liuzzo, Wenwen Wei, Andrew R. Poppe, Christina O. Lee, Vassilis Angelopoulos

Solar and Stellar Astrophysics

The Singular Behaviour of Ambipolar Diffusion Revealed by 1D Cartesian Solutions

F. Moreno-Insertis, E. R. Priest and D. Nóbrega-Siverio

Aims. We seek to (a) study 1D Cartesian ambipolar diffusion near null points; (b) characterise the nonlinear eigenmodes for ambipolar diffusion; (c) propose tests for ambipolar diffusion solvers in MHD codes. Methods. (a) Direct analysis is used to find analytical solutions for ambipolar diffusion. (b) To study the eigenmodes, we solve the ODE for self-similar solutions of the 1D ambipolar diffusion equation using phase-plane techniques. We also solve the general time-dependent 1D problem for initial conditions of interest. (c) We test the Bifrost code by trying to reproduce the behaviour of the eigenmodes. Results. (a) A stagnation-point flow solution was found with a uniform flux transfer rate across three regions: an external advection region; an internal ambipolar diffusion region with magnetic profile B propto x**(1/3); and an innermost Ohmic region with B propto x; in the latter, flux annihilation occurs at a rate imposed by the advection. (b) Both symmetric and antisymmetric eigenmode solutions to the ambipolar diffusion problem are found with sharp current sheets at the internal nulls. The time evolution of the eigenmodes (pure or perturbed) is probed, showing how higher-order eigenmodes, or perturbed ones, evolve in time towards the lowest-order allowable eigenmodes. (c) The Bifrost code reproduces the behaviour of the eigenmodes with excellent accuracy. Conclusions. Stagnation-point configurations exist with ambipolar diffusion carrying magnetic flux in an inner layer and serving as an intermediary between the external advection and an Ohmic-diffusion core around the null. Our tests are compatible with the hypothesis that zero-flux higher harmonics of the self-similar equation evolve toward either the first symmetric or antisymmetric harmonic. The self-similar solutions can serve as strong tests for ambipolar diffusion solvers in general MHD codes.
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Earth and Planetary Astrophysics

Hourly radio variability of PDS70c from time-differential photometry

Simon Casassus, Miguel Carcamo, Oriana Dominguez-Jamett et al. (+5 more)

The radio emission mechanisms from accreting protoplanets, and their variability, link observations and physical properties. We revisit the variability of the ~343GHz (ALMA Band7) flux density from PDS70c (F_B7). The subtraction of the extended time-averaged signal may enable the measurement of the flux density from variable and embedded point sources. Visibility alignment and self-calibration yields close to thermal residuals in each execution block (EB) of ALMA observations, allowing the time-differential photometry of point-source in the visibility domain. The variability of PDS70c is checked against synthetic control point sources. In images of the 2017 ALMA dataset, with three ~1h EBs, PDS70c was detected only on 6 Dec. 2017, where F_B7 rose by 228%+-69% (3.3sigma). Time-differential photometry confirms a rise by 170%+-46% (3.7sigma). An application to ~2h EBs from the 2023 dataset resulted in constant flux densities, within a scatter of ~15%. However, F_B7(t) shows some scatter when splitting the deep 2023 EBs in 20min intervals, with a chi2 test significant at 2.6sigma, and an intrinsic dispersion of 49%21%. The radio variability of PDS70c, observed over hours but averaged out on longer timescales, is indeed expected if the signal is due to HI free-free from an accretion shock on a circum-planetary disk surface. A planet-to-environment mass ratio <1E-4 is required to avoid smoothing by radiative diffusion if the signal is due to thermal emission from the environment.
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All authors Simon Casassus, Miguel Carcamo, Oriana Dominguez-Jamett, Yuhiko Aoyama, Gabriel-Dominique Marleau, Ondrej Chrenko, Hauyu Baobab Liu, Barbar Ercolano

Earth and Planetary Astrophysics

RSCL Earth Lookback Simulator: A Real-Time Multi-Physics Framework for Relativistic Signal Propagation from Confirmed Milky Way Exoplanets

Mohamed El-Hadedy

Electromagnetic signals propagating across interstellar distances are subject to simultaneous distortion by seven distinct physical mechanisms: relativistic Doppler shift, stellar aberration, interstellar medium dispersion, special relativistic time dilation, general relativistic gravitational time dilation, cosmological redshift, and atmospheric transmission losses. Each effect is individually well established, yet to our knowledge no existing public browser-based framework applies all seven effects simultaneously to a catalog of confirmed exoplanets using real measured stellar and planetary parameters. This paper presents the RSCL Earth Lookback Simulator, an open-source browser-based framework that addresses this gap. Seven physics engines operate in parallel on a curated catalog of 62 confirmed Milky Way exoplanets, drawing all physical parameters from the NASA Exoplanet Archive and the NE2001 galactic electron density model. Computed quantities are checked for consistency against published reference values. The framework is deployed as a public open-source application and is designed to serve researchers in SETI, exoplanet science, astrobiology, and space mission planning.
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Cosmology and Nongalactic Astrophysics

Variance-aware model discrimination with the Sunyaev-Zel'dovich effect of the 21 cm background (SZE-21cm)

Charles Mpho Takalana

The sky-averaged redshifted 21 cm signal from Cosmic Dawn is a uniquely sensitive tracer of early heating and ionisation, but it remains challenging to measure directly. The Sunyaev-Zel'dovich effect of the 21 cm background (SZE-21cm) provides a complementary route: Comptonisation of the incident low-frequency background by hot electrons in galaxy clusters produces a spectral distortion that can be recovered as a difference between the line of sight through a galaxy cluster and a nearby blank-sky reference, and is therefore naturally compatible with interferometric observations. We use semi-numerical simulations of the global 21 cm background, together with a relativistic scattering kernel built from the Maxwell-Juttner electron distribution, to assess how well the SZE-21cm separates physically distinct Cosmic Dawn scenarios. The model suite varies star-formation efficiency, X-ray spectral hardness, heating timing, and the suppression of low-mass sources; SZE-21cm spectra are computed over 45-200 MHz. Separability is quantified through feature-based summaries, standardised residual spectra, and a band-integrated pairwise separability index that combines seed-to-seed scatter with an astrophysical variance layer derived from coeval ON-aperture / OFF-annulus statistics. The resulting indices are intrinsic and instrument-free, and therefore upper bounds on what a real experiment with finite thermal noise can achieve. Heating-timing variations produce the strongest separations, while the X-ray hardness variations explored here are nearly degenerate with the fiducial case once the ON-OFF variance is included. We also propagate an EDGES-like benchmark curve as a morphological stress test of the framework, not as a physically validated model, illustrating how anomalous global-signal morphologies would map into the SZE-21cm.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Peculiar velocities in the $\Lambda$CDM universe

Evanthia Patliaka and Christos G. Tsagas

We present a unified analysis of the linear evolution of peculiar-velocity perturbations in the distribution of pressureless matter after recombination. Our study is carried out within the framework of full general relativity and encompasses both the earlier Einstein-de Sitter epoch and the subsequent $\Lambda$-dominated phase. Starting from a non-interacting, non-comoving mixture of radiation and dust, we derive the generalized differential equations governing the evolution of these velocity perturbations. We confirm that linear peculiar velocities ($v$) grow as $v\propto t$ throughout the Einstein-de Sitter era. In contrast, during a later phase of increasing $\Omega_{\Lambda}$-contribution, we find that the growth of the peculiar-velocity field is progressively suppressed, before reversing to decay. Nevertheless, part of the earlier velocity growth persists to the present. Hence, bulk-flow velocities at intermediate redshifts are expected to exceed those predicted by the $\Lambda$CDM model, followed by a decline in their value at lower redshifts. Interestingly, such peculiar-velocity profiles have already been reported in the literature.
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High Energy Astrophysical Phenomena

Core Collapse Supernova Modeling: The Next Ten Years

Anthony Mezzacappa

Core collapse supernova modeling has advanced considerably since the first numerical simulations were performed sixty years ago. In particular, the last decade has brought us sophisticated three-dimensional models with significant predictive capabilities – e.g., for core collapse supernova gravitational wave emission. The six decades of modeling have shown us the importance of individual components of these general relativistic neutrino radiation magnetohydrodynamics events – specifically, the importance of neutrino kinetics, fluid instabilities, magnetic fields, strong gravity, and the nuclear equation of state and neutrino–matter interactions calculated in a manner consistent with the equation of state. They have also shown us that simulation outcomes are sensitive to variations in the treatment of these ingredients, demanding a level of rigor that has not yet been consistently met by modelers. The efficacy of the neutrino shock reheating mechanism for core collapse supernovae has been demonstrated. The models now require an improved quantitative predictive capability, which will be achieved through increased sophistication in the treatment of model components, both macroscopic (e.g., strong-field gravity) and microscopic (e.g., neutrino–matter interactions). Advancement of core collapse supernova theory will also require the cooperation of modelers in other fields, especially stellar evolution and nuclear theory, to meet the level of rigor required to make the most of the eventuality of a Galactic core collapse supernova and its multimessenger emissions.
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Astrophysics of Galaxies

Galaxy mergers and disk angular momentum evolution: stellar halos as a critical test

Eric F. Bell, Richard D'Souza, Monica Valluri et al. (+1 more)

We investigate the role of hierarchical assembly in the angular momentum (AM) evolution of galaxies using a sample of 471 Milky Way-mass galaxies from the TNG-50 simulation. While galaxy orientation is often attributed to tidal torques and the cooling of gas within halos, we demonstrate that galaxy reorientation (tilting) is a common consequence of satellite accretion. Specifically, 80+/-2% of galaxies show alignment between their present-day AM and the orbital AM of their most massive (dominant) merger progenitor. This reorientation typically results in changes of around 50% in the galaxies' specific AM, with the most significant shifts occurring in galaxies that were initially highly misaligned. We find only a weak influence from the second most massive merger, and negligible impacts from surviving satellites. We show that accreted stellar halos encode the history of this reorientation. Driven by the same accretion event, the main bodies of galaxies and their stellar halos tend to co-align, with 81+/-2% of TNG-50 stellar halos showing prograde rotation relative to the galaxy. This signature will be detectable through major-axis kinematics with 30-meter class telescopes for Milky Way mass galaxies, offering a valuable observational test of this picture. While halo rotation directly constrains the specific AM of mergers within the last ~7 Gyr, this kinematic `memory' is largely erased for older and more radial events. Consequently, the Milky Way itself appears to be a notable exception to the general merger-driven trend: TNG-50 analogs with early, radial, and low angular momentum dominant mergers affect present-day disk orientation minimally. The current MW disk orientation may instead reflect the accumulated influences of gas accretion or dark matter torques.
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All authors Eric F. Bell, Richard D'Souza, Monica Valluri, Katya Gozman

High Energy Astrophysical Phenomena

Moving-Mesh Simulations of Mini-Common Envelope Ejection in Classical Novae

Nicholas Nelson and Philip Chang

Although well studied, our understanding of the mass ejection mechanisms of cataclysmic variables remains incomplete. Recent work suggests that binary interaction plays an important role in driving and shaping this mass ejection and may affect the long-term evolution of the system. In this paper, we perform a three-dimensional moving-mesh hydrodynamic simulation of a cataclysmic variable system to study the effect of binary interaction on mass ejection. We find that once the flow crosses the ${\rm L}_1$ Lagrange point, the material is ejected roughly isotropically. This can be seen in a roughly spherical distribution of the ejecta at large radii. We also show that the ${\rm L}_2$ Lagrange point is not important in the ejection of mass, contrary to the assumption in some previous work in this area. Finally, we find that the specific angular momentum of the ejected material is larger than its initial specific angular momentum. This enhanced angular momentum ejection likely affects the long-term evolution of the binary system.
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High Energy Astrophysical Phenomena

Pair-Rich Corona of an Accreting Kerr Black Hole

Jonathan Zhang and Christopher Thompson

We build a self-consistent model of a warm scattering corona near an accreting black hole in Kerr geometry, in the regime of slow ($\sim 0.01$ Eddington) mass accretion. An iterative Monte Carlo procedure is developed that incorporates self-consistently the effects of Compton scattering and electron-positron pair creation, as well as general relativistic lensing and frame dragging effects. Soft thermal photons are seeded in the inner disk and the velocity dispersion of the electrons and positrons adjusted to yield a fixed seed luminosity amplification through Compton scattering. A simple kinematic prescription is also added for bulk outflow. Pair creation by photon collisions raises significantly the density of scattering charges in and around the innermost ion disk, which is assumed to be geometrically thick and rarefied compared with the disk outside 10 gravitational radii. The self-consistent pair cloud is concentrated closer to the BH. The spectrum and polarization of the escaping X-rays are recorded as a function of the observer's orientation. The temperature and Compton parameter measured from the output spectra using the compPS package are consistent with fits to binary BH data in the hardest spectral state; the polarization degree rises to $4-10\%$ through the 2-8 keV band with allowance for $e^\pm$ upflow from the BH equator.
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High Energy Astrophysical Phenomena

A Physics Informed Bayesian Neural Network for the Neutron Star Equation of State

J.D. Baker, C.A. Bertulani and R.V. Lobato

We present a physics-informed Bayesian neural-network framework for inferring neutron-star equations of state from theoretical priors and propagating the resulting uncertainty to stellar observables. Trained on a representative set of hadronic EoSs, the model learns the equation of state through stochastic variational inference by representing the squared speed of sound with a bounded network output and obtaining the pressure by integration, so that causality, thermodynamic stability, and monotonicity are guaranteed by construction, with low-density nuclear and perturbative-QCD normalization anchors. Core EoSs are matched to an SLy4 crust and propagated through a unified Tolman-Oppenheimer-Volkoff-plus-tidal solver to obtain posterior predictions in the mass-radius ($M$-$R$) and mass-tidal-deformability ($M$-$\Lambda$) planes. The physics-informed prior is then updated with current multi-messenger data: NICER radius measurements, the GW170817 tidal-deformability constraint, and the $2\,M_\odot$ maximum-mass bound; included directly in the variational objective. The observational update moves the canonical radius from $R_{1.4}=13.41\,\mathrm{km}$ in the prior to $R_{1.4}=12.74^{+0.97}_{-0.73}\,\mathrm{km}$ (nominal 90% variational CI), with $\Lambda_{1.4}=428^{+249}_{-130}$ and $M_{\mathrm{max}}\gtrsim 2.0\,M_\odot$. This framework provides a non-parametric route from microphysical EoS uncertainty to neutron-star observables.
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Solar and Stellar Astrophysics

Forward modeling solar spectra onto Doppler images of {\lambda} And

Ö. Adebali and A. G. M. Pietrow

By using the Doppler images of {\lambda} And, we aim to investigate whether surface temperature information can be reversed to create its activity parameters, by feeding a toy model with solar spectra, based on the surface images. At the same time, we examine whether spot contributions alone are sufficient to explain the observed activity modulation of the RS CVn star {\lambda} And while quantifying the differences with the actual observations of this star that are obtained simultaneously with the Doppler images we use. Due to a lack of publicly available starspot models for its stellar type, we adopt observed solar spectra as the only available approximation of {\lambda} And's spots. These spectra are injected into sequence of full disk temperature map derived from Doppler imaging that represent a full stellar rotation. Using this approach, we show that even with simplified assumptions the spectral behavior of {\lambda} And can be qualitatively reproduced. Toy models such as the one presented in this work procure an additional dimension, providing a relation between the surface structures and chromospheric emissions. It also helps to develop a further understanding for the heating mechanisms of these active giants through comparative techniques, where in this case the spot activity seemingly modulates the chromospheric signal and can explain the bulk of its variations over a rotation.
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