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Physics Astrophysics

astro-ph Watch Astrophysics

Wednesday 21 January

Solar and Stellar Astrophysics

Magneto-Archeology of White Dwarfs. Revisiting the fossil field scenario with observational constraints during the red giant branch

Lukas Einramhof, Lisa Bugnet, Leila Magdalena Calcaferro et al. (+2 more)

The detection of strong, large-scale magnetic fields at the surface of only the oldest population of white dwarfs might point towards a hidden internal magnetic field slowly rising to the surface. In addition, strong magnetic fields have recently been measured through asteroseismology in the radiative interiors of red giant stars, the progenitors of white dwarfs. To investigate the potential connection between these observations, we revisit the fossil field framework by using the asteroseismic detections to constrain the strength of such magnetic fields as they evolve to the white dwarf stage. We assume that the magnetic field was either created during the main sequence core convection or that it fills the radiative interior as the star evolves on the red giant branch. From these, we evolve the magnetic flux, allowing for magnetic diffusion along the evolution of a 1.5Msun modelled star. We find that measured field strengths in red giants attributed to the hydrogen-burning shell are compatible with the field amplitudes and emergence timescales of magnetized white dwarfs. On the contrary, magnetic fields generated solely from a convective-core dynamo on the main-sequence and detectable during the red giant branch would be buried too deep in the star and not match the breakout timescales and the field strengths of magnetic white dwarfs. A broadly magnetized internal radiative zone during the red giant branch is therefore key for the fossil field theory to connect magnetic fields observed along the late evolution of stars.
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All authors Lukas Einramhof, Lisa Bugnet, Leila Magdalena Calcaferro, Lucas Barrault, Srijan Bharati Das

High Energy Astrophysical Phenomena

Revealing massive black hole astrophysics: The potential of hierarchical inference with extreme mass-ratio inspiral observations

Shashwat Singh, Christian E. A. Chapman-Bird, Christopher P. L. Berry et al. (+1 more)

Gravitational waves from extreme mass-ratio inspirals (EMRIs) will enable sub-percent measurements of massive black hole parameters and provide access to the demographics of compact objects in galactic nuclei. During the LISA mission, multiple EMRIs are expected to be detected, allowing statistical studies of massive black hole populations and their formation pathways. We perform hierarchical Bayesian inference on simulated EMRI catalogues to assess how well LISA could constrain the astrophysical population using parametrised population models. We test our inference framework on a variety of populations, including heterogeneous and homogeneous mixtures of parametrised subpopulations, and scenarios in which the assumed model is deliberately misspecified. Our results show that population parameters governing distributions with sharp features can be tightly constrained. Mixed populations can be disentangled with as few as $\sim20$ detections, and even with model misspecification, the inference retains sensitivity to key population features. These results demonstrate the capabilities and limitations of EMRI population inference, providing guidance for constructing realistic astrophysical population models for LISA analysis.
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All authors Shashwat Singh, Christian E. A. Chapman-Bird, Christopher P. L. Berry, John Veitch

Earth and Planetary Astrophysics

Alkali recondensation into chondrules

Emmanuel Jacquet, Yves Marrocchi and Sébastien Charnoz

While sub-mm melt droplets should rapidly lose alkali elements in a vacuum at liquidus temperatures, chondrules are only modestly depleted in them (by less than one order of magnitude). The detection of sodium in olivine cores has previously suggested very high saturating partial pressures of gaseous sodium, but we show that alkalis were lost during heating and recondensed at lower temperatures, essentially in the present-day chondrule mesostases. This recondensation was accompanied by mass-dependent enrichment in light isotopes (for multi-isotope alkalis such as K and Rb), but its limited extent indicates a cooling acceleration (or "quenching"). The isotopic fractionation also constrains the ratio of the chondrule density and the cooling rate prior to the quench around $10^{-6}\:\mathrm{kg.m^{-3}.K^{-1}.h}$ suggesting densities above $\sim 10^{-6}\:\mathrm{kg/m^3}$. In a nebular context, this is achievable by radial and vertical concentrations near pressure bumps.
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Astrophysics of Galaxies

Implications of the continuous radio-loudness distribution among AGNs in the local Universe

A. Wójtowicz, N. Vale Asari, Ł. Stawarz et al. (+2 more)

Aims. We investigate the radio loudness ($\mathcal{R}$) distribution in a large, homogeneous sample of radio galaxies. Methods. The sample is composed of galaxies from the ROGUE I/II catalogue belonging to the SDSS MGS and is divided into optically inactive radio galaxies (OPIRGs), optically active ones (OPARGs) and radio Seyferts. We use optical, mid-infrared and radio data to calculate the AGN bolometric luminosities, accretion rate ($\lambda$), black-hole mass ($M_{BH}$) and $\mathcal{R}$. Results. Contrary to some previous studies based on restricted samples, using our complete sample of objects with redshifts $z < 0.4$, we find no evidence of bimodality in $\mathcal{R}$. The highest $\mathcal{R}$ values are associated with extended radio structures. $\mathcal{R}$ is anti-correlated with $\lambda$, and spans about 2 dex at fixed $\lambda$. Radio Seyferts, OPARGs and OPIRGs form a sequence of increasing $M_{BH}$ with substantial overlap. Radio Seyferts show no $\mathcal{R}$-$M_{BH}$ correlation, whereas OPARGs and OPIRGs show a weak positive trend. From theoretical considerations, the observed two-dex spread in radio luminosity and $\mathcal{R}$ can be reproduced by a four-fold variation in the dimensionless magnetic flux $\varphi$ assuming realistic black-hole spins. Conclusions. The smooth distribution of radio loudness supports a common evolutionary path for all radio sources, with black-hole spin and magnetic field varying continuously. The radio loudness depends on black-hole mass and accretion rate, while moderate variations in $\varphi$ may account for the observed scatter in this relation.
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All authors A. Wójtowicz, N. Vale Asari, Ł. Stawarz, G. Stasinska, D. Kozieł-Wierzbowska

High Energy Astrophysical Phenomena

The early r-process nucleosynthesis scenarios

Noam Soker

I compare seven actively studied r-process nucleosynthesis scenarios against observed properties of r-process elements in the early Universe, and conclude that the most likely scenario to contribute to the site of elements below the third r-process peak is the magnetorotational r-process scenario, and that of the third peak is the common envelope jets supernova (CEJSN) r-process scenario. The collapsar and CEJSN r-process scenario might also contribute to the lighter r-process elements, and the binary neutron star (NS-NS) merger r-process scenario might contribute to the third r-process peak. The magnetar, the wind from the newly born NS, and the accretion-induced collapse of a white dwarf r-process scenarios fall short in explaining observations. They might exist, but cannot be major contributors to the r-process in the early Universe. To constrain r-process scenarios in the early Universe, I require that they explain the large scatter in the r-process abundances of very metal-poor stars, account for the correlation between light r-process nucleosynthesis and iron production, and the lack of correlation between the third peak r-process production and iron production, as inferred from very metal-poor stars. I discuss the diversity of the CEJSN r-process scenario and encourage extending its exploration.
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Astrophysics of Galaxies

Probing Heavily Obscured AGN in Major Galaxy Mergers Using the mm-X-ray Correlation

M. Droguett-Callejas, E. Treister, L. Barcos-Muñoz et al. (+10 more)

The study of heavily obscured supermassive black hole (SMBH) growth in late-stage galaxy mergers is challenging: column densities $N_{\mathrm{H}}>10^{24},\mathrm{cm}^{-2}$ can block most nuclear emission, leaving significant gaps in the SMBH growth census. Millimeter-wave continuum emission offers a potential window into this obscured phase, as it can trace Active Galactic Nuclei (AGN) activity through mechanisms less affected by dust extinction. In this work, we test whether the observed correlation between millimeter ($\sim200,\mathrm{GHz}$) and hard X-ray (14 - 150,keV) luminosities can be used to plausibly identify hidden AGN in local (Ultra)Luminous Infrared Galaxies (U)LIRGs, including systems hosting confirmed dual AGN. We identify three sources – one confirmed AGN and two strong candidates – presenting significant evidence of AGN activity. The confirmed dual AGN lie within $\sim3\sigma$ of the mm–X-ray correlation, suggesting this relation can be used to identify hidden pairs. By combining the position of each source relative to this correlation with independent star formation rate constraints, we propose a method to disentangle AGN and star formation contributions for sources with measured column densities. While our analysis is based on a small, heterogeneous local sample and relies on empirical scaling relations, these results indicate that millimeter continuum emission may provide a useful complementary diagnostic for obscured SMBH growth. ALMA observations at high angular resolutions are particularly valuable for this approach, while future facilities such as the ngVLA will be essential to test its robustness in larger and more distant samples.
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All authors M. Droguett-Callejas, E. Treister, L. Barcos-Muñoz, M. Johnstone, F. E. Bauer, T. Kawamuro, N. Torres-Albà, C. Ricci, M. Koss, Y. Song, A. Peca, A. Evans, J. González

Earth and Planetary Astrophysics

A nomenclature for individual exocomets

Alain Lecavelier des Etangs, Paul A. Strøm and Darryl Z. Seligman

With recent observational advancements, exocomet studies have entered a new era: we have moved from an epoch where exocomets' signatures were analysed to identify their true nature to a new epoch where individual exocomets' detections are studied in detail to characterise the observed bodies. In this context, as with other astronomical objects such as exoplanets and minor bodies in the solar system, a nomenclature system is needed to uniquely identify any observed exocometary body. Here, after outlining the purpose of a nomenclature and its required characteristics, we review the information on exocomets that can be included in the nomenclature. Finally, we propose an exocomet nomenclature scheme to identify the individual exocomets that have been discovered or yet to be discovered. Examples of nomenclature names of a few archetypal exocomets are provided.
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2601.15176 · 21 Jan · 10 pages, 1 figure. Published in Space Science Reviews on January 20, 2026. Chapter written for the the workshop 'Exocomets: Bridging our Understanding of Minor Bodies in Solar and Exoplanetary Systems' (July 2024), at the International Space Science Insitute (ISSI), Bern. Available https://link.springer.com/article/10.1007/s11214-025-01261-8

Abstract PDF $EXOP ×1$SOLAR ×1

Cosmology and Nongalactic Astrophysics

Dark Energy Survey Year 6 Results: Galaxy-galaxy lensing

G. Giannini, G. Camacho-Ciurana, A. Whyley et al. (+116 more)

We present galaxy–galaxy lensing (GGL) measurements from the full six years of data from the Dark Energy Survey (DES Y6), covering $4031\,\mathrm{deg}^2$ and used in the DES Y6 $3\times2$pt cosmological analysis. We use the MagLim++ lens sample, containing $\sim 9$ million galaxies divided into six redshift bins, and the Metadetection source catalog, including $\sim 140$ million galaxies divided into four redshift bins. The mean tangential shear signal achieves a total signal-to-noise ratio (S/N) of $173$, corresponding to a $17\%$ improvement over DES Y3. After applying the scale cuts used in the cosmological analysis, with $R_{\min}=6\,\mathrm{Mpc}/h$ ($4\,\mathrm{Mpc}/h$) for the linear (nonlinear) galaxy-bias model, the S/N is reduced to $75$ (90). A comprehensive suite of validation tests demonstrates that the measurement is robust against observational and astrophysical systematics at the statistical precision required for the DES Y6 analysis. Although not used in the main cosmological analysis, we extract high–signal-to-noise geometric shear-ratio measurements from the galaxy–galaxy lensing signal on small angular scales. These measurements provide an internal consistency check on the photometric redshift distributions and shear calibration used in the $3\times2$pt analysis.
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All authors G. Giannini, G. Camacho-Ciurana, A. Whyley, J. Prat, J. Blazek, C. Sánchez, G. Zacharegkas, A. Alarcon, E. Legnani, A. Amon, D. Anbajagane, S. Avila, K. Bechtol, M. R. Becker, G. M. Bernstein, S. Bocquet, A. Campos, A. Carnero Rosell, R. Cawthon, C. Chang, M. Crocce, W. d'Assignies, J. De Vicente, A. Drlica-Wagner, S. Elvin-Poole, A. Ferté, M. Gatti, D. Gruen, M. Jarvis, M. Manera, S. Mau, J. McCullough, F. Menanteau, J. Myles, A. Porredon, M. Rodriguez-Monroy, A. Roodman, E. S. Rykoff, S. Samuroff, D. Sanchez Cid, I. Sevilla-Noarbe, T. Schutt, M. A. Troxel, N. Weaverdyck, M. Yamamoto, B. Yin, T. M. C. Abbott, M. Aguena, S. Allam, O. Alves, F. Andrade-Oliveira, D. Bacon, E. Bertin, D. Brooks, H. Camacho, J. Carretero, L. N. da Costa, M. E. da Silva Pereira, T. M. Davis, D. L. DePoy, S. Desai, H. T. Diehl, P. Doel, C. Doux, T. F. Eifler, S. Everett, A. E. Evrard, P. Fosalba, J. Frieman, J. García-Bellido, E. Gaztanaga, P. Giles, K. Glazebrook, I. Harrison, W. G. Hartley, K. Herner, S. R. Hinton, D. L. Hollowood, K. Honscheid, D. Huterer, B. Jain, D. J. James, N. Jeffrey, T. Kacprzak, S. Kent, E. Krause, O. Lahav, S. Lee, J. L. Marshall, J. Mena-Fernández, R. Miquel, J. J. Mohr, J. Muir, R. C. Nichol, R. L. C. Ogando, A. Palmese, M. Paterno, W. J. Percival, D. Petravick, A. A. Plazas Malagón, M. Raveri, R. Rosenfeld, E. Sanchez, E. Sheldon, T. Shin, J. Allyn. Smith, M. Smith, M. Soares-Santos, E. Suchyta, M. E. C. Swanson, G. Tarle, D. Thomas, C. To, D. L. Tucker, V. Vikram, M. Vincenzi, A. R. Walker, P. Wiseman, B. Yanny

Earth and Planetary Astrophysics

A theory of transmission spectroscopy of hydrodynamic outflows from planetary atmospheres: Spectral-line saturation and limits on mass-loss constraints

Leonardos Gkouvelis

Transmission spectroscopy is a key technique in the characterization of exoplanet atmospheres and has been widely applied to planets undergoing hydrodynamic escape. While a robust analytic theory exists for transmission spectra of hydrostatic atmospheres, the corresponding interpretation for escaping atmospheres has so far relied on numerical modeling, despite the growing number of observations of planetary winds. In this work, a theory of transmission spectroscopy in hydrodynamically escaping atmospheres is developed by coupling the standard transmission geometry to a steady-state, spherically symmetric, isothermal outflow. This approach yields closed-form expressions for the chord optical depth and effective transit radius of a planetary wind and allows the optical depth inversion problem to be examined. The analytic solution reveals that transmission spectroscopy of planetary winds naturally separates into two regimes. In an opacity-limited regime, transmission depths retain sensitivity to the atmospheric mass-loss rate $\dot{M}$. Beyond a critical threshold, however, spectral-line cores become saturated and no longer provide a unique constraint on the escape rate. This transition is marked by a sharp analytic boundary of the form $\sigma(\lambda)\,\dot{M} \le C_{\rm sat}$, where $\sigma(\lambda)$ is the line absorption cross-section and $C_{\rm sat}$ is a constant set by the thermodynamic and geometric properties of the wind. This condition specifies when the inversion between transmission depth and mass-loss rate admits a real solution. Once it is violated, the effective transit radius is no longer controlled by opacity or mass loss, but by the geometric extent of the absorbing wind.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Chemical evolution of antimatter domains in early Universe

A.I.Dembitskaia, Stephane Weiss, M. Yu. Khlopov et al. (+1 more)

According to modern physics, our Universe is baryon-asymmetric. That phenomenon can not be described in the frameworks of the Standard Model of particle physics. Globally, the Universe consists of baryon matter. However, some scenarios can lead to the existence of local antimatter domains. In the research, the chemical evolution of such an isolated antimatter domain, surrounded by baryonic matter, is studied. The size of the domain is estimated according to the conditions of its survival in baryon surrounding, and the process of annihilation at its border is taken into account.
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All authors A.I.Dembitskaia, Stephane Weiss, M. Yu. Khlopov, M.A.Krasnov

High Energy Astrophysical Phenomena

Properties and Possible Physical Origins of $\gamma$-ray Emission in Extreme Synchrotron Blazars

Ji-Shun Lian, Jia-Xuan Li, Ze-Rui Wang et al. (+3 more)

Extreme synchrotron blazars, characterized by a first peak in their broadband spectral energy distributions (SEDs) at frequencies exceeding $10^{17}$ Hz, often exhibit a second peak beyond 1~TeV. These sources serve as ideal laboratories for studying particle acceleration and radiation mechanisms in relativistic jets. In this work, we systematically analyze the $\sim$16-year Fermi-LAT observational data for 25 extreme high-synchrotron-peaked BL Lacs (EHBLs). The results indicate that the majority of these sources display stable or low flux levels in the GeV band, with only 6 sources showing significant variability at a confidence level exceeding 5$\sigma$. The time-averaged spectra over the 16-year period for most EHBLs are well described by a hard power-law model, with photon indices predominantly clustered between 1.7 and 1.8. Using Fermi-LAT data in conjunction with multiwavelength observations compiled from the literature, we construct broadband SEDs for these EHBLs and fit them with a one-zone synchrotron + synchrotron-self-Compton (SSC) model. We find that this simplified theoretical framework is sufficient for modeling the observed SEDs of most of these EHBLs, albeit requiring relatively higher electron energies compared to other $\gamma$-ray emitting HBLs, and at times under-representing the UV emission. Based on the SED fitting results, we investigate the physical properties of the emission regions in these EHBLs and compare them with those of other $\gamma$-ray emitting HBLs. Consistent with other GeV–TeV $\gamma$-ray-emitting BL Lacs, the jets in these EHBLs are marked by low radiation efficiency and low magnetization.
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All authors Ji-Shun Lian, Jia-Xuan Li, Ze-Rui Wang, Rui-Qi Huang, Hai-Ming Zhang, Jin Zhang

Cosmology and Nongalactic Astrophysics · Cross-listed from stat.ME

Efficient prior sensitivity analysis for Bayesian model comparison

Zixiao Hu and Jason D. McEwen

Bayesian model comparison implements Occam's razor through its sensitivity to the prior. However, prior-dependence makes it important to assess the influence of plausible alternative priors. Such prior sensitivity analyses for the Bayesian evidence are expensive, either requiring repeated, costly model re-fits or specialised sampling schemes. By exploiting the learned harmonic mean estimator (LHME) for evidence calculation we decouple sampling and evidence calculation, allowing resampled posterior draws to be used directly to calculate the evidence without further likelihood evaluations. This provides an alternative approach to prior sensitivity analysis for Bayesian model comparison that dramatically alleviates the computational cost and is agnostic to the method used to generate posterior samples. We validate our method on toy problems and a cosmological case study, reproducing estimates obtained by full Markov chain Monte Carlo (MCMC) sampling and nested sampling re-fits. For the cosmological example considered our approach achieves up to $6000\times$ lower computational cost.
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Instrumentation and Methods for Astrophysics

Comment on "Application of the three-dimensional telegraph equation to cosmic-ray transport" (arXiv:1606.08272)

Andrei Galiautdinov

In a recent publication [R. C. Tautz and I. Lerche, Res. Astron. Astrophys. 16, 162 (2016); arXiv:1606.08272], the authors present a derivation of the Green's function for the three-dimensional telegraph equation (also known as the heat wave equation, or relativistic heat conduction equation). We demonstrate that the closed-form expression derived in their Appendix A is incorrect. Specifically, the published solution lacks a Dirac delta term representing the ballistic wavefront and contains an algebraic error in the prefactor of the wake term. These omissions arise from the neglect of distributional derivatives when differentiating a Heaviside step function. We provide a rigorous derivation of the Green's function using the Fourier transform method, verify the correct limiting behavior as the damping vanishes, and pinpoint the exact mathematical step where the original derivation failed.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Combined constraints on dark photons from high-energy collisions, cosmology, and astrophysics

A. W. Romero Jorge, L. Sagunski, Guan-Wen Yuan et al. (+2 more)

We investigate a dark sector coupled to the Standard Model (SM) through a kinetically mixed dark photon $U$ associated with a new $U(1)'$ gauge symmetry. Kinetic mixing $\varepsilon$ induces an effective coupling to the electromagnetic current, while $U$ interacts with stable dark matter (DM) $\chi$ via a dark gauge coupling $g_\chi$. Our analysis is based on the parton-hadron-string dynamics (PHSD) transport approach, extended to include dark photon production and decay into dileptons ($U\!\to e^+e^-$). In PHSD, dark photons are produced in high-energy collisions through Dalitz decays of light mesons ($\pi^0,\eta,\eta',\omega$), Delta-resonances ($\Delta\!\to N U$), direct vector meson decays ($\rho,\omega,\phi\!\to U$), kaon decays, and $q\bar q\!\to U$ annihilation. Building on previous PHSD benchmarks against dilepton data, we extract upper limits on $\varepsilon^2(m_U,m_\chi,\alpha_\chi)$ in both the visible regime ($m_U<2m_\chi$), where $U\!\to e^+e^-$ dominates, and the invisible regime ($m_U>2m_\chi$), where $U\!\to\chi\bar\chi$ is kinematically open. Cosmological and astrophysical constraints are incorporated in two complementary ways. First, we compute the velocity-dependent self-interaction cross section $\sigma/m_\chi$ for Yukawa-mediated SIDM and confront it with bounds from dwarf galaxies, galaxy groups, and clusters. Second, we determine thermal relic target curves by computing the relic abundance and requiring $\Omega_{\rm DM}h^2\simeq 0.12$, consistent with Planck measurements of the cosmic microwave background. Combining PHSD limits on $\varepsilon^2$ with relic density and self-interaction requirements, we exclude regions of the $(m_\chi,m_U)$ plane for each DM realization (Dirac, Majorana, or complex scalar) and identify benchmark scenarios in which heavy-ion, cosmological, and astrophysical constraints are simultaneously satisfied.
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All authors A. W. Romero Jorge, L. Sagunski, Guan-Wen Yuan, T. Song, E. Bratkovskaya

Astrophysics of Galaxies

CO Diffusion on Interstellar Amorphous Solid Water: A Computational Study

Francesco Benedetti, Mauro Satta, Tommaso Grassi et al. (+2 more)

Surface chemistry on interstellar dust grains is recognized as a central component in astrochemical models, representing a plausible formation route for many of the observed complex molecular species. However, key parameters governing interstellar surface chemistry, such as diffusion energy barriers, remain poorly constrained. In particular, surface diffusion constitutes a fundamental step for the synthesis of complex organic molecules and plays a crucial role in understanding the desorption process. In this paper, the diffusion dynamics of carbon monoxide (CO) on amorphous solid water (ASW) surfaces, representative of interstellar ices, is modeled with quantum-chemical methods. Employing a representative ensemble of water clusters, each made by 22 molecules, diffusion energy barriers between the binding sites are computed using Density Functional Theory. Diffusion rate coefficients are then determined by applying the harmonic approximation of Transition State Theory. The results, in agreement with experimental studies, revealed a wide distribution of diffusion energies. This reflects the intrinsic topological heterogeneity of ASW surfaces, and highlights how surface mobility significantly influences CO's desorption dynamics and, as a consequence, surface-mediated reactivity in interstellar environments. We show that key parameters commonly employed in astrochemical models, like the ratio between binding and diffusion energy, should be carefully revised.
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All authors Francesco Benedetti, Mauro Satta, Tommaso Grassi, Stefan Vogt-Geisse, Stefano Bovino

High Energy Astrophysical Phenomena

Three-dimensional GRMHD simulations of jet formation and propagation in self-gravitating collapsing stars

Piotr Płonka and Agnieszka Janiuk

We investigate collapsar models with and without self-gravity under identical initial conditions to directly compare the effects of self-gravity on jet properties, such as opening angle, jet power, terminal Lorentz factor, and its variability. We compute a suite of time-dependent, three-dimensional GRMHD simulations of collapsars in evolving spacetime. We update the Kerr metric components due to the growth of the black hole mass and changes its angular momentum. The self-gravity is considered via perturbative terms. We present for the first time the process of jet formation in self-gravitating collapsars. We find that self-gravity leads to temporary jet quenching, which can explain some features in the gamma-ray burst prompt emission. We find no substantial difference in jet launching times between models with and without self-gravity. We observe that in the absence of self-gravity, the jet can extract more rotational energy from the black hole, while self-gravitating models produce narrower jet opening angles. We show that under certain conditions, self-gravity can interrupt the jet formation process, resulting in a failed burst. Our computations show that self-gravity significantly modifies the process of jet propagation, resulting in notably different jet properties. We show that the timescales, variability, and opening angle of jet depend on whether self-gravity is included or not. We argue that self-gravity can potentially explain certain prompt emission properties due to the jet quenching.
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Earth and Planetary Astrophysics

A study of the high-inclination population in the Kuiper belt – V. Mean motion resonances beyond 50 AU

Jian Li

In this paper, we present the most comprehensive study to date on Neptune's mean-motion resonances (MMRs) in the distant Kuiper belt from 50 to 100 AU. Over 200 resonant Kuiper belt objects (KBOs) have been identified in this region, spanning resonances from the 2nd-order 1:3 MMR to the 22nd-order 7:29 MMR, with inclinations $i<40^\circ$. Building on these diverse distributions, we first analyse the dynamical features of numerous $m$:$n$ MMRs, providing an informative database that includes the possible eccentricity ($e$) range, resonance widths, resonance centres, and permissible $(e,i)$ distributions. We then conduct numerical simulations to explore the long-term stability of these MMRs. Our results show that: (1) resonators can occupy all 1:$n$ to 7:$n$ MMRs, with nearly any $n$ corresponding to the 50-100 AU region, including the farthest-out MMRs of 5:29 (24th-order), 6:35 (29th-order), and 7:40 (33rd-order). This suggests that KBOs could potentially exist in even higher-order MMRs than those currently observed. (2) For each set of $m$:$n$ resonances with the same $m$, resonators consistently exhibit inclinations up to $40^\circ$, while eccentricities remain strictly restricted below 0.7. (3) For the 1:3 and 1:4 MMRs, the leading population is less stable than the trailing population. Most interestingly, we discover a novel phenomenon of number reversal, where the higher-order, weaker 3:8 MMR (at semimajor axis $a\approx57.9$ AU) hosts more resonators, rather than fewer as expected, compared to the lower-order, stronger 3:7 MMR (at $a\approx53.0$ AU). Future observations, whether confirming or challenging this phenomenon, will offer valuable insight into the eccentricity and inclination distributions of primordial KBOs.
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Earth and Planetary Astrophysics

How a Close-in Planet Protects its White Dwarf Host from Pollution

Xin-Yue Zhang, Ji-Wei Xie, Di-Chang Chen et al. (+1 more)

Approximately 25-50% of white dwarfs (WDs) exhibit metal absorption lines in their photospheres, which are attributed to accretion from their remnant planetary systems. Although white dwarfs with detected planetary systems are more likely to show photospheric pollution, one notable exception - WD 1856+534 - hosts a close-in giant planet yet exhibits no detectable photospheric metal pollution. Previous studies have proposed that massive, close-in planets can block inward transport of small particles driven by radiative forces (e.g., Poynting-Robertson drag and the Yarkovsky effect). However, it remains unclear whether the close-in planet can similarly prevent delivery of larger bodies via dynamical interactions. We aim to quantify the protective influence of close-in planets on white-dwarf pollution by asteroids approaching on near-parabolic orbits, and to explore the planetary masses and orbital separations required to provide effective protection. We perform ensembles of short-term N-body integrations, sampling a range of planet masses and orbital separations and initializing asteroids on highly eccentric orbits with periapses near the WD Roche radius, in order to measure scattering, capture, and ejection outcomes and quantify the planet's shielding efficiency. For WD1856+534b-like configurations (a_p = 0.02 au), giant planets with masses greater than 0.5 Jupiter masses are sufficient to clear over 80% of highly eccentric small-body contaminants. The effectiveness of the protective effect diminishes with decreasing planetary mass and increasing semi-major axis. These findings help explain why some white dwarfs that host close-in giant planets do not show the photospheric metal pollution commonly observed in other systems.
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All authors Xin-Yue Zhang, Ji-Wei Xie, Di-Chang Chen, Ji-Lin Zhou

Astrophysics of Galaxies · Cross-listed from gr-qc

The relativistic restricted three-body problem: geometry and motion around tidally perturbed black holes

Takuya Katagiri and Vitor Cardoso

We investigate the geometry of a tidally deformed, rotating black hole and timelike geodesics in its vicinity. Our framework provides a local picture of the structural evolution of a relativistic restricted three-body problem around a deformed black hole in an adiabatically evolving binary, motivated by various astrophysical settings including disk dynamics and extreme mass-ratio inspirals. As the tidal-field strength is increased, initially regular, bound geodesics undergo four stages: (i) weak chaos emerges within the bound motion; (ii) a subset of trajectories plunges into the black hole; (iii) a fraction of the remaining trajectories becomes unbound; and (iv) no bound trajectories persist. We provide semi-analytic estimates for the critical tidal amplitudes associated with each transition. Our estimates, within the idealized test-particle description, indicate that, within the frequency band of ground-based gravitational-wave detectors, the matter flow around black holes may already be depleted, whereas LISA and (B-)DECIGO could probe the earlier stages. Our results suggest that an object orbiting a tidally deformed massive black hole may remain near resonances in a long term, indicating an accumulated, non-negligible impact on the gravitational-wave phase. Another finding is that tidal perturbations can modulate nonlinear couplings among epicyclic oscillations of geodesics, and could therefore, in principle, affect resonant excitation mechanism potentially relevant to quasi-periodic oscillations in X-ray light curves from accreting black holes.
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Astrophysics of Galaxies

MSA-3D: Connecting the Chemical and Kinematic Structures of Galaxies at $z \sim 1$

Mengting Ju, Xin Wang, Tucker Jones et al. (+12 more)

We investigate the connection between ionized gas kinematics and gas-phase metallicity gradients in 21 star-forming galaxies at $0.5 < z < 1.7$ from the MSA-3D survey, using spatially resolved JWST/NIRSpec slit-stepping observations. Galaxy kinematics are characterized by the ratio of rotational velocity to intrinsic velocity dispersion, $v/\sigma$, measured at $1.5\,R_e$, where $R_e$ is the effective radius. We find that dynamically hotter disks exhibit systematically flatter metallicity gradients, with a moderate anti-correlation between metallicity gradient and $v/\sigma$ (Pearson $r=-0.43$, $p=0.05$) and a linear fit yields a slope of $\sim 0.005$ dex per dex in $v/\sigma$, weaker than the dependence on stellar mass. A significantly stronger anti-correlation is observed with $R_e/\sigma$, interpreted as a proxy for the radial mixing timescale ($r=-0.59$, $p=0.005$), indicating that cumulative radial mixing more directly regulates chemical stratification. The metallicity gradients in our sample are uniformly shallow, indicating that efficient turbulent mixing in kinematically settled disks regulates the chemical structure of typical star-forming galaxies at $z\sim1$.
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All authors Mengting Ju, Xin Wang, Tucker Jones, Ivana Barišić, Juan M. Espejo Salcedo, Karl Glazebrook, Danail Obreschkow, Takafumi Tsukui, Qianqiao Zhou, Kevin Bundy, Alaina Henry, Matthew A. Malkan, Themiya Nanayakkara, Namrata Roy, Xunda Sun

Astrophysics of Galaxies

Kinematics of the HII region NGC 7538 from study of the Ha line

D. Russeil, H. Plana, P. Amram et al. (+2 more)

Aims. Massive stars impact their surrounding initiating star-formation along their photo-dissociation region. Once the HII region is formed it is unclear if and how the second generation of stars impacts its aspect and evolution. Methods. We performed high spectral resolution (R ~ 23400) Ha Fabry-Perot observations in five fields covering the Galactic HII region NGC 7538 and lead profiles multi-gaussian fitting to extract the parameters as peak intensity, width and velocity. We then analyse the kinematics of the ionised gas building kinematic diagrams and second order structure functions for every field. Results. The observations reveal a general blue-shifted ionised gas flow larger than 11 km s-1 in NGC 7538, consistent with previous studies. Profiles originating from features that are dark in Ha due to extinction or from outside the region show velocity dispersion larger than the one typically found for the Warm Interstellar Medium. The analysis of kinematic diagrams and second-order structure functions reveals non-thermal motions attributed to turbulence and large-scale velocity gradients. In the direction of the HII region itself the turbulence seems to be shock-dominated, with a characteristic scale length between ~ 0.72 and 1.46 pc. In this context, we propose that the kinematics of the central part of the region could be explained by the superposition of the outflow coming from IRS1 and a wind bow shock formed ahead IRS6.
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All authors D. Russeil, H. Plana, P. Amram, A. Zavagno, F. Michel

Solar and Stellar Astrophysics

Numerical study of multiple solar flare induced modulation of Very Low Frequency (VLF) diurnal profile

Sourav Palit, Subhajit Bhattacharyya, Taraknath Bera et al. (+1 more)

Earth's ionosphere is a perpetual detector of ionizing radiation received from celestial objects, particularly the Sun. Solar ionizing radiation in the form of extreme ultraviolet (EUV) and X-rays during both quiet and active phase of the Sun, and charged particles associated with a solar wind imprint their ionization signatures on the ionosphere. Although due to the bipolar nature of the geomagnetic field, the events, such as the solar coronal mass ejections (CMEs) and associated solar wind enhancement, usually disturb the polar ionosphere only, the UV and X-rays from the solar flares produce sudden ionospheric disturbances (SIDs) in low-mid-latitude part of the earth's ionosphere. Such ionospheric disturbances are studied with the help of the influence they exert on radio waves propagating through earth-ionosphere waveguide. For the lower part of the ionosphere, called the D region, prominent modification in electron-ion density during solar flares can be observed via deviation in earth bound Very Low Frequency (VLF) wave signal from its ambient diurnal profile. In earlier work, successful model of the deviation in VLF amplitude due to different classes of solar flares was formulated. There, calculation of rate of ionization with Monte Carlo simulation and ion-chemistry evaluation of plasma density enhancement followed by a radio propagation simulation was used. Presently, we attempt to numerically reconstruct the modulation in VLF signal from its diurnal pattern produced by multiple solar flares occurring over a single day. Successful reconstruction of the VLF signal modulation for such a complex flaring scenario points to the accuracy of our understanding of the ionization effect due to solar activity on the lower ionosphere, and strengthen our claim to use earth's ionosphere as a high energy space transient event detector.
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All authors Sourav Palit, Subhajit Bhattacharyya, Taraknath Bera, Sandip K. Chakrabarti

High Energy Astrophysical Phenomena

AGN in Gaia Alerts: from flares to Changing Look Quasars

M. Dennefeld, T. Pursimo, C. Carvalho et al. (+11 more)

The Gaia Alerts system is providing alerts on a variety of objects displaying a significant photometric change detected by the Gaia satellite from one passage to the next one over the same region of the sky. Among the over 22000 alerts published until the end of 2022, around 13 percent concern AGN or quasar candidates. We have embarked on a spectroscopic ground-based follow-up of some of those (including some selected by a different method specifically in galactic nuclei), to establish their true nature, and reveal the various phenomena leading to a change in magnitude of those AGN. The present paper deals with radio-quiet objects, while the radio-loud ones will be described in a companion paper. We confirm, on one hand, the AGN/quasar nature of 64 new candidates alerted by Gaia, and, on the other hand, obtained second-epoch spectra of over 200 known AGN also alerted for large photometric variations. The observed phenomena show a large variety: from Flares to Tidal Disruption Events (TDEs) and a large number of Changing Look Quasars (CLQs, 56 secure ones, plus 23 probable ones), not forgetting some rarer events like SNe, microlensing events or Extreme Coronal Line Emitters. This sample shows that variability is an excellent tool to detect new quasars, especially radio-quiet ones that otherwise would be undetected, and that a significant fraction of variable AGN/quasars, around 10 percent, presents the CLQ phenomenon. Some of the new CLQs are followed-up to monitor further changes and measure time scales.
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All authors M. Dennefeld, T. Pursimo, C. Carvalho, E. Biancalani, M.A. Diaz Teodori, O. Durfeldt Pedros, M.A. Fetzner Keniger, A. Kasikov, N. Koivisto, J. Martikainen, K. Matilainen, J. Sinkbak Thomsen, J. Terwel, A. Viitanen

High Energy Astrophysical Phenomena

Modelling the Time-variable Broadband Emission and Correlation Study of FSRQ S5 1044+71

Sajad Ahanger, Shah Zahir, Sunder Sahayanathan et al. (+3 more)

We present a detailed temporal and spectral analysis of the blazar S5\,1044+71 using multi-wavelength data obtained from the Fermi-LAT and Swift-XRT/UVOT telescopes. Applying the Bayesian block algorithm to the 3-day binned $\gamma$-ray lightcurve, we identify pronounced variability, including four major outbursts marked by significant flux enhancements. The highest flux recorded was $(1.1 \pm 0.2)\times 10^{-6}\,\text{ph}\,\text{cm}^{-2}\,\text{s}^{-1}$ on 57868.5 MJD. Each outburst comprises multiple components, and lightcurve profile analysis indicates predominantly symmetric temporal structures. The shortest variability timescale of 4.5 hours constrains the emission region to be located within 0.03 pc of the central engine, likely near the broad-line region (BLR). Additionally, two highest-energy photons were detected with energies of 46.4 GeV (on 57739.6 MJD) and 42.5 GeV (on 59161.9 MJD), observed outside the peak flaring activity. The fractional variability shows an overall increasing trend from UV/optical to $\gamma$-ray bands, with a noticeable dip in the X-ray range, consistent with the shape of the broadband spectral energy distribution (SED). The flux distributions during flares exhibit log-normal or double log-normal behavior, suggesting multiplicative variability processes and evolving emission zones. Cross-correlation analysis reveals a strong positive correlation between the $\gamma$-ray and X-ray bands, with X-rays lagging by 42.5 days. Broadband SED modeling across different flux states supports a one-zone leptonic scenario, with $\gamma$-ray emission produced via external Compton scattering of IR and BLR photons. High-flux states show harder electron spectra, elevated break energies, and reduced magnetic fields-features consistent with efficient particle acceleration and Compton dominance.
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All authors Sajad Ahanger, Shah Zahir, Sunder Sahayanathan, Naseer Iqbal, Zahoor Malik, Aaqib Manzoor

High Energy Astrophysical Phenomena

Towards gravitational wave parameter inference for binaries with an eccentric companion

Kai Hendriks, Lorenz Zwick, Pankaj Saini et al. (+2 more)

We introduce a complete model for dephasing due to line-of-sight acceleration (LOSA) in gravitational wave (GW) signals from stellar-mass binary black holes (BBHs) in three-body systems. Our prescription provides curvature- and projection-dependent phase features that are not recovered by local-expansion-based treatments. We perform parameter-space surveys and mock parameter inferences assuming the nominal sensitivity of the Einstein Telescope (ET) to identify the regime where the time-varying LOSA allows for separate constraints on the outer orbital parameters, in particular the tertiary mass and distance. We estimate that ET may detect a few to tens of such systems per year, provided that all binaries merge dynamically, and demonstrate that these constraints can be used to directly discriminate between a dynamical and AGN origin for BBHs. Finally, we reanalyse the GW190814 event and four O4a events finding no evidence for LOSA, with the previously claimed LOSA in GW190814 disappearing when a sufficiently long data segment is used.
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All authors Kai Hendriks, Lorenz Zwick, Pankaj Saini, János Takátsy, Johan Samsing

Astrophysics of Galaxies

MIGHTEE: The evolving radio luminosity functions of star-forming galaxies to $z\sim 4.5$ and the cosmic history of star formation

Nijin J. Thykkathu, Matt J. Jarvis, Imogen H. Whittam et al. (+9 more)

A key question in extragalactic astronomy is how the star-formation rate density (SFRD) evolves over cosmic time. A powerful way of addressing this question is using radio-continuum observations, where the radio waves are unaffected by dust and are able to reach sufficient resolution to resolve individual galaxies. We present an investigation of the 1.4 GHz radio luminosity functions (RLFs) of star-forming galaxies (SFGs) and Active Galactic Nuclei (AGN) using deep radio continuum observations in the COSMOS and XMM-LSS fields, covering a combined area of $\sim 4\,\mathrm{deg}^2$. These data enable the most accurate measurement of the evolution in the SFRD from mid-frequency radio continuum observations. We model the total RLF as the sum of evolving SFG and AGN components, negating the need for individual source classification. We find that the SFGs have systematically higher space densities at fixed luminosity than found in previous radio studies, but consistent with more recent studies with MeerKAT. We attribute this to the excellent low-surface brightness sensitivity of MeerKAT. We then determine the evolution of the SFRD. Adopting the far-infrared - radio correlation results in a significantly higher the SFRD at $z > 1$, compared to combined UV and far-infrared measurements. However, using more recent relations for the correlation between star-formation rate and radio luminosity, based on full spectral energy distribution modelling, can resolve this apparent discrepancy. Thus radio observations provide a powerful method of determining the total SFRD, in the absence of dust-sensitive far-infrared data.
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All authors Nijin J. Thykkathu, Matt J. Jarvis, Imogen H. Whittam, C. L. Hale, A. M. Matthews, I. Heywood, Eliab Malefahlo, R. G. Varadaraj, N. Stylianou, Chris Pearson, Nick Seymour, Mattia Vaccari

Astrophysics of Galaxies

The eJWST active galactic nucleus observation catalogue

Virginia Lenk, Alvaro Labiano, Chiara Circosta et al. (+2 more)

Context. The European Archive of the James Webb Space Telescope (eJWST) provides access to all data collected by the James Webb Space Telescope (JWST). JWST's capabilities span from studying early universe galaxy formation to probing exoplanet atmospheres. Specifically, for Active Galactic Nuclei (AGN), JWST offers unparalleled opportunities, enabling investigation into AGN phenomena with unprecedented detail through high-resolution imaging, spectroscopy, and photometric data. Aims. This study aims to compile and release a catalogue of all AGN observations conducted with JWST. Using eJWST, we systematically filter and organize these observations to facilitate access and retrieval of all of JWST's data products related to AGNs. Our goal is to provide the community with a valuable resource for their research. Methods. We compiled the AGN observations in eJWST using specific keywords set by the principal investigators in their proposals, manually reviewing the approved programs of JWST, as well as cross-matching all available observations with available AGN catalogues such as the Million Quasar catalogue, the SDSS MaNGA AGN catalogue, the CDFS catalogue, and others. Results. The resulting catalogue contains a total of 3,242 individual AGNs included in JWST observations. This is one of the first extensive collections of AGN observations from the JWST. It includes detailed information about the targets (name, coordinates, redshift), specifics of the JWST observations (instrument, aperture, filter, etc.), and provides links for data downloads.
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All authors Virginia Lenk, Alvaro Labiano, Chiara Circosta, Almudena Alonso-Herrero, Dominika Wylezalek

Astrophysics of Galaxies

Small scale turbulence alongside with large scale turbulence in a z=1.87 star Forming Galaxy with outflowing wind, revealed by Multi-point structure functions

Itzhak Goldman

Recently, Goldman (2024) obtained evidence for a large scale compressible, Burgers turbulence in the ism of a gravitationally lensed, star-forming galaxy at $z = 1.87$, with an outflowing wind. The turbulent timescale on the largest spatial scale has been found to be ~500 Myr . This together with the large spatial scale of~ 6.4 kpc suggest a large scale generating mechanism (such as tidal interaction or merger) that lasted for ~500 Myr. On the other hand, the outflowing wind is much younger and is probably the result of the intense star formation. Therefore, could it be that the star formation drives also turbulence on small scales? In the present work we utilize multi-point second order structure functions to find whether there exists also a small scale turbulence in this galaxy, and if so, try to identify its drivers. We obtained evidence for small scale turbulence whose largest spatial scale ~240 pc for the nebular gas velocity field and ~ 290 pc$ for the outflowing wind velocity field. These values suggest that stellar sub clumps or giant star clusters with an high concentration of young massive stars could be responsible for both the outflow and for the small scale turbulence.
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Earth and Planetary Astrophysics

ExoMiner++ 2.0: Vetting TESS Full-Frame Image Transit Signals

Miguel J. S. Martinho, Hamed Valizadegan, Jon M. Jenkins et al. (+4 more)

The Transiting Exoplanet Survey Satellite (TESS) Full-Frame Images (FFIs) provide photometric time series for millions of stars, enabling transit searches beyond the limited set of pre-selected 2-minute targets. However, FFIs present additional challenges for transit identification and vetting. In this work, we apply ExoMiner++ 2.0, an adaptation of the ExoMiner++ framework originally developed for TESS 2-minute data, to FFI light curves. The model is used to perform large-scale planet versus non-planet classification of Threshold Crossing Events across the sectors analyzed in this study. We construct a uniform vetting catalog of all evaluated signals and assess model performance under different observing conditions. We find that ExoMiner++ 2.0 generalizes effectively to the FFI domain, providing robust discrimination between planetary signals, astrophysical false positives, and instrumental artifacts despite the limitations inherent to longer cadence data. This work extends the applicability of ExoMiner++ to the full TESS dataset and supports future population studies and follow-up prioritization.
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All authors Miguel J. S. Martinho, Hamed Valizadegan, Jon M. Jenkins, Douglas A. Caldwell, Joseph D. Twicken, Ben Tofflemire, Marziye Jafariyazani

Cosmology and Nongalactic Astrophysics

Dark Energy Survey: DESI-Independent Angular BAO Measurement

J. Mena-Fernández, S. Avila, A. Porredon et al. (+80 more)

We present a measurement of the angular baryon acoustic oscillation (BAO) scale from the completed Dark Energy Survey (DES) dataset excluding the area of overlap with the Dark Energy Spectroscopic Instrument (DESI). We follow the same methodology and validation process as in the DES year 6 (Y6) BAO analysis. We interpret the impact of this measurement in the context of the statistical preference for $w_0w_a$ cold dark matter (CDM) over $\Lambda$CDM when combined with DES Y5 Type Ia supernovae (SN), Planck Cosmic Microwave Background (CMB) and DESI BAO. Based on our previous work, using the full Y6 DES BAO sample, in combination with SN, CMB and DESI data release 1 (DR1) BAO, added $0.3\sigma$ in this preference (from $3.7\sigma$ to $4.0\sigma$), but this ignored possible correlations between datasets. Using our new DESI-independent DES BAO likelihood instead, we find a smaller increase in the statistical preference for $w_0w_a$CDM, from $3.7\sigma$ to $3.8\sigma$ when using DESI DR1 BAO, and from $4.0\sigma$ to $4.1\sigma$ when updating to the more recent DESI data release 2 (DR2) BAO. These significances reduce to $3.1\sigma$ when using the new calibrated DES SN-Dovekie. Alongside this work, we publicly release BAOfit\_wtheta, the BAO fitting code for the angular correlation function used in the DES Y6 BAO analysis.
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All authors J. Mena-Fernández, S. Avila, A. Porredon, H. Camacho, J. Muir, E. Sanchez, M. Adamow, K. Bechtol, R. Camilleri, G. Campailla, T. M. Davis, N. Deiosso, C. Doux, A. Drlica-Wagner, A. Ferté, R. A. Gruendl, W. G. Hartley, A. Pieres, M. Raveri, E. S. Rykoff, I. Sevilla-Noarbe, P. Shah, E. Sheldon, M. Vincenzi, B. Yanny, T. M. C. Abbott, M. Aguena, S. Allam, O. Alves, F. Andrade-Oliveira, J. Annis, D. Bacon, J. Blazek, S. Bocquet, D. Brooks, A. Carnero Rosell, J. Carretero, F. J. Castander, R. Cawthon, L. N. da Costa, M. E. da Silva Pereira, J. De Vicente, S. Desai, H. T. Diehl, B. Flaugher, J. Frieman, J. García-Bellido, M. Gatti, D. Gruen, G. Gutierrez, K. Herner, S. R. Hinton, D. L. Hollowood, K. Honscheid, D. Huterer, N. Jeffrey, K. Kuehn, O. Lahav, S. Lee, J. L. Marshall, F. Menanteau, R. Miquel, J. J. Mohr, J. Myles, R. L. C. Ogando, A. Palmese, W. J. Percival, A. A. Plazas Malagón, M. Rodriguez-Monroy, A. Roodman, S. Samuroff, D. Sanchez Cid, B. O. Sánchez, T. Shin, M. Smith, M. Soares-Santos, E. Suchyta, M. E. C. Swanson, D. L. Tucker, V. Vikram, A. R. Walker, N. Weaverdyck, M. Yamamoto