Astrophysics of Galaxies
Mass Segregation in the CMZoom Survey
Stefania Schuler, Jen Wallace, Cara Battersby et al. (+5 more)
We employ a Minimum Spanning Tree (MST) approach to characterize the spatial distribution and mass segregation of compact millimeter continuum sources within the Central Molecular Zone (CMZ) of the Milky Way. We use a modified form of the complete version of the 1.3 mm
dust continuum catalog from the CMZoom survey, which identifies 685 compact sources with typical effective radii of $\sim0.1$ pc. For 22 of 35 CMZ clouds, we calculate the thermal and turbulent Jeans lengths and masses, and determine that compact source separations, as well as compact source masses, are more consistent with thermal fragmentation at $\sim0.1$ pc size scales. We construct the mass segregation ratios for compact sources in 17 CMZ clouds and determine that 5 of the analyzed clouds display some form of mass segregation ($\Lambda_{MSR} > 1.5$), while the remaining clouds show either inverse mass segregation ($\Lambda_{MSR} < 0.75$), or no evidence of true mass segregation ($0.75 < \Lambda_{MSR} < 1.5$). Finally, we find that although some actively
star-forming clouds do exhibit mass segregation, other similarly active clouds do not, indicating an unclear correlation with evolutionary stage for
star forming clouds in the CMZ, given the current available data.
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All authors Stefania Schuler, Jen Wallace, Cara Battersby, H. Perry Hatchfield, Robert Gutermuth, Xing Lu, Suinan Zhang, Qizhou Zhang
High Energy Astrophysical Phenomena
A Three-Dimensional Tomographic Reconstruction of the Galactic Cosmic-Ray Proton Density
Hanieh Zandinejad, Jakob Roth, Vo Hong Minh Phan et al. (+7 more)
Cosmic rays (CRs) are a ubiquitous non-thermal component of the interstellar medium (ISM). A data-driven three-dimensional (3D) map of their distribution is essential for understanding CR transport and constraining the spatial distribution of their sources. In this work, we reconstructed the 3D spatial distribution of the
Galactic cosmic-ray
proton (CRp) density. We model the diffuse gamma-ray emission arising from inelastic hadronic interactions between CRps and interstellar gas. Using a map of
dust-correlated diffuse gamma-ray emission based on ten years of
Fermi-LAT observations together with a three-dimensional gas density model, we infer the spatial CRp distribution through a morphological matching approach. The logarithmic CRp density field is described by a Gaussian process defined on a spherical-times-radial grid, while both the field and its correlation structure are inferred simultaneously using Iterative Charted Refinement. The posterior distribution of the reconstructed 3D CRp density field is approximated using
geometric variational inference. The reconstructed CRp density exhibits a smooth but spatially structured distribution with a limited dynamical range across the
Galactic disk. We find a moderate enhancement of the CRp density toward the inner
Galaxy. The inferred normalization at the
Solar position is consistent with local CR measurements by the AMS-02 instrument.
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All authors Hanieh Zandinejad, Jakob Roth, Vo Hong Minh Phan, Gordian Edenhofer, Philipp Frank, Philipp Mertsch, Ralf Kissmann, Andrés Ramírez, Laurin Söding, Torsten A. Enßlin
High Energy Astrophysical Phenomena
Polarized 3D Synthetic Turbulence I: Magnetic Field Line Random Walk
Matthieu Bouchet, Yoann Génolini, Silvio S. Cerri et al. (+2 more)
The behavior of
magnetic field lines in a turbulent
plasma is a key property of the medium, with important consequences for
plasma dynamics and charged-particle transport. We study the
diffusion properties of
magnetic field lines in synthetic
turbulence featuring different polarization configurations for the
magnetic perturbations, as prescribed by the existing magnetohydrodynamic modes (namely, Alfvénic and magnetosonic). These turbulent field realizations are then compared with the isotropic (or, random) polarization case, which is the one typically adopted in the literature. We construct polarized synthetic
turbulence simulations and study the properties of field lines through the running
diffusion coefficient. Our key findings can be summarized as follow: (i) field line wandering is strongly dependent on polarization configurations, (ii) we unveil that the sub-diffusive phase of field line is highly dependent on the polarization and is well reproduced by theoretical predictions based on Corrsin's hypothesis in the low
turbulence level regime, (iii) in particular the scaling of the asymptotic
diffusion coefficient in magnetosonic-like polarization is $(\delta B/B)^4$ at odd with the $(\delta B/B)^2$ scaling found in the quasi-linear regime for random polarization, (iv) interestingly we note that the subdiffusive phase of field line transport in the magnetosonic-like polarization follows closely the one observed in recent high resolution MHD
turbulence simulations, we end giving a word of caution when FL transport is investigated in such simulations.
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All authors Matthieu Bouchet, Yoann Génolini, Silvio S. Cerri, Alexandre Marcowith, Philipp Mertsch
Earth and Planetary Astrophysics
Follow the wobble: Statistical methods to detect astrometric binary asteroids in Gaia FPR
Luana Liberato, Paolo Tanga, David Mary et al. (+7 more)
In a previous article, we obtained the first-ever list of astrometric binary asteroid candidates. Some of these candidates have now been confirmed. In that previous work, however, the details of the statistical methods were not provided. Our first aim is to provide methodological details and performance evaluation of the approach used for detecting binaries. Our second aim is to establish an updated list of binary asteroid candidates from
Gaia FPR astrometric residuals exploration, where we account for the statistical properties of FPR data. We account for the astrometric uncertainties from FPR and we refine the statistical model of the data, which we use in MC simulation to evaluate the strength of the individual detections; we set up a trend detection method in the residuals and apply a dedicated period search
algorithm; we update the statistical selection process to build the list of candidates; we set up a method for detecting objects in multiple windows of consecutive observation; we refine the method for confidence interval estimation of these parameters and we better constrain the physical parameter selection. We detect 343 binary asteroid candidates corresponding to 410 windows of consecutive observations in the astrometric data. We show that in noise-only control simulations, the typical number of detections is 88% lower than in the FPR data. We also detect 9 known binaries, 25 candidates overlapping with the Pan-STARSS survey and 99 overlapping with our previous binary search in DR3. Finally, we report the detection of 45 objects with trends in residuals suggestive of wide binary systems. Our results and analyses demonstrate that although detecting binary asteroids is a difficult problem due to their low signal level, the proposed method is likely to provide a reliable list of detections, including systems poorly accessible to conventional techniques.
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All authors Luana Liberato, Paolo Tanga, David Mary, Raphael Lallemand, Ziyu Liu, Benoit Carry, Josselin Desmars, Daniel Hestroffer, Kate Minker, Alexandros Siakas
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Dimming of Photon Ring due to Photon-Axion Conversion around Kerr Black Holes
Rahul Dhyani, Sauvik Sen, Indrani Banerjee et al. (+2 more)
We investigate
photon-
axion conversion in the vicinity of rotating Kerr black holes where strong
gravity traps
photons on near-circular trajectories, effectively enhancing the path length. We explore the observable signatures of such a conversion near the
photon region. The process, driven by ambient
magnetic fields, is significantly more efficient around supermassive black holes such as M87*, since the luminosity of
photons increases with the mass of the BH. By numerically evaluating
photon path lengths (on which the conversion depends), we analyze how key parameters-
photon frequency,
axion mass,
photon-
axion coupling,
magnetic field strength,
plasma density, and black hole
spin-affect the conversion probability and the resultant dimming of
photon spectral luminosity. We find that the conversion is most efficient at high frequencies (X-rays and gamma rays), while the frequency window associated with efficient conversion widens with an increase in the
photon-
axion coupling and a decrease in the electron density and the
axion mass. The magnitude of dimming of the
photon spectral luminosity depends primarily on the
magnetic field, the
photon-
axion coupling and the BH
spin. Our study reveals that rotating black holes generally exhibit enhanced dimming compared to static ones. Thus, if future
telescopes achieving a resolution $\sim 10^{-5}$ arcsec in the X-ray/gamma-ray band detect a dimming of the
photon spectral luminosity, then they can provide interesting constraints on the
axion mass and its coupling with
photons.
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All authors Rahul Dhyani, Sauvik Sen, Indrani Banerjee, Ashmita Chakraborty, Arindam Chatterjee
High Energy Astrophysical Phenomena · Cross-listed from physics.atom-ph
X-ray and extreme-ultraviolet spectra from collisions of Ar$^{18+}$ and O$^{8+}$ ions with neutrals
Stepan Dobrodey, Chintan Shah, Sonja Bernitt et al. (+4 more)
We present measurements of K-shell x-ray emission following charge exchange of fully ionized argon with various neutral gaseous targets at small collision energies inside an electron beam ion trap. We also resolve the principal
quantum number of electron capture in extreme-ultraviolet spectra from initially bare and hydrogen-like oxygen ions held in the same trap. We analyze discrepancies between these as well as previous measurements with theoretical models based on the multichannel Landau-Zener approach.
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All authors Stepan Dobrodey, Chintan Shah, Sonja Bernitt, Ming Feng Gu, Liyi Gu, Thomas Pfeifer, José R. Crespo López-Urrutia
Astrophysics of Galaxies
Dwarf Galaxy Constraints on Interacting Fermionic Dark Matter
Bihag Dave and Raghuveer Garani
Dwarf galaxies in the Local Group offer a way to test dark matter (DM) models against
stellar kinematic data. In this work, we study degenerate fermionic DM in two cases: the standard non-interacting
Fermi gas, and an interacting degenerate DM fluid described by a phenomenological equation of state motivated by interacting
Fermi systems. These interactions modify the compressibility of the DM fluid and, in some regions of parameter space, lead to mechanically unstable branches that must be treated through a Maxwell construction. We solve the corresponding non-relativistic hydrostatic equations consistently and compute the line-of-sight velocity-dispersion profiles using the spherical Jeans equation. We then perform MCMC fits to eight classical Milky Way
dwarf spheroidal
galaxies. The data favor DM
fermion masses in the range $100$–$300\,{\rm eV}$. We find that the interacting and non-interacting equations of state give broadly similar posterior distributions for the
fermion mass, central density, and
stellar anisotropy. Current data therefore do not strongly prefer an interacting equation of state over the free degenerate
Fermi-gas, thereby excluding large deviations from the non-interacting limit.
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Earth and Planetary Astrophysics
Energetic Feasibility of Redirecting Trans-Neptunian Objects onto Mars-Impacting Orbits: Continuous Thrust and Gravity Assist Trajectories
Ryszard Gabryszewski, Leszek Czechowski and Arkadiusz Hess
We assess the dynamical feasibility of redirecting small volatile-bearing trans-Neptunian objects (TNOs) onto Mars-impacting orbits using continuous low-thrust propulsion and a single
gravity-assist encounter. The study considers two representative dynamical classes: classical Kuiper Belt–like and Scattered Disk–like initial orbits, and determines the minimum characteristic velocity increment $\Delta V$ required to drive the objects onto a Mars-impacting trajectory within a specified transfer time $\Delta T$. The dynamics is modelled in the two-body problem with a fixed maximum low thrust included, allowing the computed $\Delta V$ to represent a dynamical lower bound independent of specific propulsion-technical implementation. Three trajectory classes are investigated: (i) inward spiral transfer, (ii) time-dependent thrust-direction steering optimized via global evolutionary
algorithms, and (iii) hybrid transfers combining low thrust with a single Neptune flyby. Pure spiral trajectories yield very high velocity expenditures ($\Delta V \gtrsim 22~\mathrm{km~s^{-1}}$) and millennia durations, confirming that monotonic inward migration is dynamically inefficient for TNO redirection. In contrast, optimized steering strategies systematically increase orbital eccentricity and achieve Mars-impacting geometries with $\Delta V \approx 2.5$–$3.2~\mathrm{km~s^{-1}}$ over 380–540 yr timescales. A single Neptune encounter further reduces the total $\Delta V$ in favourable cases, with minimum values falling below those of direct optimized transfers. These results establish a quantitative lower bound on the energy cost of importing volatiles from the outer
Solar System to Mars, showing that controlled redirection is feasible under modest $\Delta V$ budgets when target bodies are chosen from favourable regions of orbital phase space.
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Solar and Stellar Astrophysics
Evidence of Radius Inflation Based on 50 Transiting Brown Dwarfs and Low-mass Stellar Companions
Aarushi Mehrotra, Chih-Chun Hsu, Jason J. Wang et al. (+2 more)
Statistical assessment of
stellar parameters enables validation and improvements in theoretical models. We compiled a sample of 85 transiting
stellar and substellar companions, with masses ranging from $\sim$13-100 $M_\mathrm{Jup}$. We focus on analyzing 50 transiting companions with robust ages and model constraints, and evaluate the degree of radius inflation versus mass, separation,
equilibrium temperature, and
metallicity. Our evaluation of the differences between measured and model radii indicates an $8.7\pm1.9$% radius inflation for the full sample, at $4.6\sigma$ discrepancy, validating the existence of radius inflation at a population level in transiting brown
dwarfs. For brown
dwarfs at separations $\leq 0.05$ au, we find an even higher radius inflation, with a median inflation of $16\pm6$% at $2.7\sigma$, and the inflation decreases toward wider separations, likely due to reduced
stellar irradiation. Finally, we provide our compilation for the community to use.
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All authors Aarushi Mehrotra, Chih-Chun Hsu, Jason J. Wang, Christopher A. Theissen, Adam J. Burgasser
Cosmology and Nongalactic Astrophysics
Towards precision cosmology with Void x CMB correlations (II): Impact of mock catalogs on the Void x CMB lensing signal
Mar Pérez Sar, Carlos Hernández Monteagudo, András Kovács et al. (+2 more)
Gravitational
lensing by large-scale structure imprints secondary anisotropies on the
Cosmic Microwave Background (CMB) that can be exploited to probe cosmology. In particular,
cosmic voids produce a characteristic
lensing signature detectable through Void x CMB cross-correlations. This signal has been robustly measured in the past but its cosmological constraining power remains limited by the incomplete knowledge of how methodological choices affect its measurement and by its uncertain dependence on cosmological parameters. Using a set of validated Roman mock catalogs, we first quantify how mock construction impacts the measured signal and then forecast the capabilities of Roman, in combination with current and upcoming CMB surveys such as Planck, SO and CMB-S4-like experiments. We analyze the signal-to-noise ratio (S/N) for different void definitions (2D and 3D), stacking approaches (rescaled versus non-rescaled profiles), CMB map filtering schemes and noise levels. In contrast to
galaxy and void statistics, we find that the Void x CMB
lensing signal is less sensitive to the choice of mock catalog, indicating that future tensions with data are unlikely to stem from mock inaccuracies alone. The highest S/N is achieved for 2D voids with rescaled profiles. We forecast S/N ~13$\sigma$ (8$\sigma$) for 2D (3D) Roman voids combined with Planck, increasing to 22$\sigma$ (13$\sigma$) for SO and 31$\sigma$ (18$\sigma$) for CMB-S4-like surveys. While the cosmological dependence of this observable remains to be quantified, Roman together with next-generation of LSS and CMB surveys opens a path toward the first direct cosmological constraints from Void x CMB
lensing.
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All authors Mar Pérez Sar, Carlos Hernández Monteagudo, András Kovács, Alice Pisani, Yun Wang
Solar and Stellar Astrophysics
HWO Target Stars and Systems: Activity and Rotation Catalog (ARC) of Potential Target Stars for the Habitable Worlds Observatory
Tara Fetherolf, Arvind F. Gupta, Elisabeth R. Newton et al. (+7 more)
A major goal of the Habitable Worlds Observatory (HWO) is to precisely characterize
exoplanets and their atmospheres. However,
magnetic activity from an
exoplanet's host
star can complicate measurements of both the
stellar and planetary properties, and
stellar activity can be an important factor in our interpretation of the evolutionary history of an
exoplanet. In this work, we assess the extent to which
magnetic activity has been characterized for potential HWO target
stars by collating archival measurements of relevant observables as published in a broad range of photometric and spectroscopic
datasets. We describe our data collection strategy, provide an overview of currently known activity and rotation properties in the Activity and Rotation Catalog (ARC) for potential HWO target
stars, and briefly review known relationships between
stellar inclination, rotation, activity, and age. Overall, we find that
stellar activity (S-index and R'HK) and rotation (v sin i and Prot) properties have been measured for at least 70% systems that are currently of high interest as potential HWO atmospheric characterization targets. However,
stellar activity is temporal in nature, such that activity properties should be regularly monitored in order to remain up-to-date for informing future observations. In particular, we find that
stellar activity cycles are measured for fewer than 20% of high interest potential HWO target
stars. Measuring a
star's activity cycle is critical for anticipating times when higher levels of
magnetic activity may occur during planned HWO observations, which may interfere with measuring precise
exoplanet atmospheric characteristics.
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All authors Tara Fetherolf, Arvind F. Gupta, Elisabeth R. Newton, Andrea P. Buccino, Jennifer A. Burt, Jose A. Caballero, Sebastian Carrazco-Gaxiola, Mariela C. Vieytes, Natalie R. Hinkel, Eric E. Mamajek
Solar and Stellar Astrophysics
Search for radio polarization in the particle-accelerating colliding-wind binaries WR 147 and HD 167971
A. B. Blanco, M. De Becker, P. Benaglia et al. (+1 more)
Particle-accelerating colliding-wind binaries (PACWBs) are multiple systems of massive
stars in which strong
stellar winds collide, accelerating particles to relativistic energies. This population of relativistic particles emits NT radiation, including synchrotron radiation in the
radio domain. This emission is expected to be linearly polarized, but the polarization signature has not yet been detected for a PACWB. Our objective is to quantify the linear polarization of synchrotron radiation in two well-known PACWBs and to interpret our measurements within the framework of the physics of these specific NT emitters. We observed the PACWBs WR 147 and HD 167971 with the Very Large Array (VLA)
radio interferometer in the frequency bands L and C (1-2 and 4-8 GHz, respectively), where synchrotron emission is expected to be more prominent. We performed polarization calibration and analyzed the resulting Stokes maps. We did not detect any polarization signature for either of the two targets in either of the two bands, even when considering narrower bands to mitigate the effect of bandpass depolarization. The most conservative upper limit on the polarization degree is on the order of 1% for both targets. The lack of linear polarization for the two targets is likely attributable to a combination of effects, including the turbulent nature of the
magnetic field in the synchrotron-emitting region, and depolarization processes based on Faraday rotation that are certainly active in these sources. Their complex geometry, unresolved by the VLA at these frequencies, is most likely to lead to beam depolarization. We emphasize that, in contrast to other canonical synchrotron sources, PACWBs are also subject to thermal dilution. This is especially relevant for systems with
stars whose winds are strong enough to contribute copiously to thermal emission, such as those harboring a Wolf-Rayet component.
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All authors A. B. Blanco, M. De Becker, P. Benaglia, S. del Palacio
Solar and Stellar Astrophysics
Decoding the Radial Velocity Signatures of Solar Faculae with 3D MHD Simulations
Florian Kröll, Sowmya Krishnamurthy, Alexander Shapiro et al. (+8 more)
We model the
solar radial velocity (RV) signal induced by faculae, the dominant contributor to RV variability in Sun-like
stars. We use a representative case of a facular patch transiting the visible
solar disk as the Sun rotates to disentangle various physical effects contributing to the RV signal. Our approach is based on 3D radiative magnetohydrodynamic (MHD) simulations of the
solar photosphere and upper convection zone with the MURaM code and spectral synthesis with the MPS-ATLAS code. We show that the faculae-induced RV strongly depends on the facular position on the
solar disk. Near disk centre, facular
magnetic fields inhibit the convective blueshift and thus produce a relative
redshift of the
solar spectrum. Surprisingly, when located closer to the limb, namely at heliocentric angles greater than about $60^\circ$, faculae produce a relative blueshift. This transition from
redshift to blueshift is caused by the effect of
magnetic fields on horizontal flows, which dominate the signal near the limb, and on the visibility of these flows. In combination with
solar rotation, this centre-to-limb dependence of the facular effect leads to a complex RV profile during the facular transit and, in particular, to a phase lag between the maximum of the RV signal and the facular crossing of the central meridian. We further show that, in contrast to
stellar reflex motion, the facular signal strongly depends on the spectral line in which it is measured.
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All authors Florian Kröll, Sowmya Krishnamurthy, Alexander Shapiro, Andrew Collier Cameron, Veronika Witzke, Sami Khan Solanki, Ignasi Ribas, Sergiy Shelyag, Greg Kopp, Nina Elisabeth Nèmec, Sophie Stucki
Cosmology and Nongalactic Astrophysics
The impact of evolving dark energy on the Weyl potential measured from the Dark Energy Survey Year 3 data
Benedetta Rosatello, Gen Ye, Maria Berti et al. (+3 more)
Measurements from the Dark Energy Survey (DES) Year 3 data have shown that the Weyl potential – the sum of the spatial and temporal distortions of the geometry – evolves more slowly than predicted by General Relativity, assuming a $\Lambda$CDM background
evolution. An evolving dark energy with a phantom crossing, as preferred by the Dark Energy Spectroscopic Instrument (DESI), is expected to decrease the depth of the gravitational potentials through a stronger acceleration than in $\Lambda$CDM, potentially solving the tension with General Relativity. In this paper, we show that $w_0w_a$CDM models indeed reduce the tension with respect to $\Lambda$CDM, down to a level of $1.6-2.2\sigma$, depending on the treatment of CMB
lensing. This reduction is not due to an increase in the Weyl potential's uncertainties, but truly to the impact of the evolving background on the theoretical predictions in General Relativity. More data are needed to robustly determine if evolving dark energy fully explains the low value of the Weyl potential at intermediate
redshifts, or if modifications of
gravity or interactions in the dark sector are needed, which could simultaneously stabilize the phantom crossing indicated by DESI.
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All authors Benedetta Rosatello, Gen Ye, Maria Berti, Isaac Tutusaus, Nastassia Grimm, Camille Bonvin
Earth and Planetary Astrophysics
Scattered light signatures of flyby-induced warps in protoplanetary discs
Katie L. Milsom, Tim J. Harries and C. J. Nixon
We explore the observational signatures of flybys in scattered light images of protostellar discs. The warps are modelled using 1D warp propagation theory coupled to a fast radiative transfer code that simulates the shadows induced. We consider two scenarios, namely a flyby in a plane orthogonal to, and at an angle with, the disc plane. In both models the outer disc becomes warped (leading to a broad shadow in the outer disc) and the warp wave propagates back and forth (causing the shadow to oscillate). We find that the inner disc, although tilted, is not warped and is therefore not shadowed. For a low viscosity disc ($\alpha=10^{-4}$) the warp lasts for most of the disc's lifetime ($\tau \sim 10^6\,$years), and for $50\%$ of the time the azimuthal variance of the surface brightness from the scattered light images, $\sigma^2$, is above $0.01$, meaning that the shadow in the disc is significant. We find that a significant fraction of discs in nearby
star forming regions should have undergone a flyby sufficient to induce an observable warp, and that surveys of shadowed discs could provide a valuable probe of disc viscosity.
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High Energy Astrophysical Phenomena
JWST observations of a planetary nebula support jet-driven explosion of core-collapse supernova remnant RCW 103
Aleksei Klimov and Noam Soker
We show that the morphology of the core-collapse
supernova (CCSN) remnant RCW 103 is very similar to the morphology of the brightest regions in the recently released JWST IR images of the jet-shaped planetary nebula (PN) PMR 1, and conclude that two energetic pairs of jets shaped RCW 103, compatible with the jittering-jets explosion mechanism (JJEM). The PN PMR 1 IR image exhibits two opposite, large, and prominent ears with a narrow, faint region connecting them through the center, a pipe. Observations and simulations have shown that a pair of jets inflates such a pair of ears in PNe. The brightest regions of PN PMR 1 form two clumpy sectors, each shaped like a wide pizza slice, with a faint region between them; the CCSN remnant RCW 103 has a very similar morphology. We identify two shells in the X-ray image of RCW 103 and suggest that two close pairs of energetic jets shaped this CCSN remnant. We find only traces of two of the four expected ears in RCW 103. The ears in RCW 103 were already dispersed and are very faint. Deeper X-ray observations might detect them. Such energetically misaligned pairs of jets are compatible with the JJEM, which predicts that a few to about 20 pairs of jets are responsible for most CCSN explosions.
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Solar and Stellar Astrophysics
Iron Fluorescence in X-class Solar Flares: Aditya-L1/SoLEXS Observations
Abhilash R. Sarwade, K. Sankarasubramanian, Monoj Bug et al. (+5 more)
Iron fluorescence is produced by the irradiation of the
solar photosphere by coronal X-rays during
flares. This study presents the first comprehensive analysis of iron K$\alpha$ fluorescence characteristics in 47 X-class
flares observed during the inaugural year of the
Solar Low Energy X-ray Spectrometer (SoLEXS) on board India's Aditya-L1 mission. Leveraging the capability of modern silicon drift detectors (SDDs) for simultaneous broadband continuum and line measurements, the Fe K$\alpha$ flux and the exciting flux ($F_{>7.11 \text{ keV}}$) are quantified for each event, establishing a well-determined relationship between them across the sample. The derived fluorescence efficiencies exhibit a center-to-limb dependence consistent with theoretical models, offering a potential diagnostic to probe coronal source heights and viewing geometries. While statistical uncertainties currently limit the ability to track rapid height variations on short timescales, the mean fluorescence efficiency during the
flare peak provides a potential constraint on the effective coronal source height. However, this derivation remains subject to a fundamental degeneracy, as the estimated source height cannot be uniquely determined without assuming a specific value for the photospheric iron abundance. These findings demonstrate that SDDs, despite having lower spectral resolution than traditional
crystal spectrometers, provide a new diagnostic for the
solar iron fluorescence observations.
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All authors Abhilash R. Sarwade, K. Sankarasubramanian, Monoj Bug, Vaishali Sharan, Kiran Lakshmipathaiah, Ankur Kushwaha, M.C. Ramadevi, Smrati Verma
Solar and Stellar Astrophysics
Configuration of the $\xi$ Tau system constrained by multi-technique observations
M. Brož, P. Doležal, D. Vokrouhlický et al. (+8 more)
$\xi$ Tau is one of the most compact multiple
stellar systems, which is sufficiently close (67 pc) to be constrained by all kinds of observations. To better constrain its current configuration, we utilized new observational data: (i) photometry from TESS and astrometry from WDS, and (ii) our own photometry from the MOST spacecraft and spectroscopy from the CTIO observatory. [...] Given the hierarchical architecture of $\xi$ Tau, ((Aa+Ab)+B)+C, we detected the orbital
evolution on all time scales. Oscillations of periods $P$ occur on the shortest, orbital time scales ($P_1$, $P_2$); the variation of eccentricity $e_1$ is from 0 to 0.008, and of $e_2$ from 0.202 to 0.207, respectively. Oscillations of projected $i$, $\Omega$ are coupled, and occur on the secular time scale of about 7000 d. The inclination $i_1$ of the inner, eclipsing pair (Aa+Ab) changes from $86.1^\circ$ to $87.1^\circ$, which is clearly manifested in eclipse depths. There is also a long-term trend due to the outer orbit ($P_3 \doteq 18900\,{\rm d}$), with a perihelion passage (a `bump') of component C, which is manifested in radial velocities. The mutual inclinations between the three orbital planes, ${\simeq}\,0.5^\circ$ and $71^\circ$, are very different. Long-term stability is ensured by suppressing Kozai oscillations due to the fast precession rate $\dot\omega_2$. The best model requires
tidal dissipation in the inner binary (with the time lag of ${\sim}100\,{\rm s}$) and five components, where component C is a binary (Ca+Cb). Although the masses of the three components ($2.27$, $2.15$, $3.78\,M_\odot$) are now constrained to within 1%, the suspected binary (Ca+Cb), offset by $600\,{\rm mas}$, should be better characterized. A key question remains whether this bright
stellar system contains additional
dwarf or exoplanetary components with low masses. Continuing monitoring of $\xi$ Tau is highly desirable.
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All authors M. Brož, P. Doležal, D. Vokrouhlický, P. Harmanec, B. Barlow, H. Božić, J. Labadie-Bartz, R. Kuschnig, T. Kallinger, J. Matthews, D. Mourard
Astrophysics of Galaxies
Probing the ion-neutral drift velocity towards the L1544 prestellar core: Detection of ambipolar diffusion using N$_2$D$^+$ and para-NH$_2$D
Doris Arzoumanian, Silvia Spezzano, Tommaso Grassi et al. (+9 more)
The dynamical role of the
magnetic field in the
star formation process is tightly linked to the coupling between matter and the field. This coupling is due to the interaction between ions and neutrals in the partially ionized interstellar medium. When the ionization degree drops in the dense environment of prestellar cores, the
magnetic field and the matter may decouple, leading to differences in the infalling velocities of ions and neutrals known as ambipolar
diffusion. The onset of gravitational collapse resulting from ion-neutral decoupling has never been observed. The aim of this work is to search for signatures of ambipolar
diffusion within a prestellar core. We observed the deuterated N$_2$D$^+$ ion and the neutral para-NH$_2$D species towards the prototypical prestellar core L1544. These two species are ideal tracers of prestellar cores sampling the same high densities in the core interior. We compared the velocity centroid and linewidth maps of the ion-neutral pair. We find a mean ion-neutral velocity difference of $\sim$0.05 km/s towards the core. By comparing with predictions from self-consistent calculations of the ambipolar resistivity including
dust grain growth, we interpret the observed ion-neutral velocity difference in L1544 as a signature of ambipolar
diffusion. We do not detect a significant ion-neutral linewidth difference that may be attributed to the subsonic infall motions of the gas in L1544 and geometrical effects in the presence of inclination. These results emphasize the role of
dust grain growth at the prestellar core stage in setting the ambipolar resistivity and regulating the dynamical
evolution of dense cores towards their collapse into protostars. We propose that measurements of ion-neutral drift velocities provide new constraints on the total
magnetic field strength and the
dust size distribution within prestellar cores.
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All authors Doris Arzoumanian, Silvia Spezzano, Tommaso Grassi, Paola Caselli, Yusuke Tsukamoto, Haruka Fukihara, Yoshiaki Misugi, Felipe Alves, Jaime Pineda, Sigurd Jensen, Elena Redaelli, Alexei Ivlev
Solar and Stellar Astrophysics
Seismic signature of a magnetic field in the $\gamma$ Doradus star KIC 2309579
S. Ihallaine, J. Ballot, F. Lignières et al. (+4 more)
Internal
magnetic fields have recently been detected and measured in the radiative core of red
giant stars using asteroseismology. Being one of red
giant stars progenitors and exhibiting high radial order
gravity modes, $\gamma$ Doradus
stars are also good candidates to hold detectable
magnetic fields in their radiative envelope. We aim to detect internal
magnetic field in a rapidly rotating $\gamma$ Doradus
star for the first time, through its influence on the propagation of Kelvin gravito-inertial modes. We used the seismic variable $\delta K_a$, defined as a combination of Kelvin modes frequencies, which is sensible to the presence of a
magnetic field. Following the detection, we carried out a modelling of the
star oscillation spectrum considering a
magnetic component following a
Bayesian approach. We found a
magnetic signature into the radiative envelope of KIC 2309579. If located just above the core, in the layers that were previously convective, the
magnetic field would reach $\sim$ 4 kG.
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All authors S. Ihallaine, J. Ballot, F. Lignières, L. Ferrié, S. Charpinet, M. Galoy, G. Li
Astrophysics of Galaxies · Cross-listed from gr-qc
Dynamics of Binary System around a Supermassive Black Hole :Binary Scattering and Eccentric vZLK Oscillations
Kei-ichi Maeda and Hirotada Okawa
We study the dynamics of a binary orbiting a supermassive black hole (SMBH), focusing on both binary scattering in unbound orbits and eccentric von Zeipel-Lidov-Kozai (vZLK) oscillations in bound orbits. The motion is described in a local inertial frame in Kerr spacetime, where
tidal effects are encoded in the Riemann
curvature. For unbound (
parabolic and
hyperbolic) orbits, we identify four scattering regimes-adiabatic, tidally affected, chaotic, and disruptive-depending on the binary semi-major axis. As the binary becomes softer,
tidal interactions near periapsis lead to strong eccentricity excitation, large changes in the orbital parameters, and eventually chaotic behavior or
tidal disruption, with a sensitive dependence on the argument of periapsis. For eccentric bound (
elliptic) orbits, the vZLK mechanism differs qualitatively from the standard one, although the $z$-component of the angular momentum in the local inertial frame remains approximately conserved. The
evolution proceeds on a dynamical timescale and exhibits step-like changes driven by repeated periapsis passages, which can be interpreted as a sequence of scattering events. We refer to this behavior as scattering-type vZLK oscillations. The rotation of the SMBH also modifies the oscillation profiles, although its effect is less significant than the dependence on the initial orbital parameters. These results suggest a unified picture of periapsis-driven
tidal dynamics in
galactic nuclei.
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High Energy Astrophysical Phenomena
Pulsar timing solutions for 17 pulsars at 150 MHz from the Irish LOFAR station
D. J. McKenna, E. F. Keane, P. T. Gallagher et al. (+1 more)
Pulsar timing is a foundational part of
pulsar research to triage the most interesting systems and to characterise properties (rotational or otherwise) of the population of these extreme objects. Due to the efficiency of a number of sensitive and/or wide-field surveys in recent years, the number of new
pulsars discoveries is growing year-on-year, and most of these lack even basic timing parameter measurements. This work aims to demonstrate the capabilities of international Low Frequency Array (LOFAR) stations operating as single
telescopes to follow-up, time and characterise these sources, offering new insight into the emission properties of these
neutron stars, and support efforts to build timing models for these sources. Between 2020 and 2023 we used the local-mode allocation of the Irish LOFAR station to follow-up 33
pulsar candidates announced from various surveys at different observing frequencies to determine if an international LOFAR station has sufficient sensitivity to detect and time these sources. From the 33
pulsars selected, 22
pulsars were detected and 17 were selected for long-term monitoring across 590 hours of observing time. This has resulted in coherent timing solutions for all of these sources at 150 MHz – 7 of these have never had any reported timing solutions, the remaining 10 solutions agree well with announcements from others since the beginning of our project. For a fraction of sources announced by surveys each year, the 14 international LOFAR stations are well placed to follow-up survey candidates for long-term
pulsar monitoring beyond the standard timing campaigns performed at these
telescopes to date, reducing the pressure on observing time availability at these observatories, and enabling the full scientific potential of these
pulsars to be realised.
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All authors D. J. McKenna, E. F. Keane, P. T. Gallagher, J. McCauley
Astrophysics of Galaxies
The habitability trade-off: Chemical decoupling and quenching in massive galaxies
Ana Mitrašinović, Nataša Pavlov, Branislav Vukotić et al. (+1 more)
Massive
galaxies experience complex evolutionary processes, including mergers and gas
accretion, which can disrupt the chemical
equilibrium between their
stellar and gaseous components. Using the IllustrisTNG (TNG100) simulation at $z=0$, we investigated the prevalence and physical properties of such chemically decoupled systems within the massive
star-forming
galaxy population. We identify a substantial subpopulation ($\sim 31.5\%$ of the sample) that exhibits systematic
stellar-gas decoupling, characterised by a metal-rich
stellar component coexisting with a diluted gas reservoir. These non-
equilibrium galaxies are closely linked to recent merger activity and partial quenching, and display systematically suppressed
star-formation rates and reduced gas fractions, consistent with a transitional evolutionary phase. We then examined the implications of this phase for
galaxy-scale habitability prescriptions by applying a terrestrial
planet abundance proxy that combines
stellar mass, gas-phase
metallicity, and the rate of sterilising events. Despite their diluted gas reservoirs, non-
equilibrium galaxies dominate the high end of the inferred present-day habitability proxy distribution, exceeding
equilibrium systems by more than an order of magnitude. We interpret this as a habitability trade-off: the same gas dilution and quenching processes that reduce the efficiency of future terrestrial
planet formation simultaneously create a transient phase of suppressed radiation hazards for existing
planets. The Andromeda
galaxy (M31) shows qualitative similarities to this chemically decoupled population, suggesting that
galaxies exiting their peak
star-forming phase represent a distinct and highly relevant demographic for
galaxy-scale habitability.
Galactic habitability is therefore intrinsically time-dependent.
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All authors Ana Mitrašinović, Nataša Pavlov, Branislav Vukotić, Stanislav Milošević
Astrophysics of Galaxies
MICONIC: The multiphase circumnuclear region of Centaurus A as seen with JWST/MIRI MRS observations. I. Spectral inventory and properties of the warm molecular disk
L. Evangelista, P. Guillard, J. Martin et al. (+21 more)
Supermassive black holes power Active
Galactic Nuclei (AGN), injecting energy that regulates
accretion and shapes host
galaxies. We investigate the morphology, excitation, and kinematics of molecular hydrogen (H2) in the inner circumnuclear disk of Centaurus A, the nearest
radio galaxy. We present JWST/MIRI MRS integral-field spectroscopy of the central 170x100 pc2 at 0.3"-0.7" (5-12 pc) resolution, focusing on pure rotational H2 lines. The spectra show strong
nuclear continuum and bright H2 emission from S(1) to S(8), including the first S(8) detection in Centaurus A. Optically thin
nuclear lines enable maps of temperature, column density, and ortho-to-para ratio from spaxel-level excitation-diagram fitting. Warm H2 shows a complex morphology, dominating the central region where CO emission is weak or undetected. Low-excitation H2 lines trace an inhomogeneous ring with a 20-pc-radius cavity aligned with the jet's near side, suggesting that the jet affects the morphology of the molecular disk. Higher-excitation lines form filamentary structures around the AGN. Kinematics are rotational with an S-shaped distortion, indicating non-circular motions or a warped disk. A coherent, low-dispersion (70 km/s) streamer spirals inward. A power-law temperature distribution yields a warm (100-2000 K) H2 mass of (5.6+/-1.4)e5 Msun and a dynamical mass of 5e8 Msun within 100 pc. Shock excitation is supported by enhanced H2/continuum and H2/PAH ratios, elevated [Ne III]/[Ne II], and sub-
equilibrium ortho-to-para ratios (1.6-2.4). Turbulent dissipation can balance H2 cooling and likely dominates heating beyond 30 pc. In the inner 100 pc of Centaurus A, AGN feeding and feedback are linked: shocks excite H2, regulate the gas temperature, and prevent cooling below 100 K, explaining the weak CO emission and lack of a massive
outflow. These shocks may drive angular momentum loss and help fuel the
nucleus.
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All authors L. Evangelista, P. Guillard, J. Martin, P. Salomé, A. Alonso Herrero, L. Pantoni, L. Hermosa Muñoz, V. Buiten, A. Labiano, M. García-Marín, L. Colina, T. Böker, D. Dicken, M.J. Ward, G. Wright, P. van der Werf, S. Garcia-Burillo, M. Baes, A. Eckart, G. Östlin, D. Rouan, F. Walter, R. A. Riffel, M. Güdel
Cosmology and Nongalactic Astrophysics
Machine Learning Techniques for Astrophysics and Cosmology: Lyman-$\alpha$ forest
Jonás Chaves-Montero
The Lyman-$\alpha$ forest refers to the series of absorption features observed in the spectra of distant
quasars that are produced by neutral hydrogen in the intergalactic medium. Observed over a wide range of
redshifts with both ground- and space-based facilities, the Lyman-$\alpha$ forest provides a powerful probe of numerous physical processes, including the thermal state of intergalactic gas, the timing and
topology of
cosmic reionization, the expansion history of the Universe, the growth of
cosmic structure, massive
neutrinos, and the nature of dark matter. This chapter reviews the transformative impact of machine-learning techniques on Lyman-$\alpha$ forest analyses, particularly in overcoming the computational and methodological limitations of traditional approaches. We discuss a broad range of machine-learning applications, including the automated characterization of individual absorption systems, improved reconstruction of the intrinsic
quasar continuum, accelerated emulation of hydrodynamical simulations, and the development of simulation-based analyses, field-level inference methods, and three-dimensional reconstruction techniques for the underlying matter density field. As current and upcoming surveys continue to increase both the volume and precision of Lyman-$\alpha$ forest observations, ML-driven pipelines are becoming an essential component of next-generation astrophysical and cosmological analyses.
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Instrumentation and Methods for Astrophysics
Hostless extragalactic transients in Fink: Results from the ELEPHANT pipeline
R. Durgesh, P. J. Pessi, E. E. O. Ishida et al. (+1 more)
The ExtragaLactic alErt Pipeline for Hostless AstroNomical Transients (ELEPHANT), has been developed as a framework for filtering hostless candidates, in real time alert systems, and implemented as a filter in the Fink broker. ELEPHANT works on stamps and requires minimal information, thus allowing for fast identification of extragalactic transient events. In this work we evaluate the performance of the ELEPHANT pipeline by systematically analyzing flagged hostless candidates identified between 1 September 2023 and 31 December 2025. Our goal is to quantifying its accuracy and identify dominant sources of contamination. For each flagged candidate we collected additional information from multiple catalogues and archival repositories. We further examined their light-curve
evolution and astrometric consistency (coordinate dispersion over time) to refine source classification. Results. Out of 877 flagged events, 67 are confidently confirmed as genuinely hostless candidates, with no detectable host
galaxy in either existing catalogues or archival imaging, representing a high-purity sample of intrinsically faint or absent hosts. Additional 51 events are linked to visually identifiable hosts that are entirely absent from both catalogues and ZTF stamps. For the confirmed hostless subset, the inferred upper limits on host-
galaxy absolute magnitudes extend well below the luminosity range of typical
dwarf galaxies. The pipeline showed an overall accuracy of 0.84, with the majority of the classified flagged events being Type Ia
supernovae, and the second most detected class being Type I superluminous
supernova. ELEPHANT has been adapted to deal with the Rubin alert stream and has been processing its alerts since February 2026.
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All authors R. Durgesh, P. J. Pessi, E. E. O. Ishida, J. Peloton
Earth and Planetary Astrophysics
Maximum Lifetime of the Vegetative Biosphere
Jacob Haqq-Misra and Eric Wolf
We use a three-dimensional model to calculate steady-state climates at various intervals in Earth's future, across a parameter space of increasing insolation and decreasing CO$_2$ mixing ratio. Comparison with prior results shows an overestimation of warming by one-dimensional models when
solar constant is increased and CO$_2$ mixing ratio is fixed. We consider two future trajectories as limiting cases: strong weathering, in which surface temperature remains constant but CO$_2$ is drawn down; and weak weathering, in which CO$_2$ remains constant and surface temperature increases. Under strong weathering, we find the conventional 10 ppm CO$_2$ starvation limit for C4 photosynthesis that occurs at 1.35 Gyr; however, we suggest that crassulacean acid metabolism (CAM) photosynthesis could persist below this limit and note that aquatic macrophytes can utilize dissolved bicarbonate if atmospheric CO$_2$ is low. If we take the CO$_2$ starvation limit at 1 ppm instead, then the vegetative biosphere could continue until 1.84 Gyr. Thermal limits apply instead under weak weathering, in which Earth would be too hot for most land plants at 1.68 Gyr (>323 K) and too hot for all land plants (>338 K) at 1.87 Gyr. These lifetimes approach the moist and runaway greenhouse limits for Earth. We discuss other possible mechanisms for extending the lifetime of Earth's biosphere, noting that both technological intervention and evolutionary processes could enable life to adapt to a brightening sun.
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Instrumentation and Methods for Astrophysics
STARFIRE-2: Can we detect the global redshifted 21-cm signal from the cosmic dawn in Earth orbit?
Yogen Pranesh, Mayuri Sathyanarayana Rao and Saurabh Singh
Detecting the redshifted global 21-cm signal from the
cosmic dawn (CD) remains a major challenge due to strong terrestrial
Radio Frequency Interference (RFI), particularly dominated by Frequency Modulation (FM) transmissions in the 88-110 MHz range. While observations from the
radio-quiet lunar farside are ideal, Earth orbit offers an intermediate and simpler alternative that may mitigate several limitations of ground-based experiments. We assess the feasibility of detecting the global 21-cm signal from Earth orbit by quantifying FM-based RFI at different altitudes and orbital configurations. We present STARFIRE-2 (Simulation of TerrestriAl
Radio Frequency Interference in oRbits around Earth – 2), an
algorithm that estimates FM transmitter-based RFI intercepted by radiometers in orbit. The model constructs a global FM transmitter database and compensates for incomplete data using statistical methods. Using PRATUSH as the reference experiment, we simulate a range of orbital scenarios to identify configurations that minimize RFI and optimize sensitivity for global 21-cm detection. The
algorithm can also be adapted for other experiments. Simulations indicate that conducting such an experiment from Earth orbit is feasible for a thermal noise limited instrument placed in a low-Earth, near-polar orbit. Mock sky observations further demonstrate that most theoretically plausible
cosmic dawn 21-cm signals can be recovered with high confidence under these optimized orbital conditions.
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Solar and Stellar Astrophysics
Reconstruction of annual solar irradiance over the last three millennia
D. Temaj, N.A. Krivova, S.K. Solanki et al. (+2 more)
Solar irradiance measurements are limited to the last few decades, requiring reconstructions to assess
solar variability on longer timescales and its impact on Earth's
climate. We present the first physics-based reconstruction of total
solar irradiance (TSI) at annual resolution over the last three millennia. The reconstruction is obtained by extending the SATIRE-T model beyond the telescopic era using recently published, annually resolved sunspot number series derived from cosmogenic isotope records. This yields a continuous, physics-based TSI record extending from the satellite era back over the last three millennia, with annual resolution throughout the pre-telescopic period. Over the full three-millennia interval, the reconstructed TSI exhibits a maximum difference of $1.04_{-0.2}^{+0.14}\,\mathrm{W\,m^{-2}}$, defined as the difference between the maximum and minimum of the 50-yr running mean values.
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All authors D. Temaj, N.A. Krivova, S.K. Solanki, I.G. Usoskin, T. Chatzistergos
High Energy Astrophysical Phenomena
A Weak Fe K$\beta$ Emission Line in the Broad-Line Radio Galaxy 3C 111 Observed with XRISM: An Ionized Wind Absorption Feature?
Kouichi Hagino, Motoki Kino, Lukasz Stawarz et al. (+3 more)
We present the results of an observation of the broad-line
radio galaxy 3C 111 with the X-Ray Imaging and Spectroscopy Mission (XRISM). The unprecedentedly high spectral resolution of XRISM/Resolve revealed that the Fe K$\beta$ emission line is significantly weaker than expected from the Fe K$\alpha$ line. This feature may be explained by a blueshifted absorption line from an ionized wind overlapping the Fe K$\beta$ energy. The inferred
outflow velocity is 4600 km s$^{-1}$ or 17200 km s$^{-1}$, depending on whether the absorption feature is identified as Fe XXVI or Fe XXV, with the current data unable to distinguish between the two interpretations. Based on spectral modeling, the kinetic power of the wind is estimated to lie in the range 10$^{41}$-10$^{44}$ erg s$^{-1}$, although this estimate is subject to large uncertainties primarily due to the poorly constrained location of the absorber. The inferred wind power is smaller than the jet power of 3C 111 ($\sim 3\times 10^{44}$ erg s$^{-1}$), and is broadly consistent with theoretical expectations that the jet power exceeds that of disk winds.
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All authors Kouichi Hagino, Motoki Kino, Lukasz Stawarz, Kenzo Kawamura, Kazuhiro Hada, Hirofumi Noda