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Physics Astrophysics

astro-ph Watch Astrophysics

Wednesday 19 November

Astrophysics of Galaxies

Fossil group origins XIV: The radial orbits of A267

S. Zarattini, A. Biviano, I. Bartalucci et al. (+3 more)

Fossil groups (FGs) are groups or clusters of galaxies with a single, massive, central galaxy and with a clear lack of L* galaxies. The physical reason for their large magnitude gap (dm12) may arise from early FG formation, which allowed all L galaxies to merge with the central one, and/or it could be related to the fact that galaxies accreting on the FGs move on radial orbits, shortening their merging timescales. The latter properties could be linked with the peculiar position of FGs within the cosmic web. We determine the velocity anisotropy profile beta(r) of the fossil cluster A267, which is related to the orbital distribution of cluster galaxies. This is the first individual FG for which the orbital distribution of galaxies is determined. We aim to confirm previous findings based on stack samples that indicate that FGs, on average, host galaxies on more radial orbits than normal clusters. We started with a sample of 2315 redshifts in the field of A267 and we determined the membership for 329 of them. Of these, 174 are located within r200. We used them as tracers of the gravitational potential of the cluster to solve the Jeans equation using the MAMPOSSt algorithm. We thus obtained the cluster mass M(r) and beta(r) profiles. We also estimated M(r) from the X-ray data. A comparison of the MAMPOSSt and X-ray-determined M(r)s allows us to estimate the cluster hydrostatic mass bias, that is consistent with previous findings. The anisotropy parameter beta(r) indicates tangential orbits for the galaxies near the cluster centre and increasingly radial orbits in the external regions. We therefore confirm that FGs are characterised by more radial orbits for their member galaxies than the average cluster population. We speculate that this different orbital distribution might be an important element in creating a large dm12.
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All authors S. Zarattini, A. Biviano, I. Bartalucci, J. A. L. Aguerri, C. P. Haines, M. Girardi

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

Holographic Constraints on the String Landscape

Alek Bedroya and Paul J. Steinhardt

We show that holography imposes strong and general constraints on scalar field potentials in the string landscape, determined by the asymptotic structure of the underlying spacetime. Applying these holographic consistency conditions, we identify broad classes of scalar potentials that are incompatible with a well-defined dual description. These include potentials with extended plateaus, excessively steep or shallow asymptotics, certain zero crossings, and specific alignments of stable AdS minima in moduli space. In particular, making the standard assumption that the CFT dual to a stable AdS vacuum must be realized as a worldvolume theory of a brane in string theory, we show that the brane selects an infinite-distance limit in moduli space where parametric scale separation is forbidden. Furthermore, the steepness and positivity of the potential are restricted in that infinite distance direction. We also find that requiring the validity of the effective theory in the future vacuum, a natural holographic criterion, automatically enforces the Trans-Planckian Censorship Conjecture (TCC) for classical cosmological solutions with positive potentials. Taken together, these constraints exclude the leading proposals to realize scale-separated AdS vacua and metastable de Sitter vacua in the string theory landscape such as DGKT and KKLT.
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Astrophysics of Galaxies

Trading oxygen for iron II. Oxygen- versus iron-dependent cosmic star formation history

Martyna Chruślińska, Mirko Curti, Ruediger Pakmor et al. (+4 more)

Due to their different nucleosynthetic origin, a stellar population produces oxygen (O) and iron (Fe) on different timescales and their relative abundance can deviate strongly from solar. Galaxy formation models should treat these elements separately, as they play a distinct role in shaping physical phenomena. For example, oxygen mainly sets the gas cooling rate, while the iron abundance sets stellar atmosphere opacities impacting stellar evolution, spectra and feedback. Observations of star-forming galaxies usually only constrain gas-phase oxygen abundance, vastly limiting our capabilities of separating the cosmic evolution of oxygen and iron. Here, we present an observationally-motivated framework to scale the cosmic evolution of O and Fe abundances. We apply the relation between the alpha-enhancement and galaxies' specific star formation rate ([O/Fe]-sSFR; Chruslinska et al. 2024) to derive the Fe and O-dependent cosmic star formation history (cSFH). We find that star formation with near-solar O/Fe is rare: at least 70% of the integrated cosmic stellar mass forms at non-solar O/Fe. The cosmic average metallicity is generally lower in [Fe/H] than in [O/H] (by up to a factor 3), with the offset increasing from redshifts z=0 to z~3 and then approaching the core-collapse O/Fe ratio. We validate our results against samples that probe the Fe-dependent cSFH in different regimes such as absorption-derived <[Fe/H]> from long gamma-ray bursts. Our results impact the interpretations of stellar and galaxy spectra and the predicted rates of transients, especially those linked to metal-poor progenitors (e.g., black hole mergers).
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All authors Martyna Chruślińska, Mirko Curti, Ruediger Pakmor, Annalisa De Cia, Jorryt Matthee, Aniket Bhagwat, Stephanie Monty

High Energy Astrophysical Phenomena

Iron Nuclei in Ultra-High Energy Cosmic Rays Near the Earth

A. Uryson

The propagation of cosmic iron nuclei with energies above 10^19 eV from their sources to the Galaxy is discussed by assuming that cosmic rays at ultra-high energies are of extragalactic origin. In extragalactic space, cosmic nuclei interact with background emissions and inevitably fragment. An analysis is performed of the fraction of iron nuclei reaching the Earth and how its energy depends on the distance from cosmic ray sources. It is found that energies of iron nuclei can be used to determine restriction on the distances from their sources
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Instrumentation and Methods for Astrophysics

A Unified Analytic Framework for Microlensing Caustics: Geode Solutions and Hyper–Catalan Signatures

Gleb Berloff and Natalia G. Berloff

We give a preparation-invariant analytic description of image formation near microlensing caustics. After a local Weierstrass preparation at any multiple image (order $d\ge2$), the lens mapping reduces to a single geode variable $m$ satisfying $m=U\,\varphi(m)$, where $U$ is a prepared source coordinate and $\varphi$ is an image-side kernel. The coefficients of $m(U)$ obey closed Hyper-Catalan (HC) recurrences, allowing termwise derivatives and truncation control from the characteristic system. We also use the same form for a short HC predictor-corrector: evaluate the series within its certified radius and apply a brief Newton polish near the boundary. We define an HC signature (first nonzero kernel coefficients) and an HC spectrum (branch points and analyticity radius $\rho_U$), which quantify sparsity, stiffness, and safe evaluation domains. The construction covers folds and cusps of any global degree. On a binary fold and cusp, an artificial decic with a resonant unit, and two triple-lens cusps of a challenging geometry, HC seeds plus a few Newton steps recover the exact images to machine precision within the certified domain and maintain continuity under continuation. The resulting single-series templates (with $(\mathrm{Sig}_R,\rho_U)$ metadata) are ready for photometric and astrometric modeling.
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Cosmology and Nongalactic Astrophysics

The Atacama Cosmology Telescope: Cross-correlation of kSZ and continuity equation velocity reconstruction with photometric DESI LRGs

Fiona McCarthy, Boryana Hadzhiyska, J. Richard Bond et al. (+12 more)

Over the last year, kinematic Sunyaev–Zel'dovich (kSZ) velocity reconstruction – the measurement of the large-scale velocity field using the anisotropic statistics of the small-scale kSZ-galaxy overdensity correlation – has emerged as a statistically significant probe of the large-scale Universe. In this work, we perform a 2-dimensional tomographic reconstruction using ACT DR6 CMB data and DESI legacy luminous red galaxies (LRGs). We measure the cross-correlation of the kSZ-reconstructed velocity $v^{\mathrm{kSZ}}$ with the velocity inferred from the continuity equation applied to the DESI LRGs $v^{\mathrm{cont}}$ at the $\sim 10 \sigma$ level, detecting the signal with an amplitude with respect to our theory of $b_v = 0.339\pm 0.034$. We fit a scale-dependent galaxy bias model to our measurement in order to constrain local primordial non-Gaussianity $f_{\mathrm{NL}}^{\mathrm{loc}}$, finding {$f_{\mathrm{NL}}^{\mathrm{loc}}=-180^{+61}_{-86}$} at 67% confidence, with $f_{\mathrm{NL}}^{\mathrm{loc}}$ consistent with zero at 95% confidence. We also measure an auto spectrum at $2.1\sigma$ significance which provides a constraint on $b_v$ of $b_v=0.26_{-0.05}^{+0.11}$, which is consistent with the measurement from the cross spectrum. Our combined measurement is $b_v=0.33\pm0.03$, an $11\sigma$ measurement. We find a good fit of our model to the data in all cases. Finally, we use different ACT frequency combinations to explore foreground contamination, finding no evidence for foreground contamination in our velocity cross correlation. We compare to a similar measurement where $v^{\mathrm{kSZ}}$ is directly cross correlated with the large-scale galaxy field, and find signs of foreground contamination which is contained in the equal-redshift spectra.
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All authors Fiona McCarthy, Boryana Hadzhiyska, J. Richard Bond, William R. Coulton, Jo Dunkley, Carmen Embil Villagra, Matthew C. Johnson, Kavilan Moodley, Toshiya Namikawa, Bernardita Ried Guachalla, Blake D. Sherwin, Cristóbal Sifón, Alexander van Engelen, Eve M. Vavagiakis, Edward J. Wollack

High Energy Astrophysical Phenomena

The Relationship Between Emission Line and Continuum Luminosity and the Baldwin Effect in Blazars. I. The Case of the Mg II {\lambda}2798 Å Emission Line

Víctor M. Patiño-Álvarez, Jonhatan U. Guerrero-González, Vahram Chavushyan et al. (+3 more)

Aims. This study investigates the relationship between the Mg II {\lambda}2798 Å emission line and the 3000 Å continuum luminosity, as well as the Baldwin Effect, in a sample of 40,685 radio-quiet (RQ) quasars and 441 Flat Spectrum Radio Quasars (FSRQs). Methods. We perform a comprehensive re-evaluation of the Mg II-3000 Å correlation, explicitly accounting for dispersion introduced by AGN variability. After excluding >3000 radio-loud sources, we employ a binning technique to mitigate variability effects, yielding a refined empirical relation. We also further examine the Non-Thermal Dominance (NTD) parameter, to investigate the dominant source of the continuum. Results. Our analysis reveals statistically significant differences in the slopes of the line-continuum luminosity relation between RQ quasars and FSRQs, with a parallel discrepancy in the Baldwin Effect. These findings imply either (1) intrinsic differences in the accretion disk spectra of RQ AGNs and FSRQs or (2) jet-induced continuum emission in FSRQs contributing to Broad Line Region (BLR) ionization. We also found that a substantial fraction of both RQ quasars (43.8%) and blazars (55.5%) exhibit NTD < 1. For blazars, this suggests that the accretion disk alone cannot fully explain BLR ionization; while we interpret NTD < 1 in radio-quiet quasars as a signature of several physical mechanisms: anomalies in the BLR structure (such as outflow or inflows), time lags between continuum and line variations, and the suppression of the UV continuum by a strong corona that diverts accretion power. Finally, we demonstrate that the Baldwin Effect emerges naturally from the line-continuum luminosity relationship, requiring no additional physical mechanism to explain its origin
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All authors Víctor M. Patiño-Álvarez, Jonhatan U. Guerrero-González, Vahram Chavushyan, Douglas E. Monjardin-Ward, Tigran G. Arshakian, Irene Cruz-González

Cosmology and Nongalactic Astrophysics

Impact of cosmic expansion on gravitational wave spectra from strongly supercooled first-order phase transitions

Marek Lewicki and Ville Vaskonen

We compute the gravitational wave spectra from strongly supercooled first-order phase transitions, explicitly incorporating the evolution of the background metric across the transition from thermal inflation to radiation domination. We find that the spectral shape remains largely unchanged apart from a causality-induced super-horizon tail. However, in contrast to standard expectations, for slow transitions we show that the peak amplitude and frequency exhibit a weaker dependence on the transition rate $\beta$ than the usual scaling of $\propto \beta^{-2}$ and $\propto\beta$, respectively.
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Solar and Stellar Astrophysics

The JWST weather report from the nearest brown dwarfs III: Heterogeneous clouds and Thermochemical instabilities as possible drivers of WISE 1049AB's spectroscopic variability

Natalia Oliveros-Gomez, Elena Manjavacas, Theodora Karalidi et al. (+17 more)

We present a new analysis of the spectroscopic variability of WISE~J104915.57$-$531906.1AB (WISE~1049AB, L7.5+T0.5), observed using the NIRSpec instrument onboard the James Webb Space Telescope (GO 2965 - PI: Biller). We explored the variability of the dominant molecular bands present in their 0.6–5.3~$\mu$m spectra (H$_2$O, CH$_4$, CO), finding that the B component exhibits a higher maximum deviation than the A component in all the wavelength ranges tested. The light curves reveal wavelength-(atmospheric depth) and possibly chemistry-dependent variability. In particular, for the A component, the variability in the light curves at the wavelengths traced by the CH$_4$ and CO molecular absorption features is higher than that of H$_2$O, even when both trace similar pressure levels. We concluded that clouds alone are unlikely to explain the increased variability of CO and CH$_4$ with respect to H$_2$O, suggesting that an additional physical mechanism is needed to explain the observed variability. This mechanism is probably due to thermochemical instabilities. Finally, we provide a visual representation of the 3D atmospheric map reconstructed for both components using the molecular band contributions at different pressure levels and the fit of planetary-scale waves.
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All authors Natalia Oliveros-Gomez, Elena Manjavacas, Theodora Karalidi, Myrla Phillippe, Beatriz Campos Estrada, Beth Biller, Johanna M. Vos, Jacqueline Faherty, Xueqing Chen, Trent J. Dupuy, Thomas Henning, Allison M. McCarthy, Philip S. Muirhead, Elspeth K. H. Lee, Pascal Tremblin, Jasmine Ramirez, Genaro Suarez, Ben J. Sutlieff, Xianyu Tan, Nicolas Crouzet

High Energy Astrophysical Phenomena · Cross-listed from nucl-th

Relativistic mean-field model with density- and isospin-density-dependent couplings

Gabriel Frohaug, Konstantin Maslov, Veronica Dexheimer et al. (+4 more)

We present a new hadronic EoS with hyperons built within the relativistic mean-field (RMF) formalism with baryon-density- and isospin-density-dependent couplings. Motivated by microscopic calculations showing density- and isospin-asymmetry-dependence of self-energies, we implement a new form for the baryon-meson couplings. The parameters for the couplings are constrained by a Bayesian analysis, which anchors the model to nuclear saturation properties, chiral effective field theory ($\chi$EFT) predictions for pure neutron matter, heavy-ion collision data, and HALQCD-based hyperon potential calculations at 3-momentum $|\mathbf{k}|=0$ in both isospin-symmetric and pure neutron matter. The resulting EoS satisfies neutron star mass-radius constraints from NICER and GW170817, providing another way to address the hyperon puzzle. The low-density part of the EoS is described via nuclear statistical equilibrium with modern mass tables (AME20/FRDM12, 8244 nuclei), providing a novel and complete general-purpose EoS for astrophysical simulations.
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All authors Gabriel Frohaug, Konstantin Maslov, Veronica Dexheimer, Joaquin Grefa, Johannes Jahan, Claudia Ratti, Tulio E. Restrepo

Instrumentation and Methods for Astrophysics

The data processing system of the POEMMA-Balloon with Radio mission

Valentina Scotti, Antonio Anastasio, Alfonso Boiano et al. (+7 more)

The POEMMA-Balloon with Radio (PBR) mission incorporates an advanced data processing system (DP) to enable the detection and characterization of ultra-high-energy cosmic rays and astrophysical neutrinos. The data acquisition (DAQ) system integrates inputs from the Cherenkov Camera, the Fluorescence Camera, the Radio Instrument and the X-Gamma detectors, ensuring synchronized event detection. Built upon the heritage of the EUSO-SPB2 DAQ architecture, the system has been adapted to support both the hybrid focal surface and radio instrumentation. The DP features two redundant CPUs, differential GPS receivers, and environmental monitoring capabilities, including temperature, humidity, and gyroscope-based orientation tracking. A central clock board synchronizes data collection across all instruments, ensuring precise event reconstruction. The main trigger and clock board manages trigger signals from different detectors, supporting both joint and independent data acquisition modes. These advancements enhance the mission's contribution to multi-messenger astrophysics and provide valuable insights for future space-based observatories. In this paper, we describe the system's main components and the design developed for this new mission.
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All authors Valentina Scotti, Antonio Anastasio, Alfonso Boiano, Francesco Cafagna, Vincenzo Masone, Marco Mese, Giuseppe Osteria, Giuseppe Passeggio, Francesco Perfetto, Haroon Akhtar Qureshi

Instrumentation and Methods for Astrophysics

The Cherenkov Camera for the PBR mission

Valentina Scotti, Antonio Anastasio, Mario Bertaina et al. (+11 more)

The POEMMA-Balloon with Radio (PBR) mission is a NASA super-pressure balloon experiment designed to advance the detection of ultra-high-energy cosmic rays, high-altitude horizontal air showers, and astrophysical neutrinos. A key instrument of PBR is the Cherenkov Camera (CC), which utilizes a 2048-pixel SiPM camera to detect the optical Cherenkov emission from cosmic-ray-induced air showers and search for upward-going signals indicative of neutrinos. The CC operates in the 320-900 nm spectral range with a 10 ns integration time, leveraging a bi-focal optical design to enhance detection efficiency. The CC enables precise reconstruction of shower trajectories and provides valuable data on cosmic rays' composition and energy distribution. PBR's sub-orbital altitude is particularly advantageous for these measurements, offering a unique vantage point that bridges the observational gap between ground-based and space-based instruments. Additionally, the CC will play a critical role in neutrino searches, detecting tau-lepton decay showers from Earth-skimming neutrinos associated with astrophysical transients. By integrating the CC with fluorescence and radio detection systems, PBR will pioneer a multi-messenger approach to high-energy cosmic phenomena, refining observational techniques for future space-based missions. This contribution will describe the current status of the development of the CC as well as its expected performance.
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All authors Valentina Scotti, Antonio Anastasio, Mario Bertaina, Alfonso Boiano, Rossella Caruso, Cristian De Santis, Vincenzo Masone, Marco Mese, Giuseppe Osteria, Beatrice Panico, Giuseppe Passeggio, Francesco Perfetto, Haroon Akhtar Qureshi, Ester Ricci

Cosmology and Nongalactic Astrophysics

Reporting a Deficit of Intrinsic NV Absorbers in Core-dominated, Radio-loud Quasars

Chris Culliton, Amber Roberts, Bryan DeMarcy et al. (+5 more)

We searched the Hubble Space Telescope Cosmic Origins Spectrograph archive for ultraviolet spectra of 428 AGN to identify intrinsic NV absorption systems. We filtered out Type 2 AGN, blazars, and spectra that do not cover at least part of the velocity window from 5000 km/s blueward to 5000 km/s redward (hereafter, the “associated” region) of the NV emission line. This yielded 175 Type 1 quasars, 34 radio-loud, 133 radio-quiet, and eight unconstrained. Our survey uncovered 77 associated NV systems in the spectra of 48 of these low-redshift quasars. We consider the incidence of intrinsic absorbers as a function of quasar properties (optical, radio and X-ray). We find a statistically significant dearth of intrinsic NV systems in the spectra of the 34 radio-loud quasars (6%), compared to 29% of the 133 radio-quiet quasars containing at least one intrinsic system. Assuming intrinsic systems are equally likely to occur in radio-loud and radio-quiet quasars and the orientations of the two subsamples are comparable, there is a 0.1% probability of such a deficit occurring by chance in the radio-loud population. We propose that this deficit of systems is caused by orientation effects. FIRST radio images are available for 14 of the 33 radio-loud quasars. These show that only three of the 14 radio-loud quasars have lobe-dominated morphologies, whereas 11 of the 14 radio-loud quasars have compact radio morphologies, implying that these quasars are face on, and suggesting that clouds that produce NV absorption are rarely found along the polar axis.
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All authors Chris Culliton, Amber Roberts, Bryan DeMarcy, Sowgat Muzahid, Rajib Ganguly, Jane Charlton, Michael Eracleous, Toru Misawa

Earth and Planetary Astrophysics

Unified Kraft Break at ~6500 K: A Newly Identified Single-Star Obliquity Transition Matches the Classical Rotation Break

Xian-Yu Wang, Songhu Wang and J. M. Joel Ong

The stellar obliquity transition, defined by a $\textit{T}_{\rm eff}$ cut separating aligned from misaligned hot Jupiter systems, has long been assumed to coincide with the rotational Kraft break. Yet the commonly quoted obliquity transition (6100 or 6250 K) sits a few hundred kelvin cooler than the rotational break (~6500 K), posing a fundamental inconsistency. We show this offset arises primarily from binaries/multiple-star systems, which drive the cooler stellar obliquity transition ($6105^{+123}_{-133}$ K), although the underlying cause remains ambiguous. After removing binaries and higher-order multiples, the single-star stellar obliquity transition shifts upward to $6447^{+85}_{-119}$ K, in excellent agreement with the single-star rotation break ($6510^{+97}_{-127}$ K). This revision has two immediate consequences for understanding the origin and evolution of spin-orbit misalignment. First, the upward shift reclassifies some hosts previously labeled `hot' into the cooler regime; consequently, there are very few RM measurements of non-hot-Jupiter planets around genuinely hot stars ($T_{\rm eff}\gtrsim6500\,\mathrm{K}$), and previously reported alignment trends for these classes of systems (e.g., warm Jupiters and compact multi-planet systems) lose the power to discriminate the central question: are large misalignments unique to hot-Jupiter-like planets that can be delivered by high-$e$ migration, or are hot stars intrinsically more misaligned across architectures? Second, a single-star stellar obliquity transition near $6500\,\mathrm{K}$, coincident with the rotational break, favors tidal dissipation in outer convective envelopes; as these envelopes thin with increasing $T_{\rm eff}$, inertial-wave damping and magnetic braking weaken in tandem.
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High Energy Astrophysical Phenomena

Catching the 2021 {\gamma}-ray flare in the blazar TXS 2013+370

Giorgos Michailidis, Efthalia Traianou, Nicola Marchili et al. (+8 more)

The $\gamma$-ray-loud blazar TXS 2013+370, a powerful multiwavelength emitter at $z = 0.859$, underwent an exceptional GeV outburst in late 2020-early 2021. In this work, we present full-polarization VLBI imaging at 22, 43, and 86 GHz together with contemporaneous single-dish monitoring (radio and $\gamma$-rays) to localize the high-energy dissipation site and probe the inner-jet structure and magnetic field topology. The images revealed a compact near-core knot at $r \simeq 40$-$60~\mu\mathrm{as}$ contemporaneously with the GeV flare and a flat, core-dominated spectrum ($\alpha \gtrsim -0.5$). The core has strong linear polarization and exhibits a $\sim 50^{\circ}$ EVPA rotation at 86 GHz; pixel-based and integrated fits yield a high, uniform rotation measure, ${\rm RM} = (7.8 \pm 0.2) \times 10^{4}~{\rm rad~m^{-2}}$, consistent with an external Faraday screen. Cross-correlation of Fermi-LAT and 15 GHz data shows a significant peak with the $\gamma$ rays leading by $\Delta t = (102 \pm 12)\,\mathrm{d}$; adopting $\beta_{\rm app} = 4.2 \pm 0.5$ and $\theta = 4.1^{\circ} \pm 0.2^{\circ}$ implies a de-projected separation $\Delta r_{\gamma-15} = (2.71 \pm 0.47)\,\mathrm{pc}$ and locates the GeV emission between the jet apex and $\sim 0.42$ pc ($1\sigma$ range) downstream. Our results do not uniquely pinpoint the emission site; rather, they support two valid scenarios. The $\gamma$-ray production may occur within the BLR ($\sim 0.07$pc), where external-Compton scattering of optical/UV photons produces the $\gamma$ rays, or beyond the BLR, reaching $\sim 0.42$ pc ($1\sigma$) within the inner parsecs, where external-Compton scattering of dusty-torus infrared photons dominates. Both scenarios are compatible within the allowed range of emission distances, while opacity-driven core shifts modulate the observed radio-$\gamma$ delay without requiring large relocations of the dissipation zone.
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All authors Giorgos Michailidis, Efthalia Traianou, Nicola Marchili, Giorgos Filippos Paraschos, Thomas P. Krichbaum, Uwe Bach, P. A. Vergara de la Parra, Dong-Jin Kim, Victor Manuel Patiño-Álvarez, Matthias Kadler, Mark Gurwell

Solar and Stellar Astrophysics · Cross-listed from physics.space-ph

Turbulence in the terrestrial magnetosheath: space-time correlation using the Magnetospheric Multiscale mission

Francesco Pecora, William H. Matthaeus, Antonella Greco et al. (+4 more)

Spatiotemporal correlation of magnetic field fluctuations is investigated using the Magnetospheric Multiscale mission in the terrestrial magnetosheath. The first observation of the turbulence propagator in space emerges through analysis of more than a thousand intervals. Results show clear features of spatial and spectral anisotropy, leading to a distinct behavior of relaxation times in the directions parallel and perpendicular to the mean magnetic field. Full space-time investigation of the Taylor hypothesis reveals a scale-dependent anisotropy of magnetosheath fluctuations that can be compared to the effect of flow propagation on spacecraft frame time decorrelation rates as well as with Eulerian estimates. The turbulence propagator reveals that the amplitudes of the perpendicular modes decorrelate according to sweeping or Alfvénic propagation mechanisms. The decorrelation time of parallel modes instead does not depend on the parallel wavenumber, which could be due to resonant interactions. Through direct observation, this study provides unprecedented insight into the space-time structure of turbulent space plasmas, while giving critical constraints for theoretical and numerical models.
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All authors Francesco Pecora, William H. Matthaeus, Antonella Greco, Pablo Dmitruk, Yan Yang, Vincenzo Carbone, Sergio Servidio

High Energy Astrophysical Phenomena

Excess of diffuse gamma-ray emission detected from the galaxy cluster Abell 119 from 14-year Fermi-LAT Data

Gajanan D Harale and Surajit Paul

Galaxy clusters are among the most massive gravitationally bound systems in the Universe and are considered major reservoirs of high-energy cosmic rays, yet no conclusive $\gamma$-ray detection from them has been achieved. This non-detection may stem from limited sensitivity and source localization of current $\gamma$-ray instruments, as well as strong interactions of $\gamma$-rays with intervening material that restrict detectable signals to only a few nearby and dynamically active clusters. Motivated by these constraints, we selected a sample of nearby ($z<0.05$) merging clusters and analyzed 14 years of Fermi-LAT data. In this work, we present a detailed study of Abell 119 (A119), a merging cluster with significant X-ray luminosity and complex dynamics. Using Fermipy and Fermi Science Tools, we modeled all potential $\gamma$-ray sources and confirmed the 4FGL point sources 4FGL J0059.3$-$0152, 4FGL J0101.0$-$0059, and 4FGL J0059.2+0006 with significant TS values.s. It further reveals, a $\sim4\sigma$ excess of diffuse $\gamma$-ray emission offset by $\sim0.25^\circ$ from the cluster center, plausibly associated with the cluster halo. An extended model provides the best fit, yielding luminosity bounds of $\sim 12.21^{+2.74}_{-3.95}\times10^{42}\,\mathrm{erg\,s^{-1}}$ and a particle spectral index of $\sim2.25^{+0.38}_{-0.13}$, consistent with earlier expectations for cluster-scale non-thermal emission. These results suggest a hadronic origin for the detected signal. Although the $\sim4\sigma$ excess is compelling, uncertainties in localization and instrumental limitations prevent a definitive detection. Nonetheless, the results highlight the potential for deeper cluster studies, and the estimated neutrino flux $E^{2}\phi_{\nu}\approx3\times10^{-10}\,\mathrm{GeV\,cm^{-2}\,s^{-1}\,sr^{-1}}$ motivates future observations with upcoming neutrino telescopes.
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Solar and Stellar Astrophysics

Quadruple system HD 135160 in a unique 2+2 configuration

Michal Zummer, Petr Harmanec, Brad Barlow et al. (+2 more)

Analysing a large body of observational data, we found that HD 135160 is a quadruple 2+2 system, composed of a massive ellipsoidal binary ('heartbeat' star) with components Aa and Ab in an eccentric 8.234 d orbit and an eclipsing binary (with components Ba and Bb), with a 5.853 d period and partial eclipses that have already been reported from the space photometry secured by the Transiting Exoplanet Survey Satellite (TESS). Our systematic echelle spectroscopy, secured since September 2021, led to the discovery that the optical spectra are dominated by spectral lines of three early-type stars, two moving around each other on a 8.234 d orbit of a high eccentricity, which causes periodic brightenings near the periastron passage, and the third one (component Ba) being the brighter component of the 5.853 d binary. Both pairs are physically bounded and revolve around each other with a period somewhere between 1600 and 2200 days (4.4 to 6 years). The object exhibits small cyclic light variations of a variable amplitude and characteristic time scale of 0.071 d (14.14 c d-1), seen throughout the whole orbit. The nature of these tiny changes deserves further investigation. It also seems that the earlier classification of the object as a Be star is unfounded.
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All authors Michal Zummer, Petr Harmanec, Brad Barlow, Mark Blackford, Jana Švrčková

High Energy Astrophysical Phenomena

Is There New Physics Beyond 30 TeV in the BOAT?

Filip Rescic, Luis Recabarren Vergara, Michele Doro et al. (+1 more)

We show that the GRB 221009A spectrum detected by LHAASO can be used to probe effects of quadratic subluminal Lorentz Invariance Violation (LIV) through the enhancement of the observed flux at the highest energies. In particular, we argue that excesses in the GRB 221009A data currently classified as non-detections at energies $E \gtrsim 30$ TeV warrant further investigation, as they may indicate a recovery of the intrinsic source spectrum consistent with the LIV-induced suppression of $\gamma\gamma \to e^-e^+$ interactions within the quadratic subluminal scenario. This would increase the accessible parameter space of the energy scale of new physics.
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All authors Filip Rescic, Luis Recabarren Vergara, Michele Doro, Tomislav Terzić

Astrophysics of Galaxies

The VVVX quest for satellites around the Circinus galaxy

L. D. Baravalle, A. L. O'Mill, M. V. Alonso et al. (+10 more)

The Circinus galaxy is the nearest type-2 Seyfert galaxy, which is at a distance of 4.2 Mpc. Its environment is challenging to explore because it is located at low Galactic latitudes, behind the Galactic disc. The long-term goal is to characterise the Circinus galaxy halo and determine the presence of dwarf satellites using near-infrared data. We selected 1,542 galaxies from the VVV NIRGC within a 2-degree radius around Circinus, representing 2/3 of the virial radius. Structural parameters such as half-light radii and colours were used, and correlations were examined. A neural network was trained with 486 galaxies with known spectroscopic redshifts to estimate photometric redshifts for all galaxies. Potential satellites were defined based on half-light radii compatible with the typical sizes of dwarf satellites, and combined with photometric redshifts. The galaxy properties are reliably characterised down to $K_{s}$ $\sim$ 15.5 mag, which represents about 90% completeness of detections. At the distance of Circinus, this limiting magnitude corresponds to $K_{s}$ absolute magnitude of $-12.6$ mag, which allows us to find dwarf galaxies. There are 20 galaxies with half-light radii larger than 2.45 arcsec, only 8 have photometric redshifts below 0.04. None of these galaxies is close to Circinus, which has a redshift of 0.0015. The ANNz model exhibited a high degree of accuracy in the range $0.001 < z_{phot} < 0.023$. The presence of dwarf satellites could not be confirmed with the available data in the studied region. The apparent lack of satellites may be genuine, possibly related to AGN feedback effects. This work demonstrates the effectiveness of combining near-infrared data and machine learning techniques to estimate photometric redshifts at low Galactic latitudes, providing useful information for future spectroscopic follow-up campaigns.
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All authors L. D. Baravalle, A. L. O'Mill, M. V. Alonso, C. Obasi, D. Minniti, M. Gómez, C. Villalon, J. Nilo-Castellón, C. Valotto, M. Soto, I. V. Daza Perilla, M. A. Sgró, J. G. Fernández-Trincado

Solar and Stellar Astrophysics

Using Light Curve Derivatives to Estimate the Fill-out Factor of Overcontact Binaries

Shinjirou Kouzuma

We propose a simple method for estimating the fill-out factor of overcontact binary systems using the derivatives of light curves. We synthesized 74,431 sample light curves, covering the typical parameter space of overcontact binaries. On the basis of a recent study that proposed a new classification scheme using light curve derivatives up to the fourth order, the sample light curves were classified. Among the classified types, for systems exhibiting high mass ratios and high inclinations (i.e., SPf type), we found that the fill-out factor has a strong correlation with the time interval between two local extrema in the third derivatives of their light curves. An empirical formula to estimate the fill-out factor was derived using regression analysis for the identified correlation. Application to real overcontact binary data demonstrated that the proposed method is practical for obtaining reliable estimates of the fill-out factor and its associated uncertainties.
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Solar and Stellar Astrophysics · Cross-listed from physics.atom-ph

Wavelengths and Energy Levels of Neutral Manganese (Mn I) Determined Using High-Resolution Fourier Transform and Grating Spectroscopy

Christian P. Clear, Gillian Nave, Richard Blackwell-Whitehead et al. (+3 more)

An extensive analysis of the spectrum of neutral manganese has been performed using spectra of manganese-neon and manganese-argon hollow cathode discharges measured using high resolution Fourier transform (FT) and grating spectroscopy over the range 151 - 5112 nm (1956 - 65876 cm-1). Wavelengths for 10426 spectral lines were extracted from the FT spectra, with uncertainties at least an order-of-magnitude lower than previous measurements. Wavelengths for 13397 lines from new grating spectra were determined for spectral regions beyond the FT spectra range or to provide wavelengths for weak transitions not observed in FT spectra. To aid in level identification, selected, previously published grating lines were included in the energy level optimisation, but no levels in this work relied solely on previously published wavelengths. In total, 24237 lines were included in the final spectral linelist, and these were used to identify 2186 Mn I transitions. These classified spectral lines were then used to optimise the values of 384 previously published energy levels of Mn I, with typical uncertainties of a few 10-3 cm-1, again typically an order-of-magnitude improvement in accuracy. Our study then expanded the known energy level structure of Mn I through the establishment of 18 new energy levels, reported here for the first time. In total, 2187 lines and 402 energy levels of Mn I have been determined as a result of our work, marking a substantial advance in the precision of Mn I atomic data which will enable far more accurate analyses of Mn I lines in astrophysical spectra. Please note: The final wavelength and energy level datasets are withheld from this pre-print to ensure that only the peer-reviewed, definitive versions are released. This approach prevents the propagation of duplicate or inconsistent data across widely used atomic databases and modelling frameworks.
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All authors Christian P. Clear, Gillian Nave, Richard Blackwell-Whitehead, Maria Teresa Belmonte, Stephen Ingram, Juliet C. Pickering

Solar and Stellar Astrophysics

Identification of periodic density structures in Solar Orbiter data: Radial evolution

C. Katsavrias, S. Di Matteo, L. Kepko et al. (+2 more)

The quasi-Periodic density structures (PDSs) are quasiperiodic variations of solar wind density ranging from a few minutes to a few hours. They are trains of advected density structures with radial length scales LR in the 100-10,000 Mm range, thus belonging to the class of solar wind mesoscale structures. Even though PDS at L1 have been extensively studied both through statistical and event analysis, their investigation at distances closer to the Sun is limited. This study performs a statistical investigation of PDS at various distances from the Sun between 0.3 and 1 AU by exploiting Solar Orbiter data. We compiled and made publicly available an extensive list of PDSs following a well-established methodology that combines the Multitaper method as well as wavelet analysis to reveal the distribution of PDS radial length scales and how they vary with respect to the radial distance. Our results indicate that PDS advected with the ambient slow solar wind are expanded at a rate of approximately 10%, while PDS detected during fast solar wind segments show compression at a similar rate. These are consistent with the scenario in which PDSs are formed at the Sun by processes involving magnetic reconnection and interchange reconnection in the solar corona.
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All authors C. Katsavrias, S. Di Matteo, L. Kepko, N. Viall, A. Walsh

Instrumentation and Methods for Astrophysics

Efficient Exoplanet Imaging Simulations of the Habitable Worlds Observatory

Jamila Taaki, Farzad Kamalabadi, Athol Kemball et al. (+2 more)

Direct imaging simulations of starshades and other proposed mission concepts are needed to characterize planet detection performance and inform mission design trades. In order to assess the complementary role of a 60 m starshade for the Habitable Worlds Observatory (HWO), we develop the optical model of a starshade and simulate solar system imaging at 0 degrees and 60 degrees inclinations. The optical core throughput of a direct-imaging system is a key metric that governs exposure time and the potential exoplanetary yield of a mission. We use our optical model to evaluate core throughput, incorporating 6 m segmented and obscured telescope apertures, over the visible to near-infrared wavelength band (500-1000 nm). Accurate diffractive optical simulations of this form require many large Fourier transforms, with prohibitive run-times, as both the starshade mask and telescope aperture require fine-scale spatial sampling. We introduce a Fourier sampling technique, the Bluestein Fast Fourier Transform (BFFT), to efficiently simulate diffractive optics and enable high-fidelity simulations of core throughput. By characterizing sampling requirements and comparing BFFT's computational complexity to standard Fourier methods (for example, DFT and FFT), we demonstrate its efficiency in our optical pipeline. These methods are implemented in PyStarshade (Taaki 2025), an open-source Python package offering flexible diffraction tools and imaging simulations for starshades. Our results show the HWO starshade used with a segmented off-axis telescope aperture achieves an optimal core throughput measured within a photometric aperture of radius 0.7 lambda/D of 68 percent. With an additionally obscured aperture, a 66 percent core throughput is achieved.
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All authors Jamila Taaki, Farzad Kamalabadi, Athol Kemball, Lia Corrales, Alfred O. Hero III

High Energy Astrophysical Phenomena

Probing the disk-jet coupling in M87

Ainara Saiz-Pérez, Christian M. Fromm, Yosuke Mizuno et al. (+3 more)

Context. Recent GMVA observations of M 87 at event horizon scales revealed a ring-like structure which is 50% larger at 86 GHz than the ring observed by the Event Horizon Telescope at 230 GHz. Aims. In this paper, we study a possible origin of the increased ring size at 86 GHz. We specifically aim to study the role the nonthermal electron population plays in the observed event horizon scales. Methods. We carry out 3D general relativistic magnetohydrodynamic simulations followed by radiative transfer calculations. We incorporate into the latter synchrotron emission from both thermal and nonthermal electrons. To better compare our results to observations, we generate synthetic interferometric data adjusted to the properties of the observing arrays. We fit geometrical models to this data in Fourier space through Bayesian analysis to monitor the variable ring size and width over the simulated time span of years. Results. We find that the 86 GHz ring is always larger than the 230 GHz ring, which can be explained by the increased synchrotron self-absorption at 86 GHz and the mixed emission from both the accretion disk and the jet footpoints, as well as flux arcs ejected from a magnetized disk. We find agreement with the observations, particularly within the error range of the observational value of M/D for M 87. Conclusions. We show that state-of-the art 3D GRMHD simulations combined with thermal and nonthermal emitting particles can explain the observed frequency-dependent ring size in M 87. Importantly we found that MAD events triggered in the accretion disk can significantly increase the lower frequency ring sizes.
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All authors Ainara Saiz-Pérez, Christian M. Fromm, Yosuke Mizuno, Matthias Kadler, Karl Mannheim, Ziri Younsi

Instrumentation and Methods for Astrophysics

LCS: A Learnlet-Based Sparse Framework for Blind Source Separation

V. Bonjean, A. Gkogkou, J.L. Starck et al. (+1 more)

Blind source separation (BSS) plays a pivotal role in modern astrophysics by enabling the extraction of scientifically meaningful signals from multi-frequency observations. Traditional BSS methods, such as those relying on fixed wavelet dictionaries, enforce sparsity during component separation, but may fall short when faced with the inherent complexity of real astrophysical signals. In this work, we introduce the Learnlet Component Separator (LCS), a novel BSS framework that bridges classical sparsity-based techniques with modern deep learning. LCS utilizes the Learnlet transform: a structured convolutional neural network designed to serve as a learned, wavelet-like multiscale representation. This hybrid design preserves the interpretability and sparsity, promoting properties of wavelets while gaining the adaptability and expressiveness of learned models. The LCS algorithm integrates this learned sparse representation into an iterative source separation process, enabling effective decomposition of multi-channel observations. While conceptually inspired by sparse BSS methods, LCS introduces a learned representation layer that significantly departs from classical fixed-basis assumptions. We evaluate LCS on both synthetic and real datasets, demonstrating superior separation performance compared to state-of-the-art methods (average gain of about 5 dB on toy model examples). Our results highlight the potential of hybrid approaches that combine signal processing priors with deep learning to address the challenges of next-generation cosmological experiments.
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All authors V. Bonjean, A. Gkogkou, J.L. Starck, P. Tsakalides

Cosmology and Nongalactic Astrophysics

Challenging the $\omega_0\omega_a$CDM parametrization through rational expansions in view of DESI data release

Youri Carloni, Orlando Luongo and Marek Biesiada

In view of the new Dark Energy Spectroscopic Instrument (DESI) 2025 results, we analyze three types of Padé cosmology, based on rational series making use of Padé approximants over the equations of state, namely Padé$^{\omega}$ (0,1) and Padé$^{\omega}$ (1,1), plus a Padé$^{q}$ (0,1), i.e., a rational expansion on the dark energy deceleration parameter, in which where the numerator and denominator orders are incorporated into the above brackets. These scenarios appear alternative dark energy parameterizations with respect to the well-known $\omega_0\omega_a$CDM model, claimed as the most viable model by DESI. Accordingly, we perform Monte Carlo Markov chain (MCMC) analyses with the publicly available CLASS Boltzmann code, including the three Padé cosmology, along with the $\omega_0\omega_a$CDM and $\Lambda$CDM standard pictures. To this end, we combine independent probes from high to low redshifts to obtain reliable constraints on the cosmological parameters of these models and compare them using statistical selection criteria. \emph{Our results show that Padé cosmology is neither statistically excluded nor worse than the $\omega_0\omega_a$CDM parametrization}. On the contrary, the Akaike Information Criterion (AIC) identifies Padé$^{q}$ (0,1) as the best-fit model, with weak evidence against the $\omega_0\omega_a$CDM parameterization, while the Deviance Information Criterion (DIC) provides \emph{strong evidence against the $\omega_0\omega_a$CDM model, favoring Padé (1,1)}. Based on our bounds, we further investigate the evolution of the squared sound speed, revealing that the Padé$^{q}$ (0,1) and Padé$^{\omega}$ (0,1) parameterizations exhibit enhanced stability compared with the other cases here considered and, therefore, describe robust alternatives for the cosmological background.
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Instrumentation and Methods for Astrophysics

Optical gains measurement with a gain scheduling camera: On-sky demonstration with PAPYRUS and perspectives

A. Striffling, C.-T. Héritier, R.J.-L Fétick et al. (+4 more)

Reaching the high angular resolution and contrast level desired for exoplanetary science requires us to equip large telescopes with extreme adaptive optics (XAO) systems to compensate for the effect of the atmospheric turbulence at a very fast rate. This calls for the development of ultra-sensitive wavefront sensors (WFSs), such as Fourier filtering wavefront sensors (FFWFSs), to be operated at low flux, as well as an increase in the XAO loop frame rate. These sensors, which constitute the baseline for current and future XAO systems, exhibit such a high sensitivity at the expense of a non-linear behaviour that must be properly calibrated and compensated for to deliver the required performance. We aim to validate on-sky a recently proposed method that associates the FFWFS with a focal plane detector, the gain scheduling camera (GSC), to estimate in real time the first-order terms of the sensor non-linearities, known as modal optical gains. We implemented a GSC on the adaptive-optics (AO) bench PAPYRUS to be associated with the existing pyramid wavefront sensor (PWFS). We compared experimental results to expected results obtained with a high-fidelity numerical twin of the AO system. We validated experimentally the method both in laboratory and on-sky. We demonstrated the capability of the GSC to accurately estimate the optical gains of the PWFS at 100 Hz, corresponding to the current limit in speed imposed by PAPYRUS hardware, but it could be applied at higher frequencies to enable frame-by-frame optical gains tracking. The presented results exhibit good agreement on the optical gains estimation with respect to numerical simulations reproducing the experimental conditions tested. Our experimental results validate the strategy of coupling a FFWFS with a focal-plane camera to master the non-linearities of the sensor. This demonstrates its attractiveness for future XAO application.
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All authors A. Striffling, C.-T. Héritier, R.J.-L Fétick, O. Fauvarque, J.-F Sauvage, A. Carlotti, B. Neichel T. Fusco

High Energy Astrophysical Phenomena

Advancing Identification method of Gamma-Ray Bursts with Data and Feature Enhancement

Peng Zhang, Bing Li, Ren-Zhou Gui et al. (+12 more)

Gamma-ray bursts (GRBs) are challenging to identify due to their transient nature, complex temporal profiles, and limited observational datasets. We address this with a one-dimensional convolutional neural network integrated with an Adaptive Frequency Feature Enhancement module and physics-informed data augmentation. Our framework generates 100,000 synthetic GRB samples, expanding training data diversity and volume while preserving physical fidelity-especially for low-significance events. The model achieves 97.46% classification accuracy, outperforming all tested variants with conventional enhancement modules, highlighting enhanced domain-specific feature capture. Feature visualization shows model focuses on deep-seated morphological features and confirms the capability of extracting physically meaningful burst characteristics. Dimensionality reduction and clustering reveal GRBs with similar morphologies or progenitor origins cluster in the feature space, linking learned features to physical properties. This perhaps offers a novel diagnostic tool for identifying kilonova- and supernova-associated GRB candidates, establishing criteria to enhance multi-messenger early-warning systems. The framework aids current time-domain surveys, generalizes to other rare transients, and advances automated detection in large-volume observational data.
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All authors Peng Zhang, Bing Li, Ren-Zhou Gui, Shao-Lin Xiong, Yu Wang, Shi-Jie Zheng, Guang-Cheng Xiao, Xiao-Bo Li, Yue Huang, Chen-Wei Wang, Jia-Cong Liu, Yan-Qiu Zhang, Wang-Chen Xue, Chao Zheng, Yue Wang

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Detectability of axion-like dark matter for different time-delay interferometry combinations in space-based gravitational wave detectors

Yong-Yong Liu, Jing-Rui Zhang, Ming-Hui Du et al. (+3 more)

In the space-based gravitational wave detections, the axion-like dark matter would alter the polarization state of the laser link between spacecrafts due to the birefringence effect. However, current designs of space-based laser interferometer are insensitive to variations in the polarization angle. Thus, the additional wave plates are employed to enable the response of the axion-induced birefringence effect. We calculate and compare the sensitivities of different space-based detectors, accounting for three time-delay interferometry combinations, including Monitor, Beacon, and Relay. We find that the Monitor and Beacon combinations have better sensitivity in the high-frequency range, and the optimal sensitivity reaches $g_{a\gamma}\sim 10^{-13}\text{GeV}^{-1}$, while the Sagnac combination is superior in the low-frequency range. We also find that ASTROD-GW can cover the detection range of axion-like dark matter mass down to $10^{-20}\text{eV}$.
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All authors Yong-Yong Liu, Jing-Rui Zhang, Ming-Hui Du, He-Shan Liu, Peng Xu, Yun-Long Zhang