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Physics Astrophysics

astro-ph Watch Astrophysics

Wednesday 3 June

Instrumentation and Methods for Astrophysics

Narrow spectral artifact investigation and mitigation in LIGO data from the fourth LIGO-Virgo-KAGRA observing run

E. Goetz, A. Neunzert, A. M. Knee et al. (+259 more)

We present efforts to identify, characterize, and mitigate narrow spectral artifacts in LIGO detector data during the fourth LIGO-Virgo-KAGRA observing run. Narrow spectral artifacts in gravitational-wave detectors are non-astrophysical noise sources that can degrade searches for narrowband persistent gravitational waves. Identifying and, where possible, mitigating these noise sources is one of the core efforts of the LIGO Detector Characterization group. Key software tools have been updated and new tools deployed for the fourth LIGO-Virgo-KAGRA observing run to facilitate investigations and data monitoring. We discuss these tool upgrades, and present several identified narrowband artifacts that have been successfully investigated and mitigated in LIGO data. Regardless of whether artifacts are mitigated or not, narrowband persistent gravitational-wave searches require information on which frequency bands contain non-astrophysical artifacts. Minimizing the number of bands containing non-astrophysical artifacts is essential to maximize the potential for discovery of a new class of gravitational-wave signals.
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All authors E. Goetz, A. Neunzert, A. M. Knee, A. Calafat, X. Fan, J-R. Mérou, K. A. Pham, T. Starkman, N. Aggarwal, Z. Bhalla, P. Baxi, J. Bayley, Y. Bu, J. B. Carlin, P. Charlton, X. Chen, G. Cheng, T. Cheunchitra, N. Christensen, A. Claveus, C. M. Compton, M. W. Coughlin, F. De Lillo, L. Dunn, S. E. Dwyer, A. Effler, T. A. Ferreira, B. Finkel, P. Goodarzi, A. E. Granados, H. Guo, C. Hsiung, K. Janssens, S. Kandhasamy, K. Kawabe, Y.-M. Kim, T. Kimpson, R. Krismer, M. Lalleman, Y. S. C. Lee, N. K. Y. Low, J. C. Martins, H. Middleton, C.-A. Miritescu, D. Nykamp, J. O'Leary, A. Renzini, K. Riles, A. Romero-Rodríguez, J. R. Sanders, R. M. S. Schofield, D. Singh, D. Singh, R. Slocum, Q. Song, J. Suresh, S. Suyamprakasam, J. D. Tasson, A. Tripathee, A. F. Vargas, A. Wang, K. Wu, J. Yee, J. Yi, Z. Zhang, R. Abbott, I. Abouelfettouh, R. X. Adhikari, A. Ananyeva, S. Appert, S. K. Apple, K. Arai, N. Aritomi, S. M. Aston, M. Ball, S. W. Ballmer, D. Barker, L. Barsotti, B. K. Berger, J. Betzwieser, D. Bhattacharjee, G. Billingsley, S. Biscans, C. D. Blair, N. Bode, E. Bonilla, V. Bossilkov, A. Branch, A. F. Brooks, D. D. Brown, J. Bryant, C. Cahillane, S. R. Callos, H. Cao, E. Capote, F. Clara, J. Collins, G. Connolly, R. Cottingham, D. C. Coyne, R. Crouch, J. Csizmazia, A. Cumming, L. P. Dartez, D. Davis, N. Demos, E. Dohmen, K. L. Dooley, J. C. Driggers, A. Ejlli, T. Etzel, M. Evans, J. Feicht, R. Frey, W. Frischhertz, P. Fritschel, V. V. Frolov, M. Fuentes-Garcia, P. Fulda, M. Fyffe, D. Ganapathy, B. Gateley, T. Gayer, J. A. Giaime, K. D. Giardina, J. Glanzer, R. Goetz, A. W. Goodwin-Jones, S. Gras, C. Gray, D. Griffith, H. Grote, T. Guidry, J. Gurs, E. D. Hall, J. Hanks, J. Hanson, M. C. Heintze, A. F. Helmling-Cornell, N. A. Holland, D. Hoyland, H. Y. Huang, Y. Inoue, A. L. James, A. Jamies, R. Jaume, A. Jennings, W. Jia, D. H. Jones, H. B. Kabagoz, S. Karat, S. Karki, M. Kasprzack, D. Keitel, N. Kijbunchoo, P. J. King, J. S. Kissel, K. Komori, A. Kontos, R. Kumar, K. Kuns, M. Landry, B. Lantz, M. Laxen, K. Lee, M. Lesovsky, F. Llamas Villarreal, M. Lormand, H. A. Loughlin, R. Macas, M. MacInnis, C. N. Makarem, B. M. Mannix, G. L. Mansell, R. M. Martin, K. Mason, F. Matichard, N. Mavalvala, N. Maxwell, G. McCarrol, R. McCarthy, D. E. McClelland, S. McCormick, T. McRae, F. Mera, E. L. Merilh, F. Meylahn, R. Mittleman, D. Moraru, G. Moreno, A. Mullavey, M. Nakano, T. J. N. Nelson, J. Notte, J. Oberling, T. O'Hanlon, R. Oram, C. Osthelder, D. J. Ottaway, H. Overmier, W. Parker, O. Patane, A. Pele, H. Pham, M. Pirello, J. Pullin, V. Quetschke, K. E. Ramirez, K. Ransom, J. Reyes, J. W. Richardson, M. Robinson, J. G. Rollins, C. L. Romel, J. H. Romie, M. P. Ross, B. I. Rotimi, K. Ryan, T. Sadecki, A. Sanchez, E. J. Sanchez, L. E. Sanchez, R. L. Savage, D. Schaetzl, M. G. Schiworski, R. Schnabel, E. Schwartz, D. Sellers, T. Shaffer, R. W. Short, D. Sigg, A. M. Sintes, B. J. J. Slagmolen, C. Soike, S. Soni, V. Srivastava, L. Sun, D. B. Tanner, M. Thomas, P. Thomas, K. A. Thorne, M. R. Todd, C. I. Torrie, G. Traylor, A. S. Ubhi, G. Vajente, J. Vanosky, A. Vecchio, P. J. Veitch, A. M. Vibhute, E. R. G. von Reis, J. Warner, B. Weaver, R. Weiss, C. Whittle, B. Willke, C. C. Wipf, J. L. Wright, V. A. Xu, H. Y. Yamamoto, L. Zhang, M. E. Zucker

Astrophysics of Galaxies

A Kinematic Study of Wolf-Rayet Stars at the Galactic Center I: Binary Candidates and Constraints on the Binary Fraction

Rory O. Bentley, Tuan Do, Andrea Ghez et al. (+13 more)

We report the binary fraction of Wolf-Rayet (WR) stars within 0.5~pc of the Galactic center obtained through the longest time-baseline (1994-2024) kinematic study of this population of stars. The new radial velocity ($v_{z}$) data we present is primarily from the W. M. Keck Observatory, with additional $v_{z}$ measurements from Gemini North Observatory. When combining our new $v_{z}$ measurements with literature measurements, we find $v_{z}$ variations suggesting the presence of a companion for five out of 27 WR stars, of which two are newly identified here (IRS~13E4, S8-181), along with three previously detected binaries (IRS~16SW, IRS~16NE, S4-258). Based on our experimental sensitivity and expected properties of the underlying population, we infer the binary fraction of the WR stars in the Galactic center to be 0.56$\pm$0.18. This is consistent with previous photometric studies of the young stars in the Galactic center, and with the binary fraction of field WR stars. When our results are combined with the results of previous photometric work, we find a binary fraction of 0.69$\pm$0.17 for the WR stars in the Galactic center.
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All authors Rory O. Bentley, Tuan Do, Andrea Ghez, Devin Chu, Anna Ciurlo, Abhimat K. Gautam, Zoë Haggard, Matthew W. Hosek Jr., Kelly Kosmo O'neil, Rebecca Lewis-Merrill, Gregory D. Martinez, Anna Pusack, Shoko Sakai, Jessica R. Lu, Mark R. Morris, Keith Matthews

High Energy Astrophysical Phenomena

Complex Analysis of Askaryan Radiation: UHECR Reconstruction

J. C. Hanson and D. Ibanez-Rodriguez

Ultra-high energy cosmic rays (UHECR) can produce relativistic cascades that emit radio-frequency (RF) pulses in the 0.1-1 GHz bandwidth via two distinct effects: the geomagnetic effect, and the Askaryan effect. The geomagnetic effect occurs when the magnetic field of the Earth causes cascade charges to form a transverse current that radiates linearly polarized radiation aligned with the Lorentz force direction. The Askaryan effect is caused by the net negative charge excess in the cascade that radiates linearly polarized radiation along the Cherenkov cone. When UHECR cascades enter solid, RF transparent matter at altitudes where the cascade develops, Askaryan radiation created in the solid medium can propagate to RF detectors. The Askaryan Radio Array (ARA) at the South Pole has observed 13 UHECR candidates in precisely this fashion. We present an analytical model that confirms the events are UHECRs. The model includes Askaryan radiation created within the ice sheet and the ARA RF channel response. The coherently summed waveforms (CSWs) from the UHECR candidates match our model with correlation coefficients between 0.69 and 0.86, and with minimal fractional power differences. Finally, we demonstrate how to obtain the Askaryan E-field from our model, and that it matches the results from the ARA collaboration.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Black Bounce Solutions from a Self-Interacting 3-Form Field in General Relativity

Francisco S.N. Lobo and Manuel E. Rodrigues

We construct a new class of black-bounce solutions sourced by a self-interacting 3-form field minimally coupled to general relativity and a scalar field. The 3-form field, which naturally arises in string theory, supergravity, and cosmological models, provides the anisotropic effective stresses required to sustain regular geometries that interpolate smoothly between black holes and traversable wormholes. By exploiting the Hodge duality between a 3-form and a 1-form in four dimensions, we reduce the field equations and obtain exact solutions through the direct integration of the coupled equations of motion. In particular, the solutions are derived from algebraic combinations and manipulations of the Einstein, scalar, and 3-form field equations, starting from a complete action principle, without employing the usual reconstruction procedure in which the metric ansatz is imposed a priori and the matter sector is reconstructed afterwards. This approach reveals two distinct classes of solutions. The first one yields a globally phantom scalar field and a metric function with a characteristic arctangent dependence, reducing to the Schwarzschild-(anti) de Sitter spacetime in the limit of vanishing 3-form coupling. The second class produces a constant 3-form Lagrangian and, remarkably, a partially canonical scalar field, namely phantom only near the bounce and canonical outside the event horizon, a feature previously attainable mainly in modified theories of gravity, but which emerges here within pure general relativity. Both families are globally regular, as confirmed by the finiteness of the Kretschmann scalar, and exhibit an asymmetric horizon structure inherited from the 3-form energy-density distribution. These results demonstrate that the 3-form black-bounce framework is both mathematically consistent and observationally viable.
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Cosmology and Nongalactic Astrophysics

On the potential for inhomogeneities to mimic an evolving dark energy

Hayley J. Macpherson and Georgios Valogiannis

In this work we explore the ability of inhomogeneities to result in an apparent dynamical evolution of dark energy. The idea that inhomogeneities may alter the expansion history of the Universe is not a new one. However, with the current excitement surrounding the inferred time-evolution of the equation of state of dark energy by the Dark Energy Spectroscopic Instrument (DESI), combined with Cosmic Microwave Background (CMB) and supernovae observations, it is worth revisiting. We use numerical relativity simulations of large-scale structure formation combined with nonlinear general-relativistic ray tracing to infer dark energy parameters for synthetic observers. We adopt a simplified set-up to roughly mimic the observational properties of the DESI plus supernovae and CMB constraints. In our small sample of 20 observers, we find one who infers parameters consistent with the DESI values at 2-$\sigma$ significance. While it is rare in our limited sample size, we show that it is at least possible for observers to infer significant non-LCDM parameters when their universe is well-described by a cosmological constant on average.
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Earth and Planetary Astrophysics

Ultraviolet-Driven Atmospheric Degeneracies Challenge Conventional Biosignature Frameworks for Terrestrial Planets with Ultracool M Dwarf Hosts: An Archean-Analog TRAPPIST-1 e Case Study

Evan L. Sneed, Edward W. Schwieterman, Sarah R. Peacock et al. (+2 more)

The ultraviolet (UV) spectrum of a host star strongly shapes the atmospheric composition and potential biosignatures of its planets. This relationship may be especially important for the planets orbiting TRAPPIST-1, an M8V star with substantially different published UV spectral energy distributions (SEDs). Using a one-dimensional photochemical model, we quantify how these SED uncertainties affect Archean Earth-like atmospheric analogs on TRAPPIST-1 e with and without biospheres. We emphasize Earth's Archean epoch because it represents a planet in transition from primarily abiotic to biotic controls on atmospheric composition. Different stellar spectra produce order-of-magnitude variations in the predicted abundances of CH4, CO, O2, and O3, thereby generating photochemical degeneracies that complicate the interpretation of potential biosignatures. For one TRAPPIST-1 UV reconstruction, a modeled atmosphere with abiotic deposition velocities and volcanic CH4 input can sustain simultaneous spectrally discernible CH4 and O3, yielding a potential false-positive disequilibrium biosignature. For all SEDs tested, surface deposition consistent with microbially-mediated CO consumption allows substantial O2 and O3 accumulation even without oxygenic photosynthesis, implying that oxygen-rich atmospheres around ultracool M dwarfs may not uniquely trace oxygenic ecosystems. Across our models, CO remains a powerful discriminator between abiotic and biotic surface boundary assumptions. Overall, we show that the abundances of co-occurring CH4, CO, and O3 can vary by orders of magnitude, depending on the assumed UV SED, creating ambiguities in interpreting atmospheric biosignatures, though observability may be challenging with current capabilities. Reducing UV spectral uncertainties is therefore essential for assessing surface-to-atmosphere interactions of temperate exoplanets around ultracool M dwarfs.
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All authors Evan L. Sneed, Edward W. Schwieterman, Sarah R. Peacock, Nicholas F. Wogan, Timothy W. Lyons

Instrumentation and Methods for Astrophysics

Building a Roadmap for Hubble science into the 2030s: Crucial UV spectroscopy of Oe stars in nearby galaxies

A. Wofford, D. Pauli, A.A.C. Sander et al. (+12 more)

Hubble's unique COS G130M+G160M and STIS E140M UV spectral capabilities are essential for characterizing and understanding fundamental properties of main-sequence O-type emission-line (Oe) stars. These are fast rotators, and some are believed to be spun up in binaries. UV medium resolution observations of these stars are crucial for understanding massive binaries and their role in galaxy evolution. Oe stars are more prevalent at low metallicity, where they are highly under-studied, but UV spectra of these stars at all metallicities are needed. Observations of these stars in the 2030's with Hubble are particularly important in the era of ultra wide-field IFU optical and transient astronomy surveys. Ultimately, these observations will inform future UV observations with the Habitable Worlds Observatory.
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All authors A. Wofford, D. Pauli, A.A.C. Sander, O. Aranguré, M.S. Oey, O.G. Telford, P.A. Crowther, J. S. Vink, Tomer Shenar, M. Gull, L.P. Martins, S. Simón-Díaz, S. Zharikov, L. M. Oskinova, L.J. Smith

Instrumentation and Methods for Astrophysics

A Critical UV Legacy: A Hubble Roadmap for HWO Science Readiness

Sarah Peacock, Aiden S. Zelakewicz, Lisa Kaltenegger et al. (+14 more)

The Habitable Worlds Observatory (HWO) will provide the first opportunity to directly image and spectrally characterize terrestrial exoplanets in the habitable zones of nearby stars. Maximizing its scientific return requires a comprehensive understanding of the high-energy radiation environments of target stars, which shape planetary atmospheres and govern the production, destruction, and detectability of biosignatures. Ultraviolet (UV) radiation plays a particularly critical role in atmospheric chemistry. Far-ultraviolet (FUV) and near-ultraviolet (NUV) photons regulate key photochemical pathways, influence ozone stability, and drive the formation of prebiotic molecules. However, the majority of high-priority HWO target stars lack high-quality UV observations. Existing datasets are sparse, heterogeneous, or limited by calibration uncertainties, and no comparable UV observatory is expected for at least 5-10 years (with UVEX offering more limited spectral resolution, wavelength coverage, and sensitivity). The Hubble Space Telescope (HST) remains the only observatory capable of acquiring high-resolution FUV and NUV spectra for these targets over the next 10-15 years. We therefore advocate for a coordinated HST program to systematically obtain UV spectra of high-priority HWO targets, ideally in conjunction with X-ray observations. This effort is essential for enabling accurate target prioritization, constraining stellar radiation environments, and ensuring robust interpretation of future HWO observations.
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All authors Sarah Peacock, Aiden S. Zelakewicz, Lisa Kaltenegger, Breanna A. Binder, José A. Caballero, Lía Corrales, Kevin France, Cynthia Froning, Eric Mamajek, Seth Redfield, Tyler Richey-Yowell, Keighley Rockcliffe, Edward Schwieterman, Riccardo Spinelli, Noah Tuchow, David Wilson, Allison Youngblood

Solar and Stellar Astrophysics

Entropy-mode imprints in the solar corona: non-exponential damping and phase shifts of compressive oscillations

Dmitrii Kolotkov, Sergey Belov and Mohamed Sherif

Magnetohydrodynamic (MHD) waves in coronal loops provide key seismological diagnostics through their characteristic time signatures. While fast and slow magnetoacoustic modes are routinely exploited, the entropy mode, despite being another eigenmode of the system, remains largely inaccessible due to its non-propagating and non-oscillatory nature. We identify possible observable time-domain signatures of the entropy mode and its indirect effects. Our approach exploits the intrinsically non-adiabatic conditions of the solar corona, under which the entropy mode is closely linked to the compressive slow mode. We consider a one-dimensional coronal loop model with field-aligned thermal conduction, where standing slow and entropy modes are simultaneously excited. We show that the entropy mode leaves distinct imprints on the total loop temperature and density perturbations. Specifically, its rapid decay relative to the slow mode produces a non-exponential damping profile during the initial oscillation cycles and introduces a pronounced asymmetry between the upper and lower temperature and density envelopes. These effects arise naturally from the superposition of two exponentially decaying components with different damping timescales. Furthermore, deviations from the canonical quarter-period phase shift between temperature/density and velocity perturbations in the standing slow mode are explained by the entropy-mode effect. We conclude that the entropy mode may be detected through its impact on compressive oscillations. Revealing its role in non-exponential damping, envelope asymmetry, and phase shifts of compressive oscillations makes the entropy mode potentially accessible to observations and lays the foundation for solar and stellar seismological applications.
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Cosmology and Nongalactic Astrophysics

The DESI results impact the local determination of $H_0$

Michael S. Turner and Dragan Huterer

Measurements of baryon acoustic oscillations (BAO) by the Dark Energy Spectroscopic Instrument (DESI) have revealed evidence for dark energy that evolves. If local distance measurements are analyzed with the $w_0w_a$ models preferred by the DESI measurements, the value for the Hubble constant can be as much as $2.5\,\mathrm{km\,s^{-1}Mpc^{-1}}$ smaller than the value obtained assuming $\Lambda$CDM. When these $w_0w_a$ models are further constrained by cosmic microwave background (CMB) and type Ia supernova (SNIa) data, the downward shift is $1.1 \pm 0.38\,\mathrm{km\,s^{-1}Mpc^{-1}}$ (DESI + CMB) and $0.5 \pm 0.1\,\mathrm{km\,s^{-1}Mpc^{-1}}$ (DESI + CMB + SNIa). The dependence of local determinations of $H_0$ on the background cosmology, combined with the fact that the low-redshift cosmology is not well constrained, is relevant to the Hubble tension.
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Astrophysics of Galaxies

Bulk vs. turbulent motions at the centres of galaxy clusters: AGN-driven turbulence according to TNG-Cluster

Bipradeep Saha, Annalisa Pillepich, Joey Braspenning et al. (+3 more)

The highly dynamic intracluster medium (ICM) influences cluster thermodynamic evolution and probes key physical processes. Quantifying the non-thermal motions is therefore essential for understanding cluster physics and interpreting high spectral-resolution X-ray observations from telescopes like XRISM. We quantify bulk and turbulent gas motions in 352 galaxy clusters at $z=0$ (${\rm M_{200c}=10^{14.3-15.4}\, M_\odot}$) from the TNG-Cluster suite of magneto-hydrodynamical galaxy simulations. We use a multi-scale filtering Reynolds decomposition to separate total gas velocities into bulk (coherent) and turbulent (small-scale fluctuations) components. We primarily focus on the hot X-ray emitting gas in the central core regions. According to TNG-Cluster, majority of the ICM has subsonic turbulence but with broad velocity distributions reaching $\mathcal{M}_{\rm Turb}\sim 10$ and large cluster-to-cluster variations. In cluster centres, turbulence contributes less than half of the total velocity dispersion $(\sigma_{v\rm,Turb } \sim 0.5 ~\sigma_{v,\rm Total})$ for most clusters, with typical turbulent velocity dispersions of $50-75$ km s$^{-1}$ across the mass range, and with sub per cent levels of turbulent pressure support. Clusters that are strong cool cores, or have X-ray cavities, or experienced recent SMBH feedback energy injections exhibit systematically larger turbulent velocity dispersions and more prominent turbulent velocity tails. On average, the turbulent velocity dispersion peaks in cluster centres, decreases slightly to a minimum at $0.1-0.2 \, R_{\rm500c}$, then rises again. Our analysis shows that SMBH feedback is a key driver of turbulence in cluster cores, generating strong but short-lived motion alongside high-velocity outflows. It also calls for caution for interpreting XRISM observations.
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All authors Bipradeep Saha, Annalisa Pillepich, Joey Braspenning, Marine Prunier, Dimitris Chatzigiannakis, Dylan Nelson

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

Running Vacuum in the expanding Universe: a unified QFT paradigm for Inflation and Dark Energy

Joan Solà Peracaula

The concordance $\Lambda$CDM model, based on a rigid $\Lambda$-term for the entire cosmic history, has been in crisis for a long time. In our expanding Universe, an evolving $\Lambda$ with the expansion is intuitively much more reasonable. In the running vacuum model (RVM) framework, based on quantum field theory (QFT) in curved spacetime, quantum effects induce a vacuum energy density (VED) $\rho_{\rm vac}=\Lambda/(8\pi G)$ which is a function of the Hubble rate $H$ and its time derivatives, $\rho_{\rm vac}=\rho_{\rm vac}(H, \dot{H},\ddot{H},\dots)$. Currently, $\rho_{\rm vac}$ evolves very slowly with the expansion, $\delta\rho_{\rm vac}\sim {\cal O}(m_{Pl} ^2 H^2)$, and this fact provides a possible fundamental origin of dark energy (DE), conceived as dynamical vacuum energy. In the RVM, Newton's $G$ is also evolving, but much more slowly (logarithmically with $H$): $G=G(\ln H)$. In the very early universe, the vacuum fluctuations induce higher (even) powers, e.g. $\sim H^4$, capable of triggering fast inflation in a very short period, in which $H$ is very large and approximately constant. This is the mechanism of `RVM-inflation'. It does not require an `inflaton' field since inflation is brought about by pure QFT effects on the dynamical background. It differs from Starobinsky's inflation, where $H$ is never constant. Furthermore, the dynamics of $\rho_{\rm vac}(H)$ and $G(H)$ can also have implications on the frequently discussed possibility that the fundamental `constants' of Nature can be mildly evolving with the cosmic expansion. Putting things together, a unified QFT framework of dark energy and inflation ensues as a realistic theory for the description of the universe as a whole on fundamental grounds. In it, dynamical VED is predicted and is much welcomed, since it fits in with current DESI measurements, preferring dynamical DE over a rigid $\Lambda$ term.
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Earth and Planetary Astrophysics

Sky-Plane Velocity Distributions of Interstellar Objects and Implications for Their Detection

Cassidy E. Walker and Darryl Z. Seligman

In the past decade, three macroscopic-scale interstellar objects have been discovered, implying that a larger galactic population exists. In this paper, we investigate the possibility that the rapid sky-plane velocities of interstellar objects may preclude their discovery. We provide an analytic solution for the apparent sky motion of an object on an arbitrary orbit observed at an arbitrary location which is more efficient and requires less overhead than the numerical approach. This formula is applied to evaluate the typical sky motion of an interstellar object as a function of its orbit and limiting magnitude/distance. We generate three synthetic populations of $\sim10^5$ interstellar objects within heliocentric spheres of radii 1.2, 3.0, and 5.0 AU, and calculate the sky motion for these objects when they reach a range of limiting magnitudes for multiple populations of interstellar asteroids and comets. The sky motions of the three known interstellar objects are broadly characteristic of populations with similar absolute magnitudes. Moreover, the intrinsically brighter objects reach detection magnitude thresholds at lower on-sky speeds than the dim objects, and active comets at even lower speeds for the same apparent magnitudes. The tails of these distributions extend to speeds faster than the discovery motion of 1I. Therefore, the potentially rapid sky motion of interstellar objects should be taken into account when attempting to link hyperbolic trajectories in survey data.
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High Energy Astrophysical Phenomena

Constraining Orbital Eccentricity of a Supermassive Black Hole Binary Candidate PKS 2131-0211

Avinash Kumar Paladi, A. Gopakumar, Sushmita Agarwal et al. (+1 more)

A detailed analysis of the decades-long radio light curve of blazar PKS 2131-021 showed epochs of sinusoidal variations in the radio flux density time-series as detailed in O'Neill et al. (2022). The observed sinusoidal flux modulation arises naturally from relativistic Doppler boosting of the jet when the jet-emitting supermassive black hole (SMBH) orbits its companion. For SMBHs in circular orbits, this scenario yields sinusoidal light curves, offering a simple kinematic explanation for the observed variability in PKS 2131-021. We present an approach that incorporates the effects of orbital eccentricity into the Kinematic Orbital model for PKS 2131-021, using the Keplerian parametric solution to describe the SMBH binary orbit. Using the available radio light curve data, we demonstrate that the proposed SMBH binary likely possesses a residual orbital eccentricity, which we constrain through detailed Bayesian parameter estimation studies to be 0.053 \pm 0.015 with a Bayes factor of 3.15 over the circular model. However, when the analysis accounts for the presence of red noise in the data using a Damped Random Walk (DRW) process, the circular model is preferred, giving an eccentricity upper limit of e < 0.15. Nevertheless, our efforts reveal that the Circular+DRW model is strongly favored. This model consistently recovers a coherent periodic signal across all datasets, with the orbital period remaining well-defined even when accounting for broader uncertainties. This analysis incorporated archival observations from the Haystack Observatory, the University of Michigan Radio Astronomy Observatory (UMRAO), and the Owens Valley Radio Observatory (OVRO), spanning the period from 1975 to 2021, compiled by O'Neill et al. (2022).
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All authors Avinash Kumar Paladi, A. Gopakumar, Sushmita Agarwal, Fazal Kareem

Astrophysics of Galaxies · Cross-listed from physics.plasm-ph

Behavior of kinetic instabilities in a dynamically forming resonant distribution

E. J. Hartigan-O'Connor, T. Barberis, E. G. Devin et al. (+2 more)

Instabilities driven by energetic particles are central to the physics of a burning plasma. The majority of kinetic simulations and reduced models assume that the unstable distribution is already fully established when energetic-particle-driven modes grow unstable. In realistic scenarios, however, energetic particles may accumulate in the resonance on an effective timescale comparable to the growth rate of the instability, meaning that the formation of the resonant distribution and the growth of the unstable mode must be treated concurrently. We study the behavior of these instabilities in the presence of such a dynamically forming distribution, evaluating two distinct metrics which measure how close a mode is to its linear stability threshold and how close a mode remains to its nonlinear stability threshold. It is found that saturation at large $\omega_b/\nu_\text{eff}$ (where $\omega_b$ is the bounce frequency of deeply trapped particles and $\nu_\text{eff}$ is the effective scattering rate at a resonance), normally associated with strongly driven excitation, can be achieved even if dynamically the mode remains at all times near its nonlinear stability threshold. We extend existing analytic models for near-marginal and far from marginal modes allowing for a time-dependent linear growth rate, deriving explicit expressions for the mode amplitude evolution. These formulas are shown to agree with nonlinear kinetic simulations. The discrepancies between the case of a dynamically forming distribution and the case of a fully formed distribution are shown to be particularly pronounced for energetic particle distributions which relax diffusively.
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All authors E. J. Hartigan-O'Connor, T. Barberis, E. G. Devin, A. Bierwage, V. N. Duarte

Astrophysics of Galaxies

Strong [OIII]$+$H$\beta$ emitters dominated the ionizing budget at $z\sim7$

Isak Wold, Sangeeta Malhotra and James Rhoads

We quantify the ionizing photon production at $z\sim7$ using the deepest spectroscopically confirmed sample of strong [OIII]$+$H$\beta$ emitters (rest-frame EW$>740$ A) in the Abell 2744 field. Leveraging ultra-deep UNCOVER F410M imaging ($5\sigma\sim29$ AB) and gravitational lensing, we probe an order of magnitude deeper than previous JWST WFSS [OIII] studies, reaching a luminosity limit of $\log(L_{\rm{[OIII]}+\rm{H}\beta}/\text{erg s}^{-1})=41.3$. Our rest-frame optical emission-line selection probes some of the youngest, metal- and dust-poor galaxies, identifying a large population of continuum-faint, ionizing candidates. NIRSpec follow-up of a luminosity-representative subset confirms $72\%$ of targets, providing detailed characterization of 18 emitters. Balmer decrements reveal negligible dust, while strong-line diagnostics indicate extremely low metallicities ($12+\log(\text{O/H})=6.8\text{--}7.7$). With typical [OII]/[OIII] ratios of $0.054\pm0.007$, we infer an average Lyman continuum escape fraction near the canonical $f_{\text{esc}}=20\%$. Correcting for the spectroscopic confirmation rate, we find that these high-EW emitters represent $56\pm12\%$ of the total UV-selected population by number density. Integrated to our survey limits, the ionizing budget of these emitters ($\log(\dot{N}_{\rm ion}/{\rm s}^{-1}\,\text{Mpc}^{-3})=50.63\pm0.05$) accounts for $\sim70\%$ of the total budget required for reionization at $z\sim7$. This result is consistent with empirical benchmarks. These results establish [OIII]$+$H$\beta$ selection as a powerful, dust-insensitive probe, showing that known galaxy populations significantly power reionization.
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High Energy Astrophysical Phenomena

How Common Are Common Envelopes? Quantifying Their Role in Forming Gravitational-Wave Sources

Floor S. Broekgaarden, Ana Lam, Sasha Levina et al. (+14 more)

A central goal of gravitational-wave astronomy is to use merging binary black hole (BBH), black hole-neutron star (BHNS), and binary neutron star (BNS) systems as fossils to reconstruct the formation and evolution of massive stars across cosmic time. In practice, this inference relies on population-synthesis models that map massive stellar binaries to merging compact objects. However, these models disagree on the dominant orbital-hardening mechanisms within isolated binary evolution, particularly on whether common-envelope (CE) evolution is required. To address this, we compile and systematically compare formation-channel predictions from more than 200 isolated-binary population-synthesis simulations, organized within a unified hierarchical taxonomy. We find that BBH and BHNS formation pathways span nearly the full allowed range from CE-dominated to without-CE-dominated evolution (0-100%), while often predicting similar merger rates, revealing a fundamental degeneracy: merger-rate measurements alone do not uniquely constrain the underlying evolutionary pathways. In contrast, BNS formation proceeds almost exclusively through channels involving at least one CE phase (>90-100%), suggesting CE evolution plays a qualitatively different role in BNS than in BBH and BHNS formation. The relative contributions of with-CE and without-CE pathways are governed primarily by assumptions controlling mass-transfer stability, angular-momentum loss, CE efficiency, and supernova physics, which often act non-linearly and in correlated fashion, such that trends from one-at-a-time parameter variations do not generalize across simulation frameworks. Robust interpretation of gravitational-wave populations will therefore require transparent formation-channel definitions, reproducible analysis pipelines, systematic cross-code comparisons, and observational constraints that extend beyond merger rates alone.
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All authors Floor S. Broekgaarden, Ana Lam, Sasha Levina, Jakub Klencki, Kyle A. Rocha, Lieke van Son, Steffani M. Grondin, Monica Gallegos-Garcia, Brian D. Metzger, Enrico Ramirez-Ruiz, Angela Twum, Melanie Santiago, Julia Haynes, Tyler B. Smith, Amedeo Romagnolo, Edo Berger, Lucas M. de Sá

Solar and Stellar Astrophysics

Hot Degenerate Components in Blue Stragglers: A Multi-Wavelength SED Analysis of Nine Open Clusters with Swift/UVOT

Deniz Cennet Ç{\i}nar, D. Bisht, Selçuk Bilir et al. (+2 more)

We present a homogeneous multi-wavelength analysis of 35 blue straggler star (BSS) candidates in nine open clusters, combining Swift/UVOT near-ultraviolet data with Gaia DR3 astrometry and optical-to-infrared photometry. We construct spectral energy distributions (SEDs) to search for signatures of hot companions associated with past mass transfer. Among the sample, 15 BSSs (~43%) show ultraviolet excesses that are better described by two-component SED fits. The inferred companions are consistent with hot white dwarfs and pre-extremely low-mass (pre-ELM) white dwarf candidates, suggesting systems observed at different stages following mass transfer. We examine the radial distribution of the BSSs and find evidence for mass segregation in dynamically evolved clusters, a result that is broadly consistent with the estimated half-mass relaxation timescales of the host systems. To place the clusters in a Galactic context, we compute their orbits using galpy, obtaining low eccentricities (e <= 0.1) and disk-like trajectories. We also find a positive relation between the half-number radius of the BSS population (r50) and the total number of BSSs. Overall, our results are consistent with a scenario in which the BSS population in these clusters is dominated by binary evolution. The systems identified here provide observational constraints on post-mass-transfer evolutionary phases. While the number of robust detections is limited and intrinsic degeneracies remain in SED-based decomposition, these results provide a useful foundation for future spectroscopic confirmation.
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All authors Deniz Cennet Ç{\i}nar, D. Bisht, Selçuk Bilir, Songmei Qin, Leila Saker

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

Gravitational Wave Imprints of a High-Quality Axion and the Origin of Flavor Hierarchies

K.S. Babu, Sai Charan Chandrasekar, Sudip Jana et al. (+1 more)

Axions, arising from an anomalous global Peccei-Quinn symmetry $U(1)_{\text{PQ}}$, offer a compelling solution to the strong CP problem but are vulnerable to Planck-suppressed operators. Gauged abelian flavor symmetries $U(1)_F$, invoked to explain the flavor hierarchies via the Froggatt-Nielsen mechanism, can naturally shield the axion from such effects, yielding an accidental high-quality flavored axion with unit domain wall number. Such constructions predict two complementary signatures: (i) flavor-changing neutral currents from $K\to\pi a$ decays, typically associated with high flavor scales $\Lambda_{\text{FN}}\gtrsim f_a$, and (ii) stochastic Gravitational Waves (GWs) sourced by the evolution and decay of gauged flavonic and axionic cosmic-string networks. In addition, global axionic strings can efficiently radiate axions, potentially accounting for the observed dark matter relic abundance. We show that the resulting characteristic plateau–valley structure in the GW spectrum provides a distinctive and powerful probe of high-quality flavored axion dark matter models, complementary to low-energy flavor experiments.
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All authors K.S. Babu, Sai Charan Chandrasekar, Sudip Jana, Sudip Manna

Solar and Stellar Astrophysics

The Influence of Opacity on Inferred MHD Wave Signatures in the Lower Solar Atmosphere

Samuel J. Skirvin, Samuel D. T. Grant, David B. Jess et al. (+8 more)

Magnetohydrodynamic wave activity in small-scale magnetic structures, such as solar pores, provides key insights into energy transport in the lower solar atmosphere. This study presents high-resolution observations of ten solar pores contained within a 43 x 43 Mm$^2$ field of view, obtained with the CRISP instrument at the Swedish 1-m Solar Telescope. We investigate the temporal behaviour of the line-of-sight velocity (vlos) and magnetic field (blos) oscillations within the pore structures. Using SIR inversions, we analyse the oscillatory signals at multiple optical depths (log $\tau$ levels) to assess how variations in geometric height (z) and temperature relate to the observed blos fluctuations. Our results reveal that higher-frequency oscillations (> 6 mHz) exhibit strong coherences with in-phase fluctuations between blos and z across atmospheric layers, consistent with upward-propagating magneto-acoustic waves. In contrast, coherent lower-frequency oscillations display significant phase differences, which may arise from opacity effects contaminating the inversion response. These findings highlight the importance of accounting for opacity effects when interpreting magnetic oscillations, with direct implications for forthcoming high-precision magnetic diagnostics from facilities such as DKIST.
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All authors Samuel J. Skirvin, Samuel D. T. Grant, David B. Jess, Ryan J. Campbell, Shahin Jafarzadeh, Mika V. Kontiainen, Michele Berretti, Timothy J. Duckenfield, Glen Chambers, Marco Stangalini, Luc Rouppe van der Voort

High Energy Astrophysical Phenomena

The WISSHFUL program: the highest redshift UFO discovered in a non-lensed QSO

G. Lanzuisi, L. Borrelli, E. Piconcelli et al. (+28 more)

We present the first results from the WISSHFUL program, an XMM-Newton heritage program targeting luminous QSOs at Cosmic Noon. We report on recent simultaneous XMM-Newton and NuSTAR observations of the Super-Eddington accreting quasar WISSH13 at z=3.294, which provide the highest quality broadband X-ray spectrum to date for a non-lensed QSO at this redshift. Physical modeling of the continuum reveals a soft photon index ($\Gamma\sim2$) and strong reflection ($R\sim1.4-1.8$), despite the weak narrow Fe emission, and a low high-energy cut-off ($E_{cut}\sim60-80$ keV, $kTe = 15-20$ keV, depending on the model adopted). Most notably, we detect two significant (at $96.7\%$ and $98.9\%$ confidence level, respectively) absorption features at $\sim7.5$ and $\sim10$ keV rest-frame, interpreted as a blueshifted blend of Fe XXV He$\alpha$ and Fe XXVI Ly$\alpha$. These features indicate the presence of two kinematic components of a highly ionized, high column Ultra-Fast Outflow (UFO) with a velocity of $v_{out}\sim0.1c$ and $v_{out}\sim0.3c$, respectively. The slower wind is consistently detected in an archival 2017 XMM-Newton observation, whereas the faster wind is detected only in 2024. This stratified and variable wind exhibits extreme energetics, with a mass outflow rate of $\dot{M}_{out}\sim20M_{\odot}/yr$ (corresponding to $15\% \dot{M}_{acc}$) for each component, and a kinetic power of the order of $\sim1$ and $\sim10\%$ of the bolometric luminosity, respectively. While this represents one of the most powerful UFOs ever detected, its kinetic power is a similar fraction of the QSO's bolometric luminosity compared to lower-redshift AGN. We present several theoretical frameworks to explain the peculiar accretion and ejection properties of this remarkable QSO at Cosmic Noon.
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All authors G. Lanzuisi, L. Borrelli, E. Piconcelli, G. Chartas, A. Luminari, J. Reeves, V. Braito, E. Bertola, S. Bianchi, A. Comastri, M. Brusa, C. Vignali, F. Vito, S. Marchesi, M. Cappi, M. Dadina, L. Zappacosta, A. Tortosa, M. Bischetti, G. Vietri, F. Salvestrini, G. Bruni, M. Fanelli, E. Kammoun, X. Zhao, G. Matzeu, F. Tombesi, A. Marinucci, M. Gaspari, T. Misawa, D. Stern

Astrophysics of Galaxies

A Decade to Map the Diffuse Universe: FRB-QSO Pairs with HST/COS Spectroscopy

Jessica Werk, Matthew McQuinn, J. Xavier Prochaska et al. (+16 more)

Jointly analyzing the sightlines of arcsecond-localized fast radio bursts (FRBs) and UV-bright quasars (QSOs) nearby in projection has the potential to provide strong constraints on the phases, mass distributions, and magnetic structure of the diffuse universe. Each probe supplies what the other cannot: FRBs provide integrated electron columns (DM), line-of-sight magnetic field estimates (RM), and scattering constraints ($\tau_{\rm scatt}$) that are independent of gas phase; QSOs provide the redshift- and phase-resolved column densities needed to interpret them. Today, there are only $\sim100$ arcsecond-localized FRBs at $z < 1$, making statistical FRB-QSO pair surveys impossible. By 2035, there will be $\sim10^{5}$. Using the most recent FRB localization forecasts and UV-bright QSO catalogs, we estimate that next-generation interferometers will yield thousands of FRB–QSO pairs at angular separations $\theta < 10'$, including $\sim100$ pairs at $\theta < 1'$, over a common 20,000\,deg$^2$ footprint by 2035. We outline the science enabled by this sample: constraints on CGM ionization fractions and baryon masses; observational constraints on the role of magnetic fields and turbulence in the CGM and cosmic web; sightline-by-sightline partitioning of the cosmic DM budget; and three-dimensional mapping of the multiphase Milky Way and M31 halos. Together, these measurements directly address the physics of feedback, non-thermal pressure support, and energy balance in the diffuse gas that regulates galaxy growth. HST/COS is the only instrument that can carry out this program, and the 2030s are the only decade in which to do it before Habitable Worlds Observatory (HWO) defines the next era of diffuse universe science.
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All authors Jessica Werk, Matthew McQuinn, J. Xavier Prochaska, Sunil Simha, Rongmon Bordoloi, Liam Connor, Andrew Fox, J. Chris Howk, Cameron Hummels, Lordrick Kahinga, Victoria Kaspi, Khee-Gan Lee, Nicolas Lehner, Kiyoshi Masui, Benjamin Oppenheimer, Vikram Ravi, Kate Rubin, Kirill Tchernyshyov, Yong Zheng

High Energy Astrophysical Phenomena

Constraining the jet base emission of M87* with past and future Event Horizon Telescope observations

Noemi La Bella, Michael Janssen, Britton Jeter et al. (+5 more)

We investigate the detectability of the jet base of M87* at Event Horizon Telescope (EHT) observing frequencies. Although M87 is known to host a prominent relativistic jet, detecting jet emission close to the black hole at horizon scales remains challenging. Our goal is to determine the minimum jet intensity that can be reliably detected with the recent EHT array configurations. We use synthetic EHT data generated for three array configurations corresponding to the 2021 and 2022 observing campaigns and to a near future EHT campaign. As input models, we employ semi analytic accretion jet models in which the jet emission can be tuned independently of the accretion flow. The synthetic data are reconstructed with regularized maximum likelihood and Bayesian imaging. Jet detectability is assessed through flux density recovery, image fidelity, and uncertainty maps. We find that jet detectability strongly depends on the jet intensity, the array configuration, and imaging methodology. Using our analysis, we determine a lower limit on the jet intensity that can be reliably recovered. The 2022 EHT array configuration represents a significant improvement over earlier arrays, enabling a more robust reconstruction of faint jet features. Our results indicate that the current EHT array is already sensitive to weak jet emission at horizon scales in M87*. The improved short-baseline coverage introduced in 2022 makes faint inner jet features more easily detectable. If the inner jet contributes a significant fraction of the unresolved compact flux, it should become visible in post-2021 observations. On the other hand, if no clear jet signature is found, this would suggest that the horizon-scale jet contributes only a small part of the compact emission. The continued expansion of the EHT will further improve the detection of such jet emission in M87*.
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All authors Noemi La Bella, Michael Janssen, Britton Jeter, Hendrik Müller, Bram Van de Berg, Hung-Yi Pu, Paul Tiede, Heino Falcke

Cosmology and Nongalactic Astrophysics

AGN Line-Intensity Mapping: A Probe of Faint Black Holes at Cosmic Noon

Eli Visbal and Greg L. Bryan

We propose line-intensity mapping (LIM) as a new probe of active galactic nuclei (AGN). By cross-correlating [Ne V] intensity maps with galaxy redshift surveys, we show that the cumulative AGN line emission can be detected even when individual sources are below the detection threshold. The 97.1 eV ionization potential of [Ne V] makes it an essentially uncontaminated tracer of AGN activity, arising from the narrow line region which is accessible even in heavily obscured AGN. We forecast signal-to-noise ratios using a Fisher matrix formalism for two hypothetical future instruments: a CDIM-like instrument targeting [Ne V] $\lambda 3426$ and a PRIMA-like instrument optimized for LIM targeting [Ne V] $14.3 \mu$m. For the CDIM-like case we find strong constraints on the product of the mean AGN intensity and bias, $S_{\rm NeV} b_{\rm NeV}$, across $z=2-3$, with redshift-space distortions enabling individual constraints on $S_{\rm NeV}$ and $b_{\rm NeV}$. The LIM signal retains sensitivity to AGN below the $5\sigma$ direct detection threshold, which at $z=3$ corresponds to $L_{\rm bol} \sim 5\times10^{43}$ erg s$^{-1}$ and coincides with the faint end of existing luminosity function measurements. Roughly 10% of the total signal originates from below this threshold, with the sub-threshold population detectable at $S/N=9-4$ across $z=2-3$ (for $S_{\rm NeV} b_{\rm NeV}$). The PRIMA-like instrument achieves slightly lower signal-to-noise but provides a complementary probe of the AGN population due to the insensitivity of the $14.3 \mu$m line to dust attenuation. AGN LIM can potentially be applied to several scientific problems including tracing the total AGN emissivity history, constraining the black hole-halo connection at faint luminosities, and discriminating between supermassive black hole seeding mechanisms.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Heavy-element paleodetectors for Higgsino dark matter

Peter W. Graham, Harikrishnan Ramani and Samuel S. Y. Wong

Paleodetectors have been proposed as a new approach to direct detection of weakly interacting massive particles (WIMPs), through the search for damage tracks in ancient minerals induced by WIMP-nucleon scattering. However, for inelastic dark matter such as the Higgsino, existing paleodetector targets lack sufficiently heavy nuclei to overcome the kinematic threshold for scattering. We propose heavy-element paleodetectors as a new probe of inelastic dark matter, using ancient, radiopure minerals containing heavy elements such as lead. We identify brine precipitates from deep geothermal aquifers as a possible geological source of such minerals. Additionally, paleodetectors are uniquely sensitive to the history of the dark matter high-velocity tail, including a possible fast population induced by the Large Magellanic Cloud's close approach 50 Myr ago. Such a scenario would favor younger minerals than usually assumed in the paleodetector literature. This method can probe Higgsino mass splittings up to $\delta \simeq 920$ keV. Due to the large Higgsino-nucleon cross section, we find that even suboptimal mineral samples with ordinary radioactivity from depths of only 2 km can probe new parameter space, thus partially relaxing the stringent requirements on radiopurity and depth that constitute two significant challenges for the paleodetector program.
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Astrophysics of Galaxies

Dynamical models of cluster members to probe the total mass properties of cluster subhalos. I. A comparison with parametric strong lensing models

Nicola Bianchetti, Claudio Grillo, Giovanni Granata et al. (+6 more)

In this series of papers, we present dynamical models of cluster members in strong lensing (SL) galaxy clusters to independently probe the persistent discrepancy reported between SL models and cosmological simulations, in terms of total mass properties for the cluster subhalos. In this work, we focused our study on early-type galaxies within Abell 2744 ($z=0.309$) and MACS J0416.1-2403 ($z=0.397$). We took advantage of deep MUSE spectroscopic data, complemented with HFF photometry. We used a pipeline based on spectral fitting to perform kinematic measurements of the LOS velocity dispersion profiles of 109 cluster members. We modeled the galaxies assuming a dPIE total mass density distribution and a Jaffe stellar mass density distribution. From the models, we inferred the values of the central stellar velocity dispersion, $\sigma_0$, and the truncation radius, $r_t$, for the galaxies in our sample. We found that $\sigma_0$ is accurately recovered for all of the cluster members, while $r_t$ is reliably measured for a fraction of galaxies in our sample, with sufficiently extended radial kinematic coverage. Our dynamical models predicted LOS velocity dispersion profiles that fit the measured ones better than those inferred from SL models. We then exploited the $\sigma_0$ measurements obtained from the dynamical models to calibrate the Faber-Jackson scaling relations for the cluster members in both galaxy clusters. When comparing our relations to those obtained in previous kinematics and SL works, we found systematically higher normalization and compatible slope and scatter values. We conclude that our dynamical measurements of $\sigma_0$ and $r_t$, along with calibrated scaling relations, are more robust than previous kinematic estimates which are biased by not taking into account the effects of the PSF, and should therefore be adopted as improved initial prescriptions in future SL models.
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All authors Nicola Bianchetti, Claudio Grillo, Giovanni Granata, Pietro Bergamini, Massimo Meneghetti, Amata Mercurio, Piero Rosati, Eros Vanzella, Gabriel B. Caminha

Earth and Planetary Astrophysics

TOI-3664 b, TOI-4034 b & TOI-6564 b: Three new hot Jupiters around stars approaching the terminal age main sequence

Matthew P. Battley, Marina Lafarga, Edward Gillen et al. (+21 more)

Studying the evolution of hot Jupiters requires a sample of well-characterised systems across all evolutionary states. We present three new gas giant exoplanets around stars approaching the end of the main sequence, a comparatively unexplored epoch of hot Jupiter evolution. These planets were discovered by TESS before being vetted and confirmed through dedicated spectroscopic follow-up programmes by CARMENES, CORALIE and MINERVA-Australis. TOI-3664 b has a period of 3.30 days, a radius of 1.22 +/- 0.03 RJup and a mass of 0.36 +/- 0.12 MJup. TOI-4034 b is a short-period hot Jupiter with a period of 1.80 days, a radius of 1.58 +/- 0.02 RJup and a mass of 0.87 +/- 0.16 MJup. Meanwhile TOI-6564 b has a period of 3.99 days, radius of 1.46 +/- 0.02 RJup and mass of 0.70 +/- 0.07 MJup. All three planets have radii larger than Jupiter but sub-Jupiter masses, in line with slight inflation as their hosts increase in luminosity towards the end of the main sequence. These exoplanets' low densities and hosts' advanced evolutionary states make them interesting planets with which to study the later stages of hot Jupiter evolution. Careful analysis was undertaken to determine the ages of each system, considering astrometry, gyrochronology, stellar isochrones and lithium abundance, yielding ages of 9.0 +2.4/-2.1 Gyr, 5.7 +/- 0.5 Gyr and 4.0 +/- 1.0 Gyr for TOI-3664, TOI-4034 and TOI-6564 respectively, yet each system has a similar evolutionary state because of their differing stellar masses (0.98 +/- 0.03, 1.19 +0.13/-0.03 and 1.18 +0.16/-0.03 M*). These three planets add more steps to the "age-ladder" of exoplanetary evolution, building towards the community's goal of understanding how planets evolve over time.
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All authors Matthew P. Battley, Marina Lafarga, Edward Gillen, Monika Lendl, Solène Ulmer-Moll, Cynthia S. K. Ho, Emilio Marfil, Sergio Sousa, Yolanda Frensch, Dimitri Veras, François Bouchy, Yann Carteret, Ian J. M. Crossfield, Tyler Fairnington, Mathilde Houelle, Dan Huber, Marziye Jafariyazani, Léna Parc, Don Radford, TG Tan, Sara Tavella, Rob Wittenmyer, Duncan Wright, George Zhou

Solar and Stellar Astrophysics

Eppur binaria non é esclusa: Gaia astrometry does not disfavor a binary origin for Long Secondary Periods

Patryk Iwanek, Piotr A. Kołaczek-Szymański, Dorota M. Skowron et al. (+2 more)

We present an independent reassessment of the nearby long secondary period (LSP) stars analyzed by Shariat et al. (2026). By inspecting long-term All Sky Automated Survey (ASAS) light curves, together with Gaia Focused Product Release (Gaia FPR) radial velocity (RV) curves, for 221 LSP candidates (out of 224) located within 1.5 kpc from the Sun, we find that less than half of the sample (103 objects, $\sim 47$%) exhibit convincing LSP-like behavior. The remaining part of the sample could be more naturally interpreted as that of semi-regular variables (SRVs), characterized by irregular or multi-periodic pulsations. This indicates that the analyzed sample is significantly contaminated by non-LSP objects and therefore is not representative of the classical period-luminosity sequence-D population. Using the gaiamock tool to predict Gaia renormalized unit weight error (RUWE) values for binary systems, we show that even the nearest LSP stars do not have to exhibit elevated RUWE values as a consequence of their binarity. We also argue that the binary-nature hypothesis for LSP stars does not lead to a discrepancy between the observed and expected distance-RUWE relation for these variables.
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All authors Patryk Iwanek, Piotr A. Kołaczek-Szymański, Dorota M. Skowron, Grzegorz Pojmański, Igor Soszyński

High Energy Astrophysical Phenomena

Nonthermal Particle Acceleration by Magnetic Pumping in Pulsating Plasmas

Giuseppe Arrò, Vladimir Zhdankin and Fabio Bacchini

We present a new pulsating box setup to investigate particle acceleration in high-beta plasmas undergoing compression–expansion cycles. Our fully kinetic simulations show that particles are efficiently accelerated by magnetic pumping, producing nonthermal energy distributions with power-law tails. Numerical results are in excellent agreement with a generalized maximum entropy model that we derive, linking the power-law index of distributions to the injected energy. Our results could be relevant for understanding the origin of high-energy particles in certain high-beta space and astrophysical plasmas.
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Instrumentation and Methods for Astrophysics

Toward decision-aware AI for LSST-scale time-domain astronomy

C. R. Bom, A. Mahabal, F. Bianco et al. (+27 more)

The Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) will generate approximately (10^7) alerts per night, pushing time-domain astronomy beyond pipelines that treat discovery as a static labeling problem. We argue that LSST is better understood as a partially observed dynamical environment, in which scientific return depends on the quality of follow-up decisions made under uncertainty and finite observational resources. The central challenge is therefore to maintain evolving, uncertainty-aware representations of astrophysical sources and to select actions that maximize long-term scientific value. We propose that foundation models trained on heterogeneous time-domain data can learn survey-scale representations of source state, while decision-theoretic policies support principled, auditable allocation of follow-up resources. Embedded within human-supervised agentic systems, these components position AI as part of the operational inference loop rather than as a downstream predictive tool. The way such systems represent belief, optimize utility, and expose their reasoning will shape observational efficiency, the distribution of scientific agency, including who participates in discovery and the scientific questions that receive priority.
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All authors C. R. Bom, A. Mahabal, F. Bianco, P. Darc, B. Fraga, R. Bonito, S. Chaini, M. W. Coughlin, S. Dillmann, F. Fontinele Nunes, A. Gomboc, N. Hernitschek, X. Li, F. Z. Majidi, A. I. Malz, A. Melandri, V. Petrecca, S. Piranomonte, M. Rabus, F. Ragosta, O. Razim, M. C. Romão, N. Sarin, A. Sasli, V. A. Srećković, A. Tramuto, V. Vujčić, M. J. Vyas, Rubin LSST Transients, Variable Stars Science Collaboration