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Physics Astrophysics

astro-ph Watch Astrophysics

Wednesday 15 July

Astrophysics of Galaxies

Merging galaxies and clusters: Insights into the role of magnetic fields and the physics of radio relics

Joseph Whittingham

Mergers have long been understood to be a driver of galaxy and galaxy cluster evolution. They release tremendous amounts of gravitational potential energy - ~$10^{59}$ and ~$10^{64}$ ergs in galaxies and clusters, respectively - which is dissipated in powerful shock waves. In galaxies especially, the strong tidal effects can have profound effects on the remnant morphology. Although the modelling of mergers has a long history, it is only recently that it has been fully appreciated just how sensitive they are to a range of factors, including the existence of circumgalactic media (CGM), accretion along filaments, and pre-existing magnetic fields. Modelling these aspects in a cosmologically-consistent manner necessitates the use of high-resolution cosmological magnetohydrodynamic (MHD) simulations. In this work, we use such simulations to investigate two distinct merger-related phenomena: i) magnetic fields in galaxy mergers, and ii) the origin of radio relics in galaxy clusters.
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High Energy Astrophysical Phenomena

Temporal Memory in Repeating Fast Radio Bursts: Epsilon-Machine Reconstruction of Causal Structure in Burst Timing

Tom Kimpson and Joseph O'Leary

The emission mechanism of fast radio bursts (FRBs) remains unknown. Whether the bursts from a repeating FRB arrive at random or in a structured sequence is a key constraint on that mechanism. We apply $\varepsilon$-machine reconstruction, a tool from computational mechanics that infers the minimal model capturing all predictive information in a stochastic process. Applied to the waiting-time sequences of three repeating FRBs (FRB~20121102A and FRB~20201124A from FAST; FRB~20220912A from CHIME), the method yields the statistical complexity $C_\mu$, the minimum number of bits required for optimal prediction. Both FAST sources carry roughly one bit of temporal memory (significant against permutation surrogates, $p \leq 0.01$; per-source false-discovery-rate-adjusted $p \leq 0.028$), while FRB~20220912A is consistent with memoryless emission. FRB~20201124A's memory spans hours-to-days across four sessions, FRB~20121102A's spans hours-to-weeks across thirty-nine, and neither source shows defensible within-session predictive memory. For FRB~20121102A the ordering of those sessions is itself predictive (session-shuffle $p = 0.02$), whereas FRB~20201124A's signal reflects the contrast between heterogeneous sessions rather than their order. A simulated windowing test shows that CHIME's short transit observations would suppress comparable structure in the FAST data, leaving FRB~20220912A's null result ambiguous. This first application of $\varepsilon$-machine reconstruction to astrophysical transients yields a model-independent constraint: the bursting of at least two of these repeaters is not memoryless, but is governed by a hidden state that occupies distinct activity-rate regimes varying across observing sessions, behaviour that any viable physical model must reproduce.
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Solar and Stellar Astrophysics

Re-evaluating solar irradiance reconstructions: No evidence for large secular trends

Theodosios Chatzistergos, Natalie A. Krivova, Mathew J. Owens et al. (+1 more)

Most current irradiance reconstructions suggest only a modest secular increase in TSI between the 1700 and 1986 activity minima ($<1$ Wm$^{-2}$). However, 2 models, the CHRONOS and Penza et al. (2024; PEA24) models, suggest substantially larger changes of 2.1-5.9 Wm$^{-2}$. Although the two models differ in their architecture, both use cosmogenic isotope records combined with neutron monitor data to describe the long-term irradiance variability. However, cross-calibrating modulation potential reconstructions from cosmogenic isotopes against neutron monitor data remains highly uncertain. We reassess the origin and the magnitude of the large secular trends in the CHRONOS and PEA24 models. We update the CHRONOS and PEA24 models using recent heliospheric modulation potential and open solar flux reconstructions based on geomagnetic data and neutron monitor measurements, which provide a more reliable connection between cosmogenic isotope and neutron monitor records. These allow the secular component of the reconstructions to be extended consistently to the satellite era and compare the resulting TSI reconstructions with direct TSI measurements. We find that the original CHRONOS and PEA24 reconstructions substantially overestimated the secular variability in irradiance. When constrained by direct TSI measurements, CHRONOS yields a TSI increase of about 0.1-0.44 Wm$^{-2}$ between the 1700 and 1986 minima, while PEA24 returns about 0.2-0.25 Wm$^{-2}$. Our analysis indicates that the previously inferred large secular trends arose primarily from improper linking cosmogenic isotope and neutron monitor records, together with issues in the adopted smoothing approach. The updated reconstructions presented here point toward a relatively modest secular increase in TSI since the Maunder Minimum, likely below 1 Wm$^{-2}$, consistent with the majority of current irradiance models.
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All authors Theodosios Chatzistergos, Natalie A. Krivova, Mathew J. Owens, Tatiana A. Egorova

High Energy Astrophysical Phenomena

Black-Hole Spin Measurements from X-ray Reflection Spectroscopy: Quality Criteria and Community Recommendations

Javier A. Garcia, Riley Connors, Laura W. Brenneman et al. (+1 more)

X-ray reflection spectroscopy provides one of the most powerful electromagnetic methods for measuring the dimensionless spin of accreting black holes. It has yielded spin constraints for stellar-mass black holes in X-ray binaries and supermassive black holes in active galactic nuclei, and is central to the science goals of current and future X-ray observatories. However, the technique is subject to observational and modeling systematics, including continuum-reflection degeneracy, limited spectral coverage, unresolved distant reflection or absorption, detector effects, source variability, accretion-state dependence, and assumptions inherent to reflection models. Motivated by discussions at the 2025 Wake Forest workshop *Recent Progress on Black Hole Spin Measurements Across the Electromagnetic and Gravitational Spectra*, we propose a practical framework for evaluating whether published reflection-based spin measurements should be considered robust, provisional, or not assessable from the available information. The framework is built on three principles: **detectability**, requiring an unambiguous relativistic reflection signal; **uniqueness**, requiring that the relativistic component be distinguishable from the continuum, distant reflection, absorption, and instrumental effects; and **robustness**, requiring that the inferred spin remain stable against reasonable changes in model assumptions, data selection, and accretion-state treatment. We translate these principles into assessment criteria, a quality-classification scheme, and a reporting checklist for future studies. Calibration of these criteria through dedicated simulations is outlined here and deferred to a companion paper. Our goal is to establish a reproducible path toward a community-maintained compilation of reliable black hole spin measurements for the high-throughput, high-resolution era of X-ray astronomy.
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All authors Javier A. Garcia, Riley Connors, Laura W. Brenneman, James F. Steiner

Instrumentation and Methods for Astrophysics

Using Muon Rings for the Calibration of the Cherenkov Telescope Array: An Analytical Solution for the Dual-Mirror Telescope Using Vector Geometry

Markus Gaug, Víctor Giráldez-Segalàs and Fiona Redmen

The analysis of ring images produced by muons in Imaging Atmospheric Cherenkov Telescopes (IACTs) provides a powerful and precise method for calibrating the optical throughput of the instrument and monitoring its optical point-spread function. To date, analytical solutions have been derived for single-mirror telescopes with reflectors assumed flat. However, a complete analytical description of the Cherenkov light produced by muons and detected by a dual-mirror telescope - accounting for both the secondary mirror and the camera - has remained elusive, owing to the complexity of the problem. In this work, we derive such a solution using a vector-geometry formalism supported by symbolic manipulation and Taylor expansions performed with the computer algebra system SageMath. We validate the formalism against known analytical solutions in simpler configurations and, for more complex terms, against limiting cases exhibiting the expected physical behavior. The behavior of the full solution is illustrated visually by varying the relevant parameters. The largest effects were found in the shadowing of Cherenkov light produced by inclined muons in dual-mirror telescopes, particularly for the Schwarzschild-Couder Telescope (SCT) design with baffles surrounding the secondary mirror. Deviations of up to 40% are observed relative to previously employed methods. As a by-product, we derive the first-order correction to the maximum emission height of Cherenkov photons emitted by a muon, arising from the curvature of the primary mirror - an effect neglected in previous studies - as well as the impact of coma aberration on the muon rings in single-mirror parabolic telescopes. Our results are directly applicable to muon-based calibration of the Cherenkov Telescope Array Observatory (CTAO).
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High Energy Astrophysical Phenomena

CRESCENDO II: Spectral cosmic rays with improved energy losses and realistic supernova seeding

Daniel Karner, Ludwig M. Böss, Klaus Dolag et al. (+1 more)

Context. Cosmological simulation codes with subgrid models for cosmic rays (CRs) help us better understand their impact on baryonic feedback and non-thermal radiation in galaxies and galaxy clusters. An accurate numerical description requires a spectrally resolved treatment of the CR population, because virtually all transport, acceleration and loss processes depend on energy. Aims. We advance the treatment of CR electrons and protons in the on-the-fly spectral CR solver CRESCENDO in OpenGadget3. Methods. We implement several new energy loss processes for both protons and electrons and improve the computation of their energies and pressures beyond the ultra-relativistic approximation. Moreover, we present a subgrid model for CR seeding by supernova remnants, in which physically motivated spectra are injected at sites of ongoing star formation. Results. We test the newly implemented loss processes and the coupling between CR injection and star formation in idealized setups. We also highlight numerical subtleties, such as the differences arising when hadronic losses are modelled as continuous or catastrophic process, and the advantages of using a flexible spectral cut-off and abandoning the ultra-relativistic approximation. Furthermore, we show that using analytical approximations to compute energy fluxes can cause the slope reconstruction to fail. Conclusions. Future applications of our spectral cosmic-ray model in large-scale, full-physics cosmological simulations will represent an important step towards building a robust and observationally verifiable link between the microphysical and macrophysical aspects of the CR component in the modern paradigm of galaxy evolution.
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All authors Daniel Karner, Ludwig M. Böss, Klaus Dolag, Ildar Khabibullin

Astrophysics of Galaxies

The chemodynamical signature of coherent metal-poor inflow and enriched recycled accretion in the cool circumgalactic medium

Glenn G. Kacprzak, Jerrard Doran, Sameer et al. (+7 more)

The azimuthal and kinematic structure of the CGM is often interpreted as planar accretion and bipolar outflows, yet direct metallicity evidence for this picture remains ambiguous. We combine cloud-by-cloud ionisation modelling with galaxy rotation kinematics for 21 galaxies from the Multiphase Galaxy Halos Survey to investigate how metallicity depends on azimuthal angle and angular momentum. We find that low-ionisation clouds kinematically consistent with disk rotation have ~0.5 dex lower metallicity near the projected major axis ($\Phi<30^\circ$) than at larger azimuthal angles. Major-axis clouds also exhibit higher N(HI), higher density, and reduced non-thermal line broadening compared to clouds at larger azimuthal angles. In contrast, the higher-ionisation phase shows no significant metallicity dependence on azimuthal angle and has lower column densities, lower densities, higher temperatures, and broader line widths than the co-rotating major-axis low-ionisation clouds. These combined metallicity–kinematic–ionisation signatures are consistent with dynamically cold, metal-poor inflow along the disk plane and enriched, more turbulent gas at larger azimuthal angles that likely traces angular-momentum-supported recycled accretion, embedded within a dynamically complex warmer phase. These results show that metallicity and angular momentum are jointly imprinted by the baryon cycle and are both required to uncover the physical origins of CGM gas.
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All authors Glenn G. Kacprzak, Jerrard Doran, Sameer, James Farrington, Jane C. Charlton, Nikole M. Nielsen, Kaustubh R. Gupta, Christopher W. Churchill, Tania M. Barone, Antonia Fernández-Figueroa

High Energy Astrophysical Phenomena

Multiwavelength study of non-thermal emission in the Swift J1834.9-0846/W41 region

Manoel F. Sousa, Rita C. Dos Anjos and Vitor de Souza

We investigate the origin of non-thermal emission from the Swift J1834-0846/W41 region by modeling its broadband spectral energy distribution from radio to TeV energies within leptonic and lepto-hadronic frameworks using Markov Chain Monte Carlo sampling. Motivated by morphological studies of HESS J1834-087 suggesting a two-component TeV structure, we explore a single extended source scenario and a configuration comprising a central point-like component embedded within extended emission. Purely leptonic models are disfavored in both scenarios by unrealistically low magnetic field strengths, whereas lepto-hadronic solutions yield field intensities and non-thermal energy budgets consistent with an evolved supernova remnant undergoing efficient cosmic-ray acceleration. In the two-component scenario, hadronic interactions dominate the extended TeV emission from W41, while the central excess is well described by a leptonic magnetar wind nebula powered by Swift J1834-0846, implying a short initial spin period of $P_0 \lesssim 0.2$ s. Simulated observations with the Cherenkov Telescope Array Observatory show that 30 h exposures will discriminate between the two morphological configurations and extend spectral measurements beyond $\sim$10 TeV.
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Astrophysics of Galaxies

VENUS: an ultra-faint galaxy hosting the metal-poor type II supernova at $z=5.13$ Witnessing the initial metal enrichment with extremely frequent core-collapse supernovae?

Yoshihisa Asada, Seiji Fujimoto, Joseph F. V. Allingham et al. (+50 more)

We present the first characterization of the host galaxy of a recently discovered type IIP SN at $z=5.13$ (SN Eos). SN Eos and its host galaxy are gravitationally lensed and multiply imaged. The total magnification $\mu\sim53$ enables spatially resolving the system, allowing us to localize the core-collapse supernova (CCSN) position and to characterize its local environment within an early galaxy. Our observation reveals that the host is an ultra-faint ($M_{\rm UV}=-14.4\pm0.3$ mag) Lyman-$\alpha$ emitter with a very high equivalent width. The host galaxy also shows very weak [O iii]4959,5007 lines despite an H$\alpha$ line detection ([O iii]5007/H$\beta <0.7$ with case B recombination). Assuming that the weak [O iii] is due to low gas-phase metallicity given the low-metallicity of SN Eos itself, SN Eos plausibly marks the formation and explosion of a metal-poor star in an extremely metal-poor environment ($<1\ \%\ Z_\odot$), facilitating the initial stages of the chemical enrichment of the host. Finding the CCSN in such an ultra-faint galaxy at $z=5.13$ also indicates that the SN rate could be considerably higher in high-$z$, metal-poor environments, potentially implying e.g., a $Z$-dependent IMF, $Z$-dependent massive star explodability, or runaway stellar collisions in dense star clusters. Without lensing, only SN Eos would be detectable and the host would be below the detection limit in any NIRCam surveys ever performed. The Eos host galaxy can thus be representative of the origin of hostless supernovae frequently found in JWST blank field surveys.
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All authors Yoshihisa Asada, Seiji Fujimoto, Joseph F. V. Allingham, David A. Coulter, Conor Larison, Matthew R. Siebert, Gabriel Brammer, Dan Coe, Pratika Dayal, Qinyue Fei, Lukas J. Furtak, Vasily Kokorev, Keiichi Maeda, Richard Pan, Johan Richard, Fengwu Sun, Abdurro'uf, Jacqueline Antwi-Danso, Franz E. Bauer, Marusa Bradac, Larry D. Bradley, Volker Bromm, John Chisholm, Christopher J. Conselice, Christa DeCoursey, Anderas L. Faisst, Brenda Frye, Mauro Gonzalez-Otero, Yuichi Harikane, Tiger Y. Y. Hsiao, Kohei Inayoshi, Yolanda Jimenez-Teja, Anton M. Koekemoer, Kotaro Kohno, Paulo A. A. Lopes, Ray A. Lucas, Georgios E. Magdis, Vladan Markov, Nicholas Martis, Jorryt Matthee, Minami Nakane, Rohan P. Naidu, Gael Noirot, Masami Ouchi, Armin Rest, Massimo Ricotti, Louis-Gregory Strolger, Raffaella Schneider, Francesco Valentino, Eros Vanzella, Hayley Williams, Rogier A. Windhorst, Adi Zitrin

Cosmology and Nongalactic Astrophysics

The plethora of diffuse emission in Abell 2034 as revealed by MeerKAT polarization observations

A. Bonafede, M. Balboni, G.W. Pratt et al. (+15 more)

We present MeerKAT observations of the galaxy cluster Abell 2034, a massive (M_500=5.21 10^14 solar masses) nearby cluster in a merging state. Previous observations at 144 MHz have shown that the cluster exhibits a plethora of diffuse emission, with multiple diffuse sources of uncertain classification because of the lack of spectral and polarimetric observations. MeerKAT multi-frequency observations, centered at 816 MHz and 1.28 GHz, together with archival low-frequency LOFAR observations at 144 MHz have allowed us to shed light on the properties of these sources. The polarization properties and spectral index information let us conclude that the cluster hosts one radio relic, a source with a very steep spectrum, previously classified as candidate relic, and filaments of very steep emission around the tailed radio galaxies identified at low frequencies. The presence of a radio halo is confirmed, and its spectrum shows hints for curvature between 144 MHz ad 1.28 GHz. The polarimetric data in the L-band, together with the model of the gas density derived from X-ray observations are used to constrain the magnetic field in the intracluster medium. We assume a radially symmetric magnetic field model, whose strength declines with the cluster gas density as B(r) ~ n_e(r)^0.5, and normalize its strength within R_500. We find that B_500=1 muG best explains the Faraday depth properties of the cluster, though the detection of sources close to the cluster center would be crucial to discriminate among different values. We conclude that the cluster Abell 2034 shows diffuse emission with complex morphologies that do not follow the historical categories of halos and relics. Deep multi-frequency and polarimetric observations are fundamental to understand their origin.
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All authors A. Bonafede, M. Balboni, G.W. Pratt, I. Bartalucci, L. Rudnick, C. J. Riseley, C. Stuardi, B. Hugo, G. Bernardi, M. Brüggen, G. Brunetti, R. Cassano, F. De Gasperin, F. Gastaldello, K. Knowles, F. Loi, T. Shimwell, R. J. van Weeren

High Energy Astrophysical Phenomena

X-Ray Timing Properties of the Black Hole Candidate IGR J17091-3624 During the 2022 Outburst Onset with AstroSat

Sree Bhattacherjee and Biplob Sarkar

We present the evolution of rapid X-ray timing variability in the black hole X-ray binary IGR J17091-3624 during the initial phase of its 2022 outburst using a ~3-day-long AstroSat observation. Utilizing the high time-resolution capability of the Large Area X-ray Proportional Counter, we perform a comprehensive study of the evolution of Type-C quasi-periodic oscillations (QPOs) throughout the observation. The QPO centroid frequency evolves from 3.30 to 7.78 Hz, accompanied by the broad-band noise characteristics. We further investigate the energy dependence of the fractional rms variability and time lags, finding that the fractional rms exhibits a positive energy dependence, with its amplitude evolving throughout the observation, while the time lags exhibit the soft-lag behavior and evolve with QPO frequency. These findings provide important insights into the evolution of geometry of the inner accretion flow during the onset phase of the 2022 outburst of IGR J17091-3624.
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Earth and Planetary Astrophysics

The exozodi spectral effect: Residual habitable zone dust may bias exoEarth characterization

Miles H. Currie, Christopher C. Stark, Eleonora Alei et al. (+1 more)

All exoplanetary systems are expected to host exozodiacal dust, or exozodi, originating from planetesimals. For many stars, exozodi will likely be the largest source of astrophysical noise in direct observations of terrestrial exoplanets. Nearby Sun-like systems likely have $\gtrsim3$x more habitable zone (HZ) dust than our solar system, which must be removed from direct images and spectra to reveal exoplanet signals. The albedo of this micron-sized dust varies smoothly over VIS – NIR wavelengths, but exozodi can be composed of different materials that can impact its color. If left unsubtracted, exozodiacal light will add cloud-like continuum emission to extracted spectra, potentially biasing characterization studies by reducing the apparent absorption depth of spectral features. To quantify these effects, we simulate exoEarth systems with a range of exozodi densities and compositions, and apply an atmospheric retrieval tool to synthetic Habitable Worlds Observatory (HWO) spectra. We find that exozodi at levels similar to the solar system (i.e., 1 zodi) can reduce the apparent depth of visible wavelength molecular absorption features by up to 50%, an effect that worsens at longer wavelengths. To measure molecular abundances, significant post-processing may be required to remove exozodi to a fractional residual that tightens with dust density. However, targeting a binary detection result for an absorbing species instead relaxes this requirement by an order of magnitude, especially at higher spectral resolution. Understanding and mitigating the effects of exozodi in extracted exoEarth spectra is critical to characterize HZ exoplanet environments with HWO and ultimately to search for signs of habitability and life.
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All authors Miles H. Currie, Christopher C. Stark, Eleonora Alei, Aki Roberge

Earth and Planetary Astrophysics

Helium escaping from the atmosphere of a nearby rocky exoplanet orbiting in a habitable zone

Collin Cherubim, Shreyas Vissapragada, Tim Cunningham et al. (+13 more)

Observations of highly irradiated gas giant exoplanets have shown helium escaping from their atmospheres. There is limited evidence for atmospheres on rocky exoplanets, perhaps because they have already escaped. We report spectroscopic observations of LHS 1140b, a rocky exoplanet that orbits in the habitable zone of a nearby low-mass star. The near-infrared transit spectra show absorption by helium escaping from the planet's atmosphere. Helium absorption is detected in 2024 but not in 2025, indicating time-variable atmospheric escape. We interpret these results as indicating an upper atmosphere dominated by helium and depleted in hydrogen, with other volatile species trapped at lower altitudes, consistent with atmospheric fractionation models. No helium absorption is detected for LHS 1140c, a smaller and more heavily irradiated exoplanet in the same system.
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All authors Collin Cherubim, Shreyas Vissapragada, Tim Cunningham, Annabella G. Meech, David Charbonneau, Robin Wordsworth, Aaron Householder, Johanna Teske, Leonardo A. Dos Santos, Nicole L. Wallack, William Misener, Zifan Lin, Andrew McWilliam, Michael Zhang, Jason A. Dittmann, Mercedes López-Morales

Earth and Planetary Astrophysics

Tidal evolution of packed moon systems around an Earth-mass planet

Alan Briseño, Billy Quarles and Marialis Rosario-Franco

While missions have long targeted terrestrial exoplanets within the habitable zone of their host stars, the number of exomoon candidates is expected to grow as next generation space-based observatories achieve the photometric sensitivity required to detect their transit signals. Constraining the stability limits of tightly packed moon systems is therefore essential for transit searches and predicting the number of moons around terrestrial planets. In our Solar System, only three moons orbit the terrestrial planets, motivating the question of whether Earth-mass exoplanet systems can sustain long-lived, tightly packed satellites. We investigate the stability limits of an Earth-mass planet orbiting a Sun-mass star, where the planet hosts multiple moons. We use the REBOUND N-body integrator along with the tides_spin module in REBOUNDx to assess the stability of tightly packed systems of Luna-, Pluto-, and Ceres-mass moons across a range of tidal dissipation parameters, up to $10^{7}$ dynamical orbits of the innermost moon. We find that an Earth-mass planet can stably host up to two Luna-mass moons, three Pluto-mass moons, or five Ceres-mass moons. Under Earth-like dissipation, the Luna, Pluto, and Ceres packed systems survive within narrow regions of orbital spacing. These results imply that long-lived multi-moon systems around Earth-mass planets are possible but strongly depend on tidal dissipation; for these architectures to exist on billion-year timescales, tides must be weaker than those of the present-day Earth-Moon system.
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High Energy Astrophysical Phenomena

Einstein Probe Fast X-ray Transients Extend the Physical Parameter Space of Relativistic Jets

Connery Chen, Yihan Wang and Bing Zhang

Fast X-ray Transients (FXTs) detected by the Einstein Probe (EP) mission possess exceptionally low spectral peak energies compared to typical long (Type II) GRBs. Some of these extragalactic transients show phenomenological similarities to X-ray flashes (XRFs), but the physical origins of FXTs remain uncertain. In this work, we investigate EP-detected FXTs using various jet structures relevant to Type II GRBs and test the hypothesis that these FXTs belong to the intrinsically same population of known GRBs but viewed at large angles from the jet axis. We apply detectability estimates to evaluate their distribution in the observed E_iso-E_p plane. We find that standard single- and multi-component jet structures can reproduce the energetics of off-axis events such as GRB 170817A and low-luminosity GRBs (llGRBs), while also yielding energetics consistent with XRFs at the lower end of the E_iso-E_p continuum for moderately off-axis observers. However, viewing-angle effects of standard Type II GRBs alone cannot account for the E_p values observed in some energetic FXTs. This tension suggests that EP-detected FXTs are unlikely to be explained solely as classical GRBs viewed off-axis, and may instead probe relativistic explosions in a previously underexplored region of parameter space. In particular, these transients may be associated with lower Lorentz factors, reduced angular momentum in the collapsing core, or alternative jet structures and emission mechanisms. Our results motivate further studies to test these scenarios and constrain the physical properties of FXT progenitors and their outflows.
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Solar and Stellar Astrophysics

Positive superhumps in high mass ratio cataclysmic variables driven by apsidal disk precession

Rebecca G. Martin, Stephen H. Lubow, David Vallet et al. (+1 more)

Previously it has been assumed that a cataclysmic variable (CV) disk can only become eccentric and display superhumps if the 3:1 resonance is located within the disk. This requires the binary mass ratio to be $q=M_2/M_1\lesssim 0.33$, where $M_1$ is the mass of the white dwarf and $M_2$ is the mass of the companion star. However, several systems with higher mass ratios have been observed to exhibit positive superhumps, posing a challenge to this picture. We present the first 3D hydrodynamic simulations to show that eccentricity growth can occur in CV disks even when the resonance radius lies outside the disk. The finite width of the 3:1 resonance extends into the outer parts of the disk and drives eccentricity. While high mass ratio CVs more commonly show negative superhumps, our linear analysis reveals that the direction of apsidal precession is highly sensitive to the disk outer radius and surface density distribution. Smoothed particle hydrodynamic simulations tend to suppress eccentricity gradients and favor prograde precession. These results provide a natural explanation for positive superhumps in high mass ratio CVs and show that disk structure, rather than the resonance location alone, controls the emergence of superhumps.
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All authors Rebecca G. Martin, Stephen H. Lubow, David Vallet, Stephen Lepp

Instrumentation and Methods for Astrophysics

Enhancing WISE Infrared Imaging to Spitzer Resolution Using Deep Learning Super-Resolution

Saeed Rezaee, Shoubaneh Hemmati, Bahram Mobasher et al. (+5 more)

We present a deep-learning framework that performs 4.6x spatial super-resolution from WISE W1 (3.4 micron) toward Spitzer IRAC Ch1 (3.6 micron), and characterize its behavior on the COSMOS field. We train on ~390,000 paired cutouts drawn uniformly within the WISE/Spitzer overlap and report all metrics on a held-out test set of 83,592 cutouts. The framework uses a convolutional neural network trained with a loss function that emphasizes accurate recovery of sources in crowded fields. The model recovers the total flux of the central source in a fixed aperture to a median relative error of 11%, a factor of ~2 better than the interpolation baselines; the gain reaches ~3x on the faintest quartile. The brightness dependence is monotonic: the aperture integrated flux error decreases from 13% on the faintest quartile to 8% on the brightest. At the 3-5 arcsec separations where WISE blends sources that Spitzer separates, the model recovers 35% of the source peaks detectable in the Spitzer truth compared with 9% for interpolation. The characteristic failure mode is oversmoothing of source profiles, which biases integrated flux measurements upward; this pattern is qualitatively similar to that of the interpolation baselines but is quantitatively smaller for the trained model. These results suggest genuine resolution enhancement and source deblending, providing a path toward applying super-resolution across the all-sky area that Spitzer could not cover. An appendix replicates the analysis at W2 -> IRAC Ch2 with consistent results; the trained model and code are publicly available.
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All authors Saeed Rezaee, Shoubaneh Hemmati, Bahram Mobasher, Naveen A. Reddy, Tara Fetherolf, Alexander de la Vega, Negin Moharrami Allafi, Sina Miri

Solar and Stellar Astrophysics

Preferential alignment of Class 0, Class I protostellar disks in multiple systems across nine nearby molecular clouds

Cheng-Han Hsieh, Aleksey Generozov, Stella S. R. Offner et al. (+6 more)

Protostellar disk orientations in multiple systems provide critical insights into the primary mechanisms that govern the formation of multiple-star systems, their subsequent dynamical evolution, and their impact on planet-forming disks. We present a disk alignment study of 512 Class 0, Class I, and flat-spectrum protostars across nine nearby molecular clouds within 500 pc, utilizing data from the CAMPOS and VANDAM surveys. Our sample includes 74 binaries and 31 high-order multiple systems. We find that multiple systems with projected pair separations up to 6000 au exhibit preferential disk alignment with respect to each other across all evolutionary classes, deviating significantly from the random distribution predicted by turbulent fragmentation models. This suggests that the formation of multiple systems cannot be explained by turbulent fragmentation alone. Disk alignment on scales of a few thousand au is also difficult to explain by disk fragmentation as the dominant origin. We further find that the degree of nearest-neighbor disk alignment in higher-order multiples is comparable to that in binaries. Finally, we identify a significant deficit of flat-spectrum protostellar disks in high-order multiple systems as compared to younger Class 0 and Class I phases. The decline is consistent with rapid dynamical evolution, in which most higher-order systems dissolve by the end of the Class I phase.
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All authors Cheng-Han Hsieh, Aleksey Generozov, Stella S. R. Offner, Héctor G. Arce, Jaime E. Pineda, Michael M. Dunham, Diego Mardones, Dominique Segura-Cox, Bethany Grimm

Instrumentation and Methods for Astrophysics

Expanding the SPISEA Stellar Population Synthesis Software to the Substellar Regime

Caitlin Begbie, Rachel Street, Katarzyna Kruszynska et al. (+4 more)

We present an extension of the SPISEA stellar population synthesis framework that adds brown dwarfs to the existing range of stellar mass objects, enabling physically consistent modeling of brown dwarfs within synthetic star clusters. Previous versions of SPISEA included limited substellar support, relying on outdated initial mass functions and incomplete atmospheric and evolutionary coverage below the hydrogen-burning limit. This was addressed through the implementation of a modern substellar initial mass function based on robust observational constraints, the introduction of merged atmospheric grids that smoothly transition between stellar and brown dwarf regimes, and the construction of unified evolutionary tracks spanning the lowest-mass brown dwarf objects through massive stars at solar metallicity. The updated framework was validated by comparing simulated color-magnitude diagrams to observational data from the Pleiades, Upper Scorpius, and M44 clusters using Gaia, UKIDSS, and 2MASS photometry. The new models allow for generation of user-specified isochrones and clusters that reproduce observed stellar behaviors while enabling realistic population synthesis in the brown dwarf regime. This work extends SPISEA's applicability to substellar science cases, including young cluster studies and microlensing simulations, and provides a foundation for future incorporation of planetary-mass objects and non-solar metallicities.
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All authors Caitlin Begbie, Rachel Street, Katarzyna Kruszynska, Jessica Lu, Matthew Hosek Jr., Natasha Abrams, Macy Huston

Cosmology and Nongalactic Astrophysics

Cosmological $\gamma$-$\gamma$ Pair-Production Background

Mika A. Gelowicz, Thomas Siegert, Saurabh Mittal et al. (+10 more)

The origin of positrons is one of the unsolved puzzles in astrophysics as the majority of sources are still unidentified. The Cosmic Photon Background (CPB) is the isotropic radiation spanning the entire electromagnetic spectrum. Interactions of the CPB with itself may pose a promising source of positrons and secondary emission. We calculate the electron-positron pair production rate from the $\gamma$-$\gamma$ pair-production of the CPB with itself for redshifts $z \leq 10$, and determine the annihilation spectrum, Inverse Compton emission, and bremsstrahlung. The CPB is decomposed into a sum of gray body functions, of which each is being evolved according to source type luminosity functions and redshift. We compute the pair-production rate by integrating the angle- and energy-dependent cross section over the evolving CPB. The pairs produced at each redshift are then propagated towards $z=0$, taking into account a cosmological, intergalactic, energy loss function. The photon emission is calculated per redshift and then line-of-sight integrated towards a contribution of the Cosmic Gamma-Ray Background (CGB) today. The resulting pair-production emissivity increases steeply from $z=0$ of about $2 \times 10^{-36}$ to a peak of $1.8 \times 10^{-31}\,\mathrm{e^\pm\,cm^{-3}\,s^{-1}}$ at $z=2.7$, then declines again. This yields a total cosmic pair-production rate on the order of $10^{54}\,\mathrm{e^\pm\,s^{-1}}$ up to redshift $10$. The secondary emission of pairs experiencing Inverse Compton scattering off the CPB results in a sizable contribution to the CGB. The pairs from cosmological $\gamma$-$\gamma$ absorption provide a minimum level of secondary emission which needs to be taken into account for any CGB study. Especially in the range from 1 MeV to 1 GeV, this background can make up 20% of the total CGB emission and may substantially reduce the gap between MeV observations and models.
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All authors Mika A. Gelowicz, Thomas Siegert, Saurabh Mittal, Laura Eisenberger, Dimitris Tsatsis, Niklas C. Bauer, Rudi Reinhardt, Patrik Ehrmann, Manja L. Zimmerer, Hiroki Yoneda, Tomohiko Oka, Tristan Bouchet, Manuel R. H. W. Skalka

Cosmology and Nongalactic Astrophysics

Misalignment production of isotropized vector dark matter?

Chong-Bin Chen

We present dark matter production by the misalignment mechanism of a multi-vector condensate through kinetic coupling during inflation. We impose isotropized background vector fields to release the model from the stringent constraint of anisotropy. However, it turns out that the constraints imposed by non-Gaussianity and isocurvature fluctuations are incompatible with each other, regardless of whether the fluctuations are in the weak-mixing or strong-mixing regime.
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Instrumentation and Methods for Astrophysics

DragonflyPol: Wide-Field Optical Linear Polarimetry with the Dragonfly Telephoto Array (Instrument Description and Commissioning)

Mehrnoosh Tahani, Leo Hollberg, Hiroshi Akitaya et al. (+9 more)

We present DragonflyPol, a wide-field optical linear polarimetry capability implemented on the Dragonfly Telephoto Array. DragonflyPol leverages Dragonfly's modular, multi-lens architecture to obtain simultaneous measurements in four linear polarization orientations ($0^\circ$, $45^\circ$, $90^\circ$, and $135^\circ$) across a $\sim5\,deg^2$ field of view, distributed across 44 polarized lens–detector units. Four additional units serve as unpolarized reference channels. We describe a broad range of science goals enabled by this capability, including magnetic field mapping and tomography, dust grain properties, CMB foreground characterization, and the three-dimensional structure of diffuse interstellar clouds. We integrate Canon polarizers and Baader Sloan $r'$ bandpass filters into the drop-in filter holders of the Canon lenses, and conduct a three-phase laboratory characterization program to select optimal polarimetric components, measure contrast ratios and transmission efficiencies, and determine and mark the transmission axis of each polarizer with sub-degree repeatability. Laboratory measurements across all 44 deployed polarizers yield a mean noise-subtracted contrast ratio of $1228 \pm 104$ and a single-polarizer transmission efficiency of $\sim$33% in the $r'$ band. On-sky commissioning, including twilight flat-field characterization and twilight-sky polarization measurements, confirms throughput stability across polarization groups and successful recovery of the expected Rayleigh scattering signal. DragonflyPol achieved first polarimetric light in September 2025.
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All authors Mehrnoosh Tahani, Leo Hollberg, Hiroshi Akitaya, Jaeyeon Kim, Deborah Lokhorst, Roberto Abraham, Pieter van Dokkum, William P. Bowman, Vishwa Koshene Gamage, Paras Regmi, Yasuo Doi, Koji S. Kawabata

Cosmology and Nongalactic Astrophysics

Charting the expansion of the Universe from z$\sim$0 to z$\sim$14 with HII galaxies

R. Chávez, R. Terlevich, A. L. González-Morán et al. (+14 more)

We present an updated Hubble diagram of giant extragalactic H II regions and H II galaxies spanning the redshift interval $z\sim 0$ to $z\sim 14$, extending the use of the $L(\mathrm{H}\beta)-\sigma$ relation as an independent cosmological probe into the epoch of cosmic dawn. Our sample comprises 243 objects, including local anchor systems with primary distance measurements, previously published low- and intermediate-redshift H II galaxies, recent JWST/NIRSpec observations, and a new subsample of extremely high-redshift H II galaxies observed with JWST and with ALMA+JWST for the highest-redshift cases. We homogenise the measurements across the full sample, applying consistent corrections for instrumental and thermal broadening, extinction, and, where required, the transformation from [O III]-based to Balmer-line velocity dispersions. We model lensing effects of high redshift using a log-normal magnification formalism and infer cosmological parameters via a nested-sampling analysis. The $L-\sigma$ relation remains consistent over the full redshift range, showing no evidence for significant evolution even at the highest redshifts currently accessible. For the joint anchor+H II galaxies sample, under a flat $\Lambda$CDM model, we obtain $h=0.725\pm0.040$ and $\Omega_m=0.308^{+0.043}_{-0.053}$. Allowing a constant dark-energy equation of state yields $w_0=-0.96^{+0.53}_{-0.21}$, while a CPL parametrisation gives $w_0=-0.92^{+0.57}_{-0.34}$ and $w_a=-0.48^{+0.60}_{-1.50}$, all consistent, within the uncertainties, with concordance cosmology. These results demonstrate that H II galaxies offer a viable, fully independent tracer of the expansion history across almost the entire age of the Universe, opening a new avenue for testing $\Lambda$CDM and dark-energy evolution well beyond reionisation.
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All authors R. Chávez, R. Terlevich, A. L. González-Morán, S. Zamora, E. Terlevich, D. Fernández-Arenas, F. Bresolin, M. Plionis, S. Basilakos, R. Amorín, M. Llerena, F. D'Eugenio, Xihan Ji, J. Zavala, J. Rivera, N. Gómez-Cruz, L. Corral-Bustamante

High Energy Astrophysical Phenomena · Cross-listed from hep-ph

Constraining the Coexistence of Primordial Black Holes and Particle Dark Matter with Neutrino Observations

Prolay Chanda, Sagnik Mukherjee and James Unwin

Primordial black holes (PBH) with a uniform mass scale could contribute up to 1% of the gravitationally inferred dark matter relic abundance and remain consistent with observational limits over a large range of masses. In this case, the vast majority of the dark matter relic abundance is comprised of dark matter particles, such as WIMPs or FIMPs. Particle dark matter gravitationally captured around primordial black holes can form dense minispikes in which the annihilation rate is strongly enhanced. In this work, we investigate the constraints on the coexistence of PBHs and particle dark matter from high-energy neutrino observations. Relative to earlier analyses, we refine the treatment of the dark matter halo profile and its redshift evolution. We consider models of freeze-out and freeze-in dark matter, as well as Boltzmann-suppressed freeze-in. We present idealized IceCube event-based sensitivities together with conservative limits obtained by requiring that the predicted extragalactic neutrino intensity not exceed the upper envelope of the measured diffuse flux. We explore the constraints in terms of an idealized model with 100% branching to neutrinos, we also discuss these results within the context fo a motivated gauged U(1)${}_{L_\mu-L_\tau}$ mediator model, emphasizing that a consistent particle-physics completion generally predicts correlated charged-lepton and neutrino final states.
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Earth and Planetary Astrophysics

First planetesimals from DESI DR1: 12 highly metal-rich white dwarfs

Paula Izquierdo, Andrew Swan, Boris T. Gänsicke et al. (+43 more)

Metal-enriched white dwarfs provide a unique insight into the composition of exoplanet interiors. These stars accrete the debris of disrupted planetary bodies, and hence, measuring the stellar parameters and photospheric abundances yields the bulk compositions of the parent bodies. At present, over 1750 debris-accreting white dwarfs are known, but just a few dozen are sufficiently enriched to allow a detailed abundance study. Here we report the analysis of 12 highly metal-enriched white dwarfs observed within the Data Release~1 of the Dark Energy Spectroscopic Instrument (DESI). We characterised their stellar parameters and photospheric metal abundances and we identified between three and ten different elements in their optical spectra, including most of the rock-forming species: O, Mg, Si, Ca and Fe. We conclude that the accreted bodies broadly resemble compositions found within the inner Solar System such as primitive meteorites, processed material or planetary cores. Six of the systems allowed a more thorough analysis: four of the parent bodies are composed of dry rock-forming elements; and two of them of something akin to a water-rich planetesimal. Thus, this study establishes DESI as a potent survey for identifying metal-rich targets, yielding reliable compositions of accreted exoplanetary material.
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All authors Paula Izquierdo, Andrew Swan, Boris T. Gänsicke, Jamie T. Williams, Detlev Koester, Nicola P. Gentile-Fusillo, Christopher J. Manser, Laura K. Rogers, D. Aguado, J. Aguilar, S. Ahlen, C. Allende Prieto, D. Bianchi, D. Brooks, T. Claybaugh, A. de la Macorra, A. Dey, P. Doel, J.E. Forero-Romero, E. Gaztañaga, S. Gontcho A Gontcho, G. Gutiérrez, D. Joyce, T. Kisner, S.E. Koposov, A. Kremin, M. Landriau, L. Le Guillou, T.S. Li, M. Manera, A. Meisner, R. Miquel, J. Moustakas, J. Najita, W.J. Percival, F. Prada, I. Pérez-Ràfols, G. Rossi, E. Sanchez, D. Schlegel, M. Schubnell, D. Sprayberry, G.Tarlé, B.A. Weaver, R. Zhou, H. Zou

Instrumentation and Methods for Astrophysics

COS2035: Extending COS/FUV Operations Through the 2030s

Marc Rafelski, David Sahnow, Christian I. Johnson et al. (+29 more)

The far-ultraviolet (FUV) detector of the Cosmic Origins Spectrograph (COS) accumulates gain sag where photons land, and without continued mitigation this degradation would render the most used modes unusable. To extend COS FUV operations through the 2030s, the COS team developed the COS2035 strategy, which builds on the existing COS2025 rules with four technical breakthroughs and two new usage policies. First, SPLIT-wavecals decouple wavelength calibration from science exposures and open detector real estate above the Pt-Ne lamp light leak. Second, a hybrid lifetime position (LP) architecture allows different gratings to operate at different LPs simultaneously. Third, the LP-infinity framework removes the dependence on the eight-LP limit in the COS flight software, supported by a new table-based APT and TRANS rules architecture. Fourth, a revised gain-sag flagging method evaluates integrated column count loss against the maximum achievable signal-to-noise (S/N) per mode. The two new usage policies cap per-target S/N at the maximum achievable value set by fixed-pattern noise, and limit any single program to 2% of the lifetime at any single LP. With LP7 and LP10 enabled in Cycle 33 and LP11 and LP12 in active commissioning for Cycles 34 and 35, the COS2035 strategy positions the FUV channel for continued high productivity through the 2030s.
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All authors Marc Rafelski, David Sahnow, Christian I. Johnson, Bethan James, Svea Hernandez, John Debes, Beverly Serrano, Kate Davis, Serge Dieterich, Van Dixon, Leonardo Dos Santos, Travis Fischer, Elaine Frazer, David French, Mark Giuliano, Joshua Goldberg, Sten Hasselquist, Jacqueline Hernandez, Nick Indriolo, Mike Kelly, Olivia Lupie, Lauren Miller, Diego Mundo, Anna Payne, Karla Peterson, Rachel Plesha, Kate Rowlands, Julia Roman-Duval, Ravi Sankrit, Debopam Som, Scott Swain, Alan Welty

Astrophysics of Galaxies

Efficient Interstellar Grain Growth from High Sticking Coefficients on Amorphous Carbon Dust

Clarke J. Esmerian, Duncan Bossion, Francois Dulieu et al. (+8 more)

Cosmic dust is the solid phase of the interstellar medium (ISM), classically assumed to be composed of carbonaceous and silicate grains with size distributions spanning $\sim 5~\AA$ to $\sim 1~\mu$m (Weingartner & Draine 2001, Draine & Li 2007, Hensley & Draine 2023). While it constitutes at most order-of-magnitude $\mathbf{1\%}$ of the ISM mass, dust is second only to stars in importance for the observable properties of galaxies (Zavala et al. 2021). Large uncertainties in the efficiency of grain growth obfuscate the relative contribution of the two dominant sources of dust in the Universe: direct production from evolved stars versus gas-phase accretion in the ambient ISM (Feldmann 2015, Esmerian & Gnedin 2022, Esmerian & Gnedin 2024). Advances in supercomputers have only recently allowed us to move beyond simple, idealized predictions of dust grain growth efficiencies (Leitch-Devlin & Williams 1985) with atomistic dynamical calculations (Bossion et al. 2024). We show that small carbon dust grains can grow significantly on timescales much shorter than the age of the universe and, in some ISM phases, comparable to the lifetimes of giant molecular clouds. Specifically, we perform molecular dynamics simulations of an amorphous carbon (a-C) grain surface impacted by gas-phase atoms of cosmologically abundant elements with realistic interstellar conditions, finding high ($\gtrsim 0.2$) sticking coefficients for all non-inert elements at all relevant gas and grain temperatures. We present the results of experiments conducted on similar dust candidate materials that support our theoretical calculations. Our results therefore confirm that the process of gas-phase accretion onto grains is likely an efficient mechanism for the growth of interstellar dust mass on astrophysical timescales, and plausibly central to the evolutionary life-cycle of interstellar grains at all cosmic epochs. (abridged)
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All authors Clarke J. Esmerian, Duncan Bossion, Francois Dulieu, Saoud Baouche, Alexey Potapov, W. M. C. Sameera, Tom J. L. C. Bakx, Susanne Aalto, Kirsten K. Knudsen, Gunnar Nyman, Wouter Vlemmings

High Energy Astrophysical Phenomena

Ultra-long simulations of collisionless relativistic shocks in front-comoving frame: evidence for a steady state and its properties

Mikhail Garasev and Evgeny Derishev

We present a series of unprecedently long 2D3V PIC simulations of unmagnetized relativistic $e^{-}e^{+}$-pair shocks performed in a front-comoving frame. By implementing a moving-wall boundary condition in the downstream together with continuous injection at the upstream boundary, we maintain a fixed simulation domain size, opening the way to perform substantially longer simulations. Our longest runs extend beyond $100000\,\omega_p^{-1}$, exceeding the duration of the previously published simulations by a factor of several. Across a diverse set of simulations – varying upstream/downstream lengths, transverse sizes, and particle-per-cell counts – we find strong evidence that the shock approaches an asymptotic, time-independent state. In the downstream region, the steady state depends only on the upstream temperature at the injection boundary and does not depend on a particular numerical realization. The upstream precursor evolves slower and retains a dependence on the simulation's upstream length, that may be of minor observational consequence, since radiation from astrophysical shocks predominantly originates from the downstream region. We also find that Fermi-type acceleration is limited in energy and a true power-law tail never forms. Another important finding is that the downstream magnetic field has a soliton-like structure, where individual magnetic domains evolve independently, each comprising a compact, highly magnetized core embedded within an extended, weakly magnetized region. The magnetic-field distribution around the centers of these spots has approximately Lorentzian profile.
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Earth and Planetary Astrophysics

Hierarchical Three-Body Problem at High Eccentricities = Simple Pendulum, IV: Octupole for Librating Kozai-Lidov Cycles

Ygal Y. Klein

We solve analytically the long-term octupole evolution of librating Kozai-Lidov cycles - those with a negative Kozai constant, in which the argument of pericenter librates - in the double-averaged restricted hierarchical three-body problem. Librating cycles reach extreme eccentricities when the normal component of the orbital angular momentum vanishes, just as rotating cycles do, but their slow dynamics was left unsolved: as noted by Katz, Dong & Malhotra (2011), the azimuth of the eccentricity vector jumps by half a turn every cycle, so the leading-order octupole kick alternates in sign and cancels pairwise. We show that the surviving dynamics, at second order in the octupole strength, is a simple pendulum with explicit coefficients. The pendulum predicts slow oscillations of the normal angular momentum with amplitude linear in the octupole strength, evolving on a timescale of order the secular timescale divided by the octupole strength, together with an explicit criterion for orbital flips. At octupole strengths typical of hierarchical triples, these amplitudes are comparable to - and in part of the librating window can exceed - those of rotating cycles, provided one waits the correspondingly longer timescale. The analytic model agrees with numerical integrations of the double-averaged equations across the librating window, for octupole strengths typical of the hierarchical triples in which the eccentric Kozai-Lidov effect is studied - from hot-Jupiter formation to gravitational-wave sources.
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Earth and Planetary Astrophysics

The Expected Yield of Venus Zone Terrestrial Planets from PLATO

Stephen R. Kane, Emma L. Miles, Colby M. Ostberg et al. (+2 more)

The characterization of terrestrial exoplanets and the conditions that lead to divergent climate outcomes is a primary goal of exoplanetary science. The Venus Zone (VZ) provides a framework for identifying planets that may have experienced runaway greenhouse processes similar to Venus, and the statistical properties of such planets bear directly on models of planetary habitability. Here we present a quantitative estimate of the expected yield of VZ terrestrial planets from ESA's PLATO (PLAnetary Transits and Oscillations of stars) mission. We combine the predicted PLATO planet yield for Earth-size ($0.8$–$1.25~R_\oplus$) and super-Earth ($1.25$–$2.0~R_\oplus$) planets with empirical occurrence rates for VZ terrestrial planets derived from Kepler data. Under conservative assumptions, we estimate that PLATO will detect $\sim$170–280 VZ terrestrial planets ($0.8$–$2.0~R_\oplus$), including $\sim$40–80 Earth-size ($0.8$–$1.25~R_\oplus$) planets, during a nominal 4-year mission. For the bright P1 sample ($V \leq 11$), we estimate $\sim$50–85 terrestrial and $\sim$13–22 Earth-size VZ detections, enabling radial velocity mass determination and atmospheric characterization of the most favorable targets with JWST and future facilities. We discuss the implications of this yield for comparative studies of Earth-Venus divergence, synergies with the DAVINCI, VERITAS, and EnVision missions to Venus, and the role of PLATO in advancing our understanding of the runaway greenhouse boundary.
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All authors Stephen R. Kane, Emma L. Miles, Colby M. Ostberg, Erika Kohler, James B. Garvin