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Physics Astrophysics

astro-ph Watch Astrophysics

Friday 4 September

Cosmology and Nongalactic Astrophysics

Exploring the dark sector through galaxy dynamics in clusters

Andrea Biviano, Lorenzo Pizzuti and Antonaldo Diaferio

Galaxy clusters are among the most powerful laboratories to probe fundamental physics, from the formation of cosmic structures to the nature of dark matter, dark energy, and gravity. Realizing their full potential requires accurate and unbiased determinations of their mass profiles, a longstanding challenge in cluster cosmology. In this context, the kinematics of member galaxies in clusters has become a key tool to reconstruct the mass distribution and to investigate the dynamical properties of clusters. The advent of large spectroscopic datasets has enabled the application of increasingly sophisticated models and robust techniques, which make kinematic analyses competitive with other probes of cluster dynamics. In this review, we provide a comprehensive overview of cluster kinematics, covering the main methods to infer dynamical masses and mass profiles, their physical assumptions, and the impact of systematics such as deviation from dynamical equilibrium, triaxiality, and substructures. We discuss the complementarity with other techniques to investigate the structure of clusters and highlight recent applications to tests cosmological models. We focus in particular on the role of kinematical studies in constraining the dark sector (dark matter and dark energy) and in providing novel insights into the behavior of gravity at Mpc scales. Finally, we outline current limitations and future prospects, emphasizing that the combination of improved modeling and forthcoming spectroscopic surveys will establish cluster kinematics as a fundamental probe in the era of precision cosmology.
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Earth and Planetary Astrophysics

Two extremely irradiated volatile-rich sub-Neptunes with companions in the TOI-426 and TOI-1839 systems: Insights into arrival and survival near the lower edge of the Neptunian desert

A. Castro-González, O. Barragán, D. J. Armstrong et al. (+26 more)

Using TESS photometry and 147 HARPS radial velocities, we confirm two extremely irradiated, volatile-rich sub-Neptunes near the lower edge of the Neptunian desert: TOI-426 b and TOI-1839 b, orbiting the solar-type stars HD 34390 and TYC 304-865-1. We modelled stellar activity with shared-timescale and multidimensional Gaussian processes. The planets have orbital periods of approximately 1.32 and 1.42 days, radii of $2.19\pm0.09$ and $2.27\pm0.10$ Earth radii, and masses of $6.7\pm1.8$ and $7.10\pm0.78$ Earth masses, respectively. They receive approximately 1700 and 1050 times Earth's irradiation, yet their densities require substantial volatile content. We also detect a transiting sub-Neptune, TOI-1839 c, at approximately 4.02 days and a giant companion, TOI-426 c, with a period of $235.8^{+9.2}_{-8.5}$ days and a minimum mass of $444^{+18}_{-17}$ Earth masses, assuming a circular orbit. Interior-structure and atmospheric-escape models yield mass-loss timescales of 1-100 Myr for hydrogen/helium envelopes, compared with 100-1000 Gyr for water-dominated envelopes, favouring a steam-world interpretation for all three transiting planets. A population analysis reveals a striking excess of detected outer giant companions to low-mass sub-Neptunes near the desert edge, where high-eccentricity tidal migration is expected to circularize surviving planets: 36% (9/25) within the tidal survival band versus 6% (9/148) outside it (Fisher exact test $p=1.4\times10^{-4}$). This excess is robust to changes in sample selection and companion definitions. The survival of these volatile-rich planets challenges a boundary set solely by evaporation of primordial hydrogen/helium envelopes, while the companion excess supports an important role for high-eccentricity tidal migration in shaping the lower desert edge.
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All authors A. Castro-González, O. Barragán, D. J. Armstrong, A. Aguichine, V. Bourrier, D. Ehrenreich, E. X. Tao, J. Lillo-Box, M. R. Standing, S. G. Sousa, E. Delgado-Mena, A. Moya, V. Adibekyan, M. Lendl, C. Hellier, S. B. Howell, E. Furlan, C. Ziegler, A. C. M. Correia, K. Cui, P. Figueira, J. M. Jenkins, M. A. Fetzner Keniger, B. Merín, A. Osborn, L. Parc, F. Pepe, P. J. Wheatley, J. N. Winn

Cosmology and Nongalactic Astrophysics

Tracing the Cosmic Origins: Machine Learning Reconstruction of the Primordial Density Field from EoR Observations

Anchal Saxena, P. Daniel Meerburg, Guochao Sun et al. (+2 more)

Reconstructing the initial conditions of the Universe from late-time tracers would unlock cosmological information buried by non-linear structure formation and astrophysics. We reconstruct the initial density field at $z\sim300$ from simulated 21-cm and CO(1-0) line-intensity maps at $z\sim8$ generated with LIMFAST. Using a three-dimensional U-Net, we reconstruct the initial conditions and evaluate its impact on cosmological parameter constraints. The two tracers probe complementary environments: 21-cm emission traces neutral, low-density regions of the intergalactic medium, while CO traces overdense, star-forming regions. To emulate realistic observations, we model instrumental effects for SKA1-Low- and COMAP-ERA-like surveys, including finite angular resolution and thermal noise. We assess reconstruction performance through the cross-correlation coefficient between reconstructed and true initial density fields, $|C(k)|$. In the noiseless case, combining both tracers delivers the most accurate recovery across ionisation states, with $|C(k)| \gtrsim$ 0.90 for $k \lesssim$ 0.75 Mpc$^{-1}$. With observational effects, small-scale information is degraded, but combining tracers still achieves $|C(k)| \gtrsim$ 0.70 for $k \lesssim$ 0.3 Mpc$^{-1}$. To quantify information gain, we perform simulation-based inference of cosmological parameters from power-spectrum summaries before and after reconstruction. In both noiseless and noisy settings, reconstruction tightens parameter constraints: uncertainties on $\sigma_8$ and $n_{\rm s}$ improve by $\sim2\times$, with smaller but consistent gains for other parameters. This is further confirmed using Kullback-Leibler divergence diagnostics for an ensemble of observations. These results indicate that joint analysis of future 21-cm and CO surveys, combined with such reconstruction, can partially recover otherwise inaccessible cosmological information.
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All authors Anchal Saxena, P. Daniel Meerburg, Guochao Sun, Tzu-Ching Chang, Lluís Mas-Ribas

Cosmology and Nongalactic Astrophysics

Early against Late: A contrast on dark energy in the light of DESI DR2

Miguel A. Zapata, Karim Carrion and Gabriela Garcia-Arroyo

Recent findings from Dark Energy Spectroscopic Instrument (DESI) Baryon Acoustic Oscillation (BAO) measurements, combined with Type Ia supernovae and Cosmic Microwave Background (CMB) data, suggest potential parameter-level deviations from $\Lambda\text{CDM}$. However, parameter exclusions omit prior-volume penalties, whereas Bayesian evidence uncovers a stark dichotomy between early- and late-time dynamics. To quantify this effect, we perform a Bayesian model comparison that explicitly accounts for the cosmological epoch of dark energy dynamics, contrasting two schemes acting in opposite epochs of cosmic history: pre-recombination Early Dark Energy (EDE) and late-time Chevallier–Polarski–Linder (CPL), both measured against a baseline $\Lambda$CDM. We validate the learned harmonic-mean estimator against UltraNest (at background level) before applying it to the CMB analysis. Background-only data already disfavor both extensions, yielding {$\ln B_{\Lambda\text{CDM},\text{EDE}} = 1.48 \pm 0.18$ and $\ln B_{\Lambda\text{CDM},\text{CPL}} = 2.36 \pm 0.24$}. Including CMB sharpens this result: {EDE is very strongly rejected ($\ln B_{\Lambda\text{CDM},\text{EDE}} \approx 12.61 \pm 0.17$)} with its early-time fraction constrained to $10^3\,\Omega_e^{\rm EDE} = 2.0^{+0.6}_{-1.0}$, whereas CPL remains only mildly disfavored ($\ln B_{\Lambda\text{CDM},\text{CPL}} \approx 2.34 \pm 0.18$), even though 2D parameter posteriors for both models display a multi-$\sigma$ deviation from $\Lambda\text{CDM}$. Thus, Bayesian evidence weakens reported preferences for dark energy dynamics, with the impact depending on the cosmic epoch involved, confirmed by our functional reconstructions of $w_{\rm de}(z)$ and $\Omega_{\rm de}(z)$ from posterior samples.
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Solar and Stellar Astrophysics

Metallicity dependence of Wolf-Rayet binaries using detailed binary models: An absence of long-period systems at low metallicity

Max M. Briel, Eirini Kasdagli, Tassos Fragos et al. (+6 more)

Observations of Wolf-Rayet (WR) stars in binaries in the SMC and LMC suggest a preference for short period ($P\lesssim30$ days) orbits, with an apparent absence of WRs in long-period systems. The Galactic population does extend to longer periods but shows a deficit in long-period WR binaries compared to their progenitors, the O-star population. Across these populations a nearly constant binary fraction has been observed. We aim to characterize the population of WR binaries across a range of metallicity and determine the metallicity dependence of the formation of these systems, specifically focusing on the period distribution. We use detailed binary evolution models from POSYDON to predict the population of WR binaries at 0.01, 0.1, 0.2, 0.45, and $1Z_\odot$, analyzing the resulting period distribution and formation channels, while comparing them against the observed population in the SMC, LMC, and Milky Way. We find that the absence of wider WR binaries in the SMC, and potentially in the LMC, can be explained by stable, Case-B mass transfer only partially stripping the donor star, combined with WR winds at low metallicity being insufficiently strong to strip the remaining envelope. As a result, the long-period peak from Case-B mass transfer, present at Zsun, disappears at low metallicity. We additionally find that stable mass transfer (SMT) produces a short-period peak through Case-A mass transfer (P~5-10 days) that closely matches observations across metallicity. Furthermore, SMT and non-interacting systems are the dominant formation channels of WR binaries at all metallicities, with their relative contribution showing no metallicity dependence. This result implies that the SMT channel has the same metallicity-dependence as isolated WR formation. At the same time, we find that common envelope evolution primarily produces short-period ($P<1$ day) WR binaries with black-hole companions.
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All authors Max M. Briel, Eirini Kasdagli, Tassos Fragos, Tomer Shenar, Jeff J. Andrews, Denzel Goh, Abhishek Chattaraj, Seth Gossage, Philipp Srivastava

Earth and Planetary Astrophysics

Ion abundances in the plasma tail of 3I/ATLAS show that it is N2-rich

Lea Ferellec, Cyrielle Opitom and Colin Snodgrass

Interstellar objects allow us to compare the early planetary formation process in the Solar System and around other stars. The second and third interstellar objects, 2I/Borisov and 3I/ATLAS, showed visible signs of activity, making it possible to assess their composition via spectroscopic analysis of their gas coma. While neutral volatiles surrounding comets are easily probed by common spectrographs, ion emissions emanate mostly from the tail, making them easier to detect with integral-field units. We present WHT/WEAVE-LIFU observations of 3I/ATLAS, performed post-perihelion on 2025 November 30 and 2025 December 02. We simultaneously detect the ions N2+, CO+, CO2+, H2O+ and CH+ located in an anti-solar tail. Using common fluorescence factors, we determine abundance ratios of these species in the tail. In particular, the N2+/CO+ ratio allows us to constrain the lower-limit N2/CO>0.023+/-0.001, indicating that 3I/ATLAS is N2-rich compared to Solar System comets, a property which can be linked to cold formation conditions. Abundance ratios between other ions cannot directly be used to constrain abundances of neutrals but seem consistent with the fact that 3I/ATLAS is enriched in hypervolatiles. We also investigate whether these ratios vary along the tail, and only detect a marginal decrease of CH+ with cometocentric distance.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Fast Bayesian Inference for Long-Duration Gravitational-Wave Signals in 3G detectors

Anand S. Sengupta

Third-generation (3G) gravitational-wave detectors will observe binary-neutron-star inspirals for nearly a day, so Earth's rotation becomes part of the signal rather than a negligible correction. This destroys the usual separation between intrinsic and extrinsic parameters and creates a major computational bottleneck for Bayesian inference. We show that the exact five-harmonic Jaranowski-Krolak-Schutz (JKS) decomposition restores the separation of the rotating antenna amplitude response from the computationally expensive intrinsic waveform calculations. By sampling the intrinsic waveform on a frequency grid set by its phase curvature and then applying error-controlled relative binning, likelihood evaluations for a 21.3-h signal are accelerated by O(10^4), making day-long 3G signal inference practical.
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Earth and Planetary Astrophysics

Dust Substructures and Line Perturbations driven by a Forming Planet in J16120

Anibal Sierra, Andrés F. Izquierdo, Paola Pinilla et al. (+18 more)

Hints of planet formation have been independently reported within the gap of the disc around 2MASS J16120668-301027 from millimetre continuum, infrared, and H-alpha observations. In this work, we present new evidence for ongoing planet formation based on Atacama Large Millimeter/submillimeter Array (ALMA) Band 7 observations, detecting 0.87 mm dust continuum emission together with 12CO (J=3-2) and 13CO (J=3-2) line emission. Visibility modelling of the continuum data reveals an inner disc and two dust rings peaking at 23 and 75 au. The continuum morphology is better reproduced by an eccentric disc model (e approximately 0.1) than by an axisymmetric disc. We further investigate the gas kinematics through modelling of the 12CO channel maps. The residual line-width map shows a localised increase in velocity dispersion at the position of a previously reported circumplanetary disc candidate (deprojected radius approximately 32 au, position angle approximately 170 degrees) and along its orbit. This signal is spatially coincident with kink-like features and a transition from sub-Keplerian to super-Keplerian velocities. In addition, the velocity residual map exhibits an arc-like structure extending outward from the planet candidate, while the gas kinematics, despite substantial uncertainties, is consistent with inflow towards the candidate's orbital radius. The observed increase in velocity dispersion agrees with predictions from planet-disc interaction simulations, which produce enhanced turbulence both at the planet location and along its orbital path. Taken together, the continuum morphology and gas kinematic signatures provide compelling new evidence for ongoing planet formation within the disc gap.
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All authors Anibal Sierra, Andrés F. Izquierdo, Paola Pinilla, Kan Chen, Myriam Benisty, Laura Pérez, Teresa Paneque-Carreño, Carolina Agurto-Gangas, Jaehan Bae, John Carpenter, Luca Cieza, Dingshan Deng, Stefano Facchini, Camilo González-Ruilova, Nicolás Kurtovic, Aleksandra Kuznetsova, Carlo F. Manara, James Miley, Álvaro Ribas, Giovanni Rosotti, Miguel Vioque

High Energy Astrophysical Phenomena

Electromagnetic alignment and jet precession around supermassive black holes: Quasi-periodic oscillations in tidal disruption events

Pau Amaro-Seoane, Leif Lui, Alejandro Torres-Orjuela et al. (+1 more)

We evaluate quasi-periodic oscillations and jet formation in tidal disruption events using the covariant formulation of electromagnetic angular-momentum transfer. General-relativistic frame-dragging tears apart misaligned transient accretion flows, forming an isolated inner mini-disk. The accumulation of magnetic flux on the event horizon powers a relativistic jet via the Blandford-Znajek mechanism. Because the magnetic field anchors to the precessing mini-disk, the jet axis rotates, generating geometric modulations in the observed X-ray and radio fluxes. To ensure physical consistency with the force-free magnetosphere required to launch a Blandford-Znajek jet, we model the electromagnetic back-reaction using a split-monopole magnetic field topology. By performing a small-spin expansion of the Noether current density over the event horizon, we derive a closed-form analytical reaction torque exerted by the electromagnetic field on the accretion plasma. We evaluate the resulting kinematics to show that the electromagnetic back-reaction induces a retrograde precession of the mini-disk, coupling with the prograde Lense-Thirring precession to dictate the global oscillation frequency. We formulate explicit predictions for observable transient signals and predict a monotonic attenuation of the peak-to-trough flux ratio as the mini-disk aligns, as well as a specific frequency drift signature characterized by an initial lengthening followed by an asymptotic shortening of the time interval between consecutive flares. We establish an analytical mechanism where magnetic flux depletion stalls alignment, predicting a constant residual modulation amplitude at late times. We formulate a methodology to extract the black hole spin and the magnetic flux density directly from the temporal derivatives of this predicted frequency drift, operating independently of spectral continuum fitting.
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All authors Pau Amaro-Seoane, Leif Lui, Alejandro Torres-Orjuela, Xian Chen

Earth and Planetary Astrophysics

Contrasting C/O ratios in Uranus and Neptune from disequilibrium chemistry: A clue to distinct evolutionary pathways?

T. Briand, V. Hue, O. Mousis et al. (+4 more)

The formation of Uranus and Neptune remains poorly constrained largely due to uncertain deep elemental abundances. Carbon monoxide (CO), a disequilibrium species in the upper troposphere, provides an indirect constraint on the deep oxygen abundance. We investigate the deep O/H and C/O ratios of the ice giants and their formation history by accounting for meridional variations in atmospheric structure and uncertainties in chemical kinetics. We extended a 1D thermochemical and diffusion model into a pseudo-2D model by including latitudinal variations in key model parameters. The O/H ratio was inferred by matching the modeled upper-tropospheric CO mole fractions to observations, and combined with the deep carbon abundance to derive the C/O ratio. For Uranus, varying tropospheric methane alone yielded O/H $\sim [47-57] \times$ protosolar, whereas allowing $K_{zz}$ to vary expanded the range to O/H $\sim [62-177] \times$ protosolar. For Neptune, the corresponding ranges are O/H $\sim [182-215] \times$ protosolar and O/H $\sim [222-342] \times$ protosolar, respectively, supporting lower oxygen enrichment in Uranus than Neptune. Chemical-network uncertainties have a more modest effect, amounting to at most $\sim 10\%$ of the retrieved oxygen ranges, comparable to the uncertainty associated with the measured CO abundance on Neptune, but larger on Uranus. We computed C/O latitudinal ranges and found C/O $\sim [0.06-0.52]$ on Uranus and $\sim [0.02-0.12]$ on Neptune. Comparison with a protoplanetary disk model suggests different formation or evolutionary pathways for the two planets. Our results highlight the dominant role of vertical mixing in constraining deep oxygen abundance and the importance of accounting for meridional variability and chemical uncertainties. This work also provides a framework for selecting the entry latitude of a future Uranus Orbiter and Probe mission.
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All authors T. Briand, V. Hue, O. Mousis, T. Cavalié, T. Benest Couzinou, A. Schneeberger, M. D. Hofstadter

Cosmology and Nongalactic Astrophysics

Supernovae Unite: Host-Galaxy Mass Measurements of Type Ia Supernovae and Their Impact on Cosmology

J. Lee, R. Camilleri, T. M. Davis et al. (+22 more)

Current consensus suggests that Type Ia supernova (SN Ia) brightnesses post light-curve standardization correlate with their host-galaxy stellar masses, which must be accounted for to obtain accurate cosmological constraints. For example, Vincenzi et al. (2025) showed that different host-galaxy stellar mass measurements for the same dataset produce redshift-dependent differences of order $\sim 0.01$ mag, large enough to appreciably shift cosmological constraints. We present internally consistent host-galaxy stellar masses remeasured using aperture photometry and spectral energy distribution (SED) fitting for SN-Unite, which combines the spectroscopic Pantheon+ and the photometric Dark Energy Survey five-year (DES-SN5YR) samples into the largest SN Ia cosmology sample to date, with 2884 likely SNe Ia. We find that photometry and SED fitting choices shift SN-Unite Flat$w$CDM parameters well below statistical uncertainties. Our stellar masses differ from the Pantheon+ data release partly due to a redshift-dependent internal inconsistency within Pantheon+, while remaining largely consistent with the DES-SN5YR (DES-Dovekie) data release. When the Pantheon+ subsample of SN-Unite is combined with Baryon Acoustic Oscillations (BAO) and Cosmic Microwave Background (CMB) measurements, the significance for time-evolving dark energy increases from 3.4$\sigma$ to 4.0$\sigma$ based on the maximum a posteriori when our newly derived host-galaxy stellar masses replace the Pantheon+ data-release host-galaxy stellar masses, while DES-Dovekie remains virtually unchanged, consistent with the findings of Hoyt et al. (2026). By remeasuring the host-galaxy stellar masses using a consistent framework throughout the whole sample, we improve the robustness of the SN-Unite cosmological constraints against systematic differences in host-galaxy stellar mass measurements.
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All authors J. Lee, R. Camilleri, T. M. Davis, D. Rubin, K. Bechtol, L. Galbany, M. Sako, M. Sullivan, T. E. Müller-Bravo, D. Scolnic, M. Vincenzi, D. Brout, C. Lidman, A. Möller, P. Shah, M. Acevedo, P. Armstrong, B. A. Bassett, R. C. Chen, H. T. Diehl, J. Frieman, K. Grech, B. Popovic, B. O. Sánchez, B. E. Tucker

2609.05321 · 4 Sep · 25 pages, 10 figures. Companion paper to Supernovae Unite: Combining Pantheon+ and DES-SN5YR. The host-galaxy stellar mass measurements and photometry will be publicly available upon acceptance of the paper. V2: For our Youtube Cosmology Talks, see https://www.youtube.com/watch?v=KT-j65gRnOQ. Removed inactive datalinks and fixed MAP significance. Submitted to the Astrophysical Journal

Abstract PDF $GLXY ×8$SNOV ×3$RDSH ×2$CSMC ×1 +1

Earth and Planetary Astrophysics

Evidence for LP 890-9d via Transit Timing Variations

Kevin B. Stevenson, Guangwei Fu, Kristin S. Sotzen et al. (+10 more)

LP 890-9, also known as SPECULOOS-2 and TOI-4306, is a nearby late-M dwarf hosting two confirmed transiting rocky exoplanets. We analyze 20 JWST/NIRSpec PRISM transits of LP 890-9b and LP 890-9c obtained as part of GO program 7073 and detect statistically significant transit timing variations (TTVs), with peak-to-peak amplitudes of ~17 s and ~35 s, respectively. Using analytic linear TTV theory, we find that the known two-planet configuration cannot reproduce the measured TTV amplitudes or super-period, whereas three-planet models provide substantially better fits. The best-fit configuration places the candidate third planet, LP 890-9d, between planets b and c, with an orbital period of ~4.4 days; however, the current data do not uniquely determine its orbital architecture, and periods spanning 4.0-6.9 days remain plausible. TESS is insensitive to transits of LP 890-9d and we find no evidence for the candidate in JWST observations, although the phase coverage (ranging from ~50% to ~80%) depends strongly on the candidate orbital period. Additional high-precision transit observations of LP 890-9b and LP 890-9c are needed to refine their TTV solutions and further constrain the orbital properties of the third planet.
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All authors Kevin B. Stevenson, Guangwei Fu, Kristin S. Sotzen, E. M. May, Larissa Palethorpe, Jacob Lustig-Yaeger, Ted M. Johnson, Eric Agol, Katherine A. Bennett, Carlos Gascón, David K. Sing, Jeff A. Valenti, Hannah R. Wakeford

Earth and Planetary Astrophysics

JWST Excludes Exomoons Down to 0.1 Earth Radii Around a Rocky, Temperate Exoplanet

David Kipping

To date, even with JWST, it has not been possible to test for exomoons as small as the Moon. Only two reported searches for exomoons around bound planets have been attempted with JWST, both of which relied on a single JWST transit. We suggest that the below expectation sensitivity to date is, in part, a product of the considerable intrinsic flexibility of the planet+moon transit model when confronted with a single event, and the presence of unanticipated systematic noise. To test this, we present a search around the rocky, temperate-zone exoplanet LP 890-9c using twelve JWST transits. We find no evidence for an exomoon but exclude $0.1R_{\oplus}$ moons to 95% confidence across the entire Hill region, representing by far the most sensitive search to date. Our limits exclude analogs to many real Solar System moons, such as Europa, Rhea and Umbriel. However, we emphasize that the close-in orbit of LP 890-9c (0.04au) would make any moons larger than ${\sim}0.1R_{\oplus}$ unlikely to survive for many Gyr due to tides. Regardless, our study firmly establishes that JWST can indeed probe down to remarkably small moons. Further, we find that even a single transit can deliver impressive limits, with the exception of one epoch that is contaminated by red noise. However, by pairing it with just one cleaner epoch, the sensitivity recovers to a level indistinguishable from any other pairing, which bodes well for a potential second JWST transit of Kepler-167e.
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Astrophysics of Galaxies

Rapid quenching and early gas depletion in the core of a galaxy protocluster at z=2.2

C. D'Eugenio, H. Dannerbauer, A. Naufal et al. (+6 more)

Understanding how galaxy evolution is affected in forming high-z overdensities is a major open question in modern astrophysics. Here, we present the average properties of the quiescent galaxy population recently identified in the core of the Spiderweb protocluster at z = 2.16. By stacking observations from the Hubble Space Telescope (HST; F160W imaging and G141 grism spectroscopy), the James Webb Space Telescope (JWST; PaBeta narrowband imaging), and the Atacama Large Millimeter/submillimeter Array (ALMA; 1.2 mm dust continuum imaging), we constrained their ensemble star formation history (SFH), residual dust-obscured star formation, and cold gas mass, respectively. The inferred average SFH indicates steady stellar mass growth, with progenitor SFRs consistent with those of massive Halpha emitters (HAEs) in the same structure. This is followed by rapid quenching, on average 500 Myr prior to observation. No significant age differences are found between active galactic nucleus (AGN) hosts and non-AGN systems. We find weak PaBeta emission for 80% of the sample, yet with dust-obscured star formation rates consistent with quiescence in all but one source (ID 443) excluded from the sample. Our galaxies remain individually and globally undetected in the dust continuum, yielding an average gas fraction fgas= Mmol/Mstar<7%, consistent with previously reported gas depletion trends with stellar mass observed in neighboring HAEs. We thus find the Spiderweb protocluster to host a sizable population of gas-depleted, massive quenched galaxies in its core, likely descending from main-sequence galaxy progenitors and building the first elements of the red sequence in this high-z forming cluster.
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All authors C. D'Eugenio, H. Dannerbauer, A. Naufal, J. M. Pérez-Martínez, Y. Koyama, P. G. Pérez-González, Y. H. Zhang, T. Kodama, K. Daikuhara

Solar and Stellar Astrophysics

ROCKETS I: Investigating the Impact of the Rocket Effect on Two Nearby Young Open Clusters Encased in Infrared Bubbles

R. Arun, G. Maheswar, Annapurni Subramaniam et al. (+5 more)

We introduce ROCKETS (Rocket-driven Cluster Kinematics & Triggered Star-formation), a Gaia based programme investigating kinematic fingerprints of stellar feedback or rocket effect in young star forming regions. We analyse two young clusters with O-type stars enclosed by mid-infrared bubbles, Collinder 69 and IC 1396 as a methodological demonstration on two nearby benchmark regions. Co-moving candidates are selected within an astrometric ellipse defined by the median and median absolute deviation of Class I/II YSOs with Gaia data. For each star, we compute a relative proper-motion angle (RPMA) relative to the ionising source. In both regions the RPMA distribution shows a strong excess at RPMA $<15^{\circ}$, corresponding to sources moving away from the respective ionising sources. We quantify this using the Rocket Effect Index (REI), finding $\mathrm{REI}\simeq 1.1$ for Collinder 69 and $\mathrm{REI}\simeq 1.7$ for IC 1396. When considering only Class I/II YSOs, the REI of both regions increases to $\mathrm{REI}\gtrsim 10$. Velocity-structure analysis of the sample shows that the RPMA $<15^\circ$ subset has stronger positive pairwise expansion than the full co-moving population, providing additional support for the rocket effect. The outward-moving stars are not uniformly distributed; instead, their position angles are strongly anisotropic and preferentially aligned towards the bright-rimmed clouds. Gaia colour-magnitude diagrams show no strong age offset between sources moving outward and literature cluster members. The observed kinematic signatures support feedback-driven acceleration of gas and triggered star formation preferentially towards higher density regions of expanding bubbles due to the rocket effect.
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All authors R. Arun, G. Maheswar, Annapurni Subramaniam, Piyali Saha, T.P. Sudheesh, B. Shridharan, Blesson Mathew, Akhil Krishna R

Solar and Stellar Astrophysics

Energy Partitioning at the Termination Shock

Judit Szente, Bart van der Holst, Gabor Toth et al. (+1 more)

We show new results of a global 3D magnetohydrodynamic (MHD) simulation of the Boston University outer heliosphere model where we used a newly developed approach that distributes the non-adiabatic shock heating among the cold protons, electrons, and pickup-ions (PUIs), while maintaining total energy conservation of all ions (cold protons and PUIs) and electrons. In our previous simulations ( E.S. Bair et al. 2025; B. van der Holst et al. 2026), all non-adiabatic shock heating was channeled to the cold protons, resulting in a too large temperature jump at the termination shock (TS) for the thermal solar wind. Using a new methodology we improved the simulation results with respect to the temperature jump observed at the TS by Voyager 2 (V2) spacecraft. Our simulations approached the observed jump conditions of a factor 10–20 in the cold solar wind temperature V2 measurements, and we obtain improvements in the simulation results relative to the data. Because we directly estimate in this way the distribution of non-adiabatic heating at the TS, we have the opportunity to study the physical process of heating cold plasma and PUIs in the TS. The results show that having almost 100% non-adiabatic shock heating going towards PUIs at the TS reproduces the jump conditions observed along the V2 trajectory. This information is key to understanding the physical processes that shape the heliosphere. As shown by M. Opher et al. (2020), PUIs significantly change the shape of the heliosphere, for example, the presence of hot PUIs results in a deflated inner heliosheath. Our work provides the architecture of how energy partitioning at shocks in kinetic simulations (J. Giacalone et al. 2021) can be utilized in global MHD models.
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All authors Judit Szente, Bart van der Holst, Gabor Toth, Merav Opher

Earth and Planetary Astrophysics

Enabling Metallicity Measurements of M-dwarf Microlensing Lenses out to the Galactic Bulge

Jiyuan Zhang, Gregory Green, Weicheng Zang et al. (+2 more)

We demonstrate that metallicity becomes identifiable for M-dwarf microlensing lenses out to bulge distances when multi-band lens photometry is combined with the angular Einstein radius, thereby defining the photometric–microlensing metallicity method. The cool atmospheres of M dwarfs contain abundant molecules, whose broad absorption bands make their positions in an optical–NIR color–absolute magnitude diagram sensitive to metallicity. The angular Einstein radius provides the mass–distance constraint needed to infer the lens absolute magnitude, while the intrinsic M-dwarf locus and reddening vector are non-parallel in color–color space, allowing the lens extinction and intrinsic color to be inferred simultaneously from its multi-band photometry, thereby recovering the lens intrinsic position in the metallicity-sensitive color–absolute magnitude diagram. The method requires three-band lens photometry spanning roughly the R, Z, and K bands, making it particularly well suited to Roman through its high-resolution F062, F087, and F213 imaging. With the planned Roman Galactic Bulge Time-Domain Survey (GBTDS) observations plus an additional $\sim$8 hr of F062 imaging per field ($\sim$40 hr in total) roughly a decade after Roman launch, host metallicities could be measured for $\sim$150 planetary systems under the GBTDS yield forecast, with a typical $1\sigma$ precision of $\sim$0.25 dex from our mock-recovery analysis. Applied homogeneously to GBTDS microlensing events with and without detected planets, the method would enable the first measurement of the occurrence–metallicity relation for cold low-mass planets beyond the snow line, constrain the low-metallicity cutoff for their formation, and extend occurrence–metallicity studies into the inner Galaxy.
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All authors Jiyuan Zhang, Gregory Green, Weicheng Zang, Hongjing Yang, Shude Mao

Earth and Planetary Astrophysics

A Homogeneous Survey of JWST MIRI Transmission Spectra of 10 Exoplanets

Martin Binet, Nikku Madhusudhan, Måns Holmberg et al. (+1 more)

The launch of JWST has enabled unprecedented atmospheric characterization of exoplanets. In particular, the JWST-MIRI instrument in the mid-infrared enables probing of molecular species that are harder to detect in the near-infrared. This has come to the fore with the first MIRI-LRS observation of a candidate hycean world, K2-18 b, with potential signs of dimethyl sulfide in its atmosphere. The statistical significance of this result has been debated in subsequent works, arguing instead for the possibility of random noise, instrumental systematics, or a different molecule. The same applies to similar spectra reported for several other exoplanets using MIRI-LRS and interpreted with similar retrieval architectures. In this work, we distinguish between these possibilities with a homogeneous survey of MIRI-LRS transmission spectra of 10 diverse exoplanets, from temperate sub-Neptunes to hot rocky planets and gas giants. We first perform a comparative assessment of the spectra, considering fits with featureless models and pairwise correlations, followed by extensive atmospheric retrievals. With the retrievals, we search for over 150 trace species in the atmosphere of each planet. We find hints of complex molecules in the temperate sub-Neptunes and candidate hycean worlds K2-18 b, TOI-732 c and TOI-270 d, similar to previous works, but not in the other seven planets. Our results indicate that the observed spectral features are likely due to molecular absorption rather than instrument systematics or noise, and underscore these temperate sub-Neptunes as a unique class of planets. More observations are required to robustly identify the specific molecules and constrain the underlying chemical processes, biotic or abiotic.
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All authors Martin Binet, Nikku Madhusudhan, Måns Holmberg, Subhajit Sarkar

Instrumentation and Methods for Astrophysics

What is new in NuRadioMC: Multilayer Analytic Raytracer

Hannes Warnhofer, Sjoerd Bouma, Vital De Henau et al. (+14 more)

NuRadioMC is a framework for the simulation of ultra-high-energy neutrino detectors that measure the radio signal emitted in neutrino-induced particle cascades used in different radio neutrino experiments. We present an extension to the analytic raytracing method for multilayered exponential refractive index models, where the full refractive index profile is described by a set of different single-exponential layers, supporting realistic medium descriptions at various experiment sites while maintaining computational efficiency. This approach also enables a realistic exponential refractive index description of the atmosphere and allows us to model signal propagation over non-smooth changes in the refractive index. This report outlines the fundamentals of the multilayered analytic raytracing method and shows some applied examples.
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All authors Hannes Warnhofer, Sjoerd Bouma, Vital De Henau, Bryan Hendricks, Jakob Henrichs, Nils Heyer, Enrique Huesca Santiago, Annanay Jaitly, Philipp Laub, Anna Nelles, Martin Ravn, Felix Schlüter, Zeynep Su Selcuk, Karen Terveer, Christian Glaser, Christoph Welling, Philipp Windischhofer

Earth and Planetary Astrophysics

Planetary gas gaps and kinematic signatures in the planet forming disk around WISPIT 2

Nienke van der Marel, Jochen Stadler, Andres F. Izquierdo et al. (+7 more)

The giant planet formation process in disks of gas and dust surrounding young stars is observationally still poorly constrained. Direct detection of protoplanets within the disk remains limited with current facilities. Indirect observational evidence of protoplanets through substructures or deviations from Keplerian rotation in the gas remains ambiguous in absence of detected planets. The lack of the combined detection of substructures and their corresponding planets makes it challenging to connect the planet formation process to the host environment. Observations with the Atacama Large Millimeter Array (ALMA) reveal clear detections of gas gaps and kinematic signatures in the WISPIT 2 protoplanetary disk that are cospatial with the locations of previously detected giant protoplanets. The newly identified gas gaps, observed in both the 12CO integrated intensity map and its rotation curve, correspond with the previously identified gaps in scattered light. Their morphologies are shown to be consistent with eccentric gaps, as expected from planet-disk interaction models of massive planets. The lack of eccentricity in the outer disk can be explained if a third planet is present in the system. The observations of WISPIT 2 provide a long-sought empirical bridge between kinematic signatures, gas gaps and giant planet formation in disks.
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All authors Nienke van der Marel, Jochen Stadler, Andres F. Izquierdo, Ruobing Dong, Bertram Bitsch, Jake Byrne, Richelle van Capelleveen, Chloe Lawlor, Christian Ginski, Matthew Kenworthy.

Astrophysics of Galaxies

Stellar Population and Dynamical Modeling of Galaxies with Kinematically Misaligned Components: Age and Metallicity of Structural Components

V. S. Goradzhanov, K. O. Parfenov, D. D. Mishurin et al. (+1 more)

We present stellar population and orbit modeling of two galaxies with kinematically misaligned components, PGC 35706 and LEDA 2220522, extending previous Schwarzschild dynamical models. Using spatially resolved age and metallicity maps from NBursts full spectral fitting of MaNGA data with the E-MILES grid, we solve a regularized bounded linear inverse problem that assigns light-weighted SSP-equivalent age, metallicity, and mass-to-light ratio to orbital cells in the $(R,\lambda_z)$ plane. Component means and radial profiles use projected mass within the actual MaNGA field of view; profile segments with local component fractions below $1\%$ are treated as weakly constrained. In LEDA 2220522, the counter-rotating disk is younger than the co-rotating disk, $1.32\pm0.04$ versus $1.61\pm0.06$ Gyr, and more metal-rich, $[\mathrm{M/H}]=-0.450\pm0.043$ versus $-0.613\pm0.024$. Its rotation agrees with that of the H$\alpha$ ionized gas, supporting late supply of chemically enriched retrograde gas without requiring multiple accretion episodes with alternating angular momentum. In PGC 35706, the counter-rotating disk contains $8.8\%$ of the mass in the observed field and is formally older than the co-rotating disk by $1.36\pm0.51$ Gyr and more metal-poor by $0.130\pm0.046$ dex. These differences are preliminary because the projected data provide limited support. Fifty Monte Carlo realizations confirm stability of the projected maps against statistical noise, but not uniqueness in individual phase-space cells. The stellar population and orbit approach is therefore applicable to MaNGA data when local projected component fractions and systematics from regularization and the dynamical model are explicitly considered.
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All authors V. S. Goradzhanov, K. O. Parfenov, D. D. Mishurin, O. K. Sil'chenko

High Energy Astrophysical Phenomena

Exploring the connection between Fast Radio Bursts and binary neutron star mergers

Barbara Patricelli, Maria Grazia Bernardini, Cecilia Sgalletta et al. (+1 more)

Fast Radio Bursts (FRBs) are highly energetic radio sources whose duration is of the order of milliseconds. The physical origin of these sources is still unknown. Many models suggest magnetars as possible progenitors of FRBs, and this is supported by the association between FRBs and the Galactic magnetar SGR 1935+2154; other proposed progenitors include binary neutron star (BNS) mergers, that are themselves linked to magnetar formation. In this work we investigate the possible connection between FRBs and BNS mergers, including magnetars that might be produced in such events, by comparing the detection rates inferred from synthetic BNS and associated FRB populations with the rates observed by CHIME. We produce a synthetic catalog of BNS mergers by combining recent theoretically predicted BNS merger rate as a function of redshift and the neutron star mass distribution inferred from measurements of Galactic BNSs. Using this catalog we predict the number of BNS systems ending as magnetars (stable or supramassive neutron star) or black holes (formed promptly or after the collapse of a hypermassive neutron star) for different equations of state. We then simulate for each BNS (and therefore for each magnetar remnant) an associated FRB and estimate how many of them can be potentially detected by CHIME. We find that the rate of BNS mergers and the rate of magnetars produced after BNS represents a non-negligible fraction of the FRBs detected by CHIME, both repeating and non-repeating. Although additional formation channels need to be considered to account for the entire population of FRBs, the existence of a fraction of FRBs that might genuinely be associated to BNS mergers has profound implications in the context of multi- messenger astronomy, supporting the systematic searches of coincident detections of FRBs and GWs from a BNS merger with current and future facilities.
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All authors Barbara Patricelli, Maria Grazia Bernardini, Cecilia Sgalletta, Michela Mapelli

Instrumentation and Methods for Astrophysics

Active focal plane phase mask coronagraphy with a discrete pixelated device: I. Study of the theoretical performance trade space

Liurong Lin, Axel Potier, Ruben Tandon et al. (+2 more)

Recent advances in high-contrast exoplanet imaging instrumentation have introduced the concept of adaptive coronagraphy. For example, liquid-crystal-on-silicon spatial light modulators can be used as programmable phase masks or digital micro-mirror devices as configurable pupil apodizers. Adaptive coronagraphy offers the ability to adjust in real time to changing observing conditions and science goals, such as switching between blind surveys and follow-ups of known objects, or optimizing observations of multiple star systems including binaries and triples. At the same time, these active devices present challenges: finite spatial sampling, limited phase resolution, and the scalar nature of their modulation can all reduce coronagraphic performance. We look at the performance of a coronagraph utilizing pixelated discrete focal plane masks in function of various key parameters, notably spatial sampling, phase resolution, temporal jitter, and calibration errors. The analysis includes several FPM designs: vortex, four-quadrant phase mask, Roddier and Roddier, dual-zone phase mask, and azimuthal cosine phase mask. Both monochromatic and 20% broadband imaging conditions are considered, along with the absence or presence of a central obstruction from a secondary mirror in the telescope pupil, associated with variations in Lyot stop sizing. Our results identify the main error sources and limiting parameters of scalar, pixelated FPM coronagraphs. Under ideal conditions, performance is mainly limited by spatial sampling and chromaticity of scalar phase modulation. These devices are therefore primarily relevant to ground-based high-contrast imaging rather than the deeper contrast regimes required by future space observatories. Although motivated mainly by SLM implementations, the conclusions should also apply to other discrete pixelated focal-plane phase masks.
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All authors Liurong Lin, Axel Potier, Ruben Tandon, Lucas Marquis, Jonas G. Kühn

Instrumentation and Methods for Astrophysics

Laboratory characterization of Hierarchical Fringe Tracking

Roxanne Ligi, Stéphane Lagarde, Romain Petrov et al. (+7 more)

One of the main limitations in long-baseline interferometry lies in its fringe tracking sensitivity. The challenge is therefore to maximize this sensitivity while minimizing the spreading of the signal on the detector. This is the goal at the core of the hierarchical fringe tracking (HFT) concept. We present the laboratory characterization of the $2^{nd}$ generation HFT chips operating in the near infrared (H band) for up to 4 telescopes with more linear phase and group delay estimators, allowing a strong simplification of the tracking algorithm. We show a comparison between theoretical intensity outputs for an optimized phase delay chip, and the laboratory measurements of two chips with different designs. The results do not reach the expectations but get close to them with the 10-outputs chip. Ultimately, this new chip is intended for implementation on the VLTI, CHARA or on the future Xuyi 100m-baseline Stellar Interferometer using three telescopes.
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All authors Roxanne Ligi, Stéphane Lagarde, Romain Petrov, Sylvie Robbe-Dubois, Julien Dejonghe, Fatmé Allouche, Teng Xu, Wei Wei, Massinissa Hadjara, Abdelkarim Boskri

Astrophysics of Galaxies

The dispersal law of young star clusters: free expansion – A Gaia/eROSITA census of Orion and Sco–Cen

João Alves, Stefan Meingast and Alena Rottensteiner

We measure how young star clusters disperse over time in the two nearest star-forming complexes. Our sample comprises 44 SigMA-Gaia-defined clusters in Orion and 31 in Sco–Cen, with isochronal ages of 2–25\,Myr. We extend each cluster's census with eROSITA-selected young stars that share its parallax and motion and lie within the distance they could have traveled ballistically since birth. By 10–30\,Myr, about one in three former cluster stars lies outside the cluster's cataloged boundary. Across both complexes and the full age range, we find that (1) the half-member radius increases linearly with age, $\rfifty \simeq \sigbirth t$, (2) the velocity dispersion shows no measurable evolution, and (3) all studied clusters are unbound. These results support free expansion. Young clusters in Orion and Sco-Cen emerge unbound from their birth clouds and coast at their birth velocity dispersion without significant relaxation or a characteristic dispersal timescale. We further show that memberships defined by density contrast preferentially omit the fastest stars, making the same clusters appear to expand more slowly ($\propto t^{0.6}$), cool with age, and approach equilibrium.
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Astrophysics of Galaxies

PPN–spin degeneracies in mock S62-like stellar-orbit inference

Shant Khlghatyan

We investigate the degeneracies between black hole (BH) spin effects and parametrized post-Newtonian (PPN) parameters in the relativistic orbital dynamics of S2-like and S62-like stars orbiting Sagittarius A$^{\ast}$. Using a 1PN+SO Hamiltonian framework and synthetic astrometric and radial velocity datasets, we perform Bayesian parameter inference. For current baseline observational precisions, the dominant relativistic observable–the Schwarzschild periapsis advance–allows the recovery of the effective precession parameter $\Upsilon$, while leaving the individual PPN parameters $\gamma$ and $\beta$ degenerate. Assuming microarcsecond-level astrometric precision, the spin-induced Lense-Thirring signal becomes partially detectable; fixing the PPN sector to General Relativity allows the BH spin magnitude to be constrained to an uncertainty of $\sim10^{-2}$. However, simultaneously varying PPN and spin parameters reveals a strong, approximately linear covariance between $\Upsilon$ and the dimensionless spin parameter $\chi$. To overcome this limitation, we demonstrate that joint multi-star inference can disentangle the degeneracy by combining a wider-orbit star, which constrains the dominant 1PN sector, with a compact relativistic orbit that is sensitive to Lense-Thirring frame dragging.
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Cosmology and Nongalactic Astrophysics

Euclid. A two-point correlation approach to diagnosing star-related systematics in the Euclid spectroscopic survey

Euclid Collaboration: I. Risso, B. R. Granett, E. Branchini et al. (+297 more)

The Euclid spectroscopic survey will measure galaxy clustering with unprecedented precision, requiring stringent control of observational and instrumental systematics. Star-related effects may contaminate spectroscopic images through photometric persistence and imperfect masking of stars. We characterized their impact on galaxy clustering analyses, focusing on angular features identifiable in the data. We used angular and spatial auto- and cross-correlation statistics. For galaxies, we used mock spectroscopic catalogues from the EuclidLargeMocks in a 330 deg2 region of the Euclid Wide Survey (EWS). For stars, we used Gaia and 2MASS catalogues in the same area. To simulate photometric persistence, we implemented a simplified detector-level model calibrated on spectroscopic measurements and varied its strength to introduce different interloper fractions. For stellar masking, we modelled inconsistencies between the mask applied to the data and to the random catalogue. We measured star-star, galaxy-galaxy, and star-galaxy angular correlation functions using the Landy–Szalay estimator, and quantified deviations from the expected null star-galaxy correlation. We also evaluated the large-scale impact of such systematics through the three-dimensional two-point correlation function (2PCF). Photometric persistence produces a characteristic feature in the star-galaxy angular cross-correlation at scales of order 100", corresponding to the Euclid dithering pattern and grism dispersion geometry, and a spurious positive signal approximately constant up to 1{\deg}. Star-galaxy cross-correlation can detect residual persistence at contamination levels as low as 10% in a Data Release 1 spectroscopic catalogue. In contrast, stellar-mask mismatches produce strong small-scale angular signatures but have negligible impact on the large-scale 2PCF under realistic EWS conditions.
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All authors Euclid Collaboration: I. Risso, B. R. Granett, E. Branchini, A. Veropalumbo, B. Kubik, P. Monaco, J. Comparat, A. Hall, N. Aghanim, B. Altieri, A. Amara, S. Andreon, N. Auricchio, C. Baccigalupi, M. Baldi, A. Balestra, S. Bardelli, P. Battaglia, A. Biviano, M. Bolzonella, M. Brescia, S. Camera, G. Cañas-Herrera, V. Capobianco, C. Carbone, J. Carretero, F. J. Castander, M. Castellano, G. Castignani, S. Cavuoti, A. Cimatti, C. Colodro-Conde, G. Congedo, L. Conversi, Y. Copin, F. Courbin, H. M. Courtois, H. Degaudenzi, S. de la Torre, G. De Lucia, H. Dole, F. Dubath, X. Dupac, S. Dusini, S. Escoffier, M. Farina, R. Farinelli, S. Ferriol, F. Finelli, N. Fourmanoit, M. Frailis, E. Franceschi, M. Fumana, L. Gabarra, S. Galeotta, K. George, W. Gillard, B. Gillis, C. Giocoli, J. Gracia-Carpio, A. Grazian, F. Grupp, L. Guzzo, S. V. H. Haugan, S. Hemmati, W. Holmes, F. Hormuth, A. Hornstrup, K. Jahnke, M. Jhabvala, B. Joachimi, S. Kermiche, A. Kiessling, M. Kümmel, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, M. Magliocchetti, G. Mainetti, O. Mansutti, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, N. Mauri, E. Medinaceli, M. Melchior, M. Meneghetti, E. Merlin, G. Meylan, A. Mora, M. Moresco, C. Moretti, L. Moscardini, R. Nakajima, C. Neissner, S.-M. Niemi, J. W. Nightingale, C. Padilla, S. Paltani, F. Pasian, W. J. Percival, V. Pettorino, A. Pezzotta, S. Pires, G. Polenta, M. Poncet, L. A. Popa, F. Raison, A. Renzi, J. Rhodes, G. Riccio, F. Rizzo, E. Romelli, M. Roncarelli, B. Rusholme, R. Saglia, Z. Sakr, A. G. Sánchez, D. Sapone, B. Sartoris, P. Schneider, T. Schrabback, M. Scodeggio, A. Secroun, E. Sihvola, C. Sirignano, G. Sirri, L. Stanco, P. Tallada-Crespí, A. N. Taylor, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, J. Valiviita, T. Vassallo, Y. Wang, J. Weller, G. Zamorani, F. M. Zerbi, E. Zucca, M. Ballardini, E. Bozzo, C. Burigana, R. Cabanac, M. Calabrese, A. Cappi, F. Caro, T. Castro, J. A. Escartin Vigo, J. García-Bellido, T. Gasparetto, J. Macias-Perez, R. Maoli, R. B. Metcalf, A. A. Nucita, M. Pöntinen, E. Sarpa, V. Scottez, M. Sereno, M. Tenti, M. Tucci, M. Viel, M. Wiesmann, J. A. Acevedo Barroso, Y. Akrami, I. T. Andika, S. Anselmi, M. Archidiacono, G. Aricò, F. Atrio-Barandela, M. Baes, L. Bazzanini, J. Bel, D. Bertacca, M. Bethermin, F. Beutler, L. Blot, M. Bonici, M. L. Brown, S. Bruton, B. Camacho Quevedo, P. Carrilho, C. S. Carvalho, F. Cogato, T. E. Collett, S. Conseil, S. Contarini, A. R. Cooray, P. Corcho-Caballero, B. Csizi, O. Cucciati, S. Davini, T. de Boer, F. De Paolis, G. Desprez, A. Díaz-Sánchez, S. Di Domizio, J. M. Diego, V. Duret, A. Enia, Y. Fang, A. Farina, A. Finoguenov, A. Franco, Y. Fu, K. Ganga, E. Gaztanaga, Z. Ghaffari, F. Giacomini, F. Gianotti, G. Gozaliasl, A. Gruppuso, M. Guidi, C. M. Gutierrez, H. Hildebrandt, J. Hjorth, M. Jauzac, J. J. E. Kajava, Y. Kang, V. Kansal, D. Karagiannis, J. Kim, C. C. Kirkpatrick, A. Kovács, I. Kovačić, K. Koyama, S. Kruk, M. C. Lam, F. Leclercq, L. Legrand, M. Lembo, G. Leroy, G. F. Lesci, J. Lesgourgues, T. I. Liaudat, L. Linke, S. J. Liu, F. Mannucci, F. R. Marleau, C. J. A. P. Martins, M. Miluzio, G. Morgante, S. Nadathur, K. Naidoo, A. Navarro-Alsina, S. Nesseris, L. Nicastro, F. Oppizzi, F. Pace, D. Paoletti, G. Parimbelli, F. Passalacqua, K. Paterson, L. Patrizii, C. Pattison, R. Paviot, A. Pisani, D. Potter, G. W. Pratt, S. Quai, M. Radovich, G. Rodighiero, W. Roster, S. Sacquegna, M. Sahlén, D. B. Sanders, A. Schneider, D. Sciotti, E. Sellentin, S. Serjeant, L. C. Smith, J. G. Sorce, I. Szapudi, M. Talia, K. Tanidis, C. Tao, F. Tarsitano, G. Testera, R. Teyssier, S. Tosi, A. Troja, C. Uhlemann, C. Valieri, A. Venhola, D. Vergani, G. Verza, S. Vinciguerra, M. von Wietersheim-Kramsta, N. A. Walton, L. Wang, A. H. Wright

Earth and Planetary Astrophysics

Stability of circumbinary planets: the role of binary properties and migration scenarios

Romain Grane, Nicolás Cuello, Mario Sucerquia et al. (+4 more)

Among the thousands of exoplanets detected to date, only a very small fraction are classified as circumbinary planets, and this number becomes negligible when considering low-mass planets. This rarity may partly result from observational biases, but also from the challenging dynamical environment of binary systems, which can prevent the long-term stability of planetary orbits. It is therefore essential to investigate the conditions that enable the formation and survival of stable circumbinary planets, particularly in the low-mass regime. To this end, we performed N-body simulations coupled with a planet migration prescription to study the post-formation dynamics of two 10 Earth-mass circumbinary planets in a protoplanetary disc. Based on more than 1,000 simulations, we find that inward migration can, in some cases, be halted through resonance capture with the binary. In contrast to some previous purely N-body studies, these configurations appear to remain stable over long timescales. We further find that the binary mass ratio $q_B$ and eccentricity $e_B$ strongly influence the stability of multi-planet systems. Within the explored parameter space, some regions support long-term stability, whereas others are highly unstable. These stability regions are also sensitive to the migration timescales, and therefore to disc properties and planetary masses. Finally, our simulations suggest that systems in which two planets enter resonance while migrating together are more likely to form stable multi-planet configurations, particularly around highly eccentric binaries. These results provide a first step toward identifying binary star systems that are most promising for hosting multiple low-mass circumbinary planets.
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All authors Romain Grane, Nicolás Cuello, Mario Sucerquia, Emmanuel Gianuzzi, Milenne Ávila-Bravo, Carolina Charalambous, Amaury H. M. J. Triaud

Solar and Stellar Astrophysics

Can isolated binaries form unequal-mass binary black-hole mergers with a high-spin primary black hole?

Xiao-Tian Xu, Dong Lai and Bin Liu

GWTC-5 has revealed a subpopulation of merging binary black holes (BBHs) with a high-spin primary black hole (BH) and possibly unequal BH masses. GW241110 additionally exhibits a large spin-orbit misalignment, which suggests a hierarchical-merger origin. However, other formation scenarios are possible or even likely, especially for events without constraints on spin-orbit misalignment. As an alternative to hierarchical mergers, we investigate whether binary evolution can produce unequal-mass BBH mergers with a high-spin primary BH. Rather than performing comprehensive population-synthesis calculations, we examine the evolutionary pathways of forming merging BBHs and assess their uncertainties. We identify two possible pathways for producing unequal-mass BBHs with a high-spin primary. In initially wide binaries, mass-ratio reversal can make the tidally spun-up second-born BH both more massive and more rapidly rotating than the first-born BH; alternatively, in an initially close, unequal-mass binary, the primary star may evolve chemically homogeneously, while the secondary star evolves normally, producing a high-spin first-born BH that is more massive than its companion. Generally, large spin-orbit misalignment can be produced by large natal kicks or tertiary-induced nodal precession and/or Zeipel-Lidov-Kozai oscillations. We conclude that hierarchical mergers are not uniquely required to produce unequal-mass BBHs with a high-spin primary BH, although each isolated-binary pathway faces important theoretical constraints. Future detections of more merger events with primary BH spins around 0.7 would discriminate between binary evolution and hierarchical merger origin.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Probing Neutron Star Equation of State Universality with Gravitational Waves

Praveer Tiwari, Ajit Kumar Mehta and K. G. Arun

Current neutron star equation-of-state inferences assume that a common equation of state describes all neutron stars. However, {poorly understood dense-matter physics may give rise to distinct long-lived stellar subpopulations following different mass–tidal-deformability relations, invalidating this assumption. In this Letter, we demonstrate that next-generation gravitational-wave observatories enable neutron star equation-of-state universality to be transformed from an assumption into a testable hypothesis. By combining hierarchical Bayesian inference with a piecewise-polytropic parametrization of the neutron star equation of state, we establish a framework for testing equation-of-state universality with next-generation gravitational-wave observatories. We find that about 30 (50) loud binary neutron star mergers with network SNRs above 100 are sufficient to provide compelling evidence for departures from equation-of-state universality, even if only 20% (10%) of the population exhibits one of the representative non-universality parametrizations considered here.
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