High Energy Astrophysical Phenomena
Evidence for orbital eccentricity supports a hierarchical origin for GW231123
Baoxiang Wang, Tao Yang, Zhoujian Cao et al. (+3 more)
GW231123 is the most massive binary black hole merger observed to date and one of the most intriguing hierarchical merger candidates in the pair-instability mass gap. Its exceptionally large inferred component
spins and remarkably short in-band duration make the source highly sensitive to waveform physics near merger. Here we show that GW231123 is better described as an eccentric binary black-hole merger. We analyse data over 11–448 Hz using the eccentric,
spin-precessing effective-one-body waveform model TEOBResumS–Dalí, accounting for detector calibration uncertainty. We measure $e_{5.5\,\mathrm{Hz}}=0.34^{+0.12}_{-0.23}$ at 90% credibility and obtain a Bayes factor of 10.2 in favour of the eccentric model over its quasi-circular counterpart. GW231123-like injection–recovery studies further show that analyses starting at 20 Hz, as in previous studies, can obscure this eccentricity. Including eccentricity substantially changes the
spin inference, weakening the preference for a near-extremal secondary
spin and lowering its posterior median to $a_2\simeq0.7$, close to the characteristic
spin expected for a black-hole merger remnant. These results provide a coherent dynamical interpretation of GW231123, in which residual eccentricity, a mass-gap black hole, and a remnant-like
spin arise naturally from a hierarchical merger channel in a dense environment.
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All authors Baoxiang Wang, Tao Yang, Zhoujian Cao, Bin Hu, Xikai Shan, Rong-Gen Cai
High Energy Astrophysical Phenomena
Autocorrelation in black hole flare movies: Departures from Kerr
Fang-Stars Wei, Zelin Zhang, Zhenyu Zhang et al. (+1 more)
Autocorrelation in black hole movies encodes the time delays and angular separations between gravitationally lensed images, offering a means of testing the spacetime geometry. Using an orbiting hot spot in the parametrized Johannsen-Psaltis metric with a single deformation parameter, we investigate the ability of
lensing-induced correlations to distinguish departures from Kerr. From ray-traced movies, we extract the slope (k) and intercept (b) of an approximately linear secondary ridge in the time-angle autocorrelation map as potential future observables. Variations in the
spin and the metric deformation parameter produce distinctive trajectories in the (k,b) plane, allowing the two observables to jointly constrain both parameters when the orbital radius, observer inclination, and orbital angular velocity are specified. By varying the orbital angular velocity, we construct a Kerr reference region in the (k,b) plane, and we find that, for some low-
spin configurations with negative deformation parameters, the measured slope-intercept pairs of the secondary peaks lie outside this reference region. This feature appears for sub-Keplerian, Keplerian, and super-Keplerian motion, indicating that secondary-ridge measurements from black hole
flare movies have the potential to distinguish non-Kerr signatures.
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All authors Fang-Stars Wei, Zelin Zhang, Zhenyu Zhang, Bin Chen
Astrophysics of Galaxies
Modeling CO Line Luminosity Using FIRE Simulations: I. Methodology and Validation of Molecular Gas and CO Abundance
Doğa Tolgay, Norman W. Murray, Dongwoo Chung et al. (+5 more)
We present a post-processing pipeline that predicts CO line luminosities, molecular hydrogen masses, and CO abundances for
galaxies in the Feedback in Realistic Environments (FIRE-2) simulations, as a first step toward CO response functions for line intensity mapping mocks. SKIRT gives the radiation field reaching each gas
cell. CLOUDY, tabulated on a five-parameter grid (
metallicity, density, turbulent velocity, radiation field, cloud scale) and interpolated, gives $L'_{\rm CO(1-0)}$ and the $\rm H_2$ and CO masses. In this first of three papers we validate the pipeline against observations. For Milky Way (MW) molecular clouds, the predicted $L'_{\rm CO(1-0)}$ rises sharply at $A_V\sim1$ and matches the observed values above that column. For a uniform $3\,Z_\odot$ the summed luminosity is within 35% of the observed total. A factor of three increase in
metallicity changes the total $L'_{\rm CO(1-0)}$ by an order of magnitude. Along MW sight lines, the predicted $N_{\rm CO}/N_{\rm H_2}$ reproduces the observed upturn within 0.3 dex in $N_{\rm H_2}$ but falls below the data at higher columns. At $z=0$ our molecular gas masses agree with xCOLD GASS for ${\rm SFR}\gtrsim0.3\,M_\odot\,yr^{-1}$ and are converged across our simulation resolutions. At $z\gtrsim1$ observed gas masses exceed ours at fixed stellar mass, though selection effects and conversion-factor assumptions limit this comparison. CO luminosities are compared with extragalactic observations in Paper II. Capturing the
metallicity-dependent dust shielding of CO from photodissociation is essential for modeling CO emission in low-mass and high-
redshift galaxies.
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All authors Doğa Tolgay, Norman W. Murray, Dongwoo Chung, J. Richard Bond, Nathan J. Carlson, Robert Feldmann, Andrew Wetzel, Guochao Sun
Cosmology and Nongalactic Astrophysics
HI intensity mapping with MeerKAT: A measurement of the 21-cm auto-spectrum on cosmological scales
MeerKLASS Collaboration, Matilde Barberi-Squarotti, José L. Bernal et al. (+16 more)
We report a direct measurement of the 21-cm signal from neutral hydrogen (HI) via the intensity mapping technique at
redshift $z = 0.42$ through its power spectrum at cosmological scales $0.095\,h\,{\rm Mpc}^{-1}<k<0.245\,h\,{\rm Mpc}^{-1}$. We analyse intensity maps observed in the frequency range $971.2\,{\rm MHz}<\nu<1023.6\,{\rm MHz}$ during the 2021 observational campaign of the MeerKAT Large Area Synoptic Survey (MeerKLASS) spanning an area of approximately $236\,{\rm deg}^2$. Capitalising on the depth of this survey, we divide the data set into multiple observationally independent subsets. After performing blind contaminant separation independently on each subset, we exploit internal cross-correlations to suppress the instrumental noise plateau and isolate the cosmological signal from residual systematics. Although the subsets' auto-spectra show the presence of excess power that we deem linked to still unresolved systematics, the cross-spectra measurements satisfactorily pass a battery of null and robustness tests. We introduce a multi-subset formalism to infer the amplitude of the HI auto-spectrum from our internal cross-spectra measurements while marginalising the potential signal loss that occurs during data processing, reaching a detection with signal-to-noise ratio of 6.2. We constrain the clustering amplitude of the signal in terms of the HI
cosmic abundance and its linear bias, measuring $10^3\,\Omega_{\rm HI} b_{\rm HI}=1.271^{+1.080}_{-0.598}$. This direct measurement marks a milestone in demonstrating the effectiveness of the HI intensity mapping technique for future surveys with the SKA Observatory, of which MeerKAT is a precursor.
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All authors MeerKLASS Collaboration, Matilde Barberi-Squarotti, José L. Bernal, Philip Bull, Stefano Camera, Isabella P. Carucci, Zhaoting Chen, Steven Cunnington, Brandon N. Engelbrecht, José Fonseca, Keith Grainge, Wenkai Hu, Melis O. Irfan, Yichao Li, Mário G. Santos, Marta Spinelli, Jingying Wang, Amadeus Witzemann, Laura Wolz
High Energy Astrophysical Phenomena
Discovery of the Slowest Radio Pulsar in the Small Magellanic Cloud
Weiyu Wang and Rahul Sengar
We report the discovery of a new
radio pulsar PSR J0103$-$72 in the Small Magellanic Cloud (SMC) through a reanalysis of Parkes/Murriyang archival observations targeting
supernova remnants and
pulsar-wind nebulae in the SMC. Previously two
pulsars were discovered in these observations, and PSR J0103$-$72 is the third which we independently detected in two observations of its target field. It has a
spin period of 1.327 sec and a dispersion measure (DM) of $272\pm13~\mathrm{pc\,cm^{-3}}$, making it the slowest known
radio pulsar in the SMC with the second-highest DM. We did not identify any plausible
supernova remnant or
pulsar-wind nebula associated with the
pulsar. Subtracting the predicted Galactic foreground leaves a DM contribution of $\sim 230$–$242~\mathrm{pc\,cm^{-3}}$, which may suggest a long path through the ionized medium of the SMC, enhanced ionized gas along the sightline, or both. Although these data had previously been searched using both FFT and fast folding
algorithms, our FFT-based reprocessing found PSR J0103$-$72 through search techniques which have previously been highly effective in discovering a large number of
pulsars in other surveys. This discovery shows that candidates with weak
Fourier-domain significance can reveal faint, narrow-duty cycle
pulsars missed in earlier extragalactic
pulsar searches.
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Astrophysics of Galaxies
Too many or too bright? Status and perspectives in the study of the UV Luminosity Function at z>10
A. Fontana, H. Atek, V. Bromm et al. (+20 more)
The finding that
galaxies in the first 500Myr were much more numerous and/or brighter than expected is often cited as one of the main discoveries of the James Webb Space
Telescope in its first four years of operation. This result is now solidly based on an impressive number of surveys that have detected, spectroscopically confirmed, and characterized a relatively large sample of
galaxies up to z=14.44, the
redshift of the most distant
galaxy currently known. This finding has motivated the introduction of additional physical mechanisms into theoretical models to reproduce the observed numbers and luminosities. These results contrast with the failure, despite ongoing efforts, to confirm any
galaxy candidate beyond this
redshift. This review summarizes the status of the search for and characterization of
galaxies at z>9, focusing on the
evolution of the UV Luminosity Function (UVLF), which is the main statistical description of the
galaxy population that can be obtained at these
redshifts. We first provide a comprehensive overview of the full set of JWST data obtained so far. We perform a 'meta–analysis' on the entire data set and provide a simple yet effective description of the global
evolution of the UVLF, averaging over the various surveys. We also compare these results extensively with theoretical models that were developed to match the new JWST observations and that explore different physical mechanisms able to drive the observed
evolution. We conclude with a summary of the contrasting results regarding the search for
galaxy candidates at z>15, and outline the requirements for future surveys aimed at breaking this barrier.
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All authors A. Fontana, H. Atek, V. Bromm, A. J. Bunker, M. Castellano, P. Dayal, F. D'Eugenio, D. Elbaz, A. Ferrara, S. L. Finkelstein, S. Fujimoto, M. Giavalisco, Y. Harikane, C. Kobayashi, F. Pacucci, P. G. Pérez-González, P. Rosati, A. Trinca, R. Tripodi, P. Santini, E. Vanzella, A. Venditti, A. Weibel
Solar and Stellar Astrophysics
EWOCS-XI: Anisotropic expansion and shear in the cluster Westerlund 1. A 2D kinematic analysis with Gaia DR3
L. Prisinzano, F. Damiani, C. Ordenes-Huanca et al. (+14 more)
Westerlund 1 (Wd1) is one of the Milky Way's most massive young clusters, in which heavy extinction and field contamination have historically hampered its kinematic characterization. We aim to assess Wd1's internal kinematics, dynamical state, and formation scenario. Using a robust 5D clustering approach, we identified 559 bona fide members. We modeled their proper motions via a 2D first-order Taylor expansion to derive the velocity gradient tensor, mapping expansion, rotation, and shear. Restricting the kinematic analysis to 524
stars with proper motion uncertainties $<0.5~\mathrm{mas\,yr^{-1}}$, we find at least 103 gravitationally unbound members, including 14 walkaway
stars. The 2D analysis reveals a statistically significant divergence (>4$\sigma$) highlighting preferred expansion along the Galactic latitude (position angle $164^\circ\pm10.1^\circ$). A detected cross-gradient ($\partial v_b / \partial l = -0.41 \pm 0.08$ km s$^{-1}$ pc$^{-1}$) provides a clear signature of shear on the plane of the sky. Wd1 does not behave as a single cohesive population, but comprises two decoupled subsystems: a stable, bound core in dynamical
equilibrium and an escaping, unbound envelope. This prominent anisotropic expansion perpendicular to the Galactic plane has a kinematic timescale ($\Delta t_{\mathrm{kin}} = 2.08 \pm 0.44$ Myr) matching the independent orbital mid-plane crossing time ($\Delta t_{\mathrm{orbit}} = 2.10 \pm 0.05$ Myr). This temporal
alignment indicates the expansion onset coincided with Wd1's Galactic disk passage, triggered either by internal dynamics (e.g., early
supernova feedback) or external tidal perturbations. Finally, the robust unbound population demonstrates that active cluster dissolution is underway, driven by discrete dynamical ejection events rather than long-term stellar evaporation.
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All authors L. Prisinzano, F. Damiani, C. Ordenes-Huanca, M. Tarantino, S. Sciortino, N.J. Wright, V. Almendros-Abad, M. Andersen, A. Bayo, R. Bonito, V. Cusimano, M. Haberle, K. Mužic, I. Negueruela, E. Sabbi, A. Winter, M.G. Guarcello
High Energy Astrophysical Phenomena
An updated model of neutrino emission from proto-neutron stars
Matteo Ballelli, Federica Pompa, Christoph Ternes et al. (+2 more)
We present an improved parametric model for
neutrino emission from core-collapse
supernovae that directly connects
neutrino luminosity and average energy to stellar properties during emission. Our model incorporates two critical physical processes: convection within the proto-
neutron star and the
evolution of the neutrinosphere radius during the early emission phase. Using simulated
datasets of
supernova neutrino events in the Super-Kamiokande detector, we assess the sensitivity to astrophysical properties in the event of a future detection. We show that the
neutrino mass ordering plays a crucial role in determining which parameters can be constrained by the observed
neutrino data.
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All authors Matteo Ballelli, Federica Pompa, Christoph Ternes, Marco Drago, Giulia Pagliaroli
Cosmology and Nongalactic Astrophysics
A New Era for Supernova Science with the James Webb Space Telescope
Justin Pierel, David Coulter, Christa DeCoursey et al. (+17 more)
Supernovae (SNe) are excellent probes of the physical, chemical, and cosmological context of
galaxies across the history of the Universe. The James Webb Space
Telescope (JWST ) has a truly unique combination of wavelength, sensitivity, and resolution, providing a new window into SN physics, progenitors, dust production,
redshift evolving stellar populations, and cosmology since its launch. Here we summarize the astounding observations JWST has made of SNe in its first few years of operations, as well as the corresponding advancements in our understanding of the Universe. This includes detailed views of nearby SNe, the first spectroscopic samples of high-z SNe, and a significant number of gravitationally lensed SNe valuable for both cosmological inference and high signal-to-noise (S/N) spectroscopy. While the upcoming Nancy Grace Roman Space
Telescope is expected to revolutionize space-based time-domain astronomy, JWST and its unique capabilities will continue to play a complementary role by providing high-precision spectroscopic and photometric data for a broad range of SN science cases.
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All authors Justin Pierel, David Coulter, Christa DeCoursey, James DerKacy, Ori Fox, Melissa Shahbandeh, Matthew Siebert, Michael Engesser, Conor Larison, Thomas Moore, Armin Rest, Rodrigo Angulo, Michael Dulude, Eiichi Egami, Massimo Griggio, Mitchell Karmen, Xiaolong Li, Estefania Padilla Gonzalez, Koji Shukawa, Louis-Gregory Strolger
Astrophysics of Galaxies
Binding Energies of Astrophysically Relevant Molecules on CO$_2$ Clusters: Benchmarking and the Donor-Acceptor Origin of Surface-Dependent Binding
Aneesa Ahmad, Catherine Walsh and Stefan Vogt-Geisse
Carbon dioxide (CO$_2$) is among the most abundant interstellar ices and has been observed by JWST in water-rich mixtures and pure CO$_2$ environments. Astrochemical models adopt binding energies (BEs) measured on water ice because few BEs are available for CO$_2$ ice. We calculate BE distributions for twelve adsorbates (N$_2$, CH$_4$, HCl, C$_2$H$_2$, H$_2$S, HF, HCN, H$_2$CO, HCOOH, HNC, CH$_3$OH, H$_2$O) on CO$_2$ clusters containing two to five molecules using DFT calibrated against CCSD(T)/CBS, a coupled-cluster treatment extrapolated to the complete-basis-set limit. Binding strength depends on whether the adsorbate requires the surface to donate a hydrogen bond (H-bond). CO$_2$ can accept an H-bond but cannot donate one, and all six species compared with water ice from Ahmad et al. (2026) bind more weakly on CO$_2$. The ratio of the BE on CO$_2$ to water ice ranges from 0.66 for H$_2$CO and 0.75 for H$_2$O to 0.87 for CH$_3$OH, 0.89 for HCOOH and 0.92 for C$_2$H$_2$. Formaldehyde is predicted to desorb near 57 K from CO$_2$-rich ice, compared with 85 K from water-rich ice, and could contribute to cold gas-phase H$_2$CO. Although the mean binding energies are changing with cluster size for several species, the differences can be traced to local binding interactions likely to remain important in larger ice models. The BEs vary by more than 500 K between sites, while the desorption peaks range from 11 K for CH$_4$ to 132 K for HCOOH. The limited H-bonding capacity of CO$_2$ may favour separation of mixed H$_2$O:CO$_2$ ice into CO$_2$-rich domains.
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Instrumentation and Methods for Astrophysics
On-chip filled array hyperspectral kinetic inductance detectors (FHYKID) for line intensity mapping
Emile Prêle, Martino Calvo, Usasi Chowdhury et al. (+3 more)
The next generation Line Intensity Mapping (LIM) experiments will require very high throughput instrumentation, and as a consequence high pixel counts focal planes. For the study of the [CII] line in the
redshift range z=7-8, we develop a hyperspectral filled focal plane (FHYKID) operating in the range 210-235 GHz and with a spectral resolution reaching 120. The spectral filtering is achieved thanks to planar Slot Split Ring Resonators (SSRR) coupled to Lumped Element Kinetic Inductance Detectors (LEKID). This robust concept achieves, thanks to its simplicity, large
quantum efficiency and is scalable, even with current readout electronics systems, to several tens of thousands beams on Sky. Our FHYKID will be one of the four channels of the NIKONA instrument, currently seeking funding and to be installed at the IRAM 30-meter
telescope at Pico Veleta. Among the science goals, simultaneously mapping the local (galactic and nearby-
galaxies) CO line and the cosmological [CII].
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All authors Emile Prêle, Martino Calvo, Usasi Chowdhury, Gregory Garde, Florence Levy-Bertrand, Alessandro Monfardini
Solar and Stellar Astrophysics
Volume Dependence of Helicity-based Eruption Diagnostics in Recurrent Coronal Jets
Chang Zhou, Jinhan Guo, Yang Guo et al. (+3 more)
Recurrent solar coronal jets originate from the same source region, providing a useful setting for studying the buildup, redistribution, and release of
magnetic energy and helicity. However, how these quantities can characterize
magnetic evolution and the onset conditions of the eruptions remains unclear. We perform a full three-dimensional (3D) thermodynamic magnetohydrodynamic simulation of recurrent jets driven by converging motions imposed at the bottom boundary. The simulation naturally produces two successive eruptions. The current-carrying helicity $H_J$ decreases during the first jet and gradually recovers between the two jets. In contrast, the free
magnetic energy $E_{\mathrm{free}}$ shows no clear accumulation after its first release. This difference indicates that $H_J$ provides information on
magnetic evolution beyond that provided by $E_{\mathrm{free}}$. Furthermore, the commonly used helicity ratio $H_J/H_V$ reaches different peaks near the onset of the two jets and is sensitive to the integration volume. By comparison, the locally normalized quantity $H_J/\Phi_{\mathrm{closed}}^2$ reaches similar peaks near the onset of both jets and is relatively insensitive to the choice among the tested integration volumes, where $\Phi_{\mathrm{closed}}$ is the single-polarity
magnetic flux of the closed-field domain. These results reveal the local nature of the eruptions and suggest that $H_J$ normalized by the square of the closed
magnetic flux may be a useful diagnostic of eruptive conditions.
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All authors Chang Zhou, Jinhan Guo, Yang Guo, Jiajia Liu, Zekun Lu, Yuhang Gao
Earth and Planetary Astrophysics
Size, Shape, and Geometric Albedo of Dwarf Planet Quaoar's Largest Satellite Weywot
Cameron Collyer, Estela Fernandez-Valenzuela, Benjamin Proudfoot et al. (+3 more)
The small satellites of dwarf-
planet size worlds in trans-Neptunian space are thought to be produced through giant impacts, and are typically observed to have bright water-ice-dominated surfaces. Here we focus on Quaoar's small primary satellite, Weywot. We build on previous work by re-analyzing the June 2023 stellar occultation by Weywot using results from 11 orbits of HST imaging with the Wide Field Camera 3. Weywot's rotational lightcurve was constrained along with its independent photometric phase curve, which we used to obtain more robust measurements of Weywot's size, shape, and
geometric albedo. We found Weywot's volume-equivalent radius to be req = 73+-5 km, with principal axes a = 82+5-3 , b = 73+5-3, c = 65+8-12 km, indicating a triaxial shape. This shape is consistent with a Roche-ellipsoid rubble-pile interpretation requiring only moderate internal friction at Weywot's current semimajor axis, and Weywot can retain this shape down to Quaoar's co-rotation radius. We also found Weywot's
geometric albedo to be quite low, pV = 0.036+0.010-0.006, akin to that of Eris's satellite Dysnomia, but over an order of magnitude lower than Pluto's minor satellites and Haumea's satellites. We propose this may indicate that Weywot's ice-mass fraction < 100%, and that Weywot is not sourced from the water-ice mantle of a differentiated pre-impact progenitor as suggested for Pluto's minor satellites and Haumea's satellites.
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All authors Cameron Collyer, Estela Fernandez-Valenzuela, Benjamin Proudfoot, Bryan J Holler, Jose Luis Ortiz, Ishan Sharma
Astrophysics of Galaxies · Cross-listed from physics.chem-ph
Gas-phase chemistry of $\mathrm{C}_3\mathrm{H}_3^+$: a key building block for carbon mass growth in space
Corentin Rossi, Jean-Christophe Loison, Anne P. Rasmussen et al. (+4 more)
The gas-phase chemistry of $\mathrm{C}_3\mathrm{H}_3^+$ plays a central role in the growth of carbonaceous species across a wide range of environments, from combustion systems to interstellar media. However, the presence of multiple isomers, primarily the linear propargyl cation and the cyclic cyclopropenyl cation, has so far prevented the determination of reliable isomer-specific reaction kinetics. In this work, we combine tunable
vacuum-ultraviolet (VUV) photoionization with controlled ion–molecule reaction measurements to selectively produce and probe the reactivity of $\mathrm{C}_3\mathrm{H}_3^+$ isomers. By employing a titration approach, we extract isomer-specific reaction rate coefficients and branching ratios for reactions of $\mathrm{C}_3\mathrm{H}_3^+$ with $\mathrm{C}_2\mathrm{H}_4$, $\mathrm{C}_3\mathrm{H}_4$, and $\mathrm{C}_3\mathrm{H}_6$. Our results demonstrate a strong contrast in reactivity: the most stable cyclic isomer is found to be essentially unreactive under the investigated conditions, whereas the linear isomer exhibits efficient and diverse chemistry leading to the formation of larger hydrocarbon ions. In particular, the formation of $\mathrm{C}_6\mathrm{H}_5^+$ is observed, providing an important intermediate in pathways toward aromatic species. These findings help resolve long-standing ambiguities in previously reported rate coefficients and provide new quantitative constraints for kinetic and astrochemical models. More broadly, this work highlights the importance of isomer-specific chemistry in carbon growth processes and demonstrates the effectiveness of VUV-based photoionization methods for disentangling complex reaction networks in the gas phase.
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All authors Corentin Rossi, Jean-Christophe Loison, Anne P. Rasmussen, Roland Thissen, Nandana Pattathadathil, Christian Alcaraz, Ugo Jacovella
Solar and Stellar Astrophysics
Magnetic flux cancellation in a 3D magnetohydrodynamic simulation of an emerging flux tube with a non-uniform twist
V. Agalianou, S. Patsourakos and V. Archontis
Flux emergence is often accompanied by flux cancellation, which may drive dynamic phenomena in the solar atmosphere. We studied
magnetic flux cancellation in a three-dimensional resistive magnetohydrodynamic (MHD) simulation of an emerging flux tube with a non-uniform twist profile. We solved time-dependent resistive MHD equations to model flux emergence into a magnetised background atmosphere. We identified several cancellation sites, estimated their cancellation rates, and examined the
magnetic topology and associated jet activity. The non-uniform twist produced multiple opposite photospheric polarities, leading to a complex multipolar
magnetic configuration rather than a simple dipolar structure. Interactions between inner secondary
magnetic patches resulted in flux cancellation of the photospheric $B_z$ along their polarity inversion line (PIL). These interactions led to the formation of concave-up loops and a cancellation rate of $1.1 \times 10^{19}$ Mx hr$^{-1}$. During cancellation,
magnetic reconnection between converging opposite polarities progressively created a coherent
magnetic flux rope above the cancellation region. The
evolution of the rope was associated with a blowout jet, as the rope expanded and released part of its stored twist into the overlying corona. We also examined two smaller secondary cancellation events at photospheric heights. Our results highlight the role of internal flux cancellation in restructuring the
magnetic field and driving blowout-jet activity in emerging regions.
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Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
Testing General Relativity with Binary Lens Microlensing Events
Xinyang Jin, Shuo Cao, Xuanni Chen et al. (+3 more)
Einstein's General Relativity (GR), which has been precisely tested on
galaxy and solar system scales, is still poorly constrained in extremely weak gravitational fields (with dimensionless Newtonian potentials of $\Phi \sim 10^{-8}$). In this Letter, we propose a new method to probe such a weak-field regime of
gravity and measure the spatial
curvature generated per unit mass. Specifically, binary microlensing events provide a laboratory to measure the parameterized post-Newtonian (PPN) parameter ($\gamma$), by combining the
lensing mass ($M_{\rm lens}^{\rm GR}$) inferred from microlensing with the dynamical mass ($M_{\rm dyn}$) determined from interferometric astrometry. Astrometric tracking of binary lenses was previously hindered by their faintness and minuscule angular separations (typically a few milliarcseconds). This limitation has been alleviated by the deployment of
GRAVITY+, which pushes the instrument's sensitivity and astrometric precision to unprecedented heights. Based on astrometric simulations of the binary microlensing event ASASSN-22av, we directly estimate $\gamma$ at the precision of ~23%. Such test of GR in the extremely weak-field regime can be further improved to much higher precision (~3%), based on more binary microlensing events with precise determination of the dynamical/lens mass.
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All authors Xinyang Jin, Shuo Cao, Xuanni Chen, Yalong Nan, Xuchen Tai, Shuxun Tian
High Energy Astrophysical Phenomena
From GeV to PeV: Orbital Modulation and Wind-Regulated Ultrahigh-energy Emission in Cygnus~X-3
Su-Yu Wan, Ruo-Yu Liu, Xing-Fu Zhang et al. (+1 more)
Recent LHAASO observations reveal ultrahigh-energy (UHE) gamma-ray emission from Cygnus~X-3 with evidence for orbital modulation, providing a rare opportunity to study particle acceleration and transport on binary scales. We develop a common binary–jet model that jointly explains the contemporaneous GeV–PeV spectra and orbital light curves. The GeV emission is produced by anisotropic inverse-Compton scattering of stellar
photons by relativistic electrons, while multi-PeV
protons escaping from the inner region produce TeV–PeV gamma rays through photohadronic and hadronuclear interactions. The GeV orbital modulation constrains the binary–jet geometry, allowing the UHE observations to probe the escaping
proton population and its interaction with the circum-binary environment. We find that the UHE emission is strongly regulated by the
accretion-driven wind structure. In the present state, a fast disk wind displaces much of the denser Wolf–Rayet (WR) wind from the escaping-
proton trajectories, suppressing hadronuclear emission. Changes in the strength, collimation, or orientation of the disk wind can expose the escaping
protons to a much denser WR wind and enhance the PeV gamma-ray luminosity by orders of magnitude. This provides a possible connection to the much brighter, though unconfirmed, PeV activity reported in the 1980s, and links UHE gamma-ray activity to the
accretion and outflow state of the binary.
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All authors Su-Yu Wan, Ruo-Yu Liu, Xing-Fu Zhang, Dmitriy Khangulyan
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Testing Extra-Dimensional Gravitational-Wave Polarizations with Compact-Binary Observations
Hai-Tian Wang, Dicong Liang, Lijing Shao et al. (+1 more)
Extra spatial dimensions arise naturally in theories beyond four-dimensional general relativity (GR), but direct observational evidence remains elusive. Gravitational waves offer a distinctive probe:
geometric projection onto the observable three-dimensional spatial subspace can produce apparent tensor, vector, and scalar polarizations. We consider one additional spatial dimension and a two-mode tensor-wave ansatz for which the projected polarization components are fixed linear combinations of the same two underlying GR tensor waveforms. These components enter the measured strain through the standard detector
antenna patterns. A frequency-domain
Bayesian analysis of five compact-binary events constrains two rotation angles for two noncommuting orderings of rotations that preserve propagation within the observed subspace. Two events are further analyzed for four orderings that allow propagation to tilt into the extra dimension. For GW250114, the maximum GR
quantiles among the tested rotation orderings are $Q_{\mathrm{GR}}\simeq0.6\%$ for the two-angle fits and $Q^{\mathrm{marg}}_{\mathrm{GR}}\simeq4.6\%$ for the three-angle fits after marginalizing over the third angle. Across the full event sample, the GR reference point lies inside the estimated 90% highest-posterior-density region in every case.
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All authors Hai-Tian Wang, Dicong Liang, Lijing Shao, Yu-Xiao Liu
High Energy Astrophysical Phenomena
Investigating the nature of magnetic turbulence in Tycho's SNR using X-ray observation
Ashwin Aravindaraj, Hui Zhu, Adrien Picquenot et al. (+1 more)
Supernova remnants (SNRs) are widely regarded as the primary sources of Galactic
cosmic ray acceleration and the particles are energized at the shock front of SNRs through the diffusive shock acceleration (DSA) mechanism, gaining energy by repeatedly crossing the shock.
Magnetic turbulence plays a crucial role in scattering these particles back and forth, making the investigation of
turbulence essential to understanding the acceleration process. In this study, we apply the two-point correlation method to derive the
magnetic energy spectrum from the non-thermal X-ray flux image of Tycho's SNR. This image was obtained using Poissonian-based Generalized Morphological Component Analysis (pGMCA). The
turbulence length scale observed in the resulting spectrum is shorter than the
turbulence scale derived from previous studies of
radio observations of Tycho's SNR. Additionally, we use the X-ray rim thickness measured across Tycho which is an indicator of
magnetic field strength to estimate the
magnetic energy spectrum. The
turbulence scale inferred from this method is consistent with that obtained from the non-thermal X-ray flux analysis.
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All authors Ashwin Aravindaraj, Hui Zhu, Adrien Picquenot, Hsiang-Kuang Chang
High Energy Astrophysical Phenomena
The Hand of God Revisited: Revealing the Shell Structure and Jet-Supernova Remnant Interaction in MSH 15-52
Lingxiao Dang, Isabel Sander, Samar Safi-Harb et al. (+1 more)
We present an X-ray analysis of the
supernova remnant (SNR) MSH 15-52 associated with the young rotation-powered
pulsar PSR B1509-58, using Chandra, XMM-Newton, and eROSITA, complemented by MeerKAT
radio data. We report the discovery of the missing southern counterpart to the bright northern RCW 89 region and identify a foreground X-ray source that may be a previously unidentified SNR candidate. Imaging and spectroscopy with XMM-Newton and eROSITA reveal the shell properties of MSH 15-52 and suggest that both the southern and northern shell-like structures are consistent with shocked interstellar medium associated with the forward shock, while their low ionization timescales and possible hard power-law components indicate possible influence from particle injection or additional heating by the
pulsar wind nebula (PWN) jets. New Chandra spectral maps of the southern jet reveal a region of hard non-thermal emission, with a
photon index of approximately 1.6, suggesting interaction between the PWN and the reverse shock and possible re-acceleration of the
pulsar outflow. Spatially resolved spectroscopy of the RCW 89 northern clumps reveals high-velocity, metal-rich ejecta with enhanced Ne and Mg abundances. Comparison with core-collapse nucleosynthesis models favors a massive progenitor with an initial mass of approximately 29 solar masses in one-dimensional yield models, while asymmetric explosion models show that lower-mass progenitors can also reproduce the observed abundance ratios. Our study supports a picture in which RCW 89 is part of a larger asymmetric SNR shell interacting with energetic
pulsar jets, making the system a valuable laboratory for probing
pulsar-PWN-SNR interaction.
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All authors Lingxiao Dang, Isabel Sander, Samar Safi-Harb, Christopher Fryer
Solar and Stellar Astrophysics
What powers the most energetic flares in the Kepler field? Revisiting the superflaring star KIC 2852961
Zs. Kővári, B. Seli, L. Kriskovics et al. (+11 more)
Flare activity in red giants is quite common when continuously monitored with high-precision space photometry. In fact, the most powerful
flares, also known as "superflares" have been observed on red giant
stars. KIC 2852961 is a red giant
star producing the highest-energy
flares in the Kepler field, and is also known for its large-amplitude starspot-induced light variations. Our goal is to find out what causes the extreme
flare activity and
flare energies in this
star. For our investigations, we use ground-based spectroscopic measurements and space photometric data, which we process using standard tools. We also collect relevant data from databases of large surveys such as Gaia. Our new radial velocity data confirm that the red giant
star is part of a close binary system, in which tidal forces play a crucial role in controlling the
evolution of the binary system. Our results show that tidal
evolution has driven the system close to orbital circularization and rotational synchronization, but it did not completely constrain the differential rotation of the red giant, in which the
magnetic dynamo can operate extremely efficiently. We find that high-energy (super)
flares are primarily controlled by the internal
magnetic activity of the active giant component, rather than phase-dependent interactions with the secondary
star. The large spot-induced rotational light modulations indicate extensive starspots that can store enormous amounts of
magnetic energy. This provides the conditions for the formation of extremely large
flares, confirming the close relationship between large spot coverage and high
flare energies and/or frequency. Behind all this, differential rotation may play a dual role in the
flare activity of KIC 2852961: it contributes both to the formation of large starspots and to the shearing and twisting of coronal
magnetic fields that can power energetic superflares.
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All authors Zs. Kővári, B. Seli, L. Kriskovics, K. Oláh, P. Odert, M. Leitzinger, B. Schmercz, K. Vida, R. Greimel, B. Cseh, A. Görgei, T. Granzer, P. Sági, M. Weber
Solar and Stellar Astrophysics
Metallicity does not reorder line-to-line sensitivity to granulation in solar-like stars
Dušan Vukadinović, Sowmya Krishnamurthy, Valeriy Vasilyev et al. (+2 more)
Stellar granulation imprints line-dependent wavelength shifts and profile variations that limit the precision of radial velocity (RV) measurements used for
exoplanet detection and characterization. Understanding how the sensitivity of individual spectral lines to granulation depends on stellar parameters is therefore essential for mitigating granulation-induced RV signals. Here, we investigate the effect of
metallicity using MURaM 3D magnetohydrodynamic simulations of stellar granulation including a small-scale dynamo for
metallicities $\mathrm{M/H}=\{-1.0,-0.5,0.0,0.3,0.5\}$. We synthesize spectra of neutral and ionized lines spanning a broad range of lower excitation potentials and transition probabilities using the MPS-ATLAS code, assuming local thermodynamic
equilibrium. We quantify the sensitivity to granulation using the continuum-intensity-weighted standard deviations of the line centre-of-
gravity wavelength and equivalent width, denoted by $\sigma_\lambda$ and $\sigma_W$, respectively. Both metrics increase systematically with
metallicity at disc centre owing to the combined effects of more vigorous convection and
metallicity-dependent changes in the line opacity. We find that the correlation between the solar ($\mathrm{M/H}=0.0$) and non-solar sensitivity metrics remains high from the disk center to the stellar limb. This indicates that the relative ordering of line sensitivities is robust against changes in viewing angle and
metallicity. Consequently, line masks calibrated on the solar spectrum can be reliably applied to radial-velocity measurements of
stars with non-solar
metallicities, provided they have solar effective temperature and surface
gravity.
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All authors Dušan Vukadinović, Sowmya Krishnamurthy, Valeriy Vasilyev, Veronika Witzke, Andrew Collier Cameron
Solar and Stellar Astrophysics
Probing Massive Star Formation with Intrinsic Multiplicity Constraints from TESS Eclipsing Binaries
Jasmine Vrancken, Alex Kemp, Andrew Tkachenko et al. (+2 more)
Massive
stars play a central role in stellar and galactic
evolution as progenitors of
supernovae,
neutron stars, black holes, and gravitational wave sources. Despite their importance, the dominant formation mechanisms of massive binaries remain poorly constrained observationally. We aim to use a large, homogeneous sample of eclipsing binaries to observationally constrain binary formation across a wide range of primary masses and test predictions from various formation scenarios. We combine photometric time series data from TESS with distance measurements from Gaia DR3 and near infrared photometry from 2MASS to analyze an all-sky sample of eclipsing binaries. By accounting for observational and
geometric selection effects, we derive bias corrected estimates of the binary fractions and orbital parameter distributions across different mass bins. We derive bias corrected binary fractions and bias corrected distributions of orbital period and radius-to-separation ratio for systems spanning primary masses from 1.1 Msun to 47 Msun. For primary masses up to 5 Msun, the observed distributions show close agreement with theoretical predictions for systems formed via disk fragmentation followed by migration. At higher masses, we observe an apparent deficit of very short period systems relative to theoretical expectations, although this regime is also expected to be affected by incompleteness. Overall, the observed properties exhibit a gradual transition across the full range of primary masses. Within the orbital period range accessible to our sample, the results do not require a sharp transition in binary properties between F- and O-type
stars. The observed continuity is consistent with disk fragmentation followed by migration acting across a broad range of stellar masses, although the present data do not uniquely require this formation pathway and alternative channels may also contribute.
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All authors Jasmine Vrancken, Alex Kemp, Andrew Tkachenko, Conny Aerts, Hugues Sana
Instrumentation and Methods for Astrophysics
A Coherent Harmonic Summing Pulsar Search Code
Scott M. Ransom
Pulsars have narrow pulses, so their signals spread over many harmonics in a
Fourier transform. Standard
pulsar searches add the powers of those harmonics and discard their phases, which throws away the pulse shape and some of the signal. Folding the time series at each trial period keeps both, but is expensive even with the Fast Folding
Algorithm (FFA). We describe CoherentSearch.jl, an open-source Julia code that reconstructs the pulse profile at every trial
spin frequency directly from the
Fourier transform. It interpolates the complex amplitudes of typically 60 harmonics, inverse transforms them into a profile, and tests that profile against boxcar templates of many widths. Because the input spectrum is normalized, the noise in every profile is known in closed form, so one threshold gives one false-alarm rate across the whole search. In an injection study of over 860,000 simulated
pulsars at a matched false-alarm rate, the new search recovers 76% of the
pulsars in white noise, against 64% for riptide's FFA in its recommended configuration and 42% for PRESTO's accelsearch, and its threshold does not move under red noise. On one CPU core it is 1.4-2.2 times faster than riptide at matched frequency coverage, it scales to 27 times faster on 48 cores, and modern GPUs run it up to nine times faster than a 20-core workstation.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Nonreciprocal black holes with primary hair in beyond Horndeski gravity: Exact solutions and stability
Sebastian Bahamonde, Theodoros Nakas and Simon Iteanu
We develop a novel systematic method for constructing exact, static, and asymptotically flat black-hole solutions in shift-symmetric and $Z_2$-symmetric beyond Horndeski theories. In contrast to previous studies, our approach does not rely on the restrictive reciprocal condition $g_{tt}g_{rr}=-1$, allowing for more general geometries characterized by two independent metric functions. The resulting solution space contains two qualitatively distinct types of hair originating from different branches of the theory. One branch is characterized by khronometric hair, while the other by genuine scalar hair. In both, the scalar profile defines a nontrivial preferred foliation, but the shift-
symmetry Noether current and the associated propagating degree of freedom are trivial for the former and nonvanishing for the latter. Focusing mainly on the second branch, we derive several distinct families of exact black-hole solutions. In general, these solutions are singular and exhibit primary scalar hair associated with an independent scalar charge. Nevertheless, we demonstrate that they can be regularized to yield regular black-hole or solitonic configurations, for which the scalar hair becomes secondary. We further investigate the stability properties of these solutions under linear perturbations by analyzing the axial sector and the monopole $(\ell=0)$ mode of the even-parity sector. For representative solutions with scalar hair, the perturbative analysis provides evidence for linear stability under the modes considered.
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Earth and Planetary Astrophysics
Gravitational Microlensing
Aikaterini Vandorou and Stela Ishitani Silva
Gravitational microlensing is a unique
planet-detection method that does not rely on detecting light from the host
star or
planet. Instead,
planets are discovered when their gravitational field perturbs the light coming from a distant source. The mechanics of this method offer several advantages. It has the ability to detect wide-orbit
planets of various masses around host
stars of different types, at and beyond the system's snow line. Thus, microlensing complements the other detecting techniques that are more sensitive to close-orbit or high-mass
planets. In this Chapter, we review the microlensing method and discuss how the physical properties, such as mass and distance, can be extracted from the microlensing light curve or from additional high-angular resolution observations. Microlensing is essential for the broader context of
exoplanet demographics, as it can place constraints on
planets, in wide orbits, beyond the snow line. Studying this parameter space can help us unravel the details of
planet formation and how our own Solar System formed. Lastly, we provide an example of how to model a light curve and obtain accurate physical parameters for the host and
planet.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Holographic dark energy from generalized entropies and extended infrared cut-offs
Ke Chen, Simone D'Onofrio, Sergei D. Odintsov et al. (+1 more)
We study holographic dark energy models constructed from generalized
entropy functionals and local infrared cut-offs. Three
entropies (Barrow and the three and five-parameter generalized
entropies) are each combined with the Granda-Oliveros (GO) cut-off and two extensions, one adding a $\gamma H^{-2}$ term and one a $\gamma \ddot{H}/H$ term, the latter raising the dark-energy
evolution equation to second order. The nine resulting models are constrained against DESI DR2 BAO, Pantheon+ and a Planck compressed CMB likelihood through an MCMC analysis, and compared using the Akaike and
Bayesian information criteria. The Hubble constant is stable across all models. The $H^{-2}$ term is unconstrained in every case, as it becomes relevant only in the far future, and never improves on the GO cut-off. The $\ddot{H}/H$ term, instead, is tightly constrained for Barrow and $S_5$, where it improves the fit substantially, but not for $S_3$. The best fit is obtained for Barrow
entropy with the $\ddot{H}/H$ cut-off, yet the Barrow exponent remains compatible with zero in all cases. The data thus favour a higher-order infrared cut-off, while showing no significant evidence for a departure from the Bekenstein-Hawking area law. We also investigate the dark energy equation of state (EoS) of $S_3$ and $S_5$, discovering quintessence-like behavior and phantom crossing.
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All authors Ke Chen, Simone D'Onofrio, Sergei D. Odintsov, Tanmoy Paul
High Energy Astrophysical Phenomena
Radio Continuum Study of One of the Brightest Large Magellanic Cloud Supernova Remnants N 132D
Rami Z. E. Alsaberi, Zachary J. Smeaton, Miroslav D. Filipovic et al. (+5 more)
We present a new
radio continuum study of the Large Magellanic Cloud
supernova remnant N 132D using observations from the Australia
Telescope Compact Array (ATCA) and MeerKAT. The
radio morphology shows a clear spatial correlation with the X-ray emission in the central and left regions of the remnant, as well as in the right portion of the shell, indicating a close connection between the thermal and non-thermal
plasma components. Polarisation measurements reveal predominantly radial
magnetic fields, with mean fractional polarisations of 1.2 per cent, 3.0 per cent, and 4.0 per cent at 2100, 5500, and 9000 MHz, respectively. There is also a complex structure in the Faraday Depth spectrum, showing a double-peaked profile that indicates regions with differing magnetisation properties or varying
magnetic field geometry. The rotation measure derived from ATCA data has an average value of ~2 rad m^-2, with a maximum of ~338 rad m^-2. We estimate a constant partition
magnetic field of ~90 microG and a minimum energy of 3 x 10^50 erg, which is in a constant partition between the energy density of electrons and the energy density of the
magnetic field. The integrated
radio spectrum follows a power law with a spectral index of -0.74 +- 0.01. These results provide new constraints on the
magnetic field structure and energetic properties of N 132D and offer insight into particle acceleration and shock
evolution in young
supernova remnants.
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All authors Rami Z. E. Alsaberi, Zachary J. Smeaton, Miroslav D. Filipovic, Roland Kothes, Hidetoshi Sano, Ahmed H. Abdullah, Dejan Urosevic, Sanja Lazarevic
Astrophysics of Galaxies
Measuring radial flows in disc galaxies
Yi He, Filippo Fraternali, Pavel E. Mancera Piña et al. (+1 more)
Numerous theoretical studies suggest that gas
accretion from the intergalactic medium is essential to feed
star formation in
galaxies throughout
cosmic time. However, the mechanism of gas
accretion remains poorly understood, as direct evidence is lacking. In some models, gas
accretion is expected to take place in the outer discs of
galaxies, from where it should be transferred to the inner
star-forming discs through radial flows. Finding such flows and quantifying them, therefore, opens the possibility of inferring the detailed properties of the accreting gas. Unfortunately, detecting radial flows is challenging due to the large disparity between radial and rotational velocities. Additionally, the distortions in velocity fields produced by these flows resemble the effects of warped structures, further complicating their quantification. To address this, we have developed a new methodology to measure axisymmetric radial velocities in disc
galaxies. Relying on the 3D kinematic fitting software \texttt{$^{\rm 3D}$Barolo}, we have designed a dedicated workflow to measure axisymmetric radial motions in disc
galaxies and to obtain robust uncertainty estimates through a bootstrapping approach. We validated this approach using realistic axisymmetric mock
galaxies as well as a small sample of `observed' Milky Way-like
galaxies drawn from the TNG50 hydrodynamic simulation. These tests demonstrate that our method works well and is capable of overcoming the degeneracy between radial motions and warps. The TNG50
galaxies we analysed have large regions in their discs with non-axisymmetric inflows and outflows, but they show, on average, no global trend of coherent radial flows.
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All authors Yi He, Filippo Fraternali, Pavel E. Mancera Piña, Enrico M. Di Teodoro
Astrophysics of Galaxies
Isotopic ratios as probes of star formation and the origin of molecular gas in the Central Molecular Zone
Laura Colzi
The Central Molecular Zone (CMZ) contains most of the dense molecular gas in the Milky Way but forms
stars at a surprisingly low rate. Isotopic ratios provide a unique tool to investigate both the local physical conditions and the nucleosynthetic history of this gas. I summarize recent isotopic studies toward the molecular cloud G$+$0.693$-$0.027. Deuterium fractionation (D/H ratios) reveals a cold ($T_{\rm kin}\lesssim30$ K), relatively quiescent gas component embedded within the otherwise warm and turbulent CMZ, indicating that the earliest stages of
star formation can survive in this extreme environment. I also present new $^{12}$C/$^{13}$C measurements from HC$_3$N and HC$_5$N, including the first constraints from doubly substituted $^{13}$C isotopologues. After accounting for isotopic fractionation with astrochemical models, the inferred elemental ratio ($\sim37$–48) exceeds the canonical CMZ assumed value ($\sim$20), supporting a scenario in which the Galactic center is replenished by less chemically processed gas flowing inward along the Galactic bar.
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