Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
Signal-to-Noise Ratio Contours for LISA
Kai Schmitz and Joseph D. Romano
The
Laser Interferometer Space
Antenna (LISA) will search for a
stochastic gravitational-wave (GW) background at millihertz frequencies, from both astrophysical and cosmological sources, and thereby open a new chapter in GW astronomy. In the literature, LISA's sensitivity to prospective GW background (GWB) signals is often quantified in terms of an expected signal-to-noise ratio (SNR) assuming perfect knowledge of the detector noise. The commonly employed expression for the SNR is, however, valid only in the limit of a weak GWB signal, which renders a large number of SNR values reported in the literature inaccurate. In this paper, we address this issue by deriving for the first time an expression for the expected optimal SNR of a LISA auto-correlation measurement that is valid at arbitrary signal strength. Based on our generalized expression, we conclude that LISA data worth an observing time of T_obs across the frequency band from f_min to f_max will never yield an SNR in excess of SNR_max = sqrt(T_obs(f_max-f_min)), which evaluates to SNR_max <~ 10^4 for typical mission parameters. We illustrate our findings in terms of generalized power-law-integrated (PLI) sensitivity curves at different SNR levels, i.e., LISA SNR contour lines in plots of the GW energy-density power spectrum. In contrast to earlier work on PLI sensitivity curves, we notably find that the LISA SNR contours are bounded from above, approximately by the LISA strain noise curve multiplied by a factor of Euler's number e. For GWB signals not much weaker than this range, the expected SNR for a LISA auto-correlation measurement needs to be evaluated based on our new expression. Our numerical results for the LISA SNR contours are available on Zenodo [https://doi.org/10.5281/zenodo.21275527].
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High Energy Astrophysical Phenomena
Exploring the effect of mixing in Low-Luminosity Type IIp Supernovae by modeling SN 2024abfl
Akshith Karri, Abigail Polin and Paul Duffell
Low-luminosity Type IIp
supernovae (LLSNe) are SN IIps with peak magnitudes > -15.5 and plateau magnitudes between -13.5 and -15.5 in the V band. SN 2024abfl is an LLSN with a unique light curve, particularly the steep drop in luminosity observed after the plateau phase makes it an interesting candidate for modeling core-collapse
supernova mechanisms. Using a custom pipeline involving MESA and STELLA, we investigate the possibility of suppressed ejecta mixing as a cause of the steep drop-off from the plateau phase. We find that turning off mixing mechanisms during shock breakout can mimic the distinct flat plateau and steep luminosity drop into the radioactive tail of the light curve while using previously proposed progenitor mass, radius and explosion energy parameters. Using these results as a proof-of-concept, exploring the effects of limited mixing in LLSNe candidates could give us better insight into how they differ from Typical Type IIp SNe.
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Astrophysics of Galaxies
Effects of low resolution on the column density PDF of molecular clouds
Yuping Tang, Q. Daniel Wang, Grant W. Wilson et al. (+2 more)
Observational resolution significantly impacts the interpretation of column density probability distribution functions (N-PDFs) in molecular clouds, which are essential for understanding turbulent structures and
star formation processes. This study quantifies how low spatial resolution truncates the high-density power-law tails of N-PDFs by simulating distant observations (2-10 kpc) of 17 local massive molecular clouds/regions using Herschel-based column density maps. We propose a parameter-free model, assuming proportional
embedding of dense regions within lower-density gas, to predict the truncation column density where the survival function equals the beam-to-threshold area ratio. Comparisons with simulations show good agreement, with deviations up to 0.3 dex attributed to cloud multiplicity in large complexes and flatter power-law tails in coherent structures. Characteristic cloud scales, derived from Delta-variance spectra, indicate that global smearing dominates when beam sizes exceed these scales. We further develop a reverse method to recover the intrinsic high-density tail from low-resolution data. Our findings link N-PDF shapes to morphologies, suggesting that feedback-compressed extended structures resist smearing, while multiplicity accelerates truncation. These insights caution against biases in N-PDF decompositions and provide a framework for correcting resolution effects in distant cloud studies, enhancing constraints on
star formation theories.
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All authors Yuping Tang, Q. Daniel Wang, Grant W. Wilson, Xing Lu, Jinhua He
Instrumentation and Methods for Astrophysics
Methods of Observing and Characterising the Ionosphere with SKA-Low
John Morgan, Biagio Forte, Kshitija Deshpande et al. (+2 more)
The ionosphere and its behaviour critically affects ground-based
radio instruments at low frequencies, and
radio interferometry has been used as a probe of the ionosphere since the earliest days of
radio astronomy. In this chapter, we aim to give an overview of the ionosphere and its salient properties in the mid-latitudes where the SKAO instruments are located. We provide a comprehensive review of its impact on the astrophysical
radio signals which traverse it. We then focus on the ionosphere as a phase screen, and the many ways in which the ionospheric structure can be measured using a low-frequency interferometer such as SKA-Low. Our aim here is to provide the broadest possible spectrum of measurement approaches. We place particular emphasis on the wide range of innovative approaches that have been developed for SKA precursors and pathfinders over the last decade, however we also draw
attention to other approaches, some untested, that appear in the literature. Next, we consider an innovative approach for deducing the detailed physical conditions in the ionosphere from SKA observables via iterative simulations with a sophisticated physical model from which the interferometric response can be forward-modelled. This approach has proven extremely successful for interpreting large scale observations in the complex polar region of the ionosphere, and we discuss how it can be applied to the SKA-Low. Finally, we provide a summary of the technical requirements which will ensure viability of the various techniques discussed.
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All authors John Morgan, Biagio Forte, Kshitija Deshpande, Andrzej Krankowski, Mario Bisi
Cosmology and Nongalactic Astrophysics
A semi-analytical approach to cosmic void evolution
A.N. Baushev, A.G. Nikiforov and M.V. Barkov
We present a theoretical study of the non-linear
evolution of
cosmic voids – underdense regions that occupy a large fraction of the observable Universe. We model a void as an isolated homogeneous spheroidal (axisymmetric) ellipsoid embedded in a homogeneous $\Lambda$CDM universe. Starting from a small initial density contrast at
redshift $z=500$, we numerically integrate the equations of motion for the ellipsoid semi-axes and follow their
evolution to the present epoch. We examine the anisotropic expansion of the void and the corresponding change in its shape, characterised by the eccentricity $e$. We find that the void non-sphericity always decreases, but rather slowly: the eccentricity drops from $e\approx0.87$ at $z=500$ to $e\approx0.81$ at $z=0$. Thus the void becomes rounder but remains aspherical throughout the
evolution. The
evolution and final value of the void underdensity are virtually independent of the void's eccentricity. The nonlinearity of void
evolution becomes apparent very early: a ten percent deviation from the linear regime occurs already at $z\simeq8$, when $\varepsilon = \Delta\rho/\rho\sim10\%$. Notably, our calculations show that the majority of voids are not strongly underdense and contain a significant amount of matter, $\mu>0.5$.
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High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Relativistic Mean Field Approach with Chiral Symmetry Breaking and Quark Confinement in the light of Astrophysical Observations
Bikram Keshari Pradhan, Mohamad Chamseddine, Jérôme Margueron et al. (+4 more)
We perform a
Bayesian analysis of a relativistic mean-field approach, which is an implementation of the
chiral confining model with both
chiral symmetry breaking and confinement effects, and which was recently proven to reproduce well the ground state properties of finite
nuclei. We additionally explore the impact of couplings between $\rho$ and $\omega$
mesons as well as a non-linear $\omega$ coupling. Our models are simultaneously constrained by
nuclear matter properties near saturation density, multi-messenger
neutron star astrophysical observations, and/or
lattice QCD predictions of the nucleon mass. It exhibits tension in simultaneously reproducing the $\sim 2M_{\odot}$ massive NS and the
tidal deformability inferred from GW170817. We show that an additional $\omega\rho$ coupling, favored by Bayes factor analysis, substantially alleviates this tension, while adding a non-linear $\omega$ self-interaction is not necessary for the RMF-CC model. Owing to the strong constraints on the scalar sector imposed by
chiral dynamics and the softening of the equation of state at high densities induced by our treatment of confinement, the RMF-CC approach favors stiff equations of state. Since we do not consider phase transition in the core of
neutron stars, this stiffening is obtained with large values of the incompressibility modulus of about $\sim300$ MeV. We finally compare the well-known RMF model with RMF-CC models with the same constraints, and we obtain a preference for the RMF model in the absence of a phase transition in the core of
neutron stars.
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All authors Bikram Keshari Pradhan, Mohamad Chamseddine, Jérôme Margueron, Hubert Hansen, Guy Chanfray, Jean-Paul Ebran, Elias Khan
Solar and Stellar Astrophysics
Collisionless and collisional kinetics of a plasma atmosphere with spatially and temporally intermittent heating at its base
Luca Barbieri, Pascal Démoulin and Filippo Pantellini
The
solar corona exhibits a pronounced temperature inversion, with
plasma temperatures increasing by nearly two orders of magnitude from the chromosphere to the corona. We investigate how spatially sparse and temporally intermittent
stochastic heating at the base of the transition region shapes the temperature and density structure of coronal loops within a kinetic framework.
Stochastic thermal boundary conditions and surface coarse graining are introduced. Analytical solutions are derived in the collisionless limit for heating-event time scales shorter or longer than the particle crossing time, and Coulomb collisions are incorporated through a reduced kinetic model describing the thermalization of suprathermal particles. In the short-time-scale regime, spatial filling factor and temporal intermittency combine into a single effective parameter controlling the suprathermal population, producing a transition region and a hot corona both within individual loops and after coarse graining. Collisions preserve this thermal structure while reducing the coronal density through progressive thermalization. In the long-time-scale regime, individual loops are nearly isothermal and the temperature inversion emerges only after coarse graining, depending solely on the spatial filling factor. Here, Coulomb collisions and optically thin radiative losses have only minor effects, while density and temperature profiles remain broadly consistent with coronal observations. These results show that sparse, intermittent heating naturally generates suprathermal particle distributions and reproduces the observed thermal structure of the
solar corona within a kinetic framework, highlighting the different sensitivity of the two regimes to collisional effects.
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Solar and Stellar Astrophysics
Successive Coronal Jets as Novel Facilitators for Filament Oscillation and Eruption
Chengrui Zhou, Chun Xia, Wentai Fu et al. (+2 more)
Solar filament eruptions are central to coronal mass ejections and space weather, yet their triggering mechanisms remain a fundamental open question. In particular, the early-stage that drives a
magnetic flux rope toward instability and its observable signatures are poorly understood. Here, combining multi-instrument observations, we report successive coronal jets impacting a filament, causing its gradual rise and oscillations with growing amplitude and period. When the filament reaches the height where the decay index exceeds the
torus instability threshold, the rapid filament eruption commences. This filament eruption is reproduced by magnetohydrodynamic simulations, in which successive thermal jets disturb a stable filament in a
magnetic flux rope and excite oscillations together with the eruption of the filament. As the filament rises to erupt, the restoring forces for the oscillation progressively weaken, which naturally leads to an increase of the oscillation amplitude and period. Our results demonstrate the growing oscillations as one of the observable precursors for filament eruptions, enhancing our ability to predict
solar eruptions.
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All authors Chengrui Zhou, Chun Xia, Wentai Fu, Hechao Chen, Qiaoling Li
Astrophysics of Galaxies
Multiple populations along the asymptotic giant branch: a Gaia+APOGEE study of 22 Galactic globular clusters
Emanuele Dondoglio, A. P. Milone, A. F. Marino et al. (+9 more)
We present an investigation of multiple
stellar populations along the asymptotic
giant branch (AGB) in 22 globular clusters (GCs), exploiting APOGEE spectroscopy combined with AGB selection based on
Gaia color-magnitude diagrams. Using light-element abundances ([C/Fe], [N/Fe], [Mg/Fe], and [Al/Fe]), we disentangle first- (1P) and second- (2P) populations along the AGB. We derive their fractions in the AGB for the largest sample of GCs to date, finding that the 1P fraction decreases with cluster mass, as in other evolutionary phases. By comparing AGB and red
giant branch (RGB), we define a quantitative criterion to identify clusters affected by the AGB-manque phenomenon. We find that in nine GCs the most chemically extreme 2P
stars are underrepresented along the AGB, indicating that they fail to ascend this phase. Our classification is in agreement with previous studies and provides the first spectroscopic characterization of AGB multiple populations in eight GCs. We derive, for the first time, the radial distribution of AGB 2P
stars in four clusters. While NGC5024 and omegaCentauri show trends consistent with the RGB, NGC2808 and NGC7078 may exhibit an unexpected increase of the AGB 2P fraction at large radii, opposite to the RGB
stars. We present the first detailed spectroscopic characterization of anomalous AGB populations in NGC6656 and omegaCentauri, i.e. the populations enhanced in heavy elements compared to the bulk of 1P and 2P. In both clusters, anomalous
stars show a more pronounced AGB-manque signature than 2P
stars, with the fraction of the most Mg-poor and Al-rich AGB dropping compared to the RGB, possibly due to enhanced He and/or increased RGB mass loss. We report the first detection of iron inhomogeneities among 1P AGB
stars in NGC5272, with a spread consistent with the RGB one. This extends the presence of iron variations to the most evolved
stellar phase studied so far.
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All authors Emanuele Dondoglio, A. P. Milone, A. F. Marino, G. Cordoni, M. V. Legnardi, T. Ziliotto, R. Asa'd, A. Mastrobuono-Battisti, F. Muratore, E. Bortolan, E. P. Lagioia, M. Tailo
Astrophysics of Galaxies
Milky Way Near Twins (MWNeTs). I. A Hierarchical Framework for Identifying Candidate Evolutionary Counterparts of the Milky Way
I.B. Vavilova, A.M. Dmytrenko, D.V. Dobrycheva et al. (+8 more)
Searches for Milky Way analogues traditionally rely on a limited set of present-day global properties. However,
galaxies with similar morphology,
stellar mass,
star-formation rate, luminosity, and bulge-to-total ratio may have experienced substantially different assembly, secular,
nuclear, and environmental histories. We introduce Milky Way Near Twins (MWNeTs) as
galaxies resembling the Milky Way (MW) in their present-day properties and exhibiting observational signatures consistent with broadly similar evolutionary pathways. We aim to extend parameter-based searches towards evolutionary similarity. We propose seven stages: local environment, isolation criterion, and
cosmic-web context; morphological and structural constraints; a MW-compatible
nuclear state; global spectrophotometric and dynamical constraints; panchromatic spectral-energy-distribution similarity; rotation-curve similarity; and evolutionary fingerprints and fossil tracers. Each stage adds physically motivated constraints, progressively refining the candidate population and strengthening its assessment. For the first time, we formulate MWNeTs as a physically motivated class and establish a hierarchy explicitly distinguishing present-day compatibility from evidence for evolutionary similarity. A companion paper presents the observational application to NGC~3521, NGC~2903, UGC~11487, and CGCG~047-026. The framework is inherently iterative: the MW provides the reference, while near twins offer external laboratories for investigating aspects of
Galactic formation and
evolution inaccessible from our internal viewpoint. It connects
Galactic astronomy, extragalactic astronomy, and cosmology through a comparative approach to testing broadly similar evolutionary pathways.
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All authors I.B. Vavilova, A.M. Dmytrenko, D.V. Dobrycheva, P.N. Fedorov, I.O. Izviekova, V.P. Khramtsov, O.V. Kompaniiets, O.N. Kukhar, O.S. Pastoven, O. Sergijenko, A.A. Vasylenko
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Precision three-Dimensional Atmospheric Neutrino Flux Calculation Based on Honda Flux Model
Jie Cheng, Yu-Feng Li and Liang-Jian Wen
We present a comprehensive three-dimensional atmospheric
neutrino flux calculation based on the well-recognized simulation framework develeped by Honda and his collaborators, incorporating for the first time the
muon propagation inside the Earth and its subsequent decay or
nuclear capture. Other updates of essential input models include: the AMS02-based primary
cosmic ray model, IGRF2020 geomagnetic field, and
muon-recalibrated hadronic interaction model. The calculation covers seven detector sites across diverse geomagnetic environments, spanning 10~MeV to $10^4$~GeV. Significant site-dependent differences appear at $E_\nu < 10$~GeV, with $\nu_\mu$ flux at IceCube approximately twice that at JUNO below 1~GeV. Compared to HKKMS15, deviations of 2%–10% are attributed to the updated input models. Below 100~MeV, we present precise flux results, revealing that
muon propagation contributes a globally significant component to the low-energy
neutrino flux at all sites, with an approximately site-independent absolute increment. The hadronic uncertainty is re-estimated across the energy range using the updated hadronic interaction model, with significant reduction of the systematic error compared to previous calculations. These results provide essential inputs for
neutrino oscillation and rare-event search experiments including JUNO, Super-Kamiokande/Hyper-Kamiokande, DUNE, KM3NeT/ORCA, and IceCube, as well as direct dark matter detection experiments facing the
neutrino fog.
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Instrumentation and Methods for Astrophysics
Development of a Raman Lidar for the Southern Site of the Cherenkov Telescope Array Observatory
Patrick Brun, Omar Gabella, Stephane Rivoire et al. (+1 more)
The future CTAO will reach a sensitivity and energy resolution never obtained until now by any other high-energy gamma-ray experiment. Studying the atmospheric conditions during the CTAO observations, namely the extinction and backscatter coefficients, permits a very precise evaluation of the atmospheric UV absorption, a parameter that directly affects the energy and flux spectra of the CTAO-studied sources. This paper describes the motivation for the LUPM Raman
Lidar system, a
Lidar specifically designed to fulfill the CTAO requirements for the south site in Chile. Preliminary results obtained during a two-year campaign at the OHP Observatory are presented. Our results include estimations of the extinction, back-scatter, and
Lidar ratio at both 355 and 532 nm and confirm the conformity of our prototype to the CTAO requirements
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All authors Patrick Brun, Omar Gabella, Stephane Rivoire, George Vasileiadis
Cosmology and Nongalactic Astrophysics
Lambda as a Probe of Lensing Consistency
Yuan Shi, Li Cui and Carlo Giocoli
We introduce a framework to identify the radial transition in mass reconstruction reliability between strong and weak gravitational
lensing in
galaxy clusters. In weak
lensing reconstruction, the convergence recovered from the reduced shear is subject to the mass-sheet degeneracy. We demonstrate that the degeneracy itself can serve as an indicator of the reconstruction reliability, and introduce a spatially resolved parameter $\lambda(r)$ to characterize this as a function of radius. We validate this approach on simulated clusters with realistic observational noise, and show that $\lambda(r)$ naturally quantifies the relative reliability of the two probes. Furthermore, when the global mass-sheet parameter $\lambda$ is constrained directly using strong
lensing information, the tightest constraints arise where the two probes achieve comparable precision. This provides a quantitative basis for joint strong and weak
lensing mass reconstruction.
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Astrophysics of Galaxies
Subaru meets JWST: A Direct Measurement of Ly$\boldsymbol{\alpha}$ Escape Fraction at $\boldsymbol{z\simeq6.2}$ with Dual Narrow-Band Imaging
Shunta Shimizu, Nobunari Kashikawa, Ryo Emori et al. (+15 more)
We present a direct measurement of the Ly$\alpha$ escape fraction, $f^{\rm Ly\alpha}_{\rm esc}$, for H$\alpha$ emitters (HAEs) at $z\simeq6.2$ in the JWST CEERS field by combining JWST/NIRCam F470N imaging with Subaru/HSC NB872 imaging. This unique pair of narrow-band filters enables the simultaneous measurement of Ly$\alpha$ and H$\alpha$ fluxes from
galaxies during the epoch of reionization (EoR). We select 84 HAEs from F470N excesses, among which 56 have reliable NB872 photometry and 19 are detected in Ly$\alpha$ at $>2\sigma$ significance. The completeness-weighted stack of the HAE sample yields a median $f^{\rm Ly\alpha}_{\rm esc}$ at $z\simeq6.2$ of $0.106^{+0.066}_{-0.044}$, which is in good agreement with recent measurements at similar
redshifts. We further find no significant dependence of the stacked $f_{\rm esc}^{\rm Ly\alpha}$ on the lower limit of H$\alpha$ luminosity over the luminosity range probed by our sample. If Ly$\alpha$ escape traces Lyman continuum leakage, this may suggest that relatively luminous HAEs, rather than only the faintest
galaxies, can provide an important contribution to the ionizing
photon budget during the EoR. For individual
galaxies, $f^{\rm Ly\alpha}_{\rm esc}$ positively correlates with Ly$\alpha$ equivalent width and negatively correlates with the UV continuum slope $\beta$ and the rest-frame UV size, while no significant correlation is found with SED-derived $E(B-V)$, or rest-frame optical size, although these trends are based on a limited sample. These results suggest that the
galaxy-to-
galaxy variation in $f_{\rm esc}^{\rm Ly\alpha}$ is more closely linked to compact, low-attenuation
star-forming components traced by the UV continuum than to global
dust attenuation or the overall
stellar structure.
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All authors Shunta Shimizu, Nobunari Kashikawa, Ryo Emori, Junya Arita, Kohei Inayoshi, Akio K. Inoue, Kei Ito, Satoshi Kikuta, Kentaro Koretomo, Mariko Kubo, Yongming Liang, Rieko Momose, Kentaro Nagamine, Masafusa Onoue, Rhythm Shimakawa, Yoshihiro Takeda, Hisakazu Uchiyama, Takehiro Yoshioka
Earth and Planetary Astrophysics
A search for circumstellar gas in pre-main-sequence debris discs using absorption spectroscopy
Karolina M. Szewczyk, Daniela P. Iglesias and Olja Panić
Gas in debris discs is thought to be either inherited from the protoplanetary stage or released from the solid, rocky content of planetesimal belts. Its presence can impact planetary atmospheres and their potential for habitability, which stresses the need to ascertain its origin and composition. Most detections to date are around main-sequence
stars, with only a few gas-bearing debris discs identified around pre-main-sequence
stars, mainly through millimetre CO line searches. We investigate narrow gas absorption features superimposed on the photospheric Ca II K & H and Na I D1 & D2 lines in a sample of 125 pre-main sequence and 5 relatively young (<17Myr)
stars. All
stars are associated with IR excess emission indicative of presence of a debris disc. By comparing their residual spectra (photosphere-subtracted) to those of nearby
stars, interstellar cloud velocities, and
stellar radial velocities, we test whether interstellar absorption is the culprit and ascertain circumstellar gas origin. Using these methods, out of the 130 targets, we identified two new gas-bearing debris discs: TYC7879-1373-1, which exhibits stable absorption, and HIP30414, which shows variable gas absorption features linked likely to ongoing
accretion. Both these systems are pre-main-sequence
stars younger than 5Myr. TYC6822-283-1 has absorption features of inconclusive origin. This study increases the number of currently known very young (<10Myr) debris discs with circumstellar gas to eight, paving the path to future systematic studies of objects caught in transition from protoplanetary to debris disc stages.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Probing Quadratically Coupled Ultralight Dark Matter with the Laser Interferometer Space Antenna
Xucheng Gan, Hyungjin Kim, Anna-Malin Lemke et al. (+1 more)
Ultralight dark matter can interact with Standard Model particles via gravitational and non-gravitational interactions. Through such interactions, it can leave distinctive signals in gravitational-wave experiments. In this work, we investigate signals induced by ultralight dark matter quadratically coupled to the Standard Model in the future space-borne gravitational-wave detector, the
Laser Interferometer Space
Antenna (LISA). Due to the quadratic nature of the coupling, dark matter signals appear at two distinct frequencies: the frequency corresponding to twice the dark matter mass, and frequencies below the typical dark matter kinetic energy. We analyze both contributions and show that LISA can surpass current constraints from terrestrial and astrophysical probes in certain mass ranges. We also find that dark matter signals in LISA are free from screening effects which significantly limit the sensitivity of terrestrial experiments.
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All authors Xucheng Gan, Hyungjin Kim, Anna-Malin Lemke, Andrea Mitridate
Instrumentation and Methods for Astrophysics
V. Bommier, B. Gelly and R. Douet
Context. THÉMIS was initially built as a calibration-free
telescope, with the polarisation analysis performed in F1 focus, before any oblique reflection. Recently, the
telescope was improved with installation of an Adaptive Optics apparatus. Aims. We would like to show you that it remains a calibration-free
telescope, even if the two beams able to provide the light polarisation, are now separated in front of the cameras only. Methods. This is obtained owing to an adaptation of all the oblique reflections along the ray path. Results. We present raw images taken across a sunspot, with three lines: two polarisable lines, which display the sunspot
magnetic field polarisation, linear and circular, and one unpolarisable line, which does not display any polarisation, which shows that the
telescope is essentially free of any instrumental polarisation, because, if this line had showed any polarisation, this polarisation would have been of instrumental origin. Those images were recorded on September 12, 2024. We also present vector
magnetic field, vector current density and vector Lorentz force maps obtained in July 2025, which are in accordance with previous results: circular currents wrapping spots clockwise about a positive polarity spot and counterclockwise about a negative polarity spot, and centripetal Lorentz force maintaining sunspots. Conclusions. As a result, THÉMIS remains a calibration-free
telescope.
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High Energy Astrophysical Phenomena
A Magnetar Engine and Circumstellar Medium Interaction: Synergistic Effects in Producing Superluminous Supernovae
Guang-Lei Wu, Yun-Wei Yu and Liang-Duan Liu
Superluminous
supernovae (SLSNe) are often modeled as being powered either by a central engine or by strong interaction with dense circumstellar material (CSM). These two mechanisms may be dynamically coupled if the ejecta interact with dense CSM while being energized by a newborn magnetar. We develop a semi-analytical hybrid model that follows the coupled dynamics, energy conversion, and radiative output of such systems. A rapidly rotating magnetar injects energy through a relativistic wind, inflating a hot bubble inside the expanding ejecta. Part of the injected energy is stored as radiation, while the rest is converted into bulk kinetic energy of the swept-up ejecta. At the same time, the outer ejecta collide with the surrounding CSM and form a circumstellar interaction (CSI) region. As the shock driven by the magnetar accelerates through the ejecta, it can catch up with the CSI region and take over the subsequent interaction with the unshocked CSM. The emergent light curves are therefore governed by the coupled effects of magnetar energy injection, shock heating, and radiative
diffusion. We show that this hybrid model can produce diverse SLSN light-curve morphologies, including luminous interaction-powered peaks, asymmetric post-peak declines, and late-time emission sustained by delayed leakage of magnetar-powered radiation. The model provides a plausible way to reduce the extreme nickel-mass or initial explosion-energy requirements often encountered in purely radioactive or purely interaction-powered interpretations.
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Astrophysics of Galaxies
CARPP: Parametric Radiative-Transfer Fitting of Molecular Cores from Dust Continuum Data
Yuchen Xing, Di Li, Nannan Yue et al. (+5 more)
The density profiles of dense molecular cores are important indicators of their physical and evolutionary states. Multi-wavelength
dust continuum data offers excellent constraints on the density profile of cores. Here we introduce CARPP (Core Analysis via Radiative Transfer and Profile Parameters), a publicly available fitting package that generates optimized core density and temperature profiles based on parameterized radiative transfer calculations. CARPP assumes spherical
symmetry and adopts physically motivated parametric forms for the density and temperature profiles, and uses
dust continuum data for fitting. Tests on synthetic data show that CARPP achieves high accuracy, namely averaged relative errors of CARPP's seven parameters being $<20\%$, when the data quality satisfies $\frac{\rm RMS \,\, noise}{[\rm peak \,\, flux]} < 0.025\times \frac{[r_0]}{\rm resolution} +0.05$, where $r_0$ is the core's characteristic radius. We select the low-mass core TMC-1C and the high-mass core Ori2-2 to demonstrate CARPP's performance on real data. It classifies TMC-1C as a Bonnor-Ebert sphere in near-hydrostatic
equilibrium, while Ori2-2 exhibits a power-law-dominated profile indicative of a collapsing envelope. This capability establishes CARPP as a powerful and versatile tool to classify the dynamical states of individual cores. It offers an optimal balance between physical fidelity and computational efficiency, serving as a practical, standardized alternative to both over-simplified SED analyses and complex, time-intensive 3D radiative-transfer modeling.
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All authors Yuchen Xing, Di Li, Nannan Yue, Zhiyuan Ren, Qizhou Zhang, Sihan Jiao, Xin Lyu, Jiawei Liu
Solar and Stellar Astrophysics
Beryllium enhancement in stars of the accreted Thamnos-2 system
Paolo Molaro, Piercarlo Bonifacio, Elisabetta Caffau et al. (+2 more)
Surveys of
Galactic halo stars have revealed numerous streams and substructures tracing
stellar populations accreted by the Milky Way. Among these,
Gaia-Sausage-Enceladus (GSE) and Sequoia are the most prominent, both associated with
dwarf galaxies accreted about 10 Gyr ago. We aim to measure beryllium abundances in nine
stars associated with Thamnos, a substructure possibly linked to Sequoia, following the discovery of a Be-rich
star BPM3066 by Monaco et al (2025). We used
Gaia photometry and parallaxes to compute ATLAS9 model atmospheres. Synthetic spectra were generated with Turbospectrum and used with MyGIsFOS in single-model mode to analyze UVES high resolution spectra. Four new
stars exhibit a significant beryllium overabundance. Moreover, the two known Be-rich
stars, HD 106038 and HD 132475, are also found consistent with Thamnos membership. Thus, all currently known Be-rich
stars appear associated with the Thamnos-2 structure. The Be enhancement is accompanied by elevated Si abundances, and we detect a correlation between Be and
neutron-capture elements. No comparable Be-rich population is known elsewhere in the
Galaxy, pointing to a rare enrichment event. The measured A(Be)/A(Li) excess ratio bears the imprint of spallation reactions, pointing to a highly energetic event in which fast CNO
nuclei fragmented upon collision with the surrounding medium. The silicon overabundance is also consistent with a hypernova origin. Such an event may have rapidly enriched the surrounding gas to [Fe/H] about -1.5 explaining the relatively high
metallicities of
stars formed from this material despite their old ages (about 13 Gyr).
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All authors Paolo Molaro, Piercarlo Bonifacio, Elisabetta Caffau, Lorenzo Monaco, Gabriele Cescutti
Instrumentation and Methods for Astrophysics
On-sky dark hole diggin' with implicit Electric Field Conjugation on MagAO-X
S. Y. Haffert, J. Liberman, J. R. Males et al. (+17 more)
Direct spectroscopy is very promising approach to characterizing the atmospheres of nearby rocky
exoplanets. Non-common path aberrations (NCPA) are differential aberrations between the science optical path and the adaptive optics optical path. The NCPA leak through the coronagraph and create speckles that mimic
exoplanet signals. This limits the sensitivity of high-contrast imaging instruments at close angular separations - exactly the separations where we want to search for rocky
exoplanets with current and future
telescopes and instruments. We aim to actively remove the NCPA on-sky during observations by using focal plane wavefront sensing and control with the newly upgraded MagAO-X instrument. MagAO-X is equipped with a unique second-stage Adaptive Optics (AO) system. The second-stage AO system contains a dedicated deformable mirror (DM) for coronagraphic focal plane wavefront control. This DM is placed after the science and AO beam-splitter and is therefore not seen by the main AO loop. The DM has been recently upgraded from an ALPAO-97 to a Boston Micromachine Kilo-DM. The new Kilo-DM enables focal plane wavefront control with the implicit Electric Field Conjugation (iEFC)
algorithm. We developed the necessary procedures to run iEFC with MagAO-X on-sky. We demonstrated the successful removal of NCPA on-sky with an iEFC interaction
matrix that was calibrated on the MagAO-X internal source. This demonstrates the repeatability between our off-sky and on-sky
alignment. The iEFC
algorithm was tested on HR4796A and Alpha Centauri in 0.5" seeing conditions. We saw a reduction of the NCPA by a factor of 2 to 20. This on-sky validation confirms the robustness and efficiency of iEFC under realistic observing conditions, paving the way for its integration into next-generation AO systems for the Extremely Large
Telescope and
Giant Magellan
Telescope.
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All authors S. Y. Haffert, J. Liberman, J. R. Males, L. M. Close, W. B. Foster, K. Van Gorkom, O. Guyon, A. D. Hedglen, P. T. Johnson, M. Y. Kautz, J. K. Kueny, J. Li, J. D. Long, J. Lumbres, M. Mars, E. A. McEwen, A. McLeod, L. Schatz, E. Tonucci, K. Twitchell
Earth and Planetary Astrophysics
Vetting Ambiguous Planetary Candidates (APC) in TESS Data: Insights from LATTE Package and Detection of Nine Potential Exoplanet Candidates
Umer Hameed Khan, Khushlim Khan, Muhammad Zeshan Ashraf et al. (+1 more)
We present the results of our study of Ambiguous Planetary Candidates (APCs) in data from the Transiting
Exoplanet Survey Satellite (TESS) using the open-source LATTE package. LATTE provides an effective framework for distinguishing transit-like signals, including planetary candidates and eclipsing binaries, from
stellar variability and instrumental noise. We performed a comprehensive analysis of TESS APCs by applying the LATTE diagnostic tools and visually inspecting the resulting light curves and diagnostic plots to identify false alarms and false positives. Our analysis confirms nine potential
exoplanet candidates that warrant follow-up observations with ground-based facilities. These findings demonstrate the effectiveness of the LATTE package for the identification and vetting of
exoplanet candidates in TESS data. Future analyses incorporating observations from additional TESS sectors will further improve candidate validation and may lead to the discovery of additional
exoplanet candidates.
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All authors Umer Hameed Khan, Khushlim Khan, Muhammad Zeshan Ashraf, A. Salam Khumber
Cosmology and Nongalactic Astrophysics
Phantom crossing from the Standard Model and General Relativity
Jinglong Liu, Tucker Manton, Yifu Cai et al. (+1 more)
Suggestions of a late-time phantom crossing from DESI
baryon acoustic oscillation measurements, combined with
cosmic microwave background and Type-Ia
supernova observations, have renewed interest in non-standard dark energy models. In this Letter, we propose a new realization of a low
redshift phantom crossing using only well understood ingredients from
fermion condensation and general relativity. Our construction relies on the interplay between effective quintom-like dark energy and backreaction from non-linear structure formation. The full cosmological
evolution is consistent with $\Lambda$CDM until low
redshift, where the backreaction starts to become prominent and a phase transition occurs. At this point, the total dark energy equation of state first crosses $w_{\text{DE}}=-1$ from above. For
benchmark values of the backreaction energy density, a second crossing from below occurs at a lower
redshift, as suggested by recent observation. Fitting our theoretical model with CPL parametrization, we find the result is consistent with the combined DESI+CMB+SNIa data analysis with DESY5, PantheonPlus, and Union3
datasets. Specifically, for backreaction density parameter $\Omega_{\rm BR}(z=0) = 0.0572$, the CPL parametrization gives the phantom crossing
redshift $z_* \simeq 0.35$, $w_0 \simeq -0.76 $ and $w_a \simeq -0.93$.
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All authors Jinglong Liu, Tucker Manton, Yifu Cai, Antonino Marciano
High Energy Astrophysical Phenomena
The Southern-sky MWA Rapid Two-metre (SMART) pulsar survey–IV. Survey update and an atlas of 205 non-recycled southern pulsars
N. D. R. Bhat, C. P. Lee, S. J. McSweeney et al. (+13 more)
The SMART survey is an ambitious effort to conduct sensitive searches for
pulsars and fast transients at 140-170 MHz. The novelty of voltage recording, long dwell times and the high-time and -frequency resolutions exchange a large survey speed for high computational cost. The survey covers the entire sky south of +30 degree in declination through a series of dedicated campaigns, accumulating 4 PB of data. The large volumes of data necessitate processing to be approached in multiple phases, and the initial searches focused on a shallow survey of parts of the skies, as reported in earlier papers. These data are also processed for re-detections of hundreds of known
pulsars in the southern sky, many of which are also the first detections below 400 MHz. This paper is motivated by the need to address the inherent difficulties in handling large amounts of voltage data and software/processing challenges for routine
pulsar detections, and also by the fast-evolving landscape of the SKA Observatory (SKAO). With the construction ramping up towards the full-scale SKA-Low, a low-frequency catalogue of detectable
pulsars in the southern sky will prove to be a valuable reference for science verification. A growing sample of low-frequency detections and measurements will also prove invaluable in a variety of science applications including population studies, survey simulations and emission beam models, refining interstellar medium models for electron densities and the spatial distribution of
turbulence, and also for
forecasting the detection prospects and survey yield from
pulsar surveys planned with SKA-Low. We present various data products, including pulse profiles, time series and multi-channel folded archives, along with the measurements of dispersion and rotation measures, and mean flux densities, and this will be periodically updated as more detections flow on from the ongoing data processing.
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All authors N. D. R. Bhat, C. P. Lee, S. J. McSweeney, B. W. Meyers, C. M. Tan, M. Xue, Q. Fu, N. A. Swainston, S. M. Ord, G. J. Sleap, S. E. Tremblay, W. van Straten, A. Williams, C. Di Pientrantonio, C. J. Harris, P. J. Elahi
High Energy Astrophysical Phenomena
Multi-wavelength Constraints on the Transient EP250905a
J. Quirola-Vasquez, P. G. Jonker, A. Levan et al. (+30 more)
Fast X-ray transients (FXTs) are a diverse class of high-energy suggested origins, ranging from
stellar explosions to compact object mergers. The Einstein Probe (EP) satellite discovers approximately 100 FXTs per year. We aim to constrain the physical origin of EP250905a. We analyze X-ray, optical, near-infrared (NIR), and
radio temporal and spectral properties of EP250905a. In addition, we assess the possible role of weak gravitational
lensing in shaping its observed characteristics. EP250905a fades rapidly in X-rays, and we detect no NIR or
radio emission, but we detect early optical emission that rapidly fades beyond the detection limits. Two nearby
galaxies are identified for which we derive spectroscopic
redshifts of $z=0.374$ (G1) and $z=2.714$ (G2). Our analysis favors G2 as the host of the FXT EP250905a. The angular separation of 2.56\arcsec\, between the FXT's optical counterpart and the center of the G1
galaxy suggests the emission of the FXT might be moderately magnified by
lensing effects ($\mu\approx3.9$) given the inferred Einstein radius of G1 ($\theta_E\approx1.9$ arcsec). The data are best explained as an afterglow from a mildly off-axis structured jet at $z=2.714$, providing a consistent broadband interpretation that also allows for weakly lensed emission of EP250905a.
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All authors J. Quirola-Vasquez, P. G. Jonker, A. Levan, D. B. Malesani, F. E. Bauer, A. Martin-Carrillo, G. Corcoran, D. Mata Sanchez, R. A. J. Eyles-Ferris, F. Carotenuto, M. Ravasio, J. Sanchez-Sierras, J. Bright, J. A. Chacon, L. Cotter, F. J. Cowie, N. Sarin, M. A. P. Torres, J. N. D. van Dalen, A. P. C. van Hoof, V. D'Elia, P. Jakobsson, N. Habeeb, S. Kobayashi, A. Saccardi, M. De Pasquale, D. Xu, Y. H. Cheng, R. D. Liang, H. Sun, Y. Wang, W. Yuan, W. D. Zhang
Instrumentation and Methods for Astrophysics
Robust Heteroskedastic Matrix Factorization: A Generalization of PCA that Flags Outliers and Handles Missing Data
Thomas Hilder, David W. Hogg, Andrew R. Casey et al. (+1 more)
We present Robust Heteroskedastic
Matrix Factorization (RHMF), a generalization of Principal Component Analysis (PCA) that is robust to outliers, handles per-feature uncertainties and missing data, and automatically flags per-feature and per-object anomalies. RHMF is useful both in recovering a low-dimensional
embedding unspoiled by bad data or anomalies, and in identifying those anomalies. It utilises an iterative reweighting
algorithm that implicitly maximizes a Student-t likelihood. This admits an equivalent probabilistic interpretation as fitting a hierarchical model with per-data-point latent variances. We deliver a fast JAX implementation, Robusta-HMF, and practical guidance for users. We demonstrate the ability of the model to identify and mitigate outliers of different classes. Identification accuracy is contingent on the choice of hyperparameters, but we show that these can be set reliably by cross-validation. We also apply RHMF to RVS spectra from
Gaia DR3 to find main-sequence
stars that are strange relative to their neighbors in color-magnitude space. We highlight specific examples, including a known binary hosting a Be
star, and M-
dwarfs with subtle emission in the Ca II triplet lines, indicative of
accretion or
magnetic activity, which would not be obvious to identify by eye.
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All authors Thomas Hilder, David W. Hogg, Andrew R. Casey, Hans-Walter Rix
Solar and Stellar Astrophysics
Investigation on the Relation between Active Regions' Compliance with Empirical Laws and Flare Productivity
Jinhui Pan, Rui Liu, Jiangtao Su et al. (+1 more)
It remains evasive whether
solar active regions (ARs) obeying or violating Hale's polarity law, Joy's tilt law, and the hemispheric helicity rule (HHR) differ in
flare productivity. Here we conduct a comprehensive statistical analysis of ARs during the
Solar Cycle 24 and the ascending phase of Cycle 25. ARs are automatically detected from full-disk line-of-sight magnetograms acquired by the Michelson Doppler Imager (MDI) and the Helioseismic and
Magnetic Imager (HMI). We calculate tilt angles via flux-weighted polarity centroids, estimate
magnetic twist by the force-free parameter $\alpha_{\mathrm{best}}$ from HMI vector magnetograms, and measure
flare productivity using the
flare index (FI) built from GOES C-class-and-above events. Our results substantiate that the majority of ARs follow the aforementioned three empirical laws. The compliance rate tends to be higher for ARs emerging at higher latitudes or having larger centroid distance, while total unsigned
magnetic flux exerts limited influence, with a clear positive correlation only for Hale's law. Overall, FI shows no significant discrepancies across different compliance groups, except that Cycle 24 ARs that satisfy Hale's and Joy's laws but violate the HHR exhibit higher FI than other groups. We also identify empirical thresholds for centroid distance and total unsigned flux, above which the median FI of binned ARs becomes nonzero. Combining the flux and distance thresholds effectively separates
flare-productive from
flare-quiet ARs. We hence conclude that the
flare productivity of ARs is not dependent on the compliance with the empirical laws, but more closely associated with sufficiently large and strong
magnetic systems.
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All authors Jinhui Pan, Rui Liu, Jiangtao Su, Jie Jiang
Solar and Stellar Astrophysics
RedDots: Magnetic field of the nearby active M dwarf GJ 729, and a search for companions
E.L. Brown, S.V. Jeffers, S.C. Marsden et al. (+5 more)
M
dwarfs are
prime targets for discovering
exoplanets, and the nearest M
dwarfs to the Sun provide among the best opportunities for follow-up detailed
exoplanet characterization. GJ 729, the seventh closest M
dwarf to the Sun, presents significant challenges for
exoplanet detection due to its high levels of
magnetic activity. To address this, we present a detailed analysis of GJ 729's
magnetic field and its variability, followed by a search for
exoplanets beneath the activity-induced noise in the
stellar radial velocity. The geometry of GJ 729's large-scale
magnetic field was reconstructed using new and archival spectropolarimetric data for a total of four epochs spanning 10 years. Results indicate a weak large-scale field ranging from 50 to 145 G, and an evolving non-axisymmetric field geometry that varies from poloidal dominated to a near-equal poloidal-toroidal configuration. We modeled activity-induced radial velocity variations using Gaussian Process Regression and activity diagnostics, and searched for planetary companions using ~90 d of high-cadence spectra taken contemporaneously with the high-precision CARMENES and HARPS spectrographs. Activity-only and activity + Keplerian models offered statistically equivalent fits, with a consistently preferred Keplerian period of ~7 d and amplitude of ~1.9 m/s across a range of activity modeling approaches. This could relate to an Earth-mass or Super-Earth
planet, or residual
stellar activity with power concentrated at a multiple of the rotation half-period. Our findings provide insight into the
magnetic behavior of fully convective M
dwarfs, and highlight the potential and challenges of detecting Keplerian RV signatures that are only a fraction of activity amplitudes.
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All authors E.L. Brown, S.V. Jeffers, S.C. Marsden, F. Liebing, S. Bellotti, J.R. Barnes, C.A. Haswell, V. Koseleva
Instrumentation and Methods for Astrophysics
Catching Disguised Transients with ASTRANet: Anomaly-Aware Spectroscopic Classification and Conformal Calibration
Argyro Sasli, Maojie Xu, Alexandra Junell et al. (+21 more)
Time-domain surveys discover thousands of transients per year, but the spectroscopic identification of rare and physically peculiar objects remains rate-limited by closed-set classifiers that confidently assign every input to a known class – including spectra that genuinely belong to no known class. We present the ASTRANet framework, a confidence-aware infrastructure for spectroscopic transient classification built around three coupled modules: a hierarchical spectral classifier that operates directly on observer-frame spectra without requiring host-
galaxy redshift or spectral phase as inputs; an anomaly detection layer (ASTRANet-Sentinel) that non-linearly combines $16$
embedding-space anomaly scores spanning four physically motivated families; and a conformal uncertainty quantification layer (ASTRANet-CP). We validate the framework on a held-out evaluation set of $289$ rare and out-of-taxonomy transients spanning $11$ classes deliberately excluded from training, chosen to span the full physical diversity of the rare-anomaly population: AGN-related outliers, GRB-related events, gap transients, novae, and peculiar
supernovae. Through five astrophysically distinct failure modes of closed-set classifiers, we show that classifier-internal uncertainty and
embedding-based anomaly detection are structurally complementary axes of confidence rather than alternative implementations of the same
estimator. We further introduce AD-stratified Mondrian conformal prediction (AD-MCP) within ASTRANet-CP, achieving uniform conditional coverage across anomaly-score strata where vanilla Mondrian under-covers in the operational regime. This establishes the methodological infrastructure for confidence-aware spectroscopic discovery in the Vera C.\ Rubin Observatory era.
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All authors Argyro Sasli, Maojie Xu, Alexandra Junell, Hailey Markoff, Avyukt Raghuvanshi, Felipe F. Nunes, Theophile Jegou Du Laz, Jesper Sollerman, Christoffer Fremling, Drew Oldag, Antoine Le Calloch, Sushant Sharma Chaudhary, Sneha Maharjan, Maxine West, Benny Border, Nabeel Rehemtulla, Richard Dekany, Joahan Castaneda Jaimes, Russ R. Laher, Reed Riddle, Mansi M. Kasliwal, Matthew J. Graham, Ashish A. Mahabal, Michael W. Coughlin
Solar and Stellar Astrophysics
A Transport Theory of Turbulent Coronal Heating in General Geometry
Jonathan Squire, Benjamin D. G. Chandran, Toby Adkins et al. (+3 more)
Magnetic geometry shapes how
turbulence transports and dissipates energy in strongly magnetized
plasmas. The
solar corona, a maze of open and closed flux tubes with sharp transverse gradients, is a prominent example, yet most wave-
turbulence models of coronal heating assume symmetric flux tubes or add
geometric effects in ad hoc ways. Here we develop a geometry-complete multiscale transport theory for reduced-magnetohydrodynamic
turbulence in an arbitrary background field, retaining squashing (
magnetic shear), transverse gradients,
curvature, and
gravity at the same order as standard expansion-driven reflection, and coupling fast, anisotropic fluctuations to slow background
evolution through conservation laws. Applied to the corona, it recovers the standard reflection-driven turbulent cascade in smooth regions such as coronal-hole interiors, but predicts that in structured regions geometry-driven channels can dominate: squashing drives reflection even when parallel Alfvén-speed gradients are weak;
curvature and non-radial geometry drive compressive heating channels; and waves catalyze the relaxation of velocity shear into heat. The same dynamics drive cross-field transport of mass, composition, momentum, and heat across open-closed interfaces, at rates rivaling the field-parallel supply from the base. These effects bias heating to low altitudes in structured regions, giving a physical basis for the coronal-hole–boundary corrections used in empirical wind-speed predictors. Additionally, the framework's slow-timescale transport equations could be evolved in time, providing a route to a global, geometry-aware model of a structured wave-driven corona and wind. More broadly, the theory provides an energy-consistent account of
turbulence, geometry, and transport effects relevant to various astrophysical and terrestrial settings, from magnetospheres and
accretion flows to fusion experiments.
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All authors Jonathan Squire, Benjamin D. G. Chandran, Toby Adkins, William A. Clarke, Romain Meyrand, Matthew W. Kunz