Earth and Planetary Astrophysics
A study on the contribution of the interplanetary medium in radio occultation experiments
Keshav Aggarwal, R. K. Choudhary, Abhirup Datta et al. (+4 more)
Irregularities in electron density within the interplanetary medium (IPM) can cause fluctuations in the Doppler frequency of spacecraft
radio signals. The amplitude of these fluctuations depends on factors such as the carrier frequency, propagation geometry, and link configuration. However, quantitative characterization of these effects across different frequencies in various occultation experiments is currently limited. We analyze five complementary
datasets: two-way S-band observations from Chandrayaan-3 outside the lunar ionosphere, two-way S-band data from Chandrayaan-2 during lunar occultation, one-way S/X band measurements from the Venus Express
Radio Science (VeRa)/Akatsuki
Radio Science (Akatsuki) under IPM-only conditions, and one-way X-band Akatsuki data during
solar occultation. The Chandrayaan-3 and Akatsuki IPM observations isolate IPM effects by excluding contributions from planetary atmospheres, the lunar ionosphere, and, except during
solar occultation, the
solar corona. Chandrayaan-3 data sample dynamically evolving Earth-Moon geometries and exhibit weak, mHz-level Doppler fluctuations, while Chandrayaan-2 observations provide near-lunar
plasma benchmarks with higher amplitudes, during quiet time
solar and geomagnetic conditions. Akatsuki and VeRa's IPM-only measurements capture long-path interplanetary effects, whereas Akatsuki
solar occultation data reveal strong coronal signatures. Power spectral density analysis indicates Kolmogorov-like
turbulence for lunar occultation and
solar occultation cases, while IPM-only spectra show low-amplitude fluctuations. These results quantify the IPM contribution to Doppler noise, demonstrate the enhanced
plasma sensitivity of two-way coherent links, and provide constraints relevant to
turbulence modelling, precision spacecraft tracking, and the interpretation of
radio occultation experiments.
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All authors Keshav Aggarwal, R. K. Choudhary, Abhirup Datta, Soumyaneal Banerjee, R. Manikantan, Anshuman Sharma, Takeshi Imamura
Cosmology and Nongalactic Astrophysics
Tomographer: End-to-end Redshift Distribution Estimation for Source Catalogs and Intensity Maps
Yi-Kuan Chiang, Yu Voon Ng, Yu-Ren Lin et al. (+2 more)
Redshift information is central to nearly every extragalactic and cosmological application of sky surveys, yet only a small fraction of cataloged sources, and none of the
photons forming diffuse backgrounds, have spectroscopic
redshifts. Clustering-based
redshift inference estimates the
redshift distribution of an arbitrary
dataset through spatial cross-correlation with a reference sample of known
redshifts. It relies only on positional information, making it applicable to any tracer of large-scale structure, including source populations and diffuse intensity maps. Its broader adoption, however, has been limited by technical barriers: assembling and characterizing spectroscopic references, expensive pair-counting computations, theoretical corrections, and systematic control. To remove these barriers, we introduce Tomographer, an end-to-end clustering-
redshift framework. The key design feature is a set of precomputed "activation maps" encoding the spatial pair information of 3 million SDSS spectroscopic
galaxies and
quasars up to $z\sim4$ over $10{,}000\,{\rm deg}^2$. This eliminates user-end pair counting, reducing computational scaling from $O(N\log N)$ to $O(1)$ map multiplications. Given a source catalog or intensity map, Tomographer returns the bias-weighted
redshift distribution, $b(z)\,{\rm d}N/{\rm d}z(z)$ or $b(z)\,{\rm d}I/{\rm d}z(z)$. We validate the framework against samples with known
redshifts, demonstrate accurate uncertainty estimates, and show robustness to survey footprint, spatially varying selection functions, beam smoothing, and foreground contamination. We showcase applications to source catalogs selected by flux, color, photometric
redshift, morphology, or variability, and to intensity maps from
radio to X-rays. Future Tomographer releases will incorporate additional wide-field spectroscopic reference samples as they become available.
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All authors Yi-Kuan Chiang, Yu Voon Ng, Yu-Ren Lin, Manuchehr Taghizadeh-Popp, Brice Ménard
Earth and Planetary Astrophysics
Phase-curve approach to study atmospheric flows in hot Jupiters
D. Shulyak, W. Dietrich, V. Parmentier et al. (+5 more)
Short-orbit gaseous
exoplanets are the best targets to study atmospheric dynamics. A time series of emission observations collected at various photometric filters (phase curves) provides insights into atmospheric flows. Modern observations reveal a wide variety of phase curves, but their utility for probing atmospheric circulation as a function of altitude has not yet been explored in detail. We aim to understand the properties of phase curves and their connection to underlying atmospheric flows, as well as to define a set of multiwavelength observations that could be used to resolve these flows as a function of altitude. We utilized a subset of the
solar metallicity models from the grid of ADAM/GCM and state-of-the-art radiative transfer codes to predict phase curves. We made predictions for a variety of photometric filters on board the Spitzer, TESS, CHEOPS, HST, and JWST missions, and explored the sensitivity of each filter to flows at various atmospheric depths. Our calculations show that the main parameter that regulates the phase-curve offsets in our models is the atmospheric temperature, although high
metallicity can also have strong impact by reducing phase-curve offsets. This is not fully supported by available observations, which possibly indicates a missing physical process in the models. The predicted contribution functions suggest that the best combination of photometric filters to study atmospheric flows is NIRCam filters because they are sensitive to a wide range of pressures between 10 bar and 1e-4 bar depending on
planet temperature, respectively. High-resolution spectroscopy is predicted to detect differential Doppler shifts of 1-4 km/s between molecular bands formed at different altitudes, providing an independent probe of vertical circulations.
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All authors D. Shulyak, W. Dietrich, V. Parmentier, D. Cont, L.-M. Lara, L. Gkouvelis, M. R. Swain, M. Rengel
Cosmology and Nongalactic Astrophysics
Bridging perturbation theory and simulations: initial conditions and fast integrators for cosmological simulations
Oliver Hahn
These lecture notes provide an introduction to the generation of initial conditions for cosmological N-body simulations. Starting from the definition and properties of Gaussian random fields, we discuss their role in cosmology and the efficient generation of such fields using
Fourier methods. The Vlasov-Poisson system is introduced as the governing framework for cold collisionless matter, and its solution via characteristics and Lagrangian perturbation theory (LPT) is detailed. We discuss the use of LPT for initializing N-body simulations, emphasizing the importance of high-order LPT and late-time starts to minimize truncation and discreteness errors. Finally, we discuss time integration schemes, including PT-informed integrators, and their role in accurately evolving the system. These notes aim to bridge the gap between theoretical perturbation methods and practical simulation techniques.
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Solar and Stellar Astrophysics
The symphony of pulsations and binarity among massive stars using HERMES spectroscopy and TESS photometry
K. Thomson-Paressant, D. M. Bowman, F. Nardini et al. (+16 more)
A wide range of variability mechanisms exist among intermediate mass and massive
stars, which are not yet fully understood. Using complementary data sources for a large population of B- and O-type
stars, we aim to study the prevalence and interplay of different types of variability, including binarity, pulsation, and rotation, to prepare for future modelling. To this end, we analyse high-resolution HERMES spectra and 2-min cadence TESS photometry and characterise the diverse variability observed within a population of 873 O- and B-type
stars. The spectroscopic data were normalised using machine-learning techniques, compared to a grid of synthetic TLUSTY spectra to determine
stellar parameters, and used to identify radial velocity variability. Photometric time series were analysed using standard frequency analysis methods to detect pulsations and rotational modulation signatures. We find that more than 93 per cent of the sample exhibits photometric variability. Photometric variability caused by pulsations is identified in 82 per cent of the sample, with dominant contributions from $\beta$ Cep and slowly pulsating B-type
stars, as well as
stochastic low-frequency variability. Based on a limited number of spectroscopic epochs, at least 14 per cent of the
stars show evidence of binarity, including both eclipsing and spectroscopic systems. This work represents one of the largest homogeneous surveys of variability for intermediate-mass and massive
stars in the Northern hemisphere, and complementing similar efforts in the Southern hemisphere. It provides a statistical framework for future studies of
stellar structure and
evolution, particularly in the context of asteroseismology.
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All authors K. Thomson-Paressant, D. M. Bowman, F. Nardini, L. J. A. Scott, J. Bodensteiner, T. Shenar, L. Mahy, G. Handler, N. Shitrit, I. Arcavi, M. Abdul-Masih, S. Simon-Diaz, P. Van Daele, A. J. Kalita, L. Dennis, J. Henneco, A. Tkachenko, H. Sana, H. Van Winckel
Instrumentation and Methods for Astrophysics
Pixel-Level Calibration for Space-Based High Precision Astrometry Using Young's Fringes
Hugo Rousset, Eric Thiébaut, Chloé Rey et al. (+8 more)
The detection of Earth-like
exoplanets via astrometry necessitates centroiding precision at the 0.3 microarcsec level, thereby imposing stringent constraints on the focal plane geometry of space
telescopes. The AGATE focal plane instrument, a proposed component of the NASA Habitable Worlds Observatory (HWO), aims to achieve this objective through the calibration of the intra-pixel response function of CMOS detectors to an accuracy of 50 micropixel (220 nm The present paper proposes a Young's fringes-based calibration method, derived from those employed by JPL and IPAG, for the purpose of mapping the pixel response barycenter offsets across the detector. Using a Pyxalis GIGAPYX-4600 CMOS sensor, we demonstrate via simulations and laboratory measurements that (1) a precision of 500 micropixel is achievable with 10,000 frames (current setup); (2) inter-pixel capacitance crosstalk and fringe hyperbolicity are dominating the errors at small and large scales, respectively; and, (3) an iterative inverse problem approach with a
hyperbolic fringe model is proposed to overcome paraxial approximation limits for 1 Gpix focal planes. These results pave the way for on-board calibration of HWO's astrometric instrument, ensuring the sub-microarcsec precision required for exo-Earth detection.
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All authors Hugo Rousset, Eric Thiébaut, Chloé Rey, Manon Lizzana, Sébastien Soler, Fabrice Pancher, Julien Michelot, Logi Olgeirsson, Jean Baptiste Le Bouquin, Alain Léger, Fabien Malbet
Solar and Stellar Astrophysics
Unravelling Mass Transfer in Algols from Surface Abundances. I. Z Vulpeculae
Ahmet Dervişoğlu, Simge Adalal{\i}, Ferhat Güney et al. (+7 more)
The photospheric abundance pattern of the components is a sensitive probe of mass and angular momentum transfer in Algols. With the aim to trace the evolutionary history and disclosed efficiency of mass transfer in Algols we collected new high-resolution spectra for about a dozen Algols with the hermes spectrograph at the Mercator
Telescope on La Palma, Canary Islands. In the present paper, which is the first in the series, we present the results of a comprehensive analysis of Z Vul, a hot Algol-type system. We derived the absolute
stellar quantities and elemental abundances for the components. The carbon-to-nitrogen (C/N) ratio is the most sensitive tracer of thermonuclear processing and mass transfer. It is found to be within expected value for gainer but donor lacks the severe C/N inversion traditionally expected for a deeply stripped
star. An extensive grid of over three million evolutionary models was calculated with the Cambridge
STARS code which allows determination of the best-fitting and all surviving models. Constraints from the He and CNO abundances indicate that Z Vul underwent an episode of nearly conservative mass transfer during the Main Sequence life-time of the originally more massive component (Case A). Our detailed chemical tagging confirms that the surface abundances of the mass-losing component represent the delicately stripped outer layers still not reaching the CNO-rich core. This underscores the need of coupling high-resolution spectroscopic abundances with interior
stellar profiles to accurately reconstruct the evolutionary history of interacting binaries.
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All authors Ahmet Dervişoğlu, Simge Adalal{\i}, Ferhat Güney, Bar{\i}ş Hoyman, Timur Şahin, Ömür Çak{\i}rl{\i}, Kresimir Pavlovski, David Mkrtichian, Peter De Cat, Patricia Lampens
Earth and Planetary Astrophysics
Long-lived thermal dynamo generation on differentiated, impact-disrupted planetesimals
Hannah R. Sanderson, James F. J. Bryson and Claire I. O. Nichols
Meteorites containing both metal and silicates indicate that some planetesimals were partially differentiated and/or processes mixed planetesimal cores and mantles post-differentiation. Time-resolved paleomagnetic records in these meteorite groups can shed light on the differentiation and mixing histories of such bodies. Previous studies measured paleomagnetic remanences in two such meteorite groups, the IIE irons and the Main Group pallasites, and used thermal
evolution and dynamo generation modelling to recover parent body properties. However, these studies assumed that these meteorites only recorded
magnetic fields generated by core solidification; an assumption recently shown to be invalid. We use a refined planetesimal thermal
evolution and dynamo generation model that considers thermal and compositional drivers of dynamo generation simultaneously to re-evaluate the parent body properties of the IIE irons and Main Group pallasites and constrain the formation mechanisms of these meteorites. We find that none of the remanences require core solidification, but later formed remanences are more likely to record dynamos driven by core solidification. The Main Group pallasites and IIE iron parent bodies likely had radii of $\sim$400km with core radius fractions of $\sim$0.5 and $\sim$0.7, respectively. Impacts shaped both parent bodies: the Main Group pallasites formed too far from the core-mantle-boundary to result from ferromagmatism and instead formed by impacts, and the IIE iron's core radius fraction suggests the parent body experienced mantle-stripping collisions. Overall, combining meteorite paleomagnetism with thermal
evolution and dynamo generation models provides insights into the long-term
evolution of differentiated planetesimals, their interior structures, and metal-silicate mixing on these bodies.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
From Størmer to Schwarzschild: Analytical Dynamics of Charged Particles in a Dipole Magnetosphere
Francisco S. N. Lobo and Tiberiu Harko
We investigate the conservative dynamics of relativistic charged particles in a Schwarzschild spacetime threaded by an externally supported dipolar
magnetic field. The gravitational sector is treated exactly in isotropic coordinates, while the electromagnetic field is described by the leading asymptotic term of the relativistic exterior dipole solution. This formulation provides an analytically tractable relativistic extension of the classical Størmer problem and allows the circular-orbit and stability structure to be studied explicitly. For the outward-Lorentz branch, characterized by a positive signed
magnetic coupling for positive azimuthal motion, we find a non-trivial competition between radial and vertical stability. Weak
magnetic coupling shifts the radially marginal orbit inward, whereas at stronger coupling vertical instability becomes the limiting mechanism and the inner boundary of stable circular motion moves outward. The associated vertical epicyclic mode progressively softens and vanishes at the vertical stability boundary. The marginally bound sequence exhibits a distinct strong-coupling behaviour, illustrating that energetic and stability boundaries need not evolve together. The radial and vertical epicyclic frequencies also generate characteristic commensurabilities that may provide natural sites for nonlinear orbital coupling. Because the
magnetic field is treated as a test field, these charged-particle effects leave the
vacuum Schwarzschild null-geodesic structure unchanged.
Magnetic signatures in compact-object observations must therefore arise through the dynamics and radiation of charged matter,
plasma propagation effects, or physics beyond the test-field approximation. The framework developed here provides an analytical basis for studying nonlinear dynamics, radiation reaction, and more realistic compact-object magnetospheres.
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Astrophysics of Galaxies
Chemical Abundances and Globular Clusters of Milky Way Dwarf Galaxies
Baitian Tang, Shihui Lin, Ruoyun Huang et al. (+5 more)
We present an overview of our ongoing GASTRONOMI project, which investigates the coevolution of the Milky Way (MW), its satellite
dwarf galaxies, and their
star clusters through chemo-dynamical analysis. We derive precise chemical abundances for
stars in five classical
dwarf galaxies, which reveal mass-dependent chemical
evolution, particularly in alpha elements, such as [Si/Fe]. A distinct dichotomy in [Al/Fe] is found between metal-rich ([Fe/H]>-1.5)
stars formed in-situ in the MW and those originating in
dwarf galaxies.
Star clusters act as sensitive environmental probes. The presence of multiple populations correlates with
galactic evolution, and nitrogen-rich
stars in Fornax are likely relics of disrupted globular clusters (GCs). We developed a chemical classification for
Galactic GCs, isolating
primordial populations by their low [Al/Fe]. This places in-situ and accreted GCs in distinct regions of the [Al/Fe]-[Fe/H] plane, providing a new tool to reconstruct the
Galaxy's
accretion history.
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All authors Baitian Tang, Shihui Lin, Ruoyun Huang, Cheng Xu, Jose G. Fernandez-Trincado, Doug Geisler, Chengyuan Li, Zhiqiang Yan
High Energy Astrophysical Phenomena · Cross-listed from physics.plasm-ph
Radiation reaction in the classical relativistic Størmer problem
Francisco S. N. Lobo and Tiberiu Harko
We extend the classical relativistic Størmer problem by incorporating radiation reaction through the Landau–Lifshitz formulation, thereby providing a self-consistent description of dissipative charged-particle motion in a static dipole
magnetic field. We derive the complete dimensionless equations and distinguish them from a reduced drag-only model that preserves the exact energy-loss law while omitting directional effects associated with
magnetic field gradients. For planar motion, the reduced system yields exact instantaneous
evolution laws for the particle energy and canonical angular momentum, together with averaged transport equations for regular bound librations. When the motion is constrained to the instantaneous circular branch, the secular
evolution can be integrated in closed form and approaches a simple large-radius power law. This analytical solution provides a useful
benchmark, although the circular branch is radially unstable and therefore does not describe generic nearby trajectories. Numerical integrations further illustrate the nonuniform dissipative deformation of planar rosette-like orbits. In three dimensions, the complete Landau–Lifshitz force produces local exponential damping of small vertical perturbations, with the leading contribution arising from the field-gradient term absent from the reduced model. These exact, averaged, conditional, and local results establish a controlled analytical framework for studying radiation-driven phase-space transport in strongly inhomogeneous
magnetic fields and provide a foundation for future global simulations, kinetic descriptions, and calculations of the associated electromagnetic emission.
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Solar and Stellar Astrophysics
The double white dwarf merger model for the progenitors of SN 2021yfj-like events
Dongdong Liu, Chengyuan Wu, Takashi J. Moriya et al. (+4 more)
Context. Recently, a new class of
supernovae with prominent narrow emission features of Si, S and Ar has been reported, i.e. SN 2021yfj-like events (SNe Ien). Their progenitor origin is still unknown. It has been suggested that a massive CO WD may evolve into a Si/S-rich WD when accreting He-rich matter at a high mass-transfer rate. If the He companion subsequently evolves into another more massive WD, the merger of this double WD system can generate Si/S-rich CSM through
tidal stripping. Following the SN explosion, the interaction between the SN ejecta and the Si/S-rich CSM could produce the Si, S, and Ar emission lines characteristic of SN 2021yfj-like events. Aims. In this work, we aim to determine the initial parameter space of WD+He
star systems that can lead to SN 2021yfj-like events via the double WD merger scenario, and to quantify their theoretical
Galactic birthrate and delay-time distributions. Methods. We perform detailed binary
evolution simulations of a large number of semidetached WD+He
star systems to obtain the parameter space that leads to the formation of Si/S-rich WDs and subsequent double WD mergers. We then use binary population synthesis to calculate the
Galactic birthrate and delay-time distribution of such events. Results. For the formation of SN 2021yfj-like events, we found that the initial CO WD and He companion masses must lie in the ranges of 1.0-1.2 M_sun and 2.2-2.5 M_sun, respectively. The derived merger rate for this scenario is ~(2.6-4.4)x10^-5 yr^-1 with delay times longer than 450 Myr, which is about 1% of the observed SN Ia rate. Conclusions. We suggest that the double WD merger scenario involving a Si/S-rich WD originating from a CO WD+He
star system, represents a significant and competitive model for SN 2021yfj-like events, underscoring the need for further observations of similar events coupled with relevant theoretical investigations.
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All authors Dongdong Liu, Chengyuan Wu, Takashi J. Moriya, Jiawen Ning, Zhengwei Liu, Zhanwen Han, Bo Wang
Solar and Stellar Astrophysics
Electron transport in a radiation-dominated plasma Application to solar corona brightenings
Roland Duclous, Vladimir Tikhonchuk, Marina Leboulanger et al. (+3 more)
Bremsstrahlung scattering of fast electrons on ions can be enhanced by the microwave radiation present in the
solar corona. It can account for the electron diffusive transport along
magnetic loops and high precipitation rates. This process can also dominate the transport of thermal electrons confined in such loops. The influence of stimulated Bremsstrahlung scattering on the electron transport is studied, with focus on the return current induced by the fast electron population trapped in
magnetic loops. Overall, transport coefficients are reevaluated in the radiation-dominated
plasma, characterized by the stimulated action of radiation on the Bremsstrahlung electron-ion collision, down to thermal velocities. We develop a theoretical framework for electron transport driven by a large bandwidth, bright low-frequency part of the
photon spectrum and compute a set of radiation-enhanced transport coefficients. UV, XEUV and hard X-ray signals from
flares, evidencing anomalous resistivity, thermal conduction inhibition and high precipitation rates of fast electrons, are reinterpreted. The anomalous resistivity due to stimulated Bremsstrahlung scattering is found to dominate the classical resistivity in
flares. The runaway effect due to Coulomb collisions is suppressed. Thermal conduction is inhibited compared to the Spitzer conduction, in agreement with coronal seismology of slow-mode waves. Stimulated Bremsstrahlung scattering is found to be a key collisional process in flaring events. It can explain the above loop-top hard X-ray signal due to the fast electrons, and the measured electrical conductivity due to the thermal electrons. As a perspective, the corresponding transport coefficients can be used in radiation MHD codes. The radiation model could also be applied to stimulate large-angle electron scattering in the kinetic or hybrid models used to study the
solar corona.
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All authors Roland Duclous, Vladimir Tikhonchuk, Marina Leboulanger, Xavier Blanc, Allan-Sacha Brun, Antoine Strugarek
Astrophysics of Galaxies
Binary Constraints on the Origin of Nitrogen-rich Field Stars
Liao Yang, Baitian Tang, José G.Fernández-Trincado et al. (+4 more)
Recent JWST observations have revealed
galaxies with unusually high N/O ratios, suggesting that nitrogen enrichment may be common in intense
star-forming environments in the early Universe. In the Milky Way, nitrogen-rich(N-rich)
stars in the
Galactic field have long served as probes of early
Galaxy formation and globular cluster enrichment. However, the identification of binaries among these
stars raises the possibility that binary mass transfer could contribute to their origin. In this work, we utilize multi-epoch radial velocities and element abundances from APOGEE DR17 to constrain their formation sites. Among 266 N-rich field
stars, 33 exhibit radial velocity variations of $\Delta {\rm RV} > 1\,{\rm km/s}$, including 10 robust spectroscopic binaries identified using the $F_2$ statistic within a well-sampled subset of 46
stars. The resulting close-binary fraction ($21.7\pm6.1\%$) is statistically indistinguishable from that of chemically normal field
stars ($18.1\pm0.6\%$), showing no evidence of the excess expected from AGB binary pollution. This is further supported by the absence of correlation between [N/Fe] and [Ce/Fe] and the lack of [C/Fe] enhancement. Crucially, we detect an anti-correlation between binary fraction and [Al/Fe], with strongly Al-enhanced
stars ($[\mathrm{Al/Fe}] \gtrsim 0.5$) exhibiting a reduced binary fraction ($< 10\%$). This trend serves as a dynamical fingerprint of high-density environments, consistent with the efficient disruption of binaries via three-body interactions in GC cores. Our results do not support binary mass transfer as the dominant formation channel for N-rich field
stars; they are predominantly GC escapees that retain the dynamical
memory of their dense birth sites.
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All authors Liao Yang, Baitian Tang, José G.Fernández-Trincado, Chengyuan Li, Long Wang, Dengkai Jiang, Bo Ma
Cosmology and Nongalactic Astrophysics
The One-Loop Power Spectrum of Fast Radio Burst Dispersion Measures
Haruki Ebina and Martin White
Fast
radio burst (FRB) dispersion measures trace free electron column densities and will soon offer a unique probe of low-$z$
baryons. Such measurements can constrain cosmology directly, with the free electrons serving as a new tracer of large-scale structure, and probe the baryonic feedback of
galaxies, a leading systematic for weak
lensing surveys such as LSST and Euclid. We prepare for both science cases using effective field theory (EFT) and hydrodynamical simulations. We construct the one-loop EFT description of the free-electron auto-spectrum $P_{ee}$ and electron-
galaxy cross-spectrum $P_{eg}$, placing FRB dispersion clustering on the same theoretical footing as spectroscopic
galaxy analyses, and quantify the FRB densities at which this modeling is useful. We also investigate suitable
galaxy samples for cross-correlations, finding that current spectroscopic catalogs provide appropriate
redshift range and sufficient density. We validate the model against the FLAMINGO simulations, jointly fitting $P_{ee}$, $P_{eg}$, and $P_{gg}$ for DESI-like samples at $z=0.2$ and 0.5. The model describes all three spectra to $k\sim0.2\,h\,{\rm Mpc}^{-1}$, with an electron linear bias $b_{e,1}\simeq0.92$, higher-order biases consistent with zero, and all parameters stable across feedback variants. Together with the near-perfect electron-matter correlation $r_{em}\simeq1$, this establishes free electrons as nearly unbiased, feedback-robust tracers of matter, supporting a key assumption of FRB-based feedback constraints. These properties make electron clustering an ideal application for Hybrid Effective Field Theory (HEFT), which would extend the modeling reach by a further factor of 2–3. The low-$z$ electron spectrum becomes signal-dominated beyond the linear regime within the first few years of next-generation surveys; the models developed here will be necessary on these timescales.
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Solar and Stellar Astrophysics
A Possible Stellar CME Event Associated with a Long-duration Optical Flare on the RS CVn-type Star UX Arietis
Cao Dongtao and Gu Shenghong
Coronal mass ejections (CMEs) are large-scale eruptions of magnetized
plasma from
stellar coronae, and they are always accompanied by
flares. In this study, we present high-resolution spectroscopic observations of a long-duration optical
flare on the RS CVn-type
star UX Arietis (UX Ari). Around the
flare peak, we have detected a far-blueshifted emission component in the H$\alpha$ line profile—a signature of an erupting prominence—indicating a possible
stellar CME. After correcting for projection effects, the eruption velocity reaches $\sim -432$ km s$^{-1}$ when assuming radial propagation, significantly exceeding the escape velocity of the primary component ($\approx 304$ km s$^{-1}$). This strongly supports the detection of a
stellar CME. The mass of this CME is at least $2.7 \times 10^{20}$ g, and its kinetic energy is $2.5 \times 10^{35}$ erg. The mass value is consistent with the
solar flare–CME scaling relation, while its kinetic energy lies below the
solar trend. The
flare itself released an energy of $4.2 \times 10^{36}$ erg in the H$\alpha$, corresponding to a white-light bolometric energy of roughly $2.8 \times 10^{38}$ erg. Throughout the flaring event, evolving asymmetries in the H$\alpha$ profile reveal complex
plasma dynamics.
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High Energy Astrophysical Phenomena
One year of broadband radio monitoring of the enigmatic transient GRB 250702B reveals the evolution of the relativistic jet
A. J. Goodwin, James C. A. Miller-Jones, Itai Sfaradi et al. (+18 more)
We present an extensive
radio monitoring campaign of the unique extragalactic transient GRB 250702B, with observations spanning 0.65-233 GHz from 6-356 d (observer frame) post-discovery. The
radio emission shows a smoothly evolving peaked synchrotron spectrum consistent with an adiabatic shock expanding into a stratified ambient medium ($n_e\propto R^{-k}$; $k= 1.5-2$). We detect significant variability in the low frequency ($\leq3$ GHz) light curves which we interpret as interstellar scintillation, placing an approximate bound on the blast wave image size of $1.2\times10^{16}\lesssim R_{\perp} \lesssim 5\times10^{17}$ cm. The temporal
evolution of the flux density and critical synchrotron frequencies suggest the shock that powers the
radio emission is potentially a wide-angle $\theta_j\gtrsim15$ deg, low Lorentz factor ($\Gamma\lesssim10$) jet, or a narrow $\theta_j\lesssim2$ deg highly relativistic jet. A narrow jet is expected for a
stellar-mass black hole engine, such as a helium
star merger, and the beaming-corrected kinetic energy in this scenario is consistent with the known distribution for long GRBs ($E_K\sim10^{51}$ erg). The wide-angle jet scenario would instead require a progenitor involving prolonged
accretion. We derive and show an intermediate or
stellar-mass black hole
tidal disruption event are viable possibilities. The beaming-corrected kinetic energy in this scenario is on the low end of the known distribution for relativistic SMBH TDEs ($E_K\sim10^{50}$ erg). We disfavour an SMBH TDE due to lack of compatibility with the observed timescales. The detection of a jet shut off within the next year would favour a WD-IMBH TDE due to the shorter theoretical duration of super-Eddington
accretion than the main-sequence TDE channels.
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All authors A. J. Goodwin, James C. A. Miller-Jones, Itai Sfaradi, Andrew Mummery, Raffaella Margutti, Tanmoy Laskar, K. D. Alexander, Yuhan Yao, Arvind Balasubramanian, G. C. Anupama, Edo Berger, Varun Bhalerao, Yvette Cendes, Ryan Chornock, C. T. Christy, D. Eappachen, Tarraneh Eftekhari, Miguel Pérez-Torres, Enrico Ramirez-Ruiz, D. K. Sahu, Sjoert van Velzen
Solar and Stellar Astrophysics
Investigating Possible Stellar Coronal Mass Ejections in M-type Dwarfs Using the CARMENES DR1 Spectra
Cao Dongtao and Gu Shenghong
Stellar coronal mass ejections (CMEs) have significant impacts on surrounding
exoplanets and
stellar evolution. For M-type
dwarf stars, hosting close-in habitable zones, frequent and intense
stellar CMEs may render their potentially habitable
planets uninhabitable. In this study, we used the CARMENES DR1 spectra to investigate potential
stellar CMEs in M-type
dwarfs by analyzing asymmetric features of the H{\alpha} profiles. Through a comprehensive visual inspection, we identified 61 distinct asymmetric features in the H{\alpha} line profiles across 33 M-type
dwarfs. These asymmetries were associated with increased emissions in several chromospheric activity lines, indicating likely connections to
flare events. The velocities of these features remain below the escape velocities of the investigated
stars, except for one case where an asymmetric feature's maximum velocity approaches the
star's escape velocity. While
stellar CMEs are one potential explanation, the observed features are also consistent with other
flare-related
plasma motions. The estimated moving
plasma masses range from 10^15 to 10^19 g, with corresponding kinetic energies of 10^29–10^32 erg.
Stars with asymmetric H{\alpha} profiles are generally associated with stronger surface-average
magnetic field <B> and higher normalized X-ray luminosity log(L_X/L_bol). However, we find no significant correlation between the line asymmetry rate and either <B> or log(L_X/L_bol).
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Astrophysics of Galaxies
The mass-dependent interplay of active galacitc nuclei and supernova feedback in shaping the $L_{\rm X}$–$T$ relation of early-type galaxies
Haojie Xia, Feng Yuan, Bocheng Zhu et al. (+4 more)
The observed X-ray luminosity–temperature ($L_{\rm X}$–$T$) relation of hot gas in early-type
galaxies deviates significantly from the prediction of purely gravitational heating, providing a key constraint on non-gravitational processes such as
supernova (SN) and active
galactic nucleus (AGN) feedback. We investigate the physical origin of this relation using high-resolution 3D hydrodynamical simulations with the multiscale AGN-regulated
cosmic ecosystem resolver in 3D (MACER3D) framework, which we applied to a
dwarf elliptical, a massive elliptical, and a cluster-central
galaxy. For comparison, we performed controlled simulations that included AGN winds and SN feedback in isolation, excluding cosmological inflow and environmental effects. The dominant regulation mechanism depends strongly on the
halo mass. In the cluster-central case, neither AGN winds nor SN feedback alone can sufficiently suppress the gas density and $L_{\rm X}$. When both are included, their nonlinear coupling suppresses the X-ray emission, producing ($L_{\rm X}$, $T$) values below the observed relation; this discrepancy can be resolved by incorporating AGN jet feedback. In massive elliptical
galaxies, the inclusion of AGN feedback brings the model predictions into broad agreement with the observed $L_{\rm X}$–$T$ relation, indicating that AGN feedback dominates SN feedback. At the low-mass end,
dwarf galaxy models also follow the observed trend. In this regime, models with either SN or AGN feedback alone predict low $L_{\rm X}$. When both are included, AGN wind-driven transport of SN-enriched gas to intermediate radii enhances the
metallicity and radiative cooling, thereby increasing $L_{\rm X}$. This coupled process establishes a fountain-like circulation, in which gas is repeatedly lifted and recycled within the
galaxy.
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All authors Haojie Xia, Feng Yuan, Bocheng Zhu, Haoen Zhang, Tingfang Su, Aoyun He, Suoqing Ji
Astrophysics of Galaxies
PDRs4All XXII. Near-Infrared continuum in the Orion Bar
Takashi Onaka, Emmanuel Dartois, Els Peeters et al. (+13 more)
Conspicuous excess emission is present in the near-infrared (NIR) region in various objects, including reflection nebulae, planetary nebulae, and nearby
galaxies. However, the spatial distribution and spectral shape of the excess emission remain poorly understood. We studied the NIR continuum emission spectroscopically and obtained its spatial distribution relative to the aromatic infrared band (AIB) at 3.3um in the Orion Bar prototypical photodissociation region (PDR). We aim to characterize its spectral shape and discuss its origin. We employed 3D spectroscopic data of the Orion Bar taken with the integrated field unit of NIRSpec on JWST from the Early Release Science program "PDRs4All." Contribution from the foreground ionized gas was estimated using the Cloudy code and subtracted. The observed regions were divided into nine physically distinct regions and an average spectrum was derived for each region. The nine regions, including the ionized gas, atomic PDR, and molecular PDR, clearly show remaining continuum in the region 1–4.5um. The continuum at wavelengths longer than 2.7um shows good correlations with the 3.3um AIB, while the correlation of the continuum at 1.2um is not significant. We further find that the NIR continuum in the Orion Bar can be approximated by a summation of two blackbodies. The low-temperature component correlates with the AIB well, while the high-temperature component does not. The average spectra also show absorption features at 3.0 and 4.27um, which are attributed to the presence in the spectra of water ice and CO2 ice. We discuss possible origins of the NIR continuum, among which recurrent fluorescence from carbon clusters better explains the observed low-temperature component. The presence of ice species suggests a contribution from a deeper layer of the PDR along the line of sight producing characteristic ice absorption features.
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All authors Takashi Onaka, Emmanuel Dartois, Els Peeters, Olivier Berne, Emilie Habart, Christiaan Boersma, Jan Cami, Asuncion Fuente, Javier R. Goicoechea, Ozan Lacinbala, Yoko Okada, Alexander G. G. M. Tielens, Dries Van De Putte, Francois Boulanger, Thomas Pino, Yong Zhang
Solar and Stellar Astrophysics
Lithium as a Signpost for Compact Object Binary Candidates in the LAMOST Medium Resolution Survey
Yang Shen, Joshua D. Simon, Kareem El-Badry et al. (+1 more)
Binary systems with black hole or
neutron star companions are often associated with lithium enhancement.
Gaia NS1, a recently discovered
neutron-
star binary with a lithium-enhanced main-sequence companion, demonstrates the potential of lithium as a signpost for identifying compact object binaries in existing spectroscopic surveys. In particular, we aim to use lithium as a signpost to find compact object binaries similar to
Gaia NS1 in the Large Sky Area Multi-Object Fibre Spectroscopic
Telescope (LAMOST) Medium Resolution Survey (MRS). From LAMOST MRS, we selected 4441 metal-poor main-sequence
stars like
Gaia NS1, measured the Li 6707 Å equivalent width, and then identified a sample of 33
stars with strong Li absorption. We used radial velocity variation and astrometric binarity signatures from
Gaia, narrowing the sample to 3 candidates. We identified one of these candidates as an eclipsing binary and demonstrated that massive companions for the other two are unlikely via follow-up spectroscopy.
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All authors Yang Shen, Joshua D. Simon, Kareem El-Badry, Casey Y. Lam
Earth and Planetary Astrophysics
HIP 61637 b: a TESS Brown Dwarf in a Near-circular Orbit around a Massive A-type Star
Nino Ephremidze, David W. Latham, Perry Berlind et al. (+8 more)
We present the characterization of HIP 61637 b (TOI-5401 b), a brown
dwarf discovered by TESS to transit an A-type
star. HIP 61637 is the most massive and the brightest
star known to host a transiting brown
dwarf to date. The companion lies in the middle of the "brown
dwarf desert". We perform a joint analysis of light curves from NASA's TESS mission and our high-resolution spectroscopy from the Tillinghast Reflector Echelle Spectrograph. We determine that HIP 61637 b has a radius of $R_{BD} = 1.149^{+0.049}_{-0.038}$ $R_J$, a mass of $M_{BD} = 47.8^{+1.5}_{-1.4}$ $M_J$, and transits its host
star every $6.829104 \pm 0.000011$ days in a near-circular orbit ($e = 0.054 \pm 0.013$). The host
star has a mass of $2.86\pm 0.12\,M_\odot$, a radius of $4.33 \pm 0.17\, R_\odot$, and an effective temperature of $T_{\text{eff}} = 9180^{+240}_{-230}$ K. We find that the host is nearing the end of its time on the main sequence and has begun to evolve, allowing for a precise age estimation of $396 \pm 46$ Myr for the system using
stellar evolution models. This adds an important data point to the handful of well-characterized transiting brown
dwarfs with reliable age estimates, allowing us to test the latest substellar
evolution models. Theory of
tidal evolution predicts that
tidal dissipation mechanisms have circularized the orbit, consistent with the observed near-zero eccentricity.
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All authors Nino Ephremidze, David W. Latham, Perry Berlind, Allyson Bieryla, Michael L. Calkins, Gilbert A. Esquerdo, Samuel N. Quinn, Joseph E. Rodriguez, Noah Vowell, Jack Schulte, Hugh P. Osborn
High Energy Astrophysical Phenomena
EP241113a: dissipative photospheric emission from a dirty fireball
Cui-Yuan Dai, Xiang-Yu Wang and Bing Zhang
EP241113a, a soft X-ray transient detected by the Einstein Probe (EP), has an isotropic-equivalent energy ($E_{\gamma,\rm{iso}}\sim 10^{51}{\, \rm erg}$) comparable to classical gamma-ray bursts (GRBs) but an exceptionally low peak energy ($E_{\rm{p}} \lesssim 1 \, {\rm keV}$), placing it off the canonical $E_{\rm{p}}$–$E_{\gamma,\rm{iso}}$ (Amati) relation at $>3\sigma$ confidence. The afterglow of EP241113a is also unusual, with an extremely low plateau luminosity and no jet break up to the latest observation. Such properties have been interpreted as arising from an energetic “dirty fireball,” i.e., a relativistic jet with energy comparable to classical GRBs but much higher
baryon loading, leading to a bulk Lorentz factor of $\Gamma\sim 20$. In this Letter, we propose that low $E_{\rm{p}}$ arises from dissipative photospheric emission in such a low-$\Gamma$ jet. As $\Gamma$ decreases, the photosphere shifts outward while the internal shock radius moves inward, causing dissipation to occur well below the photosphere and making the
prompt emission photosphere-dominated. Meanwhile, the thermalization radius also moves outward, reducing the comoving radiation temperature where the spectral peak is established. Combined with weaker Lorentz boosting, these effects naturally shift the observed $E_{\rm{p}}$ into the soft X-ray band. We further suggest that such a low-$\Gamma$ jet may be powered by
neutrino–antineutrino ($\nu\bar{\nu}$) annihilation in a hyperaccreting disk formed during the core collapse of a massive
star. Compared with the Blandford–Znajek process,
neutrino annihilation can produce a dirtier jet through
baryon entrainment from a
neutrino-driven wind. EP241113a-like events therefore offer new insight into the dissipation physics and launching mechanisms of jets from collapsing massive
stars.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Minimal Scale-Invariant Dark Matter
Alexander Belyaev, Roman Pasechnik, Rishav Roshan et al. (+1 more)
We study the minimal classically scale-invariant extension of the Standard Model, containing a single $\mathbb Z_2$-stabilised real scalar singlet whose mass is not an independent input but is generated dynamically through the
quantum effective potential and linked to radiative electroweak
symmetry breaking through the
Higgs portal. We construct the full two-field one-loop effective potential and introduce a modified on-shell renormalisation scheme that fixes the electroweak
vacuum, the
Higgs mass, the vanishing
Higgs–singlet mixing and the singlet
curvature at the physical point, yielding predictions stable under renormalisation-scale variation. Since thermal freeze-out is excluded by direct-detection limits, we identify a highly predictive freeze-in realisation of this model. Imposing perturbativity,
vacuum stability and the observed relic abundance leads to a freeze-in solution with a dark-matter mass of around $2~{\rm MeV}$. The predicted electron-scattering cross section for this solution lies far below the current sensitivity of DAMIC-M. Current direct-detection experiments therefore do not constrain this scenario. The minimal scale-invariant singlet model thus provides a robust and highly predictive framework connecting radiative electroweak
symmetry breaking and freeze-in dark-matter genesis.
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All authors Alexander Belyaev, Roman Pasechnik, Rishav Roshan, Alfonso Zerwekh
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Neutrino flavor-wave transport: Numerical tests and theoretical challenges
Anson Kost, Lucas Johns and Huaiyu Duan
Neutrino quantum kinetics is computationally intractable in the
neutrino-dense arenas of core-collapse
supernovae and
neutron star mergers.
Flavor-wave (or flavomon) transport is an emerging approach to this problem in which small-scale
flavor inhomogeneities are treated as quasiparticles with properties determined by the local mean background. We present the first numerical calculations of
flavor-wave transport under slow driving. Our results show some quantitative successes but also underscore the theoretical challenges that need to be overcome. Two issues are particularly concerning. (1) Nonlinear wave-wave coupling may be important. (2) Degeneracies and small energy gaps are responsible for significant nonadiabatic transitions. Future work will need to address these points if
flavor-wave transport is to be viable in settings of astrophysical interest. Other topics examined include
flavor-wave parallel transport and
flavor-space
symmetry breaking.
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