High Energy Astrophysical Phenomena
nDspec: a new Python library for modelling multi-dimensional datasets in X-ray astronomy
Matteo Lucchini, Benjamin Ricketts, Phil Uttley et al. (+1 more)
The current fleet of X-ray
telescopes produces a wealth of multi-dimensional data, allowing us to study sources in time,
photon energy, and polarisation. At the same time, it has become increasingly clear that progress in our physical understanding will only come from studying these sources in multiple dimensions simultaneously. Enabling multi-dimensional studies of X-ray sources requires new theoretical models predicting these
datasets, new methods to analyse them, and, crucially, a software framework to combine data, models, and methods efficiently. However, the current ecosystem of software packages developed for X-ray data analysis does not provide the flexibility for advanced modelling of multi-dimensional
datasets. In this paper, we introduce nDspec, a new python-based library designed to allow users to seamlessly model one- and multi-dimensional
datasets common to X-ray astronomy. Unlike most other libraries, it is designed as a flexible, modular, and extensible framework capable of accommodating multi-dimensional data and able to connect to a range of different inference tools and
algorithms. Here we focus on modelling timing and spectral-timing data as a function of both
Fourier frequency and energy, in addition to limited support for time-averaged spectra. We discuss design philosophy and current features, and showcase an example use case by characterising a NICER observation of a black hole X-ray binary. We also highlight plans for extensions to other dimensions and new features, such as the inclusion of polarimetry and the improved statistical methods for
Bayesian inference.
Read the full abstract ▾
All authors Matteo Lucchini, Benjamin Ricketts, Phil Uttley, Daniela Huppenkothen
Cosmology and Nongalactic Astrophysics
Inflation at the End of 2025: Constraints on $r$ and $n_s$ Using the Latest CMB and BAO Data
L. Balkenhol, E. Camphuis, F. Finelli et al. (+10 more)
Inflation elegantly provides initial conditions for the standard model of cosmology, while solving the horizon, flatness, and
magnetic monopole problems. Inflationary models make predictions for the tensor-to-scalar ratio $r$ and the spectral index $n_s$ of initial density fluctuations. In light of relevant data releases this year, we present constraints on these two parameters using the latest
cosmic microwave background (CMB) and
baryon acoustic oscillation data (BAO) available. Using data from Planck, the South Pole
Telescope, Atacama Cosmology
Telescope, and BICEP/Keck experiments, we derive $n_s=0.9682\,\pm\,0.0032$ and a 95% upper limit of $r<0.034$. This upper limit on $r$ is consistent with the official BICEP/Keck result given the numerical precision of the analyses and our choice to impose the self-consistency relation for single field slow-roll inflation on the tensor power spectrum; the $r$ constraint is not impacted by the additional CMB data. While adding DESI BAO data to the CMB data has a negligible impact on $r$, the $n_s$ constraint shifts upward to $0.9728\,\pm\,0.0029$, which favours monomial inflaton potentials with $N_\star \!\sim 50$ over Starobinsky $R^2$ or
Higgs inflation with $N_\star = 51$ and $N_\star = 55$, respectively. This shift is caused by marginally significant differences between the CMB and DESI data that remain unexplained in the context of the standard model. We show that a class of
polynomial $\alpha$-attractor models can predict the CMB as well as the CMB+DESI $n_s$ results. % with $N_\star =47.1$ and $N_\star=55.1$, respectively. While future data will improve our sensitivity to $r$, robust $n_s$ constraints are just as crucial to differentiate between inflation models. We make the data needed to reproduce the new CMB and BAO results and visualisation tools for $r$-$n_s$ figures available https://github.com/Lbalkenhol/r_ns_2025 .
Read the full abstract ▾
All authors L. Balkenhol, E. Camphuis, F. Finelli, K. Benabed, F. R. Bouchet, J. Carron, S. Galli, E. Hivon, A. R. Khalife, L. Knox, C. L. Reichardt, A. Vitrier, W. L. K. Wu
Cosmology and Nongalactic Astrophysics
Is Dark Energy Dynamical in the DESI Era? A Critical Review
Salvatore Capozziello, Himanshu Chaudhary, Tiberiu Harko et al. (+1 more)
We investigate whether the recent DESI DR2 measurements provide or not evidences for dynamical dark energy by exploring the $\omega_0\omega_a$CDM model and its extensions with free $\sum m_{\nu}$ and $N_{\mathrm{eff}}$. Using a comprehensive MCMC analysis with a wide range of cosmological
datasets including DESI~DR2 BAO and Ly$\alpha$ data, CMB compressed likelihoods, BBN,
cosmic chronometers, and multiple Type~Ia
supernova compilations, we assess the statistical preference for departures from $\Lambda$CDM.
Read the full abstract ▾
All authors Salvatore Capozziello, Himanshu Chaudhary, Tiberiu Harko, Ghulam Mustafa
Instrumentation and Methods for Astrophysics
FAST-MEPSA: an optimised and faster version of peak detection algorithm MEPSA
Manuele Maistrello, Romain Maccary and Cristiano Guidorzi
We present FAST-MEPSA, an optimised version of the MEPSA
algorithm developed to detect peaks in uniformly sampled time series affected by uncorrelated Gaussian noise. Although originally conceived for the analysis of gamma-ray burst (GRB) light curves (LCs), MEPSA can be readily applied to other transient phenomena. The
algorithm scans the input data by applying a set of 39 predefined patterns across multiple timescales. While robust and effective, its computational cost becomes significant at large re-binning factors. To address this, FAST-MEPSA introduces a sparser offset-scanning strategy. In parallel, building on MEPSA's flexibility, we introduce a 40th pattern specifically designed to recover a class of elusive peaks that are typically sub-threshold and lie on the rising edge of broader structures - often missed by the original pattern set. Both versions of FAST-MEPSA - with 39 and 40 patterns - were validated on simulated GRB LCs. Compared to MEPSA, the new implementation achieves a speed-up of nearly a factor 400 at high re-binning factors, with only a minor (~4%) reduction in the number of detected peaks. It retains the same detection efficiency while significantly lowering the false positive rate of low significance. The inclusion of the new pattern increases the recovery of previously undetected and sub-threshold peaks. These improvements make FAST-MEPSA an effective tool for large-scale analyses where a robust trade-off between speed, efficiency, and reliability is essential. The adoption of 40 patterns instead of the classical 39 is advisable when an enhanced efficiency in detecting faint events is desired. The code is made publicly available.
Read the full abstract ▾
Earth and Planetary Astrophysics
An analytical framework for atmospheric tides on rocky planets. I. Formulation
Pierre Auclair-Desrotour, Mohammad Farhat, Gwenaël Boué et al. (+1 more)
Atmospheric thermal tides arise from the diurnal contrast in
stellar irradiation. They exert a significant influence on the long-term rotational
evolution of rocky
planets because they can accelerate the planetary
spin, thereby counteracting the decelerating effect of classical gravitational tides. Consequently,
equilibrium tide-locked states may emerge, as exemplified by Venus and hypothesised for Precambrian Earth. Quantifying the atmospheric thermal torque and elucidating its dependence on
tidal frequency – both in the low- and high-frequency regimes – is therefore essential. In particular, we focus here on the resonance that affected early Earth, which is associated with a forced Lamb wave. Within the framework of linear theory, we develop a new analytical model of the atmospheric response to both gravitational an thermal
tidal forcings for two representative vertical temperature profiles that bracket the atmospheres of rocky
planets: (i) an isothermal profile (uniform temperature) and (ii) an isentropic profile (uniform potential temperature). Dissipative processes are incorporated via Newtonian cooling. We demonstrate that the isothermal and isentropic cases are governed by the same general closed-form solution, and we derive explicit expressions for the three-dimensional
tidal fields (pressure, temperature, density and wind velocities) throughout the spherical atmospheric shell. These results constitute the foundation for two forthcoming papers, in which analytical formulae for the thermotidal torque will be presented and compared with numerical solutions obtained from General Circulation Models (GCMs).
Read the full abstract ▾
All authors Pierre Auclair-Desrotour, Mohammad Farhat, Gwenaël Boué, Jacques Laskar
Astrophysics of Galaxies
MAUVE-MUSE: A Star Formation-driven Outflow Caught in the Act of Quenching the Stripped Virgo Galaxy NGC 4064
Amy Attwater, Barbara Catinella, Luca Cortese et al. (+10 more)
The rapid quenching of satellite
galaxies in dense environments is often attributed to environmental processes such as ram pressure stripping. However, stripping alone cannot fully account for the removal of dense,
star-forming gas in many satellites, particularly in their inner regions. Recent models and indirect observations have suggested that
star formation-driven
outflows may play a critical role in expelling this remaining gas, yet direct evidence for such feedback-driven quenching remains limited. Here we report the discovery of an ionized gas
outflow in NGC 4064, a Virgo cluster satellite that has already lost most of its cold gas through environmental stripping. MUSE observations from the Multiphase Astrophysics to Unveil the Virgo Environment (MAUVE) survey reveal a bi-polar
outflow driven by residual, centrally concentrated
star formation in NGC 4064 - despite its current
star formation rate being ~0.4 dex below the
star-forming main sequence due to prior interaction with the cluster environment. The
outflow's mass loading factor is ~2, suggesting that
stellar feedback could remove the remaining gas on timescales shorter than those required for depletion by
star formation alone. These results demonstrate that even modest but centrally concentrated
star formation can drive efficient feedback in stripped satellites, accelerating quenching in the final stages of their
evolution.
Read the full abstract ▾
All authors Amy Attwater, Barbara Catinella, Luca Cortese, Timothy Davis, Toby Brown, A. Fraser-McKelvie, Andrew Battisti, Alessandro Boselli, Pavel Jáchym, Andrei Ristea, Kristine Spekkens, Sabine Thater, Christine Wilson
High Energy Astrophysical Phenomena
Wind-mediated Eddington-limited emission in a $10^{4}M_\odot$ Black Hole Tidal Disruption Event
Paola Martire, Elena Maria Rossi, Nicholas Chamberlain Stone et al. (+3 more)
Observations of
tidal disruption events (TDEs) have already produced tens of strong candidate
flares, and their number will greatly increase with upcoming wide field surveys. Nevertheless, the origin of the measured luminosity peak at early times is still unknown, and the ultimate sources of energy dissipation in TDEs are not fully understood. Here we present the first three-dimensional end-to-end simulation of a TDE by a $10^{4}M_\odot$ intermediate mass black hole (IMBH) with realistic parameters, run with the radiation-hydrodynamics code RICH. We find that the
stellar debris fails to circularize efficiently, while a low-density, radiation-driven wind forms near pericenter and expands quasi-spherically. Radiation is advected by this
outflow and released at the photosphere, which expands to radii of $\approx10^{13}$ cm and reaches temperatures of ~few $10^{4}$K at the peak of the light curve. The resulting luminosity briefly exceeds the Eddington limit before settling near that value. We systematically test the numerical convergence of our simulation by running it at three resolutions. While the nozzle shock at pericenter may be under-resolved, we find that global results are qualitatively converged and, largely, quantitatively robust. The upcoming Vera Rubin Observatory's LSST (g and r band) and ULTRASAT (near UV) will be able to observe events like our simulated IMBH TDE up to
redshifts of z$\approx$0.1 and z$\approx$0.06, respectively.
Read the full abstract ▾
All authors Paola Martire, Elena Maria Rossi, Nicholas Chamberlain Stone, Elad Steinberg, Konstantinos Kilmetis, Itai Linial
Solar and Stellar Astrophysics
Stellar Evolution in Close Binaries: Processes and Outcomes
O. G. Benvenuto, M. A. De Vito, L. Bartolomeo Koninckx et al. (+3 more)
We discuss some aspects of
stellar evolution in binary systems. While single
stars can swell following the chemical
evolution of their interior,
stars belonging to binary systems cannot overflow the size of the Roche lobe and hydrostatic
equilibrium is strictly impossible. The system is forced to exchange mass between its members through the inner Lagrangian point. In the first part of the paper, we discuss the standard
evolution of binaries that have a non-degenerate donor
star and a compact companion. We show that the model fails when to account for the occurrence of binary
pulsars when they predict a long-standing mass transfer episode. Models including irradiation feedback and evaporation in close binaries are examined next. Following these sections, we discuss the case of systems with a black hole (BH). We show that if BHs are born non-rotating, binary interaction seems insufficient to speed them up, an indication that BH rotation is a feature present at birth. Finally, we discuss Blue Straggler
Stars detected in open and globular clusters. Since they cannot be understood as single-born
stars, we evaluate one of the proposed channels is mass transfer in close binaries, and discuss its viability and the limitations of the present models.
Read the full abstract ▾
All authors O. G. Benvenuto, M. A. De Vito, L. Bartolomeo Koninckx, M. Echeveste, M. L. Novarino, J. E. Horvath
Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
BinaryGFH-v2: Improved method to search for gravitational waves from sub-solar-mass, ultra-compact binaries using the Generalized Frequency-Hough Transform
Andrew L. Miller and Lorenzo Pierini
Observing gravitational waves from sub-
solar-mass, inspiraling compact binaries would provide almost smoking-gun evidence for
primordial black holes. Here, we develop a method to search for ultra-compact binaries with chirp masses ranging from $[10^{-2},10^{-1}]M_\odot$. This mass range represents a previously unexplored gap in gravitational-wave searches for compact binaries: it was thought that the signals would too long for matched-filtering analyses but too short for time-frequency pattern-recognition techniques. Despite this, we show that a pattern-recognition technique, the Generalized frequency-Hough (GFH), can be employed with particular modifications that allow us to handle rapidly spinning-up binaries and to increase the statistical robustness of our method, and call this improved method BinaryGFH-v2. We then design a hypothetical search for binaries in this mass regime, compare the empirical and theoretical sensitivities of this method, and project constraints on formation rate densities and the fraction of dark matter that
primordial black holes could compose in both current- and future-generation gravitational-wave detectors. Our results show that our method can be used to search for sub-
solar-mass, ultra-compact objects in a mass regime that remains to-date unconstrained with gravitational waves.
Read the full abstract ▾
Instrumentation and Methods for Astrophysics
Near Ultraviolet Transient Explorer (NUTEx): A CubeSat-Based NUV Imaging Payload for Transient Sky Surveys
Shubham Ghatul, Rekhesh Mohan, Jayant Murthy et al. (+5 more)
The Near Ultraviolet Transient Explorer (NUTEx) is a CubeSat-based near-ultraviolet (NUV) imaging payload designed for transient sky surveys and is currently under development. CubeSats are compact and cost-effective satellite platforms that have emerged as versatile tools for scientific exploration and technology demonstrations in space. NUTEx is an imaging
telescope operating in the 200-300 nm wavelength range, intended for deployment on a micro-satellite bus. The optical system is based on a Ritchey Chretien (RC)
telescope configuration, featuring a 146 mm primary mirror. The detector is a
photon-counting microchannel plate (MCP) device with a
solar-blind photocathode, paired with an in-house developed readout unit. The instrument has a wide field of view (FoV) of 4 deg, a peak effective area of approximately 18 sq cm at 260 nm, and can reach a sensitivity of 21 AB magnitude (SNR = 5) in a 1200 second exposure. The primary scientific objective of NUTEx is to monitor the night sky for transient phenomena, such as
supernova remnants, flaring M-
dwarf stars, and other short-timescale events. The payload is currently scheduled for launch in Q2 2026. This paper presents the NUTEx instrument design, outlines its scientific goals and capabilities, and provides an overview of the electronics and mechanical subsystems, including structural analysis.
Read the full abstract ▾
All authors Shubham Ghatul, Rekhesh Mohan, Jayant Murthy, Margarita Safonova, Praveen Kumar, Maheswar Gopinathan, Shubhangi Jain, Mahesh Babu S
High Energy Astrophysical Phenomena
Application of time-series analysis methods to a multiple-sector TESS observations: the case of the radio-loud blazar 3C 371
Ashutosh Tripathi, Paul J. Wiita, Ryne Dingler et al. (+4 more)
We present various time series analysis methods to analyze multiple-sector observations of bright AGN from the Transiting
Exoplanet Survey Satellite (TESS) and examine whether issues such as gaps and noise in these data can be mitigated. We determine variability timescales and search for quasi-periodicity using these methods and assess any differences. In this paper, we present an analysis of the $\approx$300-day TESS observation of a blazar 3C 371 using power spectrum density, structure-function, and weighted wavelet Z-transform approaches. To reduce the effect of gaps and noise, Continuous auto-regressive moving averages, Bartlett periodogram, and wavelet decomposition methods are used. We have also used recurrence analysis to account for the nonlinearity present in the data and to quantify variability or periodicity as the recurrent state. Considering the entirety of the TESS observations, we derive the variability timescale to be around 4.5 days. Sector-wise analysis found variability timescales in the range of 3.0–7.0 days, values that are found to be consistent using different methods. When analyzing multiple sectors together, significant variability, which could be quasi-periodic oscillations (QPOs), of duration 3–6 days in individual segments, is detected. These may be attributed to the kink instabilities developed in the jet or the existence of mini-jets inside a jet undergoing precession. We find that these methods, when applied appropriately, can be used to study the variability in TESS data. The noise present in these TESS observations can be minimized using Bartlett's periodogram and wavelet decomposition to recover the real
stochastic variability.
Read the full abstract ▾
All authors Ashutosh Tripathi, Paul J. Wiita, Ryne Dingler, Krista Lynne Smith, R. A. Phillipson, Matthew J. Graham, Lang Cui
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Cosmological and lunar laser ranging constraints on evolving dark energy in a nonminimally coupled curvature-matter gravity model
Riccardo March, Miguel Barroso Varela, Orfeu Bertolami et al. (+3 more)
We analyze a cosmological solution to the field equations of a modified
gravity model where
curvature and matter are nonminimally coupled. The current Universe's accelerated expansion is driven by a cosmological constant while the impact of the nonminimal coupling on the expansion history is recast as an effective equation of state for evolving dark energy. The model is analyzed under a tracking solution that follows the minimum of the effective potential for a scalar field that captures the modified theory's effects. We determine the conditions for the existence of this minimum and for the validity of the tracking solution. Cosmological constraints on the parameters of the model are obtained by resorting to recent outcomes of data from the DESI collaboration in combination with the Pantheon+ and Dark Energy Survey
supernovae compilations, which give compatible results that point to the presence of a dynamical behavior for dark energy. The
gravity model violates the equivalence principle since it gives rise to a fifth force that implies the Earth and Moon fall differently towards the Sun. The cosmological constraints are intersected with limits resulting from a test of the equivalence principle in the Earth-Moon system based on lunar
laser ranging data. We find that a variety of model parameters are consistent with both of these constraints, all while producing a dynamical
evolution of dark energy with similarities to that found in recent DESI results.
Read the full abstract ▾
All authors Riccardo March, Miguel Barroso Varela, Orfeu Bertolami, Giada Bargiacchi, Marco Muccino, Simone Dell'Agnello
Solar and Stellar Astrophysics
The SALT survey of helium-rich hot subdwarfs: final sample and classification
C. Simon Jeffery, Matti Dorsch, Asish Philip Monai et al. (+3 more)
A medium-resolution spectroscopic survey of helium-rich hot subdwarfs has been carried out using the Southern African Large
Telescope (SALT). Objectives include the discovery of exotic hot subdwarfs, resolving distinct subclasses, identifying evolutionary sequences, and establishing the past and future histories of many of these unusual
stars. This paper extends the sample described by Jeffery et al. (2021) (arXiv:2011.09523) from 100 to 697
stars. It describes the selection criteria and presents spectral classifications based on the MK-like Drilling system. The sample includes 283 extremely helium-rich hot subdwarfs, 17 extreme helium
stars, 110 intermediate helium-rich hot subdwarfs, as well as 21 helium-rich
stars of other types. It now represents the largest homogeneous sample of both "normal" He-sdOs and "luminous" or "hot" He-sdOs. Interesting
stars discovered include
magnetic hot subdwarfs, extremely hot pre-white
dwarfs and hot subdwarfs, including hot subdwarfs showing NV emission, one short-period binary, new extreme helium
stars and several double-subdwarf candidates. The data form the basis for kinematic and model atmosphere analyses to follow.
Read the full abstract ▾
All authors C. Simon Jeffery, Matti Dorsch, Asish Philip Monai, Edward J. Snowdon, Itumaleng Monageng, Brent Miszalski
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Nonlinear evolution of the ergoregion instability: Turbulence, bursts of radiation, and black hole formation
Nils Siemonsen and William E. East
Spacetimes with an ergoregion that is not connected to a horizon are linearly unstable. While the linear regime has been studied in a number of settings, little is known about the nonlinear
evolution of this ergoregion instability. Here, we investigate this by numerically evolving the unstable growth of a massless vector field in a rapidly spinning
boson star in full general relativity. We find that the backreaction of the instability causes the
star to become more gravitationally bound, accelerating the growth, and eventually leading to black hole formation. During the nonlinear growth phase, small scale features develop in the unstable mode and emitted radiation as nonlinear gravitational interactions mediate a direct turbulent cascade. The gravitational wave signal exhibits bursts, akin to so-called gravitational wave echoes, with increasing amplitude towards black hole formation.
Read the full abstract ▾
Astrophysics of Galaxies
Isotopomer-Specific Carbon Isotope Ratio of Complex Organic Molecules in Star-Forming Cores
Ryota Ichimura, Hideko Nomura, Kenji Furuya et al. (+2 more)
The recent observation of complex organic molecules (COMs) in interstellar ices by the James Webb Space
Telescope (JWST), along with previous gas-phase detections, underscores the importance of grain surface and ice mantle chemistry in the synthesis of COMs. In this study, we investigate the formation and carbon isotope fractionation of COMs by constructing a new astrochemical reaction network that distinguishes the position of $^{13}$C within species (e.g., H$^{13}$COOCH$_3$ and HCOO$^{13}$CH$_3$ are distinguished). We take into account the position of $^{13}$C in each species in gas and solid phase chemistry. This new model allows us to resolve isotopomer-specific $^{12}$C/$^{13}$C ratios of COMs formed in the
star-forming cores. We consider thermal
diffusion-driven radical-radical reactions on the ice surface and non-thermal radiolysis chemistry in the bulk (surface + mantle) ice. We find that carbon isotope fractionation of the functional groups in COMs appears through both non-thermal radiolysis in cold environments and thermal
diffusion in warm environments, depending on the COMs. In particular, COMs containing methyl groups show isotopomer differences in $^{12}$C/$^{13}$C ratios that reflect their formation pathways and environments. These isotopomer-resolved fractionation patterns provide a diagnostic tool to probe the origins of COMs in
star-forming cores. Our results suggest that future comparisons between high-sensitivity isotopic observations and isotopomer-specific models will be helpful for constraining the relative contributions of thermal and non-thermal formation processes of COMs.
Read the full abstract ▾
All authors Ryota Ichimura, Hideko Nomura, Kenji Furuya, Tetsuya Hama, T. J. Millar
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
A Nonlocal Realization of MOND that Interpolates from Cosmology to Gravitationally Bound Systems
C. Deffayet and R. P. Woodard
Nonlocal modifications of
gravity derive from corrections to the
quantum gravitational stress tensor which grow nonperturbatively strong during
primordial inflation and may persist to the current epoch. Phenomenological constructions have been given that realize MOND in gravitationally bound systems and, separately, reproduce all the cosmological phenomena usually ascribed to dark matter, including the
cosmic microwave background radiation,
baryon acoustic oscillations and linearized structure formation. In this work we exhibit a single model that interpolates between the two regimes.
Read the full abstract ▾
Solar and Stellar Astrophysics
Does the Babcock-Leighton dynamo operate in rapidly rotating solar-type stars? Exploration using a 3D dynamo model at different rotation rates
Vindya Vashishth and Bidya Binay Karak
The Babcock-Leighton dynamo, which relies on the generation of a poloidal field through the decay and dispersal of tilted bipolar
magnetic regions (BMRs), is a promising paradigm for explaining the features of the
solar magnetic cycle. In rapidly rotating
stars, BMRs are expected to emerge at high latitudes, which are less efficient in generating the poloidal field due to poor cross-equatorial cancellation. The operation of the Babcock-Leighton dynamo in rapidly rotating
stars is therefore questionable. We, for the first time, using a 3D kinematic dynamo model, STABLE, explore this question. By taking large-scale flows from mean-field hydrodynamics models for
stars rotating at different speeds, We conduct a series of dynamo simulations in rapidly rotating
stars, exploring the following four cases of spot deposition, each based on a different assumption about toroidal flux tube rise: (i) radial rise, (ii) parallel rise to the rotation axis, (iii) parallel rise combined with an increase in Joy's law slope with the
stellar rotation rate, and (iv) increasing time delay and spot size. We find cyclic
magnetic fields in all cases except case IV of the 1-day rotating
star, for which the
magnetic field is irregular. For the parallel-rise cases, the
magnetic field becomes quadrupolar, and for all other cases, it is dipolar. Our work demonstrates that the Babcock-Leighton dynamo may operate even in rapidly rotating
stars with starspots appearing at higher latitudes.
Read the full abstract ▾
High Energy Astrophysical Phenomena
Scintillating insights into PSR~J0737$-$3039A and the interstellar plasma of the Gum Nebula from MeerKAT
J. Askew, D. J. Reardon, R. M. Shannon et al. (+8 more)
The double
pulsar system PSR~J0737$-$3039A/B has enabled some of the most precise tests of strong-field
gravity to date. Here, we present a scintillation analysis of the system based on an 18-month observation campaign with the MeerKAT
radio telescope. We characterise this interference pattern to infer properties of scattering
plasma and the orbital geometry of the system. Our preferred model supports a scattering screen located at a distance of $D_s = 360^{+30}_{-40}$ pc. This moderately anisotropic screen of ionized gas (axial ratio $A_R = 2.4 \pm 0.2$) lies near the edge of the Gum Nebula, which is believed to be a
supernova remnant (SNR) or an \HII\, region. We estimate the expansion velocity of the nebula to be $V_{\textrm{s}} = 35 \pm 5$ km s$^{-1}$, implying a SNR age of $t \approx 1$ Myr. We also constrain the orbital orientation and inclination sense of the double
pulsar to be $\Omega = 40^{\circ} \pm 3^{\circ}$ and $i > 90^{\circ}$, respectively. Assuming standard scattering geometry, our model yields a distance estimate consistent with the parallax-derived value of $D = 770 \pm 70$ pc from very long baseline interferometry. We conclude by discussing how future models of
pulsar scintillation can enhance our understanding of the IISM and the properties of
pulsars embedded within or lying behind such intervening structures.
Read the full abstract ▾
All authors J. Askew, D. J. Reardon, R. M. Shannon, M. Bailes, F. Camilo, A. Corongiu, M. Kramer, M. E. Lower, A. Parthasarathy, A. Possenti, V. Venkatraman Krishnan
Solar and Stellar Astrophysics
FAUST XXX: Dust enhancement in the young binary L1551 IRS 5
Nicolás Cuello, Eleonora Bianchi, François Ménard et al. (+17 more)
Young binary
stars with discs provide unique laboratories to study the earliest stages of
planet formation in
star-forming environments. The detection of substructure in discs around Class I protostars challenges current models of disc
evolution, suggesting that
planets may form earlier than previously expected ($<1$ Myr). In the context of the ALMA Large Program FAUST, we present observations of the circumbinary disc (CBD) around the young binary system L1551 IRS 5. The CBD exhibits two prominent over-densities in the continuum emission at the edge of the cavity, with the Northern over-density being about 20% brighter than the Southern one. By analysing the disc morphology and kinematics of L1551 IRS 5, we delineate dynamical constraints on the binary's orbital parameters. Additionally, we present 3D hydrodynamical models of the CBD to predict both the
dust and the gas surface densities. Then, we compare the resulting synthetic observations with ALMA observations of the continuum emission at 1.3 mm and the C$^{18}$O line emission. Our analysis suggests that the density enhancements observed with ALMA in L1551 IRS 5 can be caused by interactions between the binary
stars and the CBD, leading to
dust concentration within the disc. We conclude that the observed over-density corresponds to a location where could potentially grow under favourable conditions.
Read the full abstract ▾
All authors Nicolás Cuello, Eleonora Bianchi, François Ménard, Laurent Loinard, Ricardo Hernández Garnica, Aurora Durán, Cecilia Ceccarelli, María José Maureira, Claire J. Chandler, Claudio Codella, Nami Sakai, Linda Podio, Giovanni Sabatini, Layal Chahine, Marta de Simone, Davide Fedele, Doug Johnstone, Tomoyuki Hanawa, Izaskun Jiménez-Serra, Satoshi Yamamoto
High Energy Astrophysical Phenomena
Multi-wavelength emission in resistive pulsar magnetospheres
Jérôme Pétri
In this paper, we compute a full set of
neutron star magnetosphere structures from the basic
vacuum regime to the dissipation-less force-free regime by implementing a resistive prescription for the
plasma. A comparison to the radiation reaction limit is also discussed. We investigated the impact of these resistive magnetospheres onto the multi-wavelength emission properties based on the polar cap model for
radio wavelengths, on the slot gap model for X-rays and on the striped wind model for $\gamma$-rays.} % methods heading (mandatory) {We performed time-dependent pseudo-spectral simulations of the full Maxwell equations including a resistive Ohm's law. We deduced the polar cap shape and size, the Poynting flux, the
magnetic field structure and the current sheet surface, depending on the
magnetic obliquity~$\chi$ and on the conductivity~$\sigma$. We found that the geometry of the magnetosphere close to the
stellar surface is not impacted by the amount of resistivity. Polar cap rims remain very similar in shape and size. However the Poynting flux varies significantly as well as the
magnetic field sweep-back in the vicinity of the light-cylinder. This bending of field lines reflects into the $\gamma$-ray pulse profiles, changing the $\gamma$-ray peak separation~$\Delta$ as well as the time lag~$\delta$ between the
radio pulse and $\gamma$-ray peaks. X-ray pulse profiles are also drastically affected by the resistivity. A full set of multi-wavelength light-curves can be compiled for future comparison with the third $\gamma$-ray
pulsar catalogue. This systematic study will help to constrain the amount of
magnetic energy flowing into particle kinetic energy and shared by radiation.
Read the full abstract ▾
Solar and Stellar Astrophysics
Detailed theoretical analysis of core Helium-burning stars: Mixed mode patterns I. Impact of the He-flash discontinuity and of induced semi-convection
L. Panier, G. Buldgen, M. Matteuzzi et al. (+4 more)
Space missions like CoRoT, Kepler, and TESS have made asteroseismology a powerful probe of
stellar interiors. Red
giants are key targets thanks to their rich mixed-mode oscillation spectra, which reveal properties of both core and envelope. However, current models of core helium-burning red
giants still fail to fully reproduce observed oscillation patterns, largely due to uncertainties in mixing processes such as overshooting and semi-convection. This motivates the need for better seismic constraints to refine
stellar models. We investigate how internal structural features shape asteroseismic signatures in core helium-burning
stars, focusing on the links between seismic properties and internal chemical profiles. Using an updated version of the Liege
stellar evolution code and its adiabatic oscillation code, we compute and analyse mixed-mode patterns for a range of
stellar models. Our results show that sharp chemical gradients and central overshooting strongly influence the mixed-mode spectra. Changes in overshooting modify the extent of the semi-convective region, altering the local Brunt-Vaisala frequency and thus the observed period spacing. Variations in overshooting are compensated by shifts in semi-convective layers, keeping the total mixed-core size nearly constant across models. As a result,
stellar evolution is only mildly affected, while the seismic signatures, especially the Brunt-Vaisala frequency profile, are highly sensitive to these internal adjustments.
Read the full abstract ▾
All authors L. Panier, G. Buldgen, M. Matteuzzi, R. Scuflaire, M. A. Dupret, A. Noels, A. Miglio
Earth and Planetary Astrophysics · Cross-listed from physics.space-ph
Identification and Characterization of the Topside Bulge of the Venusian Ionosphere
Satyandra M. Sharma, Varun Sheel and Martin Pätzold
Venus, in the absence of an intrinsic
magnetic field, undergoes a direct interaction between its ionosphere and the
solar wind. Previous missions, including Mariner, Venera, and the Pioneer Venus Orbiter (PVO), reported a recurring localized increase in electron density, often termed a "bulge," at altitudes between 160 and 200 km. This study investigates this topside bulge using over 200 dayside electron density profiles derived from the Venus
Radio Science experiment (VeRa) onboard the Venus Express (VEX). We employ an automated, gradient-based classification
algorithm to provide a quantitative and reproducible method for identifying and categorizing the bulge morphology into three types. Type 1 profiles exhibit a distinct secondary peak above the main V2 layer. Type 2 profiles display a shoulder-like feature near the bulge altitude. Type 3 bulges are not visually apparent but can be identified through residuals obtained after subtracting a Chapman layer fit to the V2 peak. The bulge is detected in over 80% of the analyzed profiles, with a higher occurrence during periods of low
solar activity and at lower
solar zenith angles (SZA). Type 1 morphologies are only observed at low latitudes (within $\pm 40^\circ$). The peak altitude of the bulge negatively correlates with SZA, suggesting that thermospheric cooling toward the terminator significantly influences the bulge altitude. The occurrence patterns and morphological characteristics indicate that the bulge is likely influenced by external drivers, such as
solar wind interaction, rather than being solely a result of local photochemical processes.
Read the full abstract ▾
High Energy Astrophysical Phenomena
A Systematic Study of Magnetic Fields Impacts on Neutrino Transport in Core-Collapse Supernovae
Yudong Luo, Shuai Zha and Toshitaka Kajino
We quantify the impact of strong
magnetic fields (assuming $B=B_0\cdot r_0^3/r^3$ with $B_0\gtrsim 10^{16}$ G) on the
neutrino transport in core-collapse
supernovae (CCSNe).
Magnetic fields quantize the momenta of electrons and positrons, resulting in an enhanced absorption cross section for low-energy
neutrinos and suppressed chemical potentials for $e^\pm$. We include these changes in the M1 scheme for
neutrino transport and perform 1-D CCSNe simulations with GR1D. The increased low-energy cross sections reduce the $\bar{\nu}_e$ mean energy $\langle E_{\bar\nu_e}\rangle$ while elevating the
neutrino number luminosities $\mathcal{L_\nu}$ for both ${\nu}_e$ and $\bar{\nu}_e$ due to the lower energy weighted spectra. The reduction of chemical potential enhances the $\bar{\nu}_e$ emission while suppressing that of $\nu_e$, thereby driving an increase in the electron fraction behind the stalled shock at $\sim30$–$100$ km. This further amplifies $\langle E_{\nu_e}\rangle$ through an increased electron density. Consequently,
magnetic fields amplify $L_{\nu_e}$ by increasing both $\mathcal{L}_{\nu_e}$ and $\langle E_{\nu_e}\rangle$ whereas for $\bar\nu_e$, the rise in $\mathcal{L}_{\bar\nu_e}$ is offset by a decreased $\langle E_{\bar\nu_e}\rangle$, leading to a minimal change in $L_{\bar\nu_e}$. A systematic parameter scan of dipole field configurations suggests that, for $r_0 > 30$ km, $\langle E_{\bar{\nu}_e} \rangle$ is significantly suppressed and $L_{\nu_e}$ is enhanced if $B_0 \geq {2.7} \times 10^{16}$ G. These
magnetic effects become negligible for $B_0$ below $\sim {7.4} \times 10^{15}$ G.
Read the full abstract ▾
Solar and Stellar Astrophysics · Cross-listed from physics.space-ph
Generation of proton beams at switchback boundary-like rotational discontinuities in the solar wind
Rong Lin, Fabio Bacchini, Jiansen He et al. (+2 more)
Alfvénic rotational discontinuities (RDs) are abundant in the inner heliosphere and can be used to model the boundary of switchbacks, i.e. Alfvénic
magnetic kinks. To investigate the effects of RDs on
proton kinetics, we model a pair of switchback-boundary-like RDs with a hybrid Particle-In-
Cell (PIC) approach in a 2D system. We find that, at one of the boundary RDs, a significant population of
protons remains trapped over long times, creating a secondary beam-like component with temperature anisotropy $T_\perp/T_\|\gtrsim4$ in the
proton velocity distribution function that excites ion cyclotron waves within the downstream portion of the transition layer. Further analysis suggests that the static electric field in the vicinity of the RD is the key factor in trapping the
protons. This work indicates that switchback boundaries could represent a viable environment for the creation of
proton beams in the heliosphere; it also highlights the need to investigate RD sub-structures, especially the embedded current systems of interplanetary RDs. Finally, this paper underscores the importance of high-resolution observations of the
solar wind velocity distributions around RDs.
Read the full abstract ▾
All authors Rong Lin, Fabio Bacchini, Jiansen He, Luca Pezzini, Jingyu Peng
Astrophysics of Galaxies
The LEGA-C galaxy survey: multiple quenching channels for quiescent galaxies at $z\sim1$
Angelos Nersesian, Yasha Kaushal, Marco Martorano et al. (+9 more)
We analyzed the sizes and
star-formation histories (SFHs) of 2908
galaxies with $M_\star \geq 10^9$ M$_\odot$ at $0.6 < z < 1.0$, drawn from the LEGA-C survey. The goal is to investigate the connection between
galaxy sizes with SFH,
stellar age, and
metallicity. SFHs were derived with Prospector by fitting the high signal-to-noise, high spectral resolution spectroscopy drawn from the LEGA-C DR3 together with the broadband photometry from the UltraVISTA catalog.
Galaxy sizes were measured by fitting a 2D Sérsic profile to the HST ACS~F814W images. We find diverse SFHs and quenching timescales ($\tau_\rm{q}$). The main quiescent population quenched over $\tau_\rm{q}=1.23\pm0.04$ Gyr, whereas compact post-starburst
galaxies (PSBs) quenched much faster, $\tau_\rm{q}=0.13\pm0.03$ Gyr. At fixed
stellar mass, smaller quiescent
galaxies quenched more rapidly than larger ones; at fixed size, the dependence on
stellar mass is weak. Larger quiescent
galaxies are marginally younger, quenched more slowly, and have near-
solar metallicities, while compact quiescent
galaxies are older, metal-rich, and quenched faster. PSBs formed half their mass later ($z_\rm{form}\sim1.9$) and quenched on the shortest timescales. The general trends with
galaxy size, $Z_\star$, and $z_\rm{form}$ for the quiescent populations remain consistent regardless of the method used to derive the
stellar properties. We conclude that compact quiescent
galaxies are consistent with both early, moderately fast quenching and with more rapid, late quenching. While this may suggest the existence of multiple quenching channels, our data are also compatible with a continuous distribution of quenching timescales. These findings suggest that different physical mechanisms may drive quenching across
galaxy populations, potentially leading to similar morphological outcomes despite differing evolutionary histories.
Read the full abstract ▾
All authors Angelos Nersesian, Yasha Kaushal, Marco Martorano, Arjen van der Wel, Po-Feng Wu, Rachel Bezanson, Eric F. Bell, Francesco D'Eugenio, Anna R. Gallazzi, Joel Leja, Stefano Zibetti, Sandro Tacchella
Instrumentation and Methods for Astrophysics
Estimating stellar atmospheric parameters and elemental abundances using fully connected residual network
Shuo Li, Yin-Bi Li, A-Li Luo et al. (+3 more)
Stellar atmospheric parameters and elemental abundances are traditionally determined using template matching techniques based on high-resolution spectra. However, these methods are sensitive to noise and unsuitable for ultra-low-resolution data. Given that the Chinese Space Station
Telescope (CSST) will acquire large volumes of ultra-low-resolution spectra, developing effective methods for ultra-low-resolution spectral analysis is crucial. In this work, we investigated the Fully Connected Residual Network (FCResNet) for simultaneously estimating atmospheric parameters ($T_\text{eff}$, $\log g$, [Fe/H]) and elemental abundances ([C/Fe], [N/Fe], [Mg/Fe]). We trained and evaluated FCResNet using CSST-like spectra (R $\sim$ 200) generated by degrading LAMOST spectra (R $\sim$ 1,800), with reference labels from APOGEE. FCResNet significantly outperforms traditional machine learning methods (KNN, XGBoost, SVR) and CNN in prediction precision. For spectra with g-band signal-to-noise ratio greater than 20, FCResNet achieves precisions of 78 K, 0.15 dex, 0.08 dex, 0.05 dex, 0.10 dex, and 0.05 dex for $T_\text{eff}$, $\log g$, [Fe/H], [C/Fe], [N/Fe] and [Mg/Fe], respectively, on the test set. FCResNet processes one million spectra in only 42 seconds while maintaining a simple architecture with just 348 KB model size. These results suggest that FCResNet is a practical and promising tool for processing the large volume of ultra-low-resolution spectra that will be obtained by CSST in the future.
Read the full abstract ▾
All authors Shuo Li, Yin-Bi Li, A-Li Luo, Jun-Chao Liang, Hai-Ling Lu, Hugh R. A. Jones
Cosmology and Nongalactic Astrophysics
Improved Identification of Strongly Lensed Gravitational Waves with Host Galaxy Locations
Tonghua Liu and Kai Liao
We present a
Bayesian framework that enhances the identification of strongly lensed gravitational waves (GWs) by incorporating informative positional priors from the Euclid
galaxy lens catalog. The core of our method introduces a two-step reweighting scheme: first, gravitational wave parameter estimation is performed under a uniform sky prior; the resulting posterior is then used to reweight
galaxy positions within the Euclid catalog, constructing an astrophysically informed positional prior. Comparing this Euclid-informed prior against a uniform prior within our framework reveals distinct behaviors. While the posterior estimates of the intrinsic waveform parameters show little sensitivity to the prior change, the Bayes factor for
lensing identification exhibits significant prior dependence. Crucially, for truly lensed event pairs, the Bayes factor systematically increases, whereas for unlensed pairs it decreases. This dual effect is vital for robust discrimination. Our analysis demonstrates that this multi-messenger approach significantly improves the confidence of
lensing searches. For lensed pairs, the method boosts the Bayes factor by an average factor of $\sim 10$, while effectively suppressing false positives for unlensed coincidences. This underscores the critical importance of prior specification and showcases the substantial gains achievable by synergizing gravitational-wave data with electromagnetic survey information.
Read the full abstract ▾
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Nitesh K. Dubey, Sanved Kolekar and Sudipta Sarkar
The final
equilibrium stage of
stellar evolution can result in either a black hole or a compact object such as a white
dwarf or
neutron star. In general relativity, both stationary black holes and stationary
stellar configurations are known to be axisymmetric, and black hole
rigidity has been extended to several higher
curvature modifications of
gravity. In contrast, no comparable result had previously been established for stationary
stars beyond general relativity. In this work we extend the
stellar axisymmetry
theorem to a broad class of diffeomorphism invariant metric theories. Assuming asymptotic flatness and standard smoothness requirements, we show that the Killing
symmetry implied by thermodynamic
equilibrium inside the
star uniquely extends to the exterior region, thereby enforcing rotational invariance. This demonstrates that axisymmetry of stationary
stellar configurations is not a feature peculiar to Einstein
gravity but a universal property of generally covariant gravitational theories, persisting even in the presence of higher
curvature corrections.
Read the full abstract ▾
Solar and Stellar Astrophysics
Refined M-type Star Catalog from LAMOST DR10: Measurements of Radial Velocities, $T_\text{eff}$, log $g$, [M/H] and [$\alpha$/M]
Shuo Li, Yin-Bi Li, A-Li Luo et al. (+10 more)
Precise
stellar parameters for M-type
stars, the
Galaxy's most common
stellar type, are crucial for numerous studies. In this work, we refined the LAMOST DR10 M-type
star catalog through a two-stage process. First, we purified the catalog using techniques including deep learning and color-magnitude diagrams to remove 22,496 non-M spectra, correct 2,078
dwarf/
giant classifications, and update 12,900 radial velocities. This resulted in a cleaner catalog containing 870,518 M-type spectra (820,493
dwarfs, 50,025
giants). Second, applying a label transfer strategy using values from APOGEE DR16 for parameter prediction with a ten-fold cross-validated CNN ensemble architecture, we predicted $T_\text{eff}$, $\log g$, [M/H], and [$\alpha$/M] separately for M
dwarfs and
giants. The average internal errors for M
dwarfs/
giants are respectively: $T_\text{eff}$ 30/17 K, log $g$ 0.07/0.07 dex, [M/H] 0.07/0.05 dex, and [$\alpha$/M] 0.02/0.02 dex. Comparison with APOGEE demonstrates external precisions of 34/14 K, 0.12/0.07 dex, 0.09/0.04 dex, and 0.03/0.02 dex for M
dwarfs/
giants, which represents precision improvements of over 20% for M
dwarfs and over 50% for M
giants compared to previous literature results. The catalog is available at https://nadc.china-vo.org/res/r101668/.
Read the full abstract ▾
All authors Shuo Li, Yin-Bi Li, A-Li Luo, Jun-Chao Liang, You-Fen Wang, Jing Chen, Shuo Zhang, Mao-Sheng Xiang, Hugh R. A. Jones, Zhong-Rui Bai, Xiao-Xiao Ma, Yun-Jin Zhang, Hai-Ling Lu
Astrophysics of Galaxies
Tracking Protostellar Variability in Massive Protoclusters with ALMA: I. Insights from QUARKS and MaMMOtH
Yuhan Yang, Tie Liu, Sheng-Yuan Liu et al. (+22 more)
Millimeter/submillimeter variability is often attributed to dynamical disk-mediated
accretion, yet detection is limited to low-mass protostars in nearby clouds. Recent observations have also revealed significant (sub)millimeter variability in high-mass protostars, but the confirmed cases are scarce and lack systematic monitoring. In this work, we analyzed multi-epoch Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 (1.3 mm) continuum observations of 22 massive protoclusters, with epoch separations ranging from a few hours to more than two years, while achieving a consistent angular resolution of approximately 0.3 arcsec. These data allow us to track variability of protostars across a broader mass range and in an environment markedly different from nearby clouds. Using a custom processing pipeline for data reduction, image
alignment, and relative flux calibration, we achieve high-precision flux measurements and, for the first time, investigate millimeter variability in massive protoclusters based on interferometric data in a statistical manner. Applying the astrodendro
algorithm, we identified 383 condensations and tracked their variations in peak intensities. Standard deviation analysis and difference maps reveal five variable sources, corresponding to a lower limit of 1.3% on the variable fraction. Among these, I13111-6228 stands out as it hosts a hypercompact H II region that exhibits a 68% increase in continuum peak intensity over one year, with an uncertainty of 2%.
Read the full abstract ▾
All authors Yuhan Yang, Tie Liu, Sheng-Yuan Liu, Doug Johnstone, Gregory Herczeg, Wenyu Jiao, Yu-Nung Su, Xiaofeng Mai, Fengwei Xu, Dominique Meyer, Siju Zhang, Eduard Vorobyov, Suinan Zhang, Qiuyi Luo, Guido Garay, Xi Chen, Yunfan Jiao, Qi-lao Gu, Yan-kun Zhang, Ken'ichi Tatematsu, Kee-Tae Kim, Andrey Sobolev, Sergey Parfenov, Dmitry A. Ladeyschikov, Leonardo Bronfman