Earth and Planetary Astrophysics
Shaping the Mantle: The Role of Superheated Core After Giant Impacts
You Zhou
The Moon-forming
giant impact significantly influenced the initial thermal state of Earth's mantle by generating a global magma ocean, marking the onset of mantle
evolution. Recent Smoothed Particle Hydrodynamics (SPH) simulations indicate that such a collision would produce a superheated core, whose cooling would strongly influence subsequent mantle dynamics. Here, we present systematic SPH simulations of diverse
giant-impact scenarios and show that the superheated core formed after the impact can trigger secondary mantle melting, thereby governing the final state of the magma ocean. To further quantify this effect, we employ a parameterized mantle-melting model to evaluate the influence of secondary melting on the lower mantle. Our results suggest three possible outcomes: complete mantle melting, the formation of a basal melt layer, or the initiation of an early superplume. Combined with recent two-phase magma-ocean solidification models, we infer that all three scenarios would result in basal melt layers of varying thickness, partially retaining the thermal energy of the superheated core. In the canonical Moon-forming scenario, the superheated core would rapidly transfer heat to Earth's lower mantle, causing secondary mantle melting within approximately 277-5983 years and generating either a basal melt layer or a fully molten mantle. Both outcomes would effectively erase
primordial heterogeneities in the lower mantle and impose distinct pathways for its subsequent thermal
evolution.
Read the full abstract ▾
Solar and Stellar Astrophysics
Magnetic fields in the close neighborhood of LDN 328 core
Shivani Gupta, Archana Soam, Janik Karoly et al. (+1 more)
Linearly polarized
dust emission traces the plane-of-sky
magnetic field structure, thus allowing us to investigate the role of
magnetic fields in the formation and
evolution of cloud cores. In this work, we present observations of
dust polarization at 850 $\mu{\rm m}$ wavelength toward the LDN\,328 (hereafter, L328) core and its neighborhood regions, classified as R1, R2, and R3, using the James Clerk Maxwell
Telescope (JCMT) with SCUBA-2/POL-2. This study extends our previous work on
magnetic fields in L328 across different spatial scales. We used the JCMT/POL-2 data in the near vicinity of the L328 core to study the
magnetic fields in its nearby regions. We identified clumps in these regions using the FellWalker
algorithm and derived the
dust temperature and column density by fitting the spectral energy distribution (SED) using combined JCMT and Herschel
dust continuum maps. We analyzed the
magnetic field morphology in the vicinity of the L328 core and employed the structure function analysis to determine the
magnetic field dispersion angle. We used the modified Davis-Chandrasekhar-
Fermi (DCF) method to estimate
magnetic field strengths and also derived the mass-to-flux ratio and Alfvén Mach number.
Read the full abstract ▾
All authors Shivani Gupta, Archana Soam, Janik Karoly, Chang Won Lee
Solar and Stellar Astrophysics
Investigating magnetic activity cycles in solar-like oscillators using asteroseismic data from the K2 mission
Gleb Berloff, Anne-Marie Broomhall, George T. Hookway et al. (+3 more)
We present the results of an investigation into the possible presence of
magnetic activity cycles in
stars observed in two observational campaigns by the K2 mission. This study was based on the KEYSTONE asteroseismic sample of
solar-like oscillators, which contained 20
stars for which we were able to determine whether the asteroseismic p-mode frequencies varied in time. These frequency shifts ($\delta\nu$) were determined using a cross-correlation method and using the individual mode frequencies, obtained by fitting power spectra. Three
stars were found to exhibit $\delta\nu$ larger than their associated errors ($\sigma_{\delta\nu}$) using both methods, while two more
stars exhibited $\delta\nu>\sigma_{\delta\nu}$ when the cross correlation was used and a further two
stars exhibited $\delta\nu>\sigma_{\delta\nu}$ when the fitted frequencies were used. When considering the whole sample of 20
stars, the amplitude of $\delta\nu$ showed no dependence on the large frequency separation and
metallicity. However, $\delta\nu$ was observed to increase with rotation rate and effective temperature. Our sample contained a number of evolved subgiant
stars, allowing us to expand the parameter space usually considered when comparing $\delta\nu$ with
stellar parameters. While $\delta\nu$ was small for all of the evolved
stars, one was found to have $\delta\nu>\sigma_{\delta\nu}$, raising the possibility that these evolved
stars may still exhibit variable
magnetic activity.
Read the full abstract ▾
All authors Gleb Berloff, Anne-Marie Broomhall, George T. Hookway, Mikkel N. Lund, Laura Jade Millson, Dmitrii Kolotkov
Astrophysics of Galaxies
The PAH 3.4 micron feature as a tracer of shielding in the Orion Bar and NGC 6240
N. Thatte, D. Rigopoulou, F. R. Donnan et al. (+8 more)
We have carried out a detailed analysis of the 3.4 micron spectral feature arising from Polycyclic Aromatic Hydrocarbons (PAH), using JWST archival data. For the first time in an external
galaxy (NGC 6240), we have identified two distinct spectral components of the PAH 3.4 micron feature: a shorter wavelength component at 3.395 micron, which we attribute to short aliphatic chains tightly attached to the aromatic rings of the PAH molecules; and a longer wavelength feature at 3.405 microns that arises from longer, more fragile, aliphatic chains that are weakly attached to the parent PAH molecule. These longer chains are more easily destroyed by far-ultraviolet
photons (>5eV) and PAH thermal emission only occurs where PAH molecules are shielded from more energetic
photons by dense molecular gas. We see a very strong correlation in the morphology of the PAH 3.395 micron feature with the PAH 3.3 micron emission, the latter arising from robust aromatic PAH molecules. We also see an equally strong correlation between the PAH 3.405 micron morphology and the warm molecular gas, as traced by H2 vibrational lines. We show that the flux ratio PAH_3.395/PAH_3.405 < 0.3 corresponds strongly to regions where the PAH molecules are shielded by dense molecular gas, so that only modestly energetic UV
photons penetrate to excite the PAHs. Our work shows that PAH 3.405 micron and PAH 3.395 micron emission features can provide robust diagnostics of the physical conditions of the interstellar medium in external
galaxies, and can be used to quantify the energies of the
photon field penetrating molecular clouds.
Read the full abstract ▾
All authors N. Thatte, D. Rigopoulou, F. R. Donnan, I. Garcia-Bernete, M. Pereira-Santaella, B. Draine, O. Veenema, B. Kerkeni, A. Alonso-Herrero, L. Hermosa Muñoz, G. Speranza
Cosmology and Nongalactic Astrophysics
Learning Cosmology from Nearest Neighbour Statistics
Atrideb Chatterjee, Arka Banerjee, Francisco Villaescusa-Navarro et al. (+1 more)
Extracting cosmological parameters from
galaxy/
halo catalogues with sub-percent level accuracy is an important aspect of modern cosmology, especially in view of ongoing and upcoming surveys such as Euclid, DESI, and LSST. While traditional two-point statistics have been known to be suboptimal for this task, recently proposed k-Nearest Neighbour (kNN) based summary statistics have demonstrated tighter constraining power. Building on the kNN statistics, we introduce a new field-level representation of discrete
halo catalogues - NN distance maps. We employ this technique on the
halo catalogues obtained from Quijote N-body simulation suites. By combining these maps with kNN-based summary statistics, we train a hybrid neural network to infer cosmological parameters, showing that the resulting constraints achieve state-of-the-art, if not the best, accuracy. In addition, our hybrid framework is 5-10 times more computationally efficient than some of the existing point-cloud-based ML methods.
Read the full abstract ▾
All authors Atrideb Chatterjee, Arka Banerjee, Francisco Villaescusa-Navarro, Tom Abel
Cosmology and Nongalactic Astrophysics
Cosmic Expansion Driven by Gravitational Particle Production: Toward a Complete Cosmological Scenario
P. W. R. Lima and J. A. S. Lima
A dark-energy-free cosmological model ($\Omega_{DE} \equiv 0$) based on gravitationally induced adiabatic particle creation is proposed. The thermodynamics of particle production yields an effective negative pressure that drives both
primordial inflation and late-time
cosmic acceleration. The model, characterized by four components and two free parameters ($\alpha$, $\beta$), reproduces a $\Lambda$CDM-like expansion for suitable $\alpha$, while $\beta$ introduces small but testable deviations from the
cosmic concordance model. Constraints from type Ia
Supernovae (Pantheon+SH0ES) and H(z) data indicate $\beta \simeq 0.13$, suggesting a mild departure from standard cosmology and possible relief of the $H_0$ and $S_8$ tensions. The resulting classical cosmology evolves smoothly between two extreme de Sitter phases, offering a singularity-free, unified scenario that beyond solving old cosmological puzzles opens a new perspective to handle the tensions plaguing the current
cosmic concordance model.
Read the full abstract ▾
Instrumentation and Methods for Astrophysics
PDRs4All XX. Haute Couture: Spectral stitching of JWST MIRI-IFU cubes with matrix completion
Amélie Canin, Cédric Févotte, Nicolas Dobigeon et al. (+3 more)
MIRI is the imager and spectrograph covering wavelengths from $4.9$ to $27.9$ $\mu$m onboard the James Webb Space
Telescope (JWST). The Medium-Resolution Spectrometer (MRS) consists of four integral field units (IFU), each of which has three sub-channels. The twelve resulting spectral data cubes have different fields of view, spatial, and spectral resolutions. The wavelength range of each cube partially overlaps with the neighboring bands, and the overlap regions typically show flux mismatches which have to be corrected by spectral stitching methods. Stitching methods aim to produce a single data cube incorporating the data of the individual sub-channels, which requires matching the spatial resolution and the flux discrepancies. We present Haute Couture, a novel stitching
algorithm which uses non-negative
matrix factorization (NMF) to perform a
matrix completion, where the available MRS data cubes are treated as twelve sub-
matrices of a larger incomplete
matrix. Prior to
matrix completion, we also introduce a novel pre-processing to homogenize the global intensities of the twelve cubes. Our pre-processing consists in jointly optimizing a set of global scale parameters that maximize the fit between the cubes where spectral overlap occurs. We apply our novel stitching method to JWST data obtained as part of the PDRs4All observing program of the Orion Bar, and produce a uniform cube reconstructed with the best spatial resolution over the full range of wavelengths.
Read the full abstract ▾
All authors Amélie Canin, Cédric Févotte, Nicolas Dobigeon, Dries Van De Putte, Takashi Onaka, Olivier Berné
Solar and Stellar Astrophysics
An Unusual Velocity Field in a Sunspot Penumbra
H. Balthasar, C. Denker, A. Diercke et al. (+6 more)
The photospheric Evershed flow is normally oriented radially outward, yet sometimes opposite velocities are observed not only in the chromosphere but also in the photospheric layers of the penumbra. We study the velocity field in a special case of an active region with two mature sunspots, where one of them formed several days later than the main one. Between the two spots, flux emergence is still ongoing influencing the velocity pattern. We observed the active region NOAA 12146 on August 24, 2014, with the GREGOR Fabry-Pérot Interferometer (GFPI) and the Blue Imaging Channel (BIC) of the GREGOR
solar telescope at Observatorio del Teide on Tenerife. Context data from the Helioseismic and
Magnetic Imager (HMI) onboard the
Solar Dynamics Observatory (SDO) complement the high-resolution data. In the penumbra of a newly formed spot, we observe opposite Doppler velocity streams of up to +-2 km/s very close to each other. These velocities extend beyond the outer penumbral boundary and cross also the polarity-inversion line. The properties of the
magnetic field do not change significantly between these two streams. Although the
magnetic field is almost horizontal, we do not detect large transversal velocities in horizontal flow maps obtained with the local correlation technique. The ongoing emergence of
magnetic flux in an active region causes flows of opposite directions intruding the penumbra of a pre-existing sunspot.
Read the full abstract ▾
All authors H. Balthasar, C. Denker, A. Diercke, S. J. González Manrique, C. Kuckein, J. Löhner Böttcher, R. E. Louis, M. Sobotka, M. Verma
Astrophysics of Galaxies
Constraining r-process nucleosynthesis with multi-objective Galactic chemical evolution models
M. Molero, A. Arcones, F. Montes et al. (+1 more)
The astrophysical site(s) of the r-process are uncertain, with candidates such as
neutron star mergers and magneto-rotational
supernovae predicting different event rates, delay times, and heavy-element yields.
Galactic chemical
evolution models constrain these properties by comparing model predictions with observed abundances. We explore, in a systematic and data-driven way, the astrophysical conditions under which r-process enrichment can reproduce the observed trends of multiple
neutron-capture elements in the Milky Way. Rather than assuming a fixed site, we adopt a flexible, parametric approach to test whether a common set of r-process parameters can explain the chemical
evolution of several heavy elements. We compute a grid of one-infall, homogeneous models varying: Eu yield per event, r-process event rate, enrichment delay time, and progenitor mass range. For each of the $\sim 1.5 \times 10^5$ models, we predict [X/Fe] vs. [Fe/H] trends by scaling Eu yields with the
solar r-process pattern. A multi-objective optimisation based on Pareto fronts identifies models that best reproduce the abundance trends. Best-fitting models favour short delay times ($\leq 30\ \rm Myr$), low-mass progenitors ($\sim 20-25\ \rm M_\odot$), and an effective Eu injection of $\sim 2 \times 10^{-7}\ \rm M_\odot$ per event.
Stars more massive than $\sim 80\ \rm M_\odot$ are too rare to dominate the enrichment. While heavy elements can be reproduced, lighter ones show stronger conflicts with Eu, reflecting that the
solar r-process scaling relation becomes less valid toward lighter elements. No single class of r-process events, under
solar-scaled yields, can explain light and heavy
neutron-capture elements; at least two components are required: a main r-process consistent with
solar and r-rich
stars, and a weaker component producing enhanced light r-process elements, similar to that observed in r-poor
stars.
Read the full abstract ▾
All authors M. Molero, A. Arcones, F. Montes, C. J. Hansen
Cosmology and Nongalactic Astrophysics
Constraining the Neutral Hydrogen Fraction from SKA Simulated Observation using a Double-Gaussian Decomposition Technique
Jiajun Zhang and Huanyuan Shan
The Epoch of Reionization (EoR) is a unique phase in
cosmic history, marked by the ionization of neutral hydrogen by the first luminous sources. The global neutral hydrogen fraction (x_HI) is a key observable for probing this era. This paper presents a novel, statistically robust method to extract the
evolution of x_HI from the challenging noise-dominated data from the Square Kilometre Array (SKA) Data Challenge 3b. Our approach is based on a key physical insight: the pixel value distribution in SKA intensity maps is a mixture of signals from ionized and neutral regions. We model this distribution as a superposition of two Gaussian components-one fixed at zero representing noise and ionized bubbles, and a second, offset Gaussian tracing the neutral hydrogen signal. We perform this decomposition on data grouped into three
redshift bins. The double-Gaussian model provides an excellent fit to the pixel histogram data. The derived x_HI values show a clear decreasing trend across the three
redshift bins, consistent with a progressing reionization process. And the results are consistent with the provided simulation data. This method offers a powerful, model-independent, and fully interpretable way for measuring x_HI from 21 cm data, demonstrating significant potential for application to future SKA observations.
Read the full abstract ▾
Solar and Stellar Astrophysics
Stray Light Correction for the Helioseismic and Magnetic Imager
A.A. Norton, T.L. Duvall, Jr. et al. (+7 more)
We report a point spread function (PSF) and deconvolution procedure to remove stray light from the Helioseismic and
Magnetic Imager (HMI) data. Pre-launch calibration observations, post-launch Venus transit and lunar transit data were used to develop the PSF and evaluate how well it reproduced the observed scattering. The PSF reported differs from previous stray light removal efforts since we do not use Gaussians as the central mathematical component. Instead, we use a Lorenztian convolved with an Airy function. In 2018, the HMI team began providing full-disk, stray-light-corrected data daily. Intensity, Doppler, magnetogram, and vector
magnetic field data are provided. The deconvolution uses a Richardson-Lucy
algorithm and takes less than one second per full-disk image. The results, on average, show decreases in umbral continuum intensity, a doubling of the granulation intensity contrast, increases in the total field strength, most notably in plage by $\sim$1.4–2.5 the original value, and a partial correction for the convective blueshift. Local helioseismology analyses using corrected data yield results that are consistent with those from uncorrected data, with only negligible differences, except in sunspot regions. The new data are found in JSOC with names similar to the original but with the qualifying term '$\_dcon$' or '$\_dconS$' appended, denoting whether the deconvolution was applied to the filtergrams or Stokes images. The HMI team recommends using the corrected data for improved visual clarity, more accurate irradiance reconstruction, better co-
alignment with high-resolution data, reduced errors in tracking
algorithms, and improved
magnetic field strengths.
Read the full abstract ▾
All authors A.A. Norton, T.L. Duvall, Jr., J. Schou, R.S. Bogart, J. Zhao, C. Rabello-Soares, P.J. Levens, J.T. Hoeksema, C.S. Baldner
Cosmology and Nongalactic Astrophysics
Foreground removal in HI 21 cm intensity mapping under frequency-dependent beam distortions
Athanasia Gkogkou, Victor Bonjean, Jean-Luc Starck et al. (+2 more)
Neutral hydrogen (HI) intensity mapping with single-dish experiments is a powerful approach for probing cosmology in the post-reionization epoch. However, the presence of bright foregrounds over four orders of magnitude stronger than the HI signal makes its extraction highly challenging. While all methods perform well when assuming a Gaussian beam degraded to the worst resolution, most of them degrade significantly in the presence of a more realistic beam model. In this work, we investigate the performance of SDecGMCA. This method extends DecGMCA to spherical data, combining sparse component separation with beam deconvolution. Our goal is to evaluate this method in comparison with established foreground removal techniques, assessing its ability to recover the cosmological HI signal from single-dish intensity mapping observations under varying beam conditions. We use simulated HI signal and foregrounds, covering the frequency ranges relevant to MeerKAT and SKA-Mid. The foreground removal techniques tested fall into two main categories: model-fitting methods (
polynomial and parametric) and blind source separation methods (PCA, ICA, GMCA, and SDecGMCA). Their effectiveness is evaluated based on the recovery of the HI angular and frequency power spectra under progressively more realistic beam conditions. While all methods perform adequately under a uniform degraded beam, SDecGMCA remains robust when frequency-dependent beam distortions are introduced. In the oscillating beam case, SDecGMCA suppresses the spurious spectral peak at $k_\nu \sim 0.3$ and achieves $\lesssim 5\%$ accuracy at intermediate angular scales ($10 < \ell < 200$), outperforming other methods. Beam inversion, however, remains intrinsically unstable beyond $\ell \sim 200$, setting a practical limit on the method.
Read the full abstract ▾
All authors Athanasia Gkogkou, Victor Bonjean, Jean-Luc Starck, Marta Spinelli, Panagiotis Tsakalides
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Sub-Solar Mass Intermediate Mass Ratio Inspirals: Waveform Systematics and Detection Prospects with Gravitational Waves
Devesh Giri and Bhooshan Gadre
We investigate the detectability and waveform systematics of sub-
solar mass intermediate mass-ratio inspirals (SSM-IMRIs), characterized by mass ratios $q \sim 10^2-10^4$. Using the black hole perturbation theory surrogate model BHPTNRSur1dq1e4 as a reference, we assess the performance of the IMRPhenomX phenomenological family in the high-mass-ratio regime. We find that the inclusion of higher-order gravitational wave modes is critical; their exclusion may degrade the signal-to-noise ratio by factors of $\sim3-5$ relative to quadrupole-only templates. With optimal mode inclusion, SSM-IMRIs are observable out to luminosity distances of $\sim575$ Mpc ($z\sim0.12$) with Advanced LIGO and $\sim10.5$ Gpc ($z\sim1.4$) with the Einstein
Telescope. However, we identify substantial systematic uncertainties in current phenomenological approximants. Matches between IMRPhenomX and the reference surrogate model BHPTNRSur1dq1e4 degrade to values as low as 0.2 for edge-on inclinations, and fitting factors consistently fall below 0.9, indicating a significant loss of effectualness in template-bank searches.
Bayesian parameter estimation reveals that these modeling discrepancies induce systematic biases that exceed statistical errors by multiple standard deviations, underscoring the necessity for waveform models calibrated to perturbation theory in the intermediate mass-ratio regime for robust detection and inference.
Read the full abstract ▾
High Energy Astrophysical Phenomena
Multiple Components and Spectral Evolution of BL Lacertae as Revealed by Multiwavelength Variability and SED Modeling
Hanxiao Xia, Ziming Wang, Jianghua Wu et al. (+2 more)
BL Lac has entered an active state since 2020, with multiwavelength observations revealing intense
flares. In this study, we conducted 12-night multicolor optical monitoring using an 85 cm
telescope from 2020 September to 2024 June and collected long-term broad-band archived data from
radio to $\gamma$-rays. Intraday variabilities were detected on four nights, and most of them exhibited a bluer-when-brighter behavior. Both clockwise and counterclockwise spectral hysteresis loops were found within a single night. However, no reliable intraband time lag was detected for the intranight variabilities. On long timescales, the cross-correlation analysis shows that the variations of the optical, X-ray, and $\gamma$-ray bands do not reveal an obvious time delay, while the variations in the
radio bands lagged them by about 370 days. The measured time lags suggest two distinct emission regions respectively responsible for the optical to $\gamma$-ray radiation and for the
radio radiation, with a spatial separation of approximately $4.50\times10^{19}\ \rm cm$. We modeled the broad-band spectral energy distributions during four flaring epochs and one quiescent epoch, and found evidence for the possible persistent existence of a very high energy emission region. We also confirmed a spectral
evolution of the source from an intermediate synchrotron peaked BL Lac object to a low synchrotron peaked BL Lac object.
Read the full abstract ▾
All authors Hanxiao Xia, Ziming Wang, Jianghua Wu, Yue Fang, Shiyu Du
High Energy Astrophysical Phenomena
Unveiling the nature of the Einstein Probe transient EP 241021a
J. Quirola-Vásquez, P. G. Jonker, A. J. Levan et al. (+23 more)
We present a multi-wavelength analysis of the fast X-ray transient EP 241021a, discovered by the Wide-field X-ray
Telescope aboard the Einstein Probe satellite on 2024 October 21. The event was not detected in gamma-rays. Follow-up observations from $\sim$1.5 to 100 days post-trigger were obtained across X-ray, UV, optical, near-infrared, and
radio bands with ground- and space-based facilities. The
redshift is constrained to $z = 0.7485$ from prominent optical spectral features. The optical light curve shows complex
evolution: an initial $\sim t^{-0.7}$ decay, followed by a rapid re-brightening peaking at day 7.7 with $\sim t^{-1.7}$ decay, and a third phase peaking near day 19 with $\sim t^{-1.3}$ decay. The spectral energy distribution (SED) and its temporal
evolution are consistent with a mix of non-thermal and thermal components. Early optical-to-X-ray spectral indices agree with optically thin synchrotron emission, while steepening of the optical SED after $\sim$20 days indicates either a shift in emission mechanism or the emergence of an additional component. Although broad-lined absorption features are absent, comparisons with type Ic-BL
supernovae suggest a SN contribution at late times, suggesting a collapsar origin for EP 241021a. The likely SN in EP 241021a appears to require an additional energy source beyond $^{56}$Ni decay. These results support the view that some fast X-ray transients detected by the Einstein Probe arise from massive
stellar explosions.
Read the full abstract ▾
All authors J. Quirola-Vásquez, P. G. Jonker, A. J. Levan, D. B. Malesani, F. E. Bauer, N. Sarin, G. P. Lamb, A. Martin-Carrillo, J. Sánchez-Sierras, M. Fraser, L. Izzo, M. E. Ravasio, D. Mata Sánchez, M. A. P. Torres, J. N. D. van Dalen, A. P. C. van Hoof, J. A. Chacón, S. Littlefair, V. S. Dhillon, L. Cotter, G. Corcoran, R. A. J. Eyles-Ferris, P. T. O'Brien, D. Stern, V. D'Elia, D. H. Hartmann
High Energy Astrophysical Phenomena
TransFit-CSM: A Fast, Physically Consistent Framework for Interaction-Powered Transients
Yu-Hao Zhang, Liang-Duan Liu, Ze-Xin Du et al. (+3 more)
We present TransFit-CSM, a fast and physically consistent framework for modeling interaction-powered transients. The method self-consistently couples the ejecta circumstellar medium (CSM) shock dynamics to radiative
diffusion from a moving heating boundary tied to the shocks, so that both the
photon escape path and the effective
diffusion time evolve with radius and time. We solve the mass and momentum equations for the forward and reverse shocks together with the
diffusion equation in the unshocked CSM. TransFit-CSM reproduces the canonical sequence of an early dark phase, a
diffusion-mediated rise and peak, and a post-interaction cooling tail, and it clarifies why Arnett-like peak scalings break down in optically thick CSM. The framework is well suited for
Bayesian inference and constrains physical parameters of the ejecta and CSM from bolometric or joint multi-band light curves. Applications to SN 2006gy and SN 2010jl yield accurate fits and physically interpretable posteriors, highlighting the dominant role of pre-
supernova mass loss in shaping the observables. Because it is both computationally efficient and physically grounded, TransFit-CSM bridges simple analytic prescriptions and radiation-hydrodynamic simulations, enabling population-level inference for current and future time-domain surveys.
Read the full abstract ▾
All authors Yu-Hao Zhang, Liang-Duan Liu, Ze-Xin Du, Guang-Lei Wu, Jing-Yao Li, Yun-Wei Yu
High Energy Astrophysical Phenomena
Vortex creep heating in neutron star cooling with direct Urca processes in heavy neutron stars
Yoonhak Nam and Kazuyuki Sekizawa
Old, thermally bright
neutron stars imply internal heating at late times. Among candidate mechanisms,
vortex creep heating (VCH) provides a robust link between
spin-down and frictional dissipation in the pinned inner-crust superfluid, yet its interplay with fast DUrca cooling in massive
stars remains insufficiently explored. We (i) implement VCH in our cooling code and validate it; (ii) identify the physically consistent domain where the steady-state form $L_{\text{h}}=J|\dot\Omega_\infty|$ applies; (iii) quantify how $(B,P_0)$ regulate observable VCH signatures under DUrca cooling; and (iv) introduce a 3D representation that resolves degeneracies hidden in standard 2D projections. Cooling is computed with BSk24 and APR EoS, standard pairing gaps, and iron/carbon envelopes. VCH is modeled with $J\simeq10^{42.9\text{--}43.8}$ erg s, and a
quantum-creep coverage fraction $f_{\text{Q}}(t)$ diagnoses when steady-state heating is valid. We survey $B=10^{10\text{--}13}$ G and $P_0=10$–$570$ ms for $1.4$ and $2.0\,M_\odot$, and compare with a curated set of ordinary
pulsars with measured $(P,\dot P)$. Results: (1) Our implementation reproduces published VCH bands. (2) The $(B,P_0)$ validity boundary follows
magnetic-dipole
spin-down, confirming consistency with $|\dot\Omega|$. (3) DUrca+VCH maintains $T_{\text{s}}^\infty\gtrsim10^5$ K for $B\gtrsim10^{11-12}$ G up to $P_0\sim10^2$ ms. (4) The 3D representation shows that sources appearing coincident in $(t,T_{\text{s}}^\infty)$ occupy distinct $B$-layers, removing degeneracies. VCH can substantially reshape late-time thermal states when
spin-down power remains high; its observability depends chiefly on $(B,P_0)$ rather than on mass alone. We provide a practical $(B,P_0)$ validity map for $L_{\text{h}}=J|\dot\Omega_\infty|$ and advocate treating $B$ as a co-equal axis in cooling analyses. (Shortened due to the arXiv words limit.)
Read the full abstract ▾
Solar and Stellar Astrophysics
The Spontaneous Genesis of Solar Prominence Structures Driven by Supergranulation in Three-Dimensional Simulations
Huanxin Chen, Chun Xia and Hechao Chen
Solar prominences usually have a horizontally elongated body with many feet extending to the
solar surface, resembling a multi-arch bridge with many bridge piers. The basic mechanism by which
solar prominences acquire these common structures during their
evolution, however, remains an unresolved question. For the first time, our three-dimensional magneto-frictional simulation, driven by supergranular motions, self-consistently replicates the commonly observed multi-arch bridge morphology and its characteristic structures of
solar quiescent prominences in a
magnetic flux rope. In comparison with traditional views, our simulations demonstrate that the spine, feet, and voids (bubbles) are inherent prominence structures spontaneously forming as the flux rope evolves to a mature state. The voids mainly consist of legs of sheared
magnetic loops caused by unbalanced supergranular flows, and prominence feet settle at the bottom of helical field lines piled up from the photosphere to the spine. Similarities between the simulated prominences and observed real prominences by the Chinese H$\alpha$
Solar Explorer, the New
Vacuum Solar Telescope, and NASA's
Solar Dynamics Observatory suggest the high validity of our model. This work corroborates the pivotal role of photospheric supergranulation as a helicity injection source in the formation and shaping of quiescent prominence structures within the
solar atmosphere, thereby paving a new avenue for future investigations into their fine dynamics and stability.
Read the full abstract ▾
Instrumentation and Methods for Astrophysics
Natural gradient descent for improving variational inference based classification of radio galaxies
Devina Mohan and Anna M. M. Scaife
Bayesian neural networks (BNNs) are most commonly optimised with first-order optimisers such as
stochastic gradient descent. However, when optimising for parameters of probabilistic models, incorporating second order information during optimisation can lead to a more direct path in the distribution space and faster convergence. In this work we examine whether using natural gradient descent can improve the performance of variational inference based classification of
radio galaxies. We use the Improved Variational Online Newton (iVON)
algorithm and compare its performance against a recent
benchmark for BNNs for
radio galaxy classification. We find that iVON results in better uncertainty calibration out of all the methods previously considered while providing similar predictive performance to the best performing inference methods such as
Hamiltonian Monte Carlo and Bayes by Backprop based variational inference. Models trained with iVON can distinguish far out-of-distribution optical
galaxy data, but they cannot reliably detect
radio galaxy images from a
telescope with different resolution and sensitivity. We find that the cold posterior effect persists in the models trained with iVON. Our results suggest that the choice of the optimiser can lead to qualitatively different solutions and future work using probabilistic neural network models should carefully consider the inductive biases being encoded through the optimisation process, in addition to the data, architecture and inference method.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics
Probing the Nature of Dark Matter Self-Interactions Through Observations of Massive Black Hole Mergers
Zachary J. Hoelscher, Kelly Holley-Bockelmann, Akaxia Cruz et al. (+1 more)
Though the nature of dark matter remains elusive, two models have come to prominence with testable predictions: cold dark matter (CDM) and self-interacting dark matter (SIDM). While CDM remains the widely accepted model, SIDM was introduced to potentially help resolve the discrepancies between the predictions of the CDM model and observational data, in particular the predicted central density profiles. Previous work involving simulations of small numbers of Milky Way-mass
galaxies shows that SIDM with a constant cross section of 1 $\rm{cm^2/g}$ delays massive black hole (MBH) mergers as compared to CDM when the host
halo has a flattened central density profile. In this work, we use mock gravitational wave observations of MBH mergers to test LISA's capability to indirectly probe dark matter physics. As a proof of concept, we use zoom-in simulations of two
galaxy evolutionary histories to show that LISA may be able to distinguish (with a p–value $\leq$ 0.05) between CDM and SIDM with a short-range interaction and a constant cross section of 1 $\rm{cm^2/g}$, provided at least $\sim70$ MBH mergers are observed with signal-to-noise ratios greater than 10. Given our small sample size, this should be regarded as illustrative, rather than definitive. We emphasize that our work does not consider more realistic models with a velocity-dependent cross section, though our exploratory work shows that LISA may provide a pathway to probe dark matter self-interactions, motivating future work with more realistic, currently-favored models and larger simulation suites.
Read the full abstract ▾
All authors Zachary J. Hoelscher, Kelly Holley-Bockelmann, Akaxia Cruz, N. Nicole Sanchez
Solar and Stellar Astrophysics
Spectral component imaging of solar X-ray flares
Muriel Zoë Stiefel, Paolo Massa, Alessia Guidetti et al. (+2 more)
Solar hard X-ray observations provide diagnostics of the hottest
plasmas and of nonthermal electron populations present during
solar flares and coronal mass ejections. HXR images of specific energy ranges often contain overlapping contributions of these components, complicating their interpretation. This is even more challenging as HXR imagers generally use an indirect imaging system. Our work aims to separately image individual spectral components, such as thermal loops, superhot sources, and nonthermal footpoint sources, rather than obtaining images of specific energy ranges that show a combination of all components. We introduce a new method called spectral component imaging and apply it to observations provided by the Spectrometer/
Telescope for Imaging X-rays (STIX) aboard
Solar Orbiter. First, the
flare integrated HXR spectrum is fitted with individual spectral components to get the relative contributions of each component in each native STIX energy channel. In a second step, a set of linear equations is created based on these weights and the observed, energy-dependent STIX visibilities. The visibilities of the individual spectral components are derived by means of a linear least-squares approach and are subsequently utilized for image reconstructions. We demonstrate the effectiveness of spectral component imaging on four different
flares observed by STIX. This method provides powerful diagnostics, particularly for
flares with hot and superhot components, allowing us to spatially separate these two thermal components. We apply our methodology to the nonthermal peak of the X7.1
flare SOL2024-10-01, and we find that the superhot component is located 4.8 Mm away from the hot thermal loops. The thermal energy of the superhot component is approximately 20% of the energy content of the hot component, highlighting the significance of superhot components in the total
flare energy budget.
Read the full abstract ▾
All authors Muriel Zoë Stiefel, Paolo Massa, Alessia Guidetti, Marina Battaglia, Säm Krucker
Astrophysics of Galaxies
Infrared photometry and CaT spectroscopy of the most metal-poor in-situ globular cluster VVV-CL001
W. Haro Moya, C. Moni Bidin, M.C. Parisi et al. (+11 more)
Globular clusters in the
Galactic bulge are difficult to study due to high extinction and severe crowding. VVV-CL001 is an old, metal-poor, and fast cluster in the inner bulge, whose extreme properties make it a key probe of the early chemical and dynamical
evolution of the Milky Way. We derive its fundamental parameters by combining spectroscopy, astrometry, and near-infrared photometry.
Metallicity and radial velocity were measured from medium-resolution FORS2/VLT spectra; proper motions from
Gaia DR3; and FourStar/Magellan photometry was used to refine the cluster centre, derive its structure, and estimate age, distance, and reddening. VVV-CL001 is confirmed to be an old ($12.1^{+1.0}_{-1.2}$ Gyr), metal-poor ($[\text{Fe}/\text{H}] = -2.25 \pm 0.05$) cluster at a heliocentric distance of $7.1^{+1.3}_{-1.1}$ kpc, with reddening $E(J-K_s) = 1.40^{+0.01}_{-0.02}$. Its mean proper motions are $\mu_\alpha^* = -3.68 \pm 0.09$ and $\mu_\delta = -1.76 \pm 0.10$ mas yr$^{-1}$, and its radial velocity is $-334 \pm 4$ km s$^{-1}$. The orbit is eccentric ($e = 0.76^{+0.10}_{-0.14}$), confined to the inner
Galaxy ($|Z|_{\max} \approx 1$ kpc) and within the bar's influence ($R < 5$ kpc), with pericentre $0.6^{+0.3}_{-0.2}$ kpc and apocentre $4.5^{+2.5}_{-1.2}$ kpc. Its old age, low
metallicity, and orbital properties support an in-situ origin, identifying VVV-CL001 as one of the most metal-poor inner-
Galaxy clusters formed in the early Milky Way. It likely belongs to the
primordial disk cluster population later trapped by the bar, making it a fossil remnant of the earliest phases of
Galactic assembly.
Read the full abstract ▾
All authors W. Haro Moya, C. Moni Bidin, M.C. Parisi, D. Geisler, M. Blaña, S. Villanova, F. Mauro, A.-N. Chené, R. E. Cohen, S. Ramírez Alegría, R. Contreras Ramos, M. Zoccali, C. Muñoz, B. Dias
High Energy Astrophysical Phenomena
Observational properties of a Schwarzschild black hole surrounded by a Dehnen-type dark matter halo
Zhi Li and Jiancheng Yu
This study investigates the
accretion process and observational signatures of thin
accretion disks around a Schwarzschild black hole (BH) embedded in a Dehnen-type dark matter (DM)
halo. We examine the influence of the density {\rho}_{s} and radius r_{s} of the DM
halo on key disk properties, including the energy flux, temperature distribution, and emission spectrum. Our results show that all three of these quantities decrease with increasing {\rho}_{s} or r_{s}. Furthermore, by generating and analyzing both direct and secondary images of the
accretion disk, we explore how the observational inclination angle and the DM
halo parameters {\rho}_{s} and rs affect image profiles. Finally, the observed flux distributions are presented for different inclination angles. Our findings indicate that the
accretion disk becomes colder and dimmer as the DM
halo parameters increase, highlighting the significant role of DM in shaping BH observables.
Read the full abstract ▾
Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
Towards an anomaly detection pipeline for gravitational waves at the Einstein Telescope
Gianluca Inguglia, Huw Haigh, Kristyna Vitulova et al. (+1 more)
We present the implementation of an anomaly-detection
algorithm based on a deep convolutional autoencoder for the search for gravitational waves (GWs) in time-frequency spectrograms. Our method targets short-duration ($\lesssim 2\,\text{s}$) GW signals, exemplified by mergers of compact objects forming or involving an intermediate-mass black hole (IMBH). Such short signals are difficult to distinguish from background noise; yet their brevity makes them well-suited to machine-learning analyses with modest computational requirements. Using the data from the Einstein
Telescope Mock Data Challenge as a
benchmark, we demonstrate that the approach can successfully flag GW-like transients as anomalies in interferometer data of a single detector, achieving an initial detection efficiency of 23% for injected signals corresponding to IMBH-forming mergers. After introducing weak supervision, the model exhibits excellent generalisation and recovers all injected IMBH-forming mergers, independent of their total mass or signal-to-noise ratio, with a false-alarm rate due to statistical noise fluctuations of approximately 4.5 events per year for a single interferometer operating with a 100% duty cycle. The method also successfully identifies lower-mass mergers leading to the formation of black holes with mass larger than $\simeq 20\,M_\odot$. Our pipeline does not yet classify anomalies, distinguishing between actual GW signals and noise artefacts; however, it highlights any deviation from the learned background noise distribution for further scrutiny. These results demonstrate that anomaly detection offers a powerful, model-independent framework for future GW searches, paving the way toward fully automated and adaptive analysis pipelines.
Read the full abstract ▾
All authors Gianluca Inguglia, Huw Haigh, Kristyna Vitulova, Ulyana Dupletsa
High Energy Astrophysical Phenomena
Prospects for detecting periodic or sharp fast-time features in the supernova neutrino lightcurve with IceCube
Jakob Beise, María Durán de las Heras, Segev BenZvi et al. (+5 more)
Neutrinos produced in core-collapse
supernova offer a direct probe into the hydrodynamics and energy transport mechanisms during the collapse and play a pivotal role in the shock revival and success of the
supernova explosion. Fast-time features of the
neutrino luminosity and energy spectrum encode information about phenomena such as
turbulence, convection, shock revival and potential
quark-
hadron phase transitions. In this study, we explore the detection capabilities of large-volume
neutrino telescopes with a focus on IceCube and the planned extension IceCube-Gen2. Furthermore, we consider the effect on the detection sensitivity from wavelength shifters through enhanced light collection. A variety of models predict periodic fast-time features in
supernova light curves; to quantify their detectability without relying on specific models, we investigate the detector response to a generic parameterisation of such features. We find that independent of feature frequency, IceCube-Gen2 instrumented with wavelength shifters has sensitivity to weaker modulations ($>25\%$ amplitude) as compared to only the strongest modulations ($>50\%$ amplitude) with IceCube. In addition, we examine the sensitivity of the
neutrino lightcurve to sharp features from a
quark-
hadron phase transition. Phase transitions leading to a
quark star remnant are detectable with IceCube at $5\sigma$ up to the edge of the
Galaxy, and throughout the Small Magellanic Cloud with IceCube-Gen2 equipped with wavelength-shifters. In contrast, models collapsing into a black hole are observable only within the
Galaxy, covering $41\%$ of the CCSNe population for IceCube and nearly all ($91\%$) for IceCube-Gen2 complemented by wavelength shifters. These results highlight the potential of IceCube-Gen2 for detecting
Galactic sources more reliably and with greater reach.
Read the full abstract ▾
All authors Jakob Beise, María Durán de las Heras, Segev BenZvi, Spencer Griswold, Nora Valtonen-Mattila, Evan O'Connor, David Barba-González, Erin O'Sullivan
Instrumentation and Methods for Astrophysics
Wide-Field X-ray Polarimetry for High Energy Astronomical Transients: First results of the pathfinder CXPD Cubesat Mission
Hong-Bang Liu, Zu-Ke Feng, Huan-Bo Feng et al. (+27 more)
The Low Energy Polarization Detector (LPD) is a key component of the next-generation large-scale Gamma-Ray Burst polarimeter, POLAR-2. It is designed for polarization observations of transient sources in the soft X-ray energy range with a wide field of view (FOV). To validate the key technologies required for wide-FOV X-ray polarization measurements, the
Cosmic X-ray Polarization Detector (CXPD) CubeSat was developed as a prototype for the LPD. The CXPD is equipped with two Gas Microchannel Plate Pixel Detectors (GMPDs) that measure X-ray polarization via the photoelectric effect, where ejected photoelectrons produce ionization tracks in the gas which are imaged to reconstruct their emission directions. Laboratory calibrations of the modulation factor and energy spectra were successfully performed using linear polarized X-ray sources at 2.98 keV, 4.51 keV, 6.40 keV, and 8.05 keV. Since its launch in June 2023, the CXPD has successfully completed critical in-orbit technology verification. It has also performed polarization observations of two bright X-ray sources Sco X-1 and the transient Swift J1727.8-1613 yielding constraints on their polarization degrees and angles. Notably, this was the first time that an anti-coincidence detector had been implemented in an X-ray polarimeter, enabling in-orbit verification of the charged-particle background rejection
algorithm. These results demonstrate the feasibility of wide-field soft X-ray polarization measurements and provide essential guidance for the development of the LPD for the POLAR-2 mission, thereby advancing the frontier of X-ray polarization astronomy.
Read the full abstract ▾
All authors Hong-Bang Liu, Zu-Ke Feng, Huan-Bo Feng, Di-Fan Yi, Li-Rong Xie, Yan-Jun Xie, Zong-Wang Fan, Jin Zhang, Wen-Jin Xie, Xue-Feng Huang, Wei Deng, Fei Xie, Dong Wang, Zi-Li Li, Hui Wang, Ran Chen, Shi-Qiang Zhou, Kai Chen, Jin Li, Qian Liu, Shi Chen, Rui-Ting Ma, Bin-Long Wang, Zhen-Yu Tang, Hang-Zhou Li, Bo Peng, Shu-Lin Liu, Xiang-Ming Sun, Yang-Heng Zheng, En-Wei Liang
Cosmology and Nongalactic Astrophysics
Topological Signatures of Heating and Dark Matter in the 21 cm Forest
Hayato Shimabukuro
We show that persistence-based
topology of the 21 cm forest encodes information about
Cosmic Dawn that is complementary to traditional amplitude- or correlation-based statistics. Applying topological data analysis to simulated one-dimensional forest spectra over a grid of X-ray heating efficiencies $f_X$ and warm-dark-matter masses $m_{\rm WDM}$ (which set the free-streaming scale), we construct persistence diagrams and Betti-0 curves that track the birth-merger hierarchy of absorption troughs under sublevel filtrations. From these summaries we define three interpretable descriptors: the trough line density $\lambda(t_\star)$, the total squared persistence $M_2=\sum_{j\in I_{\rm long}}\tau_j^2$, and the Betti-curve asymmetry $A_{\rm skew}$. In a Fisher forecast around a fiducial WDM model, $\lambda(t_\star)$ and $A_{\rm skew}$ provide strong local leverage on the heating axis, while $M_2$ retains appreciable sensitivity to the free-streaming scale and supplies an inclined constraint direction that reduces the remaining degeneracy in the $(f_X,m_{\rm WDM})$ plane. We further demonstrate that, under an SKA1-Low-like uncorrelated thermal-noise model, noise predominantly produces short-lived fluctuations that are removed by a uniform persistence cut, leaving the
topology of long-lived troughs and the gross Betti-curve morphology largely intact. These results establish persistence-based descriptors as a robust non-Gaussian probe of small-scale structure and heating during
Cosmic Dawn, naturally complementing power-spectrum and wavelet-based analyses.
Read the full abstract ▾
Solar and Stellar Astrophysics
The B[e] Phenomenon in Supergiants. A Result of Mass Transfer in Binaries, Mergers, or What?
Anatoly S. Miroshnichenko, Sergey V. Zharikov, Nadezhda L. Vaidman et al. (+1 more)
The B[e] phenomenon discovered nearly 50 years ago features the presence of forbidden emission lines due to extended and dense circumstellar gas and large IR excesses due to the radiation from circumstellar
dust in a wide variety of objects from pre-main-sequence
stars to Planetary Nebulae. It also shows up in a small group of supergiants that includes Luminous Blue Variables, such as {\eta} Carinae. Over the years, some of them were proven to be binary systems, but the presence of a secondary component in other is still elusive. At the same time, there is growing evidence that the B[e] phenomenon can be due to binary mergers or interactions in triple systems.
Read the full abstract ▾
All authors Anatoly S. Miroshnichenko, Sergey V. Zharikov, Nadezhda L. Vaidman, Serik A. Khokhlov
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Chiral Magnetic Effect induced Spectator Process for Leptogenesis
Wei Chao
Conventional Leptogenesis mechanism, which provides compelling explanation to the origin of the
baryon asymmetry of the universe (BAU), assumes the absence of hypermagnetic field in the early universe, thereby disregard the implications of hyper gauge field helicity, that have been thoroughly studied in the magnetogenesis mechanism. In this paper, we address impacts of a general U(1) gauge field on Leptogenesis by deriving equation of motions for the helicity and the energy density of a general
magnetic field, to which the
chiral magnetic effect (CME) is identified as essential, and studying their effects on the
evolution chiral asymmetries. Notably, CME in the $U(1)_{\mathbf{L}_i-\mathbf{L}_j}$ framework, where $\mathbf{L}_{i,j}$ means specific
lepton flavor, explicitly breaks the total
lepton number and provides an efficient spectator process, that can wash out pre-existing
lepton asymmetries. This establishes a natural connection to the wash-in Leptogenesis paradigm. We demonstrate that this spectator effect enables the generation of the BAU, eliminating the need for both an initial $\mathbf{B}-\mathbf{L}$ charge and
primordial helicity.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics
Reheating and Inflationary dynamics driven by an inverse tangent potential
Mayur Abhisheki and Prasanta Kumar Das
In this work, we study the early universe inflation and the post-inflation reheating era employing an inverse tangent potential of the form $V=V_0 \cdot[tan^{-1}(\frac{\kappa \phi}{m_p})]^2$, where $\kappa$ is a free parameter of the potential and $m_p$ is the reduced Planck mass. We derive the slow roll parameters, the number of e-folds(N), the scalar spectral index $n_s$, the tensor-to-scalar ratio $r$, and the tensor spectral index $n_T$ for the inverse tangent potential. We examine the inflationary observables using the data of the Planck-2018 and recent ACT collaboration and obtain constraints on the potential parameter $\kappa$. We also employ a reheating analysis by invoking the conservation of
entropy between today and the time when reheating starts. We obtain bounds on the reheating temperature $T_{re}$ and the number of e-folds of the reheating $N_{re}$ using the spectral-index $n_s$ constraints from Planck 2018 and the ACT results. We show that this inverse-tangent potential can act as an alternative to the standard inflationary potentials like Starobinsky which are excluded at $2\sigma$ level by the recent sixth data release (DR6) of the Atacama Cosmology
Telescope (ACT) collaboration.
Read the full abstract ▾