Solar and Stellar Astrophysics
Time-dependent Turbulent Electron Acceleration and Transport in Solar Flares
Luiz A. C. A. Schiavo, Natasha L. S. Jeffrey, Gert J. J. Botha et al. (+1 more)
Solar flares are explosive releases of
magnetic energy stored in the
solar corona, driven by
magnetic reconnection. These events accelerate electrons, generating hard X-ray emissions and often display Quasi Periodic Pulsations (QPPs) across the energy spectra. However, the energy transfer process remains poorly constrained, with competing theories proposing different acceleration mechanisms. We investigate electron acceleration and transport in a flaring coronal loop by solving a time-dependent Fokker-Planck equation. Our model incorporates transient turbulent acceleration, simulating the effects of impulsive energy input to emulate the dynamics of time-dependent reconnection processes. We compute the density-weighted electron flux, a diagnostic directly comparable to observed X-ray emissions, across the energy and spatial domains from the corona to the chromosphere. We investigate different time-dependent functional forms of the turbulent acceleration, finding that the functional form of the acceleration source maintains its signature across energy bands (1 to 100 keV) with a response time that is energy dependent (with higher energy bands displaying a longer response time). In addition, we find that (a) for a square pulse the switch on and off response time is different; (b) for a sinusoidal input the periodicity is preserved; and (c) for a damped sinusoidal the decay rate increases with density and higher energy bands lose energy faster. This work presents a novel methodology for analyzing electron acceleration and transport in
flares driven by time-dependent sources.
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All authors Luiz A. C. A. Schiavo, Natasha L. S. Jeffrey, Gert J. J. Botha, James A. McLaughlin
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Ghost instabilities and strong coupling in quadratic non-metricity theories
Alexander Ganz and Marco Spinelli
We revisit the framework of Newer General Relativity, defined by all independent quadratic invariants of the non-metricity tensor, including the unique quadratic parity-violating term. We analyze linear perturbations around a flat FLRW background and find that the theory generically exhibits ghost instabilities and/ or propagates more degrees of freedom than in the Minkowski limit, signalling strong coupling. There are two notable exceptions: the Symmetric Teleparallel Equivalent of General Relativity (STEGR) and the transverse-diffeomorphism-invariant
gravity subclass, both of which are supplemented by the parity-violating operator. However, since the parity-violating term explicitly breaks (transverse) diffeomorphism invariance, we show, using both the Dirac-Bergmann procedure and the Cartan-Kuranishi
algorithm, that the parity-violating extension of STEGR propagates eight degrees of freedom at the fully non-linear level.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Black hole binaries in shift-symmetric Einstein-scalar-Gauss-Bonnet gravity
Maxence Corman, Llibert Aresté Saló and Katy Clough
In shift-symmetric Einstein-scalar-Gauss-Bonnet
gravity, stationary black holes have a non-vanishing scalar charge. During the inspiral, the phase
evolution is modified by several effects,primarily an additional scalar dipole radiation, which enters at -1PN order. Including corrections up to 2PN, this effect accelerates the inspiral when compared to general relativity, but changes in the conservative dynamics may do the opposite. Using fully non-linear numerical simulations of quasi-circular, comparable mass binaries, we characterize the late stages of the orbital dynamics. We find that the overall effect is still an accelerated merger phase for the modified
gravity case, but noticeably less than predicted by PN alone, which we relate to the conservative dynamics, showing that at the late inspiral stage more energy must be emitted in scalar-Gauss-Bonnet
gravity to induce a given change in frequency. In longer signals, this may lead to a distinctive frequency
evolution relative to general relativity as the binary approaches merger, but its effect close to merger is to suppress the difference with GR. This work suggests we may need to revisit existing constraints on the theory that are obtained assuming PN approximations apply up to merger, or based on order by order approximations that neglect backreaction effects on the metric, and shows the importance of including non-linear effects that modify the gravitational sector in the strong field regime.
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Solar and Stellar Astrophysics
Multi-height probing of horizontal flows in the solar photosphere
Teodor Kostić, Ivan Milić, Matthias Rempel et al. (+4 more)
We tested whether simultaneous spectropolarimetric imaging in two magnetically sensitive optical spectral lines, which probe two different layers of the
solar atmosphere (the photosphere and the temperature minimum), can help constrain the depth variation of horizontal flows. We first tested the feasibility of our method using
Fourier local correlation tracking (FLCT) to track physical quantities at different optical depths ($\log\tau_{500}={-1,-2,-3,-4}$) in an atmosphere simulated with the MURaM code. We then inferred the horizontal distribution of the LOS
magnetic field component from synthetic spectropolarimetric observations of Fe I 525.0 nm and Mg I b2 spectral lines, applied FLCT to the time sequence of these synthetic magnetograms, and compared our findings with the original height-dependent horizontal velocities. Tracking the LOS
magnetic field component (which coincides with the vertical component at the disk center) yields horizontal velocities that, after appropriate temporal and spatial averaging, agree excellently with the horizontal component of the simulated velocities, both calculated at constant $\tau_{500}$ surfaces, up to the temperature minimum ($\log\tau_{500}=-3$). When tracking the temperature at constant $\tau_{500}$ surfaces, this agreement already breaks down completely at the mid photosphere ($\log\tau_{500}=-2$). Tracking the vertical component of the
magnetic field inferred from synthetic observations of the Fe I 525.0 nm and the Mg I b2 spectral lines yields a satisfactory inference of the horizontal velocities in the mid-photosphere ($\log\tau_{500}\approx-1$) and the temperature minimum ($\log\tau_{500}\approx-3$), respectively. Our results indicate that high-spatial-resolution spectropolarimetric imaging in
solar spectral lines can provide meaningful information about the horizontal
plasma velocities over a range of heights.
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All authors Teodor Kostić, Ivan Milić, Matthias Rempel, Brian T. Welsch, Maria D. Kazachenko, Andrés Asensio Ramos, Benoit Tremblay
Earth and Planetary Astrophysics
Chondrule formation by collisions of planetesimals containing volatiles triggered by Jupiter's formation
Sin-iti Sirono and Diego Turrini
Chondrules are spherical or subspherical particles of crystallized or partially crystallized
liquid silicates that constitute large-volume fractions of most chondritic meteorites. Chondrules typically range $0.1-2\,$mm in size and solidified with cooling rates of $10-1000\,{\rm K\,h^{-1}}$, yet these characteristics prove difficult to reconcile with proposed formation models. We numerically show that collisions among planetesimals containing volatile material naturally explain both the sizes and cooling rates of chondrules. We show that the high-velocity collisions with volatile-rich planetesimals first induced in the
solar nebula by Jupiter's formation produced increasing amounts of silicate melt for increasing impact velocities above $2\,{\rm km\,s^{-1}}$. We propose that the expanding gas formed from volatile materials by collisional heating dispersed and cooled the silicate melt, resulting in droplet sizes and cooling rates consistent with the observed sizes and inferred cooling rates. We further show that the peak melt production is linked to the onset of Jupiter's runaway gas
accretion, and argue that the peak age of chondrules points to Jupiter's birth dating 1.8 Myr after CAIs.
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Solar and Stellar Astrophysics
Machine Learning Based Identification of Solar Disk and Plages in Kodaikanal Solar Observatory Historical Suncharts
Dibya Kirti Mishra, Subhamoy Chatterjee, Bibhuti Kumar Jha et al. (+6 more)
Kodaikanal
Solar Observatory (KoSO) is one of the oldest
solar observatories, possessing an archive of multi-wavelength
solar observations, including white light, Ca II K, and H-alpha images spanning over a century. In addition to these observations, KoSO has preserved hand-drawn suncharts (1904-2022), on which various
solar features such as sunspots, plages, filaments, and prominences are marked on the Stonyhurst grid with distinct colour coding. In this study, we present the first comprehensive result that includes the entire data set from these suncharts using a supervised Machine Learning model called "Convolutional Neural Networks (CNNs)", firstly to identify the
solar disks from the charts (1909-2007), secondly to identify the plages, spanning 9
solar cycles (1916-2007). We train the CNN with the manually identified
solar disk and plage. We first detect the
solar limb and the North-South line in the suncharts, which enables the extraction of disk centre coordinates, radius, and P-angle. Following that, we use a CNN similar architecture to achieve accurate image
segmentation for the identification of plages. We compare plage areas derived from the suncharts with those obtained from Ca II K full-disk observations, and find good agreement that demonstrates the potential application of such an ML technique for historical data. The results of this study further demonstrate the potential application of sunchart data to fill the existing data gaps in the KoSO multi-wavelength observations and contribute toward constructing a composite series over the last century.
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All authors Dibya Kirti Mishra, Subhamoy Chatterjee, Bibhuti Kumar Jha, Hemapriya Raju, Aditya Priyadarshi, Manjunath Hegde, Srinjana Routh, Dipankar Banerjee, M. Saleem Khan
High Energy Astrophysical Phenomena
Lost and Found - A gallery of overlooked optical nuclear transients from the ZTF archive
E. Quintin, E. Russeil, M. Llamas Lanza et al. (+12 more)
Tidal disruption events (TDEs) correspond to the destruction of a
star by the
tidal forces around a black hole, leading to outbursts which can last from months to years. These transients are rare, and increasing the current sample is paramount to understand them. As part of the Fink alert broker, we have developed an early detection system for TDEs for the Zwicky Transient Facility (ZTF) data. In this paper, we report on the optical transients we found either during the development of this tool, or when applying the classifier to the existing archive. We use this sample to anticipate what improvements to the TDE detection systems will need to be implemented for future surveys. For all the transients, we present optical and infrared archival photometry from ZTF, WISE, and Catalina, and assess the previous
nuclear activity of the host. We fit the ZTF lightcurves with both a phenomenological and a physically-motivated model. We report on a total of 19 optical
nuclear transients, out of which nine are in passive
galaxies, eight in active
galaxies, and two for which the activity of the host is uncertain. Two transients are newly discovered repeated TDE candidates, and we compare them to the current sample of repeated optical
nuclear transients. One transient is exceptionally long-lived (over 5 years), in an until-now passive
galaxy. Three of the TDE-like
flares in active
galaxies have absolute g-band magnitudes brighter than -24, making them new Extreme
Nuclear Transient (ENT) candidates. One seemingly repeated object was revealed to be two independent
supernovae in the same
galaxy. This sample shows both the potential of our detection system for future discovery, and the relevance of archival searches to reveal overlooked transients. It also raises several points of concern and avenues of improvement for current and future classifiers.
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All authors E. Quintin, E. Russeil, M. Llamas Lanza, S. Karpov, E. E. O. Ishida, J. Peloton, M. V. Pruzhinskaya, A. Möller, M. Giustini, G. Miniutti, R.S. Saxton, P. Sánchez-Sáez, S. Zheltoukhov, A. Dodin, A. Belinski
Instrumentation and Methods for Astrophysics
Enhancing Fast Radio Transient Detection with Mask R-CNN Image Segmentation
Sergio Belmonte Diaz, Rene P. Breton, Zafiirah Hosenie et al. (+1 more)
Traditionally, fast
radio transient searches are conducted on dedispersed time series using thresholding techniques based on the statistical properties of the data. However, peaks in dedispersed time series do not directly provide information on the nature of the source. In the DM-time domain, the S/N variation of real, dispersed astrophysical signals forms a characteristic bow tie shape, whereas
radio frequency interference (RFI) can take multiple different forms. We have developed a method that bypasses the thresholding step of traditional single-pulse searches in favour of a direct DM-time domain image analysis. The backbone of our pipeline is a Mask R-CNN, a deep learning model designed for object detection, enabling it to identify the bow tie signature and distinguish real sources from RFI. Previous deep learning models often include a snippet of the DM-time domain in their input. We have trained the model on simulated bursts injected on top of real MeerKAT noise observations. We tested the model on MeerKAT follow-up observations of the repeater FRB20240114A and we were able to recover all bursts with a signal-to-noise above the traditional threshold, while detecting two bursts that were fainter. Our new approach considerably reduces the number of candidates above a nominal threshold while being capable of running in real time for typical surveys. We also propose a modified version of the traditional dedispersion plan optimised for this method.
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All authors Sergio Belmonte Diaz, Rene P. Breton, Zafiirah Hosenie, Ben W. Stappers
Earth and Planetary Astrophysics
Resolving the flat-spectrum conundrum: clumpy aerosol distributions in sub-Neptune atmospheres
James E. Owen and James Kirk
Transmission spectroscopy of sub-Neptunes was expected to reveal their compositions and hence origins, yet many show flat near- to mid-infrared spectra. Such spectra can be explained either by metal dominated atmospheres or by high-altitude, grey aerosols. Observations of escaping hydrogen and helium from several of these
planets rule out metal dominated atmospheres, while homogeneous distributions of small aerosols cannot produce flat spectra and large particles require unphysically high production rates. We investigate the role of heterogeneous, "clumpy" aerosol distributions in shaping transmission spectra. Modestly optically thick clumps at high altitudes can produce flat spectra even with small particles and physically realistic production rates. Clumping increases the effective
photon mean-free path while reducing wavelength dependence, allowing the aerosol distribution to behave as an effective grey absorber. Applying this framework to the sub-Neptune TOI-776c, we show that clumpy aerosols can reconcile the observed flattening of its transmission spectrum with a
primordial H/He-dominated atmosphere. We further discuss implications for emission spectra, where enhanced
stellar radiation penetration and altered scattering in a clumpy medium could produce observable signatures. These results suggest that clumpy aerosol distributions naturally resolve the tension between flat spectra and low-
metallicity atmospheres and may be a common feature of sub-Neptune
exoplanets. More broadly, our results highlight the need to consider aerosol heterogeneity when interpreting high-altitude microphysics and the spectral appearance of
exoplanet atmospheres with JWST, and motivate theoretical work to identify the physical mechanisms capable of generating clumpy aerosol distributions.
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Instrumentation and Methods for Astrophysics · Cross-listed from hep-ex
Enhancing low energy reconstruction and classification in KM3NeT/ORCA with transformers
Iván Mozún Mateo
The current KM3NeT/ORCA
neutrino telescope, still under construction, has not yet reached its full potential in
neutrino reconstruction capability. When training any deep learning model, no explicit information about the physics or the detector is provided, thus they remain unknown to the model. This study leverages the strengths of
transformers by incorporating
attention masks inspired by the physics and detector design, making the model understand both the
telescope design and the
neutrino physics measured on it. The study also shows the efficacy of
transformers on retaining valuable information between detectors when doing fine-tuning from one configurations to another.
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Solar and Stellar Astrophysics
The complex inner disk of the Herbig Ae star HD 100453 with VLTI/MATISSE
L. N. A. van Haastere, J. Varga, M. R. Hogerheijde et al. (+35 more)
The inner regions of
planet-forming disks hold invaluable insights for our understanding of
planet formation. The disk around the Herbig
star HD 100453 presents one such environment, with an inner disk that is significantly misaligned with respect to the outer disk. This paper expands the existing H-band (PIONIER) and K-band (
GRAVITY) interferometric studies of the HD 100453 inner disk to the L-band with the MATISSE VLTI instrument. With snapshot data spanning approximately four years we aim for a more comprehensive understanding of the inner disk structures and their potential time
evolution. Based on the MATISSE data obtained, we use a combination of analytical models and image reconstruction to constrain the disk structure. Additionally, we fit a temperature gradient model to the selected wavelength range of PIONIER,
GRAVITY and MATISSE to derive physical properties of the inner regions. Our parametric model finds an inclination of $\sim 47.5^\circ$ and a position angle of $\sim 83.6^\circ$, which corroborates the case of strong inner-outer disk misalignment. From the symmetric temperature gradient we derive an inner disk radius around $\sim0.27$ au, with
dust surface densities of $\Sigma_{\rm{subl}} \approx 10^{-3.2}$ g/cm$^2$ and vertical optical depth $\tau_{\rm{z, subl}} \approx 0.1-0.06$. Same-night MATISSE and
GRAVITY observations indicate the necessity for higher-order asymmetries to explain the interferometric signals, which is further supported by a MATISSE snapshot image reconstruction. The chromatic interferometric data reveal the likely need for higher-order asymmetries to explain the inner disk of HD~100453, suggesting a possible origin in dynamic interactions or disk instabilities. Coordinated multi-wavelength infrared interferometric observations with
GRAVITY and MATISSE will be crucial to confirm these findings and uncover its underlying nature.
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All authors L. N. A. van Haastere, J. Varga, M. R. Hogerheijde, C. Dominik, M. Scheuck, A. Matter, R. van Boekel, B. Lopez, M. Abello, J.-C. Augereau, P. Boley, W.-C. Danchi, V. Gámez Rosas, Th. Henning, K.-H. Hofmann, M. Houllé, W. Jaffe, J. Kobus, E. Kokoulina, L. H. Leftley, M. Letessier, J. Ma, F. Millour, E. Pantin, P. Priolet, D. Schertl, J. Scigliuto, G. Weigelt, S. Wolf, P. Berio, F. Bettonvil, P. Cruzalèbes, M. Heininger, J.W. Isbell, S. Lagarde, A. Meilland, R. Petrov, S. Robbe-Dubois
High Energy Astrophysical Phenomena
The variability of blazars throughout the electromagnetic spectrum
Claudia M. Raiteri
With their jet pointing towards us, blazars are ideal tools to study the physics and structure of extragalactic jets. Their powerful jets are
cosmic particle accelerators and are alleged to be one of the production sites of the high-energy
neutrinos detected by the IceCube Observatory. Doppler beaming of the jet nonthermal radiation increases blazar brightness, blue-shifts their emission, and shortens their variability time scales, which are observed to range from years down to minutes. This review will focus on blazar flux, spectral, and polarization variability across the electromagnetic spectrum. Interpretation of blazar variability calls into question both intrinsic and extrinsic mechanisms. Shock waves,
magnetic reconnection, and
turbulence can accelerate particles inside the jet, while jet precession, rotation, and twisting can produce variations in Doppler beaming. Microvariability puts strong constraints on the size of the emitting regions, suggesting a multizone emitting jet. Twisting jets have been proposed to explain the long-term multiwavelength variability. They are supported by
radio observations of bent or helical jets, and by results of relativistic magnetohydrodynamics simulations of
plasma jets. Detection of (quasi)periodic behaviour has been ascribed to orbital motion in black hole binary systems, jet precession, kink instabilities developing inside the jet, or perturbations in the
accretion disc. Gravitational microlensing has been suggested to explain blazar behaviour in some cases. Polarization provides information on the structure and behaviour of the
magnetic field in the emission zones. Both the degree and angle of polarization can show strong and fast variability, which is sometimes correlated with flux. The interpretation of flux, spectral, and polarization variability within a consistent picture challenges current models of blazar variability.
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Earth and Planetary Astrophysics
On the weak synchronization of a nonlinear solar dynamo oscillator by coherent planetary timing
Jean-Louis Le Mouël, Vincent Courtillot, Vladimir Kossobokov et al. (+4 more)
The
solar cycle is commonly interpreted as an internally generated
magnetic oscillation, yet its phase stability and long-term amplitude modulation remain difficult to explain through autonomous dynamo physics alone. We test the narrower hypothesis that the
solar dynamo behaves as a self-excited nonlinear oscillator whose phase and envelope may be weakly modulated by coherent astronomical timing. Using historical sunspot numbers, terrestrial length-of-day records, and ephemeris-based planetary descriptors, we identify shared long-period pseudo-cycles across
solar, geophysical, and astronomical observables. Singular Spectrum Analysis is used only as a non-parametric decomposition method. We then drive a reduced nonlinear $\alpha$–$\Omega$ oscillator with prescribed planetary timing signals.
Solar barycentric angular momentum is treated as a mechanically defined ephemeris descriptor, whereas summed planetary right ascension is retained solely as an empirical geometrical phase proxy. We also introduce the physical planetary quadrupolar
tidal tensor and use its equatorial off-diagonal component, $2T_{xy}$, as an independent timing descriptor. Forcing by normalized $2T_{xy}$ yields synchronization comparable to, and slightly better than, right ascension: $r=0.660$ and $\mathrm{RMSE}*{z}=0.824$, versus $r=0.655$ and $\mathrm{RMSE}*{z}=0.831$. Planetary forcing is not proposed to power or replace the internal dynamo, but only to provide weak timing. A possible relay involves planetary tides, tachocline magneto-Rossby dynamics, and nonlinear dynamo response. These results do not establish a complete coupling mechanism, but support the possibility that the
solar cycle is susceptible to weak astronomical synchronization.
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All authors Jean-Louis Le Mouël, Vincent Courtillot, Vladimir Kossobokov, Dominique Gibert, Fernando Lopes, Jean-Baptiste Boulé, Pierpaolo Zuddas
Cosmology and Nongalactic Astrophysics
Improved constraints on ultralight axions using latest observations of the early and late Universe
Qianshuo Liu, Chang Feng and Filipe B. Abdalla
Ultralight
axions (ULAs) are hypothetical particles which can behave like dark matter (DM) or dark energy (DE) depending on masses generated at the
symmetry-breaking scale. It remains a mystery whether the ULAs can make up a fraction of DM or DE. Although theoretical predictions indicate that the ULAs may leave distinct imprints on cosmological signals, these signatures may exist in a broad spatial and temporal scales, and may be degenerate with the known effects of the standard model. The ULA signatures are extremely subtle and the observational evidence of the ULAs remain elusive. In this work, we infer the ULA properties using both the early and late universe observations from the
cosmic microwave background (CMB) and
baryon acoustic oscillations (BAO). We validate modeling of the ULA effects using the CMB and BAO mock data and perform different tests to cross-check the results. By analyzing the Planck 2018 CMB measurements and the BAO measurements from the Data Release 2 of Dark Energy Spectroscopic Instrument (DESI), we constrain the energy density fraction ratio of the ULAs to total dark matter $\Omega_a/\Omega_d$ and obtain a new upper bound of $\Omega_a/\Omega_d$. Future CMB and BAO measurements will achieve unprecedented precision and will be crucial for understanding the nature of the ULAs.
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Solar and Stellar Astrophysics
STORMY : A Real-time Triggering Framework using Yamagawa Solar Spectrograph for Active Solar Emission Observations with the MWA
Deepan Patra, Devojyoti Kansabanik, Divya Oberoi et al. (+5 more)
Some of the most interesting insights into
solar physics and space weather come from studying
radio emissions associated with
solar activity, which remain inherently unpredictable. Hence, a real-time triggering system is needed for
solar observations with the versatile new-generation
radio telescopes to efficiently capture these episodes of
solar activity with the precious and limited
solar observing time. We have developed such a system,
Solar Triggered Observations of
Radio bursts using MWA and Yamagawa (STROMY) for the Murchison Widefield Array (MWA), the precursor for the low frequency
telescope of upcoming Square Kilometre Array Observatory (SKAO). It is based on near-real-time data from the Yamagawa
solar spectrograph, located at a similar longitude to the MWA. We have devised, implemented, and tested
algorithms to perform an effective denoising of the data to identify signatures of
solar activity in the Yamagawa data in near real-time. End-to-end tests of triggered observations have been successfully carried out at the MWA. STORMY is operational at the MWA for the routine
solar observations, a timely development in the view of the ongoing
solar maximum. We present this new observing framework and discuss how it can enable efficient capturing of event-rich
solar data with existing instruments, like the LOw Frequency ARray (LOFAR), Owens Valley
Radio Observatory - Long Wavelength Array (OVRO-LWA) etc., and pave the way for triggered observing with the SKAO, especially the SKA-Low.
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All authors Deepan Patra, Devojyoti Kansabanik, Divya Oberoi, Yûki Kubo, Bradley W. Meyers, Andrew Williams, Soham Dey, Naoto Nishizuka
Solar and Stellar Astrophysics
BSN-V: The First Detailed Light Curve Modeling of Eight Totally Eclipsing Contact Binary Stars Using Ground-Based and TESS Observations
Atila Poro, Raul Michel, Francisco Javier Tamayo et al. (+3 more)
This study broadens our comprehensive investigation of total-eclipse W Ursae Majoris-type contact binaries by analyzing eight additional systems, continuing our previous research. Multiband $BVR_cI_c$ photometric data were obtained at an observatory in Mexico, from which new times of minima were determined. All target systems also had available space-based TESS time-series data. Orbital period variations were studied for eight target systems, showing either linear or
parabolic trends. The target systems exhibiting
parabolic trends demonstrated a sustained decrease in their orbital periods over time. We modeled the light curves utilizing the PHOEBE Python code in combination with the BSN application. We revisited the relationship between orbital period and the temperature of the hotter component in contact binary systems using an empirical approach. Our analysis identified a clear break at P=0.27 days, separating the systems into two distinct groups for orbital periods shorter than 0.6 days. Following the determination of
stellar extinction, absolute parameters for seven systems were estimated employing parallax measurements from
Gaia DR3. Based on the components' effective temperatures and masses, the systems were classified into A- and W-subtypes. Their evolutionary states were illustrated using mass-radius and mass-luminosity diagrams.
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All authors Atila Poro, Raul Michel, Francisco Javier Tamayo, Mahya Hedayatjoo, Hector Aceves, Fahri Alicavus
Astrophysics of Galaxies
The dawn is quiet II: Gaia XP constraints on the Milky Way's proto-Galaxy from very metal-poor MDF tails
Boquan Chen, Matthew D. A. Orkney, Yuan-Sen Ting et al. (+1 more)
The earliest phase of the Milky Way's
evolution involved a transition from a dispersion-supported proto-
galaxy to a rotationally supported disk. A key chemical signature of this transition is the moderate rise in [$\alpha$/Fe] near $\mathrm{[Fe/H]}\approx-1.3$, which we previously interpreted as evidence for $\alpha$-enhanced gas
accretion fueling early disk formation. However, this trend alone does not uniquely constrain the trade-off between initial gas mass, inflow rate, and
star formation efficiency (SFE), leaving the physical condition of the proto-Milky Way uncertain. To break this degeneracy, we analyze the metal-poor tail ($-3<\mathrm{[Fe/H]}<-2$) of the Milky Way's
metallicity distribution function (MDF) using
Gaia DR3 BP/RP (XP)
metallicities from ten catalogs. After applying recommended quality cuts, all catalogs exhibit a single-slope exponential tail with slopes $k\simeq0.6$–$2.0$. Comparison with one-zone
galactic chemical-
evolution (GCE) models that replicated the [$\alpha$/Fe]-rise from Paper I shows that shallow tails ($k\simeq0.6$) require a massive initial cold gas reservoir ($\gtrsim10^9\, \mathrm{M_\odot}$), while steeper tails ($k\gtrsim1$) arise from small reservoirs that built up over time with weak inflow. MDFs with $k \simeq 1.0$ are best reproduced under our GCE framework, which favor a proto-
Galaxy with a moderate gas reservoir ($10^{8}$–$10^{9}\, \mathrm{M_\odot}$) sustained through weak continuous inflow ($\sim 2 \ \mathrm{M_\odot \ yr^{-1}}$) and SFE comparable to today's value (a few $\times 10^{-10}\,\mathrm{yr^{-1}}$) during the first Gyr. This scenario is reinforced by MDFs of 30 Milky Way analogs in the Auriga simulations, which exhibit similar slopes ($k\approx1.25$). The metal-poor MDF tail thus provides a quantitative constraint on the Milky Way's early gas
accretion and
star formation history.
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All authors Boquan Chen, Matthew D. A. Orkney, Yuan-Sen Ting, Michael R. Hayden
High Energy Astrophysical Phenomena
Measurement of Milli-Charged Particles with a running electromagnetic coupling constant at IceCube
Ye Xu
It is postulated that heavy dark matter $\phi$ with a mass on the order of TeV, once captured by the Earth, can decay into relativistic milli-charged particles (MCPs). These MCPs are potentially detectable at the IceCube
neutrino telescope. In this study, MCPs are modeled within the massless hidden
photon framework, where they interact with
nuclei via a running electromagnetic coupling constant, thereby enabling the prediction of their expected event rates and fluxes at IceCube. The expected number of background
neutrino events at IceCube has also been evaluated. Under the assumption that no signal events are observed over a 10-year period at IceCube, upper limits on the MCP flux have been derived at the 90% confidence level. The results suggest that MCPs originating from the Earth's core could be directly detected at IceCube at energies around $\mathcal{O}(1\ \text{TeV})$ for a fractional charge-squared range of $5.65\times10^{-5} \lesssim \epsilon^2 \lesssim 1.295\times10^{-3}$. Furthermore, with 10 years of IceCube data, a new region in the $m_{\text{MCP}}$-$\epsilon$ parameter space–specifically, $4\ \text{GeV} < m_{\text{MCP}} < 100\ \text{GeV}$ and $5.51\times10^{-2} < \epsilon < 0.612$–has been excluded.
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Instrumentation and Methods for Astrophysics
TDLight: A Framework for Incremental Light-Curve Management and Continuous Classification Optimization
Xinghang Yu, Ce Yu, Zeguang Shao et al. (+2 more)
Time-series observations of celestial objects are fundamental to studying variable and transient phenomena. As time-domain surveys continue to scale up, timely automated classification is essential for rapid follow-up. Many existing approaches treat storage and analysis as separate stages, archiving data first and analyzing it later. Yet each source is a continuously growing stream, and early observations often contain sufficient information to assign scientifically useful labels before the full light curve is available. Motivated by this, we present TDLight, a framework for light-curve management and trigger-based classification over incremental data streams. Built on the time-series database TDengine, the system loads the
Gaia DR2 archive (approximately 4.8 x 10^7 rows) in 33 s and supports low-latency
retrieval. As new observations accumulate, TDLight automatically triggers a lightweight LightGBM-based classification pipeline that requires no GPU. When prediction confidence exceeds a predefined threshold, these early results are written back to the database, providing reliable classifications before offline analysis is complete. The deployed system also supports manual label confirmation and optional incremental training. Evaluated on the LEAVES
dataset (approximately 1.10 million sources spanning 10 classes), the system achieves an overall accuracy of 93.6% and a weighted F1 score of 93.7%. Furthermore, it identifies 560 high-confidence catalog-disagreement candidates for follow-up verification. Notably, this includes correcting 150 RRc variables erroneously labeled as EW binaries due to inherited period-doubling artifacts. TDLight and the related data products are publicly available.
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All authors Xinghang Yu, Ce Yu, Zeguang Shao, Chen Wang, Bin Yang
Earth and Planetary Astrophysics
Jun Kimura
In the outer
solar system beyond Jupiter, water ice is a dominant component of planetary bodies, and most solid objects in this region are classified as icy bodies. Icy bodies display a remarkable diversity of geological, geophysical, and atmospheric processes, which differ fundamentally from those of the rocky terrestrial
planets. Evidence from past and ongoing spacecraft missions has revealed subsurface oceans, cryovolcanic activity, and tenuous but persistent atmospheres, showing that icy bodies are active and evolving worlds. At the same time, major questions remain unresolved, including the chemical properties of icy materials, the geological histories of their surfaces, and the coupling between internal
evolution and orbital dynamics. Current knowledge of the surfaces, interiors, and atmospheres of the principal icy bodies is built on spacecraft measurements, telescopic observations, laboratory experiments, and theoretical modeling. Recent contributions from Juno, JWST, and
stellar occultation studies have added valuable constraints on atmospheric composition, interior structure, and surface activity. Looking ahead, missions such as JUICE, Europa Clipper, Dragonfly, and the Uranus Orbiter and Probe are expected to deliver substantial progress in the study of icy bodies. Their findings, combined with continued Earth- and space-based observations and laboratory studies, will be critical for assessing the potential habitability of these environments and for placing them within a broader framework of planetary system formation and
evolution.
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Solar and Stellar Astrophysics
Numerical Non-Adiabatic Tidal Calculations with GYRE-tides: The WASP-12 Test Case
Meng Sun, Richard H. D. Townsend, Hongbo Xia et al. (+1 more)
We revisit the
tidal evolution of the WASP-12 system using direct numerical calculations with the GYRE-tides code. WASP-12b is a hot Jupiter on a 1.1-day orbit around a slightly evolved F-type
star. Its observed orbital decay rate, $|\dot{P}_{\rm orb}/P_{\rm orb}| \approx 3.2\,\mathrm{Myr}^{-1}$, provides a strong constraint on
stellar tidal dissipation. We confirm that linear tides with radiative damping and convective damping, as currently implemented, are not sufficient to reproduce the observed inspiral timescale. Nevertheless, our calculations, based on fully non-adiabatic forced oscillations in MESA
stellar models with convective envelopes, yield dissipation rates that are consistent with previous semi-analytic and adiabatic estimates, confirming the robustness of our numerical framework. As the only open-source, actively maintained tool capable of computing orbital
evolution in
exoplanet systems, GYRE-tides provides a
benchmark calculation for WASP-12 and future applications. Our results validate GYRE-tides as a tool for analyzing combined radiative and convective damping, and indicate that the observed decay rate requires
tidal dissipation operating in or near the fully damped regime, which may be achieved through nonlinear damping. These contributions could also be evaluated by computing the wave luminosity at the radiative-convective boundary using our tool. GYRE-tides offers an open-source framework for computing
tidal dissipation in short-period
exoplanet systems, including the many systems expected to show orbital decay in upcoming Roman surveys.
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All authors Meng Sun, Richard H. D. Townsend, Hongbo Xia, Jifeng Liu
Earth and Planetary Astrophysics
The Dynamical Interaction between Low-mass Planets and Dust Coagulation
Qiang Hou, Cong Yu and Shu-ichiro Inutsuka
We investigate the impact of a low-mass
planet on
dust coagulation, and its consequent feedback on planetary migration, using a linear analysis of the coupled
dust-gas hydrodynamic equations.
Dust coagulation is incorporated via a single-size approximation. In the co-orbital region of the
planet, we find that the growth of
dust size is significantly suppressed by
planet-induced coagulation modes (CMs). This effect are less pronounced with smaller stopping times, stronger gaseous
turbulence or imperfect sticking. Regarding planetary migration, we find that CMs make outward migration require $\tau \gtrsim 0.3$ ($\tau$ is dimensionless stopping time) with typical turbulent strength and
dust coagulation efficiency. We demonstrate that the torque variations are reasonable and arise from phase shifts between the density and stopping time perturbations in the coagulation modes.
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Earth and Planetary Astrophysics
A Smooth Transition from Giant Planets to Brown Dwarfs from the Radial Occurrence Distribution
Judah Van Zandt, Greg Gilbert, Steven Giacalone et al. (+3 more)
Measuring the occurrence rates of celestial objects is a valuable way to study their origins and
evolution.
Giant planets and brown
dwarfs produce large Doppler signatures that are easily detectable by modern instrumentation, and legacy radial velocity (RV) surveys have now achieved full orbital coverage for periods <~30 years. However, the Doppler method's sensitivity to companion minimum mass M_c sin i – as opposed to true mass M_c – prevents unambiguous characterization using RVs alone, as purported
giant planets may be brown
dwarfs or
stars on inclined orbits. Here we combined legacy RVs with absolute astrometry to re-fit the orbits of 194 companions from the California Legacy Survey. Around 40% (7/18) of the "brown
dwarfs" (M_c sin i = 13-80 M_Jup) we refit had true masses above 80 M_Jup. We incorporated our orbital posteriors and target sensitivity maps into a Poisson likelihood model to calculate occurrence as a function of true companion mass M_c (0.8-80 M_Jup) and separation a (0.3-30 AU). The semi-major axis distributions of objects in this range vary smoothly with mass, with Jupiter analogs favoring an abrupt increase in occurrence near 1 AU and brown
dwarfs exhibiting a gradual enhancement at wider separations. Marginalized companion occurrence between 1-10 AU decreases smoothly with mass, with brown
dwarfs having the lowest occurrence rate: 1.1 (+0.5, -0.4)%. Jupiter analogs are 10 times as common as brown
dwarfs per mass interval in this range, demonstrating that the brown
dwarf desert extends to 10 AU. The smooth variation in these distributions disfavors a sharp transition mass between "bottom-up" core
accretion and "top-down" gravitational instability formation mechanisms, and rather suggests that these processes may produce companions in overlapping mass ranges.
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All authors Judah Van Zandt, Greg Gilbert, Steven Giacalone, Erik Petigura, Andrew Howard, Luke Handley
High Energy Astrophysical Phenomena
Hierarchical Bayesian estimation of population-level torque law parameters from $68$ young radio pulsars observed with the Murriyang telescope
Andrés F. Vargas, Andrew Melatos, Julian B. Carlin et al. (+3 more)
Abridged. The measured braking index, $n=\nu \ddot{\nu}/\dot{\nu}^2$, of a rotation-powered
pulsar with
spin frequency $\nu$ and braking torque $K \nu^{n_{\rm pl}}$, features secular and
stochastic anomalies arising from $\dot{K} \neq 0$ and random torque noise respectively. Previous studies quantified the variance $\langle n^{2} \rangle = (n_{\rm pl}+\dot{K}_{\rm dim})^{2}+\sigma_{\rm dim}^{2}$, where the secular anomaly, $\dot{K}_{\rm dim}$, is inversely proportional to the characteristic time-scale $\tau_{K}$ over which $K$ varies; the
stochastic anomaly, $\sigma_{\rm dim}^{2} = \sigma_{\ddot{\nu}}^{2}\nu^{2}\gamma_{\ddot{\nu}}^{-2}\dot{\nu}^{-4}T_{\rm obs}^{-1}$, is a function of the timing noise amplitude $\sigma_{\ddot{\nu}}$, a damping time-scale $\gamma_{\ddot{\nu}}^{-1}$ and the total observing time $T_{\rm obs}$; and the average is taken over an ensemble of random realizations of the noise process. Here, we use a hierarchical
Bayesian scheme, based on the formula for $\langle n^{2} \rangle$, to infer the population-level distribution of $n_{\rm pl}+\dot{K}_{\rm dim}$ for a sample of $68$ young
radio pulsars, observed for $\gtrsim 10~{\rm years}$ with Murriyang, the 64-m Parkes
radio telescope. Upon assuming that the $n_{\rm pl}+\dot{K}_{\rm dim}$ values are drawn from a population-level Gaussian, $N(\mu_{\rm pl}, \sigma_{\rm pl})$, the
Bayesian scheme returns the mean $\mu_{\rm pl} = 9.95^{+5.58}_{-5.26}$ and standard deviation $\sigma_{\rm pl}=10.89^{+5.14}_{-3.69}$. At a per-
pulsar level it returns posterior medians satisfying $-13.86 \leq n_{\rm pl}+\dot{K}_{\rm dim} \leq 30.38$. The secular anomaly dominates the
stochastic anomaly, with posterior medians satisfying $|n_{\rm pl} + \dot{K}_{\rm dim}| \geq \sigma_{\rm dim}$ in 10 out of 68 objects.
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All authors Andrés F. Vargas, Andrew Melatos, Julian B. Carlin, Marcus E. Lower, Simon Johnston, Patrick Weltevrede
High Energy Astrophysical Phenomena
Tracing the Trace Anomaly of Dense Matter inside Neutron Stars
Shiyue Ren and Lap-Ming Lin
The trace anomaly $\Delta$ is an important quantity that measures the broken conformal
symmetry in
neutron star matter. In this work, we present quasi-universal relations that connect the
stellar profile of $\Delta$ to the compactness, moment of inertia, and
tidal deformability of
neutron stars. We apply the quasi-universal relations to determine the trace anomaly profiles for PSR J0030+0451 and PSR J0740+6620 based on their mass-radius measurements. We also analyze PSR J0737-3039A according to its moment of inertia inferred from
Bayesian modeling of
nuclear equation of state. A recent multimessenger constraint on the
tidal deformability is also studied, resulting in an estimate value of the trace anomaly $\Delta_c = 0.1770^{+0.0365}_{-0.0432}$ at the center of a $1.4M_\odot$ canonical
neutron star. It is expected that more precise observations from both electromagnetic and gravitational-wave channels in the future will provide tighter constraints on the behavior of $\Delta$ inside
neutron stars.
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High Energy Astrophysical Phenomena
Fast Radio Bursts from White Dwarf Binary Mergers: Isolated and Triple-Induced Channels
Cheyanne Shariat, Claire S. Ye, Smadar Naoz et al. (+1 more)
The detection of fast
radio bursts (FRBs) in both young and old
stellar populations suggests multiple formation pathways, beyond just young magnetars from core-collapse
supernovae. A promising delayed channel involves the formation of FRB-emitting
neutron stars through merger- or
accretion-induced collapse of a massive white
dwarf (WD). By simulating a realistic
stellar population with both binaries and triples, we identify pathways to WD collapse that could produce FRB candidates. We find that (i) triple dynamics open new merger channels inaccessible to isolated binaries, significantly enhancing the overall merger rate; (ii) triple-induced mergers broaden the delay-time distribution, producing long-delay ($\gtrsim1$-8~Gyr) events largely independent of
metallicity, alongside a shorter-delay population ($\lesssim100$~Myr) of rapid mergers; (iii) these long delays naturally yield FRBs in older environments such as quiescent host
galaxies and
galactic halos; (iv) when convolved with the
cosmic star-formation history, binary channels track the
star-formation rate ($z_{\rm peak} \sim 2$), while triple channels peak later ($z_{\rm peak} \sim 1$), giving a combined local source rate of $R_0 \approx 2\times10^4~{\rm Gpc^{-3}~yr^{-1}}$, consistent with observations; and (v) applying the same framework to Type~Ia
supernovae, we find that triples extend the delay-time tail and roughly double the Ia efficiency relative to binaries, yielding rates and
redshift evolution in good agreement with observations. If FRBs originate from the collapse of WDs, our results establish triples, alongside binaries, as a crucial and previously overlooked formation pathway whose predicted rates, host demographics, and
redshift evolution offer clear tests for upcoming surveys.
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All authors Cheyanne Shariat, Claire S. Ye, Smadar Naoz, Sanaea Rose