Earth and Planetary Astrophysics
How long can you trust a Starlink TLE? An empirical comparison of SGP4 and high-fidelity propagation against operator-updated truth across a megaconstellation
Dimitrije Jankovic
We characterise position-error behaviour of Two-Line Element (TLE) propagation against operator-updated truth on Starlink, sweeping 24,641 next-TLE-truth pairs across 501 satellites stratified by altitude shell (540, 550, 560 km) and platform generation (v1.0, v1.5, v2-mini) over April 2026. Each pair is propagated with SGP4 and GMAT at high fidelity (EGM2008 $70\times70$, NRLMSISE-00 drag, Sun and Moon third-body
gravity, conical-shadow SRP), then compared against the operator's next TLE as proxy truth. Three findings: First, position error follows a per-
cell power law $\lVert\Delta\mathbf{r}(\Delta t)\rVert \approx A\,\Delta t^{k}$ with fitted exponents in $(1,2)$ on every v2-mini
cell and on the high-fidelity v1.x
cells at 540 and 560 km, while SGP4 v1.x and high-fidelity v1.x at 550 km are sub-linear ($k \lesssim 1$); the cohort-specific mix of mean-motion bias and unmodelled in-track acceleration sets the per-
cell exponent. Pooled $L_{2}$ medians grow from $\sim 1$ km at 6 h to $\sim 38$ km (SGP4) / $\sim 76$ km (high-fid) at 7 d. Second, high-fidelity propagation from public-TLE inputs does not improve over SGP4 at any of the four staleness horizons; SGP4 wins on $\sim 65$–$75\%$ of pairs, with v2-mini at long $\Delta t$ the one regime where high-fidelity wins on a majority of pairs at both populated shells. The negative result reflects operator-OD residual dominance at epoch, SGP4-vs-SGP4 truth-construction kernel
alignment, and spacecraft-property bias amplification on the high-fidelity arm. Third, the per-satellite SGP4 staleness coefficient regressed against F10.7 returns a positive slope clearing conventional significance at one shell (560 km) on the 30-day, $\sim 17$ sfu window – direction-consistent with the LEO density-gradient expectation, not a calibrated F10.7-modulation measurement.
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Cosmology and Nongalactic Astrophysics
Domain-wall Quintessence
Nobufusa Kobayashi, Yuichiro Tada, Fuminobu Takahashi et al. (+1 more)
We investigate a dark energy model driven by a planar domain-wall-like structure with a thickness comparable to, or larger than, the current Hubble radius, focusing on its intrinsic anisotropy and observational viability. Near the centre of the domain wall (DW), the spacetime is anisotropic, with distinct expansion rates parallel and perpendicular to the wall. This anisotropic structure induces direction-dependent
cosmic expansion and modifies
photon geodesics from cosmological sources, leaving characteristic signatures in cosmological observables. We confront the model with recent observational data. We first compute the anisotropic
Cosmic Microwave Background (CMB) temperature multipoles generated by the DW and impose constraints from the Planck 2018 measurements. These constraints severely limit the allowed DW abundance, requiring the DW energy density to be less than $\mathcal{O}(10^{-5})$ of the current critical density in order to suppress the quadrupole contributions. We then perform a Markov Chain Monte Carlo (MCMC) analysis using Type Ia
supernova (SNe Ia) data, including the Pantheon+ SH0ES and DESY5 samples, to compare the DW scenario with the standard $\Lambda$CDM model. We find that although the DW naturally realises anisotropic accelerated expansion, the combined constraints from the CMB and SNe Ia favour the $\Lambda$CDM limit, in which the DW contribution is negligible, and the universe is effectively isotropic. Our results demonstrate that a Hubble-scale domain wall is tightly constrained by current observations and can only play a subdominant role in the late-time
cosmic acceleration.
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All authors Nobufusa Kobayashi, Yuichiro Tada, Fuminobu Takahashi, Takahiro Terada
Cosmology and Nongalactic Astrophysics
Inflaton accretion onto primordial black holes during reheating
Jitumani Kalita and Debaprasad Maity
Primordial Black Holes (PBHs) forming prior to Big Bang Nucleosynthesis evolve during the reheating epoch, an environment dominated by an oscillating inflaton field decaying into a relativistic thermal bath. In this work, we track the complete lifecycle of PBHs within this coupled inflaton-radiation background. Utilizing $\alpha$-attractor E-models, we analytically anchor the reheating initial conditions directly to
Cosmic Microwave Background observations. By matching exact scalar field solutions in a Schwarzschild spacetime to the cosmological far-zone, we derive the cycle-averaged mass
accretion rate and couple it to the growing radiation bath. We find that this combined
accretion induces a highly non-linear enhancement of the final PBH mass. Because the Hawking evaporation timescale scales cubically with mass, PBHs forming near their critical runaway limits experience a massive extension of their lifespans. Surviving deeper into the radiation-dominated era triggers a multi-order-of-magnitude amplification in their emitted
Stochastic Gravitational Wave Background (SGWB).
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Cosmology and Nongalactic Astrophysics
CMB lensing imprints of cosmic voids in DESI Legacy Survey DR9 LRGs with photometric redshift calibration
Simone Sartori
The
lensing imprint of
cosmic voids in the
Cosmic Microwave Background (CMB) provides a powerful test of the $\Lambda$CDM model. However, recent studies report a "
lensing-is-low" tension between observations and mock predictions. To investigate this, we measure the stacked CMB
lensing signal of 3D
cosmic voids identified in the DESI Legacy Survey DR9 Luminous Red
Galaxy (LRG) sample, cross-correlated with the Planck 2018
lensing map. We compare our observations to $\Lambda$CDM templates derived from Buzzard mocks, critically calibrated using over one million DESI spectra to perfectly match the sparseness and photometric
redshift error distributions of the observed data. By categorizing voids based on their gravitational potential, we disentangle the signals of void-in-voids and void-in-clouds, achieving two independent record detection significances of $\sim 17\sigma$. We find full agreement between observations and simulated $\Lambda$CDM templates across all void populations and
redshift bins ($0.35\! <\! z\! <\! 0.95$), measuring an amplitude parameter $A_\kappa = 1.016 \pm 0.054$ for the full sample. This highlights the necessity of accurate systematic control, effectively resolving the reported
lensing tension within this
dataset. This proceeding summarizes the results presented in Sartori et al. (2025).
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High Energy Astrophysical Phenomena
Magnetized neutron stars: perturbative versus fully-numerical approaches
Debarati Chatterjee, Daw Guttmann, Jérôme Novak et al. (+2 more)
(1) Background: for the study of highly magnetized
neutron stars observed as magnetars, and to quantify the effect of this intense
magnetic field onto the
star's structure and shape which can be particularly relevant for the study of emission of continuous gravitational waves, both numerical and perturbative approaches have been developed. (2) Methods: we compare these two approaches in General Relativity with the limitation to the case where the
magnetic field has a purely poloidal structure. The perturbative one (Konno-99) assumes that the deformation induced by the
magnetic field is small and that this field arises only from dipole currents. The full numerical one is based on the library LORENE. (3) Results: we have used both approaches to compute the
magnetic field distribution and the deformation of the
star, varying the value of the
magnetic field at the pole, the compactness of the
star and its equation of state. (4) Conclusions: whereas the perturbative approach breaks down for very high polar
magnetic field values (typically above a few times $10^{16}$ G), it gives very good results for observed values, even in magnetars. On the contrary, the numerical code exhibits resolution problems for relatively low
magnetic field values (typically $10^{10}$ G), which translates into imprecise computation of the
star's deformation and mass quadrupole moment.
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All authors Debarati Chatterjee, Daw Guttmann, Jérôme Novak, Micaela Oertel, Martin Jakob Steil
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Neutron stars more compact than black holes in quasi-topological gravity: Equilibrium configurations and radial stability
Liang Liang, Zhe Luo, Shoulong Li et al. (+1 more)
Within general relativity, black holes are widely regarded as the ultimate
benchmark for compactness in the Universe. Recently, however,
neutron star models have been constructed in a higher-
curvature theory – quasi-topological
gravity (QTG) – whose compactness can exceed the black-hole limit~ [S. Li, H. Lü, Y. Gao, R. Xu, L. Shao, and H. Yu, companion Letter,
Neutron stars more compact than black holes as a probe of strong-field
gravity, Phys. Rev. D 114, L021504 (2026).]. Here we present a detailed analysis of both the
equilibrium structure and radial stability of such configurations in QTG. By examining several representative equations of state and different values of the gravitational coupling constant, we find that in the high-central-density regime the compactness exceeding the black-hole bound exhibits a universal behavior in QTG. We further show that QTG corrections grow increasingly significant at large central densities and can stabilize configurations that are radially unstable in general relativity over a broad parameter range. These results establish ultra-compact
neutron stars in QTG as theoretically viable strong-field configurations and provide a foundation for further investigations of their dynamical and phenomenological implications.
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All authors Liang Liang, Zhe Luo, Shoulong Li, Hongwei Yu
Solar and Stellar Astrophysics
A Parameterized YSO Accretion Disk Model with Increasing Accretion Rate: Predicted Outburst Lightcurves
Gautam Das, Lynne A. Hillenbrand and Adolfo S. Carvalho
A sub-class among Young
Stellar Objects (YSOs), known as FU Ori type
stars, undergo sudden rises in luminosity by several orders of magnitude on timescales of a few months to a few years, and decay back to quiescence on timescales of a few decades. Modelling the light curves of these objects is crucial to understanding how different components of these
accretion disk systems evolve during outburst. For this purpose, we use a parametric model that couples the
stellar photospheric emission, magnetospheric
accretion shocks, an irradiated
dust disk, and a viscously heated gas disk. We adopt time-dependent
accretion rate profiles that mimic the observed morphologies of FU Ori outburst light curves, and we use the
accretion model infrastructure to simulate multi-band light curves, as well as color curves. The model enables us to study how different components dominate the flux in each band over the course of an outburst, providing insight into
star-magnetosphere-disk interactions throughout the outburst cycle. We find that throughout an
accretion outburst, red optical and near-infrared lightcurves generally follow the same or very similar form as the input
accretion profile, being sensitive to heating in the
accretion shocks and inner gas disk, while mid-infrared lightcurves are more responsive to the location and heating of the innermost
dust disk.
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Solar and Stellar Astrophysics
The Small Phased Array DEmonstrator (SPADE) – Description and first results
Christophe Marqué, Antonio Martínez Picar, Jasmina Magdalenić et al. (+1 more)
We present the Small Phased Array DEmonstrator (SPADE), a compact phased array spectrograph designed for the monitoring of
solar activity in the decameter range, where a majority of bursts of interest for
solar physics and space weather occur. Unlike other existing phased arrays, SPADE operations like Sun tracking and spectra productions are made entirely digitally, and rely on the use of open source library software and commercial generic software defined
radio receivers. In this paper, we describe the instrument and its associated software and present the first observations of the Sun and of the jovian magnetosphere performed between September and December 2024. For the
solar observations, in particular, we highlight the capacities of the instrument in terms of temporal and frequency resolution, making it capable of addressing science topics like
turbulence in the coronal medium and propagation effects affecting
radio waves, which are currently only accessible by larger but non-
solar dedicated phased arrays.
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All authors Christophe Marqué, Antonio Martínez Picar, Jasmina Magdalenić, Elisa Tassan-Din
Solar and Stellar Astrophysics
Solar Atmospheric Abundances in Space & Time
Stephanie L. Yardley
Elemental abundances provide a powerful diagnostic of the physical mechanisms and processes that heat the
solar atmosphere and drive the
solar wind. The First Ionisation Potential (FIP) effect and its inverse (IFIP) are observed both on the Sun and other
stars however, the underlying fractionation mechanisms, their dependence on the
magnetic field
topology, and the role of wave dynamics and
turbulence in the chromosphere are not entirely understood. To address these challenges, a focused team, including observers, theorists, modellers and instrument scientists, spanning a range of career stages and institutions, came together for the Royal Society Theo Murphy meeting “
Solar Atmospheric Abundances in Space and Time". As a result of this meeting, the team worked in collaboration to produce 16 publications for this Special Issue. These publications are introduced here, including a discussion of the open questions and future directions in the context of advances in numerical modelling and current and upcoming
solar and
stellar missions. This article is part of the Royal Society Theo Murphy Meeting Special Issue “
Solar Atmospheric Abundances in Space and Time”.
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Astrophysics of Galaxies
COSMOS-Web: Star formation along the early Hubble sequence and the evolution of dust over the redshift range 0<z<12
Stephen Eales, Matthew Smith, Tom Bakx et al. (+3 more)
We have carried out a stacking analysis with the COSMOS-Web catalogue on one of the deepest ever SCUBA-2 images at 850 microns, allowing us to estimate the mean submillimetre flux density for samples of
galaxies split by
stellar mass and morphological class over the
redshift range 0<z<12. For all morphological classes, the mean
star-formation rate estimated from the
dust emission increases with
redshift, reaching a value for the most massive
galaxies (~10^11 soar masses) of >~80
solar masses per year at 2 < z < 4.5. In this
redshift range, the mean
star-formation rate for these
galaxies falls along the Hubble sequence from ~280
solar masses per year for irregular
galaxies at one end to ~80
solar masses per year for spheroids at the other end, which shows that quenching was already happening shortly after the emergence of the Hubble sequence. The decrease in the
star-formation rate for the spheroidal
galaxies can be reproduced with a `starvation' quenching model with a depletion time of ~10^{8.2} years. We also show that the transformation of `submillimetre
galaxies' can reproduce the growth in number-density of massive bulge-dominated and spheroidal
galaxies over the
redshift range 1.5 <z < 4. As a side-project, we have used our stacking results to show that the ratio of
dust mass to
stellar mass in
galaxies increases with
redshift out to z~8 and to determine the relationship between the mean density of
dust and
redshift in the range 0 < z <12. We show that a chemical
evolution model based on the `
star-formation history' of the universe, with a gas
outflow rate equal to the
star-formation rate, can explain the monotonic rise in the
dust-to-
stellar mass ratio and reproduce the relationship between mean
dust density and
redshift remarkably accurately.
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All authors Stephen Eales, Matthew Smith, Tom Bakx, Jordan D'Silva, Feng-Yuan Frey Liu, Aparna Venkateshwaran
Astrophysics of Galaxies
The PARADIGM Project II: Characterising Nuclear and Diffuse Radio Components in Local U/LIRGs
Geferson Lucatelli, Rob Beswick, Javier Moldón et al. (+14 more)
Disentangling SF and AGN emission is essential for understanding
galaxy evolution, yet remains challenging in merging systems where both processes are enhanced and spatially intertwined.
Galaxy mergers drive gas inflows that simultaneously fuel
nuclear SBs and BH
accretion, shaping morphology from
nuclear ($\lesssim 250$~pc) to large-scale ($\gtrsim 500$~pc) regions.
Radio interferometry provides an unobscured view, but separating compact
nuclear SBs, AGN, and diffuse SF requires multiscale, multi-frequency observations. We present a systematic method to characterise multiscale
radio properties in 15 local ($z\lesssim 0.1$) U/LIRGs ($L_{\mathrm{IR}} > 10^{11}\mathrm{L}_{\odot}$). Using e-MERLIN and VLA at 1.4, 6.0 and 33.0~GHz, we probe physical scales from $\sim 10$–$250$~pc to $\sim 0.5$–$3.0$~kpc. We decompose
radio emission into
nuclear (compact cores and
nuclear extended) and large-scale (total and diffuse) components, comparing morphological properties (emission fractions, sizes, luminosities, surface densities) and investigating correlations with source classes, merger stages, and $L_{\mathrm{IR}}$. We find: i)
nuclear emission contributes $\sim$50% of total
radio emission on average; ii) total multiscale diffuse emission (SF-related) contributes $\sim$80% to total power; iii)
nuclear emission components act together to correlate with total
radio and infrared luminosities, which increase with merger stage, whilst diffuse emission at larger scales shows no clear dependence on
nuclear processes; iv) sources with
radio excess (lower $q_{\mathrm{IR}}$) show lower
nuclear luminosity ratios $L_{\mathrm{R,33}}^{\mathrm{N}}/L_{\mathrm{R,6}}^{\mathrm{N}}$, indicating a deficit of high-$\nu$
radio emission; since 33.0~GHz traces recent SF, this suggests the
radio excess is dominated by non-thermal emission at lower $\nu$, likely AGN-related, rather than enhanced SF.
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All authors Geferson Lucatelli, Rob Beswick, Javier Moldón, Antxon Alberdi, Miguel Á. Pérez-Torres, Santiago del Palacio, Kelvin Wandia, Susanne Aalto, L. Barcos-Muñoz, D. Williams-Baldwin, J. E. Conway, Cristina Romero-Cañizales, Eskil Varenius, Hans-Rainer Klöckner, Simon T. Garrington, Willem A. Baan, Ylva M. Pihlstrom
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
The stability of color-flavor-locked quark matter and massive CFL quark stars
Wen-Li Yuan and Bikai Gao
Owing to the emergence of attractive interactions between
quarks, color superconductivity is expected to occur, with the color-
flavor-locked (CFL) phase favored at high densities. This work investigates the absolute stability of beta-equilibrated CFL
quark matter in bulk within the modified Nambu-Jona-Lasinio model, under color and electric charge neutrality conditions relevant to compact
stars. Motivated by the possible existence of an ultra-low-mass central compact object in the
supernova remnant HESS J1731-347 and the "mass-gap" secondary component in the GW190814 event, we systematically explore how vector repulsion, attractive diquark pairing, and nonperturbative
vacuum effects influence the stiffness of CFL
quark matter and its stability. Our findings suggest the existence of a physically viable region of parameter space in which the CFL phase is the true ground state of strongly interacting matter, thereby theoretically supporting the scenario of self-bound
quark stars. This configuration is not only consistent with current astrophysical constraints from NICER and LIGO/Virgo observations, but also provides a possible explanation for both the $~2.6\ M_{\odot}$ secondary component in GW190814 and the ultra-low-mass compact object with $M = 0.77^{+0.20}_{-0.17}\ M_{\odot}$in HESS J1731-347.
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High Energy Astrophysical Phenomena
Evidence for Intermediate-Mass Black Holes From Microlensing Signatures in CHIME/FRB catalog 2
Huan Zhou, Zhengxiang Li, Cheng-Gang Shao et al. (+4 more)
Intermediate-mass black holes (IMBHs) are the missing link in the
cosmic hierarchy of black holes, bridging the gap between
stellar-mass black holes and supermassive ones. They also serve as unique laboratories for testing strong-field
gravity and are
prime targets for future multi-messenger observations. However, IMBHs are a population that has remained notoriously difficult to detect. The microlensing effect of fast
radio bursts (FRBs) can serve as a clean and powerful method to probe IMBHs. In this work, we develop a pipeline to search for microlensed FRBs based on their dynamic spectra and apply it to the CHIME/FRB Catalog 2. Two microlensing signatures have been identified in two separate sources, i.e. FRB~20190131D and FRB~20211115A. The inferred lens masses for these two signatures are $\sim[280-467]~M_{\odot}$ and $\sim[539-609]~M_{\odot}$, respectively. Here we interpret them as evidence for IMBHs. If there are no intervening structures-such as
galaxies or clusters-along the line of sights for these two sources, the two identified IMBHs might be isolated and of
primordial origins. In that case, we obtain
primordial black holes (PBHs) within these two mass ranges would constitute $\sim4\%$ of dark matter. Moreover, if these two candidates are not genuine
lensing signatures, the abundance of intermediate-mass PBHs with masses $>300,M_{\odot}$ is constrained to be $\sim13\%$ at $95\%$ confidence level. Therefore, more comprehensive observational information for FRBs, together with a deeper understanding of whether the intrinsic emission mechanisms of FRBs can produce
lensing-like signals, will be crucial for establishing this effect as a powerful tool for probing (
primordial) IMBHs.
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All authors Huan Zhou, Zhengxiang Li, Cheng-Gang Shao, Xi-Jing Wang, Kai Liao, He Gao, Zong-Hong Zhu
Earth and Planetary Astrophysics
Mare versus highland lunar impact flash light curve dichotomy
D. Athanasopoulos, A. Liakos, A. Z. Bonanos et al. (+5 more)
We perform a comprehensive analysis of lunar impact flash (LIF) light curve shapes and their dependence on the lunar terrain, using the large sample of LIFs detected by NELIOTA over the last 9 years. We classified 124 multi-frame light curves into mare, highland and `border' regions. Subsequently, we derived analytical expressions for single-size and dual-size ejecta cooling models, which were fitted to the observational data to estimate their physical properties. While impacts on both terrains yield similar peak magnitude distributions, their decay behaviour differs significantly; highland LIFs exhibit a shallower and longer-lasting decay compared to mare flashes, which are faster and steeper. The dual-size model suggests this extended duration is primarily driven by the fine droplets of the ejecta. The profile and duration of the LIF light curves represent the initial stages of the impact cratering process. The observed dichotomy between highland and mare LIFs demonstrates that the initial stages of the impact cratering process are fundamentally dependent on lunar lithology.
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All authors D. Athanasopoulos, A. Liakos, A. Z. Bonanos, D. Koschny, O. Sykioti, M. Devogèle, J. L. Cano, R. Moissl
Cosmology and Nongalactic Astrophysics
Anisotropy and tracer-profile assumptions in aperture-based strong-lens dynamics: Conditional inference from supernova distance ratios and unresolved stellar kinematics
Jian Hu, Yi Liu, Chen Wang et al. (+4 more)
Single-aperture
stellar kinematics jointly constrain the mass distribution, tracer light profile, and velocity anisotropy. Their coupling affects the interpretation of an inferred anisotropy. We quantify how tracer-profile assumptions and data treatment affect common-anisotropy comparisons and inferred mass-density slopes in a compiled
galaxy-scale lens sample. We analyse 107 lenses using distinct \pantheon\
supernova counterparts, spatial flatness, distance duality, and the full
supernova covariance. We compare the individual-slope power-law tracer with Hernquist and Sérsic profiles using measured effective radii. Numerical Jeans solutions, likelihood comparisons, posterior distributions, and controlled recovery experiments quantify the effects of tracer representation. The power-law fixed-minus-free
Bayesian information criterion differences are 6.74 for isotropy and 41.51 for fixed $\beta=0.18$, compared with $-3.89$ and $-2.26$ for Hernquist and $-4.67$ and $-4.30$ for Sérsic $n=4$. The preference also changes with Sérsic index. Removing 12 systems with linearised distance-ratio uncertainty above 20% reduces the power-law isotropy comparison to 2.51. In isotropic Sérsic $n=4$ and Hernquist simulations, power-law fits yield $\Delta\mathrm{BIC}_0>6$ in 60.0% and 50.0% of realisations, respectively, compared with 0.5% and 1.0% for matched-tracer fits.} {The preference for a common free anisotropy parameter depends on the tracer representation and sample composition. Controlled recovery identifies tracer mismatch as one mechanism that can generate this preference within the adopted aperture models. Physical interpretation requires joint treatment of photometry, distance uncertainties, and kinematic weighting.
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All authors Jian Hu, Yi Liu, Chen Wang, Jian-Ping Hu, Jia Zhao, Liangqing Zhu, Zhongmu Li
High Energy Astrophysical Phenomena
From mass-loss histories to lightcurves: a generalised framework for interaction-powered transients
Nikhil Sarin and Ryosuke Hirai
We introduce a fast ($\sim 1$–$50$ ms) and generalised public framework for modelling interaction-powered transients. The framework solves the thin-shell equations of motion for ejecta colliding with circumstellar material (CSM), and supports arbitrary CSM density and velocity profiles, including steady winds, eruptions, and complex time-variable mass-loss histories. For optical/UV lightcurves, we implement two luminosity treatments: a one-zone mode based on the thin-shell shock power, and a finite-shell transport mode that evolves trapped radiation,
photon diffusion, shock emergence, and post-emergence cooling for finite, static CSM shells. In a
benchmark comparison, the transport calculation and an optional time-dependent shock-efficiency prescription reproduce the main qualitative and quantitative features of a one-dimensional radiation-hydrodynamical simulation. We use the same shock solution to post-process
radio synchrotron and thermal bremsstrahlung X-ray predictions, enabling self-consistent multi-wavelength diagnostics. We show that the assumed CSM velocity structure can significantly affect inferred parameters even when the density profile at explosion is identical, and that aspherical CSM can mimic multiple spherical shells in bolometric lightcurves. We demonstrate the framework through recovery of a synthetic time-variable mass-loss history and applications to six transients: the Type IIn SN~2010jl, the rapidly evolving stripped-envelope SN~2023xgo, the Type Ia-CSM SN~2020aeuh, the hydrogen-poor superluminous SN~2015bn, the eruptive LBV-like transient SN~2009ip, and the long-duration interacting event iPTF14hls. The inferred CSM structures span steady or enhanced winds, thermonuclear interaction, eruptive density enhancements, and highly structured pre-
supernova mass loss, illustrating the framework's utility for inference on upcoming samples of interacting transients.
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High Energy Astrophysical Phenomena
Recent Findings from the Telescope Array Experiment
Jihyun Kim
The
Telescope Array (TA) is the largest ultra-high energy
cosmic ray (UHECR) observatory in the Northern Hemisphere. Together with its extensions, TA Low Energy (TALE), TALE infill, and the TA$\times$4 array, it measures extensive air showers (EAS) initiated by UHECRs across an energy range spanning from $10^{15}$ eV to beyond $10^{20}$ eV. All components of the experiment employ a hybrid detection approach, combining plastic scintillator arrays that sample the EAS footprint at ground level with
telescopes that record fluorescence and Cherenkov light from shower development in the atmosphere. The ongoing construction of TA$\times$4 will significantly increase statistics at the highest energies by expanding the surface detector area by a factor of four. In addition, the recently deployed TALE infill array further lowers the hybrid energy threshold of TALE. This presentation summarizes the current status of the TA experiment and highlights recent findings on the energy spectrum, mass composition, and anisotropy.
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Solar and Stellar Astrophysics
Towards inertial-mode helioseismology: Direct sensing of solar rotation at 75 deg latitude and 0.8 Rsun
Prithwitosh Dey, Laurent Gizon and Yuto Bekki
Solar internal rotation at high latitudes is poorly constrained by acoustic-mode helioseismology. Global inertial modes observed on the Sun are highly sensitive to
solar differential rotation and may provide new diagnostics of rotation in these regions. We aim to constrain
solar rotation with the measured frequency of the $m=1$ high-latitude inertial mode, starting from the HMI/SDO reference rotation profile given by p-mode helioseismology for 2010-2024. Using a validated and accurate
eigenvalue solver, we compute the perturbation to the mode frequency resulting from localised changes in the differential rotation rate throughout the
solar interior. We find that the linear sensitivity kernel of the $m=1$ high-latitude mode peaks at latitude 75 deg and radius $0.8 R_\odot$, with full widths of 7 deg and $0.13 R_\odot$. From the observed mode frequency in the Carrington frame, $-87.9 \pm 1.9$ nHz (retrograde, averaged over 2010-2024), we infer that the
solar rotation rate near this location is $365.3\pm 2.0$ nHz, which exceeds the reference p-mode estimate by $8.1$ nHz. Additionally, we propose a latitudinally smooth, radially independent modification to the rotation rate at high latitudes beyond the linear (small-perturbation) regime. This work demonstrates that individual inertial modes can provide direct constraints on rotation in the bulk of the
solar convection zone, well below the surface, representing the first example of spatially resolved inertial-mode helioseismology.
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Astrophysics of Galaxies
A Value-added Physical Properties Catalog for Low-redshift Galaxies from DESI Legacy Imaging Surveys DR10
Shirui Wei, Changhua Li, Yanxia Zhang et al. (+6 more)
Galaxy physical properties-such as
star formation rate (SFR),
stellar mass, and gas-phase
metallicity-are essential for population studies and evolutionary analyses. Deriving these quantities for billions of
galaxies in modern imaging surveys presents significant challenges due to limited spectroscopy and the computational costs associated with traditional spectral energy distribution fitting. As a result, many
galaxies in large photometric surveys still lack homogeneous property estimates. This study introduces a
multimodal deep learning model that integrates optical imaging with photometric catalog features to estimate SFR,
stellar mass, and oxygen abundance in low-
redshift galaxies. The model incorporates a ResNet-based convolutional neural network to extract spatial information from multiband images and a multilayer perceptron that processes catalog-level photometric features, leveraging complementary constraints from morphology, surface brightness, and broadband colors. Trained on reference measurements from the MPA-JHU DR8 catalog, the model is optimized for efficient large-scale estimation. When applied to the DESI Legacy Imaging Surveys (LS) DR10, the model generates a value-added catalog containing physical property estimates for approximately 547 million
galaxies with
redshifts z <= 0.5. Validation through comparisons with independent catalogs and exploration of key scaling relations demonstrates that while the derived properties are not intended for precision measurements of individual objects, they effectively capture the dominant astrophysical trends necessary for ensemble studies. This catalog represents the first homogeneous set of photometry-based SFR,
stellar mass, and
metallicity estimates for DESI LS DR10, providing a vital resource for statistical studies of
galaxies in the local Universe and facilitating comparisons with current and future spectroscopic surveys.
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All authors Shirui Wei, Changhua Li, Yanxia Zhang, Chenzhou Cui, Jinghang Shi, Wujun Shao, Zihan Kang, Yongheng Zhao, Maoyuan Huang
High Energy Astrophysical Phenomena
The Astro2Geo Project I. Radio astrometric offsets correlated with Gamma-ray brightness
Jeffrey A. Hodgson, Hana Krasna, Aletha de Witt et al. (+2 more)
Precision geodesy relies on the stability of the International Celestial Reference Frame (ICRF), yet its reference sources, Active
Galactic Nuclei (AGN), exhibit changes in source structure that can manifest as apparent shifts in their astrometric positions. The high-precision
radio measurements used to maintain the ICRF therefore provide a means to investigate the astrophysical mechanisms driving these changes. In particular, the observed astrometric variability offers a unique opportunity to link positional shifts in AGN to high-energy astrophysical processes. We investigated the relationship between the astrometric positions of ICRF AGN and their Gamma-ray emission. We measured the positional offsets of
radio cores relative to the ICRF3 at both S/X and K bands and compared them to
Fermi-LAT Gamma-ray fluxes within +/-30 days. Out of 92
radio sources, we identified 57 that had enough overlapping data. We find a high incidence of statistically significant (p<0.05) power-law correlations, with ~90% of sources exhibiting this behaviour. The nature of this correlation is complex: we observe both positive and negative correlations, and the sign of the correlation can differ between the two frequency bands for the same source. To explain the correlations, we tested variable Gamma-ray emission locations, changes in
nuclear opacity, and variations in jet position angle. Our analysis reveals no single explanation and suggests a complex interplay of multiple physical mechanisms. A search for time lags between the
radio position offsets and Gamma-ray fluxes revealed tentative - and highly caveated - evidence for a time-delay in only five sources. A statistical comparison with the OCARS catalogue shows that, although our sample is biased towards optically brighter sources with better-constrained astrometric solutions, it remains representative of the broader AGN population in terms of
redshift.
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All authors Jeffrey A. Hodgson, Hana Krasna, Aletha de Witt, Pfesesani van Zyl, Janeth Valverde
Instrumentation and Methods for Astrophysics
Methodological Synergies between Technosignature and UHE Neutrino Searches
Paramita Dasgupta
Radio technosignature searches and
radio-based ultra-high energy (UHE)
neutrino experiments address different scientific questions, but share a closely related data analysis problem: identifying rare signals of unknown morphology within large
datasets dominated by thermal noise and anthropogenic
radio-frequency interference (RFI). UHE
neutrino radio experiments (including ARA, RNO-G, ANITA, and PUEO) have developed advanced methodologies for continuous-wave (CW) mitigation and background characterization. This invited contribution makes that connection concrete through three points. First, we demonstrate that catalog-based time-domain sine subtraction – the CW mitigation technique used in ANITA and ARA – can be adapted for technosignature pipelines by restricting subtraction to documented persistent contaminants, improving broadband transient visibility while preserving uncataloged narrowband candidates. Second, we identify a structural equivalence between spatiotemporal clustering used in UHE
neutrino experiments and direction/cadence-based RFI rejection in
radio SETI, proposing a joint feature space incorporating direction, time, frequency, bandwidth, duration, and polarization. Third, we argue that background-only anomaly ranking is the natural second stage of this workflow, providing morphology-agnostic candidate triage. Together, these ideas motivate a 'preserve-then-rank' workflow for commensal rare-event discovery, opening a near-term path toward cross-community collaboration.
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Cosmology and Nongalactic Astrophysics
Prospect of Measuring the Cosmic Dipole by Associating Strongly Lensed Gravitational Waves with Galaxy Surveys
Anson Chen and Jun Zhang
The
cosmic dipole observed in the
cosmic microwave background (CMB) is traditionally interpreted as being caused by the observer's motion relative to the background. However, tensions with dipole measurements from
radio galaxy counts motivate the need for independent probes. This work investigates the feasibility of using strongly lensed gravitational wave (GW) events to measure the
cosmic dipole. Strongly lensed GWs produce multiple time-delayed images, which can be used to infer the distances to both the lens and the source. These distances, associated with the observed
redshifts of the lens and the source from
galaxy catalogues, encode information about the background cosmology and
cosmic dipole effects. By reconstructing a statistical sample of doubly lensed GW events based on the singular isothermal sphere lens model, the
cosmic dipole can be estimated jointly with background cosmological parameters. Using realistic simulations for Einstein
Telescope and
Cosmic Explorer, we forecast that a dipole magnitude $g$ consistent with both the CMB and number count measurement could be detected with 10 years of observation. Furthermore, constraints on $g$ are greatly improved by combining constraints from doubly lensed events with those from triply or quadruply lensed events. In the most optimistic scenario, where we measure the number count dipole magnitude with 10 years of observation, we obtain $g = (2.45^{+1.53}_{-1.28}) \times 10^{-3}$ from the combined constraint, provided that systematic uncertainties are mitigated. Although challenging, strongly lensed GWs offer a novel approach to measuring the
cosmic dipole, providing an independent consistency test with different systematics from electromagnetic probes.
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High Energy Astrophysical Phenomena
Radio-X-ray Time Lags in GX 339-4: Probing Magnetic Field Transport in Black Hole Accretion
Dizhan Du, Bei You, Zhen Yan et al. (+2 more)
We present an analysis of the time delay between the
radio emission and the X-ray Compton luminosity during the 2010-2011 outburst of GX 339-4. Using the interpolated cross-correlation function (ICCF), we measure the time delay between the Compton luminosity and the
radio luminosity, and find that during the rising hard state, the
radio emission precedes the Compton luminosity by approximately 3 days. In contrast, in the decaying hard state, the
radio emission lags behind the Compton luminosity by about 8 days. By estimating the mass
accretion rate and the disk truncation radius, the calculated inner
magnetic field can account for both the
radio delay in the decaying hard state and the
radio precedence in the rising hard state. The time delays observed in different outbursts across multiple sources are compared further, and the underlying physical mechanisms account for this difference are discussed. These results provide insights into the evolving coupling between the inner
accretion flow and the jet in black hole X-ray binaries.
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All authors Dizhan Du, Bei You, Zhen Yan, Yuao Ma, Xinwu Cao
Solar and Stellar Astrophysics
Chromospheric resonator model for sunspot revealed by multi-height observation of umbral wave
Kartika Sangal, A.K. Srivastava, Libo Fu et al. (+3 more)
Sunspots are transient, magnetically intense features that host oscillations linked to magnetohydrodynamic (MHD) waves. These waves may contribute to
plasma heating and drive mass flows in the
solar wind. Beyond their energetic role, they serve as diagnostic tools for probing sunspot structure. In this study, we investigated chromospheric wave propagation in a sunspot using high-resolution, multi-wavelength observations from the Goode
Solar Telescope at Big Bear
Solar Observatory. Spectral analysis shows that the intensity at H$\alpha$ line core and its wings exhibited oscillatory signal at about 3 min. We performed a cross-wavelet analysis to examine the phase relationship between the wing-integrated and line-core intensity oscillations of the H$\alpha$ line and the centroid-derived H$\alpha$ Doppler velocity. We also analyze the phase relationships between intensity pairs from different passband combinations of the H$\alpha$ line. The results indicate the presence of slow magnetoacoustic modes manifesting standing waves along with upward propagating waves. The observed phase patterns suggest that umbral waves are confined within a non-ideal acoustic resonator, providing measurable wave properties that could serve as input for sunspot seismology and refine models of sunspot atmospheric structure.
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All authors Kartika Sangal, A.K. Srivastava, Libo Fu, Ding Yuan, Song Feng, Yuandeng Shen
Cosmology and Nongalactic Astrophysics
Memory burden effect of regular primordial black holes
Jin-Rong Du, Zi-Zhuo Zhang and Nan Li
Primordial black holes (PBHs) have attracted intensive research interest as a promising candidate of dark matter. However, because of the Hawking radiation, the PBHs lighter than $10^{15}~\rm{g}$ have already evaporated before today. To extend the PBH mass window to small-mass range, two possible ingredients are explored. The first is the consideration of regular PBHs with non-singular metrics, which can decrease the Hawking temperature, thereby lowering black hole evaporation. The second is the incorporation of the
memory burden (MB) effect, which can further suppress the evaporation rate, after regular PBHs have lost a certain amount of their initial masses. In this work, we combine these two ingredients and study the MB effects of three types of regular PBHs (the Hayward, Bardeen and Simpson–Visser black holes). Assuming a phenomenological self-similar evaporation, we find that the MB effect significantly relaxes the evaporation constraints. For a
benchmark of the MB strength parameter $k=1$, a new PBH mass window opens at around $10^6$–$10^8$ g, where regular PBHs can compose all dark matter without violating the Big Bang nucleosynthesis bounds.
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Instrumentation and Methods for Astrophysics
Spectro Capture: A Software System for Automated Small-Observatory Spectroscopy
Paul Luckas
Spectro Capture is a Python-based software system developed to automate small- observatory fibre-fed spectroscopy. The system integrates target selection,
telescope slewing, guide
star acquisition, fibre position restoration, calibration and science exposure sequencing within a single observing workflow. The paper describes the design and operational behaviour of the system at Shenton Park Observatory, where it has been used for unattended multi-target spectroscopic observing. Log analysis from January to May 2026 shows that the system completed 339 of 345 attempted science target blocks in primary unattended batch runs, corresponding to a completion rate of 98.3%. The results demonstrate that reliable unattended spectroscopy is practical at a small observatory when target acquisition, guiding, scheduling and calibration control are treated as an integrated software problem.
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Astrophysics of Galaxies
Formation of a nuclear star cluster through the inspiral of globular clusters: A case study of the dwarf elliptical galaxy UGC 7346
Ismael Khan, Fazeel Mahmood Khan, Andrea V. Macciò et al. (+2 more)
Nuclear star clusters (NSCs) are dense
stellar environments located in the center of most
galaxies. NSCs are thought to form through two primary methods; through the inspiral of globular clusters (GCs) to the
galactic center due to dynamical friction, and through in-situ
star formation. Recent observations of
dwarf elliptical
galaxy UGC 7346 suggest that it might be undergoing NSC formation due to the presence of multiple GCs near its photometric center. We perform direct N-body simulations of nine GCs belonging to UGC 7346's GC system to investigate whether their eventual infall to the
galactic center would result in the formation of a NSC. Our simulations indicate that GC inspiral leads to the formation of a central
stellar over-density relative to the background profile of the host
galaxy within $\sim$1.5 Gyr, corresponding to a NSC with a typical mass of $(4.1\text{-}4.5)\times 10^5 M_{\odot}$. Several key structural parameters of the newly formed NSC, including the Sérsic index, effective radius, and central
stellar density, lie well within the range observed for NSCs. We also test a hypothetical scenario in which some of the infalling GCs have larger masses ($M \sim 10^6 M_{\odot}$), resulting in the formation of a more massive NSC whose mass and size are more consistent with observations. Our results suggest that inspiral of GCs is a viable channel for assembling a significant mass in the shape of NSC in the center of
dwarf galaxies and that UGC 7346 will host a NSC at its center in about 2-3 Gyr.
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All authors Ismael Khan, Fazeel Mahmood Khan, Andrea V. Macciò, Kelly Holley-Bockelmann, Peter Berczik
Astrophysics of Galaxies
Dwarf and Intermediate-Mass Galaxies in MaNGA: Evidence for Different Evolutionary Trends
Chandan Watts, Gothai L and Sudhanshu Barway
We investigate the interplay between morphology, specific
star formation rate (sSFR), and local environment using a sample of 7,408
galaxies from the SDSS-IV MaNGA survey. Our analysis spans
stellar masses from
dwarf to massive
galaxies, enabling a unified view of how
stellar mass and environment regulate
galaxy evolution.
Galaxies are classified by morphology (ellipticals (E), lenticulars (S0s), early-type spirals (ETS), and late-type spirals (LTS)) and local environmental density, with
star formation activity traced using sSFR. Low-mass
galaxies ($\log (M_{\star}/M_{\odot}) < 10$) are predominantly
star-forming and dominated by LTS, whereas high-mass
galaxies ($\log (M_{\star}/M_{\odot}) \geq 10$) are dominated by ETS and are largely quenched. By separating
dwarf ($\log (M_{\star}/M_{\odot}) \leq 9.5$) and intermediate-mass
galaxies ($9.5 < \log (M_{\star}/M_{\odot}) < 10$), we find that
dwarf galaxies remain predominantly
star-forming with only weak environmental dependence, whereas intermediate-mass
galaxies exhibit clearer environmental trends toward quenching. Using the D4000 index as a tracer of long-term
stellar population aging, we further show that
dwarf E and S0s host systematically younger
stellar populations than their intermediate-mass counterparts, implying reduced quenching efficiency and more gradual environmental processing in the
dwarf regime. This distinction is not evident among spiral
galaxies, whose
stellar population properties are comparatively insensitive to the
dwarf versus non-
dwarf classification. Overall, these results indicate that the commonly defined low-mass
galaxy population is not homogeneous and that
dwarf and intermediate-mass
galaxies show systematically different evolutionary trends. Treating them separately is therefore essential for interpreting
galaxy evolution in the low-mass regime.
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Solar and Stellar Astrophysics
Gaia21bja: pre-main sequence star with quasi-periodic bursts
Ádám Mátéfy, Zsófia Nagy, Ágnes Kóspál et al. (+12 more)
Gaia21bja is a
Gaia alerted young
stellar object (YSO) that exhibits at least seven quasi-peridoic brightenings over a 20 year-long light curve with durations of 1.5-2 years and amplitudes up to $\sim$1.7 mag in the
Gaia $G$-band. We analyze its optical and near-infrared photometry and spectra taken using the IRTF and VLT in its faint and bright states in order to characterize its physical properties. A Lomb-Scargle periodogram analysis results in a most significant period of $916\pm77$ days. We derived the
stellar parameters as $R_\star= 0.78 \pm 0.04~R_\odot$, $L_\star=(4.5\pm0.3) \times 10^{-2}~L_\odot$, and $M_\star= 0.16 \pm 0.03~M_\odot$. The spectra taken during the burst are dominated by emission lines and are similar to those of EX Lupi-type eruptive young
stars (EXors). We found that the
accretion luminosity and mass
accretion rate increased by a factor of $5.5-6$ during the burst. Based on this, and the quasi-periodic bursts, we suggest that
Gaia21bja is an eruptive YSO, and is most consistent with the `Periodic' category of the Outbursting YSOs Catalogue.
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All authors Ádám Mátéfy, Zsófia Nagy, Ágnes Kóspál, Péter Ábrahám, Fernando Cruz-Sáenz de Miera, Máté Szilágyi, Michał Siwak, Eleonora Fiorellino, Teresa Giannini, Mária Kun, László Szabados, Gábor Marton, Patrik Németh, Brunella Nisini, Zsófia Marianna Szabó
Cosmology and Nongalactic Astrophysics
AMPM II. A Lunar-Mass Primordial Black Hole Microlensing Candidate in the Milky Way Halo
Renee Key, Edward N. Taylor, Ken C. Freeman et al. (+5 more)
Primordial Black Holes (PBH) are hypothesised to form during inflation and have long been considered a candidate for compact dark matter. Gravitational microlensing is known as a productive method for
exoplanet discovery and characterisation, but also provides an experimental avenue to constrain the PBH abundance in the mass regime from $\sim 10^{-11}\ M_{\odot}$ to $\sim 10^5\ M_{\odot}$. We performed a high-cadence, optical microlensing survey with DECam over five nights towards the Large Magellanic Cloud, sensitive to microlensing timescales from minutes to days. Here, we report the discovery of an hour-long microlensing event. An optical depth probabilistic analysis indicates that the
lensing object, which we refer to as Phoebe, is 5 orders of magnitude more likely to be part of the Milky Way's dark matter
halo than part of the
stellar content of the Milky Way and Large Magellanic Cloud. No matter the location of Phoebe, it is among the fastest and lowest mass microlensing signals ever detected, with an Einstein timescale of approximately 60 minutes. Using
Bayesian modelling, we interpret Phoebe as a PBH with mass $0.032^{+0.227}_{-0.027} M_{\oplus}$, or approximately 3 lunar masses. Phoebe suggests a population of compact, lunar-mass objects associated with the dark matter distribution of the Milky Way, and potentially opens a new window to the physics of inflation.
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All authors Renee Key, Edward N. Taylor, Ken C. Freeman, Jeremy Mould, Abhijit Saha, Anais Möller, Timothy M. C. Abbott, Alan R. Duffy