Solar and Stellar Astrophysics
Solar chemical composition
A. M. Amarsi and N. Grevesse
The Sun is one of the fundamental
benchmarks in astronomy, and there is ever growing interest in precise and accurate determinations of its chemical composition. We present the current state-of-the-art in spectroscopic determinations of the solar elemental abundances, that now routinely employ three-dimensional (3D) radiative-hydrodynamic simulations of the solar photosphere and post-processing in non-local thermodynamic
equilibrium (non-LTE). We critically review the recent literature and present recommended present-day and protosolar abundances of the 83 long-lived elements, and discuss their implications vis-à-vis primitive meteorites, helioseismology,
neutrino fluxes, and the Solar Modelling Problem.
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Instrumentation and Methods for Astrophysics
Development of an adaptive optics testbed at MPIA for the ELT/Planetary Camera and Spectrograph (PCS)
Raphaël Pourcelot, Thomas Bertram, Peter Bizenberger et al. (+5 more)
The Planetary Camera and Spectrograph (PCS) is a proposed second-generation instrument for the Extremely Large
Telescope (ELT), dedicated to the direct imaging and characterization of
exoplanets. To meet its demanding science requirements, PCS will incorporate an extreme adaptive optics (AO) system, building upon the heritage of existing ELT AO instruments such as ELT/METIS, as well as high-contrast AO systems at the ELT and the VLT, including SPHERE and its upcoming upgrade, SAXO+. PCS development requires extensive research and development to advance critical AO technologies. In this work, we present the Max Planck Institute for Astronomy (MPIA) plan for a modular testbed to validate key components and control strategies. This testbed will integrate two deformable mirrors, including a DM prototype developed by Bertin-ALPAO in collaboration with ESO, with an estimated delivery in 2029. The facility will enable testing of different
Fourier filtering wavefront sensors, including novel mask designs, while exploring different control architectures, such as woofer-tweeter configurations with a single wavefront sensor for both deformable mirrors or fully independent AO stages. Additionally, the testbed will leverage MPIA's expertise in real-time computer development to experiment with advanced control strategies, including predictive control and machine learning-enhanced AO techniques. This contribution presents the current status of PCS development at MPIA, highlighting the ongoing R&D efforts to mature its AO system for high-contrast imaging with the ELT.
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All authors Raphaël Pourcelot, Thomas Bertram, Peter Bizenberger, Markus Feldt, Markus Kasper, Silvia Scheithauer, Stefan Ströbele, Horst Steuer
High Energy Astrophysical Phenomena
Neutron star masses from electron-capture supernovae under equation-of-state uncertainties
Vishal Parmar, Domenico Scordino and Ignazio Bombaci
Electron-capture
supernovae (ECSNe) are a promising formation channel for low-mass
neutron stars, but the minimum gravitational mass of the
neutron stars they produce depends on both the progenitor core structure and the
neutron-
star matter equation of state (EOS). We compute the electron-capture (EC) threshold gravitational mass ($M^\star_{WD}$) of cold white-dwarf-like O–Ne–Mg cores with representative compositions and map the baryon number onto cold
neutron-
star configurations constructed from a
Bayesian ensemble of unified crust–core EOSs. Although the EC threshold density is sensitive to the concentrations of the O–Ne–Mg mixture, the threshold baryon number of the O–Ne–Mg core varies only weakly, producing a narrow remnant-mass window. In the baseline case with no baryonic mass loss during the transition from the EC threshold mass O–Ne–Mg core to the remnant
neutron star, standard ECSNe yield remnant
neutron stars with gravitational masses of $1.24$–$1.265\, M_\odot$, with only a small EOS-induced spread. Small baryonic mass losses of $0.01$–$0.02\, M_\odot$ shift this range modestly downward, but the $1.174\, M_\odot$ companion of PSR J0453+1559 would require an extreme mass loss close to $0.10\, M_\odot$, which is not favored by current ECSN simulations. We find that the residual EOS dependence of the remnant mass is controlled mainly by the pressure around nuclear saturation density, while the corresponding tidal deformability remains sensitive to the remnant radius and compactness. Thus, low-mass double
neutron star systems can in principle connect ECSN-like formation channels with gravitational-wave constraints on the EOS. Our results show that ECSNe naturally form low-mass
neutron stars, but within a restricted mass range; the lightest observed
neutron stars likely require low-mass iron-core collapse, ultra-stripped
supernovae, or other nonstandard channels.
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High Energy Astrophysical Phenomena
Reconstructing the Auger UHECR Dipole: A Hybrid Analysis of 4LAC AGNs and Nearby Starburst Galaxies
Swaraj Pratim Sarmah, Umananda Dev Goswami and Sovan Chakraborty
The large-scale dipole anisotropy observed by the Pierre Auger Observatory above $8$~EeV provides important clues about the origin of ultra-high-energy
cosmic rays (UHECRs). In this work, we investigate whether gamma-ray active galactic
nuclei (AGNs) from the Fermi-LAT Fourth AGN Catalog (4LAC) can explain the observed dipole and examine the contribution of nearby starburst
galaxies (SBGs). Incorporating source fluxes,
redshift distributions, GZK attenuation, and a mixed-composition framework, we demonstrate that single-source populations of AGNs and SBGs alone fail to reproduce the observed Auger dipole. To resolve this, we construct a hybrid AGN+SBG model. The best-fit solution for the $8$–$16$~EeV interval requires a $23$% AGN contribution and $45$% SBG contribution, which gives a dipole amplitude of $5.03$% while maintaining the dipole direction of ($104.1^\circ$, $-25.1^\circ$) with angular separation of $7.10^\circ$. In the other energy intervals also, we find that the nearby SBGs increasingly dominate the anisotropic component while AGNs provide a subdominant contribution alongside a quasi-isotropic background.
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Instrumentation and Methods for Astrophysics
Effects of near-surface sedimentary structure on Newtonian noise for the Einstein Telescope: a 2-D numerical study
Shi Yao, Patrick Schillings, Johannes Erdmann et al. (+1 more)
Near-surface low-velocity sediments can strongly modify seismic wavefields and therefore affect estimates of Newtonian noise at underground gravitational-wave observatories. We investigate these effects using 2-D viscoelastic simulations of a sediment layer overlying hard-rock basement. Controlled experiments examine the influence of sediment-basement interface geometry, sediment shear-wave velocity, attenuation, and test-mass position. Relative to a homogeneous model, the sediment layer produces frequency-dependent changes through wave trapping, interference, and attenuation. A constant-thickness layer generates a more laterally coherent wavefield and a sharper spectral enhancement than a basin-shaped interface, whereas lateral thickness variations broaden and shift the response. Sediment shear-wave velocity primarily controls the frequencies of the spectral features, while attenuation mainly controls their amplitudes. Newtonian noise is most sensitive to sediment structure for test masses located within or several hundred meters below the sediment layer. The sensitivity to lateral variations in sediment thickness decreases with burial depth and is weak at 2 km depth in the present model. These results demonstrate that near-surface sedimentary structure should be represented explicitly when assessing site-dependent Newtonian noise, particularly for test masses located between 200 m and 300 m depths.
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All authors Shi Yao, Patrick Schillings, Johannes Erdmann, Andreas Rietbrock
Instrumentation and Methods for Astrophysics
When a neural surrogate cannot accelerate a solver: runtime share, closed-loop drift, and the economics of uncertainty gating in a stiff coupled simulation
L. Thümmler and T. Kuroda
Learned surrogates for expensive inner solver blocks are a widely pursued route to faster multiphysics simulation. We report a controlled, end-to-end negative result and identify three structural barriers, none of them a deficiency of the network we trained. The testbed is the implicit Newton solve coupling energy-dependent
neutrino radiation to matter in a general-relativistic radiation-hydrodynamics code, its most expensive physics routine per call. First, per-call cost and share of runtime are different quantities, and only the second bounds acceleration. An exclusive self-time profile puts the target block at 16.9% of critical-rank wall clock, capping any surrogate at ~1.2x by Amdahl's law. A surrogate 5.8x cheaper per call merely ties the solver, and the configuration stable enough to run without fallback reaches only parity. Second, offline accuracy cannot rank surrogates for deployment: across fourteen networks the pooled Spearman error-versus-survival correlation (rho = +0.73) is a between-family confound that vanishes under control (rho = -0.04). Third, a correct out-of-distribution gate cannot accelerate a loop that leaves its training distribution. We give the break-even deferral fraction in closed form: because the visited states sit 73x off the data
manifold, the gate defers 96.8 to 99.7% of
cells, almost invariant to surrogate quality. Including its own cost, the gated loop is a 0.94 to 0.96x slowdown. We further separate stability from fidelity: a never-crashing gated run accumulates a linear -19.9% density bias over 6000 steps. The error is a directed, ballistically accumulating bias, not the variance-driven divergence the autoregressive literature targets.
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High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Signed Sound-Speed Deformations of BSk24-Anchored Barotropes: Neutron-Star Response
Ioannis Papathanasiou
Background: Localized structure in the
equilibrium squared sound speed can affect
neutron-
star observables, but modifying $dP/d\epsilon$ requires thermodynamically consistent reconstruction and assessment over the complete declared domain. Purpose: We quantify the response to positive and negative localized sound-speed changes around a unified BSk24 baseline while keeping the deformation geometry, admission criteria, reconstruction, and fixed-mass comparison protocol fixed. Method: A Gaussian profile with quintic smootherstep activation is added to $c_{\rm s}^2$. Proposals violating $P>0$ or $0<c_{\rm s}^2\leq1$ anywhere in the retained domain are rejected before reconstruction. Passing cases are reconstructed as effective cold one-fluid barotropes and evolved with the Tolman-Oppenheimer-Volkoff and tidal equations. Results: The $A=0$ case reproduces the undeformed control exactly. A localized change produces a persistent pressure offset, relocates the fixed-mass central state, and yields a mass-dependent, nonlinear, sign-asymmetric response. For $A=-0.8$ and $+0.8$, respectively, $\Delta\Lambda/\Lambda_0=(-46.02\%,+35.33\%)$ at $1.4\,M_\odot$ and $(-63.52\%,+87.17\%)$ at $2.0\,M_\odot$. The reached stiffened feature remains core connected at the reporting endpoints, whereas the softened feature becomes an off-center shell at high mass. Conclusions: These phenomenological BSk24-anchored effective barotropes illustrate how a local sound-speed intervention propagates through thermodynamic reconstruction and stellar structure. They are not BSk24 predictions or evidence for a microscopic composition or phase transition.
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Astrophysics of Galaxies
The star formation history of NGC 2276: Comparison between SED modeling and hydrodynamical simulations
Luka Matijevic, Antonino Marasco, Neven Tomicic et al. (+10 more)
Analyzing environmental effects in
galaxy groups is pivotal for understanding how
galaxies evolve in these moderate-density settings. The degree to which ram pressure versus tidal interactions drive the unusual morphologies and kinematics seen in group
galaxies remains a subject of active debate. This study focuses on the nearby
galaxy NGC 2276, which has the longest
radio continuum tail in galactic groups. It is a member of the NGC 2300 group that possibly experiences both processes, and we aim to determine which has the greatest impact on its overall structure. We combined broadband images with synthetic narrow band filters around emission line maps from integral field spectrograph to construct spatially resolved spectral energy distributions (SED), which we modeled using the BAGPIPES software package to reconstruct kpc-scale
star formation histories. These are compared with those derived from adaptive mesh refinement wind tunnel simulations of an NGC 2276-like system. We show that the spatial distribution of the oldest stellar populations ($>1.1$ Gyr) is highly symmetric compared to the youngest ones. This is the most compelling evidence so far pointing towards ram pressure being the only morphological disturber of this system, as it primarily affects the gaseous component. Simulated data show similar results, with older stellar populations being more symmetric. Our RPS-only model showed no significant differences in the morphology of the stellar populations compared to the RPS+tidal model with initial separation of 50 kpc.
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All authors Luka Matijevic, Antonino Marasco, Neven Tomicic, Rory Smith, Peter Jonathan Watson, Alessandro Ignesti, Ian Roberts, Paul Sell, Augusto Eduardo Lassen, Anna Wolter, Konstantina Anastasopoulou, Andreas Zezas, Panagiotis Kotoulas
High Energy Astrophysical Phenomena
Extensive Air Showers Parameters Estimation Using Machine Learning Techniques with Simulations of the FAST Telescope
Jiří Kvita, Monika Machalová, Radek Přívara et al. (+2 more)
We present the capabilities of the Fluorescence detector Array of Single-pixel
Telescopes (FAST) observatory in the single
telescope configuration as an important step towards the possible future large-field observatory for detecting ultra-high-energy
cosmic rays. Reconstruction of main shower physics parameters are explored on noise-free simulated events using machine learning techniques in the challenging domain of a low-intensity transient signal. We find a very good correlation between the true and reconstructed energy of the shower even with the information from just the four photomultipliers of the single FAST
telescope, and a reduced performance for the maximum of the shower development Xmax, using various architectures of artificial deep and convolutional neural networks, with a comparison to a
benchmark gradient boost regression model. The resolution in the energy is found at the sub-percent level, while in Xmax it is~$5\%$. The relative difference between predicted and true values is under one percent for energy, while for Xmax it ranges from $-8\%$ to $+17\%$, which can be attributed to the limited information from the single FAST
telescope configuration. The results constitute an important capabilities verification and a lesson learned with implications for established FAST prototypes as well as for more complex configurations of the FAST observatory under construction.
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All authors Jiří Kvita, Monika Machalová, Radek Přívara, Rostislav Vodák, Jan Tomeček
Solar and Stellar Astrophysics
Six new doubly eclipsing quadruples in a 2+2 architecture
P. Zasche, H. Kucakova, J. Kara et al. (+5 more)
The study presents a confirmation of six quadruples with two sets of eclipses that have the 2+2 architecture. These so-called doubly eclipsing systems still present a quite rare group of
stars. We collected all available photometric data and carried out a detailed analysis of them. In addition to the precise TESS photometry used to model the light curves for both inner eclipsing binaries, photometric survey data were also used, and more than 100 nights of our own dedicated observations were carried out. These were mainly used for the detection of the long-term
evolution of orbital periods. Thanks to these data, we were able to derive the mutual orbits of the inner doubles via eclipse timing variations. The systems studied are: CzeV1254 (periods 0.715348 d + 0.362593 d, mutual period 15.6 yr); ASASSN-V J070838.27-171952.9 (4.300490 d + 3.767235 d, 4 yr); ASASSN-V J091951.17-593306.9 (2.668674 d + 14.342218 d, 0.95 yr); WISE J100820.07-731554.0 (0.368315 d + 7.945339 d, 3.8 yr); ASASSN-V J143536.01-721459.4 (7.353842 d + 6.368567 d, 27.4 yr); and Corot 310284765 (1.875418 d + 2.371126 d, 22.6 yr). Some of the binaries show significantly eccentric orbits. We also estimated their apsidal motion periods. With our six new systems, the number of confirmed orbits of 2+2 quadruples has been increased to 64 in total.
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All authors P. Zasche, H. Kucakova, J. Kara, J. Merc, Z. Henzl, M. Masek, L. Cervinka, V. Dienstbier
Earth and Planetary Astrophysics
Korean Space Collision Environment Assessment Framework Based on 3D-Cell Model
Jaewoo Kim, Minchan Song, Jinsung Lee et al. (+6 more)
Space situational awareness (SSA) requires purpose-matched models across spatial, temporal, and fidelity scales. Building on our previously reported three-dimensional (3D)
cell formulation and implementation, this study establishes a reproducible, resolution-aware, catalog-conditioned framework for macroscopic assessment of the low Earth orbit (LEO) collision environment. The framework maps supplied catalog or scenario populations to time-averaged spatial density and target-specific impact metrics while retaining individual-object information. Using a 2025 Space-Track snapshot, we evaluate radial, declination, and right-ascension resolution sensitivity and computational performance for six targets, including two Korean space assets. Normalized expected impact counts range from 0.615 to 1.599 and vary nonmonotonically; for a synthetic 500-km circular target, the result at a 0.25-km radial width is 38.5% below the 10-km reference. Runtime and
memory show direction-dependent trade-offs. Ten annual snapshots show catalog growth from 15,723 objects in 2016 to 28,540 in 2025 and a 7.86-fold increase in the 500-km target metric, driven primarily by Starlink, other payloads, and unknown/TBA records. In a conditional stress test of the proposed 998,240-satellite SpaceX Orbital Data Center population, exact annual probabilities of at least one impact reach $3.75\times10^{-3}$ and $1.48\times10^{-3}$ for the 700-km and 1,000-km targets. The framework provides a reproducible, resolution-aware basis for catalog-conditioned environment monitoring, comparative scenario assessment, and prioritization of cases for higher-fidelity follow-up analysis.
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All authors Jaewoo Kim, Minchan Song, Jinsung Lee, Jiwoong Yu, Hosik Kam, Jung Hyun Jo, Eun-Jung Choi, Jin Choi, Jaemyung Ahn
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Impact of Bubble Nucleation History and Friction on Primordial Black Hole Formation
Tathagata Ghosh, Kousik Loho and Sudip Manna
Cosmological first-order phase transitions (FOPTs) in the early Universe are an exciting prediction of many beyond the Standard Model scenarios. Owing to the
stochastic nature of bubble nucleation, some causal patches may remain trapped in the false
vacuum long after the surrounding regions have completed the transition and started to
redshift. Under suitable conditions, these delayed patches can become sufficiently overdense to collapse into primordial black holes (PBHs). One therefore expects characteristic parameters, such as the PBH mass and PBH formation time to be sensitive to the underlying phase-transition dynamics. Here, we adopt a model-independent framework with a fixed mean bubble separation scale ($R_*$) to directly compare the impact of exponential and Gaussian nucleation profiles on PBH formation. We further incorporate the effects of friction on the bubble walls arising from interactions with the surrounding
plasma. We find that friction significantly modifies the bubble dynamics, leading to significant changes in the PBH mass and formation time for both nucleation histories. Moreover, the
stochastic gravitational-wave spectrum generated by the FOPT can provide a complementary probe of the underlying dynamics, allowing the effects of friction on the bubble wall
evolution to be distinguished from the frictionless case.
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Astrophysics of Galaxies
ASKAP discovery of a pair of large radio bubbles: on the origin of odd radio circles
Renzhi Su, Minfeng Gu, Hengxiao Guo et al. (+9 more)
We report the serendipitous discovery of a large, low-surface-brightness
radio bubble in 944 MHz continuum data from the ASKAP Evolutionary Map of the Universe (EMU) survey. The structure, centred on the elliptical
galaxy LEDA 217397 at a
redshift of $z=0.040$, spans $\sim$8.4 arcmin, corresponding to a projected diameter of $\sim$399 kpc, and consists of two partly overlapping shells both with radii of $\sim$114 kpc. The integrated flux density of the bubble is $56.8\pm2.9$ mJy at 944 MHz, implying a rest-frame 1.4 GHz luminosity of $\sim$ $1.4\times10^{23}$ W Hz$^{-1}$. Combining the EMU measurement with MWA GLEAM-X data at 88–185 MHz, we derive a steep integrated spectral index of $\alpha=-1.04\pm0.04$, and a two-frequency spectral-index map suggesting a possible exterior flattening. Spectral Energy Distribution (SED) fitting indicates a massive ($\log M_{\ast}/M\odot = 10.97\pm0.09$), quiescent (SFR=$0.025\pm0.083\,M\odot$ yr$^{-1}$) early-type host with no mid-infrared AGN signature and no overdense environment. We compare the bubble with odd
radio circles (ORCs) and large
radio shells, and discuss three scenarios for its origin: a starburst-driven wind, a merger-driven shock, and AGN jet-inflated bubbles. The starburst wind is disfavoured on energetic grounds ($\gtrsim$$10^{59}$ erg required versus $\sim$$10^{8}$ yr electron lifetimes), and neither a
halo-scale merger shock nor a spherical nuclear blast wave can explain the unusually regular, double-shell geometry; a bipolar nuclear outburst – a relic AGN jet episode, possibly triggered by a supermassive-black-hole merger – provides the most natural explanation, with later shocks possibly re-energising the
plasma. Deeper broad-band
radio, polarimetric, spectroscopic and X-ray observations are needed to confirm its nature.
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All authors Renzhi Su, Minfeng Gu, Hengxiao Guo, Neelesh Amrutha, Liang Cheng, Fangzheng Shi, Wenwen Zuo, Ruiyu Zhang, Guobin Mou, Fulai Guo, Wenke Ren, Xuecheng Zheng
Instrumentation and Methods for Astrophysics · Cross-listed from cs.LG
Neural Operator based Multi-Field Reconstruction of Inner Solar Boundary State
Vignesh Kumar Pandian Sathia, Reza Mansouri, Dustin J. Kempton et al. (+2 more)
The Solar wind is a continuous flow of charged particles emanating from the solar surface and governed by complex, interacting magnetohydrodynamic processes. Accurate specification of inner-boundary conditions is essential for heliospheric modeling and solar-wind prediction. In many practical applications, only a subset of interacting multi-field variables is directly available, but for a comprehensive view of solar wind prediction and downstream magnetohydrodynamic simulations, a more complete boundary state is required. In this work, we study the problem of learning the multi-field multi-scale solar magnetohydrodynamic state at 30 solar radii ($R_\odot$) using operator learning. Specifically, given the radial velocity and radial
magnetic field, we aim to reconstruct the non-radial velocity and
magnetic field components, radial and non-radial current density, thermodynamic density, and pressure components. This mapping is highly nonlinear, spatially coupled, and multi-scale, making it a challenging task for data-driven scientific machine learning. To address this problem, we employ a Local Neural Operator (LocalNO) that learns mappings between input and output function spaces while retaining locality and resolution-awareness. Unlike conventional regression models and autoencoder models, neural operators are better suited for learning structured field-to-field transformations arising from physical systems. The resulting predictions along with inputs are intended to serve as boundary condition variables for future inner-heliospheric modeling pipelines.
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All authors Vignesh Kumar Pandian Sathia, Reza Mansouri, Dustin J. Kempton, Pete Riley, Rafal A. Angryk
Earth and Planetary Astrophysics
Thermochemical constraints on a primordial-origin of gas-rich debris disks
H. Mitani, W. Ooyama, R. Nakatani et al. (+2 more)
Recent observations have revealed gas-rich debris disks around intermediate-mass
stars at ages of tens of Myr. The origin of this gas remains unclear: it may be primordial, retained from the protoplanetary phase, or secondary, released from volatile-rich solids. Secondary-origin models reproduce CO emission but often overpredict neutral carbon. Recent observations and disk-
evolution models suggest that primordial gas may survive longer than previously assumed, motivating thermochemical tests of the primordial-remnant scenario. We test the previously unexplored possibility that primordial-origin disks satisfy the observational constraints on gas-rich debris disks. Specifically, we determine under what conditions a disk around a $2\,M_{\odot}$
star reproduces substantial CO, low CI/CO ratios, and weak HCO+ emission consistent with current non-detections. We post-processed 20-40 Myr structures from 1D disk-
evolution models with Cloudy, varying irradiation geometry, dust-to-gas mass ratio (DTG), and
cosmic-ray ionisation rate. In the dust-poor models (DTG $=10^{-4}$), CO remains optically thick around $R\sim100$~au. The models yield low disk-integrated CI/CO mass ratios. Our model produces CO radial intensities of the observed order of magnitude, but its CI-emitting region is more extended than observed. The standard CR model overproduces HCO+, whereas the weak CR model brings its predicted luminosity within current observational limits. These results demonstrate that a primordial origin remains chemically viable for CO-rich debris disks. The main remaining tension is the excessive radial extent of the CI emission, although it may reflect our simplified modelling. Further testing of the primordial-origin scenario will require multidimensional, self-consistent modelling, spatially resolved CI observations, and deeper searches for HCO+.
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All authors H. Mitani, W. Ooyama, R. Nakatani, R. Kuiper, T. Hosokawa
High Energy Astrophysical Phenomena
A Two-month, Galaxy-targeted NIR Follow-up of the Sub-solar-mass Gravitational Wave Candidate S251112cm: Probing Electromagnetic Counterpart Scenarios
Gregory S. H. Paek, Felipe Olivares E. and Willem B. Hoogendam
S251112cm is a nearby ($93 \pm 27$~Mpc) compact-binary merger candidate with a high inferred probability that at least one component is below $1\,M_\odot$. This event provides a rare test case for electromagnetic follow-up of a theoretically predicted but unconfirmed sub-solar-mass merger candidate. Motivated by scenarios predicting NIR-bright emission over weeks to months, we carried out a deep,
galaxy-targeted UKIRT $J$-band campaign over approximately two months, prioritizing host candidates by a ranking that combines the three-dimensional localization probability with WISE W1 luminosity as a stellar-mass proxy. Of $\sim9000$ candidate hosts, we monitored 59, corresponding to 7.7% of the cumulative weighted host prior. Difference imaging reveals no convincing transient down to typical depths of $J\sim22$–23~mag (AB). At this distance, both a Type~Ic-BL
supernova template and an AT\,2017gfo-like KN template—including time-shifted variants up to $\Delta t \sim 60$~days—would have remained above our median depth for multiple epochs within the monitored hosts. Comparison with a canonical KN model grid, summarized through conditional weighted consistent-fraction maps, shows that bright configurations with high dynamical and wind-ejecta masses are strongly disfavored, while less luminous configurations remain largely permissible. While these constraints are host-limited and do not constitute an event-wide exclusion, this campaign provides the first empirical case study of long-baseline, deep NIR follow-up for a sub-solar-mass merger GW class and demonstrates a host-weighted framework applicable to future
galaxy-targeted campaigns.
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High Energy Astrophysical Phenomena
Timing, Polarization, and Single-Pulse Properties of Long-Period FAST Pulsars
Habtamu Menberu Tedila, Shijun Dang, Di Li et al. (+5 more)
We present phase-connected timing and polarization measurements for two long-period FAST-CRAFTS
pulsars, PSRs J0000+6252 and J2131+3642, and extend single-pulse emission-state analysis to a five-source sample including PSRs J1903+1407, J1502+4653, and J2112+4058. FAST L-band timing baselines span 414 to 511 days; the two
pulsars have
spin periods of 1.11 to 1.55 s, period derivatives of $(3.99$ to $4.06)\times10^{-15}~{\rm s~s^{-1}}$, characteristic ages of 4.34 to 6.16 Myr, surface
magnetic fields of $(2.15$ to $2.52)\times10^{12}$ G, and
spin-down luminosities of $(4.21\times10^{31}$ to $1.16\times10^{32})~{\rm erg~s^{-1}}$. Their rotation measures are $70.2\pm26.7$ and $-44.6\pm7.6~{\rm rad~m^{-2}}$, with linear polarization fractions of 17.6% to 27.2%. PSR J2131+3642 shows a short monotonic PA segment permitting a formal rotating-vector-model fit, though limited longitude coverage leaves the
geometric parameters poorly constrained; PSR J0000+6252 has too few PA points for such a fit. Gaussian mixture modeling (GMM) of single-pulse energy distributions identifies null, weak, and burst components in PSRs J0000+6252, J1903+1407, J1502+4653, and J2112+4058, while J2131+3642 shows only weak and burst states. We also identify bright single pulses (peak intensity $\geq10\times$ the integrated average profile): 42 in J0000+6252, four each in J1903+1407 and J2112+4058, and none in J2131+3642 or J1502+4653. These bright pulses occur within the main emission window with no evidence of periodic recurrence, consistent with sporadic enhancements of the normal
radio-emission beam. For J2112+4058, we measure a scattering timescale $\tau_{\rm sc}=5.84\pm0.18$ ms at $\nu_{\rm ref}=1.25$ GHz. Together, these results highlight the diversity of magnetospheric variability among slowly rotating
neutron stars.
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All authors Habtamu Menberu Tedila, Shijun Dang, Di Li, Pei Wang, Jianping Yuan, Rai Yuen, Na Wang, Shakhboz Khasanov
High Energy Astrophysical Phenomena
Tidal disruption of stellar binaries as a pathway to exotic transients
Mauricio González-Servín, Emilio Tejeda, Susana Lizano et al. (+2 more)
Tidal disruption event (TDE) progenitors are commonly modelled as single
stars on parabolic orbits around a supermassive black hole (SMBH), yet observations reveal a richer diversity of dynamical pathways. We show that tidal separation of stellar binaries by a $10^6\,M_\odot$ SMBH provides a natural mechanism for producing eccentric TDEs. Using restricted three-body and SPH simulations, we model a solar-like
star (SLS)–white dwarf (WD) binary on a parabolic orbit. The binary orbital phase governs the outcome: one component is captured onto a tightly bound orbit while the other is ejected as a hypervelocity object, naturally producing TDEs with eccentricities $e \neq 1$. We classify these into Elliptical TDEs (eTDEs) and
Hyperbolic TDEs (hTDEs), occurring with equal probability. For $\sim 88\%$ of orientations the disruption is clean, with no mass accreted by the WD. The remaining $\sim 12\%$, in two narrow phase windows, leaves the WD with a captured debris envelope (WDDE). About a third of that, $\sim 4\%$ of orientations, involves a direct WD–SLS collision near pericenter, with fallback peaking up to five times earlier and twenty times higher than for a single
star; for the innermost $\sim 1.5\%$ the total WDDE mass exceeds $1.4\,M_\odot$, though the degenerate core does not, since the captured material forms a non-degenerate envelope, suggesting outcomes ranging from nova-like events to peculiar red giant-like objects. Depending on the phase, the mechanism may also produce repeating partial TDEs (rTDEs) and quasi-periodic eruptions (QPEs). Binary–SMBH encounters provide a robust channel for generating diverse TDEs with distinct observational signatures.
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All authors Mauricio González-Servín, Emilio Tejeda, Susana Lizano, Luis A. Manzaneda, Raúl Cano-Villegas
High Energy Astrophysical Phenomena
Probing AU-Scale Magnetic-Field Reversals in the Interstellar Medium with Pulsar Scintillation
Jacob Yen, Daniel Baker, Dongzi Li et al. (+1 more)
AU-scale structures in the interstellar medium have become relevant across several areas of astrophysics, from ISM microphysics to
pulsar timing arrays and
cosmic-ray (CR) propagation. Current sheets formed at
magnetic-field reversals have drawn particular
attention because they can deflect the dominant GeV CR population through large angles.
Pulsar scintillation, an outstanding probe of
plasma density, resolves these structures—but not their
magnetic configuration. Conventional Faraday rotation measures (RM) are only marginally sensitive at AU scales and are further compromised by ionospheric systematics. We propose a method that isolates birefringence-induced polarization—the signature of
magnetic reversal—by applying phase
retrieval to polarized data.
Pulsar scintillation further resolves ray paths separated by $\sim 1\,\rm{AU}$, enabling differential RM measurements that suppress the ionospheric common mode while preserving the AU-scale
magnetic signal. We demonstrate the method on an archival observation of PSR B0834+06. Phase
retrieval resolves the 1-ms scattering feature into two branches in Doppler-delay space. Under the corrugated current-sheet interpretation, these branches correspond to ray paths sampling opposite sides of an AU-scale current sheet. We measure a branch-to-branch RM difference of $(-9.3\pm3.2)\times 10^{-3}\text{ rad m}^{-2}$ at 2.9$\sigma$ across a 10-MHz band. The signal is consistent with a field reversal of $|\Delta\langle B_\parallel \rangle| \simeq4.4\pm2.1\,\mu\rm G$, sufficient to sustain a long-lived sheet. With only six independent subbands, we present this as a proof of concept rather than a definitive detection. If it proves scalable, its full implementation could constrain
cosmic-ray transport and inform models of propagation-induced noise in
pulsar timing arrays.
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All authors Jacob Yen, Daniel Baker, Dongzi Li, Ue-Li Pen
Astrophysics of Galaxies
Observational Evidence for the Kinematic Memory of Cosmic Filaments from Satellite Orbital Orientations
Peng Wang, Wei Wang, Wenting Wang et al. (+5 more)
We present an observational study of the kinematic coherence between satellite orbital planes and the
cosmic web. Using the SDSS DR12
galaxy sample combined with the Bisous filament catalogue, we investigate whether the orbital motion of satellites preserves the
memory of filamentary
accretion. For each satellite system, we define a projected orbital-normal vector using
galaxy sky positions and line-of-sight velocity offsets. By measuring the angle $\theta$ between this vector and the local projected filament direction, we detect a distinctive preferred orientation: satellite orbital planes tend to contain or lie parallel to the filament axis. This signal deviates from the isotropic expectation at a high significance level of $12.8\sigma$. The strength of this kinematic connection depend strongly on environment and host properties. The preference for orbital planes to track the filament direction is most pronounced for groups in close distance to the filament spine and for more massive hosts. Conversely, at intermediate distances from the filament and at large group-centric radii, the signal reverses, indicating a tendency for orbital planes to be oriented perpendicular to the filament. Our findings provide direct observational evidence for the two-phase model of filamentary
accretion, where a transition from initial perpendicular collapse toward the filament spine to subsequent parallel streamwise infall into dark matter
haloes governs the orientation of satellite orbital angular momentum and
galaxy spin. The observed transition may further trace the characteristic radial scale of filaments, offering a dynamical perspective on the internal structure and assembly of the
cosmic filament.
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All authors Peng Wang, Wei Wang, Wenting Wang, Min Bao, Xi Kang, Hong Guo, Youcai Zhang, Xiao-xiao Tang
Earth and Planetary Astrophysics
On the formation of retrograde S-type planets in binaries with a polar circumbinary disk
Cheng Chen, Philip J. Armitage, C. J. Nixon et al. (+2 more)
Retrograde S-type
planets have been observed in several binary systems, yet their formation pathway remains poorly understood. With high-resolution hydrodynamic simulations, we demonstrate that a polar circumbinary disk around an eccentric, unequal-mass binary can form and sustain a retrograde mini disk around the primary
star. This provides a direct in-situ formation channel for retrograde S-type
planets. The mini disk forms via a sub-Keplerian
accretion stream that is slightly misaligned from the polar disk. The mini disk initially undergoes von Zeipel-Kozai-Lidov (ZKL) oscillations, driving coupled eccentricity and inclination
evolution. Rather than oscillating indefinitely, the inner mini disk evolves past the critical ZKL inclination, decouples from the outer disk, and settles into a stable retrograde orbit. This
evolution is sensitive to numerical resolution: the retrograde configuration is absent in previous lower-resolution simulations, where the mini disk
accretion timescale is too short to sustain ZKL-driven
evolution. For a higher disk viscosity, the mini disk remains near-polar due to a shorter
accretion timescale. Since protoplanetary disks typically have low viscosity, our results suggest that retrograde S-type
planets can form in-situ from retrograde mini disks around polar circumbinary disks, and their occurrence rate may be higher than currently estimated.
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All authors Cheng Chen, Philip J. Armitage, C. J. Nixon, Stephen H. Lubow, Rebecca G. Martin
Solar and Stellar Astrophysics
Where Do Periodic Density Structures Acquire Coherence? A Low-Coronal Resonator Candidate and a 12-Event STEREO/SECCHI Transfer Test
Olena Podladchikova
Periodic density structures (PDS) are trains of
plasma enhancements carried into the heliosphere, but their repeated timing does not by itself identify where the cadence is set. We test whether PDS selected independently in the outer corona can be traced back to a low-coronal clock, and whether that organization survives through the EUVI–COR1–COR2 observing chain. We analyze 12 STEREO-A/SECCHI events on 2008 January 11–14 along a nonradial path. EUVI 171 A at 1.10–1.20 R_sun shows an unusual concentration of power in the predeclared 80–130 minute band relative to filter-matched red-noise controls, while the ensemble is most strongly organized in upper COR1 at 2.5–3.0 R_sun. These signatures identify a low-coronal modulation candidate and an intermediate-height organization domain, but they do not form a unique phase-preserving clock extending into COR2. Instead, the more persistent observable is spatial order. Events 9 and 12 retain expansion-stable outward ordering. In polar r–theta maps, intersections of oppositely inclined, expansion-aware matched-filter ridge supports form repeated X-/diamond-like patterns. The morphology is compatible with stationary or quasi-stationary shock-
cell processing, although the brightness diagnostics are insufficient to establish a stationary MHD shock branch. The observations therefore favor an intermittent source–gate–transfer picture: a low-coronal cadence may modulate
plasma release, while event-dependent propagation progressively destroys exact phase coherence. The outward ordering of the density structures can survive, providing a more persistent signature of the source-to-wind transfer than phase locking itself.
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