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Physics Astrophysics

astro-ph Watch Astrophysics

Monday 27 October

Earth and Planetary Astrophysics

The influence of a stably stratified layer on the hydromagnetic waves in the Earth's core and their electromagnetic torques

Fleur Seuren, Santiago A. Triana, Jérémy Rekier et al. (+2 more)

Evidence from seismic studies, mineral physics, thermal evolution models and geomagnetic observations is inconclusive about the presence of a stably stratified layer at the top of the Earth's fluid outer core. Such a convectively stable layer could have a strong influence on the internal fluid waves propagating underneath the core-mantle boundary (CMB) that are used to probe the outermost region of the core through the wave interaction with the geomagnetic field and the rotation of the mantle. Here, we numerically investigate the effect of a top stable layer on the outer core fluid waves by calculating the eigenmodes in a neutrally stratified sphere permeated by a magnetic field with and without a top stable layer. We use a numerical model, assuming a flow with an m-fold azimuthal symmetry, that allows for radial motions across the lower boundary of the stable layer and angular momentum exchanges across the CMB through viscous and electromagnetic coupling. On interannual time-scales, we find torsional Alfvén waves that are only marginally affected by weak to moderate stratification strength in the outer layer. At decadal time-scales similarly weak stable layers promote the appearance of waves that propagate primarily within the stable layer itself and resemble Magneto-Archimedes-Coriolis (MAC) waves, even though they interact with the adiabatic fluid core below. These waves can exert viscous and electromagnetic torques on the mantle that are several orders of magnitude larger than those in the neutrally stratified case.
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All authors Fleur Seuren, Santiago A. Triana, Jérémy Rekier, Véronique Dehant, Tim Van Hoolst

High Energy Astrophysical Phenomena

First detection of ultra-high energy emission from gamma-ray binary LS I +61 303

Zhen Cao, F. Aharonian, Y.X. Bai et al. (+324 more)

We report the first detection of gamma-ray emission up to ultra-high-energy (UHE; $>$100 TeV) emission from the prototypical gamma-ray binary system LS I +61 303 using data from the Large High Altitude Air Shower Observatory (LHAASO). It is detected with significances of 9.2$\sigma$ in WCDA (1.4–30.5 TeV) and 6.2$\sigma$ in KM2A (25–267 TeV); in KM2A alone we identify 16 photon-like events above 100 TeV against an estimated 5.1 background events, corresponding to a 3.8$\sigma$ detection. These results provide compelling evidence of extreme particle acceleration in LS I +61 303. Furthermore, we observe orbital modulation at 3.9$\sigma$ confidence level, between 25 and 100 TeV, with a hint that the orbital modulation is energy-dependent. These features can be understood in a composite scenario in which leptonic and hadronic processes jointly contribute.
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All authors Zhen Cao, F. Aharonian, Y.X. Bai, Y.W. Bao, D. Bastieri, X.J. Bi, Y.J. Bi, W. Bian, J. Blunier, A.V. Bukevich, C.M. Cai, Y.Y. Cai, W.Y. Cao, Zhe Cao, J. Chang, J.F. Chang, E.S. Chen, G.H. Chen, H.K. Chen, L.F. Chen, Liang Chen, Long Chen, M.J. Chen, M.L. Chen, Q.H. Chen, S. Chen, S.H. Chen, S.Z. Chen, T.L. Chen, X.B. Chen, X.J. Chen, X.P. Chen, Y. Chen, N. Cheng, Q.Y. Cheng, Y.D. Cheng, M.Y. Cui, S.W. Cui, X.H. Cui, Y.D. Cui, B.Z. Dai, H.L. Dai, Z.G. Dai, Danzengluobu, Y.X. Diao, A.J. Dong, X.Q. Dong, K.K. Duan, J.H. Fan, Y.Z. Fan, J. Fang, J.H. Fang, K. Fang, C.F. Feng, H. Feng, L. Feng, S.H. Feng, X.T. Feng, Y. Feng, Y.L. Feng, S. Gabici, B. Gao, Q. Gao, W. Gao, W.K. Gao, M.M. Ge, T.T. Ge, L.S. Geng, G. Giacinti, G.H. Gong, Q.B. Gou, M.H. Gu, F.L. Guo, J. Guo, K.J. Guo, X.L. Guo, Y.Q. Guo, Y.Y. Guo, R.P. Han, O.A. Hannuksela, M. Hasan, H.H. He, H.N. He, J.Y. He, X.Y. He, Y. He, S. Hernández-Cadena, B.W. Hou, C. Hou, X. Hou, H.B. Hu, S.C. Hu, C. Huang, D.H. Huang, J.J. Huang, X.L. Huang, X.T. Huang, X.Y. Huang, Y. Huang, Y.Y. Huang, A. Inventar, X.L. Ji, H.Y. Jia, K. Jia, H.B. Jiang, K. Jiang, X.W. Jiang, Z.J. Jiang, M. Jin, S. Kaci, M.M. Kang, I. Karpikov, D. Khangulyan, D. Kuleshov, K. Kurinov, Cheng Li, Cong Li, D. Li, F. Li, H.B. Li, H.C. Li, Jian Li, Jie Li, K. Li, L. Li, R.L. Li, S.D. Li, T.Y. Li, W.L. Li, X.R. Li, Y. Li, Zhe Li, Zhuo Li, E.W. Liang, Y.F. Liang, S.J. Lin, B. Liu, C. Liu, D. Liu, D.B. Liu, H. Liu, J. Liu, J.L. Liu, J.R. Liu, M.Y. Liu, R.Y. Liu, S.M. Liu, W. Liu, X. Liu, Y. Liu, Y. Liu, Y.N. Liu, Y.Q. Lou, Q. Luo, Y. Luo, H.K. Lv, B.Q. Ma, L.L. Ma, X.H. Ma, I.O. Maliy, J.R. Mao, Z. Min, W. Mitthumsiri, Y. Mizuno, G.B. Mou, A. Neronov, K.C.Y. Ng, M.Y. Ni, L. Nie, L.J. Ou, Z.W. Ou, P. Pattarakijwanich, Z.Y. Pei, D.Y. Peng, J.C. Qi, M.Y. Qi, J.J. Qin, D. Qu, A. Raza, C.Y. Ren, D. Ruffolo, A. Sáiz, D. Savchenko, D. Semikoz, L. Shao, O. Shchegolev, Y.Z. Shen, X.D. Sheng, Z.D. Shi, F.W. Shu, H.C. Song, Yu.V. Stenkin, Y. Su, D.X. Sun, H. Sun, J.X. Sun, Q.N. Sun, X.N. Sun, Z.B. Sun, N.H. Tabasam, J. Takata, P.H.T. Tam, H.B. Tan, Q.W. Tang, R. Tang, Z.B. Tang, W.W. Tian, C.N. Tong, L.H. Wan, C. Wang, D.H. Wang, G.W. Wang, H.G. Wang, J.C. Wang, K. Wang, Kai Wang, Kai Wang, L.P. Wang, L.Y. Wang, L.Y. Wang, R. Wang, W. Wang, X.G. Wang, X.J. Wang, X.Y. Wang, Y. Wang, Y.D. Wang, Z.H. Wang, Z.X. Wang, Zheng Wang, D.M. Wei, J.J. Wei, Y.J. Wei, T. Wen, S.S. Weng, C.Y. Wu, H.R. Wu, Q.W. Wu, S. Wu, X.F. Wu, Y.S. Wu, S.Q. Xi, J. Xia, J.J. Xia, G.M. Xiang, D.X. Xiao, G. Xiao, Y.F. Xiao, Y.L. Xin, H.D. Xing, Y. Xing, D.R. Xiong, B.N. Xu, C.Y. Xu, D.L. Xu, R.F. Xu, R.X. Xu, S.S. Xu, W.L. Xu, L. Xue, D.H. Yan, T. Yan, C.W. Yang, C.Y. Yang, F.F. Yang, L.L. Yang, M.J. Yang, R.Z. Yang, W.X. Yang, Z.H. Yang, Z.G. Yao, X.A. Ye, L.Q. Yin, N. Yin, X.H. You, Z.Y. You, Q. Yuan, H. Yue, H.D. Zeng, T.X. Zeng, W. Zeng, X.T. Zeng, M. Zha, B.B. Zhang, B.T. Zhang, C. Zhang, H. Zhang, H.M. Zhang, H.Y. Zhang, J.L. Zhang, J.Y. Zhang, Li Zhang, P.F. Zhang, R. Zhang, S.R. Zhang, S.S. Zhang, S.Y. Zhang, W. Zhang, W.Y. Zhang, X. Zhang, X.P. Zhang, Yi Zhang, Yong Zhang, Z.P. Zhang, J. Zhao, L. Zhao, L.Z. Zhao, S.P. Zhao, X.H. Zhao, Z.H. Zhao, F. Zheng, T.C. Zheng, B. Zhou, H. Zhou, J.N. Zhou, M. Zhou, P. Zhou, R. Zhou, X.X. Zhou, X.X. Zhou, B.Y. Zhu, C.G. Zhu, F.R. Zhu, H. Zhu, K.J. Zhu, Y.C. Zou, X. Zuo

Astrophysics of Galaxies

The Cosmic Baryon Cycle in IllustrisTNG: flows of mass, energy, and metals

Yossi Oren, Viraj Pandya, Rachel S. Somerville et al. (+3 more)

We measure and analyze the inflows and outflows of mass, energy, and metals through the interstellar medium (ISM) and circumgalactic medium (CGM) of galaxies in the IllustrisTNG100 simulations. We identify the dominant feedback mechanism in bins of halo virial mass and redshift by computing the integrated energy input from SNe and the “kinetic” and “thermal” mode of AGN feedback. We measure all quantities in a shell at the virial radius (“halo scale”) and one chosen to be approximately at the interface of the CGM and the interstellar medium (ISM; “ISM scale”). We find that galaxies have strong net positive inflows on halo scales, and weaker but still net positive inflows on ISM scales, at $z\gtrsim 2$. At later times, partially due to the onset of kinetic AGN feedback in massive halos, inflows and outflows nearly balance one another, leading to the familiar effects of the slow-down of galaxy growth and the onset of quenching. Halos dominated by SN feedback show only weak evidence of preventative feedback on halo scales, and we see excess ISM scale accretion indicative of rapid gas recycling. Wind mass loadings decrease with increasing halo mass, and with increasing redshift, while energy loadings are nearly independent of both mass and redshift. The detailed catalogs of these mass, metal, and energy inflow and outflow rates on galaxy and halo scales can be used to guide empirical and semi-analytic models, and provide deeper insight into how galaxy growth and quenching is regulated in the IllustrisTNG simulations.
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All authors Yossi Oren, Viraj Pandya, Rachel S. Somerville, Shy Genel, Osase Omoruyi, Amiel Sternberg

Instrumentation and Methods for Astrophysics

The Programmable Liquid-crystal Active Coronagraphic Imager for the 4-m DAG telescope (PLACID) instrument: installation and commissioning update

Jonas G. Kühn, Ruben Tandon, Lucas Marquis et al. (+9 more)

The Programmable Liquid-crystal Active Coronagraphic Imager for the DAG telescope (PLACID) instrument is a novel high-contrast direct imaging facility that was recently installed on the new Turkish 4-m DAG telescope. In brief, PLACID consists in a fore-optics coronagraphic intermediate stage platform, installed in-between the TROIA XAO system and the DIRAC HAWAII-1RG focal-plane array. The PLACID instrument was delivered to ATASAM campus facilities in March of 2024, and transported to summit in October of 2024. In February of 2025, the PLACID optical breadboard was craned to the DAG observatory floor, and successfully installed on the optical table of the diffraction-limited Nasmyth platform of the 4-m telescope. Following the official DAG Acceptance milestone in the spring of 2025, Assembly, Integration and Validation (AIV) activities have started in July of 2025, when PLACID was cabled up with all active components fully interfaced and tested for functional integrity. When on-sky by early 2026, PLACID will be the world's first active coronagraph system, fielding a customized spatial light modulator (SLM) acting as a dynamically programmable focal-plane phase mask (FPM) coronagraph from H- to Ks-band. This will provide a wealth of novel options to observers, among which software-only abilities to change or re-align the FPM pattern in function of observational conditions or science requirements. Future features will include non-common path aberrations (NCPA) self-calibration, angular differential imaging (ADI) coronagraphy for binary or triple stars, as well as coherent differential imaging (CDI). We hereby present the PLACID AIV activities that have taken place over the last twelve months, and the next steps for commissioning the instrument internally, and on-sky later this year.
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All authors Jonas G. Kühn, Ruben Tandon, Lucas Marquis, Liurong Lin, Derya Öztürk Çetni, Iljadin Manurung, Axel Potier, Laurent Jolissaint, Audrey Baur, Daniele Piazza, Mathias Brändli, Martin Rieder

Astrophysics of Galaxies

Alma Luminous Star catalogue IV: A Massive star census in the Magellanic Clouds

J. A. Molina-Calzada and J. Maíz Apellániz

The fourth part of the Alma Luminous Star catalogue (ALS IV) aims to create the most comprehensive sample of massive stars in the Magellanic Clouds (MCs). By combining Gaia DR3 with Simbad and complementing this information with other photometric and spectroscopic catalogues, we select the massive stars in this region. To achieve this, we apply filters in photometry, combining different bands, as well as in variability and spectral types from the literature. With this approach, we will obtain one of the most complete samples of massive stars in the MCs, which can be used both to study the Clouds and the Magellanic Bridge, as well as the massive stars they contain.
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Instrumentation and Methods for Astrophysics · Cross-listed from hep-ex

Charge Trap Analysis in a SENSEI Skipper-CCD: Understanding Low-Energy Backgrounds in Rare-Event Searches

Agustin Brusco, Bruno Sivilotti, Ana M. Botti et al. (+14 more)

Skipper Charge-Coupled Devices (Skipper-CCDs) are ultra-low-threshold detectors capable of detecting energy deposits in silicon at the eV scale. Increasingly used in rare-event searches, one of the major challenges in these experiments is mitigating low-energy backgrounds. In this work, we present results on trap characterization in a silicon Skipper-CCD produced in the same fabrication run as the SENSEI experiment at SNOLAB. Lattice defects contribute to backgrounds in rare-event searches through single-electron charge trapping. To investigate this, we employ the charge-pumping technique at different temperatures to identify dipoles produced by traps in the CCD channel. We fully characterize a fraction of these traps and use this information to extrapolate their contribution to the single-electron background in SENSEI. We find that this subpopulation of traps does not contribute significantly but more work is needed to assess the impact of the traps that can not be characterized.
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All authors Agustin Brusco, Bruno Sivilotti, Ana M. Botti, Brenda Cervantes, Ansh Desai, Rouven Essig, Juan Estrada, Erez Etzion, Guillermo Fernandez Moroni, Stephen E. Holland, Ian Lawson, Steffon Luoma, Santiago E. Perez, Dario Rodrigues, Javier Tiffenberg, Sho Uemura, Yikai Wu

Astrophysics of Galaxies

The First Star-by-star $N$-body/Hydrodynamics Simulation of Our Galaxy Coupling with a Surrogate Model

Keiya Hirashima, Michiko S. Fujii, Takayuki R. Saitoh et al. (+9 more)

A major goal of computational astrophysics is to simulate the Milky Way Galaxy with sufficient resolution down to individual stars. However, the scaling fails due to some small-scale, short-timescale phenomena, such as supernova explosions. We have developed a novel integration scheme of $N$-body/hydrodynamics simulations working with machine learning. This approach bypasses the short timesteps caused by supernova explosions using a surrogate model, thereby improving scalability. With this method, we reached 300 billion particles using 148,900 nodes, equivalent to 7,147,200 CPU cores, breaking through the billion-particle barrier currently faced by state-of-the-art simulations. This resolution allows us to perform the first star-by-star galaxy simulation, which resolves individual stars in the Milky Way Galaxy. The performance scales over $10^4$ CPU cores, an upper limit in the current state-of-the-art simulations using both A64FX and X86-64 processors and NVIDIA CUDA GPUs.
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All authors Keiya Hirashima, Michiko S. Fujii, Takayuki R. Saitoh, Naoto Harada, Kentaro Nomura, Kohji Yoshikawa, Yutaka Hirai, Tetsuro Asano, Kana Moriwaki, Masaki Iwasawa, Takashi Okamoto, Junichiro Makino

Cosmology and Nongalactic Astrophysics

The role of supercluster filaments in shaping galaxy clusters

Raúl Baier-Soto, Yara Jaffé, Alexis Finoguenov et al. (+44 more)

In a hierarchical $\Lambda$CDM Universe, cosmic filaments serve as the primary channels for matter accretion into galaxy clusters, influencing the shape of their dark matter halos. We investigate whether the elongation of galaxy clusters correlates with the orientation of surrounding filaments, providing the first observational test of this relationship in large supercluster regions. We identified and characterized cosmic filaments in two dimensions within the two superclusters that are part of the low-redshift sub-survey of the Chilean Cluster Galaxy Evolution Survey (CHANCES): the Shapley supercluster and the Horologium-Reticulum supercluster. We analyzed the alignment between filament directions – traced by galaxy distributions – and the triaxiality of cluster gravitational potentials – traced by X-ray emission- using publicly available optical and X-ray data. We have found that most (82%) of the X-ray clusters are associated with and interconnected by the optically detected filaments. The clusters-filaments alignment analysis shows that the elongation of most clusters is well aligned with nearby filaments, providing observational confirmation of theoretical predictions, with the alignment progressively reducing at larger cluster-centric distances ($> 1.6 r_{200}$). Overall, our results support the notion that filaments are the main source of galaxy accretion at redshift below 0.1 and additionally provide evidence that matter accretion through filaments shapes the gravitational potential of galaxy clusters. We propose this measurement as a simple observational proxy to determine the direction of accretion in clusters, which is key to understanding both galaxy evolution and the merger history of galaxy clusters.
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All authors Raúl Baier-Soto, Yara Jaffé, Alexis Finoguenov, P. Christopher Haines, Paola Merluzzi, Hugo Méndez-Hernández, Antonela Monachesi, Ulrike Kuchner, Rory Smith, Nicolas Tejos, Cristóbal Sifón, Maria Argudo-Fernández, C.R. Bom, Johan Comparat, Ricardo Demarco, F. Rodrigo Haack, Ivan Lacerna, E.V.R. Lima, Ciria Lima-Dias, Elismar Lösch, C. Mendes de Oliveira, Diego Pallero, Laerte Sodré Jr, S.M. Gabriel Teixeira, O. Alghamdi, F. Almeida-Fernandes, Stefania Barsanti, E. Lawrence Bilton, M. Canducci, Maiara Carvalho, Giuseppe D'Ago, Alexander Fritz, R. Fábio Herpich, E. Ibar, Hyowon Kim, Sebastian Lopez, Alessia Moretti, L.M.I. Nakazono, D.E. Olave-Rojas, G.B. Oliveira Schwarz, Franco Piraino-Cerda, Emanuela Pompei, U. Rescigno, F. Boudewijn Roukema, V.M. Sampaio, P. Tiño, P. Vásquez-Bustos

Solar and Stellar Astrophysics

The AMBRE Project: Line-broadening and stellar rotation of ESO/FEROS archived spectra

F. Bado, P. de Laverny, Z. Kam et al. (+3 more)

Stellar rotation is a fundamental parameter in stellar studies. However, large homogeneous catalogues of rotational velocities derived from high-resolution stellar spectra are still lacking. The main objective of this work is to determine the line-broadening parameter (Vbroad), a proxy for the stellar rotational velocity, in a large sample of FGKM stars based on their ESO/FEROS spectra, previously parameterised by the AMBRE Project. Vbroad was estimated by cross-correlating the FEROS spectra with AMBRE binary masks. This methodology also relies on a specific calibration of a coupling constant between the rotational velocity and the width of the cross-correlation function. This fundamental step was performed by adopting the AMBRE grid of synthetic spectra. The derived Vbroad were then validated using data from the literature, ground-based spectroscopic surveys, and Gaia/RVS. After analysing more than 5,000 FEROS spectra (including repeated spectra for several stars), we obtained the line-broadening coefficients for 2,584 stars covering the FGKM spectral types, any stellar gravity, and metallicities between the metal-poor up to sub-solar regimes. The mean Vbroad relative uncertainty of this sample was found to be smaller than 8%. As expected, most stars were found to be slow rotators (below a few km/s), in particular, cool dwarfs and giants. However, several hot dwarfs and high-luminosity stars with high-Vbroad rates were identified, most of them not previously classified as fast rotators and/or affected by large macro-turbulent effects. The measured rotational broadening values are of high-quality and verified on the basis of literature comparisons. We publicly provide this catalogue of Vbroad parameters, including stellar atmospheric and quality parameters, for the analysed AMBRE/FEROS sources.
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All authors F. Bado, P. de Laverny, Z. Kam, A. Recio-Blanco, P.A. Palicio, J. Koulidiati

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Energy extraction from a rotating black hole via magnetic reconnection: Bumblebee gravity

Ho-Yun YuChih and Ye Shen

Many efforts were made in order to better understand the energy extraction via magnetic reconnection from a rotating black hole, following the work of Comisso and Asenjo in 2021. We also tried to make some progress in our previous works, in which we discussed differences between bulk plasma with different streamlines and also defined the covering factor as an internal property of an accretion system to quantify its capability on extracting energy via magnetic reconnection from its central black hole. In this study, we aim to explore this topic within the framework of a Kerr-Sen-like spacetime induced from Bumblebee gravity, which, among various alternative theories of gravity beyond pure Einstein gravity, stands out as a promising candidate for explaining certain high energy astrophysical phenomena. More specifically, we would like to analyze the influence of the rate of Lorentz symmetry breaking and the Bumblebee charge, the two additional parameters in Bumblebee gravity except for the black hole mass and spin, on the energy extraction via magnetic reconnection. By analyzing the allowed regions for energy extraction and the variations of covering factor, we find that energy extraction becomes more likely to succeed and tends to occur closer to the central region when the spacetime carries bigger rate of Lorentz symmetry breaking and Bumblebee charge. Furthermore, our results indicate that the most favorable spacetime configuration for energy extraction via magnetic reconnection, when the extractable energy of the central black hole is determined, corresponds to the scenario in which the cosmic censorship hypothesis is marginally not violated.
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High Energy Astrophysical Phenomena

Can KM3-230213A be compatible with a cosmogenic origin?

The KM3NeT collaboration

On the 13th February 2023 the KM3NeT/ARCA telescope observed a track-like event compatible with a ultra-high-energy muon with an estimated energy of 120 PeV, produced by a neutrino with an even higher energy, making it the most energetic neutrino event ever detected. The reported equivalent flux suggest the possible existence of a new diffuse component. A diffuse cosmogenic flux is expected to originate from the interactions of ultra-high-energy cosmic rays with ambient photon and matter fields. Here we show that this component can be compatible with the reported flux level only integrating the cosmogenic emission, at least up to redshift ~$z = 6 $ and assuming a subdominant fraction of protons in the ultra-high-energy cosmic-ray flux, thus placing constraints on known cosmic accelerators. These conditions impose constraints on known cosmic accelerators and open a window into an unexplored region of the Universe at this energy scale.
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Earth and Planetary Astrophysics

The effects of stellar activity cycles on planetary atmospheric escape and the HeI 1083nm transit signature

Andrew P. Allan, Aline A. Vidotto, Jorge Sanz-Forcada et al. (+1 more)

The HeI 1083nm transit signature is commonly used in tracing escaping planetary atmospheres. However, it can be affected by stellar activity, complicating detections and interpretations of atmospheric escape. We model how stellar activity cycles affect the atmospheric escape and HeI 1083nm signatures of four types of highly irradiated exoplanets, at 0.025 and 0.05 au, during minimum and maximum cycle phases. We consider two stars, exhibiting different cycle behaviours: the Sun and the more active star iota Hor, for which we reconstruct its spectral energy distributions at minimum and maximum phases using X-ray observations and photospheric models. We show that over a modulated activity cycle, the release of extreme ultraviolet photons, responsible for atmospheric escape, varies substantially more than that of mid-UV photons, capable of photoionising HeI (23S). This leads to consistently stronger helium signatures during maximum phases. We show that planets at the largest orbit are more affected by cycles, showing larger variations in escape rates and absorptions between minimum and maximum. We also confirm the counter-intuitive behaviour that, despite the fall-off in escape rate with orbital distance, the HeI 1083nm absorption is not significantly weaker at further orbits, even strengthening with orbital distance for some iota Hor planets. We partially explain this behaviour with the lower mid-UV fluxes at more distant orbits, leading to less HeI (23S) photoionisations. Finally, we propose that stellar cycles could explain some of the conflicting HeI 1083nm observations of the same planet, with detections more likely during a phase of activity maximum.
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All authors Andrew P. Allan, Aline A. Vidotto, Jorge Sanz-Forcada, Carolina Villarreal D'Angelo

Solar and Stellar Astrophysics

Energetics of star-planet magnetic interactions: Novel insights from 3D modelling

Arghyadeep Paul and Antoine Strugarek

Star-planet magnetic interactions (SPMI) occurring in the sub-Alfvenic regime can, in principle, induce stellar chromospheric hotspots. Currently, estimates of the power generated by SPMI primarily rely on analytical scaling laws that relate stellar and planetary parameters to the interaction energetics. The existing scaling laws published in the literature so far do not agree with each other by at least an order of magnitude. Our aim is to quantify an absolute upper limit on the power that a planet can channel back to its host star during such interactions, which in turn lead to the formation of stellar hotspots. By performing a series of 3D MHD simulations with varied parameters known to influence the energetics of SPMI, we derive a numerically supported scaling law that can be used to reliably estimate the energy channeled from the planet back to the star. Our results suggest that existing analytical scaling laws may not fully capture the power transferred from the planet to the star through SPMI. The scaling law derived from our numerical simulations appears to provide a more comprehensive estimate, reflecting dependencies on common stellar and planetary parameters also considered in earlier models. Moreover, our findings indicate that power generation involves not only the planetary obstacle itself but also the extended magnetic structure of the Alfven wings interacting with the streaming stellar wind. This study suggests that care should be taken when applying analogies directly from jovian sub-Alfvenic interactions to SPMI, as the underlying physical conditions (specifically the value of the Alfvenic Mach number) may not be directly comparable. Our numerically derived scaling law offers a potentially improved approach for estimating SPMI power, capturing some of the interaction's complexities exclusive to SPMI.
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Astrophysics of Galaxies

The spatial distribution of dwarf and giant galaxies in and around Virgo cluster

Nelvy Choque-Challapa, Rory Smith, Iván Lacerna et al. (+2 more)

The Virgo cluster is one of the closest clusters to us where we can further study the evolution of galaxies, with several infalling substructures and several filaments around it have been reported. Therefore, it makes this cluster and its surrounding an interesting place to study the spatial distribution of the population of dwarf and bright giant galaxies. We analyse the dwarf fraction (DF) in different regions of the cluster, inside the virial radius, in its surrounding area, and in the filamentary structure surrounding it using available catalogues with the aim of measuring whether the DF changes in different environments. Although the total dwarf fraction within the cluster is $\sim$ 0.8, significant local variations are measured throughout the cluster; there are regions with a relatively higher concentration of giant or dwarf galaxies. The fact that Virgo is embedded in a rich environment surrounded by several filaments that feed the cluster with new substructures could imply changes in the DF locally. When we analyse the DF variation at further distances from the cluster we observe some regions with few or no giant galaxies at all, with a locally DF ranging from 0.8 - 1.0. Additionally, when comparing the dwarf fraction in different environments, overall, the DF is larger in regions further away from denser regions such as the Virgo cluster and its filamentary structure surrounding it. When comparing the filament and the cluster area, the dwarf fraction is slightly higher in the filaments, but from filament to filament, the DF changes depending on the presence of groups.
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All authors Nelvy Choque-Challapa, Rory Smith, Iván Lacerna, J. Alfonso L. Aguerri, Daniela Palma

Solar and Stellar Astrophysics

Fine details in solar flare ribbons: Statistical insights from observations with the Swedish 1-m Solar Telescope

Jonas Thoen Faber, Reetika Joshi, Luc Rouppe van der Voort et al. (+4 more)

Flare ribbons serve as chromospheric footprints of energy deposition resulting from particle acceleration during magnetic reconnection. Their fine-scale structure provides a valuable tool for probing the dynamics of the flare reconnection process. Our goal is to investigate the fine-scale structure of flare ribbons through multiple observations of flares, utilising data obtained from the Atmospheric Imaging Assembly (AIA) and the Swedish 1-m Solar Telescope (SST). The aligned AIA and SST datasets for the three solar flares were used to examine their overall morphology. The SST datasets were specifically used to identify fine-scale structures within the flare ribbons. For spectroscopic analysis of these fine structures, we applied machine-learning methods (k-means clustering) and Gaussian fitting. Using k-means, we identified elongated features in the flare ribbons, termed as "riblets", which are short-lived and jet-like small-scale structures that extend as plasma columns from the flare ribbons. Riblets are more prominent near the solar limb and represent the ribbon front. Riblet widths are consistent across observations, ranging from 110-310 km (0".15-0".41), while vertical lengths span 620-1220 km (0".83-1".66), with a potential maximum of 2000 km (2".67), after accounting for projection effects. Detailed H-beta spectral analysis reveals that riblets exhibit a single, redshifted emission component, with velocities of 16-21 km s^1, independent of viewing angle. Our high-resolution observations of the three flare ribbons show that they are not continuous structures, but are composed of vertically extended, fine-scale substructures. These irregular features indicate that the reconnection region is not a smooth, laminar current sheet, but rather a fragmented zone filled with magnetic islands, consistent with the theory of patchy reconnection within the coronal current sheet.
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All authors Jonas Thoen Faber, Reetika Joshi, Luc Rouppe van der Voort, Sven Wedemeyer, Eilif Sommer Øyre, Ignasi J. Soler Poquet, Aline Rangøy Brunvoll

Astrophysics of Galaxies

Automated Exploration of Radical-Molecule Chemistry: The Case of Oxirane + CH in the ISM

Moritz Bensberg, Silvia Alessandrini, Mattia Melosso et al. (+2 more)

Quantum chemistry provides accurate and reliable methods to investigate reaction pathways of reactive molecular systems relevant to the interstellar medium. However, the exhaustive exploration of a reactive network is often a daunting task, resulting in unexplored reactive channels that affect kinetic outcomes and branching ratios. Here, an automated workflow for exploring reactive potential energy surfaces (PESs) is employed for the first time to study the oxirane (C$_2$H$_4$O) plus methylidyne ($^.$CH) reaction. The ultimate goal is to comprehensively map its PES and, subsequently, derive rate constants for the most important reaction channels. In addition to its astrochemical relevance, this reaction has been considered because it is a challenging test case, its network being very extended, with 60 exothermic bimolecular products lying below the reactant's energy. Kinetic simulations indicate that the main product of the reaction is the HCO radical plus ethene (C$_2$H$_4$), while formation of s-trans-propenal (acrolein) and 2H-oxene is also possible, but to a lesser extent. Based on the present study and other references in the literature, we suggest that the slightly higher relative abundance of s-trans-propenal compared to methyl ketene in the interstellar medium is a gas-phase kinetic effect, s-trans-propenal being a more easily accessible product on the C$_3$H$_5$O$^.$ PES.
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All authors Moritz Bensberg, Silvia Alessandrini, Mattia Melosso, Cristina Puzzarini, Markus Reiher

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Lensing, not luck! Detection prospects of strongly lensed gravitational waves

A. Barsode, K. N. Maity and P. Ajith

A small fraction of gravitational-wave (GW) signals detected by ground-based observatories will be strongly lensed by intervening galaxies or clusters. This may produce multiple copies of the signals (i.e., lensed images) arriving at different times at the detector. These, if observed, could offer new probes of astrophysics and cosmology. However, identification of lensed image pairs among a large number of unrelated GW events is challenging. Though the number of lensed events increases with improved detector sensitivity, the false alarms increase quadratically faster. While this "lensing or luck" problem would appear to be insurmountable, we show that the expected increase in measurement precision of source parameters will efficiently weed out false alarms. Based on current astrophysical models and anticipated sensitivities, we predict that the first confident detection could occur in the fifth observing run of LIGO, Virgo, and KAGRA. We expect computational costs to be a major hurdle in achieving such a detection, and show that the Posterior Overlap 2.0 method may offer a near-optimal solution to this challenge.
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.ins-det

Characterization of field cage and cathode for low radioactivity operation with the CYGNO experiment

F.D. Amaro, R. Antonietti, E. Baracchini et al. (+48 more)

Dark matter, which is considered to account for approximately the 27% of the Universe's energy-mass content, remains an open issue in modern particle physics along with its composition. The CYGNO Experiment aims to exploit an innovative approach applied to the direct detection search of low energy nuclear recoils possibly induced by cold particle-like dark matter candidates. CYGNO employs a directional detector based on a Time Projection Chamber (TPC) filled with a He:CF$_{4}$ gas mixture and equipped with an optical readout. Currently, the CYGNO Collaboration is constructing the detector demonstrator, CYGNO-04, in Hall F at Laboratori Nazionali del Gran Sasso (LNGS). This 0.4 m$^3$ detector has the goal of proving the scalability of the technology and assessing the physics and radiopurity capabilities. Given the low radioactivity requirements, especially in internal components such as field cage and cathode, the reduction of material while keeping the correct electrical behavior is paramount. In this paper, we present the validation of several internal components, mainly focusing on the field cage material and support structure. The tests included geometrical asymmetries in the electric field response, collection efficiency as well as measurement of known physical quantities. A preferred configuration is found with a structure based on Nylon material which supports a PET or Kapton sheet with copper strips deposited on.
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All authors F.D. Amaro, R. Antonietti, E. Baracchini, L. Benussi, S. Bianco, A. Biondi, C. Capoccia, M. Caponero, L.G.M. de Carvalho, G. Cavoto, I.A. Costa, A. Croce, M. D'Astolfo, G. D'Imperio, E. Danè, G. Dho, E. Di Marco, J.M.F. dos Santos, D. Fiorina, F. Iacoangeli, Z. Islam, E. Kemp, H.P. Lima Jr, G. Maccarrone, R.D.P. Mano, D.J.G. Marques, G. Mazzitelli, A.G. McLean, P. Meloni, A. Messina, C.M.B. Monteiro, R.A. Nobrega, I.F. Pains, E. Paoletti, L. Passamonti, F. Petrucci, S. Piacentini, D. Piccolo, D. Pierluigi, D. Pinci, A. Prajapati, F. Renga, F. Rosatelli, A. Russo, G. Saviano, P.A.O.C. Silva, N.J. Spooner, R. Tesauro, S. Tomassini, S. Torelli, D. Tozzi

Astrophysics of Galaxies

Using Type-II Cepheids as Extragalactic Standard Candles: Distances to M31

V. D. Pipwala, H. N. Lala, B. Lemasle et al. (+3 more)

Several standard candles have been tested and used to measure accurate extragalactic distances over the past decades. There have been discussions regarding the possibility of using Type-II Cepheids (T2Cs) as an alternative tool, but rarely was this ever implemented. The aim of this project is to assert the use of T2Cs as a new avenue for calibrating the extragalactic distance scale, by using M31 as a benchmark galaxy. Since Ordinary Least Squares regression methods are not immune to outliers and offer an incomplete treatment of the uncertainties, we favor a Bayesian robust regression model to compute new Period–Luminosity (PL) and Period–Wesenheit (PW) relations calibrated using $\sim$100 T2Cs, $\sim$1000 fundamental-mode and $\sim$750 first-overtone classical Cepheids (CCs) in the LMC. Using these relations, we employ a classification routine based on Bhattacharyya distances to filter out any contaminants from the M31 sample. We validate our method by verifying that we retrieve an accurate distance for the LMC. We find a distance to M31 of $24.487\pm0.001$ (statistical) $\pm0.052$ (systematic) mag using CCs and of $24.409\pm0.025$ (statistical) $\pm0.156$ (systematic) mag using T2Cs. Both values are in excellent agreement with literature values derived from meta-analyses, from Hubble Space Telescope (HST) observations of CCs, from the Tip of the Red Giant Branch method, and from HST observations of RR Lyrae. In almost all cases, we reach a relative accuracy better than 98%, although the archival ground-based data we use cannot compare with HST photometry. We demonstrate that T2Cs can also be used as accurate tracers for determining extragalactic distances, thereby making them excellent candidates for JWST, LSST, and ELT observations. These stars allow us to probe galaxies deprived of young populations and are beyond the reach of the fainter RR Lyrae.
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All authors V. D. Pipwala, H. N. Lala, B. Lemasle, E. K. Grebel, G. Bono, G. Fiorentino

Instrumentation and Methods for Astrophysics

Development of the Reconstruction Procedure of the Fluorescence detector Array of Single-pixel Telescopes for measuring Ultra-High Energy Cosmic Rays

Fraser Bradfield

The Fluorescence detector Array of Single-pixel Telescopes aims to deploy an array of simplified, autonomous fluorescence telescopes over an area of $\sim60,000$ km$^{2}$ to observe ultra-high energy cosmic rays. The unprecedented size of such an array will enable measurements of cosmic rays with energies above 10$^{20}$ eV with large statistics, providing new insights into UHECR sources. With a single FAST telescope consisting of just four photomultiplier tubes, traditional techniques to reconstruct observed extensive air showers are not applicable. Instead, FAST utilises a top-down approach where simulations are directly compared to data and the best match chosen via a maximum likelihood estimation. This method, known as the "top-down reconstruction (TDR)", requires an accurate "first guess" of the shower parameters to be successful. In this work, improvements to the efficiency and precision of the TDR are made and two different first guess estimation methods are investigated. The combined performance of a machine-learning-based first guess and improved TDR is shown to achieve resolutions in the shower arrival direction, depth of shower maximum and shower energy of $\sim2^\circ$, $\sim30$ g cm$^{-2}$ and $\sim7\%$ respectively for simulated events observed from two or more locations. The improved reconstruction is then applied to data from the current FAST prototype installations at the Pierre Auger Observatory and Telescope Array experiment. Using these results, the first measurements of the UHECR energy spectrum and composition by FAST are presented.
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Solar and Stellar Astrophysics

Fundamental effective temperature measurements for eclipsing binary stars – VI. Improved methodology and application to the circumbinary planet host star BEBOP-3

P. F. L. Maxted, N. J. Miller, T. A. Baycroft et al. (+3 more)

BEBOP-3 is detached eclipsing binary star that shows total eclipses of a faint M~dwarf every 13.2 days by a 9$^{\rm th}$-magnitude F9V star. High precision radial velocity measurements have recently shown that this binary star is orbited by a planet with an orbital period $\approx 550$ days. The extensive spectroscopy used to detect this circumbinary planet has also been used to directly measure the masses of the stars in the eclipsing binary. We have used light curves from the TESS mission combined with these mass measurements to directly measure the following radii and surface gravities for the stars in this system: $R_1 = 1.386 \pm 0.010\,R_{\odot}$, $\log g_1 = 4.190 \pm 0.004$, $R_2 = 0.274 \pm 0.002\,R_{\odot}$, $\log g_2 = 4.979 \pm 0.002$. We describe an improved version of our method to measure the effective temperatures (T$_{\rm eff}$) of stars in binary systems directly from their angular diameters and bolometric fluxes. We measure T$_{\rm eff,1} = 6065{\rm\,K} \pm 44\,{\rm K}$ and T$_{\rm eff,2} = 3191{\rm\,K} \pm 40\,{\rm K}$ for the stars in BEBOP-3 using this method. BEBOP-3 can be added to our growing sample of stars that can be used test the accuracy of spectroscopic and photometric methods to estimate T$_{\rm eff}$ and $\log g$ for solar-type stars.
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All authors P. F. L. Maxted, N. J. Miller, T. A. Baycroft, D. Sebastian, A. H. M. J. Triaud, D. V. Martin

Astrophysics of Galaxies

QUEST (Quasar Unsupervised Encoder and Synthesis Tool): A machine learning framework to generate quasar spectra

F. Guarneri, J. T. Schindler, R. A. Meyer et al. (+5 more)

Quasars at the redshift frontier (z > 7.0) are fundamental probes of black hole (BH) growth and evolution but notoriously difficult to identify. At these redshifts, machine learning-based selection methods have proven to be efficient, but require appropriate training sets to express their full potential. Here, we present QUEST, a Variational Auto-Encoder capable of generating realistic quasar spectra that can be post-processed for generating synthetic photometry and for spectral imputation. We start from the SDSS DR16Q catalogue, pre-process the spectra, and vet the sample to obtain a clean data set. After training the model, we investigate the properties of its latent space to understand whether it has learnt relevant physics. We provide a pipeline to generate photometry from the sampled spectra, compare it with actual quasar photometry, and showcase the capabilities of the model in reconstructing and extending quasar spectra. The trained network faithfully reproduces the input spectrum, both in terms of sample median and variance. By examining the latent space, we find correlations with continuum and bolometric luminosity, BH mass, redshift, continuum slope, and emission line properties. When used to generate photometry, we find results in excellent agreement with the control sample. The model provides satisfactory results in reconstructing emission lines: estimates of the BH mass from the reconstructed spectra are in good agreement with those from the original spectra. Furthermore, when spectra with broad absorption line features are reconstructed, the model successfully interpolates over the absorption systems. Compared with previous work, we find excellent agreement between the spectra sampled from our model and the output of their results. However, QUEST does not require any ad-hoc tuning, and is capable of reproducing the full variety of spectra available in the training set.
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All authors F. Guarneri, J. T. Schindler, R. A. Meyer, D. Yang, J. F. Hennawi, L. Lucie-Smith, S. E. I. Bosman, F. B. Davies

Solar and Stellar Astrophysics

Spinning-down RU Lup. Constraints on the physics of the outflow from high-resolution spectroscopy

A. Armeni, B. Stelzer, A. Frasca et al. (+4 more)

Magnetic winds are a key mechanism for angular momentum removal in young stars. In this work, we aim at characterizing the multi-component outflow of RU Lup. The unprecedented high resolution of the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO) enabled a detailed study of the forbidden emission lines and the blueshifted absorption in the lines of the Na I and Ca II doublets, which we resolved in three discrete absorption components at low, medium, and high velocities. We developed a method that disentangles vertical and toroidal velocities in the absorption components and infers the wind launching radius, magnetic lever arm, and mass-loss rate. We identified a low-velocity broad component in the [O I] 5577 line, consistent with a rotating magnetohydrodynamic disk wind launched near the disk truncation radius. We showed that the discrete absorption components trace spatially and physically distinct regions of the outflow. The medium and low velocity components are launched from the inner disk (< 6.76 stellar radii) with low lever arms indicative of warm, highly mass-loaded streamlines. However, the two components differ mainly in vertical velocity. The low velocity absorption is consistent with an outer absorbing shell, while the medium velocity absorption forms near the disk truncation radius. Its higher vertical velocity is compatible with either a slightly larger lever arm, or additional heating at the base of the flow. For plausible ionization levels in the inner disk, this outflow component removes a substantial fraction of the accretion spin-up torque. In conclusion, our work shows that RU Lup hosts a stratified, rotating, warm disk wind launched across a narrow annulus near the disk truncation radius, which is sufficiently mass-loaded to extract a large amount of the stellar spin-up torque. The observations disfavor an X-wind scenario.
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All authors A. Armeni, B. Stelzer, A. Frasca, C. F. Manara, J. Campbell-White, J. F. Gameiro, M. Gangi

Earth and Planetary Astrophysics

Open-Source High-Fidelity Orbit Estimation for Planetary Science and Space Situational Awareness Using the Tudat Software

Luigi Gisolfi, Dominic Dirkx, Sam Fayolle et al. (+29 more)

The TU Delft Astrodynamics Toolbox (Tudat) is a free open-source software suite for research and education in astrodynamics. Initially focused on numerical simulations of orbital dynamics and state estimation, it enables combining optical and radiometric tracking data from multiple sources to estimate the dynamics and parameters of natural and artificial bodies. Recent developments have added functionality for real tracking data analysis, with applications to planetary missions and Space Situational Awareness (SSA). Tudat currently supports processing of (i) deep-space Doppler and range data from DSN and ESTRACK, (ii) Doppler and VLBI data from the PRIDE experiment, and (iii) optical astrometry from the Minor Planet Center (MPC) and Natural Satellite Data Center (NSDC). Using tracking data from the MRO and GRAIL spacecraft and astrometric data of the asteroid Eros, we present prefit residuals (from SPICE-based observables) and postfit residuals (from fitting data to the Tudat dynamical model). Postfit Doppler residuals reach 1-5 mHz for MRO and GRAIL, orbit differences are a few meters for GRAIL and about one meter for MRO, and MRO range residuals are a few meters. From eight years of Eros astrometry, we obtain an orbit difference from the JPL Horizons solution by several tens of kilometers, consistent with its 3-sigma formal error. Tudat's SSA capability is demonstrated by propagating the orbit of Kosmos 482, a Venus lander launched in 1972 that remained in Earth orbit, over 50 years, including its predicted re-entry on May 10 2025. These examples showcase Tudat's modular, flexible, high-fidelity modeling across diverse orbital regimes within a fully open-source framework. All example code is publicly available, and future Tudat analyses will be published with fully reproducible code, allowing anyone in the community to improve and expand upon our work.
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All authors Luigi Gisolfi, Dominic Dirkx, Sam Fayolle, Valerio Filice, Riva Alkahal, Miguel Avillez, Tristan Dijkstra, Jonas Hener, Lars Hinüber, Marco Langbroek, Nicolò Maistri, Michael Plumaris, Alfonso Sanchez Rodriguez, Giuseppe Cimò, Kevin Cowan, Fabien Dahmani, João Encarnacao, Geoffrey Garrett, Steve Gehly, Xuanyu Hu, Marceau Jeanjean, Antonio López Rivera, Andrea Minervino Amodio, Guifre Molera Calvés, Markus Reichel, Bart Root, Martin Søndergaard, Dominik Stiller, Simon Van Hulle, Gijs Verdoes Kleijn, Rees Williams, Daan Witte

High Energy Astrophysical Phenomena

Recasting and Forecasting Dark Matter Limits Without Raw Data: A Generalized Algorithm for Gamma-Ray Telescopes

Giacomo D'Amico, Michele Doro and Michela De Caria

We present a novel method for both forecasting and recasting upper limits (ULs) on dark matter (DM) annihilation cross sections, $\left< \sigma v \right>^{UL}$, or decay lifetime $\tau^{LL}$ . The forecasting method relies solely on the instrument response functions (IRFs) to predict ULs for a given observational setup, without the need for full analysis pipelines. The recasting procedure uses published ULs to reinterpret constraints for alternative DM models or channels. We demonstrate its utility across a range of canonical annihilation channels, including $b\bar{b}$, $W^+W^-$, $\tau^+\tau^-$, and $\mu^+\mu^-$, and apply it to several major gamma-ray experiments, including MAGIC, Fermi-LAT, and CTAO. Notably, we develop a recasting approach that remains effective even when the IRF is unavailable by extracting generalized IRF-dependent coefficients from benchmark channels. We apply this method to reinterpret ULs derived from standard spectra (e.g., PPPC4DMID) in terms of more recent DM scenarios, including a Higgsino-like model with mixed final states and spectra generated with the CosmiXs model. Extensive Monte Carlo simulations and direct comparison with published results confirm the robustness and accuracy of our method, with discrepancies remaining within statistical uncertainties. The algorithm is generally applicable to any scenario where the expected signal model is parametric, offering a powerful tool for reinterpreting existing gamma-ray limits and efficiently exploring the DM parameter space in current and future indirect detection experiments.
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Solar and Stellar Astrophysics

The Sun as an X-ray star V.: A new method to retrieve coronal filling factors

Wilhelmina Maryann Joseph, Beate Stelzer, Salvatore Orlando et al. (+1 more)

Context. Stellar coronae are unresolved in X-rays, so inferences about their structure rely on spectral analysis. The "Sun-as-an-X-ray-star" (SaXS) approach uses the Sun as a spatially resolved template to interpret stellar spectra, but previous SaXS implementations were indirect and computationally heavy. Aims. We present a new SaXS implementation that converts solar emission measure distributions (EMDs) of distinct coronal region types into XSPEC spectral components and test whether broad-band X-ray spectra alone can recover their filling factors. Methods. We built XSPEC multi-temperature spectral models for four solar region types (background/quiet corona, active regions, cores, and flares) by using EMDs derived from Yohkoh/SXT data and translating each EMD bin into an isothermal apec component. These models were fit (using PyXspec) to two one-hour DAXSS spectra representative of quiescent (2022-06-29) and flaring (2022-04-25) states. Best-fit normalizations were converted into projected areas and filling factors and compared with near-coincident Hinode/XRT full-disk images. Results. Using the Yohkoh/SXT EMDs, the quiescent Sun spectrum is dominated by active region emission (filling factor ~22%), with the background corona poorly constrained. The flaring Sun spectrum is best described by a combination of active regions, cores, and flares with filling factors of ~47.5%, ~4.1%, and ~0.062%, respectively. The dominant components match spatial features seen in Hinode/XRT images. Limitations include the DAXSS low-energy cutoff (~0.7 keV) and the small, non-uniform Yohkoh EMD sample. Conclusions. Our SaXS implementation enables direct retrieval of coronal filling factors from broad-band X-ray spectra and provides a physically motivated alternative to ad hoc few-temperature fits, suitable for stellar X-ray analyses.
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All authors Wilhelmina Maryann Joseph, Beate Stelzer, Salvatore Orlando, Moritz Klawin

Earth and Planetary Astrophysics

The Detectability of Lunar-Origin Asteroids in the LSST Era

Yixuan Wu, Yifei Jiao, Wen-Yue Dai et al. (+5 more)

While most near-Earth asteroids (NEAs) are thought to originate from the main belt, recent discoveries have suggested the existence of a lunar-derived NEA population, such as the asteroids Kamo'oalewa and 2024 PT5. These objects may hold key clues to the dynamical evolution of NEAs and the recent impact history of the Earth-Moon system. However, the population, distribution, and dynamical characteristics of these Lunar-Origin Asteroids (LOAs) remain poorly constrained. By combining the lunar ejecta production with N-body orbital simulations of the ejecta, we investigate their orbital evolution in the past millions of years and the current LOA population, revealing their significant potential for detection by future surveys. Specifically for the Vera C. Rubin Observatory's upcoming Legacy Survey of Space and Time (LSST), we predict an average detection rate of about 6 LOAs (with D > 5 m) per year. Additionally, we find that the LOAs tend to approach from sunward and anti-sunward directions, with encounter velocities significantly lower than those of typical NEAs. These findings offer valuable insights in guiding targeted ground-based surveys and planetary defense efforts for LOAs in the future.
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All authors Yixuan Wu, Yifei Jiao, Wen-Yue Dai, Yukun Huang, Zihan Liu, Bin Cheng, Hexi Baoyin, Junfeng Li

High Energy Astrophysical Phenomena

A volcanic chronosequence as a time-resolved paleo-detector array to study the cosmic-ray flux in the Late Pleistocene and Holocene

Claudio Galelli, Lorenzo Caccianiga, Lorenzo Apollonio et al. (+2 more)

We present a phenomenological study demonstrating the feasibility of using olivine xenoliths from the Chaîne des Puys as a time-resolved paleo-detector array to probe the cosmic-ray flux over the last 40,000 years. This volcanic region provides a unique chronosequence of samples brought to the surface by well-dated eruptions. By modeling the expected density of nuclear recoil tracks induced by cosmic-ray muons in olivine, we show that the signal is detectable and above backgrounds from natural radioactivity. We demonstrate that by analyzing samples with different exposure ages, it is possible to construct a time-differential measurement of the cosmic-ray flux. This method shows sensitivity to historical variations, such as the enhanced flux expected during the Laschamp geomagnetic excursion ($\sim$41~kyr) and the potential contribution from nearby supernovae, for which we use the Antlia supernova remnant precursor as a benchmark. This work establishes a new application of the paleo-detector technique for long-scale time-domain high-energy astrophysics and provides the direct scientific motivation for experimental efforts to measure these track records.
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All authors Claudio Galelli, Lorenzo Caccianiga, Lorenzo Apollonio, Paolo Magnani, Vincent Breton

High Energy Astrophysical Phenomena

Luminosity Functions and Detectability of Binary Neutron Star Merger-nova Signals with Various Merger Remnants

Zhiwei Chen, Youjun Lu, Hao Ma et al. (+1 more)

With the rapid advancements in next-generation ground-based gravitational wave (GW) detectors, it is anticipated that $10^3$-$10^5$ binary neutron star (BNS) mergers per year will be detected, with a significant fraction accompanied by observable merger-nova signals through future sky surveys. Merger-novae are typically powered by the radioactive decay of heavy elements synthesized via the r-process. If the post-merger remnant is a long-lived rapid-rotating neutron star, the merger-nova can be significantly enhanced due to strong magnetized winds. In this paper, we generate mock BNS merger samples using binary population synthesis model and classify their post-merger remnants–black hole (BH) and magnetar, (i.e., long-lived supramassive NS and stable NS), based on results from numerical simulations. We then construct merger-nova radiation models to estimate their luminosity function. We find that the luminosity function may exhibit a distinctive triple-peak structure, with the relative positions and heights of these peaks depending on the equation of state (EOS) of the BNS. Furthermore, we estimate the average Target-of-Opportunity (ToO) detection efficiency $\langle f_{\rm eff} \rangle$ with the Chinese Space Station Telescope (CSST) and find that due to possible enhanced luminosity, the largest source redshift with $\langle f_{\rm eff} \rangle>0.1$ can be enlarged from $z_{\rm s}\sim 0.5$ to $z_{\rm s}\sim 1-1.5$. Besides, we also generate the detectable mass spectrum for merger-novae by $\langle f_{\rm eff}\rangle$, which may provide insights to the ToO searching strategy.
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All authors Zhiwei Chen, Youjun Lu, Hao Ma, Qingbo Chu

High Energy Astrophysical Phenomena

Revisiting Very High Energy Gamma-Ray Absorption in Cosmic Propagation under the Combined Effects of Axion-Like Particles and Lorentz Invariance Violation

Longhua Qin, Jiancheng Wang, Chuyuan Yang et al. (+9 more)

Very-high-energy (VHE; $E \gtrsim 100$ GeV) gamma rays are expected to experience strong attenuation during cosmological propagation due to electron-positron pair production on the extragalactic background light (EBL). Recent observations of GRB 221009A (z = 0.151), including photons up to $\sim 18$ detected by LHAASO and a $\sim 300\ \mathrm{TeV}$ event reported by Carpet-3, suggest a higher-than-expected transparency of the Universe at extreme energies. These observations cannot be explained by standard EBL absorption alone; moreover, neither Lorentz invariance violation (LIV) nor photon-axion-like particle (ALP) oscillations, when considered in isolation, appear sufficient to account for the survival of such photons over cosmological distances. In this work, we propose a joint propagation scenario that incorporates photon-ALP mixing in astrophysical magnetic fields together with subluminal quadratic LIV corrections to the $\gamma\gamma$ pair-production threshold. Applying this framework to the broadband gamma-ray spectrum of GRB 221009A, we show that ALPs with coupling ($g_{a\gamma} = 1.685 \times 10^{-10}\mathrm{GeV}^{-1}$ ) and mass ($m_a = 9.545 \times 10^{-8}\mathrm{eV}$), combined with a quadratic LIV energy scale ($E_{\rm LIV,2} = 1.30 \times 10^{-7} E_{\rm Pl}$) adopted from the literature, can significantly enhance the photon survival probability in the energy range (10\text{-}300) TeV. The resulting enhancement exceeds that obtained from either ALP mixing or LIV effects alone. These results indicate that a combined ALP-LIV scenario may provide a viable interpretation of the extreme-energy gamma-ray observations of GRB 221009A and highlight the potential of VHE gamma-ray measurements as probes of physics beyond the Standard Model.
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All authors Longhua Qin, Jiancheng Wang, Chuyuan Yang, Huaizhen Li, Quangui Gao, Ju Ma, Ao Wang, Weiwei Na, Ming Zhou, Zunli Yuan, Chunxia Gu, Guangbo Long