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Physics Astrophysics

astro-ph Watch Astrophysics

Wednesday 10 December

Cosmology and Nongalactic Astrophysics

Euclid preparation. Review of forecast constraints on dark energy and modified gravity

Euclid Collaboration: N. Frusciante, M. Martinelli, L. Lombriser et al. (+325 more)

The Euclid mission has been designed to provide, as one of its main deliverables, information on the nature of the gravitational interaction, which determines the expansion of the Universe and the formation of structures. Thus, Euclid has the potential to test deviations from general relativity that will allow us to shed light on long-lasting problems in the standard cosmological model, $\Lambda$CDM. Euclid will mainly do this by using two complementary probes: weak gravitational lensing and galaxy clustering. In this paper we review pre-launch Euclid analyses for dark energy and modified gravity. These include forecast constraints with future Euclid data on cosmological parameters for different cosmological models, such as a time-varying dark energy component, phenomenological modifications of the perturbation sector and specific modified gravity models, with further extensions that include neutrino physics and the coupling to the electromagnetic sector through the fine-structure constant. We review the study of the impact of nonlinear clustering methods on beyond-$\Lambda$CDM constraints with Euclid. This is of fundamental importance to efficiently predict the large-scale clustering of matter and dark matter halos, given that we will have access to a wealth of information on scales beyond the linear regime. We inspect the extension of theoretical predictions for observable quantities in alternative cosmologies to $\Lambda$CDM at fully nonlinear scales by means of $N$-body simulations. We discuss the impact of relativistic corrections in extended cosmological models. Overall, this review highlights the significant potential of the Euclid mission to tightly constrain parameters of dark energy and modified gravity models, or perhaps to detect possible signatures of a $\Lambda$CDM failure.
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All authors Euclid Collaboration: N. Frusciante, M. Martinelli, L. Lombriser, A. Silvestri, M. Archidiacono, M. Baldi, M. Ballardini, N. Bartolo, E. Bellini, G. Benevento, D. Bertacca, C. Bonvin, B. Bose, P. Brax, V. F. Cardone, S. Casas, M. Y. Elkhashab, P. G. Ferreira, F. Finelli, F. Hassani, S. Ilić, K. Koyama, M. Kunz, F. Lepori, J. Lesgourgues, C. J. A. P. Martins, D. F. Mota, J. Noller, F. Pace, D. Paoletti, G. Parimbelli, V. Pettorino, Z. Sakr, S. Srinivasan, E. M. Teixeira, I. Tutusaus, P. Valageas, H.-A. Winther, J. Adamek, I. S. Albuquerque, L. Atayde, M.-A. Breton, S. Camera, C. Carbone, E. Carella, P. Carrilho, F. J. Castander, R. Durrer, B. Fiorini, P. Fosalba, M. Marinucci, C. Moretti, M. Pietroni, L. Piga, G. Rácz, F. Sorrenti, F. Vernizzi, C. Viglione, L. Amendola, S. Andreon, C. Baccigalupi, S. Bardelli, R. Bender, A. Biviano, D. Bonino, E. Branchini, M. Brescia, J. Brinchmann, A. Caillat, G. Cañas-Herrera, V. Capobianco, J. Carretero, M. Castellano, G. Castignani, S. Cavuoti, K. C. Chambers, A. Cimatti, C. Colodro-Conde, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, F. Courbin, H. M. Courtois, M. Cropper, A. Da Silva, H. Degaudenzi, G. De Lucia, A. M. Di Giorgio, J. Dinis, H. Dole, F. Dubath, X. Dupac, S. Dusini, A. Ealet, S. Escoffier, M. Farina, S. Farrens, F. Faustini, S. Ferriol, S. Fotopoulou, M. Frailis, E. Franceschi, M. Fumana, S. Galeotta, B. Gillis, C. Giocoli, J. Gracia-Carpio, A. Grazian, F. Grupp, L. Guzzo, S. V. H. Haugan, H. Hoekstra, W. Holmes, I. Hook, F. Hormuth, A. Hornstrup, P. Hudelot, K. Jahnke, M. Jhabvala, B. Joachimi, E. Keihänen, S. Kermiche, A. Kiessling, B. Kubik, H. Kurki-Suonio, O. Lahav, A. M. C. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, D. Maino, E. Maiorano, O. Mansutti, O. Marggraf, K. Markovic, N. Martinet, F. Marulli, R. Massey, S. Maurogordato, E. Medinaceli, S. Mei, M. Melchior, Y. Mellier, M. Meneghetti, E. Merlin, G. Meylan, A. Mora, M. Moresco, L. Moscardini, C. Neissner, R. C. Nichol, S.-M. Niemi, J. W. Nightingale, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, W. J. Percival, S. Pires, G. Polenta, M. Poncet, L. A. Popa, L. Pozzetti, F. Raison, R. Rebolo, A. Renzi, J. Rhodes, G. Riccio, E. Romelli, M. Roncarelli, R. Saglia, A. G. Sánchez, D. Sapone, B. Sartoris, R. Scaramella, J. A. Schewtschenko, M. Schirmer, T. Schrabback, A. Secroun, E. Sefusatti, G. Seidel, M. Seiffert, S. Serrano, C. Sirignano, G. Sirri, A. Spurio Mancini, L. Stanco, J. Steinwagner, P. Tallada-Crespí, D. Tavagnacco, A. N. Taylor, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, E. A. Valentijn, L. Valenziano, J. Valiviita, T. Vassallo, G. Verdoes Kleijn, A. Veropalumbo, Y. Wang, J. Weller, A. Zacchei, G. Zamorani, E. Zucca, E. Bozzo, C. Burigana, M. Calabrese, D. Di Ferdinando, J. A. Escartin Vigo, G. Fabbian, M. Maturi, N. Mauri, A. Pezzotta, M. Pöntinen, C. Porciani, V. Scottez, M. Tenti, M. Viel, M. Wiesmann, Y. Akrami, V. Allevato, S. Anselmi, F. Atrio-Barandela, A. Balaguera-Antolinez, A. Blanchard, L. Blot, H. Böhringer, S. Borgani, M. L. Brown, S. Bruton, R. Cabanac, A. Calabro, B. Camacho Quevedo, A. Cappi, F. Caro, C. S. Carvalho, T. Castro, F. Cogato, S. Contarini, A. R. Cooray, S. Davini, G. Desprez, A. Díaz-Sánchez, S. Di Domizio, A. G. Ferrari, I. Ferrero, A. Finoguenov, F. Fornari, L. Gabarra, K. Ganga, J. García-Bellido, T. Gasparetto, V. Gautard, E. Gaztanaga, F. Giacomini, F. Gianotti, G. Gozaliasl, A. Gregorio, M. Guidi, C. M. Gutierrez, A. Hall, H. Hildebrandt, J. Hjorth, A. Jimenez Muñoz, J. J. E. Kajava, Y. Kang, V. Kansal, D. Karagiannis, C. C. Kirkpatrick, S. Kruk, F. Lacasa, M. Lattanzi, S. Lee, J. Le Graet, L. Legrand, M. Lembo, T. I. Liaudat, S. J. Liu, A. Loureiro, J. Macias-Perez, M. Magliocchetti, F. Mannucci, R. Maoli, J. Martín-Fleitas, L. Maurin, R. B. Metcalf, M. Migliaccio, M. Miluzio, P. Monaco, A. Montoro, G. Morgante, S. Nadathur, K. Naidoo, P. Natoli, Nicholas A. Walton, L. Pagano, K. Paterson, L. Patrizii, A. Pisani, V. Popa, D. Potter, P. Reimberg, I. Risso, P.-F. Rocci, M. Sahlén, E. Sarpa, A. Schneider, M. Schultheis, D. Sciotti, M. Sereno, L. C. Smith, K. Tanidis, C. Tao, G. Testera, R. Teyssier, S. Tosi, A. Troja, M. Tucci, C. Valieri, D. Vergani, G. Verza, P. Vielzeuf

Cosmology and Nongalactic Astrophysics

Tachyonic dark energy- Constraints from current observations

Ramanpreet Singh, Athul CN and H.K. Jassal

Recent observations from the DESI survey have reignited the debate on the true nature of dark energy, challenging the standard model of cosmology. The results suggest a preference for dynamical dark energy rather than a constant. Several recent analyses of DESI data indicate that the universe's expansion may not be accelerating in the way suggested by supernova based cosmology. Motivated by these studies, we investigated a tachyon type scalar field $\phi$ as a model for dark energy, assuming an exponential potential for the field and performed parameter estimation using MCMC techniques. Such a model offers solutions that have $w\sim-1$ and are decelerating without requiring a phantom like equation of state (EoS). The present day value of EoS parameter is treated as a free parameter. However, for the reference model, we fix its present value to $-1$. The analysis is carried out using Pantheon+ and BAO measurements from DESI. The results show that both types of datasets consistently predict a turnaround in the EoS, regardless of whether $w_{\phi0}$ is treated as a free parameter or fixed to $-1$. The corresponding deceleration parameter also exhibits a future turnaround for both datasets when $w_{\phi0}$ is free. However, in the reference model with $w_{\phi0}=-1$, the deceleration parameter instead approaches $-1$ asymptotically. A model comparison shows that the Pantheon+ dataset favors free $w_{\phi0}$, while BAO observations prefer $w_{\phi0} = -1$. This indicates a disagreement in the future evolution predicted by the two datasets within the tachyon dark energy model.
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High Energy Astrophysical Phenomena

Massive Star Clusters as sources of high-energy gamma radiation

Luana N. Padilha and Rita C. Anjos

This paper investigates the contribution of massive star clusters (MSC) as sources of high-energy gamma rays and their impact on the ultra-high-energy (UHE) emission observed throughout the Galaxy. By modeling proton injection, the study explores how the acceleration of protons in massive star clusters contributes to the gamma radiation detectable from Earth. The analysis focuses on two primary types of clusters: widespread, dispersed clusters and younger, compact massive clusters, both of which host shock waves generated by supernova remnants (SNR). Clusters located near the solar system, within a 3-kiloparsec radius,are identified. Analytical methods are used to calculate energy spectra and gamma-ray production rates. The findings suggest that young and compact MSC contribute to multi-TeV to PeV gamma-ray emission, with the dominant contribution arising from nearby populations.
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Solar and Stellar Astrophysics

Predicting CME Arrivals with Heliospheric Imagers from L5: A Data Assimilation Approach

Tanja Amerstorfer, Justin Le Louëdec, David Barnes et al. (+5 more)

The Solar TErrestrial RElations Observatory (STEREO) mission has laid a foundation for advancing real-time space weather forecasting by enabling the evaluation of heliospheric imager (HI) data for predicting coronal mass ejection (CME) arrivals at Earth. This study employs the ELEvoHI model to assess how incorporating STEREO/HI data from the Lagrange 5 (L5) perspective can enhance prediction accuracy for CME arrival times and speeds. Our investigation, preparing for the upcoming ESA Vigil mission, explores whether the progressive incorporation of HI data in real-time enhances forecasting accuracy. The role of human tracking variability is evaluated by comparing predictions based on observations by three different scientists, highlighting the influence of manual biases on forecasting outcomes. Furthermore, the study examines the efficacy of deriving CME propagation directions using HI-specific methods versus coronagraph-based techniques, emphasising the trade-offs in prediction accuracy. Our results demonstrate the potential of HI data to significantly improve operational space weather forecasting when integrated with other observational platforms, especially when HI data from beyond 35{\deg} elongation are used. These findings pave the way for optimising real-time prediction methodologies, providing valuable groundwork for the forthcoming Vigil mission and enhancing preparedness for CME-driven space weather events.
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All authors Tanja Amerstorfer, Justin Le Louëdec, David Barnes, Maike Bauer, Jackie A. Davies, Satabdwa Majumdar, Eva Weiler, Christian Möstl

Earth and Planetary Astrophysics · Cross-listed from physics.ao-ph

Oceanic internal tides: do they get phased at the Equator?

Camille Moisset, Bruce Sutherland and Lois Baker

Low-mode baroclinic tides play a major role in ocean dynamics, especially for energy redistribution and deep ocean mixing. These internal waves, generated by tidal flow over submarine topography, can propagate for thousands of kilometres across ocean basins, and become unstable through wave-mean flow or wave-wave interactions. Satellite observations of internal tides have shown that part of their lunar semidiurnal (M2) altimetry signal loses phase coherence in equatorial regions, thus affecting how we interpret their dynamics and energy distribution (Buijsman et al. 2017). We investigate the interaction of a baroclinic M2 internal tide wavepacket with an equatorial zonal jet, possibly of any horizontal or vertical structure. The dynamics of the low modes are explored as well as the potential excitation of higher vertical modes and how these interactions can generate incoherences in the baroclinic tide signal. We develop an idealized linear model using modal decomposition (Kelly et al. 2016), which is solved using Dedalus, to study the dynamics of a mode 1 M2 internal wavepacket on an equatorial beta plane. A zonal jet, with a uniform or a sheared vertical structure, is added at the equator to investigate potential wave-mean flow interaction. We find that a vertically uniform zonal jet affects the propagation of the mode 1 wavepacket. Depending on the strength of the jet, this can cause total reflection or strong distortion of the wavepacket. In contrast, a wavepacket entering a vertically sheared jet shows energy scattering into higher modes, which have lower phase and group speeds, shorter wavelengths, and are thus more susceptible to dissipation (and critical layers for non-uniform stratification). As the wavepacket exits the jet, reverse energy transfer occurs and the phase speed difference between the modes may explain part of the phase incoherence observed in altimetry data.
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Earth and Planetary Astrophysics

Numerical simulations of astrophysical dynamos and applications to giant planets

Albert Elias-López

Magnetic fields pervade astrophysical systems and strongly influence their dynamics. Because magnetic diffusion is usually much faster than system evolution, ancient fields cannot explain the present magnetization of planets, stars, and galaxies. Instead, self-sustaining dynamos, which convert fluid motion into magnetic energy, offer the most robust explanation. Numerical magnetohydrodynamic simulations are essential to understanding this phenomenon. This thesis uses numerical models of self-excited dynamos in two contexts: the interstellar medium (ISM) and the interiors of gas giant planets. First, I use 3D MHD simulations with the Pencil Code to study magnetic growth from irrotational, subsonic expansion flows, a simplified representation of supernova-driven motions in the ISM. These curl-free flows mimic stellar explosions and winds, drive turbulence, and seed magnetic amplification. The second part examines planetary dynamos. I outline the properties of planetary magnetic fields and their modeling through convection in spherical shells. Although many exoplanets are known, their magnetic fields remain difficult to detect, but may be observable through coherent radio emission with new low-frequency instruments. Using 3D dynamo simulations with the MagIC code, coupled to thermodynamic profiles from MESA-based evolution models, I study the magnetic evolution of cold gas giants. The models show a slow decline in field strength, a shift from multipolar to dipolar states, and clear evolutionary trends in dynamo behavior. I also investigate hot Jupiters, where strong irradiation alters convection and rotation. Most remain fast rotators, but massive, distant planets may enter different regimes. When heating is concentrated in outer layers, convection in the dynamo region weakens, reducing expected field strengths and helping explain the absence of confirmed detections in past radio surveys.
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Cosmology and Nongalactic Astrophysics · Cross-listed from stat.AP

Bayesian Model Selection with an Application to Cosmology

Nikoloz Gigiberia

We investigate cosmological parameter inference and model selection from a Bayesian perspective. Type Ia supernova data from the Dark Energy Survey (DES-SN5YR) are used to test the $\Lambda$CDM, $w$CDM, and CPL cosmological models. Posterior inference is performed via Hamiltonian Monte Carlo using the No-U-Turn Sampler (NUTS) implemented in NumPyro and analyzed with ArviZ in Python. Bayesian model comparison is conducted through Bayes factors computed using the bridgesampling library in R. The results indicate that all three models demonstrate similar predictive performance, but $w$CDM shows stronger evidence relative to $\Lambda$CDM and CPL. We conclude that, under the assumptions and data used in this study, $w$CDM provides a better description of cosmological expansion.
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Earth and Planetary Astrophysics

Cosmic-Ray Bath in a Past Supernova Gives Birth to Earth-Like Planets

Ryo Sawada, Hiroyuki Kurokawa, Yudai Suwa et al. (+3 more)

A key question in astronomy is how ubiquitous Earth-like rocky planets are. The formation of terrestrial planets in our solar system was strongly influenced by the radioactive decay heat of short-lived radionuclides (SLRs), particularly $^{26}$Al, likely delivered from nearby supernovae. However, current models struggle to reproduce the abundance of SLRs inferred from meteorite analysis without destroying the protosolar disk. We propose the `immersion' mechanism, where cosmic-ray nucleosynthesis in a supernova shockwave reproduces estimated SLR abundances at a supernova distance ($\sim$1 pc), preserving the disk. We estimate that solar-mass stars in star clusters typically experience at least one such supernova within 1 pc, supporting the feasibility of this scenario. This suggests solar-system-like SLR abundances and terrestrial planet formation are more common than previously thought.
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All authors Ryo Sawada, Hiroyuki Kurokawa, Yudai Suwa, Tetsuo Taki, Shiu-Hang Lee, Ataru Tanikawa

High Energy Astrophysical Phenomena

No evidence for accretion around the intermediate-mass black hole in Omega Centauri

Angiraben D. Mahida, Arash Bahramian, James C.A. Miller Jones et al. (+5 more)

For over a decade, both theoretical predictions and observational studies have suggested that $\omega$ Centauri ($\omega$ Cen), the most massive Milky Way globular cluster, might harbor an intermediate-mass black hole (IMBH). Recently, identification of fast-moving stars in the core of $\omega$ Cen provided the strongest evidence to date for the presence of such an IMBH. One of the key questions in the study of IMBHs is their accretion efficiency, which determines their radio and X-ray signatures. We investigate the accretion signature of the IMBH in $\omega$ Cen with ultra-deep radio continuum observations of the central region of the cluster. Using approximately 170 hours of Australia Telescope Compact Array observations, we achieve a root mean square noise of 1.1 $\mu$Jy at 7.25 GHz, making this the most sensitive radio image of the cluster to date. We detect no radio emission at any of the proposed centers of the cluster, imposing stringent constraints on the presence of an accreting IMBH in $\omega$ Cen. Considering the fundamental plane of black hole activity, our findings indicate that the accretion efficiency around the black hole is exceptionally low (with a conservative 3-$\sigma$ upper limit of $\epsilon \lesssim 4\times10^{-3}$).
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All authors Angiraben D. Mahida, Arash Bahramian, James C.A. Miller Jones, Susmita Sett, Kristen Dage, Jay Strader, Timothy J. Galvin, Alessandro Paduano

High Energy Astrophysical Phenomena

A jet bent by a stellar wind in the black hole X-ray binary Cygnus X-1

Steve Prabu, James C.A. Miller-Jones, Arash Bahramian et al. (+7 more)

Jets provide an important channel for kinetic feedback from accreting black holes into their environment, without which models of the formation of large-scale structure in the universe fail to reproduce the observed properties of galaxies. Hence, an accurate measurement of jet power is critical for understanding black hole growth through accretion and also for quantifying the impact of kinetic feedback. However, the absence of instantaneous jet power measurements has precluded direct comparisons with the accretion luminosity, forcing kinetic feedback models to rely on ad hoc assumptions about how much jet power is released per accreted amount of mass. Here we report the detection of stellar wind-induced bending of the jets in the black hole X-ray binary Cygnus X-1, using 18 years of high-resolution radio imaging. By modeling jet-wind interactions, we determine the current kinetic instantaneous power of the jet to be log$_{10}(L_{\rm jet}/{\rm erg\,s}^{-1}) = 37.3_{-0.2}^{+0.1}$, comparable to the accretion energy determined from its bolometric X-ray luminosity. This result critically places prevailing assumptions about the energetics of black hole powered jets in both galaxy formation simulations, and in scaling models of black hole accretion, on a firm empirical footing.
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All authors Steve Prabu, James C.A. Miller-Jones, Arash Bahramian, Valenti Bosch-Ramon, Sebastian Heinz, Steven J. Tingay, Callan M. Wood, Alexandra Tetarenko, Tyrone N. O'Doherty, Valeriu Tudose

Earth and Planetary Astrophysics

An Orbital House of Cards: Frequent Satellite Close Conjunctions

Sarah Thiele, Skye R. Heiland, Aaron C. Boley et al. (+1 more)

The number of objects in orbit is rapidly increasing, primarily driven by the launch of megaconstellations, an approach to satellite constellation design that involves large numbers of satellites paired with their rapid launch and disposal, as well as the overall proliferation of satellite systems. While satellites provide many benefits to society, their use comes with challenges, including the growth of space debris, collision risks, ground casualty risks, optical and radio-spectrum pollution, and the alteration of Earth's upper atmosphere through rocket emissions and reentry ablation. There is potential for current or planned actions in orbit to cause serious degradation of the orbital environment or lead to catastrophic outcomes, highlighting the urgent need to find better ways to quantify stress on the orbital environment. Here we propose a new metric, the CRASH Clock, that measures such stress in terms of the timescale for a possible catastrophic collision to occur if there are no satellite maneuvers or there is a severe loss in situational awareness. Our calculations show that the CRASH Clock is 5.5 days as of June 2025 and continues to decrease, which suggests there is limited time to recover from a wide-spread disruptive event, such as a solar storm. This is in stark contrast to the pre-megaconstellation era: in 2018, the CRASH Clock was 164 days.
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All authors Sarah Thiele, Skye R. Heiland, Aaron C. Boley, Samantha M. Lawler

High Energy Astrophysical Phenomena

Extreme-Lensing Signatures Revealed by Correlations of Simulated Black-Hole Movies

Barbora Bezděková, Shahar Hadar, George Wong et al. (+1 more)

A black hole's gravitational pull can deflect light rays to an arbitrary degree. As a result, any source fluctuation near the black hole creates multiple lagged images on an observer's screen. For optically thin stochastic emission, these light echoes give rise to correlations of brightness fluctuations across time-dependent images (movies). The correlation pattern disentangles source-specific characteristics from universal features dictated by general relativity. This picture has motivated a proposal to use the two-point image correlation function as a probe of extreme gravitational lensing in upcoming black-hole imaging campaigns. In this work, we test the feasibility of this method by computing the two-point correlation function of brightness fluctuations in a black-hole movie of state-of-the-art realism. The movie is generated by ray tracing a general relativistic magnetohydrodynamic simulation, which can then be blurred to any angular resolution. At an effective resolution expected to be achieved by next-generation terrestrial very-long-baseline interferometric arrays, these lensing signatures appear in neither time-averaged images nor light-curve autocorrelations. However, we demonstrate that they are clearly visible in the more fine-grained two-point image correlation function. Our positive findings motivate a more comprehensive investigation into the instrument specifications and inference techniques needed to resolve extreme lensing effects through correlations.
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All authors Barbora Bezděková, Shahar Hadar, George Wong, Maciek Wielgus

Earth and Planetary Astrophysics

Accretion bottleneck in protoplanetary discs: the role of the stellar spin

Cristiano Longarini and Cathie Clarke

We investigate angular momentum transport and accretion properties in a sample of protoplanetary discs with dynamical measurements of stellar masses, disc masses, and scale radii. From these data we infer effective $\alpha$-viscosities, finding a remarkably broad range spanning over three orders of magnitude. This spread correlates with the stellar rotation period: systems with shorter periods exhibit significantly lower accretion rates, suggesting that they are undergoing at least temporary episodes of accretion bottleneck. We interpret this behaviour within the framework of magnetospheric accretion models, where the transition between steady accretion and the propeller regime is set by the relative locations of the co-rotation and magnetospheric radii. Our results indicate that stellar spin is a key parameter in regulating mass transfer from the disc to the star, and provide new evidence that the observed dispersion in $\alpha$ reflects transitions between distinct accretion states rather than differences in global disc properties.
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High Energy Astrophysical Phenomena

The impact of AGN environmental effects on testing general relativity with space-borne gravitational wave detector

Xiangyu Lyu, Hongyu Chen, En-Kun Li et al. (+1 more)

The space-borne gravitational wave detectors such as TianQin offers a new window to test General Relativity by observing the early inspiral phase of stellar-mass binary black holes. A key concern arises if these stellar-mass binary black holes reside in gaseous environments such as active galactic nucleus accretion disks, where environmental effects imprint detectable modulations on the gravitational waveform. Using Bayesian inference on simulated signals containing both environmental and dipole deviation, we have assessed the extent to which the presence of environmental effects affects the detectability of dipole radiation. Our results demonstrate that even in the presence of strong environmental coupling, the dipole parameter can be recovered with high precision, and the evidence for dipole radiation remains distinguishable. Crucially, we find that the existence of environmental effects does not fundamentally impede the identification of dipole radiation, provided both effects are simultaneously modelled in the inference process. This study establishes that future tests of modified gravity with space-borne observatories can remain robust even for sources in astrophysical environments.
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All authors Xiangyu Lyu, Hongyu Chen, En-Kun Li, Yi-Ming Hu

2512.09635 · 10 Dec · We withdraw this manuscript because the results – that AGN environmental effects do not hinder dipole-radiation searches – remains preliminary. The methodology is sound, but the findings require further validation under broader astrophysical assumptions. To avoid potential misinterpretation, we decided to retract this version. We are retracting this version pending a more thorough investigation

Abstract PDF $STELR ×2$ACCR ×1$BAYS ×1$GALAC ×1 +2

Solar and Stellar Astrophysics

First Resolution of a Main Sequence G-Star Astrosphere Using Chandra

C.M. Lisse, S.J. Wolk, B. Snios et al. (+25 more)

We report resolution of a halo of X-ray line emission surrounding the Zero Age Main Sequence (ZAMS) G8.5V star HD 61005 by Chandra ACIS-S. Located only 36.4 pc distant, HD 61005 is young (approx. 100 Myr), x-ray bright (300 times Solar), observed with nearly edge-on geometry, and surrounded by Local Interstellar Medium (LISM) material denser than in the environ of the Sun. HD 61005 is known to harbor large amounts of circumstellar dust in a dense ecliptic plane full of mm-sized particles plus attached, extended wing like structures full of micron sized particles, which are evidence for a strong LISM-dust disk interaction. These properties aided our ability to resolve the 220 au wide astrosphere of HD61005, the first ever observed for a main sequence G-star. The observed x-ray emission morphology is roughly spherical, as expected for an astrospheric structure dominated by the host star. The Chandra spectrum of HD 61005 is a combination of a hard stellar coronal emission (T=8 MK) at Lx = 6 x10e29 erg per sec, plus an extended halo contribution at Lx = 1x10e29 erg per sec dominated by charge exchange (CXE) lines, such as those of OVIII and NeIX. The Chandra CXE x-ray morphology does not track the planar dust morphology but does extend out roughly to where the base of the dust wings begins. We present a toy model of x-ray emission produced by stellar wind (SW)-LISM CXE interactions, similar to the state of the young Sun when it was approximately 100 Myrs old (Guinan and Engle 2007), and transiting through an approximately 1000 times denser part of the interstellar medium (ISM) such as a Giant Molecular Cloud (Stern 2003, Opher and Loeb 2024).
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All authors C.M. Lisse, S.J. Wolk, B. Snios, R.L. McNutt, Jr., J.D. Slavin, R.A. Osten, D.C Hines, J.H. Debes, D. Koutroumpa, V. Kharchenko, J.L. Linsky, P. Brandt, M. Horanyi, H.M. Guenther, E.F. Guinan, S. Redfield, P.C. Frisch, K. Dennerl, V. Kashyap, K.G. Kislyakova, Y.R. Fernandez, E. Provornikova, M.A. MacGregor, C.H. Chen, L. Paxton, K. Dialynas, L. Gu

Earth and Planetary Astrophysics · Cross-listed from physics.ao-ph

Rogue Vertical Drafts in the Mesosphere and Lower Thermosphere: Evidence and Implications

J. L. Chau, A. Berera and D. Huyghebaert

Observational evidence of extreme vertical velocities (|w| ge 12.5 m/s and at times greater than 50 m/s) in the mesosphere and lower thermosphere (MLT), has emerged in recent years. We refer to these events as Rogue Vertical Drafts (RVDs). They exceed five standard deviations of observed vertical velocities and appear as paired updraft-downdraft structures in varicose mode. Four-dimensional observations reveal that RVDs are intermittent, recurrent, and unpredictable. On average, they are expected to occur every sim 12 days during summer over Northern Norway, assuming a 1000 s interval. Different instruments may capture only portions of these events, for example, only upward or downward drafts when restricted to a single altitude range. Despite their rarity, their magnitudes and frequency suggest potential impacts on dust-sized matter escaping from planets, natural and anthropogenic space material, and MLT climate and processes. We propose that RVDs are a fundamental yet under-recognized feature of the MLT, underscoring the need for global observations to assess their prevalence and significance.
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Earth and Planetary Astrophysics

WASP-12, shrouded in mystery or just cold gas?

Simon Daley-Yates, Ricarda Beckmann, Lewis McCallum et al. (+2 more)

Observations of the planet-hosting star WASP-12 show a distinctive depression in the \ion{Mg}{ii} and \ion{Ca}{ii} resonance lines. This has been interpreted as a marker of atmospheric loss from the close-in hot Jupiter WASP-12b and the resulting formation of a gas torus around the star. In this paper we quantify the \ion{Mg}{ii} absorption from this torus, compared to that provided by the stellar wind, the stellar astrosphere and the ISM. To do this we piece together the full density profile of \ion{Mg}{ii} from WASP-12 to an observer on Earth using a combination of hydrodynamical simulations and observations. We find that the bulk of the gas along the line of sight is contained within a dense torus close to WASP-12. However, the temperatures in this torus are sufficient to promote Mg into a doubly (\ion{Mg}{iii}) or higher ionized state. As a result, the singly ionized fraction (\ion{Mg}{ii}) is low. We find that most of the \ion{Mg}{ii} is not in the torus but in the ISM. Despite this, the total column density of \ion{Mg}{ii} is two orders of magnitude lower than required to explain observations of the system. To resolve this discrepancy, we note that the torus gas is at a temperature where it will cool efficiently. We speculate that the onset of the cooling instability will cause the torus to fragment, forming cold clumps with a higher fraction of \ion{Mg}{ii}, capable of explaining the observed absorption.
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All authors Simon Daley-Yates, Ricarda Beckmann, Lewis McCallum, Moira Jardine, Andrew Cameron

High Energy Astrophysical Phenomena

3-Dimensional WIMP Effective Velocity Distribution

Chung-Lin Shan

In this talk, I discussed a 3-dimensional "effective" velocity distribution of Weakly Interacting Massive Particles (WIMPs), which, instead of the theoretically predicted velocity distribution of "entire" Galactic Dark Matter particles, describes the actual velocity distribution of WIMPs "scattering off" (specified) target nuclei in an underground detector. Based on numerical results carried out by our double Monte Carlo scattering-by-scattering simulation of 3-dimensional elastic WIMP-nucleus scattering, an (asymmetric) "forward-backward asymmetry" was also demonstrated.
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Earth and Planetary Astrophysics

The Response of Planetary Atmospheres to the Impact of Icy Comets III: Impact Driven Atmospheric Escape

Felix Sainsbury-Martinez, Greg Cooke and Catherine Walsh

In an Earth-analogue atmosphere, water vapour is a key carrier of hydrogen in the lower atmosphere with its transport above the tropopause controlling the atmospheric hydrogen escape rate. On the Earth, this escape is limited by transport though the tropospheric cold trap where water vapour condenses. However, on a tidally-locked exoplanet, the strong day-night temperature gradient drives a global-scale circulation. This circulation could rapidly transport water through the cold trap, potentially increasing hydrogen escape and impacting the composition of potentially habitable worlds. We couple cometary impact and planetary atmospheric models to simulate water-depositing impacts with both a tidally-locked and Earth-analogue atmosphere and quantify how atmospheric circulations transport water from the impact site to high altitudes where it can potentially drive escape. The global nature of the atmospheric circulations on a tidally-locked world enhances hydrogen escape, with both our unimpacted tidally-locked and Earth-analogue atmospheres exhibiting similar mass loss rates despite the tidally-locked atmosphere being bpth cooler and drier near the surface. When considering the effects of a cometary impact, we find an order of magnitude difference in peak escape rates between impacts on the day-side ($\Phi_{\mathrm{escape}}=1.33\times10^{10}\,\mathrm{mol\,mth^{-1}}$) and night-side ($\Phi_{\mathrm{escape}}=1.51\times10^{9}\,\mathrm{mol\,mth^{-1}}$) of a tidally-locked atmosphere, with the latter being of the same order of magnitude as the peak escape rate found for an impact with an Earth-analogue atmosphere ($\Phi_{\mathrm{escape}}=2.7\times10^{9}\,\mathrm{mol\,mth^{-1}}$). Our results show the importance of understanding the underlying atmospheric circulations when investigating processes, such as hydrogen escape, which depend upon the vertical advective mixing and transport.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Improving the inference of the stellar quantities using the extended $I$-Love-$Q$-$\delta M$ relations

Eneko Aranguren, José A. Font, Nicolas Sanchis-Gual et al. (+1 more)

In relativistic Astrophysics the $I$-Love-$Q$ relations refer to approximately EoS-independent relations involving the moment of inertia, Love number, and quadrupole moment through some quantities that are normalised by the mass $M_0$ of the background configuration of the perturbative scheme. Since $M_0$ is not an observable quantity, this normalisation hinders the direct applicability of the relations. A common remedy assumes that $M_0$ coincides with the actual mass of the star $M_S$; however, this approximation is only adequate for very slow rotation (when the dimensionless spin parameter is $\chi_S<0.1$). The more accurate alternative approach, based on the $I$-Love-$Q$-$\delta M$ set of relations, circumvents this limitation by enabling the inference of $M_0$. Here we review both approaches and provide numerical comparisons.
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All authors Eneko Aranguren, José A. Font, Nicolas Sanchis-Gual, Raül Vera

Cosmology and Nongalactic Astrophysics

Observational constraints on New Tsallis holographic energy in Rastall theory

N. Sadeghnezhad, R. Jalalzadeh, Z. Davari et al. (+1 more)

The cosmological implications of New Tsallis holographic dark energy (NTHDE) in Rastall theory have been studied. Using the data set that includes DESI BAO (DR2), PantheonPlus SNe Ia, H(z) measurements, and BBN and the MCMC analysis, the key cosmological and model-specific parameters are constrained. The result is compared with that of the {\Lambda}CDM model indicating that in addition to providing a viable dynamical dark energy framework, predictions for H(z) are slightly more consistent with intermediate-redshift observations. Generally, the model remains compatible with current data and offers testable deviations from {\Lambda}CDM for upcoming surveys. It is also seen that when the energy density of quantum fields in vacuum, exposed by NTHDE, is combined with the Rastall correction term to the general relativity, a plausible candidate for dynamical dark energy is obtained that mimic the current value of the dark energy density parameter reported in the {\Lambda}CDM model. The latter cannot be repeated by NTHDE alone. The study also confirms previous theoretical and observational constraints on the Rastall parameter obtained by focusing on the thermodynamics, early universe, pulsars, and the early-type galaxies.
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All authors N. Sadeghnezhad, R. Jalalzadeh, Z. Davari, B. Afshar

Solar and Stellar Astrophysics

Ultimate large-$Rm$ regime of the solar dynamo

François Rincon

For more than 40 years the quest to understand how large-scale magnetic fields emerge from turbulent flows in rotating astrophysical systems, such as the Sun, has been a major focus of computational astrophysics research. Using a parameter scan and phenomenological analysis of maximally simplified three-dimensional cartesian magnetohydrodynamic simulations of large-scale non-linear helical turbulent dynamos, I present results in this Letter that strongly point to an asymptotic ultimate regime of the large-scale solar dynamo at large magnetic Reynolds numbers, $Rm$, involving helicity fluxes between hemispheres. I obtained corresponding numerical solutions at both $Pm>1$ and $Pm<1$, and show that they can currently only be achieved in clean, simplified numerical set-ups. The analysis further strongly suggests that all global simulations to date lie in non-asymptotic turbulent magnetohydrodynamic regimes highly sensitive to changes in kinetic and magnetic Reynolds numbers. Ideas are presented to attempt to reach the ultimate regime in such 'realistic' global spherical models at a reasonable numerical cost. Overall, the results clarify the current state, and some hard limitations of the brute-force numerical modelling approach applied to this, and other similar astrophysical turbulence problems.
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Astrophysics of Galaxies

Can Clump Properties Predict Core Distribution in Star Formation? A Statistical Analysis of MHD Simulations

Wei-An Chen, Seamus D. Clarke and Ya-Wen Tang

Dense cores, the progenitors of stars, are in sub-pc scale and fragmented from pc-scale clumps. However, it is still unclear that how strongly the fragmentation process is affected by the properties of the host clumps, and how these properties influence the core distribution observed in recent millimeter (mm) and sub-mm observations. To systematically investigate this relation, we employed MHD simulations of convergent flows to generate a large sample of clumps and analyzed their properties using various techniques. Alignment parameters were used to quantify core distribution, while energy terms were calculated to assess the influence of gravity, magnetic fields, and turbulence. We found the core distribution only exhibiting weak correlations between alignment parameters and clump properties. For an individual clump, turbulence is believed to significantly contribute to these features by inducing non-homologous collapse and ongoing fragmentation. Nevertheless, for the entire population, more compact core distributions are observed due to the dominance of gravity. Overall, these factors suggest that clump properties are not sufficient to accurately determine core distribution.
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Astrophysics of Galaxies

Age, Chemistry, and Kinematics of the Inner Galaxy Revealed by MUSE

Zixian Wang, Michael R. Hayden, Sanjib Sharma et al. (+3 more)

The bar/bulge and inner disk are fundamental building blocks of the Milky Way, containing a large fraction of its stellar mass. However, stars in these regions are faint, crowded, and have high extinction, which makes studying their formation and evolution challenging. Using the integral-field spectrograph MUSE with adaptive-optics on the Very Large Telescope, we overcome these limitations and measure accurate ages, chemical abundances, and line-of-sight velocities for 98 main-sequence turn-off and subgiant branch stars with $R_{gc}<3.5$ kpc in Baade's Window. We find that 17% stars have ages younger than 5 Gyr, and the age distribution reveals multiple peaks at 3.1, 4.8, 7.6, and 10.8 Gyr, indicating that star formation in the inner Galaxy occurred in multiple episodes. These stars are predominantly metal-rich but span a broad metallicity range ($-1.2<$[Fe/H]$<+0.6$). The [$\alpha$/Fe]-[Fe/H] distribution shows both $\alpha$-rich and $\alpha$-poor sequences, with most stars being metal-rich and low-[$\alpha$/Fe]. Our results demonstrate that IFUs enable reliable measurements of stellar parameters even in the most crowded regions of the Milky Way, opening a new pathway to study the chemodynamical evolution of the inner Galaxy.
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All authors Zixian Wang, Michael R. Hayden, Sanjib Sharma, Joss Bland-Hawthorn, Anil C. Seth, Gail Zasowski

Solar and Stellar Astrophysics

Surface image and activity-corrected orbit of the RS CVn binary HR 7275: Disentangling activity tracers

Ö. Adebali, M. Weber, K. G. Strassmeier et al. (+3 more)

Quantifying stellar parameters and magnetic activity for cool stars in double-lined spectroscopic binaries (SB2) is not straightforward, as both stars contribute to the observed composite spectra and are likely variable. Disentangled component spectra allow a detailed analysis of a component's magnetic activity. We aim at separating the spectra of the two stellar components of the HR\,7275 SB2 system. Our further aim is a more accurate orbital solution by cleaning the observed radial velocities (RV) from activity perturbations of the spotted primary ("RV jitter") and obtain a surface image of this component. The Doppler image of the primary shows two large cool spots of size $\approx$20% of the visible hemisphere plus three smaller spots, each still $\approx$13% in size. In total, HR\,7275a exhibited an impressive spottedness of $\approx$40%\ of its entire surface in May-June 2022. The RV is modulated by the rotation of the primary with maximum amplitudes of 320\,\ms\ and 650\,\ms\ for two different modulation behaviors during the 250\,d of our observations. This jitter is primarily caused by the varying asymmetries of the apparent disk brightness due to the cool spots. Its removal resulted in roughly ten times higher precision of the orbital elements. Our snapshot magnetic-field measurements reveal phase-dependent (large-scale) surface fields between +0.6$\pm$2.0\,G at phase 0.1 and $-$15.2$\pm$2.7\,G at phase 0.6, indicating a complex magnetic morphology related to the location of the photospheric spots. We also obtain a logarithmic lithium abundance of 0.58$\pm$0.1 for HR\,7275a, indicating considerable mixing, and 0.16$^{+0.23}_{-0.63}$ for HR\,7275b, which is an extremely low value. }
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All authors Ö. Adebali, M. Weber, K. G. Strassmeier, I. V. Ilyin, M. Steffen, Zs. Kovári

Astrophysics of Galaxies

CASCADE: Filamentary accretion flows in Cygnus X DR20

M. Sawczuck, H. Beuther, S. Suri et al. (+11 more)

Aims. We investigate the role of filaments in high-mass star formation, whether gas flows from large to small scales along them, and what their properties might reveal about the region they are found in. Methods. The Max Planck IRAM Observatory Program (MIOP), the Cygnus Allscale Survey of Chemistry and Dynamical Environments (CASCADE), includes high spatial resolution (~3”) data of HCO+(1-0) and H13CO+(1-0) emission in the star-forming DR20 region in the Cygnus X complex. In this data we identify filaments with the structure identification algorithm DisPerSE. We further analyze these filaments using Gaussian fits to the spectra to determine the line peak velocity and full width half maximum along them. The Python package FilChaP was used to determine filament widths. Results. We find projected velocity gradients inside several filaments between 0.4 to 2.4km/s over projected length-scales of 0.1pc toward star-forming cores. This can be interpreted as a sign of gas flowing along the filaments toward the cores. The filament width distributions exhibit median values between 0.06 and 0.14pc depending on the core, the tracer, and the method. Standard deviations are approximately 0.02 to 0.06pc. These values are roughly in agreement with the filament width of 0.1pc typically found in nearby low-mass star-forming regions. Conclusions. This first analysis of filamentary properties within the Cygnus X CASCADE program reveals potential signatures of gas flows along filaments onto star-forming cores. Furthermore, the characteristics of the filaments in this high-mass star-forming region can be compared to those of filaments in low-mass star-forming regions typically studied before. Extending such studies to the entire CASCADE survey will enhance our knowledge of high-mass filament properties on solid statistical grounds.
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All authors M. Sawczuck, H. Beuther, S. Suri, F. Wyrowski, K.M. Menten, J.M. Winters, L. Bouscasse, N. Schneider, T. Csengeri, C. Gieser, S. Li, D. Semenov, I. Skretas, M.R.A. Wells

Cosmology and Nongalactic Astrophysics

SLICE – Combining Strong Lensing and X-ray in AC 114. Further Insights into the Merger Scenario

Marceau Limousin, Benjamin Beauchesne, Keren Sharon et al. (+14 more)

AC114 is a historically significant galaxy cluster, being one of the first strong lensing clusters detected from the ground in the early 1990s, prior to the launch of the HST. Despite this early prominence, no detailed lensing analyses have been carried out for more than fifteen years. We here study this cluster using JWST imaging obtained as part of the SLICE program, complemented by archival HST and X-ray observations. JWST data reveal ten new multiply imaged systems and enable the identification of conjugate substructures in several of the sixteen systems, significantly increasing the number of strong lensing constraints. Using these data, we construct a parametric mass model with Lenstool and extend it by explicitly incorporating the Chandra data in a combined strong lensing+X-ray fit. Our best-fit model reproduces the multiple images with an RMS of 0.4" while simultaneously matching the X-ray data. The dark matter distribution is unimodal and centered on the brightest cluster galaxy, with a large core radius of 83+-5kpc, consistent with values reported in other strong lensing clusters. The strong lensing constraints require the inclusion of an external shear component which position angle points unambiguously towards a nearby (~1Mpc), well defined mass concentration at the same redshift in the North-West, for which we propose the naming AC114b. The spatial coverage of the XMM-Newton data encompasses the whole structure, allowing us to probe the X-ray properties of the companion cluster and the thermodynamics of AC114, providing evidence for a major merger, in line with previous signatures seen in Chandra, radio and optical spectroscopic data. Our results shed new light on the merging scenario, revealing a major merger caught in a late post-collisional phase, where AC114 is the dominant system and Ac114b has likely been stripped of its hot gas.
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All authors Marceau Limousin, Benjamin Beauchesne, Keren Sharon, Dominique Eckert, Guillaume Mahler, Johan Richard, David Lagattuta, Gourav Khullar, Mathilde Jauzac, Mike Gladders, Marco Balboni, Fabio Gastaldello, Stefano Ettori, Catherine Cerny, Eric Jullo, Gavin Leroy, Nency Patel

High Energy Astrophysical Phenomena

Dirac vs. Majorana Dark Matter Imprints on Neutron Star Observables

M. Bhuyan, Jeet Amrit Pattnaik, S. K. Patra et al. (+1 more)

The fundamental character of a fermionic dark matter, whether it is a Dirac or Majorana particle remains a key unresolved issue whose answer would profoundly affect dark-sector phenomenology and detection strategies thereby motivates complementary probes across particle and astrophysical experiments. Compact stars, particularly neutron stars, offer unique astrophysical laboratories for probing such fundamental properties under extreme densities. The presence of a fermionic DM admixed with nuclear matter can modify the equation of state, thereby affecting observable quantities such as the mass-radius (M-R) relation and tidal deformability. In this work, we investigate how the intrinsic particle nature of fermionic DM influences neutron star structure. Within a relativistic mean-field framework extended by a scalar (or Higgs like) portal coupling between DM and nucleons, we construct self-consistent equation of states for both Dirac and Majorana cases and solve the Tolman-Oppenheimer-Volkoff equations to obtain stellar configurations. Owing to the difference in internal degrees of freedom, Dirac DM (four degrees of freedom) generally softens the equation of state more strongly than Majorana DM (two degrees of freedom), leading to smaller radii and lower maximum masses. We identify the parameter space consistent with current NICER and gravitational-wave constraints, highlighting the potential of compact-star observations to discriminate between Dirac and Majorana dark matter.
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All authors M. Bhuyan, Jeet Amrit Pattnaik, S. K. Patra, Sudhanwa Patra

Cosmology and Nongalactic Astrophysics

Constraints on Spatial Curvature and Dark Energy Dynamics in the $w$CDM Model from DESI DR1 and DR2

Manish Yadav, Archana Dixit, M. S. Barak et al. (+1 more)

In this study, we investigate the $w$CDM dynamical dark energy model with spatial curvature utilizing the recently released DESI Collaboration data (DR1 and DR2) in conjunction with other observational probes such as BBN, Observational Hubble Data (OHD), and Pantheon Plus (PP). Our investigation attempts to discover which DESI dataset gives a better match to the $w$CDM framework and assess the impact of spatial curvature on cosmological constraints. We find that the cosmic curvature parameter, $\Omega_k$, disfavors the cosmological constant for the DR2+BBN and DR2+BBN+OHD data combinations. However, the deviation from the cosmological constant remains below the $1\sigma$ level, indicating a mild preference for a open universe. In contrast, when using the DR1 based combinations namely DR1+BBN and DR1+BBN+OHD-the deviation from the cosmological constant increases to approximately $1.2\sigma$, suggesting a slightly stronger indication of a open geometry. Also, the best-fit values of the Hubble constant ($H_0$) obtained from the DR1+BBN+OHD+PP and DR2+BBN+OHD+PP combinations within the dynamical dark energy model are consistent with the results reported by the Planck Collaboration. Our findings provide constraints on the dark energy EoS parameter $ w_{\mathrm{}0}$, reveal a mild but notable deviation from the vacuum energy ($w = -1$) scenario at a significance level $1.8\sigma$ from DR2+BBN+OHD+PP and $0.5\sigma$ from DR1+BBN+OHD+PP, both favoring the quintessence region of dark energy. Furthermore, the key physical distance measures $D_H$, $D_V$, and $D_M$ show better consistency with our model when analyzed with the DR2 data.
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All authors Manish Yadav, Archana Dixit, M. S. Barak, Anirudh Pradhan

High Energy Astrophysical Phenomena

X-ray Polarization and Spectral Variations in an Extreme High-Synchrotron-Peaked Blazar 1ES 1101–232

Xin-Ke Hu, Jin Zhang, Fei Xie et al. (+1 more)

We present the first X-ray polarimetric observation of the extreme high-synchrotron-peaked blazar 1ES 1101–232, conducted by the Imaging X-ray Polarimetry Explorer (IXPE). The data analysis incorporates simultaneous and quasi-simultaneous observations from Swift-XRT and NuSTAR. Our results reveal a significant detection of X-ray polarization in the 2–6 keV band at a confidence level (CL) of 6.6$\sigma$, with a polarization degree of $\Pi_{\rm X}=17.9\%\pm2.7\%$ and an electric vector position angle (EVPA) of $\psi_{\rm X}=10^\circ.0\pm4^\circ.4$. An even higher polarization degree of $\Pi_{\rm X}=38.9\%\pm9.1\%$ with an EVPA of $\psi_{\rm X}=13^\circ.9\pm6^\circ.7$ is observed within a narrower time interval, at a CL of 4.3$\sigma$. During the IXPE observational campaign, the X-ray spectrum of 1ES 1101–232 exhibits a clear soft-to-hard spectral evolution in the 0.3–10 keV band, although no significant flux variability is detected. Additionally, a clockwise hysteresis loop is identified in the flux–photon index plane. These findings collectively indicate that the X-ray emission from 1ES 1101–232 originates in a region characterized by a well-ordered magnetic field through synchrotron radiation.
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All authors Xin-Ke Hu, Jin Zhang, Fei Xie, Xiang-Gao Wang