Astronomy & Astrophysics最新文献

{"title":"Is ozone a reliable proxy for molecular oxygen?","authors":"Thea Kozakis, João M. Mendonça, Lars A. Buchhave, Luisa M. Lara","doi":"10.1051/0004-6361/202556015","DOIUrl":"https://doi.org/10.1051/0004-6361/202556015","url":null,"abstract":"In the search for life in the Universe, molecular oxygen (O<sub>2<sub/>) combined with a reducing species, such as methane (CH<sub>4<sub/>), is considered a promising disequilibrium biosignature. In cases where it would be difficult or impossible to detect O<sub>2<sub/> (such as in the mid-IR or low O<sub>2<sub/> levels), it has been suggested that ozone (O<sub>3<sub/>), the photochemical product of O<sub>2<sub/>, could be used as a proxy for determining the abundance of O<sub>2<sub/>. As the O<sub>2<sub/>–O<sub>3<sub/> relationship is known to be nonlinear, the goal of this series of papers is to explore how it would change for different host stars and atmospheric compositions and learning how to use O<sub>3<sub/> to infer O<sub>2<sub/>. We used photochemistry and climate modeling to further explore the O<sub>2<sub/>–O<sub>3<sub/> relationship by modeling Earth-like planets with the present atmospheric level (PAL) of O<sub>2<sub/> between 0.01% and 150%, along with high and low CH<sub>4<sub/> abundances of 1000% and 10% PAL, respectively. Methane is of interest not only because it is a biosignature, but it is also the source of hydrogen atoms for hydrogen oxide (HO<sub><i>x<i/><sub/>), which destroys O<sub>3<sub/> through catalytic cycles, and acts as a catalyst for the smog mechanism of O<sub>3<sub/> formation in the lower atmosphere. We find that varying CH<sub>4<sub/> causes changes to the O<sub>2<sub/>–O<sub>3<sub/> relationship in ways that are highly dependent on both the host star and O<sub>2<sub/> abundance. A striking result for high CH<sub>4<sub/> models in high O<sub>2<sub/> atmospheres around hotter hosts is that enough CH<sub>4<sub/> is efficiently converted into H<sub>2<sub/>O to significantly impact stratospheric temperatures, and therefore the formation and destruction rates of O<sub>3<sub/>. Changes in HO<sub><i>x<i/><sub/> have also been shown to influence both the HO<sub><i>x<i/><sub/> catalytic cycle and production of smog O<sub>3<sub/>, causing variations in harmful UV reaching the surface, as well as changes in the 9.6 μm O<sub>3<sub/> feature in emission spectra. This study further demonstrates the need to explore the O<sub>2<sub/>–O<sub>3<sub/> relationship in different atmospheric compositions in order to use O<sub>3<sub/> as a reliable proxy for O<sub>2<sub/> in future observations.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"87 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145103607","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Blowing star formation away in AGN hosts (BAH)","authors":"Rogemar A. Riffel, Carlos R. Melo-Carneiro, Gabriel Luan Souza-Oliveira, Rogério Riffel, Cristina Furlanetto, Nadia L. Zakamska, Santiago Arribas, Marina Bianchin, Ana L. Chies-Santos, José Henrique Costa-Souza, Maitê S. Z. de Mellos, Michele Perna, Thaisa Storchi-Bergmann","doi":"10.1051/0004-6361/202556329","DOIUrl":"https://doi.org/10.1051/0004-6361/202556329","url":null,"abstract":"We report the detection of a gravitationally lensed galaxy by the nearby spiral galaxy CGCG 012-070 (<i>z<i/> = 0.048) using integral field unit (IFU) observations with the Near-Infrared Spectrograph (NIRSpec) instrument on board the <i>James Webb<i/> Space Telescope (JWST). The lensed galaxy is identified through the flux distributions of emission lines in the rest-frame optical, consistent with a source located at a redshift of <i>z<i/> ∼ 2.89. The system is detected in [O III] <i>λλ<i/>4959, 5007, H<i>β<i/>, and H<i>α<i/> emission lines, exhibiting line ratios typical of a star-forming galaxy. The emission-line flux distributions reveal three distinct components, which are modeled using an elliptical power-law mass profile for the lens galaxy. This model provides a good characterization of the source and reveals a disturbed star-forming morphology consistent with those of galaxies at cosmic noon. This serendipitous discovery of a rare low-redshift strong lens highlights the critical role of IFU observations in expanding the lens census and advancing our understanding of galaxy mass profiles and evolution.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"56 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145103634","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Signatures and bias assessment of rotation in galaxy cluster members","authors":"D. Castellani, G. Ferrami, C. Grillo, G. Bertin","doi":"10.1051/0004-6361/202555077","DOIUrl":"https://doi.org/10.1051/0004-6361/202555077","url":null,"abstract":"<i>Context.<i/> In dynamically relaxed galaxy clusters, the galactic component is typically assumed to have zero or negligible mean motions.<i>Aims.<i/> We investigate the possible presence of systematic rotation in the member galaxies of a sample of 17 nearby (<i>z<i/> < 0.1), rich (at least 80 identified members) Abell clusters. We also assess the extent to which low-number statistics may influence the recovery of the rotation parameters.<i>Methods.<i/> Following the methods often used in the context of globular clusters and of clusters of galaxies, we estimate a representative value of the systematic rotation velocity (<i>v<i/><sub>rot<sub/>) and the position angle of the projected rotation axis for the set of spectroscopically confirmed member galaxies within 1.5 Mpc from the centre of each cluster. We study the robustness of our rotational velocity measurements as a function of the number of galaxies, <i>N<i/>, included in the analysis with a bootstrapping technique.<i>Results.<i/> Eight clusters with sufficiently abundant and regular data (A1367, A1650, A2029, A2065, A2142, A2199, A2255, and A2670) exhibit a significantly high rotational velocity, when compared to their velocity dispersion (<i>v<i/><sub>rot<sub/>/<i>σ<i/> ≥ 0.15). Interestingly, three of them (A1650, A2029, and A2199) are confirmed to be cool-core, relaxed clusters with no evidence of recent mergers, as is suggested by X-ray observational data. We also find a general tendency to overestimate the value of <i>v<i/><sub>rot<sub/> when the number of galaxies with measured velocities is reduced, for which we put forward an analytical justification. This bias mainly affects slowly rotating clusters: we find that clusters with 0.15 ≤ <i>v<i/><sub>rot<sub/>/<i>σ<i/> ≤ 0.20 require at least 120 galaxies with measured velocities to limit the percentage error to less than ∼10%, while for rotating clusters with <i>v<i/><sub>rot<sub/>/<i>σ<i/> ≈ 0.25, ∼55 kinematic data points are sufficient to achieve the same accuracy.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"38 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145103647","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterising the red giant companion of the black hole in the BH2 system","authors":"G. Valle, M. Dell’Omodarme, P. G. Prada Moroni, S. Degl’Innocenti","doi":"10.1051/0004-6361/202556349","DOIUrl":"https://doi.org/10.1051/0004-6361/202556349","url":null,"abstract":"<i>Context.<i/> The recently discovered Gaia BH2 binary system composed of a red giant star and a dormant black hole offers a great opportunity to investigate the formation of binary black holes.<i>Aims.<i/> From this perspective, we performed an independent determination of fundamental parameters of the luminous giant star BH2*, a young thin disk object and high [<i>α<i/>/Fe]. A peculiarity of our investigation is the adoption of stellar models specifically tailored to Galactic red giant branch stars with chemical abundances and [<i>α<i/>/Fe] scaling calibrated over a large sample of objects.<i>Methods.<i/> We derived the estimated system parameters using the SCEPtER pipeline, which relies on spectroscopic and global asteroseismic constraints from literature investigations and utilises a large grid of stellar models. We explored the robustness of the determination by adopting two different corrections for Δ<i>ν<i/> values from the literature to account for the current uncertainty on this quantity.<i>Results.<i/> The estimated masses ranged from <i>M<i/> = 1.19 ± 0.05 <i>M<i/><sub>⊙<sub/> to <i>M<i/> = 1.26 ± 0.05 <i>M<i/><sub>⊙<sub/>. The global age of the system was determined to be 4.8 ± 0.5 (sys) ± 0.7 (rand) Gyr. These estimates are consistent with recent findings but exhibit a significantly reduced uncertainty. The radius of BH2* was estimated to be between 8.23 ± 0.12 and 8.47 ± 0.13 <i>R<i/><sub>⊙<sub/>. To explore potential merging or accretion events in the evolutionary history of BH2*, we conducted a supplementary radius estimation based on surface brightness–colour relations utilising <i>V<i/> and <i>K<i/> magnitudes along with <i>Gaia<i/> DR3 parallax data. This estimate, based on two validated relations, indicated a significantly lower radius range of 7.50 ± 0.23 to 7.80 ± 0.23 <i>R<i/><sub>⊙<sub/>. However, this discrepancy was not large enough to rule out a mere fluctuation. Finally, we explored the possibility of inferring non-single-star evolutionary scenarios for BH2* based on its chemical abundance pattern. Principal component analysis (PCA) using <i>α<i/>-element abundances and sodium revealed that the position of BH2* in the PCA space was extreme, even when compared to other young <i>α<i/>-enhanced stars identified as suspect merging products.<i>Conclusions.<i/> Further asteroseismic observations and carbon and nitrogen determinations would enable a more detailed characterisation of BH2* and provide further insights into its evolutionary history.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"18 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145103612","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rotating supermassive Pop III stars on the main sequence","authors":"Devesh Nandal, Gaël Buldgen, Daniel J. Whalen, John Regan, Tyrone E. Woods, Jonathan C. Tan","doi":"10.1051/0004-6361/202555878","DOIUrl":"https://doi.org/10.1051/0004-6361/202555878","url":null,"abstract":"The detection of billion-solar-mass supermassive black holes (SMBHs) within the first billion years of cosmic history challenges conventional theories of black hole formation and growth. Simultaneously, recent JWST observations revealing exceptionally high nitrogen-to-oxygen abundance ratios in galaxies at high redshifts raise critical questions about rapid chemical enrichment mechanisms operating in the early universe. Supermassive stars (SMSs) with masses of 1000–10 000 <i>M<i/><sub>⊙<sub/> are promising candidates to explain these phenomena, but existing models have so far neglected the pivotal role of stellar rotation. Here we present the first comprehensive evolutionary models of rotating Pop III SMSs computed using the GENEC stellar evolution code, including detailed treatments of rotation-induced chemical mixing, angular momentum transport, and mass loss driven by the ΩΓ limit. We demonstrate that rotation significantly enlarges the convective core and extends stellar lifetimes by up to 20%, with moderate enhancement of mass-loss rates as stars approach critical rotation thresholds. Our results further indicate that the cores of SMSs rotate relatively slowly (below ∼200 km s<sup>−1<sup/>), resulting in dimensionless spin parameters <i>a<i/> * < 0.1 for intermediate-mass black hole (IMBH) remnants that are notably lower than theoretical maximum spins. These findings highlight rotation as a key factor in determining the structural evolution, chemical yields, and black hole spin properties of SMSs, and provide critical insights into the observational signatures from the high-redshift universe and their interpretation.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"21 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145103605","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Corona-Australis star-forming region","authors":"E. Rigliaco, R. Gratton, V. Nascimbeni","doi":"10.1051/0004-6361/202555158","DOIUrl":"https://doi.org/10.1051/0004-6361/202555158","url":null,"abstract":"<i>Context<i/>. The star-forming complex of Corona Australis (CrA) is one of the closest and most isolated molecular clouds. It belongs to a chain of clusters that show age gradients with distance from the galactic plane.<i>Aims<i/>. We aim to provide suggestions regarding its formation history by examining the stellar and disk populations, the stellar multiplicity, and the interstellar absorption.<i>Methods<i/>. We made a census of stars and disks using Gaia DR3 and infrared data. Interstellar absorption in the direction of each star was derived by comparing spectral types from the literature and Gaia colors. Stellar multiplicity analysis accounts for both direct observation of visual companions (Gaia data and high-contrast imaging) and indirect detection of the presence of companions (eclipsing binaries, spectroscopic binaries, and astrometry). The properties of the disks were obtained from the slopes of the spectral energy distributions.<i>Results<i/>. As found in previous studies, the CrA complex can be divided into two regions: a younger region (CrA-Main: 3±1 Myr) and an older one (CrA-North: 6.7±0.3 Myr), which are slightly younger than previously thought. Moreover, while CrA-Main still appears bound to the gas, CrA-North is unbound and expanding. The stars that belong to CrA-North were in the most compact configuration 3.72 Myr ago. At that time, CrA-Main and CrA-North were also much closer to each other than they appear now. The fraction of disk-bearing stars is higher in CrA-Main than in CrA-North, as also expected due to the younger age of CrA-Main.<i>Conclusions<i/>. We propose a formation history scenario for the CrA-complex. It started between 15 and 18 Myr ago with supernovae (SNe) explosions in the Upper Centaurus-Lupus complex, followed by a quiescent phase with little star formation. A star formation episode ~7 Myr ago formed CrA-North stars. About 3.7 Myr ago, a second SN explosion south of CrA-North triggered star formation in CrA-Main. This last SN might have been the origin of the pulsar RX J1856.5-3754.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"1 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145103611","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Hot Neptune Initiative (HONEI)","authors":"F. Manni, L. Naponiello, L. Mancini, S. Vissapragada, K. Biazzo, A. S. Bonomo, D. Polychroni, D. Turrini, D. Locci, A. Maggio, V. D’Orazi, M. Damasso, C. Briceño, D. R. Ciardi, C. A. Clark, K. A. Collins, D. W. Latham, N. Law, M. López-Morales, M. B. Lund, L. Malavolta, A. W. Mann, G. Mantovan, D. Nardiello, M. Pinamonti, D. J. Radford, R. P. Schwarz, A. Shporer, A. Sozzetti, C. N. Watkins, S. W. Yee, C. Ziegler, T. Zingales","doi":"10.1051/0004-6361/202556081","DOIUrl":"https://doi.org/10.1051/0004-6361/202556081","url":null,"abstract":"<i>Context<i/>. The formation of Neptune planets with orbital periods shorter than ten days remains uncertain. They might have developed similarly to their longer-period counterparts, emerged from rare collisions between smaller planets, or be the remnant cores of stripped giant planets. Characterising a large number of such planets is important for advancing our understanding of how they form and evolve.<i>Aims<i/>. We aim to confirm the planetary nature and characterise the physical and orbital properties of a close-in Neptune-type transiting exoplanet candidate revealed by TESS around the star TOI-5795 (V = 10.7 mag), 162 pc away from the Sun.<i>Methods<i/>. We monitored TOI-5795 with the HARPS spectrograph for two months to quantify any periodic variations in its radial velocity (RV), necessary to estimate the mass of the smaller companion. We jointly analysed these RV measurements and the TESS photometry. We excluded contaminating sources as the origin of the detected signal using high-angular-resolution speckle and adaptive optical imaging.<i>Results<i/>. We find that the parent star is a metal-poor ([Fe/H] = −0.27 ± 0.07) G3 V star (<i>T<i/><sub>eff<sub/> = 5718 ± 50 K), with a radius of <i>R<i/><sub>*<sub/> = 1.082 ± 0.026 <i>R<i/><sub>⊙<sub/>, a mass of <i>M<i/><sub>⋆<sub/> = 0.901<sub>−0.037<sub/><sup>+0.055<sup/> <i>M<i/><sub>⊙<sub/> and an age of 10.2<sub>−3.3<sub/><sup>+2.5<sup/> Gyr. We confirm the planetary nature of the candidate, which can now be named TOI-5795 b. We estimate that the planet has an orbital period of <i>P<i/><sub>orb<sub/> = 6.1406325 ± 0.0000054 days and an orbital eccentricity compatible with zero. With a mass of 23.66<sub>−4.60<sub/><sup>+4.09<sup/> <i>M<i/><sub>⊕<sub/>, a radius of 5.62 ± 0.11 <i>R<i/><sub>⊕<sub/>, and an equilibrium temperature of 1136 ± 18 K, it can be considered a hot super-Neptune at the edge of the so-called Neptune desert. The transmission spectroscopy metric of TOI-5795 b is ≈100, which makes it an interesting target for probing the chemical composition of its atmosphere. We simulated planet-formation processes but found almost no successful matches to the observed planet’s mass and orbit, suggesting that post-formation dynamical events may have shaped its current state. We also performed an atmospheric-evolution study of TOI-5795 b, finding that this planet likely experienced significant atmospheric stripping due to prolonged high-energy irradiation from its parent star.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"2 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145103609","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Revisiting the proper motions of M31 and M33 using massive supergiant stars with Gaia DR3","authors":"Hao Wu, Yang Huang, Huawei Zhang, Qikang Feng","doi":"10.1051/0004-6361/202555477","DOIUrl":"https://doi.org/10.1051/0004-6361/202555477","url":null,"abstract":"The proper motions (PMs) of M31 and M33 are key to understanding the Local Group’s dynamical evolution. However, measurement discrepancies between <i>Gaia<i/> blue and red samples, regarding whether the transverse velocity is remarkable, introduce significant ambiguity. In this work, we remeasure the systemic PMs of M31 and M33 using massive supergiant stars from <i>Gaia<i/> Data Release 3. Clean disk tracers are selected via color–color diagrams, with foreground contaminants removed through kinematic and astrometric cuts. We identify the discrepancy in M31’s blue and red samples as arising from systematic differences between <i>Gaia<i/>’s five-parameter (5p) and six-parameter (6p) astrometric solutions. The 6p solution, applied to sources lacking accurate color information, relies on a pseudo-color approximation, leading to lower precision and larger uncertainties. Two key limitations of the 6p solution are: (1) degraded astrometric accuracy for very red sources (<i>G<i/><sub>BP<sub/> − <i>G<i/><sub>RP<sub/> > 2.6); (2) significant PM zero-point offsets. In our sample, red sources are dominated by the 6p solution, while blue sources include a substantial fraction of 5p sources; this mismatch drives the observed discrepancy. By excluding extreme red sources and calibrating PM zero-points separately for 5p and 6p sources using background quasars, we reduce the discrepancy, bringing blue and red measurements into agreement within 1<i>σ<i/>. We ultimately report the most robust <i>Gaia<i/>-based PMs using high-quality 5p sources. For M31, we obtain as yr<sup>−1<sup/>, consistent with, but more precise than, the HST result. For M33, we find that as yr<sup>−1<sup/>, which agrees with the VLBA measurement within 1.5<i>σ<i/>. These results support a first infall scenario for M33.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"102 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145103610","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"X-ray polarization in radio-quiet AGN: Insights from the wedge corona model using Monte Carlo simulations","authors":"D. Tagliacozzo, S. Bianchi, V. Gianolli, A. Gnarini, A. Marinucci, G. Matt, F. Ursini, W. Zhang","doi":"10.1051/0004-6361/202554138","DOIUrl":"https://doi.org/10.1051/0004-6361/202554138","url":null,"abstract":"In this study, we present novel calculations of X-ray polarization from radio-quiet and unobscured active galactic nuclei (AGNs) using the Monte Carlo code MONK, which includes all general and special relativity effects. Our geometric model, referred to as the “wedge corona”, features a homogeneous cloud of electrons characterized by an aspect ratio of h/r and a radius that extends down to the innermost stable circular orbit around the central black hole (BH). Adopting the physical parameters of the Seyfert galaxy NGC 4151 as a baseline, we investigated various geometric and physical configurations of the BH-corona-accretion disk (AD) system, such as the coronal opening angle, temperature, optical depth, BH spin, and the inner radius of the disk. Finally, we compared our calculations with results from the Imaging X-ray Polarimetry Explorer (IXPE) for NGC 4151, the only radio-quiet and unobscured AGN with significant polarization detected by IXPE, to constrain the system’s geometric parameters within the framework of the wedge corona model.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"26 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145083849","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Broadband radio study of the supernova remnant Kes 73","authors":"S. Loru, A. Ingallinera, A. Pellizzoni, E. Egron, C. Bordiu, G. Umana, C. Trigilio, F. Bufano, M. N. Iacolina, M. Marongiu, S. Mulas, C. Buemi, F. Cavallaro, P. Leto, A. Melis, P. Reich, W. Reich, S. Riggi, A. C. Ruggeri","doi":"10.1051/0004-6361/202555932","DOIUrl":"https://doi.org/10.1051/0004-6361/202555932","url":null,"abstract":"<i>Context<i/>. Strong shocks occurring in supernova remnants (SNRs), and their interaction with an often anisotropic surrounding medium, make SNRs ideal laboratories for studying the production and acceleration of cosmic rays (CRs). Due to their complex morphology and phenomenology, different CR populations are expected to exist throughout the remnants, each characterized by its own energy spectrum. A comprehensive understanding of particle acceleration mechanisms and energetics in SNRs requires spatially resolved spectral and morphological studies.<i>Aims<i/>. We want to highlight the crucial role of high-resolution radio images at high frequencies (≳10 GHz) for studying the spectral properties of different remnant regions and better constraining the models that describe their non-thermal emission from radio to <i>γ<i/>-ray wavelengths.<i>Methods<i/>. We studied the integrated radio spectrum of the SNR Kes 73 using single-dish observations performed with the Sardinia Radio Telescope (SRT) between 6.9 and 24.8 GHz, complemented by published data. The high-resolution map at 24.8 GHz was used to search for spatial variations in the spectral index across the remnant.<i>Results<i/>. We present the SRT images of Kes 73, providing the highest-frequency morphological and spectral characterization ever obtained for this source. By combining our 18.7 and 24.8 GHz maps with previously published interferometric images at 1.4 and 5 GHz, we identify a flatter spectrum in the western bright region compared to the rest of the shell. In the same region, we detect overlapping <sup>12<sup/>CO molecular emission and <i>γ<i/>-ray radiation, providing strong evidence of SNR–molecular cloud interaction and enhanced CR production. We modelled the non-thermal radio to <i>γ<i/>-ray emission from this region, favouring a lepto-hadronic scenario with a maximum electron energy of 1.1 TeV and a magnetic field strength of 25 μG.<i>Conclusions<i/>. The spatial coincidence of the radio-bright, flat-spectrum region with the <sup>12<sup/>CO emission, together with the preferred lepto-hadronic model, strongly supports an ongoing interaction between the Kes 73 shock front and nearby molecular clouds.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"76 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145077777","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}