Astronomy & Astrophysics最新文献

{"title":"Global Hall-magnetohydrodynamic simulations of transition disks","authors":"Eleftheria Sarafidou, Oliver Gressel, Barbara Ercolano","doi":"10.1051/0004-6361/202452121","DOIUrl":"https://doi.org/10.1051/0004-6361/202452121","url":null,"abstract":"<i>Context.<i/> Transition disks (TDs) are a type of protoplanetary disk characterized by a central dust and gas cavity. The processes behind how these cavities are formed and maintained, along with their observed high accretion rates of 10<sup>−8<sup/>−10<sup>−7<sup/> <i>M<i/><sub>⊙<sub/> yr<sup>−1<sup/>, continue to be subjects of active research.<i>Aims.<i/> This work aims to investigate how the inclusion of the Hall effect (HE) alongside Ohmic resistivity (OR) and ambipolar diffusion (AD) affects the structure of the TD. Of key interest is the dynamical evolution of the cavity and whether it can indeed produce transonic accretion, as predicted by theoretical models in order to account for the observed high accretion rates despite the inner disk’s low density.<i>Methods.<i/> We present our results of 2D axisymmetric global radiation magnetohydrodynamic (MHD) simulations of TDs for which all three non ideal MHD effects are accounted. We used the NIRVANA-III fluid code and initialized our model with a disk cavity reaching up to <i>R<i/> = 8 au with a density contrast of 10<sup>5<sup/> . We performed three runs, one with only OR and AD, and one for each of the two configurations that arise when additionally including the HE, that is, with the field aligned (anti-aligned) with respect to the rotation axis.<i>Results.<i/> For all three runs, our models maintain an intact inner cavity and an outer standard disk. MHD winds are launched both from the cavity and from the disk. Notably, when the HE is included, ring-like structures develop within the cavity. We moreover obtain accretion rates of 3−8 × 10<sup>−8<sup/> <i>M<i/><sub>⊙<sub/> yr<sup>−1<sup/>, comparable to typical values seen in full disks. Importantly, we clearly observe (tran)sonic accretion (<i>v<i/><sub>acc<sub/> ≳ <i>c<i/><sub>s<sub/>) in the cavity. Additionally, outward magnetic flux transport occurs in all three runs.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"103 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143737137","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 theoretical pulsation spectra of hot B subdwarfs","authors":"N. Guyot, V. Van Grootel, S. Charpinet, M. Farnir, M.-A. Dupret, P. Brassard","doi":"10.1051/0004-6361/202452423","DOIUrl":"https://doi.org/10.1051/0004-6361/202452423","url":null,"abstract":"<i>Context.<i/> The <i>Kepler<i/> and TESS space missions have revealed the rich gravity (<i>g<i/>-)mode pulsation spectra of many hot subdwarf B (sdB) stars in detail. These spectra exhibit complex behaviors, with some stars exhibiting trapped modes interposing in the asymptotic period sequences of regular period spacing, while others do not.<i>Aims.<i/> We aim to thoroughly compute theoretical <i>g<i/>-mode pulsation spectra, using our current sdB models, useful for future reference when comparing to observations. This also enables us to explore relationships with features of the internal structure of these stars. Such studies provide guidance in conducting future asteroseismic analyses of these pulsators and insights on how to interpret their outcomes.<i>Methods.<i/> We used our STELlar modeling from the Université de Montréal (STELUM) code to compute static (parametric) and evolutionary models of sdB stars, with different prescriptions for their chemical and thermal structures. We used our adiabatic PULSE code to compute the theoretical spectra of <i>g<i/>-mode pulsations for degrees of <i>ℓ<i/> = 1 to 4 and for periods between 1000 s and 15 000 s, amply covering the range of observed <i>g<i/>-modes in these stars.<i>Results.<i/> We show that <i>g<i/>-mode pulsation spectra and, in particular, the appearance of trapped modes are highly dependent on the chemical and thermal structures in the models as the star evolves, particularly in the region just above the He-burning core. Depending on the prescriptions and specific evolutionary stage, we observe mainly three types of spectra for mid to high radial-order <i>g<i/>-modes (the ones observed in sdB stars): “flat” spectra of nearly constant period spacing; spectra with deep minima of the period spacing interposing between modes with more regular spacing (which correspond to trapped modes); and spectra showing a “wavy” pattern in period spacing. For the two latter cases, we have identified the region where the modes are trapped in the star.<i>Conclusions.<i/> Detailed comparisons with observed <i>g<i/>-mode spectra ought to be carried out next to progress on this issue and constrain the internal structure of core-He burning stars via asteroseismology, in particular, for the region above the He-burning core.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"15 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143736901","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":"An effective model for magnetic field amplification by the magnetorotational and parasitic instabilities","authors":"Miquel Miravet-Tenés, Martin E. Pessah","doi":"10.1051/0004-6361/202452953","DOIUrl":"https://doi.org/10.1051/0004-6361/202452953","url":null,"abstract":"The magnetorotational instability (MRI) is considered a leading mechanism for driving angular momentum transport in differentially rotating astrophysical flows, including accretion disks and protoneutron stars. This process is mediated by the exponential amplification of the magnetic field whose final amplitude is envisioned to be limited by secondary (parasitic) instabilities. In this paper, we investigated the saturation of the MRI via parasitic modes relaxing previous approximations. We carried out the first systematic analysis of the evolution of parasitic modes as they feed off the exponentially growing MRI while being advected by the background shear flow. We provide the most accurate calculation of the amplification factor to which the MRI can grow before the fastest parasitic modes reach a comparable amplitude. We find that this amplification factor is remarkably robust, depending only logarithmically on the initial amplitude of the parasitic modes, in reasonable agreement with numerical simulations. Based on these insights, and guided by numerical simulations, we provide a simple analytical expression for the amplification of magnetic fields responsible for MRI-driven angular momentum transport. Our effective model for magnetic field amplification may enable going beyond the standard prescription for viscous transport currently employed in numerical simulations when the MRI cannot be explicitly resolved.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"5 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143736902","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":"Making the unmodulated pyramid wavefront sensor smart","authors":"R. Landman, S. Y. Haffert, J. D. Long, J. R. Males, L. M. Close, W. B. Foster, K. Van Gorkom, O. Guyon, A. D. Hedglen, P. T. Johnson, M. Y. Kautz, J. K. Kueny, J. Li, J. Liberman, J. Lumbres, E. A. McEwen, A. McLeod, L. Schatz, E. Tonucci, K. Twitchell","doi":"10.1051/0004-6361/202553753","DOIUrl":"https://doi.org/10.1051/0004-6361/202553753","url":null,"abstract":"Pyramid wavefront sensors (PWFSs) are the preferred choice for current and future extreme adaptive optics (XAO) systems. Almost all instruments use the PWFS in its modulated form to mitigate its limited linearity range. However, this modulation comes at the cost of a reduction in sensitivity, a blindness to petal-piston modes, and a limit to the sensor’s ability to operate at high speeds. Therefore, there is strong interest to use the PWFS without modulation, which can be enabled with nonlinear reconstructors. Here, we present the first on-sky demonstration of XAO with an unmodulated PWFS using a nonlinear reconstructor based on convolutional neural networks. We discuss the real-time implementation on the Magellan Adaptive Optics eXtreme (MagAO-X) instrument using the optimized TensorRT framework and show that inference is fast enough to run the control loop at > 2 kHz frequencies. Our on-sky results demonstrate a successful closed-loop operation using a model calibrated with internal source data that delivers stable and robust correction under varying conditions. Performance analysis reveals that our smart PWFS achieves nearly the same Strehl ratio as the highly optimized modulated PWFS under favorable conditions on bright stars. Notably, we observe an improvement in performance on a fainter star under the influence of strong winds. These findings confirm the feasibility of using the PWFS in its unmodulated form and highlight its potential for next-generation instruments. Future efforts will focus on achieving even higher control loop frequencies (> 3 kHz), optimizing the calibration procedures, and testing its performance on fainter stars, where more gain is expected for the unmodulated PWFS compared to its modulated counterpart.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"65 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143736834","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":"ALMA observations of CH3COCH3 and the related species CH3CHO, CH3OH, and C2H5CN in line-rich molecular cores","authors":"Chuanshou Li, Sheng-Li Qin, Tie Liu, Xunchuan Liu, Xiaohu Li, Li Chen, Hong-Li Liu, Fengwei Xu, Meizhu Liu, Mengyao Tang, Hongqiong Shi, Tianwei Zhang, Yuefang Wu","doi":"10.1051/0004-6361/202452810","DOIUrl":"https://doi.org/10.1051/0004-6361/202452810","url":null,"abstract":"<i>Context<i/>. Acetone (CH<sub>3<sub/>COCH<sub>3<sub/>) is a carbonyl-bearing complex organic molecule, yet interstellar observations of acetone remain limited. Studying the formation and distribution of CH<sub>3<sub/>COCH<sub>3<sub/> in the interstellar medium can provide valuable insights into prebiotic chemistry and the evolution of interstellar molecules.<i>Aims<i/>. We explore the spatial distribution of CH<sub>3<sub/>COCH<sub>3<sub/> and its correlation with the O-bearing molecules acetaldehyde (CH<sub>3<sub/>CHO) and methanol (CH<sub>3<sub/>OH), as well as the N-bearing molecule ethyl cyanide (C<sub>2<sub/>H<sub>5<sub/>CN), in massive protostellar clumps.<i>Methods<i/>. We observed 11 massive protostellar clumps using ALMA at 345 GHz, with an angular resolution of 0.7′′−1.0′′. Spectral line transitions were identified using the eXtended CASA Line Analysis Software Suite. We constructed integrated intensity maps of CH<sub>3<sub/>COCH<sub>3<sub/>, CH<sub>3<sub/>CHO, CH<sub>3<sub/>OH, and C<sub>2<sub/>H<sub>5<sub/>CN and derived their rotation temperatures, column densities, and abundances under the assumption of local thermodynamic equilibrium.<i>Results<i/>. CH<sub>3<sub/>COCH<sub>3<sub/> is detected in 16 line-rich cores from 9 massive protostellar clumps: 12 high-mass cores (core mass >8 M<sub>⊙<sub/>), 3 intermediate-mass cores (2–8 M<sub>⊙<sub/>), and 1 low-mass core (<2 M<sub>⊙<sub/>). CH<sub>3<sub/>CHO and CH<sub>3<sub/>OH are also detected in all 16 cores, while C<sub>2<sub/>H<sub>5<sub/>CN is detected in 15. The integrated intensity maps reveal similar spatial distributions for CH<sub>3<sub/>COCH<sub>3<sub/>, CH<sub>3<sub/>CHO, CH<sub>3<sub/>OH, and C<sub>2<sub/>H<sub>5<sub/>CN. The line emission peaks of all four molecules coincide with the continuum emission peaks in regions without ultra-compact HII regions. Significant correlations are observed in the abundances of these molecules, which also exhibit similar average temperatures.<i>Conclusions<i/>. Our observational results, supported by chemical models, suggest that CH<sub>3<sub/>COCH<sub>3<sub/>, CH<sub>3<sub/>CHO, and CH<sub>3<sub/>OH originate from the same gas. The observed temperatures and abundances of CH<sub>3<sub/>COCH<sub>3<sub/> are consistent with model predictions involving grain surface chemistry.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"72 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143736843","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":"Comparative study of small-scale magnetic fields on ξ Boo A using optical and near-infrared spectroscopy","authors":"A. Hahlin, O. Kochukhov, P. Chaturvedi, E. Guenther, A. Hatzes, U. Heiter, A. Lavail, E. Nagel, N. Piskunov, K. Pouilly, A. D. Rains, A. Reiners, M. Rengel, U. Seeman, D. Shulyak","doi":"10.1051/0004-6361/202453016","DOIUrl":"https://doi.org/10.1051/0004-6361/202453016","url":null,"abstract":"<i>Context.<i/> Magnetic field investigations of Sun-like stars, using Zeeman splitting of non-polarised spectra, in the optical and H-band have found significantly different magnetic field strengths for the same stars, the cause of which is currently unknown.<i>Aims.<i/> We aim to further investigate this issue by systematically analysing the magnetic field of ξ Boo A, a magnetically active G7 dwarf, using spectral lines at different wavelengths.<i>Methods.<i/> We used polarised radiative transfer accounting for the departures from local thermodynamic equilibrium to generate synthetic spectra. To find the magnetic field strengths in the optical, H-band, and K-band, we employed MCMC sampling analysis of high-resolution spectra observed with the spectrographs CRIRES<sup>+<sup/>, ESPaDOnS, NARVAL, and UVES. We also determine the formation depth of different lines by calculating the contribution functions for each line employed in the analysis.<i>Results.<i/> We find that the magnetic field strength discrepancy between lines in the optical and H-band persists even when treating the different wavelength regions consistently. In addition, the magnetic measurements derived from the K-band appear to more closely align with the optical. The H-band appears to yield magnetic field strengths ∼0.4 kG with a statistically significant variation while the optical and K-band is stable at ∼0.6 kG for observations spanning about two decades. The contribution functions reveal that the optical lines form at a significantly higher altitude in the photosphere compared to those in the H- and K-band.<i>Conclusions.<i/> While we find that the discrepancy remains, the variation of formation depths could indicate that the disagreement between magnetic field measurements obtained at different wavelengths is linked to the variation of the magnetic field along the line of sight and between different structures, such as star spots and faculae, in the stellar photosphere.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"45 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143736844","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":"Chromospherically active stars: Chemical composition of photospheres in 20 RS CVn stars","authors":"B. Bale, G. Tautvaišienė, R. Minkevičiūtė, A. Drazdauskas, Š. Mikolaitis, E. Stonkutė, M. Ambrosch","doi":"10.1051/0004-6361/202452780","DOIUrl":"https://doi.org/10.1051/0004-6361/202452780","url":null,"abstract":"<i>Context.<i/> Various element transport processes modify the photospheric chemical composition of low-mass stars during their evolution. The most prominent one is the first dredge-up that occurs at the beginning of the red giant branch. Then, various extra-mixing processes, such as those caused by thermohaline- and/or rotation-induced mixing, come into action. The extent of the influence of stellar magnetic activity on alterations in stellar chemical composition is among the least studied questions.<i>Aims.<i/> To investigate how magnetic activity influences mixing in the atmospheres of magnetically active stars, we carried out a detailed study of C, N, and up to ten other chemical element abundances, as well as carbon isotope ratios in a sample of RS CVn stars.<i>Methods.<i/> Using a differential model atmosphere method, we analysed high-resolution spectra that had been observed with the VUES spectrograph on the 1.65 m telescope at the Moletai Astronomical Observatory of Vilnius University. Carbon abundances were derived using the spectral synthesis of the C<sub>2<sub/> band heads at 5135 and 5635.5 Å. We analysed the wavelength intervals 6470–6490 Å and 7980–8005 Å with CN features to determine nitrogen abundances. Carbon isotope ratios were determined from the <sup>13<sup/>CN line at 8004.7 Å. Oxygen abundances were determined from the [O I] line at 6300 Å. Abundances of other chemical elements were determined from equivalent widths or spectral syntheses of unblended spectral lines.<i>Results.<i/> We determined the main atmospheric parameters and abundances of up to 12 chemical elements for a sample of 20 RS CVn giants that represented different evolutionary stages. We determined that *29 Dra, *b01 Cyg, and V* V834 Her, which are in the evolutionary stage below the red giant branch luminosity bump, already show evidence of extra-mixing in their lowered carbon isotope ratios.<i>Conclusions.<i/> We provide observational evidence that in low-mass chromospherically active RS CVn stars, due to their magnetic activity, extra-mixing processes may start acting below the luminosity bump of the red giant branch.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"73 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143736894","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":"Strong nebular He II emission induced by He+ ionizing photons escaping through the clumpy winds of massive stars","authors":"A. Roy, M. R. Krumholz, S. Salvadori, G. Meynet, S. Ekström, J. S. Vink, A. A. C. Sander, R. S. Sutherland, S. Paul, A. Pallottini, Á. Skúladóttir","doi":"10.1051/0004-6361/202553697","DOIUrl":"https://doi.org/10.1051/0004-6361/202553697","url":null,"abstract":"<i>Context.<i/> The origin of nebular He II emission in both local and high-redshift galaxies remains an unsolved problem. Various theories have been proposed to explain it, including He II-ionizing photons produced by high mass X-ray binaries, ultra-luminous X-ray sources, or “stripped” He stars produced by binary interaction or evolution of rapidly rotating (<i>v<i/>/<i>v<i/><sub>crit<sub/> ≫ 0.4) single massive stars, shock ionization, and hidden active galactic nuclei. All of these theories have shortcomings, however, leaving the cause of nebular He II emission unclear.<i>Aims.<i/> We investigate the hypothesis that the photons responsible for driving nebular He II emission are produced by the evolution of single massive stars and/or Wolf-Rayet (WR) stars whose winds are on the verge of becoming optically thin due to clumping, thus allowing significant escape of hard ionizing photons. We combined models of stellar evolution with population synthesis and nebular models to identify the most favorable scenarios for producing nebular He II via this channel.<i>Methods.<i/> We used the Modules for Experiments in Stellar Astrophysics (MESA) code to compute evolutionary tracks for stars with initial masses of 10 − 150 M<sub>⊙<sub/> and a range of initial metallicities and rotation rates. We then combined these tracks with a range of custom treatments of stellar atmospheres, which were intended to capture the effects of clumping, in the population synthesis code Stochastically Lighting Up Galaxies (SLUG) in order to produce the total ionizing photon budgets and spectra. We used these spectra as inputs to CLOUDY calculations of nebular emission at a range of nebular densities and metallicities.<i>Results.<i/> We find that if WR winds are clumpy enough to become close to optically thin, stellar populations with a wide range of metallicities and rotation rates can produce He II ionizing photons at rates sufficient to explain the observed nebular <i>I<i/>(He II)/<i>I<i/>(H<i>β<i/>) ratio ∼0.004 − 0.07 found in He II-emitting galaxies. Metal-poor rapidly rotating stellar populations ([Fe/H]= − 2.0, <i>v<i/>/<i>v<i/><sub>crit<sub/> = 0.4) also reach these levels of He II production, even for partially clumpy winds. These scenarios also yield He II, H<i>β<i/>, and “blue bump” line equivalent widths comparable to those observed in He II emitters. Only for homogeneous non-clumpy winds did we fail to find combinations of metallicity and stellar rotation rate that yield <i>I<i/>(He II)/<i>I<i/>(H<i>β<i/>) values as high as those observed in He II emitters.<i>Conclusions.<i/> Contrary to previous findings, we conclude that single WR stars can be a strong source for nebular He II emission if their winds are sufficiently clumpy. This scenario also reproduces a range of other properties found in He II emitters, suggesting that hard photons escaping through clumpy WR winds are a strong candidate to explain nebular He II-emission.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"31 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143736895","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 H.E.S.S. extragalactic sky survey with the first decade of observations","authors":"F. Aharonian, F. Ait Benkhali, J. Aschersleben, H. Ashkar, M. Backes, V. Barbosa Martins, R. Batzofin, Y. Becherini, D. Berge, K. Bernlöhr, M. Böttcher, C. Boisson, J. Bolmont, M. de Bony de Lavergne, J. Borowska, M. Bouyahiaoui, F. Bradascio, R. Brose, A. Brown, F. Brun, B. Bruno, T. Bulik, C. Burger-Scheidlin, T. Bylund, S. Casanova, J. Celic, M. Cerruti, T. Chand, S. Chandra, A. Chen, J. Chibueze, O. Chibueze, G. Cotter, P. Cristofari, J. D. Mbarubucyeye, I. D. Davids, J. Devin, J. Djuvsland, A. Dmytriiev, K. Egberts, S. Einecke, S. Fegan, G. Fontaine, S. Funk, S. Gabici, J. F. Glicenstein, J. Glombitza, P. Goswami, G. Grolleron, L. Haerer, B. Heß, J. A. Hinton, W. Hofmann, T. L. Holch, M. Holler, D. Horns, Zhiqiu Huang, M. Jamrozy, F. Jankowsky, A. Jardin-Blicq, E. Kasai, K. Katarzyński, R. Khatoon, B. Khélifi, Nu. Komin, K. Kosack, D. Kostunin, A. Kundu, R. G. Lang, S. Le Stum, A. Lemière, M. Lemoine-Goumard, J.-P. Lenain, F. Leuschner, A. Luashvili, J. Mackey, D. Malyshev, V. Marandon, G. Martí-Devesa, R. Marx, A. Mehta, A. Mitchell, R. Moderski, L. Mohrmann, A. Montanari, M. de Naurois, J. Niemiec, P. O’Brien, L. Olivera-Nieto, E. de Ona Wilhelmi, M. Ostrowski, S. Panny, M. Panter, U. Pensec, G. Pühlhofer, M. Punch, A. Quirrenbach, S. Ravikularaman, M. Regeard, A. Reimer, O. Reimer, I. Reis, H. Ren, B. Reville, F. Rieger, G. Rowell, B. Rudak, E. Ruiz-Velasco, V. Sahakian, H. Salzmann, D. A. Sanchez, A. Santangelo, M. Sasaki, J. Schäfer, F. Schüssler, J. N. S. Shapopi, A. Sharma, H. Sol, S. Spencer, Ł. Stawarz, R. Steenkamp, S. Steinmassl, C. Steppa, H. Suzuki, T. Takahashi, T. Tanaka, A. M. Taylor, R. Terrier, A. Thakur, M. Tsirou, C. van Eldik, M. Vecchi, C. Venter, J. Vink, H. J. Völk, T. Wach, S. J. Wagner, A. Wierzcholska, M. Zacharias, A. A. Zdziarski, A. Zech, N. Żywucka","doi":"10.1051/0004-6361/202452723","DOIUrl":"https://doi.org/10.1051/0004-6361/202452723","url":null,"abstract":"The results of the first extragalactic gamma-ray survey by the High Energy Stereoscopic System (H.E.S.S.) are presented. The survey comprises 2720 hours of very high-energy gamma-ray observations of the extragalactic sky, recorded with H.E.S.S. from 2004 up to the end of 2012. These data have been re-analysed using a common consistent set of up-to-date data calibration and analysis tools. From this analysis, a list of 23 detected objects, predominantly blazars, was obtained. This catalogue was assessed in terms of the source class populations that it contains. The level of source parameter bias for the blazar sources, probed by this observational dataset, was evaluated using Monte-Carlo simulations. Spectral results obtained with the H.E.S.S. data were compared with the <i>Fermi<i/>-LAT catalogues to present the full gamma-ray picture of the detected objects. Lastly, this unique dataset was used to assess the contribution of BL Lacertae objects and flat-spectrum radio quasars to the extragalactic gamma-ray background light at several hundreds of gigaelectronvolts. These results are accompanied by the release of the high-level data to the astrophysical community.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"20 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143737195","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":"Theoretical relations between model parameters and Metis observables for eruptive prominences and coronal mass ejections","authors":"S. Jejčič, P. Schwartz, P. Heinzel, S. Gunár","doi":"10.1051/0004-6361/202453116","DOIUrl":"https://doi.org/10.1051/0004-6361/202453116","url":null,"abstract":"<i>Context.<i/> We investigate the behavior of the plasma in eruptive prominences and coronal mass ejections in characteristic physical conditions.<i>Aims.<i/> We aim to demonstrate various relations between the plasma parameters and radiation properties relevant to Solar Orbiter and Metis observations.<i>Methods.<i/> Our method is based on 2D non-local thermodynamic equilibrium (non-LTE) modeling of moving structures that are externally illuminated from the solar disk. We have focused on temperatures below 10<sup>5<sup/> K and a range of gas pressures to investigate the opacity effects in the L<i>α<i/> line. Overall, we applied a large grid of isothermal and isobaric models.<i>Results.<i/> Our results are presented in the form of various correlation plots showing relationships between the plasma parameters and radiation properties relevant to Metis observations. We also demonstrate the relative importance of radiative and collisional ionization of hydrogen and the ratio between radiative and collisional excitation of the L<i>α<i/> line. Our results point to the need to carry out optically thick non-LTE modeling for specific plasma conditions. The visible light (<i>VL<i/>) emission was also obtained for the purposes of a comparison with the Metis data.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"5 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143737136","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}