Astronomy & Astrophysics最新文献

{"title":"The nature of Martian plume during solar wind interaction with Mars","authors":"Yuchen Cao, Haoyu Lu, Jinbin Cao, Shibang Li, Yihui Song, Nihan Chen, Jianxuan Wang, Jianing Zhao, Bingzhao Li","doi":"10.1051/0004-6361/202452882","DOIUrl":"https://doi.org/10.1051/0004-6361/202452882","url":null,"abstract":"Investigating the physical mechanism of ion escape on Mars is crucial for comprehending the evolution of Martian space environment. The plume structure located in the +E hemisphere of Mars plays a crucial role in the escape of planetary ions, contributing more than 20 percent to the overall ion escape rate. In this study, a three-dimensional multi-fluid Hall magnetohydrodynamics (MHD) numerical model is utilized to simulate the ion escape process of Mars. A force analysis is conducted to examine the electric field exerted on O<sup>+<sup/> and to investigate the density, velocity, and escape flux of O<sup>+<sup/>. Numerical results indicate that both the convection field and the magnetic force field play essential roles in driving ion escape in the plume region and shaping the morphology of ion escaping fluxes. The plume is positioned above the magnetic pile-up boundary (MPB), as the convection field directed towards the +<i>Z<i/> direction primarily influences the area above the MPB. Furthermore, the Hall field points outward and reaches the peak values at the MPB, while the ambipolar field peaks at the bow shock (BS). In addition, the ions escaping from the plume predominantly originates from the middle and high latitudes of the +E hemisphere on the Martian dayside. The plume escape rate and the tail escape rate are 4.33 × 10<sup>23<sup/> s<sup>−1<sup/> and 1.74 × 10<sup>24<sup/> s<sup>−1<sup/> respectively. The plume escape rate accounts for 24.83% of the tail escape rate and 19.89% of the overall escape rate.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"51 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143933453","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":"A multiscale view of the magnetic field morphology in the hot molecular core G31.41+0.31","authors":"C. Y. Law, M. T. Beltrán, R. S. Furuya, J. M. Girart, D. Galli, R. Cesaroni, L. Moscadelli, D. Arzoumanian, A. Lorenzani, M. Padovani, A. Sanna, G. Surcis","doi":"10.1051/0004-6361/202453510","DOIUrl":"https://doi.org/10.1051/0004-6361/202453510","url":null,"abstract":"Multiscale studies of the morphology and strength of the magnetic field are crucial to properly unveil its role and relative importance in high-mass star and cluster formation. G31.41+0.31 (G31) is a hub-filament system that hosts a high-mass protocluster embedded in a hot molecular core (HMC). G31 is one of the few sources showing a clear hourglass morphology of the magnetic field on scales between 1000 au and a few 100 au in previous interferometric observations. This strongly suggests a field-regulated collapse. To complete the study of the magnetic field properties in this high-mass star-forming region, we carried out observations with the James Clerk Maxwell Telescope 850 μm of the polarized dust emission. These observations had a spatial resolution of ∼0.2 pc at 3.75 kpc. The aim was to study the magnetic field in the whole cloud and to compare the magnetic field orientation toward the HMC from ∼50 000 au to ∼260 au scales. The large-scale (∼5 pc) orientation of the magnetic field toward the position of the HMC is consistent with that observed at the core (∼4000 au) and circumstellar (∼260 au) scales. The self-similarity of the magnetic field orientation at these different scales might arise from the brightest sources in the protocluster, whose collapse is dragging the magnetic field. These sources dominate the gravitational potential and the collapse in the HMC. The cloud-scale magnetic field strength of the G31 hub-filament system, which we estimated using the Davis-Chandrasekhar-Fermi method, is in the range 0.04–0.09 mG. The magnetic field orientation in the star-forming region shows a bimodal distribution, and it changes from an NW–SE direction in the north to an E–W direction in the south. The change in the orientation occurs in the close vicinity of the HMC. This favors a scenario of a cloud-cloud collision for the formation of this star-forming region. The different magnetic field orientations would be the remnant of the pristine orientations of the colliding clouds in this scenario.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"2 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143933493","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 and radio data obtained by XMM-Newton and VLA constrain the stellar wind of the magnetic quasi-Wolf-Rayet star in HD45166","authors":"P. Leto, L. M. Oskinova, T. Shenar, G. A. Wade, S. Owocki, C. S. Buemi, R. Ignace, C. Trigilio, G. Umana, A. ud-Doula, H. Todt, W. -R. Hamann","doi":"10.1051/0004-6361/202452899","DOIUrl":"https://doi.org/10.1051/0004-6361/202452899","url":null,"abstract":"<i>Context.<i/> Recently, a powerful magnetic field was discovered in the hot helium star classified as a quasi-Wolf-Rayet (qWR) star (∼2 M<sub>⊙<sub/>), in the HD 45166 system. Upon its explosion as a core-collapse supernova, it is expected to produce a strongly magnetic neutron star – a magnetar. Among the key parameters that govern pre-supernova evolution is the amount of mass lost via stellar wind. However, the magnetic nature of this helium star is expected to affect its stellar wind, which makes the estimation of the wind parameters uncertain.<i>Aims.<i/> We report the first observations of HD 45166 in X-rays with the <i>XMM-Newton<i/> telescope and in radio with the VLA interferometer array. By placing the observation results in a theoretical framework, we aim to provide a reliable estimate of the wind strength of the magnetic qWR star.<i>Methods.<i/> We explain the X-ray properties in the framework of the magnetically confined wind shock scenario, and we apply the semianalytic model of a dynamical magnetosphere (DM) to reproduce the X-ray emission. We compute the thermal radio emission of the wind and its absorption effect on possible gyro-synchrotron emission from the underlying dipolar magnetosphere, sampled in 3D, by integrating the radiative transfer equation.<i>Results.<i/> We did not detect radio emissions, which enabled us to set sensitive upper limits on the radio luminosity. The magnetic qWR star is a slow rotator, and comparison with models reveals that the possible acceleration mechanisms that occur within its DM are not as efficient as in fast-rotating magnetic ApBp-type stars. In contrast, the system is detected in X-rays with log(<i>L<i/><sub>X<sub/>/<i>L<i/><sub>bol<sub/>)∼−5.6. Using suitable models, we constrain the mass lost from this magnetic quasi-Wolf-Rayet star as <i>Ṁ<i/> ≈ 3 × 10<sup>−10<sup/> M<sub>⊙<sub/> yr<sup>−1<sup/>.<i>Conclusions.<i/> This novel empirical estimate of the mass-loss rate in a ∼2 M<sub>⊙<sub/> helium star confirms that it maintains super-Chandrasekhar mass until collapse and can produce a magnetar as its final evolutionary product.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"38 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143933495","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":"Improving the spatial resolution of SDO/HMI transverse and line-of-sight magnetograms using GST/NIRIS data with machine learning","authors":"Chunhui Xu, Yan Xu, Jason T. L. Wang, Qin Li, Haimin Wang","doi":"10.1051/0004-6361/202453581","DOIUrl":"https://doi.org/10.1051/0004-6361/202453581","url":null,"abstract":"<i>Context.<i/> High-resolution magnetograms are crucial for studying solar flare dynamics because they enable the precise tracking of magnetic structures and rapid field changes. The Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory (SDO/HMI) has been an essential provider of vector magnetograms. However, the spatial resolution of the HMI magnetograms is limited and hence is not able to capture the fine structures that are essential for understanding flare precursors. The Near InfraRed Imaging Spectropolarimeter on the 1.6 m Goode Solar Telescope (GST/NIRIS) at Big Bear Solar Observatory (BBSO) provides a better spatial resolution and is therefore more suitable to track the fine magnetic features and their connection to flare precursors.<i>Aims.<i/> We propose DeepHMI, a machine-learning method for solar image super-resolution, to enhance the transverse and line-of-sight magnetograms of solar active regions (ARs) collected by SDO/HMI to better capture the fine-scale magnetic structures that are crucial for understanding solar flare dynamics. The enhanced HMI magnetograms can also be used to study spicules, sunspot light bridges and magnetic outbreaks, for which high-resolution data are essential.<i>Methods.<i/> DeepHMI employs a conditional diffusion model that is trained using ground-truth images obtained by an inversion analysis of Stokes measurements collected by GST/NIRIS.<i>Results.<i/> Our experiments show that DeepHMI performs better than the commonly used bicubic interpolation method in terms of four evaluation metrics. In addition, we demonstrate the ability of DeepHMI through a case study of the enhancement of SDO/HMI transverse and line-of-sight magnetograms of AR 12371 to GST/NIRIS data.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"5 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143933497","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":"Broad-band noises in GX 339-4 during the 2021 outburst observed with Insight-HXMT and NICER","authors":"Yong-Jie Jin, Xiao Chen, Hai-Fan Zhu, Ze-Jun Jiang, Wei Wang","doi":"10.1051/0004-6361/202453494","DOIUrl":"https://doi.org/10.1051/0004-6361/202453494","url":null,"abstract":"Rapid X-ray variability of GX 339−4 including the low-frequency quasi-periodic oscillations (LFQPOs) and broad-band noises were observed with the Hard X-ray Modulation Telescope (Insight-HXMT) and Neutron star Interior Composition Explorer (NICER) during the 2021 outburst. Here we present a systematic study of the evolution and energy dependence properties of such broad-band noises (BBNs). The outburst from February to March of 2021 can be divided into three stages: the low hard state (LHS), the hard intermediate state (HIMS), and soft intermediate state (SIMS). In the PDSs of the LHS and HIMS, the broad-band noises were well fitted with three Lorentzian components: a low-frequency component <i>L<i/><sub>1<sub/>, a middle-frequency component <i>L<i/><sub>2<sub/>, and a high-frequency component <i>L<i/><sub>3<sub/>. The increasing trend of the characteristic frequencies for <i>L<i/><sub>1<sub/> and <i>L<i/><sub>2<sub/> and the relation between the QPO frequency and characteristic BBN frequency are reported. We find that the energies corresponding to the peaks and shapes of the rms spectra for three BBN components are different. The comparison among three BBN components indicates that energy-dominant bands of these BBN components are distinct. Our results can be explained with the truncated disc and hot flow model with a large variable disc and a small hot inner flow. A possible description of the accretion structure and its evolution from the LHS to the SIMS is proposed. Further research is still required to probe such an accretion structure in GX 339-4.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"67 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143933451","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 CIELO project: The chemo-dynamical properties of galaxies and the cosmic web","authors":"Patricia B. Tissera, Lucas Bignone, Jenny Gonzalez-Jara, Ignacio Muñoz-Escobar, Pedro Cataldi, Valentina P. Miranda, Daniela Barrientos-Acevedo, Brian Tapia-Contreras, Susana Pedrosa, Nelson Padilla, Rosa Dominguez-Tenreiro, Catalina Casanueva-Villarreal, Emanuel Sillero, Benjamin Silva-Mella, Isha Shailesh, Francisco Jara-Ferreira","doi":"10.1051/0004-6361/202453348","DOIUrl":"https://doi.org/10.1051/0004-6361/202453348","url":null,"abstract":"<i>Context.<i/> The CIELO project introduces a novel set of chemo-dynamical zoom-in simulations, designed to simultaneously resolve galaxies and their nearby environments. The initial conditions (ICs) encompass a diverse range of cosmic structures, including local groups, filaments, voids, and walls, enabling a detailed exploration of galaxies within their broader cosmic web context.<i>Aims.<i/> This study aims to present the ICs and characterise the global properties of CIELO galaxies and their environments. Specifically, it focuses on galaxies with stellar masses ranging from 10<sup>8<sup/> to 10<sup>11<sup/> M<sub>⊙<sub/> and investigates key scaling relations, such as the mass-size relation, the Tully-Fisher relation (TFR), and the mass-metallicity relation (MZR) for both stars and star-forming gas.<i>Methods.<i/> We employed the DisPerSe algorithm to determine the positions of CIELO galaxies within the cosmic web, with a particular focus on the Pehuen haloes. The selection of Local Group (LG) type volumes was guided by criteria based on relative positions and velocities of the two primary galaxies. The Pehuen regions were selected to map walls, filaments and voids. Synthetic SDSS i, r, and g band images were generated using the SKIRT radiative transfer code. Furthermore, a dynamical decomposition was performed to classify galaxy morphologies into bulge, disc, and stellar halo components.<i>Results.<i/> The CIELO galaxies exhibit stellar-to-dark matter fractions consistent with both observational data and other simulation results. These galaxies align with expected scaling relations, such as the mass-size relation and TFR, indicating effective regulation of star formation and feedback processes. The mass-size relation reveals the expected dependence on galaxy morphology. The gas and stellar MZRs also agree well with observational data, with the stellar MZR displaying strong correlations with galaxy size (R<sub>hm<sub/>) and star formation rate (SFR). This indicates that smaller, less star-forming galaxies tend to have higher metallicities. Future investigations will delve into the chemo-dynamical properties of bulges, discs, and stellar haloes, exploring their connections to assembly histories and positions within the cosmic web.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"28 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143933494","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":"A search for the three isomers of cyano-1,3-butadiene in TMC-1: Implications for bottom-up routes involving 1,3-butadiene⋆","authors":"M. Agúndez, C. Cabezas, N. Marcelino, B. Tercero, R. Fuentetaja, P. de Vicente, J. Cernicharo","doi":"10.1051/0004-6361/202554343","DOIUrl":"https://doi.org/10.1051/0004-6361/202554343","url":null,"abstract":"The molecule 1,3-butadiene (CH<sub>2<sub/>CHCHCH<sub>2<sub/>) could play a key role in the synthesis of the cyclic molecules cyclopentadiene and benzene in cold dense clouds. Since 1,3-butadiene is non-polar, we searched for its cyano derivative, which exists in the form of three different polar isomers, in the cold dense cloud TMC-1. We used the most recent data obtained with the Yebes 40 m telescope in the Q band (31.0−50.3 GHz) in the frame of the QUIJOTE project. We did not detect either of the isomers of 1-cyano-1,3-butadiene, and we derive 3 <i>σ<i/> upper limits to their column densities of 1.2 × 10<sup>10<sup/> cm<sup>−2<sup/> and 2.0 × 10<sup>10<sup/> cm<sup>−2<sup/> for <i>E<i/>- and <i>Z<i/>-1-cyano-1,3-butadiene, respectively. Our results are not consistent with those from , ApJ, 948, 133), who determine a column density of 3.8 × 10<sup>10<sup/> cm<sup>−2<sup/> for <i>E<i/>-1-cyano-1,3-butadiene in TMC-1 using GBT data and a line stack technique. At the current level of sensitivity of our data, there is tentative evidence for the presence of the third cyano derivative isomer, 2-cyano-1,3-butadiene, although a firm detection must await more sensitive data. We derive an upper limit to its column density of 3.1 × 10<sup>10<sup/> cm<sup>−2<sup/>. This isomer cannot be formed in the reaction between CN and 1,3-butadiene, according to experimental and theoretical studies, and thus we speculate whether it could arise from neutral-neutral reactions, such as C<sub>2<sub/> H<sub>3<sub/>+CH<sub>2<sub/> CHCN and CH<sub>2<sub/> CCN+C<sub>2<sub/> H<sub>4<sub/>. From the upper limit on the abundance of 1-cyano-1,3-butadiene derived here, we estimate that the abundance of 1,3-butadiene in TMC-1 is below 10<sup>−11<sup/>−10<sup>−10<sup/> relative to H<sub>2<sub/>. The low abundance inferred for 1,3-butadiene makes it unlikely that it plays an important role in bottom-up routes to cyclopentadiene and benzene.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"17 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143933496","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":"Understanding the baryon cycle: Fueling star formation via inflows in Milky Way-like galaxies","authors":"Filippo Barbani, Raffaele Pascale, Federico Marinacci, Paul Torrey, Laura V. Sales, Hui Li, Mark Vogelsberger","doi":"10.1051/0004-6361/202452608","DOIUrl":"https://doi.org/10.1051/0004-6361/202452608","url":null,"abstract":"<i>Context.<i/> Galaxies are not isolated systems, as they interact with their surroundings throughout their lifetimes by both ejecting gas via stellar feedback and accreting gas from their environment. Understanding the interplay between the gas ejected from the disc and the circumgalactic medium (CGM) is crucial to learning how star-forming galaxies evolve.<i>Aims.<i/> Our goal is to understand how gas in the CGM is accreted onto the inner regions of the star-forming disc, making it available for the formation of new stars. Specifically, we explore the connection between stellar feedback and gas accretion from the CGM in Milky Way-like galaxies, aiming to unveil the complex mechanisms driving the evolution of star-forming galaxies. We focus on the distribution of vertical and radial gas flows to and from the disc as a function of galactocentric radius and examine the implications of these processes for the evolution of such galaxies.<i>Methods.<i/> We used the moving-mesh code AREPO coupled with the <i>SMUGGLE<i/> sub-grid model to perform hydrodynamic <i>N<i/>-body simulations of nine different galaxies surrounded by a hot (<i>T<i/> ∼ 10<sup>6<sup/> K) CGM (also called galactic corona). Each simulation has a different structure of the gaseous disc in terms of mass and scale length, which allows us to study how the dynamics of the gas can be affected by disc structure.<i>Results.<i/> We find evidence of a crucial link between stellar feedback processes and gas accretion from the CGM, which collectively play an essential role in sustaining ongoing star formation in the disc. In particular, the ejection of gas from the plane of the disc by stellar feedback leads to the generation of a baryon cycle where the CGM gas is preferentially accreted onto the external regions of the disc (≈3 − 10 M<sub>⊙<sub/> yr<sup>−1<sup/> of gas is accreted into the entire disc). From these regions, it is then transported to the centre with radial mass rates of ≈1 − 4 M<sub>⊙<sub/> yr<sup>−1<sup/> on average, owing to angular momentum conservation. It then leads to the formation of new stars and restarts the whole cycle. We find that both vertical accretion onto the inner regions of the disc and the radial transport of gas from the disc outskirts are necessary to sustain star formation.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"119 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143933498","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":"Three-dimensional non-LTE radiative transfer effects in Fe I lines","authors":"R. Holzreuter, H. N. Smitha, S. K. Solanki","doi":"10.1051/0004-6361/202553965","DOIUrl":"https://doi.org/10.1051/0004-6361/202553965","url":null,"abstract":"<i>Context.<i/> In the first three papers of this series, we investigated the formation of photospheric neutral iron lines in different atmospheres ranging from idealized flux tube models to complex three-dimensional magneto-hydrodynamic (3D MHD) simulations. The overarching goal was to understand the role of non-local thermodynamic equilibrium (NLTE) and horizontal radiative transfer (RT) effects in the formation of these lines.<i>Aims.<i/> In the present paper, we extend this investigation using a high-resolution MHD simulation, with a grid spacing much smaller than the scales currently resolvable by telescopes. We aim to understand whether the horizontal RT effects imposes an intrinsic limit on the small-scale structures that can be observed by telescopes, by spatially smearing out these structures in the solar atmosphere.<i>Methods.<i/> We synthesized the Stokes profiles of two iron line pairs, one at 525 nm and other at 630 nm in 3D NLTE. We compared our results with the ones in previous papers and checked the impact of horizontal transfer on the quality of the images.<i>Results.<i/> Our results with the high-resolution simulations align with the ones inferred from lower-resolution simulations in the previous papers of this series. The spatial smearing due to horizontal RT, although present, is quite small. The degradation caused by the point spread function of a telescope is much stronger.<i>Conclusions.<i/> In the photospheric layers, we do not see an image degradation caused by horizontal RT that is large enough to smear out the small-scale structures in the simulation box. The current generation of telescopes with spatial resolutions smaller than the horizontal photon mean free path should in principle be able to observe the small-scale structures, at least in the photosphere.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"1 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143933450","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":"Neutrinos from stochastic acceleration in black hole environments","authors":"Martin Lemoine, Frank Rieger","doi":"10.1051/0004-6361/202453296","DOIUrl":"https://doi.org/10.1051/0004-6361/202453296","url":null,"abstract":"Recent experimental results from the IceCube detector and their phenomenological interpretation suggest that the magnetized turbulent corona of nearby X-ray luminous Seyfert galaxies can produce ∼1 − 10 TeV neutrinos via photo-hadronic interactions. We investigate the physics of stochastic acceleration in these environments in detail and examine the conditions under which the inferred proton spectrum can be explained. To this end, we used recent findings on particle acceleration in turbulence and paid particular attention to the transport equation, notably for transport in momentum space, turbulent transport outside of the corona, and advection through the corona. We first remark that the spectra we obtained are highly sensitive to the value of the acceleration rate, for instance, to the Alfvénic velocity. Then, we examined three prototype scenarios, one scenario of turbulent acceleration in the test-particle picture, another scenario in which particles were preaccelerated by turbulence and further energized by shear acceleration, and a final scenario in which we considered the effect of particle backreaction on the turbulence (damping), which self-regulates the acceleration process. We show that it is possible to obtain satisfactory fits to the inferred proton spectrum in all three cases, but we stress that in the first two scenarios, the energy content in suprathermal protons has to be fixed in an ad hoc manner to match the inferred spectrum at an energy density close to that contained in the turbulence. Interestingly, self-regulated acceleration by turbulence damping naturally brings the suprathermal particle energy content close to that of the turbulence and allowed us to reproduce the inferred flux level without additional fine-tuning. We also suggest that based on the strong sensitivity of the highest proton energy to the Alfvénic velocity (or acceleration rate), any variation in this quantity in the corona might affect (and in fact, set) the slope of the high-energy proton spectrum.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"5 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143933456","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}