Astronomy & Astrophysics最新文献

{"title":"Gas excitation in galaxies and active galactic nuclei with He IIλ4686 and X-ray emission","authors":"K. Kouroumpatzakis, J. Svoboda","doi":"10.1051/0004-6361/202453192","DOIUrl":"https://doi.org/10.1051/0004-6361/202453192","url":null,"abstract":"<i>Context.<i/> The origin of He II emission in galaxies remains a debated topic, requiring ionizing photons with energies exceeding 54 eV. While massive stars, such as Wolf-Rayet stars, have been considered potential sources, their UV flux often fails to fully explain the observed He II emission. Recent studies suggest that X-ray binaries (XRBs) might contribute significantly to this ionization.<i>Aims.<i/> We explore the relationship between X-ray and He II<i>λ<i/> 4686 emission in a statistically significant sample of galaxies, investigating whether X-ray sources, including active galactic nuclei (AGNs) and XRBs, serve as the primary mechanism for He II ionization across different galactic environments.<i>Methods.<i/> We cross-matched a sample of known well-detected He II galaxies with the Chandra Source Catalog, yielding 165 galaxies with X-ray and He II<i>λ<i/> 4686 detections. The sources were classified into star-forming galaxies (SFGs) and AGNs based on the BPT diagram and a classification scheme defined for He II galaxies. We analyzed the correlation between X-ray and He II luminosity across different energy bands and other parameters.<i>Results.<i/> The comparison between X-ray and He II luminosity shows a strong, linear correlation across AGNs and SFGs spanning over seven orders of magnitude. AGNs generally exhibit higher He II/H<i>β<i/> flux ratios, stronger extinction, and harder X-ray spectra. The O32 ratio of SFGs is tightly correlated with the H<i>β<i/> equivalent width (EW<sub>H<i>β<i/><sub/>) but not with the He II/H<i>β<i/> ratio, suggesting a different excitation mechanism. We derive an O32–EW<sub>H<i>β<i/><sub/> line above which only AGNs of our sample reside.<i>Conclusions.<i/> The tight correlation between X-ray and He II luminosity supports X-rays as the primary driver of He II excitation. While AGNs have one common ionization source, the central black hole, in SFGs low-energy species are mainly excited by UV emission related to star-forming activity, however, high-energy species like He II require the presence of XRBs.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"14 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143819745","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":"Oscillations of red giant stars with magnetic damping in the core","authors":"Jonas Müller, Quentin Coppée, Saskia Hekker","doi":"10.1051/0004-6361/202553888","DOIUrl":"https://doi.org/10.1051/0004-6361/202553888","url":null,"abstract":"Strong magnetic fields in the core of red-giant branch stars are expected to suppress the amplitudes of the multipole modes. This occurs when the strength of the internal magnetic field approaches the critical field strength, at which the magnetic forces become comparable to the buoyancy. We performed Hamiltonian ray tracing simulations of magneto-gravity waves to investigate the suppression of the multipole modes in the presence of an internal dipole-like magnetic field. We took into account different stellar masses, metallicities, and ages, as well as various oscillation frequencies and spherical degrees. In particular, we estimated the trapped fraction, a measure of multipole mode suppression, which quantifies the fraction of mode energy in the core that is dissipated by the interaction with the magnetic field. Our results indicate that the trapped fraction can be described by a simple expression, which smoothly connects the regime without multipole mode suppression with the regime with complete suppression of the multipole modes. Crucially, the trapped fraction depends only on the ratio between the strength of the internal magnetic field and the critical field strength. Therefore, our expression for the trapped fraction provides a flexible tool that can be used, for example, to estimate the amount of multipole mode suppression as a star ascends the red-giant branch or to investigate the onset of the suppression in observed power spectral densities.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"21 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143819500","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":"Electron beam propagation and radio-wave scattering in the inner heliosphere using five spacecraft","authors":"L. A. Cañizares, S. T. Badman, N. Chrysaphi, S. Bhunia, B. Sánchez-Cano, S. A. Maloney, P. T. Gallagher","doi":"10.1051/0004-6361/202452877","DOIUrl":"https://doi.org/10.1051/0004-6361/202452877","url":null,"abstract":"<i>Context.<i/> Solar energetic particles such as electrons can be accelerated to mildly relativistic velocities in the solar corona. These electrons travel through the turbulent corona, generating radio waves, which are then severely affected by scattering.<i>Aims.<i/> The physical interpretation of the discrepancies between the actual and observed radio sources is still subject to debate. We used radio emission observed by an unprecedented total of five spacecraft to track the path of radio sources from the low corona to the inner heliosphere (15–75 R<sub>⊙<sub/> or 0.07–0.35 au generated during a solar event on 4 December 2021.<i>Methods.<i/> We used the Bayesian multilateration technique known as BELLA to track the apparent path of radio sources observed by Parker Solar Probe, STEREO A, Wind, Solar Orbiter, and Mars Express. To validate the accuracy of the tracked path, we used Nançay Radioheliograph interferometric imaging at 150 MHz, which was found to agree with the estimated footpoints predicted by BELLA. We further validated our results using ACE in situ measurements.<i>Results.<i/> We find that the apparent radio sources followed the path of an Archimedean Parker spiral, with an associated solar wind velocity of approximately 493 km s<sup>−1<sup/> (consistent with the corresponding speed observed at 1 au at the relevant longitude), and connected to the solar surface at 75° longitude east. Finally, we made quantitative estimates of the scattering of radio waves, which we found to be in good agreement with contemporary models of scattering in which the radio waves primarily propagate along the local Parker spiral.<i>Conclusions.<i/> This work shows conclusive evidence that the cause of the widely observed ‘higher-than-expected’ electron densities at interplanetary distances is due to radio-wave scattering, and provides a more detailed understanding of the propagation of radio waves emitted near the local plasma frequency in turbulent astrophysical plasmas.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"25 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143819445","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":"On unveiling buried nuclei with JWST: A technique for hunting the most obscured galaxy nuclei from local to high redshift","authors":"I. García-Bernete, F. R. Donnan, D. Rigopoulou, M. Pereira-Santaella, E. González-Alfonso, N. Thatte, S. Aalto, S. König, M. Maksymowicz-Maciata, M. W. R. Smith, J.-S. Huang, G. E. Magdis, P. F. Roche, J. Devriendt, A. Slyz","doi":"10.1051/0004-6361/202452455","DOIUrl":"https://doi.org/10.1051/0004-6361/202452455","url":null,"abstract":"We analyze JWST NIRSpec+MIRI/MRS observations of the infrared (IR) polycyclic aromatic hydrocarbon (PAH) features in the central regions (∼0.26″ at 6 μm; ∼50–440 pc depending on the source) of local luminous IR galaxies. In this work, we examine the effect of nuclear obscuration on the PAH features of deeply obscured nuclei, predominantly found in local luminous IR galaxies, and we compare these nuclei with “normal” star-forming regions. We extend previous work to include shorter wavelength PAH ratios now available with the NIRSpec+MIRI/MRS spectral range. We introduce a new diagnostic diagram for selecting deeply obscured nuclei based on the 3.3 and 6.2 μm PAH features and/or mid-IR continuum ratios at ∼3 and 5 μm. We find that the PAH equivalent width ratio of the brightest PAH features at shorter wavelengths (at 3.3 and 6.2 μm) is impacted by nuclear obscuration. Although the sample of luminous IR galaxies used in this analysis is relatively small, we find that sources exhibiting a high silicate absorption feature cluster tightly in a specific region of the diagram, whereas star-forming regions experiencing lower extinction levels occupy a different area in the diagram. This demonstrates the potential of this technique to identify buried nuclei. To leverage the excellent sensitivity of the MIRI imager on board JWST, we extend our method of identifying deeply obscured nuclei at higher redshifts using a selection of MIRI filters. Specifically, the combination of various MIRI JWST filters enables the identification of buried sources beyond the local Universe and up to <i>z<i/> ∼ 3, where other commonly used obscuration tracers such as the 9.7 μm silicate band, are out of the spectral range of MRS. Our results pave the way for identifying distant deeply obscured nuclei with JWST.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"108 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143819546","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":"Dust and gas modeling in radiative transfer simulations of disc-dominated galaxies with RADMC-3D","authors":"Francesco Sinigaglia, Miroslava Dessauges-Zavadsky, Lucio Mayer, Pedro R. Capelo, Valentina Tamburello","doi":"10.1051/0004-6361/202453404","DOIUrl":"https://doi.org/10.1051/0004-6361/202453404","url":null,"abstract":"<i>Context.<i/> Bridging theory and observations is a key task in modern astrophysics, aimed at improving our understanding of the formation and evolution of galaxies. With the advent of state-of-the-art observational facilities, the accurate modeling of galaxy observables via radiative transfer simulations coupled to hydrodynamic simulations of galaxy formation must be performed.<i>Aims.<i/> We present a novel pipeline, dubbed RTGen, based on the Monte Carlo radiative transfer code RADMC-3D. We explore the impact of the physical assumptions and modeling of dust and gas phases on the resulting galaxy observables. In particular, we thoroughly addressed the impact of the dust abundance, composition, and grain size. We also implemented approximate models for the atomic-to-molecular transition and studied the resulting emission from molecular gas.<i>Methods.<i/> We applied a Monte Carlo radiative transfer a posteriori to determine the dust temperature in six different hydrodynamic simulations of isolated galaxies. Afterwards, we applied ray tracing to compute the spectral energy distribution (SED), as well as to derive the continuum images and spectral line profiles.<i>Results.<i/> We find that our pipeline is able to predict accurate SEDs for the studied galaxies, along with the continuum and CO luminosity images. These results are in good qualitative agreement with literature results from both observations and theoretical studies. In particular, we find the dust modeling to have an important impact on the convergence of the resulting predicted galaxy observables and that an adequate modeling of dust grain composition and size is required.<i>Conclusions.<i/> We conclude that our novel framework is ready to perform high-accuracy studies of the observables of the interstellar medium (ISM), reaching a convergence of a few tens of percent under the studied baseline configuration. This will enable robust studies of galaxy formation and, in particular, the nature of massive clumps in high-redshift galaxies thanks to the generation of reliable and accurate mock images mimicking observations from state-of-the-art facilities, such as JWST and ALMA.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"39 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143814223","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 combined study of thermohaline mixing and envelope overshooting with PARSEC: Calibration to NGC 6397 and M4","authors":"C. T. Nguyen, A. Bressan, A. J. Korn, G. Cescutti, G. Costa, F. Addari, L. Girardi, X. Fu, Y. Chen, P. Marigo","doi":"10.1051/0004-6361/202451847","DOIUrl":"https://doi.org/10.1051/0004-6361/202451847","url":null,"abstract":"Thermohaline mixing is one of the main processes in low-mass red giant stars that affect the transport of chemicals and, thus, the surface abundances along the evolution. The interplay of thermohaline mixing with other processes, such as downward overshooting from the convective envelope, needs to be carefully investigated. This study aims to understand the combined effects of thermohaline mixing and envelope overshooting. After implementing the thermohaline mixing process in the PARSEC stellar evolutionary code, we computed tracks and isochrones (with the TRILEGAL code) and compared them with observational data. To constrain the efficiencies of both processes, we performed detailed modelling that is suitable for globular clusters NGC 6397 and M4. Our results indicate that an envelope overshooting efficiency parameter, Λ<sub>e<sub/> = 0.6, and a thermohaline efficiency parameter, <i>α<i/><sub>th<sub/> = 50, are necessary to reproduce the red-giant-branch bump magnitudes and lithium abundances observed in these clusters. We find that both envelope overshooting and thermohaline mixing have a significant impact on the variation in <sup>7<sup/>Li abundances. Additionally, we also explore the effects of adopting solar-scaled or <i>α<i/>-enhanced mixtures on our models. The <sup>12<sup/>C and the <sup>12<sup/>C/<sup>13<sup/>C ratio are also effective indicators with which to probe extra mixing in red-giant-branch stars. However, their usefulness is currently limited by the lack of precise and accurate C-isotopes abundances.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"99 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143814226","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":"Quantifying the completeness and reliability of visual source extraction: An examination of eight thousand data cubes by eye","authors":"Rhys Taylor","doi":"10.1051/0004-6361/202451606","DOIUrl":"https://doi.org/10.1051/0004-6361/202451606","url":null,"abstract":"<i>Context.<i/> Source extraction in HI radio surveys is still often performed using visual (by-eye) inspection, but the efficacy of the procedure lacks rigorous quantitative assessment due its laborious nature. Thus, algorithmic methods are often preferred due to their repeatable results and speed.<i>Aims.<i/> This work attempts to quantitatively assess the completeness and reliability of visual source extraction by using a suitably large sample of artificial sources and a comparatively rapid source extraction tool and to compare the results with those from automatic techniques.<i>Methods.<i/> A dedicated source extraction tool was modified to significantly reduce the cataloguing speed. I injected 4232 sources into a total of 8500 emission-free data cubes, with at most one source per cube. The sources covered a wide range of signal-to-noise values and velocity widths. I blindly searched all cubes for the sources, measuring the completeness and reliability for pairs of signal-to-noise and line width values. Smaller control tests were performed to account for the possible biases in the search, which gave results in good agreement with the main experiment. I also searched cubes injected with artificial sources using algorithmic extractors and compared these results with a set of catalogues independently reported from real observational data, which were searched with different automatic methods.<i>Results.<i/> I find that the results of visual extraction follow a tight relation between integrated signal-to-noise and completeness. Visual extraction compares favourably in efficacy with the algorithmic methods, tending to recover a higher fraction of fainter sources.<i>Conclusions.<i/> Visual source extraction can be a surprisingly rapid procedure that yields higher completeness levels than automatic techniques, giving predictable and quantifiable results that are not strongly subject to the whims of the observer. Regarding the recovery of the faintest features, algorithmic extractors can be competitive with visual inspection but do not yet outperform it, though their advantage in speed can be a significant compensating factor.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"250 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143813926","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":"Earth-like planet predictor: A machine learning approach","authors":"Jeanne Davoult, Romain Eltschinger, Yann Alibert","doi":"10.1051/0004-6361/202452434","DOIUrl":"https://doi.org/10.1051/0004-6361/202452434","url":null,"abstract":"<i>Context.<i/> Searching for planets analogous to Earth in terms of mass and equilibrium temperature is currently the first step in the quest for habitable conditions outside our Solar System and, ultimately, the search for life in the universe. Future missions such as PLAnetary Transits and Oscillations of stars or Large Interferometer For Exoplanets will begin to detect and characterise these small, cold planets, dedicating significant observation time to them.<i>Aims.<i/> The aim of this work is to predict which stars are most likely to host an Earth-like planet (ELP) to avoid blind searches, minimises detection times, and thus maximises the number of detections.<i>Methods.<i/> Using a previous study on correlations between the presence of an ELP and the properties of its system, we trained a Random Forest to recognise and classify systems as ‘hosting an ELP’ or ‘not hosting an ELP’. The Random Forest was trained and tested on populations of synthetic planetary systems derived from the Bern model, and then applied to real observed systems.<i>Results.<i/> The tests conducted on the machine learning (ML) model yield precision scores of up to 0.99, indicating that 99% of the systems identified by the model as having ELPs possess at least one. Among the few real observed systems that have been tested, eight have been selected as having a high probability of hosting an ELP, and a quick study of the stability of these systems confirms that the presence of an Earth-like planet within them would leave them stable.<i>Conclusions.<i/> The excellent results obtained from the tests conducted on the ML model demonstrate its ability to recognise the typical architectures of systems with or without ELPs within populations derived from the Bern model. If we assume that the Bern model adequately describes the architecture of real systems, then such a tool can prove indispensable in the search for Earth-like planets. A similar approach could be applied to other planetary system formation models to validate those predictions.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"14 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143813998","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 nature of an imaginary quasi-periodic oscillation in the soft-to-hard transition of MAXI J1820+070","authors":"Candela Bellavita, Mariano Méndez, Federico García, Ruican Ma, Ole König","doi":"10.1051/0004-6361/202453092","DOIUrl":"https://doi.org/10.1051/0004-6361/202453092","url":null,"abstract":"A recent study shows that if the power spectra (PS) of accreting compact objects consist of a combination of Lorentzian functions that are coherent in different energy bands but incoherent with each other, the same is true for the real and imaginary parts of the cross spectrum (CS). Using this idea, we discovered imaginary quasi-periodic oscillations (QPOs) in NICER observations of the black hole candidate MAXI J1820+070. The imaginary QPOs appear as narrow features with a small real and large imaginary part in the CS but are not significantly detected in the PS when they overlap in frequency with other variability components. The coherence function drops and the phase lags increase abruptly at the frequency of the imaginary QPO. We show that the multi-Lorentzian model that fits the PS and CS of the source in two energy bands correctly reproduces the lags and the coherence, and that the narrow drop in the coherence is caused by the interaction of the imaginary QPO with other variability components. The imaginary QPO appears only in the decay of the outburst, during the transition from the high-soft to the low-hard state of MAXI J1820+070, and its frequency decreases from ∼5 Hz to ∼1 Hz as the source spectrum hardens. We also analysed the earlier observations of the transition, where no narrow features were seen, and we identified a QPO in the PS that appears to evolve into the imaginary QPO as the source hardens. As for the type-B and C QPOs in this source, the rms spectrum of the imaginary QPO increases with energy. The lags of the imaginary QPO are similar to those of the type-B and C QPOs above 2 keV but differ from the lags of those other QPOs below that energy. While the properties of this imaginary QPO resemble those of type-C QPOs, we cannot rule out that it is a new type of QPO.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"23 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143813995","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":"Standing torsional Alfvén waves as the source of the rotational period variation in magnetic early-type stars","authors":"Koh Takahashi, Norbert Langer","doi":"10.1051/0004-6361/202452850","DOIUrl":"https://doi.org/10.1051/0004-6361/202452850","url":null,"abstract":"<i>Context.<i/> The influence of magnetic fields on stellar evolution remains unresolved. It has been proposed that if there is a large-scale magnetic field in the stellar interior, torsional Alfvén waves could arise, efficiently transporting angular momentum. In fact, the observed variations in the rotation periods of some magnetic stars can be attributed to these torsional Alfvén waves’ standing waves.<i>Aims.<i/> We aim to demonstrate the existence of torsional Alfvén waves through modeling of the rotational period variations.<i>Methods.<i/> We conducted an eigenmode analysis of standing Alfvén waves based on one-dimensional magnetohydrodynamic equations. We parametrically represented internal magnetic field structures to treat poloidal fields with different degrees of central or surface concentration. We compared the obtained frequencies with the observed frequencies of the rotational period variations, thereby constraining the internal magnetic field structures.<i>Results.<i/> The cycle length of CU Vir’s rotational period variation of 67.6 years is reproduced for surface-concentrated magnetic field structures. The rotational period variations of all ten magnetic stars analyzed in this study are inconsistent with a centrally concentrated magnetic field.<i>Conclusions.<i/> Torsional Alfvén waves can reproduce the observations of rotational period variations. The large-scale magnetic fields within magnetic stars are likely concentrated on the surface.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"90 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143814349","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}