{"title":"γ Cas Stars: The Origin of the X-ray Emission","authors":"A. F. Kholtygin, E. B. Ryspaeva","doi":"10.1134/S0016793224700361","DOIUrl":null,"url":null,"abstract":"<p>The γ Cas type stars are a group of Be stars with unusually hard X-ray emission and an X-ray luminosity of <i>L</i><sub><i>X</i></sub> ~ 10<sup>31</sup>–10<sup>33</sup> erg/s, which is higher than for typical Be stars but less than for massive X-ray binaries with Be components. The temperature of the X-ray emitting plasma reaches values of 10–20 keV or even more, assuming that they emit thermal X-rays. To test the hypotheses on the X-rays formation from this group of stars, the variability of the X-ray and optical emission of γ Cas type stars is analyzed. Regular components of X-ray brightness variations and H, He and FeII line profile variations in spectra of such stars are revealed. The periods of optical and X-ray variability are close and correspond to typical periods of non-radial pulsations (NRPs) of Be stars. That suggests modulation of the wind structure of a Be star as a result of NRPs.</p>","PeriodicalId":55597,"journal":{"name":"Geomagnetism and Aeronomy","volume":"64 8","pages":"1267 - 1272"},"PeriodicalIF":0.7000,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Geomagnetism and Aeronomy","FirstCategoryId":"89","ListUrlMain":"https://link.springer.com/article/10.1134/S0016793224700361","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}
引用次数: 0
Abstract
The γ Cas type stars are a group of Be stars with unusually hard X-ray emission and an X-ray luminosity of LX ~ 1031–1033 erg/s, which is higher than for typical Be stars but less than for massive X-ray binaries with Be components. The temperature of the X-ray emitting plasma reaches values of 10–20 keV or even more, assuming that they emit thermal X-rays. To test the hypotheses on the X-rays formation from this group of stars, the variability of the X-ray and optical emission of γ Cas type stars is analyzed. Regular components of X-ray brightness variations and H, He and FeII line profile variations in spectra of such stars are revealed. The periods of optical and X-ray variability are close and correspond to typical periods of non-radial pulsations (NRPs) of Be stars. That suggests modulation of the wind structure of a Be star as a result of NRPs.
期刊介绍：
Geomagnetism and Aeronomy is a bimonthly periodical that covers the fields of interplanetary space; geoeffective solar events; the magnetosphere; the ionosphere; the upper and middle atmosphere; the action of solar variability and activity on atmospheric parameters and climate; the main magnetic field and its secular variations, excursion, and inversion; and other related topics.
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