Crimean Astrophysical Observatory of the Russian Academy of Sciences
УДК 524.33 Переменные звезды. Физические переменные
УДК 53 Физика
УДК 520 Инструменты, приборы и методы астрономических наблюдений, измерений и анализа
УДК 521 Теоретическая астрономия. Небесная механика. Фундаментальная астрономия. Теория динамической и позиционной астрономии
УДК 523 Солнечная система
УДК 524 Звезды и звездные системы. Вселенная Солнце и Солнечная система
УДК 52-1 Метод изучения
УДК 52-6 Излучение и связанные с ним процессы
ГРНТИ 41.00 АСТРОНОМИЯ
ГРНТИ 29.35 Радиофизика. Физические основы электроники
ГРНТИ 29.31 Оптика
ГРНТИ 29.33 Лазерная физика
ГРНТИ 29.27 Физика плазмы
ГРНТИ 29.05 Физика элементарных частиц. Теория полей. Физика высоких энергий
ОКСО 03.06.01 Физика и астрономия
ОКСО 03.05.01 Астрономия
ОКСО 03.04.03 Радиофизика
ББК 2 ЕСТЕСТВЕННЫЕ НАУКИ
ББК 223 Физика
ТБК 614 Астрономия
ТБК 6135 Оптика
BISAC SCI004000 Astronomy
BISAC SCI005000 Physics / Astrophysics
To test the origin of the X-ray and optical emission from the $\gamma$ Cas-type stars, we analyzed their optical spectra obtained on the 6-m telescope BTA, the 1.25-m telescope of the Crimean station of the State Astronomical Institute (SAI, Moscow), the 2.5-m telescope SAI25 of SAI, and the photometric TESS light curves. We compare the optical variability of the $\gamma$ Cas-type stars with variations of their X-ray luminosity. An overlap between the periods of line profile variations in the spectra of $\gamma$ Cas stars and the variations in their X-ray brightness allows us to assume that a significant fraction of X-rays emits from the same place where the optical radiation comes from. The $\gamma$ Cas-type stars HD 45314, HD 45995 and NGC 6649 9 demonstrate the ultrafast X-ray brightness variations with the periods of about 50–90 seconds, which may be the rotation periods of white dwarfs components of binary systems. Thus, we can assume that at least for these stars the X-ray emission goes partly due to accretion onto rapidly rotating white dwarfs. The anomalously hard X-ray emission from the $\gamma$ Cas stars can be interpreted by assuming that the contribution of non-thermal X-ray emission is generated as a result of a reconnection of the local magnetic field lines of the Be star and its decretion disk.
stars: general, emission-line, Be; X-rays: stars
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