TY - JOUR

T1 - Variability of optical and X-ray spectra of Gamma Cassiopeia stars

AU - Холтыгин, Александр Федорович

AU - Рыспаева, Елизавета Борисовна

AU - Якунин, Илья Андреевич

AU - Циопа, О.А.

PY - 2023/10/31

Y1 - 2023/10/31

N2 - Stars of the γ Cas type (γ Cas analogs) belong to a small group of Be stars with a high X-ray luminosity of 10 31 ‑ 10 33 erg/s and an anomalously high temperature of the plasma emitting in the X-ray range of 10–20 keV or more, assuming a completely thermal X-ray emission. The results of the analysis of the optical spectra of γ Cas under the program of observations on the BTA "Line profile variability in the spectra of OBA stars and the nature of their X-ray emission" and the results of a study of the archival X-ray spectra of this star in 2010–2014 based on observations on the XMM-Newton satellite are presented. The variability of the line profiles in the optical spectra and the variability of the X-ray brightness of the γ Cas star on scales from minutes to hours are found. It is assumed that the minute scale variability is associated with high modes of non-radial pulsations of stars of this type. The periods of optical and X-ray variability turned out to be close, which allows us to hypothesize that the wind structure is modulated as a result of non-radial photospheric pulsations. The anomalously hard X-ray emission from such stars can be explained in terms of the contribution of possible non-thermal X-ray emission resulting from Compton backscattering of UV photons by relativistic electrons.

AB - Stars of the γ Cas type (γ Cas analogs) belong to a small group of Be stars with a high X-ray luminosity of 10 31 ‑ 10 33 erg/s and an anomalously high temperature of the plasma emitting in the X-ray range of 10–20 keV or more, assuming a completely thermal X-ray emission. The results of the analysis of the optical spectra of γ Cas under the program of observations on the BTA "Line profile variability in the spectra of OBA stars and the nature of their X-ray emission" and the results of a study of the archival X-ray spectra of this star in 2010–2014 based on observations on the XMM-Newton satellite are presented. The variability of the line profiles in the optical spectra and the variability of the X-ray brightness of the γ Cas star on scales from minutes to hours are found. It is assumed that the minute scale variability is associated with high modes of non-radial pulsations of stars of this type. The periods of optical and X-ray variability turned out to be close, which allows us to hypothesize that the wind structure is modulated as a result of non-radial photospheric pulsations. The anomalously hard X-ray emission from such stars can be explained in terms of the contribution of possible non-thermal X-ray emission resulting from Compton backscattering of UV photons by relativistic electrons.

KW - Be stars

KW - gamma Cas

KW - optical spectra

KW - X-ray spectra

KW - variability

U2 - 10.51194/inasan.2023.8.2.008

DO - 10.51194/inasan.2023.8.2.008

M3 - статья

VL - 8

SP - 86

EP - 92

JO - Научные труды Института Астрономии РАН

JF - Научные труды Института Астрономии РАН

SN - 2658-5669

IS - 2

ER -