High-frequency variations of spectral lines in cromospherically active stars 61 cyg AB

• Published in: Kinematics and physics of celestial bodies Vol. 31; no. 6; pp. 267 - 275
• Main Authors: Zhilyaev, B. E., Bondar, A. V., Andreev, M. V., Pokhvala, S. M., Ivashchenko, Yu. M., Reshetnyk, V. M., Petukhov, V. N., Svyatogorov, O. A., Verlyuk, I. A.
• Format: Journal Article
• Language: English
• Published: New York Allerton Press 01.11.2015; Springer Nature B.V
• Subjects: Astronomy; Hydrogen; Intervals; Mathematical models; Observations and Techniques; Physics; Physics and Astronomy; Physics of Stars and Interstellar Medium; Radio telescopes; Spectra; Spectral lines; Spectrographs; Stars; Stars & galaxies; Telescopes; Comparison Star; Balmer Line; Flare Star; Celestial Body; Active Star
• ISSN: 0884-5913; 1934-8401
• DOI: 10.3103/S0884591315060082

We report on the detection of rapid variability in subsecond mode in the Balmer lines of hydrogen, lines Ca II H,K, and b Mg I triplet in chromospherically active stars 61 Cyg A, B. The spectral observations of 61 Cyg A, B were performed with MMCS spectrograph in Cassegrain’s focus of the 2-m telescope at peak Terskol ( R = 13000), with a grating spectrograph mounted on a 60-cm telescope at peak Terskol ( R ≈ 100), and a 60-cm telescope of the Andrushivka Observatory ( R ≈ 200). The observations were carried out in the framework of international campaign of observations of variable stars using the Synchronous Network of Telescopes. The high-resolution spectra were obtained with intervals of approximately 2 minutes. The low-resolution spectra were obtained with intervals from 2 to 3 seconds. Spectral monitoring lasted from 30 minutes to 2 hours. We found that chromospherically active dwarf stars 61 Cyg A, B, having extensional spots on their surfaces exhibit rapid variations in the hydrogen lines, lines CaII H, K of ionized calcium and chromospheric triplet b Mg I on a time scale from approximately 2 seconds to approximately 2 minutes. Variations in the intensity of lines range from 1.5% in the Balmer series of hydrogen to approximately 0.5% in the lines of b Mg I triplet. These variations are well described by the shot noise model in the form of random elementary pulses with the frequency of occurrence of a few fractions of events per second to a few events per second. Comparison of rapid variations in chromospheric lines with different time intervals demonstrates the transient nature of this activity both on short (subsecond) and long-time scales.