Changes of the Optical Spectrum of the Hypergiant ρ Cas due to a Shell Ejection in 2013

Аннотация

Spectral monitoring of the yellow hypergiant ρ Cas with the by 6-m telescope of the Special Astrophysical Observatory with a spectral resolution of R ≥ 60 000 has led to the detection of new features in the kinematic state of its extended atmosphere following the ejection of matter in 2013. Significant changes in the profile of the Hα line were detected: the line had a doubled core for the first time in a 2014 spectrum, an inverse P Cygni profile on February 13, 2017, and the profile was again doubled on August 6, 2017 and September 5, 2017, but was strongly shifted toward longer wavelengths, indicating a rapid infall of matter. Splitting of the profiles of strong, low-excitation absorption lines into three components was first detected in 2017. There is no correlation between the evolution of the profiles of Hα and the splitted absorption lines. Pulsation-like variability with an amplitude of about 10 km/s is characteristic only of symmetric weak and moderate-intensity absorption lines. Shell emission lines of iron-group elements can be identified in the long-wavelength part of a spectrum obtained in 2013, whose intensity decreased until they completely disappeared in 2017. In the absence of emission in the cores of the H and K lines of Ca II, emission lines of shell metals are visible in the wings of these lines.