Changes of the optical spectrum of the hypergiant $\rho$ Cas due to a shell ejection in 2013

TL;DR

This study used high-resolution spectral monitoring to observe significant changes in the optical spectrum of the hypergiant $ ho$ Cas following a shell ejection in 2013, revealing complex atmospheric dynamics and matter infall.

Contribution

It provides detailed spectral analysis of $ ho$ Cas's atmospheric changes post-shell ejection, highlighting new features and variability patterns not previously documented.

Findings

Detection of doubled Hα line core in 2014

Inverse P Cygni profile observed in 2017

Splitting of absorption profiles into three components in 2017

Abstract

Spectral monitoring of the yellow hypergiant $\rho$ Cas with the by 6-m telescope of the Special Astrophysical Observatory with a spectral resolution of R$\ge$60000 has led to the detection of new features in the kinematic state of its extended atmosphere following the ejection of matter in 2013. Significant changes in the profile of the H$\alpha$ line were detected: the line had a doubled core for the first time in a 2014 spectrum, an inverse P Cygni profile on December 13, 2017, and the profile was again doubled on August 6, 2017 and September 5, 2017, but its core was strongly shifted toward longer wavelengths, indicating a rapid infall of matter. Splitting of the profiles of strong, low-excitation absorptions into three components was first detected in 2017. There is no correlation between the evolution of the profiles of H$\alpha$ and the splitted absorptions. Pulsation-like variability with an amplitude of about 10 km/s is characteristic only of symmetric weak and moderate-intensity absorption lines. Shell emissions 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 CaII, emissions of shell metals are visible in the wings of these lines.