The Inhomogeneous Wind of the LBV Candidate CygOB2-No.12

TL;DR

This study provides detailed high-resolution spectral analysis of the luminous star CygOB2-No.12, revealing complex wind behavior, atmospheric dynamics, and spectral features indicative of variability and inhomogeneity.

Contribution

It offers the first detailed spectral characterization of CygOB2-No.12, including identification of spectral features and evidence of a variable, inhomogeneous stellar wind.

Findings

Spectral features identified include NaI, KI, DIBs, HeI, CII, SiII.

Radial velocity data shows atmospheric expansion and matter infall.

The stellar wind is variable over time.

Abstract

We present the results of high-resolution spectroscopy of the extremely luminous star CygOB2-No.12. We identified about 200 spectral features in the range 4552-7939 AA, including the interstellar NaI, KI lines and numerous very strong DIBs, along with the HeI, CII, and SiII lines. An MK spectral type we derived for the object is B4.5Ia+. Our analysis of the radial velocity data shows the presence of a gradient in the stellar atmosphere, caused by both atmospheric expansion and matter infall onto the star. The Halpha emission displays broad Thompson wings, a slightly blue-shifted PCyg type absorption component and a time-variable core absorption. We conclude that the wind is variable in time.