New in the optical spectrum and kinematic state of the atmosphere of the variable V1027\,Cyg (= IRAS 20004+2955)

TL;DR

This study uses high-resolution spectroscopy to analyze the atmosphere and envelope of the variable supergiant V1027 Cyg, revealing spectral line splitting, pulsations, and interstellar features for the first time.

Contribution

First detection of spectral line splitting and detailed velocity field analysis in V1027 Cyg's atmosphere using high-resolution spectroscopy.

Findings

Detected splitting of metal absorption cores.

Identified stable systemic velocity of 5.5 km/s.

Observed pulsation-induced radial velocity variations.

Abstract

Based on high-resolution spectroscopy performed with the NES echelle spectrograph of the 6-m telescope, we have studied the peculiarities of the spectrum and the velocity field in the atmosphere and envelope of the cool supergiant V1027 Cyg, the optical counterpart of the infrared source IRAS 20004+2955. For the first time, a splitting of the cores of strong absorptions of metals and their ions (SiII, NiI, TiI, TiII, ScII, CrI, FeI, FeII, BaII) has been detected in the stellar spectrum. The broad profile of these lines contains a stable weak emission in the core whose position may be considered as the systematic velocity Vsys=5.5 km/s. Small radial velocity variations with an amplitude of 5-6 km/s due to pulsations have been revealed by symmetric low- and moderate-intensity absorptions. A long-wavelength shift of the H$\alpha$ profile due to line core distortion is observed in the stellar spectrum. Numerous weak CN molecular lines and the KI 7696 \AA\ line with a P Cyg profile have been identified in the red spectral region. The coincidence of the radial velocities measured from symmetric metal absorptions and CN lines suggests that the CN spectrum is formed in the stellar atmosphere. We have also identified numerous diffuse interstellar bands (DIBs) whose positions in the spectrum, Vr(DIBs)=$-12.0$ km/s, correspond to the velocity of the interstellar medium in the Local arm of the Galaxy.