Optical spectroscopy of RU Cam, a pulsating carbon star

TL;DR

This study presents high-resolution spectral analysis of RU Cam, a pulsating carbon star, revealing its atmospheric parameters, elemental abundances, and peculiar spectral features, contributing to understanding its chemical composition and stellar behavior.

Contribution

First detailed high-resolution spectral analysis of RU Cam confirming its atmospheric parameters and elemental abundances, including carbon excess and peculiar NaI emission features.

Findings

RU Cam has Teff=5250K and log g=1.0.

Carbon and nitrogen are significantly overabundant.

NaI doublet shows emission features at two observation times.

Abstract

We analysed the high resolution spectra of a RU Cam, classified as W Vir type star. The atmospheric parameters of RU Cam were estimated Teff=5250K and log g=1.0. The hydrogen deficiency of RU Cam was not confirmed. The iron abundance, [Fe/H]=-0.37, is close to the solar one. Abundances of most other elements are also close to normal. We found considerable excesses of carbon and nitrogen: [C/Fe]=+0.98, [N/Fe]=+0.60. The carbon to oxygen ratio is C/O$\ge$1. The carbon isotopic abundance ratio is equal to C^12/C^13=4.5. For sodium a moderate overabundance Na/Fe=+0.55 was obtained. For two moments of observations we found close heliocentric velocity values, Vr=-21.7+/-0.8 and -23.1+/-1.0 km/s. Both spectra contain a peculiar feature - an emission component of NaI doublet which location agrees with the radial velocity from the bulk of metallic lines. For our two observing moments we found no dependence of radial velocities on the formation depth or on excitation energy for metallic lines.