Spectroscopic characterization of FHLC stars from the Hamburg/ESO survey and a newly found HdC star

TL;DR

This study spectroscopically analyzes faint high latitude carbon stars from the Hamburg/ESO survey, identifying a rare hydrogen-deficient carbon star with unique spectral features, and discusses its possible formation mechanisms.

Contribution

It reports the discovery and spectral analysis of a rare Galactic HdC star with unusual s-process element features, expanding understanding of HdC star diversity.

Findings

Identification of a rare HdC star with strong Sr features

Detection of weak Ba spectral features in the star

Discussion of possible formation scenarios for the star

Abstract

The sample of candidate faint high latitude carbon (FHLC) stars chosen from the Hamburg/ESO survey is a potential source to search for objects of rare types. From medium resolution spectral analyses of about 250 objects from this sample, the object HE 1015-2050, was found to be a hydrogen-deficient carbon (HdC) star. Apart from U Aquarii, HE 1015-2050 is the only example, till now, of a Galactic cool HdC star that is characterized by strong spectral features of light s-process element Sr, and weak features of heavy s-process elements such as Ba. This object, with its enhanced carbon and hydrogen-deficiency, together with anomalous s- process spectral features, poses a challenge as far as the understanding of its formation mechanism is concerned. We discuss possible mechanisms for its formation in the framework of existing scenarios of HdC star formation.