Carbon stars from LAMOST DR2 data

TL;DR

This paper presents a new catalog of 894 carbon stars identified from LAMOST DR2 spectra, classifies them into sub-types, and discusses their spectral features and potential origins.

Contribution

The study introduces a comprehensive catalog of carbon stars from LAMOST DR2, classifies them into sub-types, and analyzes their spectral features for future identification.

Findings

894 carbon stars identified from LAMOST DR2

Distinct spectral features for extch{CN}, extc{C2}, and other lines

No clear spectral separation between extCR ext and extch ext sub-types

Abstract

In this work, we present the new catalog of carbon stars from the LAMOST DR2 catalog. In total, 894 carbon stars are identified from multiple line indices measured from the stellar spectra. Combining the CN bands in the red end with \ctwo\ and other lines, we are able to identify the carbon stars. Moreover, we also classify the carbon stars into spectral sub-types of \ch, \CR, and \cn. These sub-types approximately show distinct features in the multi-dimensional line indices, implying that in the future we can use them to identify carbon stars from larger spectroscopic datasets. Meanwhile, from the line indices space, while the \cn\ stars are clearly separated from the others, we find no clear separation between \CR\ and \ch\ sub-types. The \CR\ and \ch\ stars seem to smoothly transition from one to another. This may hint that the \CR\ and \ch\ stars may not be different in their origins but look different in their spectra because of different metallicity. Due to the relatively low spectral resolution and lower signal-to-noise ratio, the ratio of $^{12}$C/$^{13}$C is not measured and thus the \cj\ stars are not identified.