FS CMa type binaries

TL;DR

FS CMa type stars are a group of about 70 objects exhibiting strong emission lines, IR excesses, and signs of binarity, with new spectroscopic evidence suggesting the presence of cool companions, impacting their understanding and evolution.

Contribution

This paper provides the first overview of FS CMa type binaries, highlighting spectroscopic evidence of cool companions and discussing their nature and evolutionary implications.

Findings

Detection of neutral metal lines indicating cool stars

Presence of Li I 6708 Å line in some spectra

Implications for the binary nature and evolution of FS CMa stars

Abstract

FS CMa type stars is a group of ~70 objects formerly known as unclassified stars with the B[e] phenomenon. Their very strong emission-line spectra in combination with a nearly main-sequence luminosity suggest the binary nature for them. They possess strong IR excesses due to radiation of circumstellar dust that implies a compact distribution probably in a circumbinary disk. Our long-term spectroscopic monitoring revealed neutral metal lines, which always include that of Li I 6708 \AA, in the spectra of some FS CMa objects indicating the presence of a cool star. We present a summary of our results with a first overview of FS CMa type binaries and review possible implications for the nature and evolutionary status of the entire group.