FS CMa Type Binaries

¹ Department of Physics and Astronomy, University of North Carolina at Greensboro, PO 26170, Greensboro, NC 27402–6170, USA
² Instituto de Astronomía, Universidad Nacional Autónoma de Mexico, Ensenada, Baja California, 22800, Mexico

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 Å, 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.