Toward Understanding the B[e] Phenomenon. II. New Galactic FS CMa Stars

Abstract

FS CMa stars form a group of objects with the B[e] phenomenon that were previously known as unclassified B[e] stars or B[e] stars with warm dust (B[e]WD) until recently. They exhibit strong emission-line spectra and strong IR excesses, most likely due to recently formed circumstellar dust. These properties have been suggested to be due to ongoing or recent rapid mass exchange in binary systems with hot primaries and various types of secondaries. The first paper of this series reported an analysis of the available information about previously known Galactic objects with the B[e] phenomenon, the initial selection of the FS CMa group objects, and a qualitative explanation of their properties. This paper reports the results of our new search for more FS CMa objects in the IRAS Point Source Catalog. We present new photometric criteria for identifying FS CMa stars as well as the first results of our observations of nine new FS CMa group members. With this addition, the FS CMa group has now 40 members, becoming the largest among the dust-forming hot star groups. We also present nine objects with no evidence for the B[e] phenomenon, but with newly discovered spectral line emission and/or strong IR excesses.

First detections of FS Canis Majoris stars in clusters

“…As shown by Hollenbach & Adams (2004), photoevaporation caused by UV radiation from nearby massive stars has a strong effect on dispersal of disks in young clusters, and this mechanism becomes predominant in the outer regions of the disks. The latter also could explain the aforementioned SED decrease even at shorter wavelengths (6-8 μm) than for other FS CMa stars (10-30 μm;Miroshnichenko 2007;Miroshnichenko et al 2007). …”

A Study of Mass Loss and Dust Formation Near Hot Stars

“…This is due to weakness of the secondary components contribution to the total spectrum of the system. Typically the secondary components are 2-4 magnitudes fainter than the Btype primaries in the optical region of spectrum (e.g., Miroshnichenko, 2007;Miroshnichenko et al, 2015).…”

“…However, the nature of 30 objects out of these 65 was not determined, and they were called unclassified objects with the B[e] phenomenon. Miroshnichenko (2007) analyzed properties of the unclassified objects and summarized them as follows: 2. a large IR excess that peaks at λ ∼ 10-30 µm and sharply decreases toward longer wavelengths;…”

“…Miroshnichenko et al (2007) expanded the group with 10 objects found in the IRAS catalog by cross-identification with catalogs of optical positions. Miroshnichenko et al (2011) found 20 more group objects by cross-correlating the Hamburg catalog of emission-line stars (Kohoutek & Wehmeyer, 1999), IRAS (IPAC, 1986), and2MASS (Cutri et al, 2003) catalogs.…”

AMBER/VLTI observations of the B[e] star MWC 300

“…The binarity of MWC 349A has not been directly confirmed, but was suggested by Hofmann et al (2002). Although the exact role of binarity in the B[e] phenomenon is still an open question, it is possible that the disks are the result of mass exchange episodes between the stellar components of the B[e] stars (Sheikina et al 2000;Miroshnichenko 2007;Miroshnichenko et al 2007Miroshnichenko et al , 2009Kraus et al 2010Kraus et al , 2012b. The slowing down of the radiative wind by the companion gravitational effect or wind shock may also be an explanation (Plets et al 1995).…”