Spectroscopy and photometry of the emission-line B-type stars AS 78 and MWC 657

Details Spectroscopy and photometry of the emission-line B-type stars AS 78 and MWC 657 Spectroscopy and photometry of the emission-line B-type stars AS 78 and MWC 657

Nov 2000

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000a%26as..147....5m&link_type=abstract

Astronomy and Astrophysics Supplement, v.147, p.5-24

Astronomy and Astrophysics

Astrophysics

19

Techniques: Photometric, Techniques: Spectroscopic, Stars: Emission-Line, Stars: Circumstellar Matter, Stars: Individual (As 78, Mwc 657)

Scientific paper

We present the results of low- and high-resolution spectroscopic and multicolour photometric observations of two early-type emission-line stars, AS 78 and MWC 657. They were identified by Dong & Hu (\cite{dong}) with the IRAS sources 03549+5602 and 22407+6008, respectively, among many other sources displaying a very strong infrared excess, V-[25] >= 8 mag AS 78 is recognized as a photometric variable for the first time. A large near-IR excess radiation is detected in AS 78 and confirmed by new, higher-quality, data for MWC 657. Significant variations in the Balmer line profiles are detected for both objects. Modelling of the Balmer line profiles of AS 78 obtained in 1994 yields the following parameters of the star and its wind: Teff ~ 17 000 K, log Lbol/Lsun ~ 4.0, dot M ~ 10-6 Msun yr-1. The photometric and new spectroscopic data indicate that the star's Teff increases with time, while the stellar wind changes its structure. Distances towards both objects are estimated on the basis of their radial velocities and the galactic rotation curve. Consideration of different options about the nature and evolutionary state of both objects leads us to suggest that they are binary systems containing a B-type intermediate-luminosity star and a gaseous disk around the less luminous component. Table 9 is only available in electronic form at the CDS via anonymous ftp (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html

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