AS314: A dusty A-type hypergiant

Send offprint request: A.S.Miroshnichenko,
e-mail: anatoly@physics.utoledo.edu

1 - Central Astronomical Observatory of the Russian Academy of Sciences, Saint-Petersburg, 196140, Russia
2 - Ritter Observatory, Dept. of Physics & Astronomy, University of Toledo, Toledo, OH 43606, U.S.A.
3 - Special Astrophysical Observatory of the Russian Academy of Sciences, Karachai-Cirkassian Republic,
Nizhnij Arkhyz, 357147, Russia
4 - Isaak Newton Institute of Chile, SAO Branch

Abstract:

We present the results of our observations of the poorly-studied emission-line star AS314 which include high-resolution spectroscopy, obtained at the 6-meter telescope of the Russian Academy of Sciences, multicolor optical and near-infrared photometry. The strong H $\alpha$ line, H $\beta$ and H $\gamma$ of moderate strength and a number of weak Fe II lines were detected in emission. The Balmer lines and most of the Fe II lines show narrow PCyg-type profiles which implies a very low terminal velocity of the stellar wind. Very weak signs of emission are found in H $\delta$ . Photospheric lines detected for the first time allowed us to determine the object's spectral type, A0. The luminosity, $M_{\rm bol} \sim -8.0$ mag was estimated using several methods and implies that AS314 is a hypergiant, which is located at about 10 kpc from the Sun and has an initial mass of $\sim 20\; M_{\hbox{$\odot$ }}$ . Modeling of the Balmer line profiles resulted in the following parameters of the stellar wind: $\dot{M} = 2\ 10^{-5}\;M_{\hbox{$\odot$ }}$ yr^-1, $v_\infty = 75\;{\rm km\,s}^{-1}$ . The star is located within the LBV strip in the HRD. Its noticeable far-IR excess is due to the circumstellar dust emission and is likely evidence of an LBV-type outburst in the past.

Key words: stars: emission-line -- stars: supergiants -- circumstellar matter -- stars: mass-loss -- stars:individual - AS314