Nature and spectral variations of the B-type emission-line object MWC 645
Creators
- 1. Al-Farabi Kazakh National University, Al-Farabi Ave. 71, 050040, Almaty, Kazakhstan
- 2. Al-Farabi Kazakh National University, Al-Farabi Ave. 71, 050040, Almaty, Kazakhstan, Fesenkov Astrophysical Institute, Observatory 23, 050020 Almaty, Kazakhstan
- 3. Department of Physics and Astronomy, University of North Carolina at Greensboro, Greensboro, NC 27402, USA, Main (Pulkovo) Astronomical Observatory of the Russian Academy of Sciences, Pulkovskoye chaussee 65, 196140, Saint-Petersburg, Russia, Fesenkov Astrophysical Institute, Observatory 23, 050020 Almaty, Kazakhstan
- 4. Canada-France-Hawaii Telescope Corporation, 65-1238 Mamalahoa Hwy, Kamuela, HI 96743, USA
- 5. Instituto de Astronoma, Universidad Nacional Autonoma de Mexico, Apartado Postal 877, MX-22830, Ensenada, Baja California, Mexico
- 6. ) Special Astrophysical Observatory of the Russian Academy of Sciences
- 7. Main (Pulkovo) Astronomical Observatory of the Russian Academy of Sciences, Pulkovskoye chaussee 65, 196140, Saint-Petersburg, Russia
- 8. Saint-Petersburg State University, St. Petersburg, 198504, Russia, Main (Pulkovo) Astronomical Observatory of the Russian Academy of Sciences, Pulkovskoye chaussee 65, 196140, Saint-Petersburg, Russia
Description
We present both optical high-resolution spectroscopic and photometric observations of the FS CMa type object MWC 645 which shows the B[e] phenomenon. This star shows strong Balmer emission lines, narrow permitted and forbidden low-excitation emission lines of FeII, [FeII], and OI. The optical spectrum contains emission and weak absorption lines including diffuse interstellar bands (DIBs). We found a heliocentric radial velocity of -65 km/s from the emission lines and -22 km/s from the absorption lines. Strong emission lines suggest a high temperature of the underlying star, while the absence of helium lines (HeI) may indicate a lack of helium due to an advanced evolutionary stage.
By comparing spectra of MWC 645 and MWC 623 (a binary FS CMa object) we identified lines of neutral metals (LiI 6708, CaI 6717, FeI, TiI, etc.) that characterize the cool component of the binary system. Moreover, the Halpha line has a very intense double-peak profile in the spectrum of MWC 645 and shows strong variations.
The spectral energy distribution (SED) also confirms the B[e] phenomenon. The object has a circumstellar envelope that emits an infrared excess. A combination of our photometric and spectroscopic study of the star makes possible to estimate object's temperature. The hot component has a maximum temperature of 20,000 K (early subtype of spectral type B), and the cold component has a temperature of 4000-5000K (spectral type no earlier than G).
Analysis of the collected data suggests that MWC 645 is a binary system with the B[e] phenomenon which consists of a hot and a cool component
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Nodyarov_Atilkhan_MWC645-OBA_stars.pdf
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