Spectra of Be Star 28 Cyg ; 2024 July 04th
Cygni 28 is a classical Be star showing a strong emission in H-Alpha originating from a disc around the star. He is also a binary system together with a subdwarf O star detected by interferometry(1) in 2018.
The apparent visual magnitude is about 5 and there at the limit to seen with naked eye. His distance is about 257 +/- 7 parsec. According Slettebak (1982) 28 Cyg is found to be an evolved subgiant star of B2 IV(e),
The emisison lines is originated by gas orbiting on a Keplerian orbit. 28 Cyg also shows a short term varibility with a time scale less than one day and an amplitude about 4 to 5 percent. As alos other Be-Star 28 Cyg is spinning with a relativ high velocity of about 320km/s as projected radial velocity which a at 80% of this critical rotational rate forming the star into an oblate shape with a ration 6.5 / 5.7 equatorial solar radius to polar radius.
| Object | 28 Cyg, July 04th, 2024, 23:40:00 UT |
| Instrument | Friesenheimer Lichteimer |
| Setup | Shelyak, LHiRes III, 2400l/mm, 50µ slit |
| Exposure | 1 x 1200s @ TP 2600 (IMX 571); Gain=25% |
| Software | Maxim DL, ESO MIDAS |
| Comments | calibration performed using telluric lines arround H-Alpha |
(1) Klement, Robert; Schaefer, Gail H.; Gies, Douglas R.; Wang, Luqian; Baade, Dietrich; Rivinius, Thomas; Gallenne, Alexandre; Carciofi, Alex C.; Monnier, John D.; Mérand, Antoine; Anugu, Narsireddy; Kraus, Stefan; Davies, Claire L.; Lanthermann, Cyprien; Gardner, Tyler; Wysocki, Peter; Ennis, Jacob; Labdon, Aaron; Setterholm, Benjamin R.; Le Bouquin, Jean-Baptiste (2022). "Interferometric Detections of sdO Companions Orbiting Three Classical Be Stars". The Astrophysical Journal. 926 (2): 213
(2) Baade, D.; et al. (March 2018), "Short-term variability and mass loss in Be stars. III. BRITE and SMEI satellite photometry of 28 Cygni", Astronomy & Astrophysics, 610: 17