EDP Sciences
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Volume 416, Number 2, March III 2004
Page(s) 669 - 676
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361:20031732

A&A 416, 669-676 (2004)
DOI: 10.1051/0004-6361:20031732

Properties and nature of Be stars

XXII. Long-term light and spectral variations of the new bright Be star
H. Bozic1, P. Harmanec2, 3, S. Yang4, J. Ziznovský5, J. R. Percy6, D. Ruzdjak1, D. Sudar1, M. Slechta3, P. Skoda3, J. Krpata2 and C. Buil7

1  Hvar Observatory, Faculty of Geodesy, Zagreb University, 10000 Zagreb, Croatia
2  Astronomical Institute of the Charles University, V Holesovickách 2, 180 00 Praha 8, Czech Republic
3  Astronomical Institute, Academy of Sciences, 251 65 Ondrejov, Czech Republic
4  Department of Physics and Astronomy, University of Victoria, PO Box 3055 STN CSC, Victoria, BC, V8W 3P6, Canada
5  Astronomical Institute of the Slovak Academy of Sciences, 059 60 Tatranská Lomnica, Slovak Republic
6  Erindale Campus and Department of Astronomy and Astrophysics, University of Toronto, Mississauga, ON L5L IC6, Canada
7  Association des Utilisateurs de Détecteurs Électroniques (AUDE), 28 rue du Pic du Midi, 31130 Quint-Fonsegrives, France

(Received 14 May 2003 / Accepted 6 November 2003)

Photometric and spectroscopic monitoring of the B star resulted in the finding that this object is a new bright Be star with a clear positive correlation between the brightness and emission-line strength. The emission-line episodes are relatively short and seem to repeat frequently which makes this star an ideal target for studying the causes of the Be phenomenon. The general character of the light variations, the low v sin  i = 70 km s -1 and the very pronounced line asymmetries of the $\ion{He}{i}$ 6678 line, seen both outside and during emission-line episodes, are all attributes which make phenomenologically very similar to the well-known Be star $\omega$ CMa. Radial velocities of the deepest parts of the metallic and $\ion{He}{i}$ 6678 absorption lines vary with a strict period of 2 $^{\rm d}\!\!.$61507 over the whole time interval covered by the observations, the velocities of the broad outer wings of the same lines varying in anti-phase and with a lower amplitude. This periodicity could not be found in the radial-velocity variations of the sharp core of H $\alpha$. There is some indication of variability on a time scale of 24-29 days but our data are insufficient to prove that conclusively. A comparison of the line spectrum obtained outside emission episodes with synthetic spectra, standard dereddening of $U\!B{}V$ magnitudes and Hipparcos parallax all agree with the conclusion that is a star with the following basic properties: $T_{\rm eff}$ = 17 000 K, log  g = 3.0 [cgs], mass of 5  $M_{\odot}$ and radius of 11  $R_{\odot}$. The strong emission-line episodes may appear regularly, in a cycle of 630 days but with different durations of individual cycles. is probably one of the first B stars for which the Be nature was predicted on the basis of the character of its light and colour changes.

Key words: stars: binaries: spectroscopic -- stars: emission-line, Be -- stars: individual:

Offprint request: H. Bozic, hbozic@geodet.geof.hr

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