engleski

Properties and nature of Be stars. XXII. Long-term light and spectral variations of the new bright Be star HD 6226

Photometric and spectroscopic monitoring of the B star HD 6226 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 He I 6678 line, seen both outside and during emission-line episodes, are all attributes which make HD 6226 phenomenologically very similar to the well-known Be star &omega ; CMa. Radial velocities of the deepest parts of the metallic and He I 6678 absorption lines vary with a strict period of 2.61507 d 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 BV magnitudes and Hipparcos parallax all agree with the conclusion that HD 6226 is a star with the following basic properties: Teff , = 17 000 K, log g = 3.0 [cgs], mass of 5m.s and radius of 11 Ro. The strong emission-line episodes may appear regularly, in a cycle of 630 days but with different durations of individual cycles. HD 6226 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.

stars: binaries: spectroscopic; stars: emission-line; Be; stars: individual: HD 6226

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