Results of a search for bright β Cephei variables in the southern sky
Abstract
The radial velocities of seven bright southern early B-type stars, known to have variable velocity, have been systematically examined at the Radcliffe Observatory in an effort to detect the presence of short periods (3 to 7 hours) characteristic of fi Cephei variables. Positive results were obtained for three stars: fl Cm ( 14 km/sec), 71 Lup (2K=II km/sec), and a Lup (zK= 15 km/sec). Definitive periods have been derived for ` Lup and a Lup, while a provisional period is suggested for fl Cru. Cm and 71 Lup have been observed photoelectrically by the staff of the Cape Observatory and found to have short-period variations in light with a range of about o' . In the case of 71 Lup, the light variation shows the same period as the velocity variation, with the phase relationship typical of P Cephei variables. In the case of P Cm, all that can be said is that the light variation has approximately the period of the velocity variation. a Lup was observed photoelectrically by A. B. Muller at the Leiden Observatory Southern Station; no variation in excess of om.oi has so far been detected. 71 Lup fits closely the period-luminosity relations derived for P Cephei variables by Blaauw and Savedoff and by Petrie. It is clearly a typical member of the group with constant velocity amplitude. a Lup comes tolerably near to the period-luminosity relation, but, until some variation in light can be established, one cannot quite exclude the possibility that it is a single-lined spectroscopic binary. P Cm, in spite of its early spectral type (Bo), would seem to be related to the P Cephei group, though it is anomalous in a number of ways.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- 1956
- DOI:
- 10.1093/mnras/116.1.10
- Bibcode:
- 1956MNRAS.116...10P