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Study of an unbiased sample of B stars observed with Hipparcos: the discovery of a large amount of new slowly pulsating B stars
We present a classification of 267 new variable B-type stars discoveredby Hipparcos. We have used two different classification schemes and theyboth result in only a few new beta Cephei stars, a huge number of newslowly pulsating B stars, quite some supergiants with alpha Cyg-typevariations and variable CP stars, and further some new periodic Be starsand eclipsing binaries. Our results clearly point out the biased naturetowards short-period variables of earlier, ground-based surveys ofvariable stars. The position of the new beta Cephei stars and slowlypulsating B stars in the HR diagram is determined by means of Genevaphotometry and is confronted with the most recent calculations of theinstability strips for both groups of variables. We find that the newbeta Cephei stars are situated in the blue part of the instability stripand that the new slowly pulsating B stars almost fully cover thetheoretical instability domain determined for such stars. Thesupergiants with alpha Cyg-type variations are situated between theinstability strips of the beta Cephei and the slowly pulsating B starson the one hand and previously known supergiants that exhibitmicrovariations on the other hand. This suggests some connection betweenthe variability caused by the kappa mechanism acting in a zone ofpartially ionised metals and the unknown cause of the variations insupergiants.
| The 72nd Name-List of Variable Stars
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| Light variations of massive stars (Alpha Cygni variables). XIII - The B-type hypergiants R81 (LBV), HD 80077 (LBV?), HD 168607 = V 4029 Sagittarii (LBV) and HD 168625 = V 4030 Sagittarii
We present and discuss VBLUW and uvby photometry of four Alpha Cygvariables: the B-type hypergiants R81, HD 80077, HD 168607 = V 4029 Sgr,and HD 168625 = V 4030 Sgr. Quasi-periods of the light variations amountto 24,41 or 55,58 and 35 days, respectively. The maximum light amplitude(MLA) of R 81 and HD 168607 clearly reflects their LBV character. Thatfor HD 80077 suggests that it could be an LBV also. Normal Alpha Cygvariables and those which suffer from episodic mass loss eruptions, theLBVs appear to listen to the same P = constant lines in the HR diagram,but the light curves of both types show morphological differences.
| HD 80859 (B5 V) - A possible new slowly pulsating B-type star
The VBLUW photometry of a possible new member of the slowly pulsatingB-type stars is presented and discussed. This is HD 80859 (B5 V) with alight amplitude in the visual of 0.02m and a period P = 2.862d. Data onthe period of light variations and interstellar reddening are examined.
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