COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS NUMBER 807 Konkoly Observatory Budapest 1973 June 30 SIX NEW VARIABLE B-STARS Definite changes in brightness were observed by the author in six B-stars of the southern hemisphere during observing campaigns at the ESO Observatory on La Silla mountain (Chile) in 1970 and at the Boyden Observatory (Bloemfontein-South Africa) in 1973. They are listed in the table by their HD number; their m_v, spectral class and RV have been copied from the Catalogue of Bright Stars, 3d edition, while the elements of the light variation are added in so far as they could be determined. Table I * m_v S RV Type Period Amplitude HD 55857 6,11 B3-IV -- beta CMa 2h41m 0.02m HD 55958 6,53 B3 +28V? ? ? >=.06 HD 57219 5,10 B3-V +23V Ell.SB ~24h .045 +beta CMa ~ 3h .02v HD 74146 5,20 B5-V +36V Ell.SB? ? >=.01 HD 74195 3,61 B3-III +17V beta CMa 3h10m +/-.02 HD 74375 4,32 B1-III +13V beta CMa ? >=.02 + SB 133^d92 Remarks to the individual objects. 1. HD 55857 - Was discovered with the photometric equipment attached to the 6" Zeiss telescope of La Silla Observatory in 1970. Its period is the shortest known among beta CMa stars. The lightcurve is a sinusoid, so is the RV-curve with Vgamma = +30 Km/sec and 2K >= 40 Km/sec. 2. HD 55958 - was discovered with the 50" Rockefeller telescope of Boyden Observatory in March 1973 when being used as a comparison star for HD 55857. Figure 1 shows the portions of the light curve which were obtained. The star might well be of the same nature as the next one. 3. HD 57219 (upsilon^2 Pup) - discovered with the 6" Zeiss telescope at La Silla in 1970. The star was under photometric observation during seven hours in each of nine nights in January of that year; moreover spectrograms were taken with the 152 cm telescope on two successive nights. All the tracings showed grosso modo the same image for every night (see Figure 2) namely 3h-waves superposed on the rising branch of a much longer wave. This longer wave had a smaller amplitude in U than in V, a circumstance which ruled out the possibility that it be due to a pulsation. The phase relation between the lightcurves and the RV-curves strengthened this conclusion. The only way to combine all the observed facts into a coherent scheme is to admit that upsilon^2 Pup is the brighter component of a single lined spectroscopic binary with an orbital period close to 24h. This component is ellipsoidal in shape whereby its revolution produces two maxima and two minima and thus a photometric period of 12h. It is at the same time a beta CMa star of short period (3h). The star thus provides an opportunity to look into the details of the pulsations of an elongated star. Confirmation of this interpretation must come from observations made at three southern observatories widely separated in longitude: Australia, South Africa and South America. 4. HD 74146 - was discovered in 1973 at Boyden when being used as a comparison star to ommicron Vel. The mean difference m(4)-m(5) over a cycle of the latter changed from 1.55m to 1.64m. The star is probably an ellipsoidal binary. 5. HD 74195 (omicron Vel) - was already proclaimed a beta CMa star from its radial velocity changes. (Van Hoof, Astr.Astrophys. 18, 51-54, 1972) Photometric observations made at Boyden in 1973 have confirmed the earlier statement. The lightcurve is unstabil as was suspected to be the case from the large dispersion of the individual RV's from the mean velocity curve. 6. HD 74375 - this single lined spectroscopic binary was suspected by the author to be also a beta CMa star, a suspicion that arose from the dispersion of the individual RV's around the mean orbital curve and from the very sharp spectral lines. (Van Hoof, Med.Kon.Ac. Wet., en Sch.K. v. Belgie, XXXIV, no. 4, 1972.) Observations made this year at Boyden with the 60" show indeed a variation of the difference m(HD 74375)-m(HD 75086) by 0.02m. The period could not be derived because the runs obtained were too short. There is a fair chance that the star is also an eclipsing binary. [FIGURE 1] Figure 1. - Observed lightchanges in HD 55958. Absc.: Sid. Time Bloemfontein (lambda_Bfn = 1h45m E). Ord.: m_v (omega Cma - HD 55958). Full details about the observations of stars 1,3 and 5 of the list will be published in one of the forthcoming numbers of the Medede- lingen van de Koninklijke Academie voor Wetenschappen, Letteren en Schone Kunsten van Belgie. [FIGURE 2] Figure 2. - Lightchanges in HD 57219 observed in the night 1970 Jan 14/15 Absc.: Sid. Time La Silla (lambda_LS = 4h43m W). Ord.: m_v (HD 57219 - HD 56733); add - 1m for step difference. A. VAN HOOF Astronomisch Instituut K.U.L. Naamsestraat 61 B-3000 LEUVEN, Belgium