COMMISSION 27 OF THE I.A.U. INFORMATION BULLETIN ON VARIABLE STARS Number 1472 Konkoly Observatory Budapest 1978 September 13 A SEARCH FOR VARIABILITY OF SOME SELECTED STARS During several observing periods at the ESO site in La Silla (Chile), the He-weak-stars alpha Scl and 12 CMa, the old nova RR Pic and the T Tauri-star V380 Ori have been tested for variability, especially for short periodic oscillations. The reduction techniques were the same as described by Haefner et al. (1975). He-weak-stars are suspected to show photometric and spectroscopic variations (Jaschek et al. 1974). One of the brightest members of this group, a Scl, has been observed with a photometer in a high speed mode and a spectrum scanner (Schoembs et al. 1976). For 12 CMa only two photometric runs have been obtained. The observational data are compiled in Table l. Table 1 The observations (He-weak-stars) Photometry (H_beta wide/narrow) * Time Star Telescope Date Start(UT) Dur. Integrat. reso- (min.) time(s) lution(s) alpha Scl 60cm Bochum 1974,Nov.25 01h08m 40 1 4 1974,Dec.05 01 20 22 1 4 06 00 49 36 1 4 12 01 01 145 1 4 13 01 05 33 1 4 14 01 02 93 1 4 50cm ESO 1975,Nov.03 00 39 103 2 8 12 CMa 60cm Bochum 1974,Dec.06 04 49 38 1 4 50cm ESO 1975,Nov.02 06 05 125 2 8 Scanner (H_alpha, H_beta) Spectral Time Star. Telescope Date Start(UT) Dur. resolu- reso- (min.) tion (A) lution(s) alpha Scl 50cm ESO 1974,Nov.25 00h47m 90 7 17 1974,Dec.05 00 46 60 06 00 30 60 12 00 36 60 13 00 46 60 14 00 35 120 *) Cyclically used The longer runs have been analyzed by Fourier techniques, but no period in the range between 17 and 500 s could be detected. Night to night changes also were not evident. The r.m.s.-variation of the ratio Hbeta wide/Hbeta narrow amounts to 0.33% for Alpha Scl and to 0.18% for 12 CMa. For the mean values of the scanner equivalent widths of Halpha and Hbeta (alpha Scl) we obtained 5475+-106 mA and 5403+-38 mA, respectively. In accordance with the photometry the equivalent widths do not show any systematic variation during the observation period. To look for the 30 s - period reported for RR Pic (Warner, 1976), high speed photometric observations have been performed. Additionally (partly simultaneous) polarimetric observations were obtained. The observational data are listed in Table 2. Table 2 The observations of RR Pic Photometry (Integral) Telescope Date Start(UT) Dur. Integrat. Time resolution time (s) (s) 50cm ESO 1973,Oct. 29 06h27m 2h49m 0.99 1 30 04 21 4 00 0.99 1 1977,March 11 01 35 1 30 1 3 12 03 03 1 20 1 3 13 03 12 1 20 1 3 14 00 43 3 45 1 3 Polarimetry (Integral) Telescope Date Start(UT) Dur. I-Time/ umber of single measurements measurements 1m 1973,Oct.29 06h53m 1h20m 480 3 30 04 52 2 34 480 6 All photometric runs have been investigated for short periodic oscillations in the range from 6 to 500 s. But no significant period could be found. Polarization degree and angle show a large scatter which is enhanced at the rising part of the light curve. The mean values are P=(23 +- 31)*10E-4, Theta=15d +- 34d. The scatter, which is twice that for the comparison star, probably indicates a variability which should be confirmed by further observations. V380 Ori has been observed photometrically. The data are compiled in Table 3. Table 3 The observations of V380 Ori Telescope Date Start(UT) Dur. Integrat. Time resolution time (s) (s) 60cm Bochum 1974,Dec.06 02h10m 1h40m 1 2 50cm ESO 1974,Dec.06 02 10 1 10 1 0.99 The analysis of these simultaneous runs did not reveal a significant periodicity in the range between 6 and 500 s. R. HAEFNER K. METZ R. SCHOEMBS Universitats-Sternwarte Scheinerstr. 1 D-8000 Munchen 80 References: Haefner, R., Metz, K., Schoembs, R. 1975, Astr. & Astrophys. 38, 203 [BIBCODE 1975A&A....38..203H ] Jaschek, M., Jaschek, C. 1974, Vistas in Astronomy 16, p. 131 [BIBCODE 1974VA.....16..131J ] Schoembs, R., Spannagl, C. 1976, Astr. & Astrophys. Suppl. 26, 55 [BIBCODE 1976A&AS...26...55S ] Warner, B. 1976, IAU Symp. No. 73, p. 85 [BIBCODE 1976IAUS...73...85W ]