COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1757 Konkoly Observatory Budapest 1980 March 12 THE DELTA SCUTI VARIABLE GG Vir The star 27 Vir=GG Vir was announced to be a Delta Scuti variable with a period of 0.05d by Bartolini et al. (1975). Sterken (1977) confirmed this variability and pointed out by means of six colour photometry that the period was variable from 0.042d to 0.056d during two nights. Furthermore this star presents radial velocity variations (Palmer et al. 1968; Plaskett et al. 1922). 27 Vir was observed during 13 nights since February 7, 1975 to February 1, 1980 with the three colour photoelectric photometer described by Piccioni (1972) mounted on the 60cm reflector telescope of Bologna Observatory. 31 Vir and 33 Vir were used as comparison stars; the reductions were accomplished taking into account the colour effects of the atmosphere. The collected data were analysed by means of a program written by F. Grilli in order to search for multiperiodicities using the Barning (1963) method; the range of periods investigated was from 0.022d to 0.133d. The results for the comparison stars 31 Vir and 33 Vir are summarized in Table 1 and 2, respectively. Table I J.D. Period Amplitude R.F. 2442451. P1 0.037+-0.001 0.008+-0.002 13.3% P2 0.030+-0.001 0.006+-0.002 11.6% P3 0.064+-0.004 0.004+-0.002 6.7% 2442467. P1 0.027+-0.001 0.012+-0.002 13.7% P2 0.031+-0.001 0.008+-0.002 10.1% P3 0.056+-0.003 0.006+-0.002 7.1% 2442468. P1 0.064+-0.004 0.012+-0.002 18.5% P2 0.047+-0.002 0.012+-0.002 19.7% P3 0.027+-0.001 0.008+-0.002 12.6% Table II J.D. Period Amplitude R.F. 2442467. P1 0.027+-0.001 0.014+-0.002 24.4% P2 0.050+-0.002 0.006+-0.002 6.3% P3 0.033+-0.001 0.006+-0.002 4.3% 2442468. P1 0.059+-0.003 0.016+-0.003 24.8% P2 0.031+-0.001 0.012+-0.003 18.1% P3 0.024+-0.001 0.012+-0.003 18.7% 2442833. P1 0.030+-0.001 0.010+-0.002 18.4% P2 0.083+-0.006 0.006+-0.002 12.1% 2442836. P1 0.030+-0.002 0.008+-0.002 25.0% P2 0.083+-0.006 0.008+-0.002 20.0% P3 0.042+-0.003 0.004+-0.002 13.0% 2442837. P1 0.037+-0.002 0.007+-0.003 12.4% P2 0.061+-0.005 0.008+-0.003 17.4% 2442838. P1 0.033+-0.002 0.008+-0.003 7.0% P3 0.023+-0.001 0.006+-0.003 6.0% [FIGURE 1] In the Figure the Reduction Factor (R.F.) defined by Barning (1963) is plotted against frequency (number of cycles in 2 days) for the night of February 24, 1976. Analysing all the observations collected in the nights of February 23 and 24, 1975 together the values of the R.F. and the amplitude become smaller, as shown by Table 3. This result confirms that 27 Vir has also variable period in a time scale of one day as Sterken (1977) found. However in both nights (February 24 and 27, 1976) the same periods 0.030d and 0.083d are found. Table III J.D. Period (Days) Amplitude R.F. 2442467/8 P1 0.02745+-0.00008 0.010+-0.002 12% P2 0.0559+-0.0003 0.008+-0.002 7% P3 0.0320+-0.0001 0.006+-0.002 6% 2442833/6 P1 0.0302+-0.0003 0.008+-0.002 20% P2 0.0813+-0.0002 0.007+-0.002 12% Beside these the periods 0.027d, 0.037d and others close to 0.060d often occur. According to the formulae given by Breger and Bregman (1975) and the values M_v=1.92 and b-y=0.12 published by Breger (1979), for the fundamental period and the overtones the values P_1=0.057d, P_1=0.043d, P_2=0.035d and P_3=0.030d are deduced that fit fairly well with the observed values. C. BARTOLINI A. DAPERGOLAS A. PICCIONI M. VOLI Osservatorio Astronomico dell'Universita di Bologna via Zamboni 33 40126 Bologna, Italy References: Barning, F.J.M. 1963, Bull. Astr. Netherland 17, 22 [BIBCODE 1963BAN....17...22B ] Bartolini, C., Piccioni, A., Silveri, P., 1975, I.B.V.S. No. 981 Breger, M. 1979, P.A.S.P. 91, 5 [BIBCODE 1979PASP...91....5B ] Breger, M. and Bregman, J.N. 1975, Ap.J. 200, 343 [BIBCODE 1975ApJ...200..343B ] Palmer, D.R., Walker, E.N., Jones, D.H.R. and Wallis, R.E. 1968, Roy. Obs. Bull., No. 135 [BIBCODE 1968RGOB..135..385P ] Plaskett, J.S., Harper, W.E., Young, R.K., Plaskett, H.H., 1922, Dom. Astr. Obs. 1, 287 [BIBCODE 1921PDAO....1..287P ] Piccioni, A. 1972, Mem. Soc. Astr. It. 43, 159 [BIBCODE 1972MmSAI..43..159P ] Sterken, C. 1977, I.B.V.S. No. 1294