COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1897 Konkoly Observatory Budapest 1980 December 28 HU ISSN 0374-0676 FLARE ACTIVITY OF V914 Sco V914 Sco (= CSV2851) was shown to be a BY Dra-type variable (Busko, Quast and Torres, 1977), with a B amplitude of about 0.15 mag and probable period of 2.69 days. Herbig (1977) called attention to its duplicity, quoting an M3eV spectral type for the brighter component and M4eV for the fainter one. We estimated, based on photoelectric scans with small diaphragm, a difference of about 2 mag in the visual for the two components. In 4 nights between April and June 1980, the star was monitored photoelectrically in the U band with the 1.6m telescope of Brazilian Astrophysical Observatory. A photometer with DC strip chart recording was used. Both components of the pair were included in the diaphragm. Following the precepts of Kunkel (1973), flare light was referred not to the quiescent state of the star, which is poorly determined in ultraviolet, but to suitable comparison stars. The rate of occurrence of flares of peak magnitude less than U can be described by R = exp(U-U_o), with the parameter U_o being a measure of the level of flare activity. Table I - Coverage JD U.T. 2444000+ From - To 352.5 6h16.0m - 7h27.0m, 7h28.4m - 8h 0.4m 358.5 5 22.0 - 5 49.0 , 5 50.1 - 6 30.3 ,6h50.5m - 7h02.1m 7 04.4 - 7 23.2 , 7 24.6 - 7 38.0 ,7 39.8 - 8 03.2, 8 04.5 - 8 16.9 , 8 18.3 - 8 22.0 365.5 4 41.2 - 5 01.8 , 5 02.8 - 5 53.2 ,5 54.3 - 6 15.5, 6 16.7 - 6 56.5 , 6 57.6 - 8 00.2 380.5 3 53.3 - 3 57.0 , 4 00.0 - 4 14.0 ,4 15.5 - 4 46.6, 4 47.8 - 5 10.2 , 5 11.3 - 5 25.5 ,5 26.5 - 6 05.3 In a total coverage time of 9.54 hours, 28 events with U_peak<16.5 were observed. Tables I and II summarize the data. The meaning of the symbols is the same as in Busko and Torres (1976). A value of U_o = 14.6 +- 0.2 can be derived from this sample, using only the events above the completeness threshold U_faint = 15.2 (Figure 1 ). There is no published trigonometric parallax far this star. If we adapt a distance modulus of 0.5 mag supposing it to be a main sequence star, we obtain an absolute value for the activity M_u,o = 14.1. Table II - Event Data JD Sec z U T_0.5 T_0.2 Obs 2444000+ (min) (min) 352.765 1.048 13.86 .65 .800 1.088 13.39 .40 4.u .772 1.053 15.72u 1.u L .814 1.116 15.49u 1.u L 358.733 1.043 15.07 2.1 .740 1.045 15.58 3.3u .746 1.047 14.33 .20 1.3 .751 1.049 15.26 .16 .756 1.053 15.96u .15u L .762 1.059 13.94 .54 I .789 1.098 16.44u .7u L .826 1.200 14.94 .90 .830 1.217 15.93 .36 .825 1.197 14.91 1.28 365.699 1.045 12.75 1.32 5.12 .708 1.043 15.76 .4u L .720 1.044 14.35 2.8u .76u 1.074 15.44 L .776 1.111 13.17 1.5 .789 1.141 16.03u 3.1u L .806 1.198 14.87 .50 .808 1.205 14.19 .20 .813 1.223 15.43 1.4u I .819 1.250 15.05 > .90 I .824 1.272 14.97 1.40 380.667 1.043 15.93u >2.1 I .673 1.043 16.46 3.1 .709 1.066 13.61 3.0 5.6 D Even if we assume that the activity is equally divided between the two components, this would be a high activity at this spectral [FIGURE 1] Figure 1: Cumulative rate of occurrence (in hr^{-1} ) of flares brighter than magnitude U in V914 Sco. type, although the activity of BY Dra stars is in general high (Busko and Torres, 1978). Such a high activity has been found only in Gliese 182 (de la Reza, Torres and Busko, 1981). I.C. BUSKO F.J. JABLONSKI G.R. QUAST C.A.O. TORRES CNPq/Observatorio Nacional Observatorio Astrofisico Brasileiro 37.500 - Itajuba - (MG) Brasil References: Busko, I.C., Torres, C.A.O., 1976, I.B.V.S. No. 1186 Busko, I.C., Quast, G.R., Torres, C.A.O., 1977, I.B.V.S. No. 1275 Busko, I.C., Torres, C.A.O., 1978, Astron. Astrophys. 64,153 [BIBCODE 1978A&A....64..153B ] Herbig, G.H., 1977, I.B.V.S. No. 1323 Kunkel, W.E., 1973, Astrophys. J. Suppl. 25,1 [BIBCODE 1973ApJS...25....1K ] de la Reza, R., Torres, C.A.O., Busko, I.C., 1981, Monthly Not. Royal Astr. Soc. (in press) [BIBCODE 1981MNRAS.194..829D ]