COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1572 Konkoly Observatory Budapest 1979 March 21 PHOTOELECTRIC OBSERVATIONS OF AD Leo The results of photoelectric monitoring of the flare star AD Leo, made through a standard B filter are reported herein. Four flares were detected during a total of 17h28m monitoring, spread over 7 nights. All flare events were observed using the 104-cm reflector equipped with a refrigerated EMI 6094S photomultiplier. Flare events of 12 February 1977 are within the programme of Cooperative flare star observations for 1977 (Mavridis, 1977). The flare light curves (Figs. 1-4), monitoring intervals (Table 1) and flare characteristics (Table 2) are presented. Energy released during a flare event is computed using the following equation (Cristaldi and Rodono, 1973): E_B = 4 pi d^2 x 10^-0.4mB x pi_B x 60 x P_B ergs Where d is the distance of the star, m_B its apparent magnitude in B colour, pi_B the energy flux produced by a zero magnitude star outside the terrestrial atmosphere which is taken Table 1 Monitoring Intervals (Times rounded off to nearest minute of U.T.) ---------------------------------------------------- Date Telescope 1976 Feb.29 104-cm 16h12m-17h04m 17h05m-17h33m 17 58- 18 55 18 56- 19 14 19 20- 19 34 20 03- 20 21 20 45- 21 03 1977 Feb.2 104-cm 17 32- 17 48 17 56- 18 54 10 56-cm 15 06- 15 24 15 26- 15 48 15 50- 16 12 16 13- 16 40 16 42- 17 03 18 01- 18 13 19 34- 20 02 20 26- 21 04 11 56-cm 15 14- 15 51 16 16- 17 20 12104-cm 16 48- 17 16 17 18- 21 31 1978 May 17 56-cm 17 47- 18 30 1978 Dec.23 56-cm 18 25- 18 31 18 32- 18 47 18 49- 19 07 19 08- 19 16 19 18- 19 30 --------------------------------------------------- [FIGURE 1] [FIGURE 2] [FIGURE 3] [FIGURE 4] Table 2 CHARACTERISTICS OF FLARE EVENTS OF AD Leo (V = 9.43, B-V = 1.54, Parallax = .204, Spectral type = dM 4.5e) ---------------------------------------------------------------------------------------------------------------- Flare duration Energy Total emission (in minutes) P_B F(z) released during the event Date U.T.max Before After Deltam_B (min) at flare 10^31ergs. max t_b max t_a (I_0+f)/I_0 sigma/I_0 max10^30ergs/s ---------------------------------------------------------------------------------------------------------------- 1976 16h54.8m 0.6 1.13 0.296 .28 .011 0.51 1.08 0.97 2.28 Feb.29 17 59.8 1.6 8.10 .585 .41 .011 1.77 1.02 1.08 7.89 1977 17 13.7 0.5 2.75 .177 .18 .010 0.10 1.05 0.87 0.45 Feb.12 17 23.7 1.1 11.00 .687 .57 .010 1.82 1.04 1.25 8.13 ---------------------------------------------------------------------------------------------------------------- 6.3 x 10^-6 ergs cm^-2 sec^-1 (Cristaldi and Rodono, 1973) and P_B= Integral [(I_0+f)/I_0 - 1] dt, where I_0+f is the intensity deflection due to the quiet star (I_0) plus that of the flare (If) at maximum. In the case of multipeaked light curves, the peaks may belong to independent flare events even when separated by small interval of time during which the relative intensity should drop to zero. Thus the energy lost during an event should be the total energy lost by numerous weaker events. The author is thankful to Dr. C.D. Kandpal for going through the manuscript. B. B. SANWAL Uttar Pradesh State Observatory Manora Peak, Naini Tal-263129 India References: Cristaldi, S. and Rodono, M., 1973, Astron.Astrophys.Suppl. 10, 47 [BIBCODE 1973A&AS...10...47C ] Mavridis, L.N., 1977, I.B.V.S. No. 1234