COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 932 Konkoly Observatory Budapest 1974 October 14 PHOTOELECTRIC MONITORING OF THE FLARE STAR AD LEO The results of photoelectric observations of the flare star AD Leo, made through a standard B filter, are presented. Two flares were detected during photoelectric monitoring of the star over a total of 32h35n, spread over 14 nights during period 20 Nov 1973- 26 April 1974. The records of effective coverage are given in Table I. The details of the characteristics of the flare events are given in Table II. The flare characteristics of AD Leo were computed using the same techniques and procedures as those employed earlier by Kanoor, Sanwal, Sinvhal (1973, I.B.V.S. No. 810). For energy calculations the quiescent state luminosity of the star was taken to be 8.2 x 10^29 ergs sec^{-1} 100A^{-1} in the B filter with reference to Oke and Schild's (1970, Astrophys. J. 161, 1015) calibration of alpha Lyr. The light curves of the flares are shown in Figs 1 and 2. Both light curves are combinations of spike and slow flares as characterized by Moffett (1974, Sky and Telescope, 48, 94). One can see that before a flare starts, the brightness of the star undergoes dimming, as it often happens in most of the flares, of UV Ceti type. The declining branch of the flare in Fig. 1 could not be covered up to pre-flare brightness of the star. The flares correspond, nearly to type II flares (Oskanyan, 1969, Non-Periodic Phenomena in Variable Stars Ed. L. Detre, Academic Press, Budapest, p. 131). The author is thankful to Dr. S. D. Sinvhal for suggestions and guidance. Part of this work was carried out with financial assistance with PL 480 funds under Smithsonian Institution. Project No SFG-0-6425. [FIGURE 1] [FIGURE 2] Table I Coverage of AD Leo Date 1973 Telescope (Times rounded off to nearest minute of UT) 20 Nov. 52 cm 19h53m-20h00m 20h04m-08m 20h09m-11m 21 12 -18 20 20 -32 20 33 -46 20 43 -21 00 21 01 -11 21 12 -15 21 19 -21 21 23 -25 21 27 -29 21 30 -33 21 35 -40 21 44 -50 21 57 -22 01 22 02 -04 22 06 -09 22 10 -12 22 13 -17 22 20 -22 13 Dec. 56 cm 19 15 -32 19 34 -41 19 45 -55 19 57 -20 00 20 01 -02 20 03 -11 20 12 -15 20 16 -19 20 20 -27 21 09 -17 21 18 -34 14 Dec. 56 cm 18 34 -39 18 41 -47 18 48 -52 18 53 -19 01 19 04 -24 19 25 -32 19 53 -20 00 20 01 -04 20 05 -12 20 12 -32 20 54 -21 17 - 15 Dec. 56 cm 18 04 -09 18 12 -14 18 15 -20 18 21 -25 18 30 -36 18 41 -54 18 55 -57 19 02 -08 19 09 -22 19 24 -30 19 45 -20 06 20 15 -39 20 40 -42 _20 43 -48_ 20 49 -52 21 00 -04 - - 25 Dec. 56 cm 18 05 -10 18 11 -15 18 16 -19 18 21 -30 18 33 -45 19 25 -52 19 53 -20 01 20 02 -15 20 16 -29 26 Dec. 56 cm 17 05 -09 17 11 -22 17 24 -33 17 34 -41 17 42 -45 17 53 -57 17 58 -18 10 18 12 -25 18 27 -42 18 43 -45 18 46 -51 18 52 -57 19 00 -11 19 12 -17 19 20 -45 19 46 -51 19 52 -55 19 56 -20 00 20 01 -10 20 11 -22 20 23 -38 _20 40 -50_ 20 51 -21 03 21 04 -22 27 Dec. 56 cm 16 50 -54 16 55 -57 17 02 -03 17 04 -08 17 09 -15 17 16 -22 17 23 -30 17 32 -18 03 13 04 -08 18 20 -41 18 42 -46 18 47 -59 19 06 -17 19 22 -42 19 43 -50 19 50 -20 06 20 07 -09 20 21 -31 20 33 -40 20 41 -43 20 45 -49 20 49 -21 02 21 Jan. 1974 52 cm 19 12 -21 19 32 -44 20 19 -23 24 Jan. 52 cm 15 32 -40 15 47 -16 09 16 21 -39 16 59 -17 14 17 15 -18 17 23 -33 17 34 -41 17 42 -18 20 18 24 -41 18 46 -58 31 Jan. 52 cm 15 31 -37 15 48 -16 00 16 01 -09 16 10 -12 16 13 -15 16 15 -29 16 30 -45 16 46 -52 16 54 -17 42 17 50 -59 18 47 -19 13 19 14 -33 19 34 -39 19 41 -20 07 20 08 -30 20 31 -35 Table I (continued) Date 1974 Telescope (Times rounded off to nearest minute of UT) 10 Apr. 56 cm 16h18m-20m 16h22m-28m 16h29m-40m 16 42 -46 16 47 -53 18 02 -20 18 22 -46 18 47 -19 07 19 08 -26 19 27 -30 19 31 -44 19 45 -50 19 51 -58 19 59 -20 26 11 Apr. 56 cm 16 01 -08 16 09 -22 16 26 -56 16 57 -17 12 17 13 -18 12 Apr. 56 cm 15 37 -58 15 59 -16 19 16 21 -55 16 57 -17 15 17 18 -25 17 33 -18 14 18 15 -43 18 44 -52 18 59 -19 14 19 15 -33 19 38 -50 19 55 -20 18 20 19 -31 26 Apr. 56 cm 17 13 -30 17 31 -44 17 45 -18 02 18 03 -13 18 15 -18 18 29 -42 18 44 -58 18 59 -19 14 19 15 -23 19 24 -35 19 37 -44 Note: 1. The flare intervals have been underlined. 2. Total coverage: 32h35m spread over 14 nights. 3. Photomultiplier used: 1P21, unrefrigerated. Table II Characteristics of the flares on AD Leo (dM4e : V=9m.43; U-V=2m.61) Date UT Flare X_{fm+s}/ delta(m) sigma/ P F(z) Energy Total 1973 max duration /X_s /X_s (min) released emission before after at flare max max max during tb ta (10^29 the ergs/s) flare up (10^30 ergs/s) 15 Dec.20h20m03s 2.2 3 1.651 .544 .031 0.32 1.254 7.58 8.82 26 Dec.20 43 44 3.4 13 1.276 .265 .079 0.54 1.190 5.86 14.88 Note: For notation see Oskanyan (1970, I.B.V.S. No. 488). Uttar Pradesh State Observatory Manora Peak Naini Tal 263129, India. B. B. SANWAL