COMMISSION 27 OF THE I.A.U. INFORMATION BULLETIN ON VARIABLE STARS Number 1486 Konkoly Observatory Budapest 1978 October 17 PHOTOELECTRIC OBSERVATIONS OF THE FLARE STAR AD Leo IN 1974 Continuous photoelectric monitoring of the flare star AD Leo has been carried out at the Stephanion Observatory (lambda=-22d49'49", phi=+37d45'15") during the year 1974 using the 30-inch Cassegrain reflector of the Department of Geodetic Astronomy, University of Thessaloniki. Observations have been made with a Johnson dual channel photoelectric photometer in the B colour of the international UBV system. The telescope and photometer will be described elsewhere. Here we mention only. that the transformation of our instrumental ubv system to the international UBV system is given by the following equations: for the time interval from 16-1-1974 to 9-4-1974 V = v_0 + 0.030 (b-v)0 + 1.756, B-V = 0.845 + 1.042 (b-v)0, U-B =-1.778 + 1.102 (u-b)0, and from the time interval from 17-4-1974 to 26-5-1974 V = v_0 - 0.011(b-v)0 + 2.445, B-V = 0.848 + 0.992(b-v)0, U-B =-1.632 + 0.999(u-b)0. The monitoring intervals in UT as well as the total monitoring time for each night are given in the Table I. Any interruption of more than one minute has been noted. In the fourth column of Table I the standard deviation of random noise fluctuation sigma(mag) = = 2.5 log(I0+a)/I0 for different times (UT) of the corresponding monitoring interval is given. During the 40.85 hours of monitoring time 8 flares were - served the characteristics of which are given in Table II. For each flare following characteristics (Andrews et al., 1969) are given: a) the date and universal time of flare maximum, b) the duration before and after the maximum (tb and ta, respectively), as well as the total duration of the flare, c) the value of the ratio (If-I0)/I0 corresponding to flare maximum, where I0 is the intensity deflection [FIGURE 1] [FIGURE 2] [FIGURE 3] [FIGURE 4] [FIGURE 5] [FIGURE 6] [FIGURE 7] [FIGURE 8] Flare Star AD Leo, 1974 Table II Characteristics of the Flares Observed Date Flare 1974 U.T. t_b t_a Duration (If-I0)/I0 P sigma Air No. January max. min. min. Min max. min Deltam Mass 1 16 23h01m04? 0.44? 7.52? 7.96? 0.175? 0.352? 0.175? 0.01 1.373 1.379 2 17 01 36.00? -- >7.0 -- >0.4 >0.682 -- 0.01 1.058 3 17 2 25.20 0.68 1.52 2.20 0.088 0.072 0.092 0.02 1.104 4 23 22 37.01 0.64 5.52 6.16 0.784 0.619 0.628 0.01 1.168 February 5 10 20 43.70 1.20 20.50 21.70 0.630 2.240 0.530 0.01 1.290 April 6 18 00 14.14? 1.76 30.88 32.64 10.890? 29.574 2.688? 0.02 2.689 7 19 21 41.30 0.60 14.56 15.56 0.492 1.025 0.435 0.01 1.300 May 8 12 20 44.00? -- -- -- >0.280 >0.915 >0.265 0.01 1.444 less sky background of the quiet star and If is the total intensity deflection less sky background of the star plus flare, d) the integrated intensity of the flare over its total duration, including pre-flares, if present, p = f(If-I0)/I0dt, e) the increase of the apparent magnitude of the star at flare maximum Delta m(b)=2.5 log(If/I0), where b is the blue magnitude of the star .in the instrumental system, f) the standard deviation of random noise fluctuation a(mag)= = 2.5 log(I0+a)/I0 during the quiet - state phase immediately preceding the beginning of the flare and g) the air mass at flare maximum. The light curves of the observed flares in the b colour are shown in Figs. 1-8. M.E. CONTADAKIS, G. KAREKLIDIS L.N. MAVRIDIS, D. STAVRIDIS, H. ZERVAKI-ZOEROU Department of Geodetic Astronomy University of Thessaloniki Reference: Andrews, A.D., Chugainov, P.F., Gershberg, R.E. and Oskanian, V.S.: 1969, I.B.V.S. No. 326 Flare Star AD Leo, T a b l e 1 Date Monitoring intervals (U.T.) Total Monitoring L (U.T.) 1974 Time January 16 23h00m.64-23h09m, 23h14m-23h23m, 0.01(23h33m) 23 25-23 36, 23 39-24 00, 49m.36 17 00 00-00 09.40, 00 12.05-00 17 0.01(00h07m), 0.01(00h38m), 00 24-00 41, 01 36-02 01, 0.01(01h58m), 0.02(02h17m), 02 03-02 15, 02 17-02 30, 0.01(02h47m), 0.02(03h21m), 02 34-03 06, 09 08-03 14, 0,02(03h58m), 0.02(23h16m), 03 21-04 01, 22 53-23 18, 0,02(23h47m). 23 22-23 33, 23 37-24 00. 3h37m,9 18 00 00-00 08, 00 13-00 19, 0.01(00h31m), 0.01(01h29m), 00 22-00 38, 01 25-01 45, 0.02(02h00m), 0.01(02h40m). 01 49-02 15, 02 18-02 47. 1h45m 20 22 14-22 47, 22 51-23 11. 53m 0.02(22h16m), 0.02(22h53m), 23 22 29-22 51, 22 54-22 58, 0.01(22h34m), 0.02(23h07m), 23 04-23 26, 23 33-23 50. 1h05m 0.01(23h45m). February 10 20 25-20 53, 20 56-21 22, 0.01(20h39m), 0.01(21h09m), 21 27-21 50, 22 00-22 94, 0.02(21h41m), 0.01(22h15m), 22 41-23 11, 23 15-23 38. 2h44m 0.01(23h01m), 0.01(23h29m). 11 00 38-01 05, 01 10-01 37, 0.01(00h58m), 0.02(01h28m), 01 41-02 18. 1h31m 0.02(02h00m). April 3 22 05-22 39, 22 39-23 03, 0.11(22h28m), 0.12(22h43m), h m h m 23 07-23 37. 1h22m 0.15(23h13m). 7 19 30-19 59, 20 00-20 30, 0.03(19h38m), 0.04(20h12m), 20 39-21 02, 21 22-21 47, 0.04(20h58m), 0.04(21h44m), 21 51-22 23, 22 28-22 59. 2h53m 0.05(22h17m), 0.05(22h56m), 9 20 15-20 43, 20 48-20 58, 0.02(20h36m), 0.03(21h48m), 21 29-22 00, 22 14-22 43, 0.02(22h94m), 0.03(23h09m). 22 46-22 50, 22 57-28 14. 1h59m 17 22 20-22 51, 23 22-23 51, 0.01(22h35m), 0.0(23h27m). 29 54-24 00. 1h06m 18 00 00-00 46. 46m 0.02(00h11m). 19 20 30-20 59, 21 03-21 30, 0.01(20h47m), 0,01(21h14m), 21 34-21 59 ,22 13-22 45, 0.01(21h39m), 0,01(22h28m), 22 49-23 25, 23 28-24 00, 3h01m 0.01(23h02m), 0,02(23h44m). 20 00 00-00 02. 2m 23 20 30-20 58, 21 01-21 31, 0.01(20h34m), 0,01(21h18m), 21 34-22 08, 22 18-22 50, 0.01(21h48m), 0,01(22h38m), 22 59-29 19. 2h25m 0.01(23h04m). May 7 21 22-21 31, 21 32-21 45, 0.02(21h35m), 0.02(22h05m) 21 51-22 00, 22 01-22 14, 0.03(22h36m). 22 30-22 39, 22 42-22 51, 23 07-23 16, 23 19-28 26, 1h18m 19 47-19 54, 19 56-20 02, 0.01(20h00m), 0.01(20h24m), 20 05-20 13, 20 18-20 30, 0.02(21h41m), 0.02(22h16m). 21 39-21 49, 21 53-22 02, 22 11-22 20. 1h01m 10 20 09-20 18, 20 20-20 27, 0.01(20h25m). 20 29-20 36 23m 11 15 19-19 25, 19 27-19 33, 0.01(19h30m), 0.01(20h02m), 19 35-19 47, 19 51-19 58, 0.01(20h56m), 0.01(21h40m), 19 59-20 06, 20 08-20 18, 0.02(22h10m), 0.03(22h40m). 20 22-20 34, 20 40-20 48, 20 53-21 04, 21 21-21 31, 21 34-21 49, 21 46-21 55, 22 00-22 05, 22 07-22 15, 22 20-22 26, 22 35-22 43, 22 46-22 53. 2h21m 12 20 06-20 16, 20 19-20 28, 0.01(20h22m), 0.02(21h06m). 20 29-20 40, 20 44-20 53, 20 57-20 59, 21 03-21 13, 21 15-21 23, 21 26-21 37, 1h10m 13 19 42-19 55, 19 56-20 03, 0.01(19h57m), 0.01(20h26m), 20 07-20 19, 20 22-20 34, 0.01(20h43m) 20 39-20 49, 20 52-21 02, 21 03-21 14. 1h15m 14 19 57-20 05, 20 10-20 16, 0.01(20h13m), 0.02(20h44m), 20 19-20 26, 20 31-20 40, 20 43-20 52, 20 56-21 02. 45m 17 19 53-20 00, 20 03-20 09, 0.01(20h21m), 0,01(20h38m), 20 11-20 17, 20 18-20 31, 0.02(21h19m). 20 35-20 43, 20 45-20 54, 20 55-21 01, 21 05-21 13, 21 15-21 22, 21 24-21 31. 1h17m 22 19 32-19 40, 19 44-19 52, 0.01(19h56m), 19 54-20 02, 20 04-20 13. 33m 23 19 37-19 44, 19 46-19 51, 0.02(19h49m), 0.02(20h24m), 19 59-19 58, 20 01-20 07, 0.02(20h59m). 20 12-20 19, 20 21-20 29, 20 31-20 37, 20 46-20 53, 20 56-21 01, 21 04-21 10, 21 14-21 22. 1h10m 24 19 43-19 51, 19 53-19 59, 0.01(19h56m), 0.01(20h38m), 20 02-20 12, 20 14-20 22, 0.01(21h08m), 20 25-20 33, 20 35-20 43, 20 45-20 52, 20 58-21 04, 21 06-21 15, 21 17-21 25, 21 28-21 32. 1h22m 25 19 49-19 59, 20 03-20 14, 0.01(20h06m), 0.02(20h46m), 20 17-20 25, 20 31-20 36, 0.02(21h22m). 20 38-20 42, 20 44-20 49, 20 51-20 57, 21 02-21 06, 21 10-21 17, 21 20-21 25, 21 31-21 36, 21 40-21 46. 1h16m 26 19 54-20 05, 20 07-20 15, 0.01(20h21m), 0.02(20h35m). 20 17-20 27, 20 30-20 40, 20 43-20 52, 20 55-21 03, 21 06-21 11. 1h01m Total 40h51m