COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1653 Konkoly Observatory Budapest 1979 August 1 PHOTOELECTRIC OBSERVATIONS OF THE FLARE STAR EV Lac IN 1974 Continuous photoelectric monitoring of the flare star EV Lac has been carried out at the Stephanion Observatory (lambda=-22d49'44" phi=+37d45'15") during the years 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 2-6-1974 to 12-8-1974 V = v_0 + 0.053 (b-v)_0 + 2.380, (B-V)= 0.858 + 1.043(b-v)_0, (U-B)=-1.782 + 1.020(u-b)_0, and for the time interval from 13-8-1974 to 31-10-1974 V = v_0 - 0.018(b-v)_0 + 2.297, (B-V)= 0.886 + 1.004(b-v)_0, (U-B)=-1.818 + 0.974(u-b)_0. The monitoring intervals in UT as well as the total monitoring time for each night are given in 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(I_0+sigma)/I_0 for different times (UT) of the corresponding monitoring intervals is given. During the 74.55 hours of monitoring time 23 flares were observed the characteristics of which are given in Table II. For each flare the following characteristics (Andrews et al., 1969) are given: a) the date and universal time of flare maximum, b) the duration before and after maximum (t_b and t_a, respectively), as well as the total duration of the flare, c) the value of the Flare Star EV Lac, 1974 T a b l e I -------------------------------------------------------------------------------- Date Monitoring intervals(U.T.) Total Monitoring sigma(U.T.) -------------------------------------------------------------------------------- 1974 Time July 10-11 23h34m-23h58m,0001-0035, 0038-0113, 1h333m 0.02(23h47m),0.02(00h13m), 0.02(00h52m). 11-12 2321-2357, 0001-0022, 0024-0038, 0.03(23h36m),0.02(00h17m), 0043-0120, 1h48m 1.02(00h46m ,0.02(01h15m) 13 0033-0100, 0103-0133 0h57m 0.01(00h46m),0.01(01h23m), 16-17 2331-0001,0004-0032,0034-0106, 0.01(23h47m),0.01(00h15mm), 1h30m 0.01(00h55m). 17-18 2301-2332,2334-0008,0011-0039, 0.01(23h22m),0.01(00h00m) 0041-0109 2h01m 0.01(00h24m),0.01(00h50m). 18-19 2216-2247,2251-2326,2328-2359, 0.01(22h38m),0.01(23h16m), 0010-0038, 0041-0108,0114-0121. 2h39m 0.01(23h46m),0.01(00h24m), 0.01(00h54m). August 7-8 22h11m-22h40m,2242-2308,2311-2340, 0.03(22h12m),0.04(22h45m), 2354-0020.0022-0049,0052-0118. 2h43m 0.03(23h13m),0.03(23h39m), 0.03(00h13m),0.03(00h48m) 0.03(01h16m). 9-10 2035-2192,2105-2137,2148-2217, 0.02(20h37m),0.02(21h06m), 2227-2248,2250-2320,2931-2359, 0.02(21h49m),0.02(22h28m), 0043-0114. 3h10m, 0.02(22h54m),0.02(23h32m), 0.02(23h58m),0.02(00h44m), 0.02(01h13m), 10-11 2239-2306,2308-2332,2335-0008, 0.02(22h40m),0.02(23h10m), 0021-0044,0047-0120. 2h20m 0.02(23h47m),0.02(00h22m), 0.02(00h53m),0.02(01h16m). 11-12 2012-2040,2042-2112,2115-2144, 0.01(20h13m),0.02(21h18m), 2159-2227,2230-2259,2303-2330, 0.01(21h43m), 0012-0057,0059-0119. 3h56m 0.02(23h28m),0.02(00h16m). 13-14 1947-2012,2016-2043,2049-2054, 0.02(19h49m),0.01(20h16m), 2056-2124,2135-2207,2210-2239, 0.02(20h52m),0.02(21h23m), 2242-2309,2329-2348,0031-0051, 0.02(22h00m),0.02(22h34m), 0054-0119. 3h57m 0.02(23h05m),0.02(23h37m), 0.01(00h42m),0.02(01h08m). 14 1956-2017,2019-2029,2031-2059, 0.02(19h57m),0.02(20h33m), 2102-2131. 1h28m 0.01(21h04m),0.02(21h30m). 22-23 1935-2001,2003-2033,2036-2102, 0.02(19h37m),0.02(20h05m) 2122-2152,2200-2224,2225-2300, 0.02(20h32m),0.01(21h01m), 2347-0017. 3h21m 0.01(21h34m),0.02(22h06m), 0.01(22h38m),0.02(23h59m), 23-24 1905-1932, 1934-1958,2000-2031, 0.02(19h07m),0.02(19h37m), 2043-2110,2112-2143,2148-2209, 0.01(20h11m),0.01(20h56m), 2220-2248,2251-2312,0005-0028, 0.01(21h25m),0.01(22h00m), 0031-0102,0104-0137. 4h58m 0.01(22h36m),0.01(23h04m), 0.01(00h05m),0.02(00h45m), 0.02(01h15m). 24-25 1925-1952, 1955-2026,2029-2056, 0.02(19h39m),0.02(20h09m), 2107-2141,2144-2205,2208-2236, 0.02(20h39m),0.02(21h15m), 2249-2311,0003-0018, 3h25m 0.01(22h00m),0.02(22h30m) 0.02(23h03m),0.02(00h06m). 25-26 1938-2002,2005-2034,2036-2105, 0.03(19h52m),0.03(20h22m), 2116-2141,2144-2214,2217-2244, 0.02(20h56s),0.02(21h30m), 2257-2317,0011-0033,0036-0109, 0.02(20h00m),0.02(22h30m), 0112-0138. 4h25m 0.02(23h00m),0.02(00h20m) 0.01(00h52m),0.01(01h20m), 31 2040-2110,2113-2142,2144-2215, 0.04(20h44m),0.04(21h16m), 2228-2257,2307-2325. 2h17m 0.04(21h47m),0.04(22h31m), September 0.04(23h11m), 2-3 1941-2014,2017-2021,2026-2048, 0.04(19h45m),0.04(20h19m), 2051-2121.2134-2202,2205-2238, 0.04(20h54m),0.04(21h39m), 2240-2309,0000-0029,0032-0102. 3h58m 0.03(22h11m),0.03(22h43m), 3-4 2050-2115,2909-2335,2343-0010, 0.03(20h55m),0.04(23h16m), 0013-0043,0058-0109. 1h59m 0.04(23h46m),0.04(00h16m), 0.03(01h00m). 4-5 2123-2154,2157-2224,2226-2256, 0.02(21h27m),0.02(22h01m), 2345-0015,0017-0045,0047-0115. 2h54m 0.02(22h31m),0.03(23h48m), 0.03(00h20m),0.03(00h50m). 5-6 2026-2052,2055-2123,2126-2153, 0.03(20h30m),0.02(21h00m), 2206-2223,2322-2347,2350-0019, 0.03(21h31m),0.03(22h09m), 0022-0051,0053-0111, 3h19m 0.05(23h26m),0.03(23h54m), 0.04(00h27m),0.05(00h57m). 6-7 2107-2134,2137-2205,2208-2235, 0.04(21h10m),0.02(21h40m), 2328-2356,2358-0025,0028-0101. 2h50m 0.02(22h12m),0.02(23h31m), 0.02(00h02m),0.02(00h31m). 9-10 2024-2051,2054-2125,2127-2156, 0.01(20h29m),0.01(20h59m), 2236-2303,2306-2340,2344-8801, 0.01(21h30m),0.01(22h40m), 0003-0013,0025-0054,0057-0122, 3h49m 0.01(23h27m),0.01(00h06m), 0.01(00h36m),0.02(01h03m). 14 2026-2056,2059-2129,2216-2245, 0.01(20h31m),0.01(21h00m), 2247-2315,2918-2322,2326-2347. 2h22m 0.01(22h19m),0.01(22h55m), 0.01(23h28m). 15 2013-2040,2043-2110,2113-2140, 0.01(20h17m),0.01(20h56m), 2227-2249,2252-2316,2319-2329, 0.01(21h27m),0.01(22h40m), 2333-2350, 2h34m 0.01(23h09m),0.02(23h44m). 17 1956-2024,2027-2055,2057-2131, 0.01(19h58m),0.01(20h28m), 2220-2234,2236-2305. 2h13m 0.02(21h00m),0.02(22h25m), 0.01(22h39m). 0.01(20h26m), 19 1951-2020,2022-2039,2041-2121, 0.02(19h53m) 2220-2253. 1h59m 0.02(20h45m),0.01(22h23m). ---------------------------------------------------------------------------------- Total 74h33m ---------------------------------------------------------------------------------- Flare Star EV Lac, 1974 Table II Characteristics of the Flares Observed -------------------------------------------------------------------------------------------- Date Flare 1974 U.T. t_b t_a Duration I_f-I_0/I_0 P Delta m sigma Air No. July max. min. min. min. max. min. mag. mag. mass -------------------------------------------------------------------------------------------- 1 11 00h54.2m 0.5 1.8 2.3 0.09 0.09 0.10 0.02 1.03 2 13 01 26.75 0.35 1.15 1.5 0.08 0.04 0.09 0.01 1.01 3 18 00 02.3 0.2 5.7 5.9 0.14 0.15 0.14 0.01 1.05 August 4 10 22 56.65 2.0 3.9 5.9 0.10 0.18 0.11 0.02 1.03 5 10 23 49.6 0.5 3.4 3.9 0.18 0.21 0.17 0.02 1.01 6 11 00 04.0 2.9 3.3 6.2 0.10 0.22 0.10 0.02 1.01 7 11 01 17.8 0.2 0.7 0.9 0.08 0.04 0.08 0.02 1.02 8 11 22 49.5 0.3 9.4 9.7 2.51 1.92 1.37 0.02 1.03 9 12 00 35.5 1.0 46.0 47.0 1.07 4.81 0.80 0.02 1.04 10 23 20 17.9 0.9 1.8 2.7 0.08 0.08 0.08 0.01 1.18 11 24 00 55.2 0.4 2.8 3.2 0.17 0.18 0.17 0.02 1.07 12 24 01 29.05 1.1 4.0 5.1 0.28 0.37 0.27 0.02 1.13 13 24 21 33.6 0.9 4.5 5.4 0.11 0.21 0.12 0.01 1.05 14 24 21 49.65 0.7 6.6 7.3 0.25 0.28 0.24 0.01 1.04 15 25 20 26.95 2.6 6.2 8.8 0.13 0.39 0.13 0.03 1.15 16 25 20 45.55 1.7 2.5 4.2 0.10 0.14 0.10 0.02 1.11 17 26 00 42.8 0.2 0.8 1.0 0.04 0.02 0.05 0.02 1.07 September 18 2 1948.6 2.0 12.8 14.8 0.93 3.75 0.71 0.04 1.04 19 5 2037.0 5.65 7.85 13.5 0.67 3.16 0.56 0.03 1.06 20 9 2329.2 1.1 4.5 5.6 0.14 0.24 0.14 0.01 1.05 21 10 0107.4 0.9 10.5 11.4 0.84 1.83 0.66 0.02 1.23 22 15 2311.6 0.5 2.8 3.3 0.18 0.16 0.18 0.01 1.06 23 15 2323.5 1.5 0.8 2.3 0.21 0.14 0.21 0.01 1.07 -------------------------------------------------------------------------------------------- 6 ratio (I_f-I_0)/I_0 corresponding to flare maximum, where I_0 in the intensity deflection less sky background of the quiet star and I_f 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=Integral(I_f-I_0)/ I_0 dt, e) the increase of the apparent magnitude of the star at flare maximum Delta m(b)=2.51log(I_f/I_0),Where b is the blue magnitude of the star in the instrumental system, f) the standard deviation of random noise fluctuation sigma(mag)=2.5 log(I_0+sigma)/I_0 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. 1-23. M.E. CONTADAKIS, G. KAREKLIDIS L.N. MAVRIDIS, A.C. TSIOUMIS 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 [FIGURE 1] [FIGURE 2] [FIGURE 3] [FIGURE 4] [FIGURE 5] [FIGURE 6] [FIGURE 7] [FIGURE 8] [FIGURE 9] [FIGURE 10] [FIGURE 11] [FIGURE 12] [FIGURE 13] [FIGURE 14] [FIGURE 15] [FIGURE 16] [FIGURE 17] [FIGURE 18] [FIGURE 19] [FIGURE 20] [FIGURE 21] [FIGURE 22] [FIGURE 23]