COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1355 Konkoly Observatory Budapest 1977 October 24 PHOTOELECTRIC OBSERVATIONS OF THE FLARE STAR BD +16d2708 IN 1973, 1974 Continuous photoelectric monitoring of the flare star BD +16d2708 has been carried out at the Stephanion Observatory (lambda=-22d49'44", phi=+37d45'15") during the years 1373, 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 6-5-1973 to 6-6-1973 V = v_0 + 0.070(b-v)_0+1.865, B-V = 0.753+ 1.030(b-v)_0, U-B =-1.379+ 1.021(u-b)_0. for the time interval from 11-5-1974 to 31-5-1974 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 Tables Ia, Ib. Any interruption of more than one minute has been noted. In the fourth column of Tables Ia, Ib the standard deviation or random noise fluctuation sigma(mag)=2.5 log(I_0+sigma)/I_0 for different times (UT) of the corresponding monitoring interval is given. During the 40.18 hours of monitoring time 1 flare was observed the characteristics of which are given in Table II. For this flare following characteristics (Andrews et.al. 1969) are given: Table Ia Monitoring Intervals in 1973 Date Monitoring Intervals Total Monitoring sigma(U.T.) 1973 (U.T.) Time May h m h m h m h m 6-7 20 50 -21 24, 21 28 -22 00 0.012(2h17m),0.021 2208-2233,2329-2338,2340-2351, (21 32),0.021(22 18), 2357-0008,0010-0021,0034-0040, 0.015(22 33),0.019 0042-0058,0108-0119,0121-0131. 02h56m (00 01),0.016(00 50) 0.016(01 16). 7-8 2046-2106,2110-2138,2142-2153, 0.019(20 59),0.023 2155-2206,2215-2238,2330-2334, (21 26),0.019(21 47), 2337-2346,2348-2357,0002-0010, 0.018(22 22),0.014 0012-0022,0027-0036,0039-0048, (23 42),0.016(00 16), 0051-0101,0109-0117,0119-0128, 0.021(00 32),0.018, 0133-0143,0145-0152. 03 15 (01 21),0.028(01 38). 8-9 2025-2039,2041,2053,2058-2130, 0.032(20 46),0.025 2133-2144,2146-2200,2202-2211, (21 07),0.020(21 56), 2256-2331,2334-2355,0000-0011, 0.020(23 25),0.017 0013-0025,0033-0046,0048-0058. 03 14 (23 50),0.021(00 17), 0.017(00 44). 10-11 2040-2106,2109-2140,2143-2157, 0.020(21 00),0.028 2159-2210,2259-2308,2310-2323, (21 23),0.022(22 02), 2327-2336,2339-2348,2351-2358, 0.019(23 16),0.019 0002-0010,0015-0025,0036-0045, (23 44),0.015(00 18), 0047-0055,0102-0111,0114-0123. 03 02 0.020(00 41),0.017 (01 16). 11-12 2040-2107,2110-2146,2149-2212, 0.028(20 47),0.024 2258-2321,2325-2331,2335-2343, (21 43),0.029(21 52), 2347-2354,0000-0008,0015-0114, 0.015(23 05),0.022 0118-0129,0132-0136. 03 01 (23 39). 21-22 2008-2020,2022-2030,2033-2048, 0.021(20 23),0.023 2049-2051,2053-2108,2111-2136, (20 58),0.024(21 25), 2138-2140,2228-2238,2241-2305, 0.034(22 55),0.031 2309-2317,2319-2340,2343-2354, (23 34),0.037(23 49), 2356-0011,0019-0042. 03 11 0.035(00 34). June 2016-2047,2049-2100,2102-2114, 0.018(20 28),0.021 1-2 2116-2123,2213-2222,2223-2229, (2104),0.021(22 36), 2231-2242,2246-2302,2303-2318, 0.022(23 06),0.025 2323-2332,2334-2347,2348-2357, (23 35),0.027(00 18), 0005-0015,0017-0027,0030-0035, 0.026(01 04). 0038-0113. 03 29 5-6 2245-2254,2256-2306,2310-2318, 0.019(23 01),0.018 2319-2329,2331-2334,2338-2345, (23 15),0.019(23 41), 2348-2356,2358-0005,0015-0024, 0.023(00 28),0.028 0026-0035,0037-0042,0045-0055, (00 59). 0057-0105. 01 43 Total 23h51m Table Ib Monitoring Intervals in 1974 Time Monitoring Intervals Total Monitoring sigma(U.T.) 1974 (U.T.) Time May 23h42m-23h45m,23h47m-00h00m, 0.019(23h 57m),0.020 11-12 0002-0011,0015-0028,0030-0042, (00 18),0.025(00 51), 0046-0058,0101-0113,0130-0140, 0.027(01 37). 0142-0147. 01h29m 12-13 2226-2229,2230-2247,2248-2303, 0.015(22 43),0.017 2306-2318,2319-2327,2329-2340, (23 24),0.021(00 02). 2344-2355,2357-0013. 01 33 14-15 2141-2210,2216-2227,2229-2245, 0.012(21 42),0.017 2249-2302,2303-2315,2317-2331, (22 22),0.015(22 51), 2347-2356,2359-0007,0009-0079, 0.016(00 02),0.021 0026-0036,0040-0050,0053-0058. 02 27 (00 32). 16-17 2124-2139,2140-2147. 22 0.013(21 33). 21-22 1938-1949,1951-2010,2038-2044, 0.017(19 53),0.016 2046-2053,2058-2118,2121-2131, (20 49),0.013(21 09), 2204-2219,2221-2244,2341-2353, 0.014(22 16),0.018 0028-0036,0039-0046. 02 18 (23 43),0.016(00 32). 22-23 2103-2125,2131-2140,2147-2200, 0.015(21 14),0.013 2250-2300,2315-2324. 01 03 (2150),0.072(22 54). 23-24 2138-2158,2203-2215,2220-2229, 0.014(21 53),0.015 2231-2246,2252-2300,2302-2309, (22 25),0.014(23 04), 2311-2323,2348-2358,0000-0009, 0.017(00 05),0.019 0012-0021,0027-0031,0034-0040, (00 36),0.019(01 04). 0100-0106,0110-0118. 02 15 24-25 0029-0037,0039-0046,0048-0056, 23 0.014(00 41). 25-26 2205-2220,2222-2233,2235-2245, 0.016(22 27),0.014 2250-2300,2303-2316,2323-2333, (23 06),0.013(23 40), 2336-2341,2344-2355,0011-0020. 07 34 0.018(00 16). 26-27 2126-2147,2148-2201,2204-2239, 0.016(21 54),0.014 2242-2254,2255-2305,2307-2320, (22 08),0.015(23 00), 2334-2347,2348-2359,0001-0011. 02 18 0.018(2352). 28-29 2227-2240,2242-2254,2301-2313, 0.022(22 33),0.015 2315-2332,2340-2350,2356-0005, (23 07),0.018(23 59), 0028-0032,0034-0042,0047-0054. 01 32 0.017(00 36). 30-31 1953-1959,2002-2020,2022-2036, 0.026(20 14),0.028 2040-2108. 01 06 (20 47). Total 18h20m Table II Characteristics of the Flare Observed Date 1974 UT max t_b t_a Duration (I_f-I_0)/I_0 P Delta m sigma Air May max. min. min. min. max. min. mag. mag. Mass 14 21h53.2m 2.2 14.8 17.0 0.35 1.53 0.33 0.012 1.08 [FIGURE 1] a) the date and universal time of flare maximum, b) the duration before and after the maximum (t_b and t_a, respectively), as well as the total duration of the flare, c) the value of the ratio (I_f-I_0)/I_0 corresponding to flare maximum, where I_0 is 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)=2.5 log(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 curve of the observed flare in the b colour is shown in Fig. 1. G. KAREKLIDIS, F. MAHMOUD, 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