COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1654 Konkoly Observatory Budapest 1979 August 1 PHOTOELECTRIC OBSERVATIONS OF THE FLARE STAR UV Cet IN 1974,1975 Continuous photoelectric monitoring of the flare star UV Cet has been carried out at the Stephanion Observatory (lambda=-22d49'44" phi=+37d45'15") during the years 1974, 1975 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: V = v_0- 0.018(b-v) + 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 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 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 41 hours of the monitoring time 23 flares were observed 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 (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 Table Ia Monitoring Intervals in 1974 --------------------------------------------------------------------- Date Monitoring Intervals Total Monitoring sigma(U.T.) 1974 (U.T.) Time Sept. --------------------------------------------------------------------- 11 00h02m-00h26m,0029-0057,0100-0131, 0.10(00h40m),0.09 0134-0200. 1h49m (00h39m),0.09(01 15). 15 0014-0045,0048-0117,0210-0227, 1 17 0.08(0018),0.06 (00 54) ,0.08(02 12). 16 0019-0049,0052-0120,0123-0149 1 24 0.09(00 28) ,0.11 (00 59),0.10(01 30). 17-18 2338-0005,0007-0035,0037-0105, 0.07(2347),0.06 0107-0134 150 (0011),0.05(0046) 0.07(01 16). 18-19 2359-0029,0031-0059,0101.-0129, 0.06(0003),0.06 0131-0215 110 (0036),0.06(0106) 0.07(01 34). 19-20 2312-2339,2341-0012,0013-0043 0.11(2314),0.08 0049-0117,0122-0155 2 29 (2347),0.07(0017) Oct. 0.08(0052),0.10(01271, 8-9 2115-2143,2145-2213,2216-2248, 0.07(2116),0.11(2145), 2300-2328,2330-2358,0000-0016, 0.08(2213),0.10(2248), 0020-0028,0038-0105,0108-0136, 0.16(2300),0.16(2330), 0138-0148,0150-0202,0216-0224, 0.13(0010),0.19(0028), 0227-0232,0235-0242,0245-0300. 4 40 0.17(0038),0.14(0105), 0.21(0036),0.25(0216), 0.20(02 45). 9-10 2114-2141,2143-2211,2213-2249, 0.08(2117),0.08(2146), 2258-2328,2330-2400,0003-0020, 0.06(2215),0.09(2246), 0021-0026,0037-0056,0100-0109, 0.11(2328),0.10(00 08), 0111-0138,0140-0202,0216-0226, 0.14(0022),0.13(01 13), 0228-0234,0238-0252,0254-0259. 4 45 0.15(0155),0.19(0216), 0.18(0240). 11-12 2303-2331,2333-2400,0000-0002, 0.12(2303),0.97(2335), 0005-0041,0052-0121,0125-0144, 0.09,(0007),0.12(0052), 0146-0154,0156-0219,0224-0232, 0.11(0125),0.14(0154), 0234-0253. 3 19 0.29(0226). 16 2048-2112,2115-2130,2132-2141. 0 48 0.10(2048),0.13(2117). 17-18 2152-2217,0002-0025,0027-0049, 0.08(2152),0.07(2217), 0053-0118,0131-0156,0159-0206, 0.08(0003),0.08(0029), 0208-0223. 2 22 0.09(0054),0.11(0132), 0.16(0200),0.16(0221). 18-19 2248-2315,2317-2343,2345-2400, 0.10(2252),0.08(2321), 0000-0012,0027-0052,0055-0124, 0.08(2347),0.08(0010), 0127-0146. 2 33 0.11(0027),0.12(0056), 0.11(01 37). 21-22 2103-2131,2133-2159,2201-2234, 0.08(2103),0.06(2133), 2245-2313,2316-2352,2354-0008. 2 45 0.08(2203),0.07(2232), 0.06(23 11) ,0.09(23 37), 0.09(2358). -------------------------------------------------------------------------- Total 31h11m -------------------------------------------------------------------------- Table 1b Monitoring Intervals in 1975 -------------------------------------------------------------------------- Date Monitoring Intervals Total Monitoring sigma(U.T.) 1975 (U.T.) Time January -------------------------------------------------------------------------- 4 18h08m-18h36m,1840-1845,1847-1908 0.09(18h09m),0.07 1911-1936,1946-1951. 1h24 (1841),0.07(1915). 5 1731-1758,1801-1831,1835-1854, 0.07(1753),0.06(1820), 1910-1941,1944-1955,1957-2006, 0.06(1848),0.09(1927), 2009-2015,2018-2027,2030-2037, 0.08(2000),0.08(2022), 2053-2059,2103-2106. 2 38 0.15(2055). 6 1742-1814,1816-1847,1849-1922, 0.08(1751),0.08(1805), 1932-1949,1952-2005,2008-2018, 0.08(1840),0.07(1905), 2020-2032,2038-2054. 2 44 0.19(1956),0.11(2028), 0.11(2048). 7 1721-1750,1753-1827,1830-1907 0.07(1723),0.06(1750); 1919-1945,1949-2013,2015-2048 3 03 0.07(1826),0.07(1906), 0.11(1944),0.12(0215). -------------------------------------------------------------------------- Total 9h49m -------------------------------------------------------------------------- T A B L E II Characteristics of the Flares Observed ------------------------------------------------------------------------------------------------ flare Date U.T. t_b t_a Duration 1_f-I_0/I_0 P Delta m sigma Air No. max. min min min max. min mag. mag. mass 1974 ------------------------------------------------------------------------------------------------ September 1 11 01h18.9m 0.7 10.1 10.8 8.01 9.37 2.39 0.09 1.80 2 11 01 44.6 9.6 14.0 23.6 0.93 7.46 0.71 0.09 1.86 3 17 23 48.9 0.2 0.3 0.5 0.68 0.08 0.56 0.07 1.80 October 4 8 21 19.95 0.57 3.36 3.93 1.07 0.65 0.79 0.07 2.02 5 8 23 14.6 0.2 0.5 0.7 0.61 0.12 0.52 0.16 1.78 6 9 22 34.65 0.21 2.19 2.40 0.84 0.63 0.66 0.08 1.79 7 10 00 22.3 0.8 2.7 3.5 0.66 0.60 0.55 0.14 1.97 8 10 01 55.35 0.14 3.10 3.24 2.29 1.38 1.29 0.15 2.96 9 18 23 47.8 0.15 1.6 1.75 1.80 0.41 1.12 0.08 1.96 10 19 00 27.6 0.5 1.5 2.0 0.75 0.48 0.61 0.11 2.24 11 19 01 37.7 0.3 9.2 9.5 5.41 6.07 2.02 0.10 3.38 12 21 23 37.65 3.4 10.3 13.7 0.86 3.37 0.67 0.09 1.97 13 21 23 58.0 0.1 3.4 3.5 1.84 0.52 1.13 0.09 2.08 1975 January 14 4 18 18.5 8.5 15.7 24.2 4.50 9.37 1.85 0.09 1.88 15 5 18 03.65 1.65 2.35 4.1 0.29 0.45 0.27 0.07 1.85 16 5 18 50.4 0.7 0.7 1.4 0.29 0.11 0.27 0.06 2.05 17 5 19 30.0 0.1 15.0 15.1 0.65 (2.25) 0.54 0.09 2.37 18 6 17 53.1 0.1 0.2 0.3 0.54 0.06 0.47 0.08 1.83 19 6 18 6.5 0.1 2.5 2.6 1.52 0.27 1.00 0.08 1.87 20 6 20 21.35 0.1 1.5 1.6 0.65 0.24 0.54 0.11 3.33 21 6 20 29.05 0.1 1.7 1.8 1.09 0.28 0.80 0.11 3.56 22 7 18 42.0 0.2 0.9 1.1 0.65 0.24 0.54 0.08 2.05 23 7 20 21.2 0.1 21.3 21.4 28.34 54.34 3.67 0.12 3.44 ------------------------------------------------------------------------------------------------ total duration, including pre-flare, 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)=2.5log(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, D. STAVRIDIS, A.C. TSIOUMIS Department of Geodetic Astronomy University of Thessaloniki Reference: Andrews, A.D., Chugainov, P.F., Gershberg, R.I., and Oskanian, V.S.: I.B.V.S. No. 326, 1969 [FIGURE 1] [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]