COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2038 Konkoly Observatory Budapest 1981 November 5 HU ISSN 0374-0676 SYNCHRONOUS UBV FLARE OBSERVATIONS ON UV CETI The flare observations on UV Ceti have been done at the high altitude Maidanak station of Tashkent Astronomical Institute. In the period from 20th to 29th of September 60 flares were detected on UV Ceti. Some of them were observed simultaneously in three colours. The effective time of these observations was about 42 hours. In fact these observations present the continuation of the ones done in 1978. (1,2). The UBV colours were observed with the 60 cm, 60 cm and 48 cm telescopes, respectively. The measurements have been made by photon counting method. The duration of each measurement was 2.0 second, and the time interval between two measurements was 0.4 second. The precision of synchronization of observations was 0.001 second. The data of observed flares are presented in Table I. The columns of Table I represent respectively: the number of flare up, data (September 1979), the time of maximum in UT, the rise time (t_1) and the decay time (t_2) in seconds, amplitudes DeltaU, DeltaB, DeltaV, and the colours (U-B)_f and (B-V)_f of the flare. The data presented in the Table I show that the average frequency of flares of this observations is about 1.5 flare hour^-1, and that the (U-B)_f and (B-V)_f colours of the flares, and especially the the (U-B)_f colours, are very blue. For illustration the light curves of two flares are presented in Figures 1 and 2. Table I N Date The time of t_1 t_2 DeltaU DeltaB DeltaV (U-B)_f (B-V)_f maximum (UT) (sec) (sec) -------------------------------------------------------------------------------- 1 20 21h01m15s 9.2 345.0s 3.49m 2.20m 0.94m - 0.16m 2 23 19 00 32 13.8 105.2 1.51 0.37 0.24 -0.78 1.31 3 19 23 53 13.8 793.0 4.03 1.94 0.88 -0.87 0.35 4a 20 05 32 6.9 16.1 2.17 0.18 - - - 4b 20 05 58 9.2 9.2 2.11 0.20 - - - 4c 20 07 15 6.9 16.1 2.86 0.57 - -1.79 - 9d 20 08 53 2.3 9.2 2.33 0.37 - -1.77 - 9e 20 09 49 27.6 27.6 1.73 0.48 0.22 -0.72 0.80 5 20 13 32 6.9 149.5 2.44 0.72 0.36 -1.00 0.92 6 20 19 05 9.2 32.2 1.63 0.23 0.29 -1.52 - 7 20 32 48 16.1 43.9 2.72 - - - - 8 20 37 00 4.6 36.8 2.00 - - - - 9 20 41 30 16.1 66.7 1.79 0.26 0.16 -1.59 1.28 10 21 08 28 4.6 20.8 1.69 0.21 0.13 -1.74 1.33 11 21 57 45 6.9 182.3 2.36 0.55 0.29 -1.29 1.03 12 22 09 30 13.8 69.2 2.57 0.58 0.24 -1.40 0.72 13 24 19 11 40 2.3 11.5 2.27 - - - - 14 19 15 47 2.3 11.5 1.49 - - - - 15a 20 48 37 2.3 9.2 1.97 - - - - 15b 20 49 32 2.3 9.2 2.60 - - - - 16 25 18 35 57 13.8 663.0 4.12 1.15 - -2.02 - 17 18 51 12 18.4 39.3 1.84 - - - - 17 18 52 49 6.9 23.1 2.34 - - - - . 18 19 25 37 13.8 20.8 1.53 0.16 0.06 - - 19 19 51 14 2.3 43.8 - 0.32 0.18 - 1.15 20 21 03 21 6.9 55.2 2.02 0.28 0.15 -1.79 1.13 21 21 58 58 4.6 9.2 2.62 - - - - 22 22 08 53 6.9 207.7 3.06 0.77 0.24 -1.57 0.31 23 22 20 18 2.3 11.5 2.66 - 0.27 - - 24 23 04 37 23.0 159.3 1.60 0.22 0.96 - - 25 23 36 39 6.9 60.0 0.97 0.36 0.19 - 1.04 26 26 20 11 15 9.2 80.8 1.97 0.32 0.22 -1.56 1.38 27 21 13 00 4.6 64.6 3.27 0.93 0.33 -1.49 0.58 28 22 55 21 13.8 29.9 1.41 0.20 0.13 -1.42 1.38 29 27 18 45 10 16.1 225.1 1.30 0.79 - - - 30 19 05 46 11.5 59.8 1.48 0.25 0.07 -1.23 0.43 31a 19 26 46 9.2 83.1 4.35 1.86 0.72 -1.29 0.14 31b 19 28 42 39.1 463.1 2.46 0.50 0.18 -1.50 0.58 32 20 48 42 2.3 23.0 2.43 0.51 0.17 -1.47 0.48 33 21 22 56 2.3 16.1 1.98 0.20 0.22 - - 34 22 00 55 13.8 23.0 1.16 0.20 0.16 -1:06 1.61 35 22 22 00 9.2 36.6 1.40 0.20 - -1.40 - 36 23 30 32 2.3 13.8 1.85 0.23 - -1.79 - 37 23 33 16 6.9 18.4 1.63 0.32 - - - 38 28 18 10 00 ? 400.0 - 0.45 - - - 39 18 23 15 2.3 73.2 - 0.35 - - - 40 18 59 56 6.9 36.8 2.54 0.66 0.23 -1.23 0.62 41 19 06 42 2.3 13.8 1.79 - 0.22 - - 42 19 15 56 18.4 25.3 2.03 0.52 0.18 -1.00 0.53 43 20 13 30 6.9 43.8 2.88 0.83 0.28 -1.22 0.35 44 21 28 32 6.9 60.0 1.70 0.16 0.13 - 1.63 45a 21 47 33 4.6 4.6 2.32 45b 21 47 40 2.3 19.5 3.05 46 21 56 32 6.9 60.0 2.06 0.23 - - - 47 21 59 42 4.6 90.4 3.33 0.96 0.37 -1.51 0.50 48 22 02 39 6.9 191.6 4.81 1.96 0.83 -1.64 0.24 49a 22 27 05 16.1 30.0 1.89 0.44 0.39 -1.00 1.70 . 49b 22 29 10 108.1 800.0 2.23 0.58 0.54 -1.10 1.70 50 23 34 35 16.1 126.9 - - 0.60 - - 51 29 20 05 00 6.9 25.3 - 0.26 - - - ----------------------------------------------------------------------------- [FIGURE 1] [FIGURE 2] N.D. MELIKIAN I. JANKOVICS Byurakan Astrophysical Observatory Konkoly Observatory N.N. KILJACHKOV, V.S. SHEVCHENKO and O.I. STALBOVSKY Tashkent Astronomical Institute References: N.D. Melikian, N.N. Kiljachkov, O.I. Stalbovsky, G.P. Sigal, V.E. Slutzky, A.I. Teleznjakova, IBVS No. 1546, 1979. N.N. Kiljachkov, N.D. Melikian, L.V. Mizzoyan, V.S. Shevchenko, Astrofizika, 15, 423, 1979. [BIBCODE 1979Afz....15..423K ]