COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2630 Konkoly Observatory Budapest 23 November 1984 HU ISSN 0374 - 0676 UV CETI: SYNCHRONOUS UBV FLARE OBSERVATIONS The results of the flare observations on UV Ceti carried out at the Maidanak station of Tashkent Astronomical Institute are presented. During the 94.25 hours of effective time of observations (1-14 August 1978, 20-29 September 1979, 24-27 September 1982) 14 flares were detected on UV Ceti (Melikian et al. 1979, Kiljachkov et al. 1979a, Kiljachkov et al. 1979b, Melikian et al. 1981, Melikian et al. 1983). Some of them have been observed simultaneously in three colours U, B and V with the 60-cm and 48-cm telescopes. The description of the method and some characteristics of these observations can be found in Melikian's et al. (1979, 1981) papers. The present paper includes the data of all observed flares (see Table I). In the columns of Table I the following data on flares are presented, respectively: 1. The serial number of the flare up in the given year; 2. The date of flare in UT; 3. Time of maximum in UT; 4. The rise time - t_1 in seconds; 5. The decay time t_2 in seconds; 6.-8. Amplitudes DeltaU, DeltaB and DeltaV 9.-10. The ( U-B )_+ and ( B-V )_+ colours of the flare at the maximum, respectively. The data presented in Table I show, that the average frequency of flares is about 1.1 flares hour^-1 during these observations and that the ( U-B )_+ and ( B-V )_+ colours of the flares are very blue. Such blue colours were detected for the flares in stellar aggregates, associations and young stellar clusters (Mirzoyan at al. 1981, 1983). Using the two component flare model, Kunkel (1967) showed, that after the maximum the flares have a slope Delta( U-B ) / Delta( B-V ) ~~ 0.3 Table I The data of observed flares on UV Ceti -------------------------------------------------------------------------- No date of time of rise decay flare max. time time DeltaU DeltaB DeltaV (U-B)_+ (B-V)_+ (UT) t_1 t_2 -------------------------------------------------------------------------- 1 02.08.1978 22h12m42s 12s 8s 1.53m 0.39m 0.10m -0.75m +0.30m 2 " 13 00 4 12 1.42 0.36 0.06 -0.70 - 3 04.08.1978 21 39 26 6 14 2.63 0.95 0.39 -0.77 +0.57 4 " 43 37 22 88 2.70 - 0.20 - - 5 " 46 58 8 16 1.80 - - - - 6 " 22 41 12 4 22 1.90 - - - - 7 " 43 18 8 42 2.14 0.58 0.17 -0.96 +0.30 8 05.08.1978 23 13 46 6 14 3.50 - 0.40 - - 9 07.08.1978 21 22 30 8 52 - 1.50 0.25 - +0.80 10 " 22 26 08 18 160 - 1.40 - - - 11 " 29 10 20 30 - 1.10 - - - 12 09.08.1978 20 55 10 40 >70 3.72 1.93 0.56 -0.56 -0.31 13 " 58 32 102 3700 6.50 >4.30 3.20 - - 14 10.08.1978 22 14 54 78 440 - 2.60 0.70 - -0.75 15 12.08.1978 23 14 00 10 280 3.55 2.02 0.44 -0.28 -0.73 16 13.08.1978 21 29 15 30 150 2.92 1.63 0.37 -0.10 -0.40 1 20.09.1979 21 01 15 9 345 >3.49 2.20 0.94 - +0.16 2 23.09.1979 19 00 32 14 105 1.51 0.37 0.24 -0.78 +1.31 3 " 23 53 14 793 4.03 1.94 0.88 -0.87 +0.35 4a " 20 05 32 7 16 2.17 0.18 - - - 4b " 05 58 9 9 2.11 0.20 - - - 4c " 07 15 7 17 2.86 0.57 - -1.79 - 4d " 08 53 2 9 2.33 0.37 - -1.77 - 4e " 09 49 28 28 1.73 0.48 0.22 -0.72 +0.80 5 " 13 32 7 150 2.44 0.72 0.36 -1.00 +0.92 6 " 19 05 9 32 1.63 0.23 0.29 -1.52 +2.13 7 " 32 48 16 44 2.72 - - - - 8 " 37 00 5 37 2.00 - - - - 9 " 41 30 16 67 1.79 0.26 0.16 -1.59 +1.28 10 " 21 08 28 5 21 1.69 0.21 0.13 -1.74 +1.33 11 " 57 45 7 182 2.36 0.55 0.29 -1.29 +1.03 12 " 22 09 30 14 69 2.57 0.58 0.24 -1.40 +0.72 13 24.09.1979 19 11 40 2 12 2.27 - - - - 14 " 15 47 2 12 1.49 - - - - 15a " 20 48 37 2 9 1.97 - - - - 15b " 49 32 2 9 2.60 - - - - 16 25.09.1979 18 35 57 14 663 4.12 1.15 - -2.2 - 17a " 51 12 18 39 1.84 - - - - 17b " 52 49 7 23 2.34 - - - - 18 " 19 25 37 14 21 1.53 0.16 0.06 - - 19 " 51 14 2 44 - 0.32 0.18 - +1.15 20 " 21 03 21 7 55 2.02 0.28 0.15 -1.79 +1.13 21 " 58 58 5 9 2.62 - - - - 22 " 22 08 53 7 208 3.06 0.77 0.24 -1.57 +0.31 23 " 20 18 2 12 2.66 - 0.27 - - 24 " 23 04 37 23 160 1.60 0.22 0.16 - - 25 " 36 39 7 60 >0.97 0.36 0.19 - +1.04 26 26.09.1979 20 11 15 9 81 1.97 0.32 0.22 -1.56 +1.38 27 " 21 13 00 5 65 3.27 0.93 0.33 -1.49 +0.58 28 " 22 55 21 14 30 1.41 0.20 0.13 -1.42 +1.38 29 27.09.1979 18 45 10 16 225 >1.30 0.79 - - - 30 " 19 05 46 12 60 1.48 0.25 0.07 -1.23 +0.43 Table I (cont.) ------------------------------------------------------------------------ No date of time of rise decay flare max. time time DeltaU DeltaB DeltaV (U-B)_+ (B-V)_+ (UT) t_1 t_2 ------------------------------------------------------------------------ 31a 27.09.1979 19h26m46s 9s 83s 4.35m 1.86m 0.72m -1.29m +0.14 31b " 28 42 39 463 2.46 0.50 0.18 -1.50 +0.58 32 " 20 48 42 2 23 2.43 0.51 0.17 -1.47 +0.48 33 " 21 22 56 2 16 1.98 0.20 0.22 -2.14 +1.95 34 " 22 00 55 14 23 1.16 0.20 0.16 -1.06 +1.61 35 " 22 00 9 37 1.40 0.20 - -1.40 - 36 " 23 30 32 2 14 1.85 0.23 - -1.79 - 37 " 33 16 7 18 1.63 0.32 - -1.13 - 38 28.09.1979 18 10 00 - 400 - 0.45 - - - 39 " 23 15 2 73 - 0.35 - - - 40 " 59 56 7 37 2.54 0.66 0.23 -1.23 +0.62 41 " 19 06 42 2 2 1.79 - 0.22 - - 42 " 15 56 18 26 2.03 0.52 0.18 -1.00 +0.53 43 " 20 13 30 7 44 2.88 0.83 0.28 -1.22 +0.35 44 " 21 28 32 7 60 1.70 0.16 0.13 -2.04 +1.63 45a " 47 33 5 5 2.32 - - - - 45b " 47 40 2 20 3.05 - - - - 46 " 56 32 7 60 2.06 0.23 - -2.04 - 47 " 59 42 5 91 3.33 0.96 0.37 -1.51 +0.50 48 " 22 02 39 7 192 4.81 1.96 0.83 -1.64 +0.24 49a " 27 05 16 >30 1.89 0.44 0.39 -1.00 +1.70 49b " 29 10 108 800 2.23 0.58 0.54 -1.10 +1.70 50 " 23 34 35 16 127 - 0.60 - - - 51 29.09.1979 20 05 00 7 25 - 0.26 - - - 1 24.09.1982 21 54 23 7 23 1.82 - - - - 2 " 22 38 02 5 72 2.54 - 0.28 - - 3 " 43 18 5 23 1.82 - - - - 4 " 55 11 2 30 2.02 - - - - 5 " 23 34 30 30 120 2.10 0.58 0.32 -0.90 +1.05 6 " 38 18 2 23 1.45 - - - - 7 " 21 20 52 2 23 4.47 - - - - 8a " 39 11 7 46 2.56 0.64 0.24 -1.30 +0.60 8b " 40 07 2 60 2.63 0.60 0.19 -1.50 +0.40 9 " 22 09 11 5 23 1.53 0.24 0.15 -1.40 +1.30 10 " 33 11 14 30 1.67 - - - - 11 " 23 11 16 9 30 1.72 0.49 0 -0.70 - 12 26.09.1982 21 02 11 2 30 2.05 - - - - 13 " 06 07 5 120 1.10 - - - - 14 " 43 11 5 55 2.22 0.64 0.24 -0.90 +0.60 15 " 22 34 11 5 23 2.08 - - - - 16 " 40 18 32 72 1.96 0.32 - -1.50 - 17 " 23 07 16 5 23 - 0.20 - - - 18 27.09.1982 20 15 16 14 120 1.70 0.33 0.05 -1.20 - 19 " 21 49 5 200 1.51 0.36 0.26 -0.80 +1.40 20 " 55 41 2 23 1.66 - - - - 21 " 21 05 44 2 28 1.45 0.13 0.08 -2.10 - 22 " 22 11 26 2 23 1.89 - - - - 23 " 16 44 2 67 2.29 - - - - 24 " 59 11 7 46 2.90 1.16 - -0.70 - 25 " 23 04 00 5 120 2.93 1.15 0.46 -0.08 +0.50 26 " 10 16 5 46 4.36 - - - - 27 " 21 16 2 23 2.10 0.66 0.34 -0.70 +1.00 [FIGURE 1] [FIGURE 2] [FIGURE 3] [FIGURE 4] of the two-colour diagram ( U-B, B-V). From the other hand Cristaldi and Longhitano (1979) pointed out that during the flares the flare colours were constant. On the basis of results of our first synchronous UBV flare observations on UV Ceti, it was shown that there was no certain direction for flare trajectories on the two-colour diagram (Kiljachkov et al. 1979b). In the present paper in the Figures 1-4 the trajectories on the two-colour diagram for 8 flares on UV Ceti are presented. These figures show, that a) on the two colour diagram the flare trajectories have various directions, and b) the flare colours during the flare are not constant. The same results were obtained for flare stars in the stellar aggregates (Mirzoyan et al. 1981, 1983) on the basis of synchronous UBV flare observations. N.D. MELIKIAN Armenian SSR, USSR, Byurakan Astrophysical Observatory References: S. Cristaldi, M. Longhitano, 1979, Astron, Astrophys., Suppl. Ser., 38, 175. [BIBCODE 1979A&AS...38..175C ] N. N. Kiljachkov, N. D. Melikian, L. V. Mirzoyan, V. S. Shevchenko, 1979 a, Astrofizika, 15, 423. [BIBCODE 1979Afz....15..423K ] N. N. Kiljachkov, N. D. Melikian, L. V. Mirzoyan, V. S. Shevchenko, 1979 b, Astrofizika, 15, 605. [BIBCODE 1979Afz....15..605K ] W. E. Kunkel, 1967, An Optical study of Stellar Flares. Austin. N. D. Melikian, N. N. Kiljachkov, O. I. Stalbovsky, G. P. Sigal, V. E. Slutzky, A.I. Jeleznjakova 1979. IBVS, No. 1546. N. D. Melikian, I. Jankovics, N. N. Kiljachkov, V. S. Shevchenko, O.I. Stalbovsky, 1981, IBVS, No. 2038. N. D. Melikian, N. N. Kiljachkov, V. N. Igolkin, 1983, Astrofizika, 19, 835. [BIBCODE 1983Afz....19..835M ] L.V. Mirzoyan, H.S. Chavushian, N. D. Melikian, R. Sh. Natsvlishvili, G.B. Ohanian, V.V. Hambarian, A. T. Garibjanian, 1981, Astrofizika 17, 197. [BIBCODE 1981Afz....17..197M ] L.V. Mirzoyan, H.S. Chavushian, N. D. Melikian, R. Sh. Natsvlishvili, V.V. Hambarian, G. A. Brutian, 1983, Astrofizika, 19, 725. [BIBCODE 1983Afz....19..725M ]