COMMISSION 27 OF THE I.A.U. INFORMATION BULLETIN ON VARIABLE STARS Number 1210 Konkoly Observatory Budapest 1976 November 29 PHOTOELECTRIC OBSERVATIONS OF UV CETI The results of photoelectric monitoring of the flare star UV Ceti are herein reported. The star was monitored as part of a collaborative programme for a total of 11h38m spread over 5 nights during December 1975, using the Sampurnanand 104 cm reflector equipped with a refrigerated EMI 6094S photomultiplier. A total of 17 flares were detected. The observed flare light curves (Figs. 1-17), monitoring intervals (Table I) and flare characteristics (Table II) are presented. For energy estimates quiescent state luminosity of the star UV Ceti in B band is taken to be 7.31 x 10^27 ergs sec^-1. The peak of flare No. 8 was lost while taking sky measures and peak of flare No. 15 could not be covered for a very small interval due to instrumental limitations. The author is thankful to Dr. S.D. Sinvhal for suggestions and guidance. Part of this work was carried out with financial assistance under Smithsonian Institution Project No. SFG-0-6425. B. B. SANWAL Uttar Pradesh State Observatory Manora Peak, Naini Tal - 263129 India Reference: Cristaldi, S. and Rodono, M., 1973, Astron. Astrophys. Suppl. 10, 47 [BIBCODE 1973A&AS...10...47C ] Table I Monitoring Intervals (Times rounded off to nearest minute of U.T.) Date Dec. 1975 6 15h22m- 16h25m 16h32m- 17h24m 17h32m- 17h54m 18h11m-18h56m 7 15 11 - 16 37 16 42 - 17 15 17 18 - 17 36 17 49 - 18 25 8 14 03 - 15 41 16 13 - 17 05 17 11 - 18 11 18 14 - 18 27 18 30 - 18 39 9 16 22 - 17 23 17 25 - 17 51 17 53 - 18 26 10 17 44 - 18 73 18 25 - 18 36 18 43 - 18 53 Table II Characteristics of the Flare Events on W Ceti (dM4.5e: V=11.95; B-V=1.76) Date Flare duration sigma/X_s Dec. 1975 (in minutes) I_0+f/I_0 P UT.max. Before After (min) Energy* Total emission** No. max t_b max t_a deltamB F(z) 1 6 15h42m50 1.40 3.40 1.321 0.302 .020 0.300 1.023 0.96 1.31 2 6 15 50.25 0.40 3.50 1.925 0.726 .023 0.625 1.026 1.43 2.74 3 6 16 18.00 0.15 5.40 2.172 0.842 .018 0.565 1.047 1.59 2.48 4 6 16 38.80 0.17 3.17 1.256 0.247 .022 0.233 1.071 0.92 1.02 5 6 16 57.30 0.67 2.67 1.279 0.267 .031 0.370 1.101 0.93 1.62 6 6 17 02.66 0.10 1.33 1.767 0.618 .051 0.303 1.109 1.29 1.33 7 6 17 13.45 0.13 1.58 2.127 0.819 .018 0.171 1.133 1.55 0.75 8 8 - - - - - .016 - - - - 9 8 16 21.00 0.60 4.00 1.296 0.281 .018 0.255 1.059 0.95 1.12 10 8 16 31.30 1.53 7.33 1.529 0.451 .031 0.737 1.072 1.12 3.32 71 8 17 17.03 0.73 15.00 7.408 0.368 .022 1.366 1.160 1.03 5.99 12 9 16 42.66 0.33 5.66 1.468 0.417 .041 0.537 1.096 1.07 2.35 73 9 16 58.83 1.00 4.00 1.195 0.280 .037 0.426 1.127 0.95 1.87 74 9 17 26.63 0.20 8.13 1.372 0.343 .030 0.255 1.197 1.00 1.11 15 9 17 54.41 0.166 4.50 4.777 1.698 .017 2.800 1.293 3.49 12.86 16 10 18 00.83 0.26 6.33 7.365 0.338 .033 0.488 1.304 0.99 2.14 17 10 18 08.00 0.26 5.33 1.170 0.017 .033 0.200 1.370 0.85 0.88 * Energy released at flare maximum 10^29 ergs/s. ** Total emission during the event 10^29 ergs. [FIGURE 1] [FIGURE 2] [FIGURE 3]