COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1612 Konkoly Observatory Budapest 1979 May 28 SPIKE FLARES OF UV Ceti During 2-9 December 1975 the flare star UV Ceti [R.A. = 01h36m24s, declination = -18d13' (1950), visual magnitude 12,9 at minimum, spectral type dM5,5e] was monitored at Boyden Observatory with the 41 cm Nishimura reflector. A Johnson B filter and an uncooled EMI 6256 A photomultiplier tube were used in the observations. The two flares of (I_0+f - I_0)/I_0 equal to 14,20 and 3,09 were visually confirmed on the night of 2/3 December in the 15cm finder. Of the 38 other flares recorded during this period 36 were spike flares, either single flares or in the form of a spike complex. Their (I_0+f - I_0)/I_0 values were between 1,00 and 2,17 with durations generally between 3 and 12 seconds. The data is presented in the table, following the proposals to flare star observers (1). Examples of light curves representing a selection of the flares are shown in Figures 1-16. On past occasions we have reported similar spike flares from UV Ceti (references 2-5), using the terminology suggested by Moffett (6). Our data reduction has been greatly facilitated by the kindness of Prof. F.D.I. Hodgson, Director of the Institute of Groundwater Studies at the University, in making available his institutes' Hewlett Packard Model 9825 microcomputer and digitizer. A.H. JARRETT and J. VAN ROOYEN Boyden Observatory Astronomy Department University of The Orange Free State Bloemfontein Republic of South Africa DATE MONITORING TIME FLARE MAXIMUM (I_0+f - I_0)/I_0 sigma(mag) m_lim - m_0 1975 U.T. U.T. 2.5log((I_0+f - I_0)/I_0) =-2.5log(|sigma|/I_0) =sigma(mag)-1.19 --------------------------------------------------------------------------------------------------------------------------------- * 2 December 8h05m29s - 18h27m06s 19h37m17s 1,14 0,15 2,10 0,91 183124 - 185312 * 185712 - 190506 195613 1,18 0,18 1,90 0,71 * 190754 - 220000 200042 1,22 0,21 1,90 0,71 * 200112 1,14 0,14 1,90 0,71 * 203916 1,29 0,27 2,13 0,95 x 212030 14,20 2,88 2,04 0,85 x 214507 3,09 1,23 1,98 0,79 -------------------------------------------------------------------------------------------------------------------------------- 3 December 180118 - 184528 182925 1,13 0,13 1,98 0,79 184932 - 190100 ** 190412 - 220015 192552 1,23 0,23 2,03 0,84 192855 1,37 0,34 2,03 0,84 * 195005 1,57 0,49 1,87 0,68 * 203942 1,39 0,36 2,03 0,84 * 204443 1,63 0,53 2,03 0,84 * 204943 1,42 0,38 2,03 0,84 ** 205618 1,49 0,43 2,03 0,84 ** 211645 1,07 0.07 2,03 0,84 * 213158 1,48 0,43 1,93 ' 0,74 * 213544 1,55 0,48 1,93 0,74 ** 213841 1,03 0,03 1,93 0,74 * 214202 1.29 0.28 1.93 0.74 -------------------------------------------------------------------------------------------------------------------------------- x Visually Confirmed * Spike ** Spike Complex DATE MONITORING TIME FLARE MAXIMUM sigma(mag) m_lim -m_0 1975 U.T. U.T. (I_0+f - I_0)/I_0 2.5log((I_0+f - I_0)/I_0) =-2.5log(|sigma|/I_0) =sigma(mag)-1.19 -------------------------------------------------------------------------------------------------------------------------------- 7 December 18h17m15s - 18h45m04s 18h56m03s 1,38 0,35 1,78 0,59 184902 - 183601 ** 183906 - 22 01 14 195852 1,38 0,35 1,78 0,59 201758 1,56 0,48 1,81 0,62 ** 202226 1,26 0,25 1,81 0,62 * 203345 1,42 0,38 1,81 0,62 * 210246 1,28 0,27 1,68 0,49 * 210632 1,84 0,66 1,68 0,49 * 211246 2,17 0,84 1,68 0,49 ** 212245 2,04 0,78 1,68 0,49 ** 212255 1,79 0,63 1,68 0,49 * 212338 1,53 0,46 1,68 0,49 * 212418 1,28 0,27 1,68 0,49 * 214530 1,82 0,65 1,68 0,49 * 214920 1,45 0,40 1,68 0,49 -------------------------------------------------------------------------------------------------------------------------- 8 December 182426 - 183418 205516 1,13 0,13 2,00 0,81 183800 - 184118 * 184506 - 220018 210108 1,18 0,18 1,81 0,62 * 210238 1,00 0,00 1,81 0,62 * 213912 1,44 0,40 1,81 0,62 * 214809 1,50 0,44 1,81 0,62 * 215327 1,39 0,36 1,81 0,62 -------------------------------------------------------------------------------------------------------------------------- 9 December 180414 - 183614 NO FLARES 184200 - 190736 RECORDED 191218 - 230010 -------------------------------------------------------------------------------------------------------------------------- x Visually Confirmed * Spike ** Spike Complex [FIGURE 1] [FIGURE 2] [FIGURE 3] References: 1) Andrews, A.D., Chugainov, P.F., Gershberg, R.E. and Oskanian, V.S., 1969, I.B.V.S. No. 326 2) Jarrett, A.H. and Gibson, J.B., 1975, I.B.V.S. No. 979 3) Jarrett, A.H. and Gibson, J.B., 1975, I.B.V.S. No. 1017 4) Jarrett, A.H. and Gibson, J.B., 1976, I.B.V.S. No. 1105 5) Jarrett, A.H. and J. van Rooyen, 1979, I.B.V.S. No. 1585 6) Moffett, T.J., 1974, Sky and Telescope, 48, 94 [BIBCODE 1974S&T....48...94M ]