COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1002 Konkoly Observatory Budapest 1975 May 22 FLARE STARS IN THE REGION OF NGC 7000. III. During the year 1974 we have continued our observations in the region of Cygnus. The telescopes, the methods of observation and the examination of plates were the same as given in previous papers (1), (2). The observational data are summarized in Table 1. Table 1 ---------------------------------------------- Exp.time Telescope Number Number T_eff (min) of plates of exp. ---------------------------------------------- 40" 94 543 90h30m 10 21" 110 610 101 40 40" 56 336 28 00 5 21" 30 177 14 45 ----------------------------------------------- To the total effective observational time given in Table 1 2h38m should be added which correspond to four other multiple exposure plates (21") not included in this Table, because their exposure times differ from 5 and 10 minutes. Some of the plates form pairs obtained by both telescopes simultaneously (t_eff=35h32m). Our results are listed in Table 2 which contains the following data: Byurakan (B) or Tonantzintla (T) serial number, coordinates for 1950.0, brightness (pg or U ) at minimum light, amplitude of flares (pg or U), date of flare-up, telescope used, length of each exposure on the multiple exposure plate on which the flare-up was found and the observer. Table 2 --------------------------------------------------------------------------- RA. D. m_min m Date of Exp. Design. 1950.0 pg/U pg/U flare-up time Observer Telescope (min) --------------------------------------------------------------------------- B17 20h55.6m +44d32' 17.3U 1.0U 25.07.1973 40" 10 Tsvetkov B18 53.7 43 23 20.5U 3.7U 2.08.1973 40 10 " B19 41.0 41 11 16.2U 1.5U 19.08.1973 40 10 " B17 55.6 44 32 17.3U 2.2U 27.08.1973 40 10 " " " " 16.2pg 1.4pg " 21 10 Erastova B20 21 01.3 44 22 16.9U 1.6U 28.08.1973 40 10 Tsvetkov B17 20 55.6 44 32 17.3U 0.7U 31.08.1973 40 10 " B19 41.0 41 11 16.2U 1.3U 4.09.1973 40 10 Erastova B21 21 01.6 40 59 20.5pg 4.3pg 22.05.1974 21 5 " B22 20 50.6 42 48 19.5U 4.5U 17.06.1974 40 10 " B19 41.0 41 11 16.2U 0.9U 18.06.1974 40 10 " B23 21 02.3 43 24 21.5U 5.6U 20.06.1974 40 10 " B24 20 55.5 40 53 19.7U 3.5U 24.06.1974 40 10 Tsvetkov B17 55.6 44 32 17.3U 2.5U 26.06.1974 40 10 " T1 21 00.7 42 08 18.0U 0.7U 27.06.1974 40 10 " B19 20 41.0 41 11 16.2U 1.0U 28.06.1974 40 10 " " " " 15.3pg 0.4pg " 21 10 Erastova B25 50.7 44 25 20.0U 3.5U 11.07.1974 40 10 Tsvetkov B26 51.3 42 26 21.5U 6.5U 13.07.1974 40 10 " " " " 20.5pg 5.1pg " 21 10 Erastova B27 41.7 43 08 16.3U 2.4U 13.07.1974 40 10 Tsvetkov " " " 15.2pg 0.8pg " 21 10 Erastova B28 32.0 44 13 17.0pg 3.2pg 15.07.1974 21 10 " B29 57.1 42 41 18.1U 1.9U 21.07.1974 40 5 Tsvetkov B30 53.9 40 45 19.5U 3.2U 22.07.1974 40 10 " B17 55.6 44 32 17.3U 2.3U 23.07.1974 40 10 " B31 51.0 43 05 19.0U 3.6U 23.07.1974 40 10 " B32 39.6 41 38 18.8pg 3.6pg 25.07.1974 21 10 Erastova B33 51.1 41 45 18.9U 3.5U 25.07.1974 40 10 Tsvetkov " " " 17.9pg 2.2pg " 21 10 Erastova B34 42.3 42 13 18.0U 1.5U 26.07.1974 40 5 Tsvetkov ---------------------------------------------------------------------------- Table 2 (continued) ------------------------------------------------------------------------- Design RA. D. m_min m Date of Exp. 1950. pg/U pg/U flare-up time Observer Telescope (min) ------------------------------------------------------------------------- B35 20h41.4m +40d07' 20.2pg 3.6pg 12.08.1974 21" 10 Erastova B2 21 00.0 42 26 20.0U 3.8U 12.08.1974 40 5 Tsvetkov B17 20 55.6 44 32 17.3U 2.3U 18.08.1974 40 5 " " " " no registered " 21 10 Erastova B19 41.0 41 11 16.2U 1.1U 19.08.1974 40 10 Tsvetkov B17 55.6 44 32 17.3U 0.6U 8.09.1974 40 10 " B36 48.7 43 15 16.6pg 0.8pg 10.10.1974 21 10 " B17 55.6 44 32 17.3U 1.6U 16.10.1974 40 10 " " " " 16.2pg 0.4pg " 21 10 Tsvetkov* B37 54.5 42 49 18.0U 1.4U 18.10.1974 40 10 Tsvetkov B17 55.6 44 32 17.3U 0.5U 18.10.1974 90 10 " B38 41.4 44 08 19.0U 1.8U 18.10.1974 40 10 " B39 47.2 42 10 20.7U 4.6U 18.10.1974 90 10 " " " " 19.7pg 3.8pg " 21 10 Erastova B40 40.3 44 08 18.5pg 1.0pg 6.11.1974 21 20 " B3 53.9 44 09 19.5U 3.6U 7.11.1979 40 10 " ----------------------------------------------------------------------- We found the flare of B28 on a plate the centre of which was displaced for about 2deg to the West from our usual centre. A few other plates which have displaced centre were taken with the 21" telescope during this observational season as well. Thus 22 new flare stars have been found in 1979 during 201h40m total effective time of observations. Among them the stars B17 and B19 have shown 6 and 3 flare-ups, respectively during the 1974 season. Some flares given in the first part of Table 2 have been discovered after the re-examination of plates of earlier observational periods. It is very interesting to note that B17 and B19 had rather high flare activity. Together with the 23 flare stars from previous lists (1), (2), (3) and L. Rosino's private communication the total number of observed flare stars in the region studied reaches 51. According to Ambartsumian's formulae (4) the total number of flare stars in this region should be greater than 374. This estimate is somewhat higher than the previous one, obtained in the second article of this series (2). It is necessary to stress once more that no conspicuous flare events have happened with stars known to have Halpha line in emission (5), (6), (7). The authors thank Acad. V.A. Ambartsumian and Prof. L.V. Mirzoyan for their constant interest to this work and helpful advices. M.K. TSVETKOV L.K. ERASTOVA K.P. TSVETKOVA Byurakan Astrophysical Byurakan Byurakan Observatory Astrophysical Astrophysical Department of Astronomy Observatory Observatory Bulgarian Academy of Sciences References: 1 L.K. Erastova, M.K. Tsvetkov, IBVS No. 909, 1974. 2 M.K. Tsvetkov, H.S. Chavushian, K.P. Tsvetkova, IBVS No. 938, 1974. 3 G. Haro, E. Chavira, Bol.Inst.Tonantzintla, 1, 17, 1973. [BIBCODE 1973BITon...1...17H ] 4 V.A. Ambartsumian, L.V. Mirzoyan et al, Astrofizika, 6, 7, 1970. [BIBCODE 1970Afz.....6....7A ] 5 G. Herbig, ApJ. 128, 259, 1958. [BIBCODE 1958ApJ...128..259H ] 6 G. Welin, Astron.Astrophys. Suppl., 9, 183, 1973. [BIBCODE 1973A&AS....9..183W ] 7 M.K. Tsvetkov (in press).