COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2621 Konkoly Observatory Budapest 6 November 1984 HU ISSN 0374 - 0676 FLARE STARS IN ORION The search for flare stars in stellar aggregates, associations and young stellar clusters has been going on at the Byurakan Astrophysical Observatory for about 20 years (Chavushian et al., 1979; Melikian, 1981; Mirzoyan, 1964; Natsvlishvili and Melikian, 1980). Among other aggregates, observations of the Orion nebula region have been made, as well. During 102 hours of effective observational time 28 flares have been detected, 19 of those being detected on new flare stars. Some results concerning these observations, especially the results of the synchronous UBV observations have already been published (Mirzoyan et al., 1981, 1983). In general these observations were carried out with the 40" and 21" Schmidt telescopes of the Byurakan Observatory. The method of observations was the common one of multiple and equal exposures of 5 or 10 minutes. In the present paper the data about the observed flares (see Table I) and the identification charts for the 19 new flare stars (see Figure 1) are given. The following data are presented in the respective columns of Table I: 1. The Byurakan number of the flare star (N); 2. Parenago's number (NP); 3. Haro's number (NH); 4.-5. Coordinates for 1900.0 6. The magnitude of the flare star at minimum (m_u); 7. The amplitude of the flare (Delta U or Delta pg); 8. The telescope which was used for the detection of the flare; 9. The date of the occurrence of the flare. In seven cases the rise of the flare lasted more than 10 minutes. These are "slow" flares according to the classification of Haro (1964). In Table II the numbers and the rise times for these flares are presented. The light curve of the outburst on the star No. 20 had a very interesting shape. In Table I one can see that the amplitude of this flare in the U band Table I. Flare stars in Orion ------------------------------------------------------------------------------- N NP NH alpha_1900.0 delta_1900.0 m_u Deltau tel. date ------------------------------------------------------------------------------- B1 5h30.3m -5d51' 16m5pg 1.2pg 40" 25.10.1962 B2 1215 136 28.8 -4 17 17.5pg 2.4pg 40" 14.01.1964 B3 254 38.0 -5 51 16.5pg 1.3pg 40" 12.02.1964 B4 30.0 -5 49 16.5pg 1.5pg 40" 03.10.1970 B5 29.6 -5 05 18.0 4.5 40" 07.03.1975 B6 236 31.7 -5 41 18.7 >3.5 40" 08.03.1975 B7 38.7 -4 58 20.0 6.5 40" 08.03.1975 B8 26.8 -7 15 18.7 5.2 40" 10.11.1977 B9 207 29.3 -6 00 17.6 2.1 40" 07.11.1977 B10 20.4 -4 39 17.6 4.1 40" 19.10.1979 B11 2176 28.4 -4 23 15.5 1.7 40" 18.12.1979 B12 22.5 -7 06 18.4 5.0 40" 18.12.1979 B13 27.1 -5 43 18.0v 1.8v 28" 21.12.1979 B14 129 27.0 -4 31 18.2 5.7 40" 18.12.1979 B15 187 27.3 -7 08 18.0 4.6 40" 25.11.1978 B16 37.1 -5 14 21 7.0 40" 29.11.1978 B17 1167 194 28.5 -5 37 17.8 2.1 40" 29.01.1979 B18 31.7 -3 48 19.0 3.5 40" 29.01.1979 B19 30.2 -4 30 17.7 3.5 40" 17.10.1980 B20 2572 32.8 -5 16 17.4 5.4 40" 22.10.1980 B21 1588 29.7 -5 38 18.0 3.7 40" 22.10.1980 B22 2618 33.0 -6 28 15.0 1.0 40" 22.10.1980 B23 1463 31 29.5 -5 00 17.4 4.2 40" 04.11.1980 B24 847 27.2 -5 07 17.4 4.5 40" 04.11.1980 B25 1471 29.5 -5 37 17.8 2.5 40" 04.11.1980 B26 28.1 -4 14 15.8 1.2 40" 01.12.1980 B27 2368 231 31.3 -5 16 15.5 1.4 40" 07.12.1980 B28 2381 31.5 -6 06 15.1 4.3 40" 03.11.1980 Table II. Slow flares in Orion N B6 B9 B12 B14 B15 B22 B24 Rise time (min.) 30 20 15 10 10 10 10 [FIGURE 1] is equal to 5.4m. The brightness during this flare increased within few minutes and remained at the maximum for more than 3 hours. N.D. MELIKIAN Byurakan Astrophysical Observatory Byurakan, Armenia, U.S.S.R. References: Chavushian, H.S., Melikian, N.S., Mirzoyan, L.V., and Jankovics, I., 1979: Inf. Bull. Var. Stars, No. 1628. Haro, C., 1964: In: The Galaxy and the Magellanic Clouds; IAU-URSI Symp. No. 20, Australian Acad. Sci., Canberra, p. 30. [BIBCODE 1964IAUS...20...30H ] Melikian, N.D., 1981: Inf. Bull. Var. Stars, No. 2018. Mirzoyan, L.V., 1964: Astronomicheskij Tsirk., No. 294. Mirzoyan, L.V., Chavushian, H.S., Melikian, N.D., Natsvlishvili, R.Sh., Hambarian, V.V., and Brutian, G.H., 1983: Astrofizika, 19, 725. [BIBCODE 1983Afz....19..725M ] Mirzoyan, L.V., Chavushian, H.S., Melikian, N.D., Natsvlishvili, R.Sh., Ohanian, G.B., Hambarian, V.V., and Garibjanian, A.T., 1981: Astrofizika, 17, 197. [BIBCODE 1981Afz....17..197M ] Natsvlishvili, R.Sh., and Melikian, N.D., 1980: Inf. Bull. Var. Stars, No. 1726.