COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS NUMBER 788 Konkoly Observatory Budapest 1973 May 2 NEW FLARE STARS IN THE PLEIADES REGION (1972 - 1973) During the months of October, November and December, 1972, and January and February, 1973, we obtained 180 ultraviolet multiple exposure plates centered in Alcyone. The number of different exposures were 1,054 and the total time of effective observation 225h10m. In this photographic material we detected 124 outbursts in different stars. Table 1 summarizes our results but only comprises the 21 new flare stars found. The many flare-up repetitions in the previously known flare stars are not included. The numbering of the new flare stars is the continuation of the serial numbers used by Haro and Gonzalez (1972) and Haro and Chavira (1972). The coordinates and U magnitudes given are approximate. As can be noticed from Table 1 the brightest new flare stars are H_II 2244, H_II 1883 and H_II 1100, which have visual magnitudes during minima equal to 12.67, 12.60 and 12.16, respectively, according to the Johnson and Mitchell (1958) photoelectric photometry. Star H_II 1100, according to Wilson (1963), shows a K3Ve spectral type. If we consider that Kraft and Greenstein (1969) classified the Pleiades stars H_II 740, H_II 2588 and H_II 2908 as having K3Ve spectral types, we find an extremely large magnitude and color dispersion amongst these Pleiades star members. This can be interpreted either as the result of a) Possible discrepancies in the spectral classification criteria used by Wilson and by Kraft and Greenstein; b) Errors in the Johnson and Mitchell photometry larger than the one recognized before (Iriarte 1967); c) Real intrinsic differences amongst these Pleiades stars due to stellar evolution effects. We are inclined to give more weight to this last supposition. April 13, 1973 G. HARO and E. CHAVIRA Instituto Nacional de Astrofisica, Optica y Electronica Tonantzintla, Mexico. TABLE 1 New Flare stars in the Pleiades Region (1972-1973) ----------------------------------------------------------------------------------------------- No Star R.A. Dec. Mag.in U DeltamU Date of (1900) (1900) (Minimum) Flare-up ----------------------------------------------------------------------------------------------- 35b 3h34.1m +24d28' 19.8 3.3 2 Oct.1972 36b 3 34.8 21 55 19.4 2.8 7 Jan.1973 37b 3 37.3 24 03 17.0 0.4 6 Nov.1972 38b 3 37.6 25 17 19.0 3.0 6 Oct.1972 39b HII 133 3 37.6 24 05 17.0 0.8 7 Jan.1973 40b 3 38.1 25 21 14.8 2.8 4 Oct.1972 41b 3 38.4 24 33 19.6 5.6 2 Jan.1973 42b 3 38.4 14 28 17.2 3.7 9 Jan.1973 43b HII 1100 3 40.6 24 02 14.46 0.6 3 Feb.1973 44b HII 1114 3 40.7 24 38 16.6 0.8 13 Nov.1972 45b HII 1355 3 41.3 23 43 16.5 1.2 11 Nov.1972 46b 3 41.9 22 32 ~21.0 ~6.0 26 Jan.1973 47b 3 42.2 23 25 19.4 3.9 26 Jan.1973 48b HII 1883 3 42.5 22 59 14.37 2.1 11 Nov.1972 49b 3 41.6 22 33 >21.0 >6.7 7 Dec.1972 50b 3 43.3 25 23 19.0 5.0 7 Nov.1972 51b HII 2244 3 43.4 24 28 14.33 1.7 6 Feb.1973 52b 3 43.6 23 36 19.1 4.0 6 Dec.1972 53b 3 44.1 24 18 ~22.0 ~7.3 2 Oct.1972 54b 3 44.4 21 52 17.3 3.3 6 Feb.1973 55b HII 3063 3h45.5m +23d36' 15.7 1.0 6 Nov.1972 ----------------------------------------------------------------------------------------------- References: 1) Haro, G. and Gonzales, G., 1972, IAU Information Bulletin on Variable Stars No. 715. 2) Haro, G. and Chavira, E., 1972, IAU Information Bulletin on Variable Stars. No. 716. 3) Iriarte, B., 1967, Bol.Obs.Ton. y Tac.; 4, No. 28. pag. 79. [BIBCODE 1967BOTT....4...79I ] 4) Johnson, H.L. and Mitchell, R.I., 1958, Ap.J. 128, 31. [BIBCODE 1958ApJ...128...31J ] 5) Kraft, R.P. and Greenstein, J.L., 1969, Low Luminosity Stars, ed. S.S. Kumar (Gordon and Breach Science Publishers) p.65. [BIBCODE 1969lls..symp...65K ] 6) Wilson, O.C., 1963, Ap.J. 138, 832. [BIBCODE 1963ApJ...138..832W ]