COMMISSION 27 OF THE I.A.U. INFORMATION BULLETIN ON VARIABLE STARS Number 2961 Konkoly Observatory Budapest 3 December 1986 HU ISSN 0374 - 0676 NEW AND NEGLECTED VARIABLES IN THE CEPHEUS OB 2 ASSOCIATION An objective prism search for H_alpha emission stars in the region of IC 1396 was begun at Konkoly Observatory in 1980 in order to find the possible low mass members of the association Cep OB 2. The first results of this survey are already published (Kun, 1986). Further emission stars were detected on four plates taken in 1985-86. Among them there are four stars which were found to be variable by Gieseking (1976). A photographic UBV photometry of the H_alpha emission stars led to the discovery of five new variable stars. Their coordinates for 1950, V magnitudes at three different epochs, B-V and in some cases U-B colour indices are given in Table I. Identification charts are presented in Fig. 1. The photometric plates were obtained with the 60/90/180 cm Schmidt telescope of Konkoly Observatory. The variability of the stars was established from six plates taken on three nights (27/28 June 1968, 20/21 Oct 1985 and 13/14 Sept 1986). The photographic magnitude scale was calibrated using Lichtbuer's (1982) photoelectric sequence. The mean internal error of the magnitudes derived as averages from six plates is about 0.1 mag. A star is regarded here variable if the rms scatter of its magnitude averaged from six plates exceeds 0m.4. The Julian dates given in Table I are the means of the beginning of the first exposure and the end of the second exposure of the given night. The magnitudes listed at a given JD are averages of two plates. B-V, and where the brightness of the star made it possible, U-B colour indices were also derived from two plates in each colour taken on the same night (20/21 Oct 1985). We extended the photometry for some already known variable and extremely red stars situated within our field which is of five degrees in diameter and is centred on HD 206267, the exciting star of IC 1396, because there is very scarce information in the literature for these stars. These stars are as follows: a) DZ, GL and GM Cep, probable Orion-variables. Their light variations have been investigated photographically by Suyarkova (1975) and Albo (1979a, b), DZ and GM Cep show H_alpha emission on our objective prism plates. Table I JD 2400000+ 39035.5 46359.4 46691.5 N R.A.(1950) D(1950) V V B-V U-B V 1 21h27m10s0 +58d06'00" 15.33 15.94 2.76 16.19 2 21 31 47.4 +57 34 52 16.28 15.10 2.23 0.14 14.95 3 21 37 9.2 +57 16 53 16.47 14.22 2.44 1.16 15.55 4 21 48 5.8 +56 32 34 13.18 14.38 0.96 1.03 14.22 5 21 49 9.0 +55 57 6 13.80 14.22 1.15 0.04 13.20 Notes to Table I: 1. Star No. 20 from Dorschner et al.(1973) 3. Star No. 80 from Kun (1986) 4, 5. Stars 21-040 and 21-041 from Dolidze (1975), respectively [FIGURE 1] Figure 1. North is at the top and east is to the left. 10'=4cm. b) Red variables, which, because of their colour and large amplitude are regarded as possible Miras. They are as follows: - V345 Cep which was listed as an extremely red star by Dorschner et al. (1973). Its light variation was discovered by Friedemann et al. (1977). - V346, V347, V348 and V349 Cep, red variables found by Pfau and Friedemann (1980). - Stars C, D and E from a list of red variables by Friedemann et al. (1977), later designated as JV 19, 20 and 21 by Pfau and Friedemann (1980). Table II JD 2400000+ 39035.5 46359.4 46691.5 Name V V B-V U-B V Remark GL Cep 11.34 11.38 2.37 11.57 GM Cep 12.87 14.30 3,01 15.02 H_alpha emission DZ Cep 13.63 14.30 1.21 0.67 13.93 H_alpha emission V345 Cep 12.22 13.73 4.34 14.86 V346 Cep 14.07 13.91 2.76 14.56 V347 Cep 15.80 12.58 3.17 0.88 15.62 Gieseking 11 V348 Cep 14.55 14.52 1.67 14.42 JV 19 16.43 15.93 4.06 16.71 JV 20 -- 17: 2.8: 14.13 JV 21 -- 16.9 1.9 16.8 Gieseking 6 15.25 15.03 1.87 14.86 Gieseking 15 13.20 13.56 1.21 13.38 Gieseking 17 15.18 15.39 0.66 0.56 15.42 H_alpha emission Gieseking 18 15.18 15.57 1.09 0.45 16.17 H_alpha emission Gieseking 19 14.75 16.70 2.15 -0.09 15.68 CSV 8684 Gieseking 20 15.39 15.07 1.02 15.68 H_alpha emission Gieseking 23 -- 16.0 1.04 15.68 Gieseking 24 15.10 15.45 0.52 0.50 15.13 H_alpha emission Dorschner 21 14.68 14.32 4.87 14.57 Dorschner 22 15.35 14.75 4.42 15.16 Dorschner 23 15.75 15.70 1.33 15.68 Dorschner 24 12.51 12.39 3.36 12.17 Dorschner 25 16.10 16.00 2.30 16.28 Table III IRAS source Associated object R.A.(1950) D(1950) R.A.(1950) D(1950) 21h24m58.7 +57d54'01" 21h24m59s0 +57d54' V346 Cep 21 28 2.2 +57 46 12 21 28 6.0 +57 46 12" V347 Cep 21 28 54.5 +55 14 18.9 21 28 55 +55 14 JV 19 21 30 45.5 +56 13 16.0 21 30 46 +56 14 JV 20 21 31 47.6 +57 34 52.0 21 31 47.4 +57 34 51.7 No. 2 21 32 56.2 +56 47 36 21 32 59 +56 48 Dorschner 24 21 33 47.2 +57 23 8.0 21 33 47.7 +57 23 15 Gieseking 15 21 36 15.3 +57 30 42.0 21 36 12.0 +57 31 0 GL Cep* 21 36 44.7 +57 17 45.0 21 36 44.0 +57 19 12 GM Cep* 21 37 9.0 +57 16 42.9 21 37 9.2 +57 16 53 No.3 21 41 16.5 +58 43 32.9 21 41 16.4 +58 43 34 Gieseking 19 * The identification is given in the IRAS Point Source Catalogue. c) Unnamed faint variables found by Geyer and Gieseking (1975) and Gieseking (1976) during a photographic search for variable stars around Mu Cephei. Stars Nos. 6, 11, 15, 17, 18, 19 (=CSV 8684), 20, 23 and 24 are situated within our field. No. 11 happens to be identical with V347 Cep but Gieseking finds it equally bright in the red and blue. Among these stars, Nos. 17, 18, 20 and 24 show H_alpha emission on our objective prism plates. Regarding their relatively blue colour they are possibly Orion-variables. d) Stars Nos. 20, 21, 22, 23, 24 and 25 from a list of extremely red stars by Dorschner et al. (1973) were also measured because their very red colour suggests that they might be variables. No. 20 is found to be variable and in addition it shows H_alpha emission on two objective prism plates taken in 1986. We remark here that our photometry shows these stars systematically brighter and bluer than the original photometry which was based on measuring the diameters of the stars on the Palomar Observatory Sky Survey prints. Table II summarizes the photographic magnitudes and colour indices for the above listed stars. Finally we mention that some of these stars seem to have counterparts in the IRAS Point Source Catalogue. GL and GM Cep are identified with infrared sources in the Catalogue. In Table III we give a comparison of the coordinates of further IRAS sources with those of our stars. In some cases there are other optical objects within the uncertainty ellipse. In these cases, beside the very good agreement of the coordinates the fact that these stars were selected on the basis of their red colour and/or H_alpha emission supports the identity of the stars and infrared objects. The poor information available for these stars is not enough to establish their types. The large amplitudes of their light variation, the H_alpha emission, red colour and the possible infrared excess together with their apparent location in a region of star formation suggest that at least some of them are pre-main sequence variables; these properties do not exclude, however, that some of them are of Mira type. They are worthy of further study. MARIA KUN Konkoly Observatory H-1525 Budapest, P.O. Box 67, Hungary References: Albo, H.: 1979a, Tartu Publ, 47, 171. [BIBCODE 1979PTarO..47..171A ] Albo, H.: 1979b, Tartu Publ. 47, 174. [BIBCODE 1979PTarO..47..174A ] Dorschner, J., Friedemann, C., Gurtler, J.: 1973, Astron. Nachr. 294, 153. [BIBCODE 1973AN....294..153D ] Dolidze, M. V.: 1975, Bull. Abastumani Obs. 47, 3. [BIBCODE 1975AbaOB..47....3D ] Friedemann, C, Gurtler, J., Pfau, W.: 1977, Astron. Nachr. 298, 327. [BIBCODE 1977AN....298..327F ] Geyer, E. H., Gieseking, F.: 1975, IBVS No. 967. Gieseking, F.: 1976, IBVS No. 1145 Kun, M.: 1986, Astrophys. Sp. Sci. 125, 13. [BIBCODE 1986Ap&SS.125...13K ] Lichtbuer, P. C.: 1982, Vatican Obs. Publ. 2, 1. [BIBCODE 1982VatOP...2....1C ] Pfau, W., Friedemann, C.: 1980, Astron. Nachr. 301, 69. [BIBCODE 1980AN....301...69P ] Suyarkova, O. G.: 1975, Per. Zv. 20, 167. [BIBCODE 1975PZ.....20..167S ]