Circular No. 3306 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION Postal Address: Central Bureau for Astronomical Telegrams Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. TWX 710-320-6842 ASTROGRAM CAM Telephone 617-864-5758 VARIABLE-EMISSION-LINE STAR IN THE CORE OF M15 H. Ford, B. Margon and D. Jenner, University of California at Los Angeles; and A. Klemola, University of California at Santa Cruz, write: "Observations have been made of a subgiant star 14" north-east of the center of M15 that shows strong, variable, Balmer emission lines. The object is No. 86 in the list of Rosino (1950, Astrophys. J. 112, 221), where a finding chart may be found. The star was bright on Kitt Peak H-alpha video camera photographs obtained on 1977 Dec. 5, and it showed strong H-alpha, H-beta and H-gamma emission lines in spectra obtained with the Lick Observatory's 305-cm telescope on 1978 Sept. 30 and Oct. 1. The strength of the emission changed by 50 percent on the two successive nights. The emission is entirely absent on spectra obtained with the Kitt Peak 400-cm telescope on 1978 Oct. 29, 30 and 31. The emission lines are blueshifted 40 km/s relative to the cluster, while the Balmer absorption lines observed at the end of October have the same radial velocity as the cluster. The astrometric positions (+/- 0".5 accuracy) of the star, the cluster center and the planetary nebula K648 (useful as a positional reference) have been measured from short-exposure Lick refractor and astrograph plates as: R.A. (1950) Decl. Star No. 86 21 27 34.14 +11 56 54.8 Cluster center 21 27 33.30 +11 56 48.4 K648 21 27 34.52 +11 57 16.1 The star is 4" from the center of the 20"-radius SAS-3 error circle for the x-ray source 4U 2129+12 (Jernigan and Clark, preprint). Notni and Oleak (1957, Astron. Nachr. 284, 49) note the object to be variable by 0.9 magnitude (mean V = 14.4) with period 17.1 days, suggesting a possible interpretation as a long-period Population II Cepheid; our observed spectral features and color, B-V = +0.7, are indeed consistent with a W-Vir star. However, the presence of this large-amplitude spectroscopic and photometric variable in the small x-ray error box is sufficiently unusual that the alternative interpretation of a relation to the x-ray source should not be overlooked." V861 SCORPII In the table on IAUC 3281 the +/- errors quoted are percentage errors rather than absolute errors. 1978 November 15 (3306) Brian G. Marsden
Our Web policy. Index to the CBAT/MPC/ICQ pages.