COMMISSIONS 27 AND 42 OF THE IAU INFORMATION BULLETIN ON VARIABLE STARS Number 3892 Konkoly Observatory Budapest 7 June 1993 HU ISSN 0374 - 0676 26 NEW Halpha EMISSION OBJECTS Between 1950 and 1953 Haro found a fair number of stars with strong emission in the Halpha line of hydrogen in the region of the Orion nebula. He also observed the occurrence of flares in some of these emission stars, as well as temporal variations in the intensity of the Halpha lines. Further analysis of a large number of variable and flare stars detected in this region shows that many of the possible members of the Orion associations are characterized by this flare activity and the presence of the intense emissions in Halpha. The present paper is based on a review of plates of the Tonantzintla collection that covers several regions. The set analyzed consists of six Eastman Kodak plates taken with the Schmidt telescope at Tonantzintla; all star images were dispersed with a 4 objective prism and catalogued as "Halpha" in the files of the Tonantzintla Observatory. Table 1 lists the identification and characteristics of these plates as well as their corresponding regions on the plates of the Palomar Sky Survey and the number of objects with Halpha in emission. Each one was analyzed with a microscope to find conspicuous intensity in emission of the Halpha line in each of hundreds of registered spectra. Several objects with the desired characteristics were found and in order to determine if these were "new" or had been previously reported, their counterparts in the Palomar Sky Survey were identified in order to accurately determine the coordinates of all objects found with Halpha emission. As references, at least twenty stars with well determined positions were identified on each plate and both reference and problem stars were measured in the Zeiss stereo-comparator at the INAOE. The precision attained with such an instrument is of seven microns which corresponds, in arcsec, to 0.7 on the Tonantzintla plates. The positions were transformed from the measured x-y coordinates into equatorial coordinates by means of the RPLAS computational program (Salazar, 1989). In Table 2 the 26 newly determined objects with strong Halpha emission are listed along with their inferred 1950 coordinates. These objects were checked in the Herbig and Robbin Bell (1988) catalogue and have not yet been listed. Table 1. Schmidt plates reviewed and the number of Halpha objects found on each one. ---------------------------------------------------- Tonantzintla Palomar Halpha objects on each plate ---------------------------------------------------- S.T.6272 E-406 +24 5 38 1 A.C.3102 E-1314 +30 4 46 3 S.T.7934 E-668 +42 5 00 1 S.T.7934 E-644 +42 4 30 3 S.T.6245 E-1297 +12 5 12 4 A.C.3738 E-1455 +30 5 38 12 A.C.3738 E-1459 +30 5 12 2 S.T.6319 No Halpha objects found ---------------------------------------------------- Table 2. Coordinates of the newly determined objects with Halpha emission. ---------------------------------------- ID R.A. (1950) DEC ---------------------------------------- 1 4h51m47.4s 41d32'36.3" 2 4 53 41.9 27 38 26.2 3 4 56 52.3 29 56 43.3 4 5 00 24.5 27 32 52.6 5 4 55 36.6 44 46 13.6 6 4 53 33.1 43 09 54.5 7 4 46 40.7 41 35 31.2 8 4 42 46.2 44 08 08.3 9 5 18 17.6 14 41 12.3 10 5 09 48.8 14 53 52.0 11 5 07 27.0 14 17 54.4 12 5 08 44.5 10 28 46.4 13 5 40 28.9 28 13 22.1 14 5 40 37.8 28 45 37.7 15 5 44 26.5 31 11 49.1 16 5 33 49.4 31 42 11.9 17 5 37 12.1 30 38 52.6 18 5 36 49.5 28 41 21.0 19 5 35 46.7 27 58 29.3 20 5 35 47.3 28 26 02.1 21 5 34 51.1 28 46 19.2 22 5 35 08.2 29 02 30.6 23 5 31 57.6 31 38 44.9 24 5 32 59.7 32 55 18.9 25 5 24 14.5 31 21 30.0 26 5 23 58.0 30 11 32.0 ---------------------------------------- Acknowledgements. We would like to thank G. Vazquez for assistance with the RPLAS computing, Dr. Parsamian for her critical comments and guidance and J. A. Miller for checking the English version. This was a class project in an Observational Astronomy course at the INAOE. A. PICENO 1, C. ESCAMILLA 1 and J. H. PENA 2 1 Instituto Nacional de Astrofisica, Optica y Electronica 2 Instituto de Astronomia, UNAM References: Herbig, G.H., and Robbin Bell, K. 1988, Lick Observatory Bulletin No. 1111. [BIBCODE 1988cels.book.....H ] Salazar, G., 1989, Thesis. Benemerita Universidad Nacional Autonoma de Puebla, Mexico.