Subject: GCFLASH - Vol. 6, No. 10 (Oct 16, 1997) ======================================================================== G C N E W S * Newsflash * - The Newsletter for Galactic Center Research - gcnews@astro.umd.edu http://www.astro.umd.edu/~gcnews ======================================================================== Vol. 6, No. 10 Oct 16, 1997 Recently submitted papers: -------------------------- 1) THE STELLAR CONTENT NEAR THE GALACTIC CENTER (Davidge et al., AJ) 2) The hard X-ray source GRS 1734-292: a Seyfert 1 galaxy behind the Galactic Center (Marti et al., A&A) ------------------------------------------------------------------------ Email : Tim.Davidge@hia.nrc.ca Title : THE STELLAR CONTENT NEAR THE GALACTIC CENTER Author(s): T. J. Davidge(1), D. A. Simons(2), F. Rigaut(3), R. Doyon(4), D. Crampton(5) Institute: (1) Canadian Gemini Project Office, Herzberg Institute of Astrophysics, National Research Council of Canada, 5071 W. Saanich Road, Victoria, BC, Canada V8X 4M6 ^a, and, Department of Physics & Astronomy, University of British Columbia, Vancouver, BC Canada V6T 1Z4, email: tim.davidge@hia.nrc.ca (2) Gemini Project Office, PO Box 26732, 950 N. Cherry Ave, Tucson, Arizona, USA 85726-6732, email: dsimons@gemini.edu (3) Canada-France-Hawaii Telescope, PO Box 1597, Kamuela, HI USA 96743, email: rigaut@cfht.hawaii.edu (4) D'epartement de Physique, Universit'e de Montr'eal, C.P. 6128, Succ. Centre Ville, Montreal, PQ Canada H3C 3J7, email: doyon@astro.umontreal.ca (5) Dominion Astrophysical Observatory, Herzberg Institute of Astrophysics, National Research Council of Canada, 5071 W. Saanich Road, Victoria, BC, Canada V8X 4M6, email: david.crampton@hia.nrc.ca Paper : AJ, in press EPrint : astro-ph/9710146 Abstract: High angular resolution J, H, K, and L' images are used to investigate the stellar content within 6 arcsec of SgrA*. The data, which are complete to K ~ 16, are the deepest multicolor observations of this region published to date. The mean locus of the (K, H-K) CMD varies across the field, a result that is attributed to differential reddening with amplitude Delta A_V ~ 15 mag. The reddening variations within 3 arcsec of SgrA* are significantly smaller than this, and the resolved members of the compact star cluster immediately surrounding SgrA* have photometric properties that are not significantly different from objects at larger radii. We find that sources in our field with published 2 micron spectra showing either line emission or CO absorption occupy different sequences on the (K, J-K) CMD. The emission line stars, which fall along the most richly populated sequence, have redder J-K colors than stars in the Magellanic Clouds with similar spectroscopic characteristics, and evidence is presented that this is due to excess infrared emission in the spectrum of the GC sources. The photometric properties of the giant branch, which is defined by stars showing CO absorption, are similar to those of the giant branch in Baade's Window (BW). The mean J-K color and peak K brightness of the red giant branch are both consistent with a metal-rich population having an age ~ 10 Gyr, while the width of the giant branch on the (K, J-K) CMD is indicative of an age spread Delta log(t) <= 1 dex. Therefore, if the inner bulge contains an underlying population of stars with ages in excess of ~ 10 Gyr, as is the case in BW, then the region within a few arcsec of SgrA* cannot contain a large population of giant branch stars younger than 1 Gyr. We also report the detection of a modest population of faint, blue sources with K >= 14. We speculate that these are bright main sequence stars at the distance of the GC, although spectra will be required to confirm this interpretation. Nevertheless, the photometric properties of the largely unresolved compact knot of stars immediately surrounding SgrA* provide indirect evidence to support the presence of a large population of faint blue stars. In particular, we confirm previous studies that measure a relatively blue color for this cluster. ------------------------------------------------------------------------ Email : chaty@discovery.saclay.cea.fr Title : The hard X-ray source GRS 1734-292: a Seyfert 1 galaxy behind the Galactic Center Author(s): J. Marti(1), .F. Mirabel(1), S. Chaty(1), & L.F. Rodriguez(2) Institute: (1) CEA/DSM/DAPNIA/Service d'Astrophysique, Centre d'Etudes de Saclay, 91191 Gif/Yvette, France, (2) Instituto de Astronomia, UNAM, Apdo. Postal 70-264, 04510 Mexico D.F., Mexico Paper : A&A, in press EPrint : astro-ph/9710136 Abstract: The radio, infrared and optical counterparts of the hard X-ray source GRS 1734-292 (l^II=358.9^o, b^II=+1.4^o) are reported. The optical spectrum exhibits broad (>1000 km s^-1) H alpha emission at a redshift of 0.0214+/-0.0005. The radio counterpart is a double-sided synchrotron jet of 5 arcsec, which at a distance of 87 Mpc corresponds to a size of 2 kpc. The multiwavelength observations of GRS 1734-292 indicate that this X-ray source is a Seyfert 1 galaxy behind 6+/-1 magnitudes of visual absorption. ------------------------------------------------------------------------ (Older versions of the Newsflash can be found at the gcnews web-page) ======================================================================== Edited by Angela Cotera Heino Falcke (cotera@ipac.caltech.edu) (hfalcke@astro.umd.edu) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - For Abstract submission please send the (La)Tex file of your paper to gcnews@astro.umd.edu ========================================================================