Subject: GCFLASH - Vol. 3, No. 7 (Sep 15, 1996) ======================================================================== G C N E W S * Newsflash * - The Newsletter for Galactic Center Research - gcnews@astro.umd.edu http://www.astro.umd.edu/~gcnews ======================================================================== Vol. 3, No. 7 Sep 15, 1996 It was certainly worth waiting the 4 years it took to obtain reliable proper motions for stars in the central star cluster. The exciting results reported by Eckart and Genzel which now will appear in MNRAS finally make the GC (together with NGC 4258) one of the best black hole candidates known today. The second paper, by Nagata et al. about the Quintuplet and Object #17, is the first one we have received that reports ISO observations and we hope that there is more to come. This paper comes just in time, as the final program for the Miniworkshop on the Quintuplet/Pistol/Sickle complex will be distributed in the next Newsflash. Your GCNEWS Team Recently submitted papers: -------------------------- 1) Stellar Proper Motions in the Central 0.1 Parsec of the Galaxy (Eckart & Genzel, MNRAS) 2) ISOCAM CVF observations of the Quintuplet and Object #17 clusters near the Galactic Center (Nagata et al., A&A) ------------------------------------------------------------------------ Email : genzel@mpe-garching.mpg.de Title : Stellar Proper Motions in the Central 0.1 Parsec of the Galaxy Author(s): A.Eckart and R.Genzel Institute: (1) Max-Planck Institut fuer extraterrestrische Physik Garching, FRG Paper : to appear in MNRAS Abstract: We report the first results of a program to measure proper motions of stars in the innermost core of the Galaxy. From high resolution near-infrared imaging over the last 4 years we have determined proper motions for 39 stars between 0.03 and 0.3 pc from the compact radio source SgrA*. For 19 of these the derived motions are more significant than 4 sigma in at least one coordinate. Proper motion and radial velocity dispersions are in very good agreement indicating that the stellar velocity field on average is close to isotropic. Taking radial and proper motion data together the dynamic evidence is now strong that there is a 2.45(+/-0.4) x 1e6 Mo central dark mass located within <0.015 pc of SgrA*. Its mass density is at least 6.5x1e9 Mo pc-3 excluding that the central mass concentration is in form of a compact white dwarf or neutron star cluster. In addition, we have detected significant changes in the structure of the innermost complex of stars in the immediate vicinity of SgrA*, implying in at least one case stellar motions of ~1500 km/s within ~0.01 pc of the compact radio source. Including this preliminary evidence, the inferred density of the central dark mass would then have to be in excess of 1e12 Mo pc-3, implying that the central mass concentration is likely a single massive black hole. ------------------------------------------------------------------------ Email : nagata@zlab.phys.nagoya-u.ac.jp Title : ISOCAM CVF observations of the Quintuplet and Object #17 clusters near the Galactic Center Author(s): T. Nagata(1), K. Kawara(2,3), T. Onaka(4), Y. Kitamura(2), and H. Okuda(2) Institute: (1) Department of Physics, Nagoya University, Nagoya 464-01, Japan (nagata@zlab.phys.nagoya-u.ac.jp) (2) Institute of Space and Astronautical Science, Yoshinodai, Sagamihara 229, Japan (3) ISO Science Operations Centre, Astrophysics Division of ESA, Villafranca, 28080 Madrid, Spain (4) Department of Astronomy, University of Tokyo, Tokyo 113, Japan Paper : Accepted in A&A (First results from ISO) Abstract: Two fields near the Galactic Center, containing the Quintuplet and Object #17 star-clusters, have been imaged with the ISOCAM circular variable filters (CVFs) in the wavelength range of 2.47 - 3.08 micron and 3.99 - 9.09 micron . Emission of [Ar II] 6.99 micron is detected in the ``pistol-shaped'' H II region (G0.15-0.05) to the south of the Quintuplet cluster. Absorption probably due to O-H stretching vibration (2.8 micron) is evident in the Quintuplet spectra. In addition, Quintuplet members and the central part of Object #17 have CO_2(4.3 micron ) and CO (4.7 micron) absorption. Abundant CO_2 might be present in these lines of sight. ------------------------------------------------------------------------ (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 ========================================================================