======================================================================== G C N E W S * Newsflash * - The Newsletter for Galactic Center Research - gcnews@mpifr-bonn.mpg.de http://www.mpifr-bonn.mpg.de/gcnews ======================================================================== Vol. 9, No. 11 Dec 7, 1998 Recently submitted papers: -------------------------- 1) SPECTROSCOPY OF THE PISTOL AND QUINTUPLET STARS IN THE GALACTIC CENTRE (Moneti et al., ISO Proc.) 2) The Stellar Content of Obscured Galactic Giant H II Regions: I. W43 (Blum et al., AJ) 3) The jet/disk symbiosis III. What the radio cores in GRS 1915+105, NGC 4258, M81, and Sgr A tell us about accreting black holes (Falcke & Biermann, A&A) Email : amoneti@iso.vilspa.esa.es Title : SPECTROSCOPY OF THE PISTOL AND QUINTUPLET STARS IN THE GALACTIC CENTRE Author(s): A. Moneti(1,2), J.A.D.L. Blommaert(1), F. Najarro(3), D. Figer(4), S. Stolovy(4) Institute: (1) ISO Data Centre, ESA Astrophysics Division, Villafranca del Castillo, Spain., (2) On contract from SERCo F.M. B.V., (3) IEM, Consejo Superior de Investigaciones Cientificas, Madrid, Spain., (4) University of California, Los Angeles, CA, USA., (5) Steward Observatory, Tucson, AZ, USA., Paper : to appear in "The Universe as seen by ISO" proc's Weblink : http://www.iso.vilspa.esa.es/science/publications.html EPrint : astro-ph/9812046 Abstract: We present initial results of a spectroscopic study of the Pistol and of the cocoon stars in the Quintuplet Cluster. From ISOCAM CVF 5--17\mic spectroscopy of the field of the Pistol Star, we have discovered a nearly spherical shell of hot dust surrounding this star, a probable LBV. This shell is most prominent at lambda >~ 12\mic, and its morphology clearly indicates that the shell is stellar ejecta. Emission line images show that most of the ionised material is along the northern border of this shell, and its morphology is very similar to that of the Pistol \HH region (Yusef-Zadeh \& Morris, 1987). We thus confirm that the ionisation comes from very hot stars in the core of the Quintuplet Cluster. An SWS spectrum of the Pistol Nebula indicates a harder ionising radiation than could be provided by the Pistol Star, but which is consistent with ionisation from Wolf-Rayet stars in the Quintuplet Cluster. The CVF 5--17\mic spectra of the cocoon stars in the Quintuplet do not show any emission feature that could help elucidate their nature. ------------------------------------------------------------------------ Email : blum@ctiowe.ctio.noao.edu Title : The Stellar Content of Obscured Galactic Giant H II Regions: I. W43 Author(s): R. D. Blum(2) A. Damineli(2,3) P. S. Conti Institute: (1) Cerro Tololo Interamerican Observatory, Casilla 603, La Serena, Chile, rblum@noao.edu (2) IAG-USP, Av. Miguel Stefano 4200, 04301-904, Sao Paulo, Brazil ,damineli@iagusp.usp.br (3) JILA, University of Colorado,Campus Box 440, Boulder, CO, 80309,pconti@casa.colorado.edu Paper : to appear in AJ, March 1999 Weblink : http://www.ctio.noao.edu/ftp/pub/blum/ EPrint : astro-ph/9812070 Abstract: Near infrared images of the Galactic giant H II region W43 reveal a dense stellar cluster at its center. Broad band JHK photometry of the young cluster and K-band spectra of three of its bright stars are presented. The 2 \mic spectrum of the brightest star in the cluster is very well matched to the spectra of Wolf-Rayet stars of sub-type WN7. Two other stars are identified as O type giants or supergiants by their NIII and CIV emission. The close spatial clustering of O and the hydrogen WN type stars is analogous to the intense star burst clusters R136 in the Large Magellanic Cloud and NGC 3603 in the Galaxy. ------------------------------------------------------------------------ Email : hfalcke@mpifr-bonn.mpg.de Title : The jet/disk symbiosis III. What the radio cores in GRS 1915+105, NGC 4258, M81, and Sgr A tell us about accreting black holes Author(s): Heino Falcke and Peter L. Biermann Institute: Max-Planck Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn, Germany Paper : A&A 342, in press Weblink : http://www.aoc.nrao.edu/mpivlb/falcke/publications.html# jdiii EPrint : astro-ph/9810226 Abstract: We have derived simplified equations for a freely expanding, pressure driven jet model as a function of jet power and applied it successfully to the radio cores in the black hole candidates GRS 1915+105, NGC 4258, and M81 which are observationally well defined systems, and to Sgr A*. By using equipartition assumptions, the model has virtually no free parameters and can explain all sources by just scaling the jet power. In GRS 1915+105 it also naturally explains the jet velocity and the radio time delay. The jet powers we derive for the radio cores of the first three sources are comparable to their accretion disk luminosities, providing further evidence for the existence of symbiotic jet/disk systems and a common engine mechanism also in low-luminosity AGN and stellar mass black holes. With the exception of Sgr A* an advection dominated accretion flow (ADAF) does not seem to be necessary to explain any of the radio cores which span a large range in luminosity and size, as well as in black hole masses and accretion rate--from Eddington to extreme sub-Eddington. We suggest, however, that the jet model can be used to derive minimum accretion rates and thus find that Sgr A* seems to be truly radiatively deficient--even in a starved black hole model--and that a combination of jet and ADAF model may be one possible solution. ------------------------------------------------------------------------ (Older versions of the Newsflash can be found at the gcnews web-page) ======================================================================== Edited by Angela Cotera Heino Falcke (cotera@ipac.caltech.edu) (hfalcke@mpifr-bonn.mpg.de) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - For Abstract submission please send the (La)Tex file of your paper to gcnews@mpifr-bonn.mpg.de ========================================================================