======================================================================== 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. 14, No. 14 Feb 27, 2002 Recently submitted papers: -------------------------- 1) Sgr A* and Sgr A East: Intimate Life in the Galactic Center (Plewa & Rozyczka, Proc.) 2) The Origin of X-ray Emission from a Galactic Center Molecular Cloud: Low Energy Cosmic Ray Electrons (Yusef-Zadeh et al., ApJL) ------------------------------------------------------------------------ Email : tomek@flash.uchicago.edu Title : Sgr A* and Sgr A East: Intimate Life in the Galactic Center Author(s): Tomasz Plewa(1), \& Michal Rozyczka(2) Institute: (1) Center for Astrophysical Thermonuclear Flashes, The University of Chicago, Chicago, IL 60637, USA (2) N. Copernicus Astronomical Center, Bartycka 18, 00716 Warsaw, Poland Paper : to appear in M. Rosado, L. Binette and L. Arias, eds, ASP Conf. Series, Proceedings of the Conference Galaxies: the Third Dimension, Cozumel, Mexico, December 3-7, 2001 EPrint : astro-ph/0202470 Abstract: A hydrodynamic interaction between an old supernova remnant and a massive black hole is studied with the help of a high-resolution adaptive mesh refinement code. A series of multidimensional numerical models is obtained for a fixed distance between supernova explosion site and the black hole but different densities of the ambient medium. The interaction between the shell of the supernova remnant and the black hole results in a rapid increase of the emission from the vicinity of the black hole. Light curves of the gas heated by gravitational compression and hydrodynamical interactions are obtained assuming optically thin conditions. It is shown that the duration of the event and the peak luminosity critically depend on the density of the ambient medium. The model is applied to the data obtained by the Chandra satellite for the Galactic center. ------------------------------------------------------------------------ Email : zadeh@oort.astro.nwu.edu Title : The Origin of X-ray Emission from a Galactic Center Molecular Cloud: Low Energy Cosmic Ray Electrons Author(s): F. Yusef-Zadeh, C. Law, and M. Wardle Paper : ApJL, in press EPrint : astro-ph/0202442 Abstract: The Galactic center region near l 0.2^0 hosts a mixture of nonthermal linear filaments and thermal radio continuum features associated with the radio Arc. Chandra observations of this region reveal an X-ray filament and diffuse emission with an extent of roughly 60''*2'' and 5'*3', respectively. The X-ray filament lies at the edge of the nonthermal radio filaments and a dense molecular shell G0.13-0.13 that has an unusually high kinetic temperature >=70K. These observations demonstrate that the G0.13-0.13 molecular cloud and the nonthermal radio filaments of the Arc are interacting. The diffuse X-ray emission is correlated with the molecular shell and is fitted either by two-temperature (1 and 10 keV) thermal emission or by power-law and 1 keV thermal gas. Fluorescent 6.4 keV line emission is also detected throughout the molecular shell. This cloud coincides within the error circle of a steady unidentified EGRET source 3EGJ1746-2851. We argue that low-energy cosmic ray electrons (LECRe) produce the power-law continuum by bremsstrahlung and 6.4 keV line emission from the filament and the diffuse cloud with the implication on the origin of the Galactic ridge X-ray emission. The strong 6.4 keV Fe-line emission seen from other Galactic center clouds could be produced in a similar fashion rather than via fluorescent emission induced by a transient hard X-ray source in the Galactic center. In addition, heating by ionization induced by LECRe are also responsible for the high temperature of G0.13-0.13. The gamma-ray source is a result of brehmsstrahlung by the high-energy tail of the electron energy distribution. ------------------------------------------------------------------------ (Older versions of the Newsflash can be found at the gcnews web-page) ======================================================================== Edited by Angela Cotera Heino Falcke & Sera Markoff (cotera@as.arizona.edu) (hfalcke,smarkoff@mpifr-bonn.mpg.de) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - For Abstract submission please send the (La)Tex file of your paper to gcnews@mpifr-bonn.mpg.de ========================================================================