======================================================================== G C N E W S * Newsflash * - The Newsletter for Galactic Center Research - gcnews@aoc.nrao.edu http://www.aoc.nrao.edu/~gcnews ======================================================================== Vol. 22, No. 6 Oct 6, 2005 Recently submitted papers: -------------------------- 1) Stochastic Electron Acceleration During the NIR and X-ray Flares in Sagittarius A* (Liu et al., ApJ) 2) Constraining the Nature of the Galactic Center X-ray Source Population (Laycock et al., ApJL) ------------------------------------------------------------------------ Email : liusm@stanford.edu Title : Stochastic Electron Acceleration During the NIR and X-ray Flares in Sagittarius A* Author(s): Siming Liu(1), Fulvio Melia(2,3), and Vahe Petrosian(1,4) Institute: (1) Center for Space Science and Astrophysics, Department of Physics, Stanford University, Stanford, CA 94305 (2)Physics Department and Steward Observatory, The University of Arizona, Tucson, AZ 85721 (3) Sir Thomas Lyle Fellow and Miegunyah Fellow. (4) Department of Applied Physics, Stanford University, Stanford, CA 94305 Paper : ApJ in press EPrint : astro-ph/0506151 Abstract: Recent near-IR (NIR) and X-ray observations of Sagittarius A*'s spectrum have yielded several strong constraints on the transient energizing mechanism, justifying a re-examination of the stochastic acceleration model proposed previously for these events. We here demonstrate that the new results are fully consistent with the acceleration of electrons via the transit-time damping process. But more importantly, these new NIR and X-ray flares now can constrain the source size, the gas density, the magnetic field, and the wave energy density in the turbulent plasma. Future simultaneous multi-wavelength observations with good spectral information will, in addition, allow us to study their temporal evolution, which will eventually lead to an accurate determination of the behavior of the plasma just minutes prior to its absorption by the black hole. ------------------------------------------------------------------------ Email : silas@head.cfa.harvard.edu Title : Constraining the Nature of the Galactic Center X-ray Source Population Author(s): S. Laycock(1), J. Grindlay(1), M. van den Berg(1), P. Zhao(1), J. Hong(1), X. Koenig(1), E. M. Schlegel(1), S. E. Persson(2) Institute: (1) Harvard-Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA, 02138 (2) Observatories of the Carnegie Institution of Washington, 813 Santa Barbara St., Pasadena, CA, 91101 Paper : ApJ Letters (in press) EPrint : astro-ph/0509783 Web : http://hea-www.harvard.edu/ChaMPlane/index.html Abstract: We searched for infrared counterparts to the cluster of X-ray point sources discovered by Chandra in the Galactic Center Region (GCR). While the sources could be white dwarfs, neutron stars, or black holes accreting from stellar companions, their X-ray properties are consistent with magnetic Cataclysmic Variables, or High Mass X-ray Binaries (HMXB) at low accretion-rates. A direct way to decide between these possibilities and hence between alternative formation scenarios is to measure or constrain the luminosity distribution of the companions. Using infrared (J, H, K, Br gamma ) imaging, we searched for counterparts corresponding to typical HMXB secondaries: spectral type B0V with K<15 at the GCR. We found no significant excess of bright stars in Chandra error circles, indicating that HMXBs are not the dominant X-ray source population, and account for fewer than 10% of the hardest X-ray sources. ------------------------------------------------------------------------ (Older versions of the Newsflash can be found at the gcnews web-page) ======================================================================== Edited by Sera Markoff, Loránt Sjouwerman, Joseph Lazio, Cornelia Lang, Rainer Schödel, Robin Herrnstein - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - For Abstract submission please follow the instructions which are at http://www.aoc.nrao.edu/~gcnews/home/submission.shtml ========================================================================