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                              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
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Vol. 14, No. 10                                              Feb 4, 2002

The feedback on our survey for the Galactic Center conference in
Hawaii was very positive - 108 people responded and we modified our
plans accordingly. More details will given in the next issue of GCNEWS
due later this month.

Recently submitted papers:
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1) Diffuse X-rays in the Galactic center region -- The zoo of iron line 
   clumps, non-thermal filaments and hot plasmas (Bamba et al., 
   Proceedings)
2) On the Nature of the X-ray Emission from the Galactic Center Region 
   (Wang et al., Nature)
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Email    : bamba@cr.scphys.kyoto-u.ac.jp
Title    : Diffuse X-rays in the Galactic center region -- The zoo of 
           iron line clumps, non-thermal filaments and hot plasmas
Author(s): Aya Bamba, Hiroshi Murakami, Atsushi, Shin-ichiro Takagi, 
           Jun Yokogawa, Katsuji Koyama
Institute: Department of Physics, Graduate School of Science, Kyoto 
           University, Kita-shirakawa, Sakyo-ku, Kyoto, 606-8502, Japan
Paper    : Proceedings of the Symposium "New Visions of the X-ray 
           Universe in the XMM-Newton and Chandra era", Noordwijk-NL, 
           November 2001
EPrint   : astro-ph/0202010
Web      : http://www-cr.scphys.kyoto-u.ac.jp/member/bamba/Proceeding/Ne
           wvision.ps.gz

Abstract:
This paper reports the diffuse X-ray features around the Galactic 
center observed with Chandra. We confirm the ASCA and Ginga discoveries 
of the large-scale thin-thermal plasma with strong lines in the 
Galactic center region. In addition, many small clumps of emission 
lines from neutral (6.4 keV line) to He-like (6.7 keV line) irons are 
discovered. The 6.4 keV line clumps would be reflection nebulae, while 
those of the 6.7 keV line are likely SNRs. We also find emission lines 
of intermediate energy between 6.5-6.7 keV, which are attributable to 
young SNRs in non equilibrium ionization. Non-thermal filaments or 
belts with X-ray spectra of no emission line are found, suggesting the 
Fermi acceleration site in a rapidly expanding shell. All these suggest 
that multiple-supernovae or extremely large explosion had occurred 
around the Galactic center region in the recent past.
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Email    : wqd@gcs.astro.umass.edu
Title    : On the Nature of the X-ray Emission from the Galactic Center 
           Region
Author(s): Q. D. Wang^1, E. V. Gotthelf^2, \& C. C. Lang^1
Institute: (1) Department of Astronomy, University of Massachusetts, 
           Amherst, MA 01003, USA (2) Columbia Astrophysics Laboratory, 
           Columbia University, New York, NY 10027, USA
Paper    : Nature, 415, 148
EPrint   : astro-ph/0201070

Abstract:
The origin of the X-ray emission from the central region of the Galaxy 
has remained a mystery, despite extensive study over the past two 
decades. A fundamental question is the relative contribution of the 
point-source and diffuse components of this emission, which is critical 
to understanding the high-energy phenomena and processes unique to this 
Galactic nuclear environment. Here, we report on results from a 
large-scale imaging survey of the Galactic center with sufficient 
spatial resolution to allow a clean separation of the two components. 
The He-like Fe K alpha emission, previously attributed to the diffuse 
emission, is found largely due to the discrete X-ray source population. 
The number and spectrum of such sources indicate the presence of 
numerous accreting white dwarfs, neutron stars, and/or black holes in 
the region. The diffuse X-ray emission dominates over the contribution 
from the faint discrete sources and is shown to be associated with 
distinct interstellar structures observed at radio and mid-infrared 
wavelengths, suggesting that it arises from the recent formation of 
massive stars. We have also mapped out the 6.4-keV fluorescence line 
emission from neutral to moderately ionized irons. The ubiquitous 
association of the emission with molecular gas indicates that either 
the X-ray radiation from the Galactic center was substantially more 
intense in the past than at present or non-relativistic cosmic-rays are 
important in producing Fe K shell vacancies.
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(Older versions of the Newsflash can be found at the gcnews web-page)
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			       Edited by
    Angela Cotera                       Heino Falcke & Sera Markoff
(cotera@as.arizona.edu)             (hfalcke,smarkoff@mpifr-bonn.mpg.de) 
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