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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. 13, No. 17                                              Aug 15, 2001

(This newsflash was a little bit delayed due to summer vacation.)
 
Recently submitted papers:
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1) X-Ray Observations on the Galactic Center Region (Koyama, proc.)
2) Monte Carlo cluster simulations to determine the rate of compact 
   star inspiraling to a central galactic black hole (Freitag, proc.)
3) X-ray source population of the Galactic center region obtained with 
   ASCA (Sakano et al., proc)
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Email    : hiro@cr.scphys.kyoto-u.ac.jp
Title    : X-Ray Observations on the Galactic Center Region
Author(s): Katsuji Koyama
Institute: Department of Physics, Graduate School of Science, Kyoto 
           University
Paper    : proc. of New Century of X-ray Astronomy, ASP Conf.
EPrint   : astro-ph/0108109

Abstract:
This paper reports on the early Chandra view of the Galactic center 
(GC) activities. The massive black hole Sgr A^* is extremely faint, 
while more bright diffuse X-ray emission is prevailing in the 
circumnuclear disk. Another high temperature plasma is found in the Sgr 
A East shell. This may indicate that Sgr A East is a supernova remnant, 
although no clear X-ray shell is found. A hint of non-thermal X-ray 
filaments is found, suggesting the presence of an acceleration site of 
extremely high-energy cosmic rays. The giant molecular cloud Sgr B2 is 
established to be an X-ray reflection nebula, possibly arising from the 
past Sgr A activities. Chandra further discovered high temperature 
shells, suggesting multiple supernova explosions near the GC region.
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Email    : marc.freitag@obs.unige.ch
Title    : Monte Carlo cluster simulations to determine the rate of 
           compact star inspiraling to a central galactic black hole
Author(s): Marc Freitag^1,2
Institute: ^1 Observatoire de Geneve, CH-1290 Sauverny, Switzerland, ^2 
           Physikalisches Institut, Universitaet Bern, CH-3012 Bern, 
           Switzerland
Paper    : 3rd LISA conference, Symposium paper appears in "Classical 
           and Quantum Gravity"
EPrint   : astro-ph/0107193

Abstract:
The capture and gradual inspiral of stellar mass objects by a massive 
black hole at the centre of a galaxy has been proposed as one of the 
most promising source of gravitational radiation to be detected by 
LISA. Unfortunately rate estimates for this process suffer from many 
uncertainties. Here we report on the use of our newly developed Monte 
Carlo stellar dynamics code to tackle this problem. We present results 
from simple galactic nuclei models that demonstrate the high potential 
of our approach and point out the aspects of the problem where an 
improved treatment seems desirable.
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Email    : mas@star.le.ac.uk
Title    : X-ray source population of the Galactic center region 
           obtained with ASCA
Author(s): Masaaki Sakano(1), Katsuji Koyama(2), Hiroshi Murakami(2), 
           Yoshitomo Maeda(3), Shigeo Yamauchi(4), The ASCA Galactic 
           plane/center survey team
Institute: (1) NASDA/SURP, Tsukuba, Ibaraki 305-8505, Japan, 
           sakano@oasis.tksc.nasda.go.jp (2) Kyoto Univ., Sakyo, Kyoto, 
           606-8502, Japan (3) Pennsylvania State Univ., University 
           Park, PA 16802-6305, USA (4) Iwate Univ., Morioka, Iwate, 
           020-8550, Japan
Paper    : proc of "New Century of X-ray Astronomy", 6-8 March 2001, 
           Yokohama, Japan
EPrint   : astro-ph/0107444
Web      : http://www-maxi.tksc.nasda.go.jp/%7Esakano/work/paper/index-e
           .html#Sakano2001asca2001

Abstract:
From the ASCA X-ray point-source list in the Galactic center 5* 5 
degree^2 region, we found the clear correlation between the position of 
the sources and the absorption. This fact implies that the major part 
of the absorption is due to the cold interstellar matter (ISM) in the 
line of sight. Using the correlation, we estimate the distribution of 
the cold ISM. We also found that the ratio of high mass binaries to low 
mass binaries is significantly smaller than that in the whole Galaxy or 
SMC, which implies that the past starburst activity in the Galactic 
center region was rather quiet.
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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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