From koyama@cr.scphys.kyoto-u.ac.jp Mon Apr 22 22:13:54 1996
Date: Tue, 23 Apr 96 11:13:48 +0900
From: koyama@cr.scphys.kyoto-u.ac.jp (Katsuji Koyama)
To: gcnews@astro.umd.edu
\documentstyle[12pt]{article}

\title{ ASCA View of Our Galactic Center:\\
           Remains of Past Activities in X-Rays?}

\author{K. KOYAMA$^{1}$ Y. MAEDA$^{1}$
T. SONOBE$^{2}$ T. TAKESHIMA$^{3}$ \\
Y. TANAKA$^{4,2}$ and S. YAMAUCHI$^{5}$} 


\maketitle

\scriptsize 
\noindent
\institute{
$^{1}$ Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-01\\
$^{2}$ Institute of Space \& Astronautical Science, 3-1-1 Yoshinodai, 
Sagamihara, Kanagawa 229\\
$^{3}$ Laboratory for High Energy Astrophysics, Code 668, NASA/GSFC, 
Greenbelt, MD 20771, USA\\
$^{4}$ Max-Planck Institut f\"{u}r Extraterrestrische Physik, D-85748 
Garching, Germany\\ 
$^{5}$ College of Humanities \& Social Science, Iwate University, 3-18-34 
Ueda, Morioka, Iwate 020}

(Received 1995 October 23; accepted 1996 February 6)


\normalsize
\begin{abstract}
Detailed X-ray images and spectra of the Galactic-center region up to 
10 keV were obtained with ASCA.  
Diffuse thermal-emission with distinct K$\alpha$ lines from highly 
ionized ions of various elements has confirmed the presence of an extended 
high-temperature plasma. 
The fluorescent X-ray emission from cold iron atoms in molecular clouds was 
also found, possibly due to irradiation by X-rays from the center, which 
was bright in the past, but is presently dim. 
The results suggest that the Galactic center exhibited intermittent 
activities with a time-averaged energy generation rate comparable to 
Seyfert nuclei, a class of active galactic nuclei.
\end{abstract}

Key words: Galaxies: Milky Way -- Interstellar: clouds -- X-rays: sources -- X-rays : spectra \\ 

\end{document}











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