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To reveal the origin of the cosmic X-ray background (CXB) in the hard band, we are now conducting a wide (~ 7 deg2) and deep (~ 1 × 10−13 erg sec−1 cm−2 in the 2-10 keV band) survey with the ASCA (the ASCA Large Sky Survey, hereafter LSS). We have detected 83 sources above 4 sigma level in the 0.7-10 keV band with the GIS and resolved ~30% of the CXB in the 2-10 keV band into discrete sources (Ueda 1996). AGNs (type 1 and type 2) and clusters of galaxies are expected to be major contributers to these X-ray sources.
The complex radio source Sgr A is embedded in a region near our Galactic Center. The dynamical center of our Galaxy is considered to be Sgr A*, the compact non-thermal radio source. Dynamical mass within ~0.1 pc from Sgr A* has been estimated to be ~ 3×106 M⊙. This places Sgr A* to be a candidate of a massive blackhole (Eckart and Genzel, 1997 and reference therein).
Questionnaire surveys were implemented to study the incidence and physicians' knowledge of Vibrio vulnificus infections in Japan. Registered emergency physicians were selected by stratified random sampling for a questionnaire survey. A total of 235 out of 386 physicians (61%) responded to the questionnaire and 12 V. vulnificus septicaemia cases were reported from 10 respondents. The annual estimated number of V. vulnificus septicaemia was calculated as 425 (95% CI 238–752). The study also revealed that only 15·7% (95% CI 11·3–21·0) of responding physicians had a basic knowledge of V. vulnificus infection. Education for both physicians and people in the high-risk group for developing the infection (e.g. immunocompromised, chronic liver disease) will be necessary for the prevention, early diagnosis and appropriate treatment of the disease.
Y. Maeda, Dept. of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park PA 16802-6305, U.S.A.,
G. Garmire, Dept. of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park PA 16802-6305, U.S.A.,
K. Koyama, Department of Physics, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan; CREST, Japan Science and Technology Corporation (JST), 4-1-8 Honmachi, Kawaguchi, Saitama 332-0012, Japan,
M. Sakano, Department of Physics, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
We present preliminary results of our ASCA observation of the Galactic bulge. We confirm the diffuse (spatially-unresolved) soft X-ray emission in the direction of the bulge. We also detect iron-L and neon-K complex lines in the spectrum. Therefore, the bulge emission undoubtedly originates from an optically thin thermal plasma. The plasma temperature is 0.4 keV. With the results, we present possible implications of the Galactic bulge emission.
A Galactic Soft X-ray Diffuse Background (SXDB) below ∼2 keV was discovered by Bowyer, Field & Mack (1968). Four soft X-ray all-sky surveys produced maps of this SXDB (McCammon et al. 1983; Marshall & Clark 1984; Garmire et al. 1992; Snowden et al. 1995, 1997) which show complex features, indicating that the SXDB must be made up of several components. However, Snowden et al. (1997) established that the SXDB maps above 0.5 keV are smooth on the south side of the plane, which can be reproduced with only one component: a hot gas in the bulge with a scale height of ∼1.9 kpc. Thus they named this component as the ‘bulge’ emission. The typical temperature was estimated to be ∼0.3 keV.
The ASCA satellite has the capability to observe the SXDB with a reasonable energy resolution (Tanaka et al. 1994), which allows an improved study of line emission. We present here results of our initial analysis of the ASCA spectrum and discuss the bulge emission.