Takayoshi Kohmura

Metal-Rich Plasma at the Center Portion of the Cygnus Loop

We observed the center portion of the Cygnus Loop supernova remnant with the ASCA observatory. The X-ray spectrum of the center portion was significantly different from that obtained at the North-East (NE) limb. The emission lines from Si and S were quite strong while those of O and the continuum emission were similar to those obtained at the NE limb. Based on the spectral analysis, Si and S emission lines originated from a high-kTe and low ionization plasma whereas O and most of the continuum emission arose from a low-kTe and high ionization plasma. We suppose that Si and S emitting gas are present at the interior of the Loop while O lines and continuum emission mainly arise from the shell region. Therefore, we subtracted the spectrum of the NE limb from that of the center. Obtained abundances of Si, S, and Fe were 4

Discovery of a 220 Second X-Ray Pulsar, AX J1749.2–2725

pm

Measurement of quantum efficiency of a charge coupled device

1, 6

Discovery of 715 Second Pulsations from the Faint X-Ray Source AX J170006–4157

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Development and Evaluation of Event-Driven SOI Pixel Detector for X-ray Astronomy

2, and

Soft x-ray response of the prototype CCD camera (XIS) for Astro-E

{1.3}^{+0.6}_{-0.3}

ASCA Identification of SMC X-2 with the 2.37-s Pulsar Discovered by RXTE

times higher than those of the cosmic abundances, respectively, and are

X-ray imaging spectrometers for Astro-E: ground calibration in the soft x-ray range

sim

Delayed Iron Lines in Centaurus X-3

40 times richer than those obtained at the NE limb. These facts strongly support that some of the crude ejecta must be left at the center portion of the Cygnus Loop. The low abundance of Fe relative to Si and S suggests a type II SN with a massive progenitor star as the origin of the Cygnus Loop.

Soft X-ray response of a CCD with a grating spectrometer

We report here the discovery of a faint 220 s X-ray pulsar, AX J1749.2-2725, with ASCA. In the analysis, we used a method that can detect a pulsating source in a field of view contaminated by stray light. The source was observed on four occasions between 1995 March and 1997 September. The observed source flux was ~3.0 × 10-11 ergs s-1 cm-2 (2-10 keV) in 1995 March and became an order of magnitude fainter during the 2.5 yr interval. We cannot rule out the possibility that AX J1749.2-2725 is a nearby (d 1.3 kpc) DQ Her-type white dwarf binary, while the hard X-ray spectrum and the transient behavior suggest that it is a distant (d ~ 8.5 kpc) binary system containing a neutron star.