[en] Observation of CenX-3 by 'Hakucho' was performed. The observed shape of X-ray pulses has a hump at a decay part. The delay Doppler treatment was made as the pulse analysis. The best fit orbital parameters were obtained. The variation of X-ray pulse period is shown in a figure. It was found that simple spin-up tendency was not seen. The observed luminosity of CenX-3 was deduced. There was no correlation between the luminosity and the spin-up rate. The variation of orbital period was observed in the data from 1973 to 1981. (Kato, T.)

[en] A new method of soft X-ray spectroscopy is proposed to observe line X-ray emitted from galactic hot plasma. This method is low dispersive but it has higher efficiency than a grating. The principle of this method is to measure accurately photoelectrons produced by incident X-ray. Incident X-ray energy is uniquely determined from the measurement of the photoelectron energy. Since photoelectrons are scattered from various processes, the determination of their energy is difficult. The extent of the loss of initial information on their energy is investigated by the Monte 0.8 predicted in 10⁶ deg. K hot plasma enters Be and C targets, the behavior of low energy electrons is simulated. Further, the energy spectrum of galactic X-ray simulated by this method is presented. (J.P.N.)

[en] The recurrent X-ray burster 1608-522 was observed by HAKUCHO from April 20 to May 9, 1980, and twelve burst events were analyzed. The emitting energy ratio of burst X-ray to steady X-ray (α-value) was less than 26. In order to explain α < 26, it must be considered that this burster is a star with extremely small mass or large radius. The correlation between the peak intensity and the integrated counts of burst X-ray was different from that observed in 1979. This variation of the burst condition is interesting. The double peak structure was observed in the range from 9 to 22 keV in two burst events. It has not been known what condition caused the double peak structure. (Yoshimori, M.)

No abstract available

[en] The Gamma-ray Burst Detector (GBD) on the 'Ginga' satellite observed spectral structures in two gamma-ray bursts. One of them which occurred on February 5, 1988 shows clear two absorption lines. For this event, the probability that these lines are due to mere statistical fluctuation is estimated at 8 x 10^-5. These two absorption lines show harmonic structure which can be interpreted as a fundamental and its second harmonic due to cyclotron scattering in a relatively cool magnetized plasma with a super strong field of about 2 x 10¹²G. This observation, therefore, may strongly support the hypothesis that highly magnetized neutron stars are the origin of gamma-ray bursts. In addition, the narrowness of the two lines sets upper limits on the electron kinetic temperature parallel to the magnetic field of a few keV, and also on the size of the absorbing region; 0.1 of a neutron star surface in area and 0.15 of the neutron star radius in thickness. These results suggest that the absorbing region is not a part of the gamma-ray emission region where the continuum radiation is produced. (author)

[en] The polypropylene membrane of 1μm thick was developed, and it is widely used as the window material for the proportional counters for the detection of soft X-ray. Several observations of cosmic soft X-ray have been performed, and the energy spectra of diffuse soft X-ray and the spatial distribution have been measured. The observed results showed that the intensity of soft X-ray was much higher than that extrapolated from the energy spectra of the diffuse component measured above 1 keV. The proportional counter system of 660 cm² area and the 2.8 deg x 11 deg (FWHN) field of view was used for the detection of 0.1-1.5 keV soft X-ray. The K-9M-44 rocket was launched on Aug. 27, 1973, and the energy spectra of diffuse soft X-ray were measured. The result showed that the energy spectra outside. Radio Loop I was different from that inside it, the soft X-ray intensities from the galactic north pole and the HI hole region were higher than those from other regions, and the energy spectra were enhanced near 0.5-0.8 keV in North Polar Spur and Lupus Loop regions. The X-ray emission model was suggested for the explanation of the energy spectra outside Radio Loop I. (Yoshimori, M.)

[en] The 13.9-min pulsating x-ray source 4U 0352 + 30-X Per was observed by the Tenma satellite. A pulse period of 13.933 ± 0.002 min, after heliocentric correction, was observed on JD 2,446,016 in 1984. This pulse period is the longest observed to date. The fluctuation of the pulse period looks similar to those of pulsars such as Vela X-1 and GX 301 - 2, and the rate of change of the pulse period can be explained only if the rotating body is a neutron star. However, the observed luminosity may be too low to explain the observed period derivative by present theories. (author)

[en] Gamma-ray Burst Detector System (GBD) on board the scientific satellite 'GINGA' which was launched on Feb. 5, 1987, was realized as an international cooperation between ISAS and LANL. It has recorded more than 40 Gamma-Ray Burst candidates during 20 months observation. Although many observational evidences were accumulated in past 20 years after the discovery of gamma-ray burst by LANL scientists, there are not enough evidence to determine the origin and the production mechanism of the gamma-ray burst. GBD consists of a proportional counter and a NaI scintillation counter so that it became possible to observe energy spectrum of the gamma-ray burst with high energy resolution over wide range of energy (1.5-380 keV) together with high time resolution. As the result of observation, the following facts are obtained: (1) A large fraction of observed gamma-ray bursts has a long X-ray tail after the harder part of gamma-ray emission has terminated. (2) Clear spectral absorption features with harmonic in energy was observed in some of the energy spectrum of gamma-ray bursts. These evidences support the hypothesis that the strongly magnetized neutron star is the origin of gamma-ray burst. (author)

[en] The soft X-ray emission of gamma-ray bursts below 10 keV provides information about size, location, and emission mechanism. The Gamma-ray Burst Detector (GBD) on board Ginga, which consists of a proportional counter and a scintillation detector, covers an energy range down to 1.5 keV with 63 cm² effective area. In several of the observed gamma-ray bursts, the intensity of the soft X-ray emission showed a longer decay time of 50 to 100s after the higher energy gamma-ray emission had ended. Although we cannot rule out other models, such as bremsstrahlung and thermal cyclotron types, due to poor statistics, the soft X-ray spectra are consistent with a blackbody of 1 to 2 keV in the late phase of the gamma-ray bursts. This enables us to estimate the size of the blackbody responsible for the X-ray emission. (author)

[en] Two new X-ray burst sources XB1812-12 and XB1940-04 have been discovered in Serpens and in Aquila region, respectively, from Hakucho observations. The location of XB1812-12 coincides with that of 4U1812- 12/3A1812-121 which was once reported as the transient X-ray source Ser X-2 in 1965. In the error box of XB1940-04, there is no reported or cataloged X-ray source. Including XB1812-12,8 out of 27 X-ray burst sources have been identified with transient X-ray sources. The higher energy band from XB1812-12 exhibits a double-peaked profile. (author)