S. Takano

GINGA observations of three X-ray-luminous early-type galaxies : NGC 4472, NGC 4636, and NGC 3998

Observations of three X-ray luminous early-type galaxies, NGC 4472, NGC 4636 and NGC 3998, with the satellite Ginga, are presented. The X-ray spectra of NGC 4472 and NGC 4636 can be described as thermal emission from an optically thin plasma. The temperatures of the hot gas are determined. The X-ray spectrum of NGC 3998 is well fitted by a power-law model having a photon index of 2.0, the same sort of spectrum typical of AGN.

X-RAY CONTINUUM AND EVIDENCE FOR AN IRON EMISSION-LINE FROM THE QUASAR E1821 + 643

This paper reports on the 2-10 keV spectrum of the quasar E1821 + 643, obtained with the large-area proportional counters aboard the Ginga spacecraft on two occasions: May 12-14, 1987 and September 27, 1988. The spectrum shows strong evidence for the presence of a redshifted iron K emission line of a 5.1 + or - 0.2 keV energy, and an observed equivalent width of 210 + or - 80 eV. The E1821 + 643 appeared to be embedded within a cluster of galaxies which could contribute part of the observed line. A possibility is suggested that iron emission lines may be a common feature in X-ray spectra of quasars. 41 refs.

An X-ray pulsator in the direction of molecular cloud MBM 12 (Lynds 1457)

Multiwave observations have been conducted near the central region of a molecular cloud MBM 12 and a peculiar X-ray source HO253 + 193. An IR object with a K-magnitude of about 13.5 was discovered within the error circle of X-ray source HO253 + 193. In the X-ray band, a coherent 206 s pulsation from HO253 + 193 was found. X-ray spectrum of HO253 + 193 was very similar to that of a cataclysmic variable with a strong magnetic field. With fine CO mapping observation near HO253 + 193, it was found that the position of HO253 + 193 (or the new IR source) is slightly off-center from the intensity peak of the molecular cloud. 21 refs.