ASCA OBSERVATIONS OF 2 ULTRALUMINOUS IRAS GALAXIES - IRAS-15307-20460+1925(3252 AND IRAS)

We report on ASCA observations of two ultraluminous far-infrared galax ies, IRAS 15307+3252 and IRAS 20460+1925. an X-ray flux of 1.53x10(-12 ) erg cm(-2) s(-1) in the 2-10 keV band was detected from IRAS 20460+1 925. The continuous spectrum is well represented by a power law with a photon index of 1.99(-0.15)(+0.18) and excess photoelectric absorptio n by a column of (2.6(-0.23)(+0.29)x10(22)) cm(-2) in the rest frame. The spectrum also shows an iron K emission line with an equivalent wid th of 260(-137)(+145) eV and a centroid energy of 6.36+/-0.08 keV in t he rest frame. These spectral properties are consistent with those of Seyfert-2 galaxies, although the intrinsic 2-10 keV X-ray luminosity ( corrected for absorption) of 1.20x10(44) erg s(-1) is high and close t o that of quasars. No X-rays were detected from IRAS 15307+3252, and t he upper limit to the X-ray flux is 7.2x10(-14) erg cm(-2) s(-1) in th e 2-10 keV band. However, the upper limit on the ratio of the X-ray fl ux to the far-infrared flux is not inconsistent with a source containi ng a highly obscured quasar.