ASCA Observation of the Lyman-limit Quasar PKS2145+067
N. Y. Yamasaki, T. Ishikawa, T. Ohashi
Abstract
X-ray observation of a famous Lyman-limit quasar PKS2145+067at zem= 0.990 was carried with ASCA. The source showed a 2-10 keV flux of 1.3 E-11 erg cm-2 sec-1 (LX = 2.5 E46 erg sec-1 for H0=50 km s-1 Mpc-1) described by a power-law spectrum with a photon index Gamma=1.63 +/- 0.04 . In the ASCA energy band, no excess absorption was detected implying the absorption column density at z ab=0.791 was less than 1.6 E21 cm-2 if absorbing medium had a metal abundance of 0.5 solar. Comparison with previous Einstein and ROSAT observations shows that PKS2145+067 has increased its luminosity by a factor of 2--3 between 1991 and 1998.
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