X-RAY-SPECTRUM AND VARIABILITY OF THE QUASAR PG 1211+143

We present preliminary results of an ASCA observation of the classic s oft-excess quasar PG 1211+143. The overall ASCA spectrum can be charac terized by a blackbody with a temperature of approximately 125 eV (qua sar frame) and a power law with photon index approximately 2. Simultan eous ROSAT data are suggestive of further steepening of the spectrum j ust below the ASCA band. Comparison with previous observations shows t hat the soft flux in the 0.1-2 keV band varies by at least a factor of approximately, 16 scaling roughly as the square of the hard flux in t he 2-10 keV band over a timescale of approximately 13.5 yr. We also fi nd evidence of short-term amplitude variability of up to a factor appr oximately 2 on a timescale of approximately 2 x 10(4) s, in both the s oft and hard flux so that the soft and hard photons are likely to orig inate from the same, compact, region. The data rule out variable absor ption (cold or ionized) as the origin of the soft excess, favoring an intrinsic emission component. However, we argue against optically thin emission for the 'blue bump' in PG 1211+143. The large amplitude soft X-ray variability may be indicative of variations in the effective te mperature, or peak, of the soft component. There is only marginal evid ence for Fe K line emission between 6-7 keV in the quasar frame.