Persistence and change in the soft X-ray spectrum of the quasar PG 1211 + 143
Citation
Elvis, Martin, Belinda J. Wilkes, P. Giommi, and Jonathan McDowell. 1991. “Persistence and Change in the Soft X-Ray Spectrum of the Quasar PG 1211 + 143.” The Astrophysical Journal 378 (September): 537. doi:10.1086/170454.Abstract
The present study examines two Einstein and three Exosat observations of PG 1211 + 143 over a 6-yr baseline which show that strong steep-spectrum low-energy X-ray emission is a persistent feature of this quasar. Exosat observations of PG 1211 + 143 detected an increase of a factor of 2.3 in its steep soft X-ray flux during 18 days. It is concluded that the bulk of the soft X-ray emission of PG 1211 + 143 comes from a region less than 5 x 10 to the 16th cm across. In another interval of 193 days, the soft X-rays decreased by a factor of 3.7. In the same interval the hard X-rays decreased by a factor of 1.6 + or - 0.05, which suggests a connection between the two energy regimes and argues against variable absorption causing the soft X-ray variations. It is contended that in order to decrease in luminosity so rapidly, a thermal source in PG 1211 + 143 would have to be optically thick to both electron scattering and free-bound absorption.Terms of Use
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