Other
Scientific paper
Sep 1991
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1991apj...378..537e&link_type=abstract
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 378, Sept. 10, 1991, p. 537-542.
Other
35
Quasars, Stellar Spectra, X Ray Sources, X Ray Spectra, Exosat Satellite, Optical Thickness, Satellite Observation
Scientific paper
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.
Elvis Martin
Giommi Paolo
McDowell Jonathan
Wilkes Belinda J.
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