Redshift dependence of soft X-ray quasar spectra.

Details Redshift dependence of soft X-ray quasar spectra. Redshift dependence of soft X-ray quasar spectra.

Mar 1996

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996a%26a...307...33s&link_type=abstract

Astronomy and Astrophysics, v.307, p.33

Astronomy and Astrophysics

Astrophysics

47

X-Ray: Galaxies, Quasars: General

Scientific paper

The analysis of the X-ray spectra of a sample of 102 X-ray bright quasars observed with ROSAT during the all-sky survey confirmed for the soft (0.1-2.4)keV energy range that the power law photon indices of radio-loud and radio-quiet quasars differ significantly from each other: <{GAMMA}>_rl_=2.23+/-0.07 <{GAMMA}>_rq_=2.54+/-0.04. These mean indices are found to be significantly steeper than those determined for the harder (0.3-3.5)keV energy band of the Einstein Observatory/IPC and the medium energy (2-10...20)keV bands of the EXOSAT/ME and Ginga/LAC experiments for identical subsets of quasars. The comparison yielded a tendency of the harder the energy range covered by the experiment the flatter the average spectral indices. All but one of the 55 radio-quiet quasars in the present ROSAT sample cover a very limited redshift range (z<0.5). On the other hand, the 47 radio-loud quasars of the sample have redshifts up to z=2.5. For this subset we established a relation between the mean photon index in ROSAT's soft energy band and the redshift. This relation shows a remarkable drop of the spectral slope from <{GAMMA}>~2.2 for nearby quasars to <{GAMMA}>~1.5 for distant objects. This flattening of the mean quasar spectrum with increasing redshift may partly be caused by selection effects. A quantitative interpretation of the relation is, however, achieved by assuming a two-component continuum for the intrinsic mean quasar spectrum consisting of a medium energy power law spectrum and a steep soft excess component. As far as the spectral properties at very soft X-ray energies are concerned, radio-loud and radio-quiet quasars are indistinguishable. Normalized to the same soft excess component, the power law continua of radio-loud and radio-quiet quasar cross over at about 0.6keV. Beyond that photon energy the radio-loud quasars are appreciably X-ray brighter and spectrally flatter than their radio-quiet counterparts. The only difference between both species seems to be a difference in the medium energy spectral index.

Affiliated with

Also associated with

No associations

Rating

Redshift dependence of soft X-ray quasar spectra. does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Redshift dependence of soft X-ray quasar spectra., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Redshift dependence of soft X-ray quasar spectra. will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1642265