Astronomy and Astrophysics – Astronomy
Scientific paper
Nov 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000stin...0021229f&link_type=abstract
Technical Report, Smithsonian Astrophysical Observatory Cambridge, MA United States
Astronomy and Astrophysics
Astronomy
X Ray Astronomy, X Ray Sources, Seyfert Galaxies, Active Galactic Nuclei, Quasars, Black Holes (Astronomy), Balmer Series, Emission Spectra, Line Spectra, Spectrum Analysis, Variability, Data Reduction
Scientific paper
Steep soft X-ray (0.1-2 keV) quasars share several unusual properties: narrow Balmer lines, strong Fe II emission, large and fast X-ray variability, and a rather steep 2-10 keV spectrum. These intriguing objects have been suggested to be the analogues of Galactic black hole candidates in the high, soft state. We present here results from ASCA observations for two of these quasars: NAB 0205 + 024 and PG 1244 + 026. Both objects show similar variations (factor of approximately 2 in 10 ks), despite a factor of approximately 10 difference in the 0.5-10 keV luminosity (7.3 x 1043 erg/s for PG 1244 + 026 and 6.4 x 1044 erg/s for NAB 0205 + 024, assuming isotropic emission, H0 = 50.0 and q0 = 0.0). The X-ray continuum of the two quasars flattens by 0.5-1 going from the 0.1-2 keV band towards higher energies, strengthening recent results on another half-dozen steep soft X-ray active galactic nuclei. PG 1244 + 026 shows a significant feature in the '1-keV' region, which can be described either as a broad emission line centered at 0.95 keV (quasar frame) or as edge or line absorption at 1.17 (1.22) keV. The line emission could be a result of reflection from a highly ionized accretion disc, in line with the view that steep soft X-ray quasars are emitting close to the Eddington luminosity. Photoelectric edge absorption or resonant line absorption could be produced by gas outflowing at a large velocity (0.3-0.6 c).
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