The Equilibrium Photoionized Absorber in 3C351

Abstract

We present two ROSAT PSPC observations of the radio-loud, lobe-dominated quasar 3C 351, which shows an `ionized absorber' in its X-ray spectrum. The factor 1.7 change in flux in the $\sim$2~years between the observations allows a test of models for this ionized absorber. The absorption feature at ~0.7 keV (quasar frame) is present in both spectra but with a lower optical depth when the source intensity - and hence the ionizing flux at the absorber - is higher, in accordance with a simple, single-zone, equilibrium photoionization model. Detailed modeling confirms this agrement quantitatively. The maximum response time of 2 years allows us to limit the gas density: n_e > 2 x 10^4 cm^{-3}; and the distance of the ionized gas from the central source R < 19 pc. This produces a strong test for a photoionized absorber in 3C~351: a factor 2 flux change in ~1 week in this source must show non-equilibrium effects in the ionized absorber.

10 pages, 3 figures, accepted by ApJ

References in corpus (5)

• An X-ray spectral study of 24 type-1 AGN
• A multi-wavelength study of the Seyfert 1 galaxy MCG-6-30-15
• The variability properties of X-ray steep and X-ray flat quasars
• X-ray absorption by ionized oxygen in ASCA spectra of the infrared quasar IRAS 13349+2438
• The Optical Polarization and Warm Absorber in IRAS 17020+4544

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