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R.M. Sambruna, M. Eracleous (Penn State University), R.F. Mushotzky (NASA/GSFC)
We present a systematic X-ray spectral survey with ASCA of a sample of radio-loud AGN, including 9 Broad Line Radio Galaxies (BLRGs), 6 Quasars (QSRs), 12 Narrow Line Radio Galaxies (NLRGs), and 11 Radio Galaxies (RGs). At soft X-rays, 50% NLRGs and 100% RGs exhibit a thermal component, indicating emission from either a cluster or a loose group or hot corona. At energies > 2 keV, a hard power-law is detected, with similar slopes (photon index \Gamma ~ 1.7) and luminosities in BLRGs, QSRs, and NLRGs, consistent with simple orientation-based unification schemes. Excess cold absorption in the range 1021-24~cm-2 is detected in most NLRGs, most likely due to an obscuring torus. Absorption edges of ionized oxygen, common in Seyfert 1s, are detected in only one BLRG. Instead large columns of cold gas, comparable to NLRGs, are detected in a fraction of BLRGs and QSRs, which is puzzling. The nuclear X-ray luminosity is non-linearly correlated with the [OIII] emission line luminosity, the FIR 12~\mum emission, and 5 GHz lobe radio power. The Fe K\alpha line is detected in 50% BLRGs and one QSR, with a large range of intrinsic widths and equivalent widths, while it is unresolved in NLRGs. There is only a weak indication that the ASCA spectra of BLRGs are flatter than Seyfert 1s of comparable X-ray luminosity, contrary to previous evidence.
The sample includes 6 Weak Line Radio Galaxies (WLRGs), characterized by underluminous [OIII] lines and unusually high [OII]/[OIII] ratios. Their ASCA spectra are consistent at hard energies with a hard (\Gamma ~1.5) power law, with intrinsic luminosities 100 times lower than in other RGs. If the hard X-ray emission is attributed to a low-luminosity AGN, an interesting possibility is that WLRGs are accreting at strongly sub-Eddington rates. This work is supported by NASA contract NAS-38252 and NASA grant NAG5-7733
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