TY - JOUR
T1 - The XMM-Newton view of NGC 6251
AU - Gliozzi, M.
AU - Sambruna, R. M.
AU - Brandt, W. N.
AU - Mushotzky, R.
AU - Eracleous, M.
N1 - Copyright:
Copyright 2008 Elsevier B.V., All rights reserved.
PY - 2004/1
Y1 - 2004/1
N2 - We report on the nuclear X-ray properties of the radio galaxy NGC 6251 observed with XMM-Newton. NGC 6251 is a well-known radio galaxy with intermediate FRI/II radio properties. It is optically classified as a Seyfert 2 and hosts a supermassive black hole with mass ∼6 × 108 ME. The 0.4-10 keV EPIC pn continuum is best fitted by two thermal components (kT ∼ 0.5 and 1.4 keV, respectively), plus a power law with photon index Γ ∼ 1.9 absorbed by a column density NH ∼ 5 × 1020 cm-2. We confirm the previous ASCA detection of a strong iron line. The line, resolved in the EPIC pn spectrum, is adequately fitted with a broad (σ ∼ 0.6 keV) Gaussian at rest-frame energy 6.4 keV with EW ∼ 220 eV. We also detect, for the first time, short-term, low-amplitude variability of the nuclear flux on a timescale of a few ks. The spectral properties argue in favor of the presence of a standard accretion disk, ruling out the base of the jet as the sole origin of the X-rays. The moderate X-ray luminosity and lack of strong intrinsic absorption suggest that NGC 6251 is a "pure" type 2 AGN which lacks a broad-line region.
AB - We report on the nuclear X-ray properties of the radio galaxy NGC 6251 observed with XMM-Newton. NGC 6251 is a well-known radio galaxy with intermediate FRI/II radio properties. It is optically classified as a Seyfert 2 and hosts a supermassive black hole with mass ∼6 × 108 ME. The 0.4-10 keV EPIC pn continuum is best fitted by two thermal components (kT ∼ 0.5 and 1.4 keV, respectively), plus a power law with photon index Γ ∼ 1.9 absorbed by a column density NH ∼ 5 × 1020 cm-2. We confirm the previous ASCA detection of a strong iron line. The line, resolved in the EPIC pn spectrum, is adequately fitted with a broad (σ ∼ 0.6 keV) Gaussian at rest-frame energy 6.4 keV with EW ∼ 220 eV. We also detect, for the first time, short-term, low-amplitude variability of the nuclear flux on a timescale of a few ks. The spectral properties argue in favor of the presence of a standard accretion disk, ruling out the base of the jet as the sole origin of the X-rays. The moderate X-ray luminosity and lack of strong intrinsic absorption suggest that NGC 6251 is a "pure" type 2 AGN which lacks a broad-line region.
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U2 - 10.1051/0004-6361:20034053
DO - 10.1051/0004-6361:20034053
M3 - Article
AN - SCOPUS:0348170679
SN - 0004-6361
VL - 413
SP - 139
EP - 144
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
IS - 1
ER -