Abstract

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.

Original languageEnglish (US)
Pages (from-to)139-144
Number of pages6
JournalAstronomy and Astrophysics
Volume413
Issue number1
DOIs
StatePublished - Jan 1 2004

Fingerprint

XMM-Newton telescope
newton
radio galaxies
radio
x rays
accretion disks
power law
accretion
luminosity
continuums
timescale
iron
photons
energy

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Gliozzi, M. ; Sambruna, R. M. ; Brandt, William Nielsen ; Mushotzky, R. ; Eracleous, Michael. / The XMM-Newton view of NGC 6251. In: Astronomy and Astrophysics. 2004 ; Vol. 413, No. 1. pp. 139-144.
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The XMM-Newton view of NGC 6251. / Gliozzi, M.; Sambruna, R. M.; Brandt, William Nielsen; Mushotzky, R.; Eracleous, Michael.

In: Astronomy and Astrophysics, Vol. 413, No. 1, 01.01.2004, p. 139-144.

Research output: Contribution to journalArticle

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T1 - The XMM-Newton view of NGC 6251

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AU - Sambruna, R. M.

AU - Brandt, William Nielsen

AU - Mushotzky, R.

AU - Eracleous, Michael

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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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