Volume 410, Number 1, October IV 2003
|Page(s)||131 - 138|
|Published online||17 November 2003|
The hard X-ray view of the low-luminosity blazar in the radio galaxy NGC 6251
XMM-Newton Science Operations Center, VILSPA, ESA, Apartado 50727, 28080 Madrid, Spain e-mail: firstname.lastname@example.org
2 Istituto di Astrofisica Spaziale e Fisica Cosmica (IASF-C.N.R.), Sezione di Bologna, via Gobetti 101, 40129 Bologna, Italy
3 I.N.A.F., Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
4 Dipartimento di Fisica, Università degli Studi “Roma Tre”, via della Vasca Navale 84, 00146 Roma, Italy
Corresponding author: M. Guainazzi, email@example.com
Accepted: 31 July 2003
We present results from a BeppoSAX (July 2001) observation of the FR I radio galaxy NGC 6251, together with a re-analysis of archival ASCA (October 1994) and Chandra (September 2000) data. The weak detection above 10 keV and the lack of iron fluorescent Kα emission lines in the BeppoSAX spectrum rule out that the bulk of the X-ray emission is due to an obscured Seyfert nucleus. The study of the multiwavelength spectral energy distribution suggests instead that X-rays probably originate as inverse-Compton of synchrotron seed photons in a relativistic jet, indicating that NGC 6251 hosts a low radio luminosity ( erg s-1) blazar. The BeppoSAX spectrum is flatter than in the earlier ASCA observation. This might be due to the emergence of a different spectral component during phases of lower X-ray flux. In this context, we discuss some possible explanations for the intense and mildly-ionized fluorescent iron line measured by ASCA.
Key words: galaxies: active / galaxies: individual: NGC 6251 / galaxies: jets / galaxies: nuclei / X-rays: galaxies
© ESO, 2003
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