Disclosing the true nature of the Sy 2 galaxy NGC 3281: One more Compton-thick source

Free access article

Issue		A&A Volume 381, Number 3, January III 2002


Page(s)		834 - 840
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:20011527

A&A 381, 834-840 (2002)
DOI: 10.1051/0004-6361:20011527

Disclosing the true nature of the Sy 2 galaxy NGC 3281: One more Compton-thick source

C. Vignali and A. Comastri

Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy

(Received 31 August 2001 / Accepted 29 October 2001 )

Abstract
We present the BeppoSAX broad-band X-ray spectrum of the Seyfert 2 galaxy NGC 3281. The source high-energy spectrum is characterized by the nuclear transmitted component, with an absorbing column density of $\approx$ 2 $\times$ 10 ²⁴ cm ^-2, while the MECS spectrum is reflection-dominated, with a prominent ( $EW\approx0.5$ -1.2 keV) iron K ${\alpha}$ emission line. The source is detected at only the 5 $\sigma$ significance level in the LECS band, because of the strong obscuration which hampers at low energies the direct view of the active nucleus harbored in NGC 3281. BeppoSAX results are consistent with the scenario where NGC 3281 is inclined more than 60 $^{\circ}$ with respect to the line-of-sight. Combining the $N_{\rm H}$ value obtained from the present X-ray analysis with the $A_{\rm V}$ measurement, a $N_{\rm H}/A_{\rm V}$ about 50 times the Galactic value is derived.

Key words: galaxies: Seyferts: individual: NGC 3281 -- galaxies: nuclei -- galaxies: active -- X-rays: galaxies

Offprint request: C. Vignali, chris@astro.psu.edu

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