Evidence for orbital motion of material close to the central black hole of Mrk 766

Free access article

Issue		A&A Volume 445, Number 1, January I 2006


Page(s)		59 - 67
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:20053042

A&A 445, 59-67 (2006)
DOI: 10.1051/0004-6361:20053042

Evidence for orbital motion of material close to the central black hole of Mrk 766

T. J. Turner^{1, 2}, L. Miller³, I. M. George^{1, 2} and J. N. Reeves^{2, 4}

¹ Dept. of Physics, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA
e-mail: turner@milkyway.gsfc.nasa.gov
² Code 662, Exploration of the Universe Division, NASA/GSFC, Greenbelt, MD 20771, USA
³ Dept. of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
⁴ Dept. of Physics and Astronomy, Johns Hopkins University, 3400 N Charles Street, Baltimore, MD 21218, USA

(Received 10 March 2005 / Accepted 24 June 2005 )

Abstract
Time-resolved X-ray spectroscopy has been obtained for the narrow line Seyfert galaxy Mrk 766 from XMM-Newton observations. We present analysis in the energy-time plane of EPIC pn data in the 4-8 keV band with energy resolution $R \simeq 50$ . A component of Fe K $\alpha$ emission detected in the maps shows a variation of photon energy with time that appears both to be statistically significant and to be consistent with sinusoidal variation. We investigate the interpretation that there exists a component of line emission from matter in a Keplerian orbit around a supermassive black hole. The orbit has a period ~165 ks and a line-of-sight velocity ~ $13\,500$ km s^-1. This yields a lower limit for the central mass of $M > 4.9 \times 10^{5}~M_{\odot}$ within a radius of $3.6 \times 10^{13}$ cm (2.4 AU). The orbit parameters are consistent with higher black hole masses, but the lack of any substantial gravitational redshift of the orbit implies an upper limit to the black hole mass of $4.5 \times 10^{7}\,M_{\odot}$ .

Key words: galaxies: active -- X-rays: individual: Mrk 766 -- accretion, accretion disks

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