NuSTAR observations of Mrk 766: distinguishing reflection from absorption

Creators: Buisson, D. J. K.; Parker, M. L.; Kara, E.; Vasudevan, R. V.; Lohfink, A. M.; Pinto, C.; Fabian, A. C.; Ballantyne, D. R.; Boggs, S. E.; Christensen, F. E.; Craig, W. W.; Farrah, D.; Hailey, C. J.; Harrison, F. A.; Ricci, C.; Stern, D.; Walton, D. J.; Zhang, W. W.

Abstract

We present two new NuSTAR observations of the narrow-line Seyfert 1 (NLS1) galaxy Mrk 766 and give constraints on the two scenarios previously proposed to explain its spectrum and that of other NLS1s: relativistic reflection and partial covering. The NuSTAR spectra show a strong hard (>15 keV) X-ray excess, while simultaneous soft X-ray coverage of one of the observations provided by XMM–Newton constrains the ionized absorption in the source. The pure reflection model requires a black hole of high spin (a > 0.92) viewed at a moderate inclination (⁠i=46^(+1)_(−4)∘⁠). The pure partial covering model requires extreme parameters: the cut-off of the primary continuum is very low (⁠22^(+7)_(−5) keV) in one observation and the intrinsic X-ray emission must provide a large fraction (75 per cent) of the bolometric luminosity. Allowing a hybrid model with both partial covering and reflection provides more reasonable absorption parameters and relaxes the constraints on reflection parameters. The fractional variability reduces around the iron K band and at high energies including the Compton hump, suggesting that the reflected emission is less variable than the continuum.

Additional Information

© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model) Accepted 2018 July 30. Received 2018 July 27; in original form 2017 May 23. DJKB, MLP, and RVV acknowledge financial support from the Science and Technology Facilities Council (STFC). ACF, AML, CP, and MLP acknowledge support from the ERC Advanced Grant FEEDBACK 340442. This work made use of data from the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by the National Aeronautics and Space Administration. This research has made use of the NuSTAR Data Analysis Software (NuSTARDAS) jointly developed by the ASI Science Data Center (ASDC, Italy) and the California Institute of Technology (USA). This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. This work has made use of observations obtained with XMM–Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA. We acknowledge support from the Faculty of the European Space Astronomy Centre (ESAC).

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