Measuring the Coronal Properties of IC 4329A with NuSTAR

Creators: Brenneman, L. W.; Madejski, G.; Fuerst, F.; Matt, G.; Elvis, M.; Harrison, F. A.; Ballantyne, D. R.; Boggs, S. E.; Christensen, F. E.; Craig, W. W.; Fabian, A. C.; Grefenstette, B. W.; Hailey, C. J.; Madsen, K. K.; Marinucci, A.; Rivers, E.; Stern, D.; Walton, D. J.; Zhang, W. W.

Abstract

We present an analysis of a ~160 ks NuSTAR observation of the nearby bright Seyfert galaxy IC 4329A. The high-quality broadband spectrum enables us to separate the effects of distant reflection from the direct coronal continuum, and to therefore accurately measure the high-energy cutoff to be E_(cut)=178^(+74)_(-40) keV. The coronal emission arises from accretion disk photons Compton up-scattered by a thermal plasma, with the spectral index and cutoff being due to a combination of the finite plasma temperature and optical depth. Applying standard Comptonization models, we measure both physical properties independently using the best signal to noise obtained to date in an active galactic nucleus over the 3-79 keV band. We derive kT_e=37^(+7)_(-6) keV with τ =1.25^(+0.20)_(-0.10) assuming a slab geometry for the plasma, and kT_e=33^(+6)_(-6)keV with τ = 3.41^(+0.58)_(-0.38) for a spherical geometry, with both having an equivalent goodness-of-fit.

Additional Information

© 2014 American Astronomical Society. Received 2013 October 18; accepted 2013 December 11; published 2014 January 13. This work was supported under NASA Contract No. NNG08FD60C, and 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. We thank the NuSTAR Operations, Software and Calibration teams for support with the execution and analysis of these observations. 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). L.B. gratefully acknowledges funding from NASA grant NNX13AE90G. G.M. and A.M. acknowledge financial support from the Italian Space Agency under contract ASI/INAF I/037/12/0-011/13.

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