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3C 273 with NuSTAR: Unveiling the Active Galactic Nucleus

Madsen, Kristin K. and Fürst, Felix and Walton, Dominic J. and Harrison, Fiona A. and Nalewajko, Krzysztof and Ballantyne, David R. and Boggs, Steve E. and Brenneman, Laura W. and Christensen, Finn E. and Craig, William W. and Fabian, Andrew C. and Forster, Karl and Grefenstette, Brian W. and Guainazzi, Matteo and Hailey, Charles J. and Madejski, Greg M. and Matt, Giorgio and Stern, Daniel and Walter, Roland and Zhang, William W. (2015) 3C 273 with NuSTAR: Unveiling the Active Galactic Nucleus. Astrophysical Journal, 812 (1). Art. No. 14. ISSN 0004-637X. doi:10.1088/0004-637X/812/1/14.

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We present results from a 244 ks NuSTAR observation of 3C 273 obtained during a cross-calibration campaign with the Chandra, INTEGRAL, Suzaku, Swift, and XMM-Newton observatories. We show that the spectrum, when fit with a power-law model using data from all observatories except INTEGRAL over the 1–78 keV band, leaves significant residuals in the NuSTAR data between 30 and 78 keV. The NuSTAR 3–78 keV spectrum is well described by an exponentially cutoff power law (Γ = 1.646 ± 0.006, E_(cutoff) = 202_(-34)^(+51) keV) with a weak reflection component from cold, dense material. There is also evidence for a weak (EW = 23 ± 11 eV) neutral iron line. We interpret these features as arising from coronal emission plus reflection off an accretion disk or distant material. Beyond 80 keV INTEGRAL data show clear excess flux relative to an extrapolation of the active galactic nucleus model fit to NuSTAR. This high-energy power law is consistent with the presence of a beamed jet, which begins to dominate over emission from the inner accretion flow at 30–40 keV. Modeling the jet locally (in the NuSTAR + INTEGRAL band) as a power law, we find that the coronal component is fit by Γ_(AGN) = 1.638 ± 0.045, E_(cutoff) = 47 ± 15 keV, and jet photon index by Γ_(jet) = 1.05 ± 0.4. We also consider Fermi/LAT observations of 3C 273, and here the broadband spectrum of the jet can be described by a log-parabolic model, peaking at ~2 MeV. Finally, we investigate the spectral variability in the NuSTAR band and find an inverse correlation between flux and Γ.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Madsen, Kristin K.0000-0003-1252-4891
Fürst, Felix0000-0003-0388-0560
Walton, Dominic J.0000-0001-5819-3552
Harrison, Fiona A.0000-0003-2992-8024
Ballantyne, David R.0000-0001-8128-6976
Boggs, Steve E.0000-0001-9567-4224
Christensen, Finn E.0000-0001-5679-1946
Fabian, Andrew C.0000-0002-9378-4072
Forster, Karl0000-0001-5800-5531
Grefenstette, Brian W.0000-0002-1984-2932
Matt, Giorgio0000-0002-2152-0916
Stern, Daniel0000-0003-2686-9241
Zhang, William W.0000-0002-1426-9698
Alternate Title:3C 273 with NuSTAR: Unveiling the AGN
Additional Information:© 2015. The American Astronomical Society. Received 2015 June 16; accepted 2015 August 26; published 2015 October 5. We thank Chris Done for bringing to our attention the alternative interpretation of the jet as a two-component inverse Compton model, and the anonymous referee, whose remarks and corrections helped improve the quality of this paper. 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). Facilities: Fermi - Fermi Gamma-Ray Space Telescope (formerly GLAST), Chandra (CXO) - , INTEGRAL - International Gamma-Ray Astrophysics Laboratory satellite, NuSTAR - The NuSTAR (Nuclear Spectroscopic Telescope Array) mission, Suzaku - Suzaku (ASTRO-EII), Swift - Swift Gamma-Ray Burst Mission, and XMM - Newton X-Ray Multimirror Mission satellite.
Group:NuSTAR, Space Radiation Laboratory
Funding AgencyGrant Number
Subject Keywords:quasars: individual (3C 273) - X-rays: individual (3C 273)
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory2015-27
Issue or Number:1
Record Number:CaltechAUTHORS:20151015-090448563
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:61139
Deposited By: Tony Diaz
Deposited On:15 Oct 2015 17:22
Last Modified:10 Nov 2021 22:44

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