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IC 751: A New Changing Look AGN Discovered by NuSTARWe present results of five Nuclear Spectroscopic Telescope Array (NuSTAR) observations of the type 2 active galactic nucleus (AGN) in IC 751, three of which were performed simultaneously with XMM-Newton or Swift/ X-Ray Telescope. We find that the nuclear X-ray source underwent a clear transition from a Compton-thick (NH approx. = 2 x10(exp 24)/sq cm) to a Compton-thin ( N(sub H) approx. = 4 x10(exp 23)/sq cm) state on timescales of < or approx.3 months, which makes IC 751 the first changing look AGN discovered by NuSTAR. Changes of the line of sight column density at the approx.2 (sigma) level are also found on a timescale of approx. 48 hr (delta N(sub H approx. 10(exp 23)/sq cm). From the lack of spectral variability on timescales of approx.100 ks, we infer that the varying absorber is located beyond the emission-weighted average radius of the broad-line region (BLR), and could therefore be related either to the external part of the BLR or a clumpy molecular torus. By adopting a physical torus X-ray spectral model, we are able to disentangle the column density of the non-varying absorber (N(sub H) approx. 3.8 x10(exp 23)/sq cm) from that of the varying clouds [N(sub H) approx. (1- 150) x 10(exp 22)/sq cm], and to constrain that of the material responsible for the reprocessed X-ray radiation (N(sub H approx. 6 x 10(exp 24)/sq cm).24 -2). We find evidence of significant intrinsic X-ray variability, with the flux varying by a factor of five on timescales of a few months in the 2-10 and 10-50 keV band.
Document ID
Document Type
Reprint (Version printed in journal)
Ricci, C.
(Catholic Univ. Santiago, Chile)
Bauer, F. E.
(Space Science Inst. Boulder, CO, United States)
Arevalo, P.
(Universidad Catolica de Valparaiso Valparaiso, Chile)
Boggs, S.
(California Univ. Berkeley, CA, United States)
Brandt, W. N.
(Pennsylvania State Univ. University Park, PA, United States)
Christensen, F. E.
(Technical Univ. of Denmark Lyngby, Denmark)
Craig, W. W.
(California Univ. Berkeley, CA, United States)
Ghandi, P.
(Southampton Univ. Highfield, United Kingdom)
Hailey, C. J.
(Columbia Univ. New York, NY, United States)
Harrison, F. A.
(California Inst. of Tech. Pasadena, CA, United States)
Koss, M.
(Eidgenoessische Technische Hochschule Zurich, Switzerland)
Markwardt, C. B.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Stern, D.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Treister, E.
(Universidad de Concepcion Chile)
Zhang, W. W.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Date Acquired
March 29, 2017
Publication Date
March 10, 2016
Publication Information
Publication: The Astrophysical Journal
Volume: 820
Issue: 1
ISSN: 2041-8205
Subject Category
Report/Patent Number
Distribution Limits
indivdual: Seyfert
galaxies: active

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