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NuSTAR and XMM-Newton Observations of the Extreme Ultraluminous X-Ray Source NGC 5907 ULX1: A Vanishing Act

Walton, D. J. and Harrison, F. A. and Bachetti, M. and Barret, D. and Boggs, S. E. and Christensen, F. E. and Craig, W. W. and Fuerst, F. and Grefenstette, B. W. and Hailey, C. J. and Madsen, K. K. and Middleton, M. J. and Rana, V. and Roberts, T. P. and Stern, D. and Sutton, A. D. and Webb, N. and Zhang, W. (2015) NuSTAR and XMM-Newton Observations of the Extreme Ultraluminous X-Ray Source NGC 5907 ULX1: A Vanishing Act. Astrophysical Journal, 799 (2). Art. No. 122. ISSN 0004-637X.

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We present results obtained from two broadband X-ray observations of the extreme ultraluminous X-ray source (ULX) NGC 5907 ULX1, known to have a peak X-ray luminosity of ~5 × 10^(40) erg s^(–1). These XMM-Newton and NuSTAR observations, separated by only ~4 days, revealed an extreme level of short-term flux variability. In the first epoch, NGC 5907 ULX1 was undetected by NuSTAR, and only weakly detected (if at all) with XMM-Newton, while in the second NGC 5907 ULX1 was clearly detected at high luminosity by both missions. This implies an increase in flux of ~2 orders of magnitude or more during this ~4 day window. We argue that this is likely due to a rapid rise in the mass accretion rate, rather than to a transition from an extremely obscured to an unobscured state. During the second epoch we observed the broadband 0.3-20.0 keV X-ray luminosity to be (1.55 ± 0.06) × 10^(40) erg s^(–1), similar to the majority of the archival X-ray observations. The broadband X-ray spectrum obtained from the second epoch is inconsistent with the low/hard accretion state observed in Galactic black hole binaries, but is well modeled with a simple accretion disk model incorporating the effects of photon advection. This strongly suggests that when bright, NGC 5907 ULX1 is a high-Eddington accretor.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Walton, D. J.0000-0001-5819-3552
Harrison, F. A.0000-0003-2992-8024
Bachetti, M.0000-0002-4576-9337
Boggs, S. E.0000-0001-9567-4224
Madsen, K. K.0000-0003-1252-4891
Rana, V.0000-0003-1703-8796
Stern, D.0000-0003-2686-9241
Additional Information:© 2015 American Astronomical Society. Received 2014 August 19; accepted 2014 November 21; published 2015 January 21. The authors would like to thank the reviewer for positive and useful feedback, which helped improve the manuscript, as well as Diego Altamarino for useful discussions. M.B. and D.B. acknowledge financial support from the French Space Agency (CNES). This research has made use of data obtained with the NuSTAR mission, a project led by the California Institute of Technology (Caltech), managed by the Jet Propulsion Laboratory (JPL) and funded by NASA, and has utilized the NuSTAR Data Analysis Software (NUSTARDAS) jointly developed by the ASI Science Data Center (ASDC, Italy) and Caltech (USA). This research has also made use of data obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA, and NASA’s Chandra and Swift satellites. Facilites: NuSTAR, XMM, Chandra, Swift
Group:NuSTAR, Space Radiation Laboratory
Funding AgencyGrant Number
Centre National d'Études Spatiales (CNES)UNSPECIFIED
Subject Keywords:black hole physics; X-rays: binaries; X-rays: individual (NGC 5907 ULX1)
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory2015-83
Record Number:CaltechAUTHORS:20150306-121109629
Persistent URL:
Official Citation:NuSTAR and XMM-Newton Observations of the Extreme Ultraluminous X-Ray Source NGC 5907 ULX1: A Vanishing Act D. J. Walton et al. 2015 ApJ 799 122
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:55603
Deposited By: Ruth Sustaita
Deposited On:06 Mar 2015 23:24
Last Modified:30 Nov 2017 22:45

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