CaltechAUTHORS
Published February 1, 2015 | Version Published + Submitted
Journal Article Open

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

Creators

Abstract

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.

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

Attached Files

Published - 0004-637X_799_2_122.pdf

Submitted - 1411.5974v1.pdf

Files

0004-637X_799_2_122.pdf

Files (813.7 kB)

Name Size Download all
md5:97ffc20e57e154da5d9fbdedec3d075f
547.8 kB Preview Download
md5:be7812ea4b130cbbfbddf34722b82608
265.8 kB Preview Download

Additional details

Identifiers

Eprint ID
55603
Resolver ID
CaltechAUTHORS:20150306-121109629

Related works

Describes
http://arxiv.org/abs/1411.5974 (URL)

Funding

Centre National d'Études Spatiales (CNES)
NASA/Caltech/JPL
ESA Member States

Dates

Created
2015-03-06
Created from EPrint's datestamp field
Updated
2021-11-10
Created from EPrint's last_modified field

Caltech Custom Metadata

Caltech groups
NuSTAR, Space Radiation Laboratory
Other Numbering System Name
Space Radiation Laboratory
Other Numbering System Identifier
2015-83