The ultraluminous x-ray sources ngc 1313 x-1 and x-2: a broadband study with NuSTAR and XMM-Newton

Matteo Bachetti; Vikram Rana; Dominic J. Walton; Didier Barret; Fiona A. Harrison; Steven E. Boggs; Finn Erland Christensen; William W. Craig; Andrew C. Fabian; Felix Fuerst; Brian W. Grefenstette; Charles J. Hailey; Ann Hornschemeier; Kristin K. Madsen; Jon M. Miller; Andrew F. Ptak; Daniel Stern; Natalie A. Webb; William W. Zhang

doi:10.1088/0004-637X/778/2/163

The ultraluminous x-ray sources ngc 1313 x-1 and x-2: a broadband study with NuSTAR and XMM-Newton

Authors:

Bachetti, Matteo ;
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Universite de Toulouse
Rana, Vikram ;
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California Institute of Technology
Walton, Dominic J. ;
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California Institute of Technology
Barret, Didier ;
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Universite de Toulouse
Harrison, Fiona A. ;
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California Institute of Technology
Boggs, Steven E. ;
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University of California at Berkeley
Christensen, Finn Erland ;
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0000-0001-5679-1946
National Space Institute, Technical University of Denmark
Craig, William W. ;
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Lawrence Livermore National Laboratory
Fabian, Andrew C. ;
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University of Cambridge
Fuerst, Felix ;
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California Institute of Technology
Grefenstette, Brian W. ;
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California Institute of Technology
Hailey, Charles J. ;
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Columbia University
Hornschemeier, Ann ;
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NASA Goddard Space Flight Center
Madsen, Kristin K. ;
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California Institute of Technology
Miller, Jon M. ;
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University of Michigan
Ptak, Andrew F. ;
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NASA Goddard Space Flight Center
Stern, Daniel ;
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California Institute of Technology
Webb, Natalie A. ;
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Universite de Toulouse
Zhang, William W.
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NASA Goddard Space Flight Center

DOI:

10.1088/0004-637X/778/2/163

Abstract:

We present the results of NuSTAR and XMM-Newton observations of the two ultraluminous X-ray sources: NGC 1313 X-1 and X-2. The combined spectral bandpass of the two satellites enables us to produce the first spectrum of X-1 between 0.3 and 30 keV, while X-2 is not significantly detected by NuSTAR above 10 keV. The NuSTAR data demonstrate that X-1 has a clear cutoff above 10 keV, whose presence was only marginally detectable with previous X-ray observations. This cutoff rules out the interpretation of X-1 as a black hole in a standard low/hard state, and it is deeper than predicted for the downturn of a broadened iron line in a reflection-dominated regime. The cutoff differs from the prediction of a single-temperature Comptonization model. Further, a cold disk-like blackbody component at similar to 0.3 keV is required by the data, confirming previous measurements by XMM-Newton only. We observe a spectral transition in X- 2, from a state with high luminosity and strong variability to a lower-luminosity state with no detectable variability, and we link this behavior to a transition from a super-Eddington to a sub-Eddington regime.

Type:

Journal article

Language:

English

Published in:

Astrophysical Journal, 2013, Vol 778, Issue 2

Keywords:

ASTRONOMY; MASS BLACK-HOLES; QUASI-PERIODIC OSCILLATIONS; SUPER-EDDINGTON ACCRETION; ACTIVE GALAXIES; BINARY-SYSTEMS; ESO 243-49; SLIM DISK; VARIABILITY; STATE; SPECTRA

Main Research Area:

Science/technology

Publication Status:

Published

Review type:

Peer Review

Submission year:

2014

Scientific Level:

Scientific

ID:

256282894

The ultraluminous x-ray sources ngc 1313 x-1 and x-2: a broadband study with NuSTAR and XMM-Newton

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