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Title: The ultraluminous X-ray sources NGC 1313 X-1 and X-2: a broadband study with NuSTAR and XMM-Newton
Authors: Bachetti, Matteo
Rana, V
Walton, Dominic J.
+16 Co-Authors
Keywords: accretion
accretion disks
black hole physics
stars: black holes
X-rays: individual
NGC 1313 X-1 NGC 1313 X-2
X-rays: stars
Issue Date: 1-Dec-2013
Publisher: IOP Sciences for The American Astronomical Society
Citation: The Astrophysical Journal, 2013, Vol.778, p11
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 ~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.
Description: Open Access
ISSN: 0004-637X
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Copyright: 2013, The American Astronomical Society
Appears in Collections:Research Papers (A&A)

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