A hard X-ray study of the ultraluminous X-ray source NGC 5204 X-1 with NuSTAR and XMM-Newton

E. S. Mukherjee, D. J. Walton, M. Bachetti, F. A. Harrison, D. Barret, E. Bellm, S. E. Boggs, Finn Erland Christensen, W. W. Craig, A. C. Fabian, F. Fuerst, B. W. Grefenstette, C. J. Hailey, K. K. Madsen, M. J. Middleton, J. M. Miller, V. Rana, D. Stern, W. Zhang

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We present the results from coordinated X-ray observations of the ultraluminous X-ray source NGC 5204 X-1 performed by the Nuclear Spectroscopic Telescope Array and XMM-Newton in early 2013. These observations provide the first detection of NGC 5204 X-1 above 10 keV, extending the broadband coverage to 0.3-20 keV. The observations were carried out in two epochs separated by approximately 10 days, and showed little spectral variation with an observed luminosity of LX = (4.95 ± 0.11) × 1039 erg s-1. The broadband spectrum robustly confirms the presence of a clear spectral downturn above 10 keV seen in some previous observations. This cutoff is inconsistent with the standard low/hard state seen in Galactic black hole binaries, as would be expected from an intermediate-mass black hole accreting at significantly sub-Eddington rates given the observed luminosity. The continuum is apparently dominated by two optically thick thermal-like components, potentially accompanied by a faint high-energy tail. The broadband spectrum is likely associated with an accretion disk that differs from a standard Shakura & Sunyaev thin disk.
Original languageEnglish
Article number64
JournalAstrophysical Journal
Issue number1
Number of pages7
Publication statusPublished - 2015


  • Black hole physics
  • X-rays: binaries
  • X-rays: individual (NGC 5204 X-1)

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