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Title: Spectral Changes in the Hyperluminous Pulsar in NGC 5907 as a Function of Super-Orbital Phase
Authors: Fuerst, F.
Walton, D. J.
Rana, V
+5 Co-Authors
Keywords: accretion
accretion disks
pulsars: individual: NGC 5907 ULX1
X-rays: binaries
Issue Date: 1-Jan-2017
Publisher: IOP Sciences for The American Astronomical Society
Citation: The Astrophysical Journal, 2079, Vol.834, p7
Abstract: We present broadband, multi-epoch X-ray spectroscopy of the pulsating ultra-luminous X-ray source (ULX) in NGC 5907. Simultaneous XMM-Newton and NuSTAR data from 2014 are best described by a multicolor blackbody model with a temperature gradient as a function of accretion disk radius significantly flatter than expected for a standard thin accretion disk (T(r)\propto {r}-p, with p={0.608}-0.012+0.014). Additionally, we detect a hard power-law tail at energies above 10 keV, which we interpret as being due to Comptonization. We compare this observation to archival XMM-Newton, Chandra, and NuSTAR data from 2003, 2012, and 2013, and investigate possible spectral changes as a function of phase over the 78-day super-orbital period of this source. We find that observations taken around phases 0.3-0.4 show very similar temperature profiles, even though the observed flux varies significantly, while one observation taken around phase 0 has a significantly steeper profile. We discuss these findings in light of the recent discovery that the compact object is a neutron star and show that precession of the accretion disk or the neutron star can self-consistently explain most observed phenomena.
Description: Open Access
ISSN: 0004-637X
Alternative Location:
Copyright: 2017, The American Astronomical Society
Appears in Collections:Research Papers (A&A)

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