Absence of Reflection Features in NuSTAR Spectra of the Luminous Neutron Star X-Ray Binary GX 5-1
We present NuSTAR observations of the luminous neutron star low-mass X-ray binary (NS LMXB) and Z source GX 5−1. During our three observations made with separations of roughly two days, the source traced out an almost complete Z track. We extract spectra from the various branches and fit them with a...
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Published in | The Astrophysical journal Vol. 853; no. 2; pp. 157 - 162 |
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Main Authors | , , , , , , |
Format | Journal Article |
Language | English |
Published |
Philadelphia
The American Astronomical Society
01.02.2018
IOP Publishing |
Subjects | |
Online Access | Get full text |
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Summary: | We present NuSTAR observations of the luminous neutron star low-mass X-ray binary (NS LMXB) and Z source GX 5−1. During our three observations made with separations of roughly two days, the source traced out an almost complete Z track. We extract spectra from the various branches and fit them with a continuum model that has been successfully applied to other Z sources. Surprisingly, and unlike most of the (luminous) NS-LMXBs observed with NuSTAR, we do not find evidence for reflection features in any of the spectra of GX 5−1. We discuss several possible explanations for the absence of reflection features. Based on a comparison with other accreting neutron star systems, and given the high luminosity of GX 5−1 (∼1.6-2.3 times the Eddington luminosity, for a distance of 9 kpc), we consider a highly ionized disk the most likely explanation for the absence of reflection features in GX 5−1. |
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Bibliography: | High-Energy Phenomena and Fundamental Physics LET35429R |
ISSN: | 0004-637X 1538-4357 |
DOI: | 10.3847/1538-4357/aaa439 |