Absence of Reflection Features in NuSTAR Spectra of the Luminous Neutron Star X-Ray Binary GX 5-1

作者：Homan Jeroen^*; Steiner James F; Lin Dacheng; Fridriksson Joel K; Remillard Ronald A; Miller Jon M; Ludlam Renee M

来源：Astrophysical Journal, 2018, 853(2): 157.

DOI：10.3847/1538-4357/aaa439

• accretion, accretion disks
• stars: neutron
• X-rays: binaries
• X-rays: individual (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 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 (similar to 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.

• 出版日期2018-2-1
• 单位MIT