A recent NuSTAR observation of the source GX 17+2
ATel #17234; Aditya S Mondal (Visva-Bharati)
on 18 Jun 2025; 16:26 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Aditya S. Mondal (adityas.mondal@visva-bharati.ac.in)
Subjects: X-ray, Binary, Neutron Star
In 2024, NuSTAR frequently observed the neutron star low-mass X-ray binary GX 17+2. One of these observations, performed on 2024 March 16, is considered for the present analysis. This observation (Obs ID: 30902026002) had an exposure time of roughly 13 ks. The source was clearly detected in the 3-40 keV energy band, with an average count of ~500 counts/s. The light curve showed some flaring at the initial part of the observation.
The 3-40 keV NuSTAR spectrum (FPMA and FPMB) was initially fitted with an absorbed single-temperature blackbody (bbodyrad in Xspec) and a multi-temperature blackbody component (diskbb in Xspec). A broad asymmetric Fe K-alpha emission and a Compton hump were present in the spectrum. The red wing of the Fe K-alpha emission line extends down to ~5 keV while the blue wing drops around ~7 keV. A relativistic reflection model (relxillNS) was introduced to model these spectral features. In addition, the spectrum showed the presence of two absorption edges, indicating the presence of absorbing material in the system. The whole combination of models gives a reduced chi^2=1117 for 975 d.o.f.
The disk and the blackbody temperature were found to be kT_in=1.98+-0.01 keV and kT_bb=3.1+-0.02 keV, respectively. The reflection fit reveals an inner disk radius of R_in=1.15+-0.04 R_ISCO and an inclination angle of i=38+-1 deg. The X-ray flux during this observation was ~1.31e-8 erg/s/cm^2 in the 3-40 keV energy band. The absorption edges were found at the energies of 8.20+-0.03 keV and 9.50+-0.05 keV. The R_in and inclination angle values are consistent with the previous measurements done by Ludlam et al. 2017, ApJ, 836, 140 from the analysis of the earlier NuSTAR observation.
