Constraining the physical parameters of XTE J1701−462 through NuSTAR observations

Abstract

The spectral properties of the transient neutron star low mass X-ray binary XTE J1701−462 were studied using the data obtained from FPMA/B detectors onboard NuSTAR during its second known outburst (2022 September). The physical parameters of the system were derived from the analysis of the data in the 3.0−30.0 keV energy range. The patterns displayed on the hardness-intensity diagram of the three observations closely resembled the banana branch/normal branch, a vertex of horizontal and normal branch of the Z track and a transition from normal branch to flaring branch. Spectral analysis of the source revealed the presence of Fe K emission complex. The source spectra were fitted with a multi-temperature black body ($\mathtt {diskbb}$) component in conjunction with the reflection model ($\mathtt {relxillNS}$). The values of temperature (kTin) and radius (Rin) of the inner accretion disc obtained from the spectral fitting with the model combination - $\mathtt {constant} \times \mathtt {tbabs} (\mathtt {diskbb}$+$\mathtt {relxillNS})$ showed the source to be in its soft spectral state during the observations. The inclination angle (θ) of the source was estimated to be between 19 − 33○ and the inner disc radius (Rin) was found to be 17.4 km. Assuming the case of magnetic truncation of accretion disc, the upper limits for the magnetic dipole moment (μ) and the magnetic field strength (B) at the poles of the neutron star in the system were found to be 5.78 × 1026 G cm3 and 8.23 × 108 G, respectively, for kA = 1.