Relativistic X-ray reflection and photoionized absorption in the neutron star low-mass X-ray binary GX 13+1

We analysed a dedicated NuSTAR observation of the neutron-star low-mass X-ray binary Z-source GX 13+1 to study timing and spectral properties source. From colour-colour diagram, we conclude that during source transitioned from normal branch flaring branch. fitted spectra in each with model consisting an accretion disc, Comptonised blackbody, relativistic reflection (relxillNS), photo-ionised absorption (warmabs). Thanks combination large effective area good energy resolution at high energies, found evidence both Fe K line profile, Compton hump present 10--25 keV range. The inner disc radius is $R_{\rm in} \lesssim 9.6~r_g$, which allowed us further constrain magnetic field strength $B 1.8 \times 10^8$ G. also for presence hot wind leading Ni, Ni overabundance $\sim$6 times solar. fits, find distance between ionising slab ionised absorbing material $\sim 4-40 10^5$ km. width boundary layer extends $\sim$3 km above surface neutron star, yielded NS}\lesssim 16$ scenario inferred modelling becomes self-consistent only electron densities disk, $n_e \sim 10^{22}-10^{23}$ cm$^{-3}$, as expected Shakura-Sunyaev significantly provided by relxillNS models. These results have implications our understanding physical conditions 13+1.