We present the spectral analysis of bright steady states in an outburst of the transient neutron star low-mass X-ray binary (NS-LMXB) Swift J1858.6-0814 observed with NICER. We detected an ionized iron K absorption line (H-like Fe) at 6.97keV in the spectrum. We estimated the photoionization parameter using the ratio of the equivalent widths (EWs) of the FeXXVI (H-like) (17+\-5eV) and FeXXV (He-like) (<3eV) and discuss the origin of the iron absorption line. The irradiated gas producing the absorption line would locate within (3-6)*1E9cm from the X-ray source. We suggest that the observed H-like Fe absorption line originates from the highly-ionized gas in the inner accretion disk in Swift J1858.6-0814.
@article{arxiv.2401.09664,
title = {X-ray Iron absorption line in Swift J1858.6-0814},
author = {Kazumi Asai and Tatehiro Mihara and Kento Sakai and Aya Kubota},
journal= {arXiv preprint arXiv:2401.09664},
year = {2024}
}