SIMBAD references

We present the spectral analysis of bright steady states in an outburst of the transient neutron star low-mass X-ray binary Swift J1858.6-0814 observed with the Neutron star Interior Composition Explorer (NICER). We detected an ionized iron K absorption line (H-like Fe) at 6.97 keV in the spectrum. We estimate the photoionization parameter using the ratio of the equivalent widths of the Fe XXVI (H-like) (17 ± 5 eV) and Fe XXV (He-like) (<3 eV) and discuss the origin of the iron absorption line. The irradiated gas producing the absorption line would locate within (3-6) × 10⁹ cm of 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.