NICER observation list: Target ID 557105

Abstract

Cir X-1 is the youngest known binary system in our Galaxy, hosting a neutron star. A NICER AO2 observation was carried out to cover the entire Cir X-1 orbit with 99 regular snapshots. Three iron emission/absorption lines were observed near the periastron (phase=0) at 6.4 keV, 6.7 keV and 7.0 keV. In particular, the highly ionized Fe lines at 6.7 keV and 7.0 keV switched from emission to absorption between the orbital phases 0.93 and 0.96. We hope to clarify these line production mechanisms by studying orbit-by-orbit variation/stability of the emission/absorption line strengths and the transition phase. We concentrate on the orbital phase-period when the emission lines switch to the absorption lines (0.85-1.05) and propose to monitor this phase-period over the AO4 duration.
Obsid RA DEC l b Start End Exposure Number of
Modules
Number of
Processing
Status of
Processing
Date of
Processing
Public
date
5571050101 230.171 -57.167 322.119 0.038 59736.3240 59736.9884 4171.0 52 7 VALIDATED 59752.0 59930
5571050102 230.170 -57.167 322.119 0.038 59737.1005 59737.8912 4757.0 52 5 VALIDATED 59748.2 59931