Monitoring Observations of SMC X-1’s Excursions (MOOSE) III: X-ray Spectroscopy of a Warped, Precessing Accretion Disc

Rawan Karam ( Université McGill )

The MOOSE (Monitoring Observations of SMC X-1’s Excursions) program uses the Neutron Star Interior Composition Explorer Mission (NICER) to monitor the high mass X-ray binary SMC X-1 during its superorbital period excursions. Here, we perform X-ray spectral analyses of 26 NICER observations of SMC X-1, taken at the tail-end of the excursion between 2021-04-01 and 2022-01-05. We use a single spectral model to fit spectra observed in high, intermediate and low states, using a combination of a partial covering fraction model, a black-body disc, and a power-law component. We find that the model best fits for the black-body disc temperature and photon index do not vary significantly with the superorbital period; however, the partial covering fraction does vary significantly with the superorbital state.