NICER observation list: Target ID 363801

We request 100 ks of NICER observations of the high mass X-ray binary SMC X-1 to investigate and model changes in accretion structure with super-orbital cycle. SMC X-1 displays quasi-periodic super-orbital modulation, likely because of instabilities in the warped accretion disc. We propose to study the variable structure of the inner disc using four NICER observations of 25 ks each during the high state of different super-orbital cycles. We will perform phase-resolved spectral analysis and a principal component analysis to determine the origin of variations in the soft X-ray emission and use a simple warped disc model to constrain the changes in accretion and disc geometry. This work will probe the effect of the variable disc on the accretion structure in SMC X-1 with unprecedented detail.