089040

Accreting pulsar SMC X-1 exhibits a superorbital cycle likely caused by a warped precessing accretion disk which drives behaviors like pulsation transience and varying spectral obscuration levels. The superorbital cycle is typically virgul55 days but has excursions driven by instability in the disk geometry where the period increases to 44 days. There exists no broad-band spectral and timing coverage of superorbital excursion. This proposal asks for simultaneous NuSTAR and XMM observations to sample the upcoming 2022 excursion. A unique opportunity to use tomography to probe the fluctuating disk geometry and investigate the effect of excursion on obscuration levels pulse shape and pulsation transience. [truncated! Please see actual data for full text]