NICER observation list: Target ID 770401

We propose a monitoring program for LMC X-3 to capture this persistent and soft source which ranges over a month-long timescale from a few percent Eddington to near its Eddington limit. Polarimetric data over this luminosity range allows assessment of slim-disk effects in the inner-disk geometry. At low luminosities, the thermal state of black holes in X-ray binaries is simple and stable, with a fixed inner-disk radius and exhibiting low rms-variability. At high luminosities >~ 30% of the Eddington limit, slim-disk effects manifest as the disk scale-height grows. X-ray polarimetry can uniquely map the inner-disk geometry vs luminosity, and can distinguish the role of returning radiation (enhanced for thicker disks), which may be important in governing polarization strength.