Testing EMRI models for Quasi-Periodic Eruptions with the 3-year NICER campaign of eRO-QPE1

Quasi-Periodic Eruptions (QPEs) are luminous X-ray outbursts recurring on hour timescales, observed from the nuclei of a growing handful of nearby low-mass galaxies. Their physical origin is still debated, but leading models invoke 1) recurring accretion disk instabilities, or 2) interaction of the SMBH with a lower mass companion in an extreme mass-ratio inspiral (EMRI). In this talk, I will present results from a 3-year NICER monitoring campaign of eRO-QPE1, a source which exhibits exceptionally erratic QPEs that have been challenging for the simplest EMRI models. We report 1) the QPEs persist for 3 years, then disappear in October 2023; 2) complex evolution in the QPE fluence, temperature, and emitting area; and 3) the presence of a possible 5.7-day super-period in the QPE arrival times. This tentative 5.7-day period aligns with the expected frequency for Lense-Thirring precession of the accretion disk, supporting EMRI-disk collision models powering the QPEs.