Probing orbits of stellar mass objects deep in galactic nuclei with quasiperiodic eruptions

Quasiperiodic eruptions (QPEs) are intense, repeating, soft x-ray bursts with recurrence times of about a few to ten hours from nearby galactic nuclei. The origin of QPEs is still unclear. In this work, we investigate the extreme mass ratio inspiral (EMRI) + accretion disk model, where the disk is formed from a previous tidal disruption event (TDE). In this EMRI & thorn; TDE disk model, the QPEs are the result of collisions between a TDE disk and a stellar mass object (a stellar mass black hole or a main sequence star) orbiting around a supermassive black hole (SMBH) in galactic nuclei. If this interpretation is correct, QPEs will be invaluable in probing the orbits of stellar mass objects in the vicinity of SMBHs and further inferring the formation of EMRIs, which are one of the primary targets of spaceborne gravitational wave missions. Taking GSN 069 as an example, we find the EMRI that is of low eccentricity (e < 0.1 at the 3-sigma confidence level) and a semimajor axis about O(10(2)) gravitational radii of the central SMBH, which is consistent with the prediction of the wet EMRI formation channel while incompatible with alternatives.