Program: GN-2018A-Q-224

We have discovered a new type of brief but very energetic flaring phenomenon in two X-ray sources believed to be associated with extragalactic globular clusters. These flares reach X-ray luminosities two orders of magnitude larger than the Eddington limit of a neutron star yet the process does not destroy the object. If their optical counterparts can be confirmed to be globular clusters around other galaxies, they represent the most energetic sources ever discovered in globular clusters. On a broader scale, these sources will join soft gamma repeaters and anomalous X-ray pulsars as the only astrophysical sources that flare by factors of >100 above the Eddington limit of a neutron star on time scales less than one minute without destroying the object. Here, we propose to obtain a Gemini-N GMOS spectrum of the optical counterpart of the more extreme of the two sources to determine if it is associated with an extragalactic globular cluster of NGC4636, in order to confirm its distance and extreme luminosity.