Gaia18cbf Gi light curves

We investigate the range of microlensing models and use them to derive the most probable mass and distance to the lens using a Galactic model as a prior. Using known mass-brightness relation we determined how likely it is that the lens is a main sequence star. This event is one of the longest ever detected, with the Einstein timescale of t_E_=491.41^+128.31^_-84.94_ days for the best solution and t_E_=453.74^+178.69^_-105.74_ days for the second-best.

Assuming Galaxy priors, this translates to the most probable lens mass of M_L_=2.65^+509^_-1.48_M_{sun}_ and M_L_=1.71^+3.78^_-1.06_M_{sun}_, respectively. The limits on the blended light suggest that this event was most likely not caused by a main sequence star, but rather by a dark remnant of stellar evolution.