Context : Gravitational microlensing is sensitive to compact-object lenses in the Milky Way , including white dwarfs , neutron stars , or black holes , and could potentially probe a wide range of stellar-remnant masses .
However , the mass of the lens can be determined only in very limited cases , due to missing information on both source and lens distances and their proper motions .

Aims : Our aim is to improve the mass estimates in the annual parallax microlensing events found in the eight years of OGLE-III observations towards the Galactic Bulge with the use of Gaia Data Release 2 ( DR2 ) .

Methods : We use Gaia DR2 data on distances and proper motions of non-blended sources and recompute the masses of lenses in parallax events .
We also identify new events in that sample which are likely to have dark lenses ; the total number of such events is now 18 .

Results : The derived distribution of masses of dark lenses is consistent with a continuous distribution of stellar-remnant masses .
A mass gap between neutron star and black hole masses in the range between 2 and 5 solar masses is not favoured by our data , unless black holes receive natal kicks above 20-80 km/s .
We present eight candidates for objects with masses within the putative mass gap , including a spectacular multi-peak parallax event with mass of 2.4 ^ { +1.9 } _ { -1.3 } M _ { \odot } located just at 600 pc .
The absence of an observational mass gap between neutron stars and black holes , or conversely the evidence of black hole natal kicks if a mass gap is assumed , can inform future supernova modelling efforts .

Conclusions :