Abstract
Gravitational microlensing of the superluminal components of the southern blazar PKS 0537-441 is proposed as a method for detecting objects with masses between 10-4 and 1 Modot in a foreground galaxy. A relativistic shock in the jet of the blazar can produce microlensing events on time scales of 1-3 days for lensing stars with masses in the 0.1-1 Modot range, and on time scales ranging from 30 minutes to 1 day for lensing brown dwarfs of 10-4-10-1 Modot at optical wavelengths. For events with amplification larger than Ao=2, a total optical depth τ ≈ 0.2 is estimated. We predict that monitoring the source during an observing period of 30 days should reveal several microlensing events in case that the relativistic propagation of a shock front through the blazar's jet creates a superluminal source component. The number and time scales of the resulting variability events can be used to enlighten the question about the mass function of compact objects in the foreground galaxy. For a mass function N(M)∝ M-2 in the 10-4-1 Modot range, 1 star event and 19 brown dwarf events are expected to be produced in a lapse of 30 days.
