SIMBAD references

We use the statistics of caustic crossings induced by microlensing in the lens system Q 2237+0305 to study the lens galaxy peculiar velocity. We calculate the caustic crossing rates for a comprehensive family of stellar mass functions and find a dependence of the average number of caustic crossings with the effective transverse velocity and the average mass, (n) ∝ v_eff/ sqrt{(m)}, equivalent to the theoretical prediction for the case of microlenses with identical masses. We explore the possibilities of the method to measure v_eff using the ∼12 yr of Optical Gravitational Lensing Experiment monitoring of the four images of Q 2237+0305. To determine a lower limit for v_eff, we count, conservatively, a single caustic crossing for each one of the four high magnification events identified in the literature (plus one additional proposed by us) obtaining v_eff ≳ 240 sqrt{(m)/0.17M_☉} km/s at 68% of confidence. From this value and the average FWHM of the four high magnification events, we obtain a lower limit of r_s ≳ 1.4 sqrt{(m)/0.17M_☉} light-days for the radius of the source (r_s = FWHM/2.35). Tentative identification of three additional caustic crossing events leads to estimates of v_eff ~= (493 ± 246) sqrt{(m)/0.17M_☉} for the effective transverse velocity and of r_s ~= (2.7 ± 1.3) sqrt{(m)/0.17M_☉} light-days for the source size. The estimated transverse peculiar velocity of the galaxy is v_t ~= (429 ± 246) sqrt{(m)/0.17M_☉} km/s.