MOA 2003-BLG-37: A BULGE JERK-PARALLAX MICROLENS DEGENERACY

We analyze the Galactic bulge microlensing event MOA 2003-BLG-37. Although the Einstein timescale is relatively short, tE = 43 days, the light curve displays deviations consistent with parallax effects due to the Earth's accelerated motion. We show that the χ2 surface has four distinct local minima that are induced by the "jerk-parallax" degeneracy, with pairs of solutions having projected Einstein radii E = 1.76 and 1.28 AU, respectively. This is the second event displaying such a degeneracy and the first toward the Galactic bulge. For both events, the jerk-parallax formalism accurately describes the offsets between the different solutions, giving hope that when extra solutions exist in future events they can easily be found. However, the morphologies of the χ2 surfaces for the two events are quite different, implying that much remains to be understood about this degeneracy.