The Relative Lens-Source Proper Motion in MACHO 98-SMC-1

We present photometric and spectroscopic data for the second microlensing event seen toward the Small Magellanic Cloud (SMC), MACHO-98-SMC-001. The lens is a binary. We resolve the caustic crossing and find that the source took 2∆t = 8.5 hours to transit the caustic. We measure the source temperature Teff = 8000 K both spectroscopically and from the color (V − I)0 ∼ 0.22. We find two acceptable binary-lens models. In the first, the source crosses the caustic at φ = 43.2 and the unmagnified source magnitude is Is = 22.15. The angle implies that the lens crosses the source radius in time t∗ = ∆t sin φ = 2.92 hours. The magnitude Univ. of Canterbury, Dept. of Physics & Astronomy, Private Bag 4800, Christchurch, New Zealand Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen, The Netherlands South African Astronomical Observatory, P.O. Box 9, Observatory 7935, South Africa Ohio State University, Department of Astronomy, Columbus, OH 43210, U.S.A. Univ. of Tasmania, Physics Dept., G.P.O. 252C, Hobart, Tasmania 7001, Australia Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD. 21218 U.S.A. Perth Observatory, Walnut Road, Bickley, Perth 6076, Australia