1999ApJ...512..672A

We present photometric and spectroscopic data for the second microlensing event seen toward the Small Magellanic Cloud (SMC), MACHO 98-SMC-1. The lens is a binary. We resolve the caustic crossing and find that the source took 2 Δt=8.5 hr to transit the caustic. We measure the source temperature T_eff=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 I_s=22.15. The angle implies that the lens crosses the source radius in time t_*=Δtsinφ=2.92 hr. The magnitude (together with the temperature) implies that the angular radius of the source is θ_*=0.089 µas. Hence, the proper motion is µ=θ_*/t_*=1.26 km.s^–1.kpc^–1. For the second solution, the corresponding parameters are φ=30°.6, I_s=21.81, t_*=2.15 hr, θ_*=0.104 µas, and µ=θ_*/t_*=2.00 km.s^–1.kpc^–1. Both proper-motion estimates are slower than 99.5% of the proper motions expected for halo lenses. Both are consistent with an ordinary binary lens moving at ∼75-120 km.s^–1 within the SMC itself. We conclude that the lens is most likely in the SMC proper.