Optical and infrared photometry of Kuiper Belt object 1993SC

Minor planet 1993SC, with a semi-major axis of 39.67 AU, is one of the brightest of numerous recently discovered objects with orbits close to or beyond Neptune. It is a member of the Kuiper Belt, a planetesimal population remaining from the formation of the Solar System. We present optical photometry which indicates a lightcurve amplitude of less than 0.2 magnitude for 1993SC and which does not support the 0.5 magnitude lightcurve of I. P. Williams et al. (Icarus 116, 180-185, 1995). We derive (Kron-Cousins photometric system) V - R 0.54 +/- 0.14, V - I = 0.97 +/- 0.14, and V - J = 2.08 +/- 0.15, which confirm that 1993SC has optical/infrared colors closer to Centaur 1993HA(2) than to the extremely red 5145 Pholus. We also find that VRI colors published by J. X. Luu and D. C. Jewitt (Astron. J. 111, 499-503, 1996) are inconsistent with their reflectance spectrum of 1993SC and we derive new values from their reflectance spectrum of V - R = 0.56 +/- 0.08 and V - I = 1.19 +/- 0.18, which give reasonable agreement with our results. (C) 1997 Academic Press