Photometry of the Trans-Neptunian Object 1993 SC

We obtained broadband photometry of the Trans-Neptunian Object 1993 SC with the Steward Observatory 1.5-m telescope near Mt. Bigelow, Arizona and the Lunar and Planetary Laboratory CCD on 1996 October 8. 1993 SC exhibited a constant brightness (V=22.67) with a la scatter about the average of 0.06 magnitudes during a five hour interval. In addition, we obtained observations of 1993 SC with the Steward Observatory 2.3-m telescope on Kitt Peak, Arizona during 1995 November 24-27. Once again 1993 SC exhibited a constant brightness (V=22.73) with a 1 sigma scatter about the average of 0.03 magnitude. If 1993 SC has a lightcurve, the amplitude must be at the level of 0.12 magnitude or less. If the obliquity of 1993 SC is near zero degrees, then 1993 SC is spherical with a semi-major to semi-minor axis ratio less than or equal to 1.12. A spherical nature for 1993 SC may be the result of self-gravity exceeding the tensile strength of the material in the interior of 1993 SC. If the obliquity of 1993 SC is large, then 1993 SC could have an irregular shape. The steady intrinsic brightness for 1993 SC suggests that the object has a relatively uniform surface albedo. Our photometry and the assumption of a comet-like albedo (0.04) indicates that the diameter of 1993 SC is similar to 240 km. (C) 1997 American Astronomical Society.