Straight-Up G—Determining the Solar Phase Coefficient of 462 Eriphyla

The Koronis family asteroid 462 Eriphyla was observed during February and March, 2000, to determine its solar phase coefficient G. Slivan (1995) presents analysis of several already-existing smaller data sets suggesting G=0.36, but no single data set had enough solar phase angle coverage to yield a reliable result. The quoted result was obtained by combining observations made during different apparitions, and is therefore subject to systematic errors. Here, we present five nights of new data obtained at Colgate University's Foggy Bottom Observatory that cover solar phase angles from 1° to 9°. All observations were made using the 0.4-m telescope equipped with a Photometrics STAR I CCD camera and a V filter. Data reduction and photometry were carried out using IRAF. Preliminary analysis of the new data suggests a value of G~0.18 for Eriphyla. An additional data point was recorded in late April at phase angle 15° to improve the final result; this new uniform data set will ultimately be used to improve the shape and spin axis solutions of Eriphyla.