Visible and infrared photometry of six Centaurs

We present infrared (JHK) and visible (VRI) observations of the Centaurs 2060 Chiron, 5145 Pholus, 7066 Nessus, 1995 DW2, 1995 GO, and 1997 CU26. These are combined whenever possible to derive relative reflectance spectra between 0.55 acid 2.2 mu m. The extreme visible to infrared color of Pholus found in 1992 is confirmed, as is the redness of 7066 Nessus, We refine the rotation period and lightcurve of 1995 GO and resolve ambiguous determinations of its V-R color. We find that 1997 CU26 has V-JHK colors very similar to 1995 GO. Our data imply changes in the visible-IR color of 2060 Chiron with level of cometary activity and, aware of the difficulties of combining nonsimultaneous data, we comment on the likely reality of these. We find a wide range of reflectances within the Centaur population with no obvious correlations with heliocentric distance. (C) 1998 Academic Press.