TIME-RESOLVED NEAR-INFRARED PHOTOMETRY OF EXTREME KUIPER BELT OBJECT HAUMEA

We present time-resolved near- infrared (J and H) photometry of the extreme Kuiper belt object ( 136108) Haumea (formerly 2003 EL61) taken to further investigate rotational variability of this object. The new data show that the near- infrared peak-to-peak photometric range is similar to the value at visible wavelengths Delta m(R) = 0.30 +/- 0.02 mag. Detailed analysis of the new and previous data reveals subtle visible/near-infrared color variations across the surface of Haumea. The color variations are spatially correlated with a previously identified surface region, redder in B - R and darker than the mean surface. Our photometry indicates that the J - H colors of Haumea (J - H = -0.057 +/- 0.016 mag) and its brightest satellite Hi'iaka (J - H = -0.399 +/- 0.034 mag) are significantly (greater than 9 sigma) different. The satellite Hi'iaka is unusually blue in J - H, consistent with strong 1.5 mu m water-ice absorption. The phase coefficient of Haumea is found to increase monotonically with wavelength in the range 0.4 < lambda < 1.3. We compare our findings with other solar system objects and discuss implications regarding the surface of Haumea.