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, Δ 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 9σ) different. The satellite Hi'iaka is unusually blue in J − H , consistent with strong 1.5 μm water-ice absorption. The phase coefficient of Haumea is found to increase monotonically with wavelength in the range 0.4 < λ < 1.3. We compare our findings with other solar system objects and discuss implications regarding the surface of Haumea.