We present direct imaging observations at wavelengths of 3.3, 3.8 (L',band), and 4.8 (M band) microns, for the planetary system surrounding HR 8799. All three planets are detected at L'. The c and d component are detected at 3.3 microns, and upper limits are derived from the M band observations. These observations provide useful constraints on warm giant planet atmospheres. We discuss the current age constraints on the HR 8799 system, and show that several potential co-eval objects can be excluded from being co-moving with the star. Comparison of the photometry is made to models for giant planet atmospheres. Models which include non-equilibrium chemistry provide a reasonable match to the colors of c and d. From the observed colors in the thermal infrared we estimate T_eff < 960 K for b, and T_eff=1300 and 1170 K for c and d, respectively. This provides an independent check on the effective temperatures and thus masses of the objects from the Marois 2008 results.
@article{arxiv.1003.4986,
title = {Thermal Infrared MMTAO Observations of the HR 8799 Planetary System},
author = {Philip M. Hinz and Timothy J. Rodigas and Matthew A. Kenworthy and Suresh Sivanandam and Aren N. Heinze and Eric E. Mamajek and Michael R. Meyer},
journal= {arXiv preprint arXiv:1003.4986},
year = {2015}
}