  Gamma-ray burst (GRB) 111215A was bright at X-ray and radio frequencies, but
not detected in the optical or near-infrared (nIR) down to deep limits. We have
observed the GRB afterglow with the Westerbork Synthesis Radio Telescope and
Arcminute Microkelvin Imager at radio frequencies, with the William Herschel
Telescope and Nordic Optical Telescope in the nIR/optical, and with the Chandra
X-ray Observatory. We have combined our data with the Swift X-Ray Telescope
monitoring, and radio and millimeter observations from the literature to
perform broadband modeling, and determined the macro- and microphysical
parameters of the GRB blast wave. By combining the broadband modeling results
with our nIR upper limits we have put constraints on the extinction in the host
galaxy. This is consistent with the optical extinction we have derived from the
excess X-ray absorption, and higher than in other dark bursts for which similar
modeling work has been performed. We also present deep imaging of the host
galaxy with the Keck I telescope, Spitzer Space Telescope, and Hubble Space
Telescope (HST), which resulted in a well-constrained photometric redshift,
giving credence to the tentative spectroscopic redshift we obtained with the
Keck II telescope, and estimates for the stellar mass and star formation rate
of the host. Finally, our high resolution HST images of the host galaxy show
that the GRB afterglow position is offset from the brightest regions of the
host galaxy, in contrast to studies of optically bright GRBs.
