We report the detection of a ring of warm dust in the edge-on disk
surrounding HD 32297 with the Gemini-N/MICHELLE mid-infrared imager. Our
N'-band image shows elongated structure consistent with the orientation of the
scattered-light disk. The Fnu(11.2 um) = 49.9+/-2.1 mJy flux is significantly
above the 28.2+/-0.6 mJy photosphere. Subtraction of the stellar point spread
function reveals a bilobed structure with peaks 0.5"-0.6" from the star. An
analysis of the stellar component of the SED suggests a spectral type later
than A0, in contrast to commonly cited literature values. We fit
three-dimensional, single-size grain models of an optically thin dust ring to
our image and the SED using a Markov chain Monte Carlo algorithm in a Bayesian
framework. The best-fit effective grain sizes are submicron, suggesting the
same dust population is responsible for the bulk of the scattered light. The
inner boundary of the warm dust is located 0.5"-0.7" (~65 AU) from the star,
which is approximately cospatial with the outer boundary of the scattered-light
asymmetry inward of 0.5". The addition of a separate component of larger,
cooler grains that provide a portion of the 60 um flux improves both the
fidelity of the model fit and consistency with the slopes of the
scattered-light brightness profiles. Previous indirect estimates of the stellar
age (~30 Myr) indicate the dust is composed of debris. The peak vertical
optical depths in our models (~0.3-1 x 1e-2) imply that grain-grain collisions
likely play a significant role in dust dynamics and evolution. Submicron grains
can survive radiation pressure blow-out if they are icy and porous. Similarly,
the inferred warm temperatures (130-200 K) suggest that ice sublimation may
play a role in truncating the inner disk.Comment: ApJ accepted, 8 pages, 4 figure
