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We have obtained new resolved images of the well-studied HR 4796A dust ringat 18 and 25 microns with the 8-meter Gemini telescopes. These images confirmthe previously observed spatial extent seen in mid-IR, near-IR, and opticalimages of the source. We detect brightness and temperature asymmetries suchthat dust on the NE side is both brighter and warmer than dust in the SW. Weshow that models of so-called pericenter glow account for these asymmetries,thus both confirming and extending our previous analyses. In this scenario, thecenter of the dust ring is offset from the star due to gravitationalperturbations of a body with an eccentric orbit that has induced a forcedeccentricity on the dust particle orbits. Models with 2-micron silicate dustparticles and a forced eccentricity of 0.06 simultaneously fit the observationsat both wavelengths. We also show that parameters used to characterize thethermal-emission properties of the disk can also account for the disk asymmetryobserved in shorter-wavelength scattered-light images.

Asymmetric Heating of the HR 4796A Dust Ring Due to Pericenter Glow