The mineralogy and structure of the inner debris disk of β pictoris

Abstract

We observed the edge-on, planet-bearing disk of β Pictoris using T-ReCS at Gemini to clarify and extend previous observations and conclusions about this unique system. Our spectroscopy and spectral modeling of the 10 μm silicate feature constrain the spatial distributions of three representative dust components (0.1 μm/2.0 μm glassy olivine and crystalline forsterite) across the inner 20 AU of the disk. We confirm that the 2.0 μm glassy olivine is strongly peaked in the disk center and that the 0.1 μm glassy olivine does not show this concentration, but rather is double peaked, with the peaks on either side of the star. However, we do not see the strong difference in brightness between those two peaks reported in a previous study. Although the spatial distribution of the 0.1 μm dust is consistent with the scenario of a dust-replenishing planetesimal belt embedded in the disk, we note an alternative interpretation that can explain the spatial distributions of the 0.1 μm and 2.0 μm grains simultaneously and does not require the planetesimal belt. In addition to the spectroscopy, we also obtained a new 11.7 μm image of the β Pic disk. By comparing this image with that acquired in 2003, we confirm the existence and overall shape of the dusty clump at 52 AU in the SW disk. We speculate that the clump's projected spatial displacement of 2.0 AU, a 3.6σ result, between two epochs separated by seven years is due to the Keplerian motion of the clump at an orbital radius of 54.3+2.0 -1.2 AU. © 2012. The American Astronomical Society. All rights reserved..