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Radial distribution of dust grains around HR 4796A

Wahhaj, Z. and Koerner, D. W. and Backman, D. E. and Werner, M. W. and Serabyn, E. and Ressler, M. E. and Lis, D. C. (2005) Radial distribution of dust grains around HR 4796A. Astrophysical Journal, 618 (1). pp. 385-396. ISSN 1538-4357


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Publisher’s or external URL: http://dx.doi.org/10.1086/425858


We present high dynamic range images of circumstellar dust around HR 4796A that were obtained with MIRLIN at the Keck II telescope at lambda = 7.9, 10.3, 12.5, and 24.5 mum. We also present a new continuum measurement at 350 mum obtained at the Caltech Submillimeter Observatory. Emission is resolved in Keck images at 12.5 and 24.5 mum with point-spread function FWHM values of 0".37 and 0".55, respectively, and confirms the presence of an outer ring centered at 70 AU. Unresolved excess infrared emission is also detected at the stellar position and must originate well within 13 AU of the star. A model of dust emission fitted to flux densities at 12.5, 20.8, and 24.5 mum indicates that dust grains are located 4(-2)(+3) AU from the star with effective size 28 +/- 6 mum and an associated temperature of 260 +/- 40 K. We simulate all extant data with a simple model of exozodiacal dust and an outer exo-Kuiper ring. A two-component outer ring is necessary to fit both Keck thermal infrared and Hubble Space Telescope scattered-light images. Bayesian parameter estimates yield a total cross-sectional area of 0.055 AU(2) for grains roughly 4 AU from the star, and an outer-dust disk composed of a narrow large-grain ring embedded within a wider ring of smaller grains. The narrow ring is 14 +/- 1 AU wide with inner radius 66 +/- 1 AU and total cross-sectional area 245 AU2. The outer ring is 80 +/- 15 AU wide with inner radius 45 +/- 5 AU and total cross-sectional area 90 AU2. Dust grains in the narrow ring are about 10 times larger and have lower albedos than those in the wider ring. These properties are consistent with a picture in which radiation pressure dominates the dispersal of an exo-Kuiper belt.

Item Type: Article
Publisher’s Statement: © 2005 The American Astronomical Society. Published by IOP Publishing.
ID number or DOI: 10.1086/425858
Keywords: belt; beta-pictoris; circumstellar disk; circumstellar matter; debris; Evolution; infrared observations; infrared : stars; Particles; planetary systems : formation; planetary systems : protoplanetary disks; solar-system; solar system : formation; Stars; stars : individual (HR 4796A); zodiacal dust
Subjects: Q Science > QB Astronomy
NAU Depositing Author Academic Status: Faculty/Staff
Department/Unit: College of Engineering, Forestry, and Natural Science > Physics and Astronomy
Date Deposited: 30 Sep 2015 18:42
URI: http://openknowledge.nau.edu/id/eprint/440

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