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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 308574.0, MPI für Astronomie / Publikationen_mpia
Discovery of an 86 AU radius debris ring around HD 181327
Authors:Schneider, G.; Silverstone, M. D.; Hines, D. C.; Augereau, J.-C.; Pinte, C.; Ménard, F.; Krist, J.; Clampin, M.; Grady, C.; Golimowski, D.; Ardila, D.; Henning, T.; Wolf, S.; Rodmann, J.
Date of Publication (YYYY-MM-DD):2006
Journal Abbrev.:The Astrophysical Journal
Start Page:414
End Page:431
Audience:Not Specified
Abstract / Description:HST NICMOS PSF-subtracted coronagraphic observations of HD 181327 have revealed the presence of a ringlike disk of circumstellar debris seen in 1.1 mum light scattered by the disk grains, surrounded by a diffuse outer region of lower surface brightness. The annular disk appears to be inclined by 31.7d+/-1.6d from face-on, with the disk major-axis P.A. at 107deg+/-2deg. The total 1.1 mum flux density of the light scattered by the disk (at 1.2"<r<5.0") of 9.6+/-0.8 mJy is 0.17%+/-0.015% of the starlight. Seventy percent of the light from the scattering grains appears to be confined in a 36 AU wide annulus centered on the peak of the radial surface brightness (SB) profile 86.3+/-3.9 AU from the star, well beyond the characteristic radius of thermal emission estimated from IRAS and Spitzer flux densities, assuming blackbody grains (~22 AU). The 1.1 mum light scattered by the ring (1) appears bilaterally symmetric, (2) exhibits directionally preferential scattering well represented by a Henyey-Greenstein scattering phase function with gHG=0.30+/-0.03, and (3) has a median SB (over all azimuth angles) at the 86.3 AU radius of peak SB of 1.00+/-0.07 mJy arcsec-2. No photocentric offset is seen in the ring relative to the position of the central star. A low SB diffuse halo is seen in the NICMOS image to a distance of ~4". Deeper 0.6 mum Hubble Space Telescope (HST) ACS PSF-subtracted coronagraphic observations reveal a faint (V~21.5 mag arcsec-2) outer nebulosity at 4''<r<9'', asymmetrically brighter to the north of the star. We discuss models of the disk and properties of its grains, from which we infer a maximum vertical scale height of 4-8 AU at the 87.6 AU radius of maximum surface density, and a total maximum dust mass of collisionally replenished grains with minimum grain sizes of ~1 mum of ~4MMoon.
Free Keywords:Stars: Circumstellar Matter; Infrared: Stars; Stars: Planetary Systems: Protoplanetary Disks; stars: individual (HD 181327)
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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