Discovery of an 86 AU Radius Debris Ring around HD 181327
Abstract
HST NICMOS PSF-subtracted coronagraphic observations of HD 181327 have revealed the presence of a ringlike disk of circumstellar debris seen in 1.1 μm 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°.7 ± 1°.6 from face-on, with the disk major-axis P.A. at 107° ± 2°. The total 1.1 μm 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 μm light scattered by the ring (1) appears bilaterally symmetric, (2) exhibits directionally preferential scattering well represented by a Henyey-Greenstein scattering phase function with g_HG = 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 μm 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 μm of ≈4M_(Moon).
Additional Information
© 2006 American Astronomical Society. Received 2005 December 31; accepted 2006 June 6. We are grateful to F. J. Low and P. S. Smith of the Spitzer GTO (PID 72) team for providing MIPS imaging photometry of HD 181327. We thank Elizabeth Stobie (NICMOS Project, University of Arizona) for her significant contributions to this program through her development, implementation, enhancement, and support of analysis software used throughout the course of this study. We appreciate the commentary received from Eric Mamajek, particularly in regard to the age estimation for HD 181327 beyond its "guilt by association" as a presumed member of the β Pictoris moving group, as reflected in our discussion in §§ 1 and 6.3 of this paper. This investigation was based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs GO10177 and GTO/9987. Support for program GO 10177 was provided by NASA through a grant from STScI. S. Wolf was supported by the German Research Foundation (DFG) through the Emmy Noether grant WO857/2-1. J.-C. Augereau, C. Pinte, and F. Ménard acknowledge financial support from the Programme National de Physique Stellaire (PNPS) of CNRS/INSU, France. We acknowledge the use of the SIMBAD database.Attached Files
Published - SCHNapj06.pdf
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Additional details
- Eprint ID
- 24495
- Resolver ID
- CaltechAUTHORS:20110721-114145893
- Space Telescope Science Institute
- WO857/2-1
- German Research Foundation (DFG)
- Programme National de Physique Stellaire (PNPS)
- Created
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2011-07-21Created from EPrint's datestamp field
- Updated
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2021-11-09Created from EPrint's last_modified field