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C. A. Grady (Eureka Scientific and GSFC), G. Schneider, D. Potter, M. Silverstone (U. of Arizona), G. M. Williger (JHU and U. Louisville), B. Woodgate (NASA's GSFC), M. L. Sitko, W. J. Carpenter (U. Cincinnati), HST/GO 10177 Team
Since its identification as a Vega-like system, HD 169142 has attracted interest with its combination of PAH emission, an absence of warm silicate emission, and low near-IR luminosity. More recently, attention has focussed on the molecular gas content of the disk. With the identification of 2 apparently common proper motion companions, HD 169142 is now securely identified as an older Herbig Ae star with t=8+/-4 Myr. NICMOS coronagraphic observations confirm that the disk is viewed essentially face-on, and extends to at least 1.4" (200 AU) from the star, with background objects visible beyond 2" (290 AU). Like another older Herbig Ae star, HD 100546, the disk has a steep radial surface brightness distribution which can be fit by r-3 from 0.57-1.4" from the star with a peak surface brightness at 0.57" of 0.5 mJy per square arcsecond. The star lacks the high velocity wind component seen in the Herbig Ae stars which are driving bipolar microjets. Any UV excess is at least a factor of 5-10 fainter than for HD 104237. The low inferred accretion rate is consistent with the behavior of other Herbig Ae stars in the same nominal age range. However, the current accretion rate is inconsistent with sub-millimeter and millimeter estimates of the disk mass and molecular gas content, unless the inner portion of the disk is partially cleared. Limits on the degree of central clearing and the nature of any close stellar or sub-stellar companions will be discussed.
This work is based, in part, on observations made with the NASA/ESA Hubble SpaceTelescope, obtained at the STScI, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contrat NAS 5-26555. This study made use of data obtained as part of HST-GO-10177. Apache Point Observatory observations with the Goddard Fabry-Perot were made through a grant of Director's Discretionary Time. Apache Point Observatory is operated by the Astrophysical Research Consortium. The GFP was supported under NASA RTOP 51-188-01-22 to GSFC. Grady is partially supported under NASA contract NNH05CD30C to Eureka Scientific.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.