AAS 207th Meeting, 8-12 January 2006
Session 9 Circumstellar Disks I
Poster, Monday, 9:20am-7:00pm, January 9, 2006, Exhibit Hall

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[9.05] Few Skewed Results from IOTA Interferometer YSO Disk Survey

J. D. Monnier (U. Michigan), R. Millan-Gabet (Michelson Science Center), J.-P. Berger (Laboratoire d'Astrophysique de Grenoble), E. Pedretti (U. Michigan), W. Traub (Jet Propulsion Laboratory), F. P. Schloerb (U. Massachusetts, Amherst)

The 3-telescope IOTA interferometer is capable of measuring closure phases for dozens of Herbig Ae/Be stars in the near-infrared. The closure phase unambiguously identifies deviations from centro-symmetry (i.e., skew) in the brightness distribution, at the scale of 4 milliarcseconds (sub-AU physical scales) for our work. Indeed, hot dust emission from the inner circumstellar accretion disk is expected to be skewed for (generic) flared disks viewed at intermediate inclination angles, as has been observed for LkHa 101. Surprisingly, we find very little evidence for skewed disk emission in our IOTA3 sample, setting strong constraints on the geometry of the inner disk. In particular, we rule out the currently-popular model of a VERTICAL hot inner wall of dust at the sublimation radius. Instead, our data is more consistent with a curved inner wall that bends away from the midplane as might be expected from the pressure-dependence of dust sublimation or limited absorption of stellar luminosity in the disk midplane by gas.

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