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K. R. Stapelfeldt (Jet Propulsion Laboratory / Caltech), A. M. Watson (UNAM-Morelia), J. E. Krist (STScI), C. J. Burrows (STScI)
We report on continuing studies of the edge-on young stellar object accretion disk HH 30 using the WFPC2 cameras aboard the Hubble Space Telescope. Broadband filter images at five new epochs have been obtained during the past year, providing temporal sampling on spacings of 2, 13, 28, and 64 days. The variable asymmetry in the upper reflection nebula, first seen in 1998 (Ap.J. 516 L95), is present in all the new images but with a reduced lateral extent. There is no evidence for motion of the asymmetry on timescales of days or weeks; if its motion is periodic, a characteristic timescale on the order of 15 years is needed to match the nebula structure seen with HST between 1994-1999. This result appears to rule out beaming models tied to the stellar rotation period, and argues instead that the asymmetry arises from the beaming effects of disk inhomogeneities at radii near 5 AU. The dynamical influence of a low mass companion is an attractive means for creating and maintaining beaming through the disk, and we will present preliminary models exploring this possibility.
This work is supported by NASA under Hubble Space Telescope GO grant 6754 to the Jet Propulsion Laboratory.
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