Probing Circumstellar Disks and Outflows with Spectropolarimetry

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Session 49 -- Interstellar Dust and Polarization
Display presentation, Tuesday, 10, 1995, 9:20am - 6:30pm

[49.07] Probing Circumstellar Disks and Outflows with Spectropolarimetry

K.S. Bjorkman (U. Wisconsin)

Polarimetry, especially polarimetric imaging, has already proven to be a useful method for studying circumstellar disks around pre-main sequence stars. Spectropolarimetry of these objects shows promise of being equally useful, although only limited samples of such data are available at present. In pre-main-sequence stars, where the polarization mechanism is wavelength-dependent dust scattering in an equatorial disk plus electron scattering in polar regions, comparison of UV and optical spectropolarimetry can provide evidence of bi-polar outflows and of inhomogeneities in accretion disks and proto-planetary systems. Modeling of the position angle changes from the optical to the UV can give information about the relative densities of polar and equatorial material, as well as clues to the nature of the dust.

As part of a multi-spectral effort to investigate Herbig Ae/Be stars, we have begun to obtain spectropolarimetric observations of some bright pre-main-sequence stars in the optical (from the Pine Bluff Observatory - PBO) and ultraviolet (from the Wisconsin Ultraviolet Photo-Polarimeter Experiment - WUPPE). Data on HD45677, a suspected pre-main-sequence object, show evidence for a bipolar outflow geometry (Schulte-Ladbeck et al 1993; Grady et al 1994). Optical data on several Herbig Ae/Be stars show evidence for polarimetric variability. These data will be presented and discussed along with plans for future observations, including the second flight of WUPPE aboard the Astro-2 mission, and prospects for observations of fainter objects using larger telescopes.

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