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M. D. Perrin (UC Berkeley), D. T. Gavel (Lawrence Livermore National Laboratory), E. L. Gates (UCO/Lick Observatory), J. R. Graham, P. Kalas, J. D. Larwood (UC Berkeley), J. P. Lloyd, C. E. Max, D. M. Pennington (CalTech)
We have obtained high spatial resolution near-IR imaging polarimetry of several Herbig Ae/Be stars using the Laser Guide Star adaptive optics (AO) system at Lick Observatory. We present here our observations of three of these objects: LkH\alpha 198, LkH\alpha 225, and LkH\alpha 233. Herbig Ae/Be stars are young intermediate-mass stars, whose detailed nature is not as well understood as that of the lower-mass T Tauri stars. AO polarimetry enables us to probe circumstellar dust and outflows at high spatial resolution and dynamic range; the use of the Lick Observatory/LLNL laser guide star system enables observations of these distant and heavily visually extincted targets which could not otherwise be observed with AO.
We find a bipolar structure ~ 10 arcsec in extent oriented north-south surrounding LkH\alpha 198, perpendicular to a dark lane suggestive of an edge-on circumstellar disk. The infrared companion 6 arcsec north illuminates nebulosity oriented in the NW-SE direction and may be the best candidate for driving CO outflow in the region. The two stellar components of the binary LkH\alpha 225 show complex circumstellar structures that resemble tidal arms. Our polarimetric observations establish that the material is illuminated in scattered light from LkHa 225 and is thus physically associated with the binary. The observed morphology may be explained by tidal interactions between circumstellar disks during a close encounter of these stars. LkH\alpha 233 presents a narrow, unpolarized lane separating its characteristic X-shaped reflection nebulosity. This dark lane is oriented perpendicular to a jet and the bipolar cavity and may represent an optically thick circumstellar disk that blocks our direct view of the star at wavelengths shorter than 2.2 micron. This work has been supported by the NSF Center for Adaptive Optics.
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.