Spectropolarimetric clues to the structure and evolutionary status of MWC 349A

摘要

We present visible wavelength spectropolarimetric measurements of the emission-line star MWC 349A and its close optical companion MWC 349B, conducted with the HPOL spectropolarimeter on both the 0.9 m telescope at the University of Wisconsin's Pine Bluff Observatory and the 3.5 m WIYN telescope on Kitt Peak. Our measurements allow us to estimate the interstellar polarization contribution and thus constrain the intrinsic polarization of MWC 349A, which we find to be consistent in position angle with the dusty disk seen perpendicular to the bipolar outflow. Our analysis reopens the possibility that MWC 349A may be part of the Cyg OB2 association, suggests that it is not a physical companion to MWC 349B, and supports the classification of MWC349A as a premain-sequence Be star. References: 29