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arXiv · 1807.10332

Constraining Theories of SiO Maser Polarization: Analysis of a $pi$/2 EVPA Change

Taylor Tobin·Athol Kemball·Malcolm Gray
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Abstract

The full theory of polarized SiO maser emission from the near-circumstellar environment of Asymptotic Giant Branch stars has been the subject of debate, with theories ranging from classical Zeeman origins to predominantly non-Zeeman anisotropic excitation or propagation effects. Features with an internal electric vector position angle (EVPA) rotation of $\sim \pi /2$ offer unique constraints on theoretical models. In this work, results are presented for one such feature that persisted across five epochs of SiO $\nu=1, J=1-0$ VLBA observations of TX Cam. We examine the fit to the predicted dependence of linear polarization and EVPA on angle ($\theta$) between the line of sight and the magnetic field against theoretical models. We also present results on the dependence of $m_c$ on $\theta$ and their theoretical implications. Finally, we discuss potential causes of the observed differences, and continuing work.

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Taylor Tobin, Athol Kemball, Malcolm Gray. 2018-07-26. Constraining Theories of SiO Maser Polarization: Analysis of a $pi$/2 EVPA Change. https://doi.org/10.1017/s1743921317011486

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