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标题：The magnetically collimated jet of the evolved star W43A
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作者：W. Vlemmings ; P.J. Diamond ; H. Imai 等
期刊名称：PoS - Proceedings of Science
印刷版ISSN：1824-8039
出版年度：2006
出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：We present Very Long Baseline Array (VLBA) observations of the linear and circular polarization of the H2O masers in the collimated jet of W43A. The observations reveal a strong toroidal magnetic field, indicating that the jet is magnetically collimated. These are the first direct measurements of the magnetic field strength and direction in a collimated jet from an evolved star on its way to become a planetary nebula. The magnetic field strength in the jet extrapolated back to the stellar surface is fully consistent with the magnetic fields determined from SiO, H2O and OH maser polarization in a large sample of evolved stars. The origin of the magnetic field is yet unknown, although the jet precession might point to the existence of a heavy planet or stellar companion. Our observations thus provide strong evidence for magnetic collimation in the jets, that likely play an important role in shaping planetary nebulae.