Observational support for radiative pumping of SiO masers in evolved stars |
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| Authors: | J -F Desmurs V Bujarrabal F Colomer J Alcolea |
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| Institution: | 1. Observatorio Astronómico Nacional (IGN), Apartado 1143, 28800 Alcalá de Henares, Spain;2. Joint Institute for VLBI in Europe, Postbus 2, 7990 AA Dwingeloo, The Netherlands;1. The University of Edinburgh, School of Engineering, United Kingdom;2. California Polytechnic State University – San Luis Obispo, Mechanical Engineering Department and Fire Protection Engineering Program, United States;3. Hydrock Consultants Ltd, Bristol, United Kingdom;1. School of Physics and Electronic Science, Guizhou Normal University, Guiyang 550025, China;2. Key Laboratory of Low Dimensional Condensed Matter Physics of Higher Educational Institution of Guizhou Province, Guizhou Normal University, Guiyang 550025, China;3. School of Science, Minzu University of China, Beijing 100081, China |
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| Abstract: | SiO maser emission in AGB stars is found to be systematically distributed in ring structures, displaying tangential linear polarization. Using the VLBA, we have performed observations of such SiO maser emission at 43 GHz in the circumstellar envelopes of several late-type stars. We simultaneously mapped the v=1 and v=2, J=1–0 transitions. Our new maps show, for most spots, a systematic spatial shift between both maser lines. We discuss the implication of these results on the possible pumping mechanisms, concluding that the existing data favour radiative pumping schemes. |
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| Keywords: | Radio: VLBI interferometry AGB stars Circumstellar masers SiO |
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