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VLBI Observations of Water Masers in the Circumstellar Envelope of IRC+60169

H. Sudou·T. Omodaka·H. Imai·T. Sasao·H. Takaba·M. Nishio·W. Hasegawa·J. Nakajima
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Abstract

Water masers around an AGB star, IRC+60169, were observed at four epochs using the Japanese VLBI networks. The distribution of the maser features is limited in a thick-shell region, which has inner and outer expansion velocities of 7 km/s and 14 km/s at radii of 25 mas and 120 mas, respectively. The distribution of the red-shifted features exhibits a ring-like structure, the diameter of which is 30 mas, and corresponds to the inner radius of the maser shell. This implies that dense gas around the star obscures red-shifted emission. Although a position--radial velocity diagram for the maser features is consistent with a spherical shell model, the relative proper motions do not indicate an expansion motion of the shell. A remarkable property has been found that is a possible periodic change of the alignment pattern of water maser spots.

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H. Sudou, T. Omodaka, H. Imai, T. Sasao, H. Takaba, M. Nishio, W. Hasegawa, J. Nakajima. 2002-08-21. VLBI Observations of Water Masers in the Circumstellar Envelope of IRC+60169. https://doi.org/10.1093/pasj%2F54.5.757

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