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Paper: Water Maser Microstructures in Cepheus A
Volume: 287, Galactic Star Formation Across the Stellar Mass Spectrum
Page: 373
Authors: Torrelles, J. M.; Patel, N. A.; Ho, P. T. P.; Greenhill, L.; Gómez, J. F.; Rodríguez, L. F.; Anglada, G.; Garay, G.; Curiel, S.; Cantó, J.
Abstract: We have recently reported three epochs of VLBA water vapor maser observations toward the star forming region Cepheus A. The VLBA data show that some of the masers detected previously with the VLA unfold into linear/arcuate continuous ``microstructures''. Both the flattened appearance and proper motions of the small ``building-blocks'' constituting the water maser structures show that these are likely shock fronts. One of the water maser microstructures defines an expanding (9 km/s) circle of 62 AU radius at the precision of one part in a thousand. We have interpreted this structure as due to a spherical ejection of material 33 years earlier from a protostar. The physical processes involved to produce such highly spherically symmetric ejection are not known yet.
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