Astronomy and Astrophysics – Astrophysics
Scientific paper
Mar 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001crlrv..47...31i&link_type=abstract
Review of the Communications Research Laboratory, vol. 47, p. 31
Astronomy and Astrophysics
Astrophysics
Emission Spectra, Water Vapor, Stellar Evolution, Interstellar Masers, Massive Stars, Astrophysics, Infrared Astronomy Satellite, Protostars, Radial Velocity, Semiregular Variable Stars, Supergiant Stars, Very Long Base Interferometry
Scientific paper
Cosmic-maser emission from water vapor has been observed at an early stage of birth and at the final stage of death in stellar evolution. We have observed such water masers using the Japanese domestic VLBI network for astronomy (J-Net), and revealed in detail the kinematics of them around protostars and evolved stars: (1) Systematic radial-velocity drifts of water-maser features in time were found around the semiregular variable star RT Vir. This phenomenon, discovered for the first time, indicates acceleration motions of a mass-loss flow around the star. (2) Rotation-infall motions around the protostar IRAS 16923-2422 in the solar-system scale were revealed with water masers. These motions indicated dynamical infalls of material on to the protostar in a scale down to a few tens of AU. (3) A large number of proper motions of water-maser features have been measured in the massive-star forming region W51 North. We found 3-D kinematics of an outflow from W51 North and estimated directly a distance to W51 North as 6.7 +/- 2.1 kpc. and (4) We started study of the high precision astrometry of maser sources to develop stellar astrophysics. The phase-referencing technique using the fast antenna-switching method has been applied to a pair of water masers around the supergiant star S Per and the continuum source KR 143. Although an accuracy of relative astrometry for the maser sources was limited to 1 mas at the present work, the fringe-phase fluctuation due to the atmosphere has been compensated effectively at the relatively high frequency band of 22.2GHz.
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