Astronomy and Astrophysics – Astronomy
Scientific paper
Mar 1991
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1991mnras.249..227c&link_type=abstract
Monthly Notices of the Royal Astronomical Society (ISSN 0035-8711), vol. 249, March 15, 1991, p. 227-240.
Astronomy and Astrophysics
Astronomy
39
Hydroxyl Emission, Interstellar Masers, Mira Variables, Stellar Envelopes, Stellar Evolution, Astronomical Spectroscopy, Stellar Mass Ejection, Stellar Motions
Scientific paper
The Jodrell Bank MERLIN array was used to map the OH 1665- and 1667-MHz masers in the circumstellar envelope of U Orionis in 1984, 1986 and 1987. The OH masers lie within a region of extent 130 x 180 sq AU, and have complex distributions which are different for each line and polarization. The masers show clumpy structures with a typical clump size of about 25 AU. The strongest emission is from a ring of radius 60 AU which is interpreted as part of an expanding, tilted torus. The ring has a proper motion of 5.4 + or - 1.4 mas/yr corresponding to a transverse expansion velocity of 7 km/s for the period-luminosity distance to U Orionis of 260 pc. This expansion velocity is also indicated by a compact blueshifted maser spot which lies near the projected stellar position. OH maser emission is also detected from a redshifted filament which appears to project over a considerable radial depth in the envelope and varies in intensity in an erratic fashion.
Chapman Jessica M.
Cohen Richard J.
Saikia D. J.
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