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Making movies of stars: VLBA monitoring of the SiO masers around the Mira variable TX Cam

Published online by Cambridge University Press:  25 May 2016

P. J. Diamond
Affiliation:
NRAO, PO Box 0, Socorro, NM, 87801, USA
A. J. Kemball
Affiliation:
NRAO, PO Box 0, Socorro, NM, 87801, USA

Abstract

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We have produced a movie of the time evolution of the v=1, J=1−0 43 GHz SiO masers in the inner circumstellar envelope of the isolated Mira variable TX Cam. Our observations, taken every two weeks with the VLBA, currently cover about 60% of the stellar cycle from ϕ ∼ 0.6 → ϕ ∼ 1.2. They show that, in contrast to previous observations and theoretical models, the gas in which the masers are embedded is undergoing expansion during this period with a typical velocity of 3.65 ± 0.15 km/s. Some isolated features are seen to start falling back towards the star at around ϕ ∼ 1.0. We suggest that the 5 → 10 G magnetic fields we have previously detected at the position of the SiO masers may explain the departure from the expected behaviour.

Type
Part 2. Pulsation, Mass Loss, Cool Envelopes
Copyright
Copyright © Astronomical Society of the Pacific 1999 

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