EDP Sciences
Free access
Volume 385, Number 1, April I 2002
Page(s) L1 - L4
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20020233

A&A 385, L1-L4 (2002)
DOI: 10.1051/0004-6361:20020233


Submilliarcsecond-resolution mapping of the 43 GHz SiO maser emission in the bipolar post-AGB nebula OH231.8+4.2

C. Sánchez Contreras1, 2, J. F. Desmurs1, V. Bujarrabal1, J. Alcolea1 and F. Colomer1

1  Observatorio Astronómico Nacional (OAN), Apdo. 1143, 28800 Alcalá de Henares, Spain
    e-mail: sanchez,bujarrabal,desmurs,j.alcolea,colomer@oan.es
2  Jet Propulsion Laboratory, California Institute of Technology, MS 183-900, 4800 Oak Grove Dr., Pasadena, CA 91109
    e-mail: sanchez@eclipse.jpl.nasa.gov

(Received 30 November 2001 / Accepted 11 February 2002)

We present ~0.3 milliarcsec-resolution maps of the SiO ( v=2, J=1-0) maser emission in the bipolar post-AGB nebula obtained with the Very Long Baseline Array. These observations have provided for the first time the structure and kinematics of the close stellar environment in a proto-Planetary Nebula. Our observations reveal the SiO maser emission arising in several bright spots of less than ~10 13 cm in size forming a structure elongated in the direction perpendicular to the symmetry axis of the nebula. Such a distribution is consistent with an equatorial torus with a radius of ~6 AU around the central star. A complex velocity gradient is found along the torus, which suggests rotation and infall of material towards the star. The rotation and infalling velocities deduced are of the same order and range between ~7 and ~10 km s -1. From our data, we estimate the mass of the SiO torus and the central star, as well as a stringent upper limit to the present stellar mass-loss rate.

Key words: masers -- stars: AGB and post-AGB -- stars: mass-loss -- circumstellar matter -- stars: individual: OH231.8+4.2 -- stars: variables: general

Offprint request: C. Sánchez Contreras, sanchez@eclipse.jpl.nasa.gov

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