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Issue A&A Volume 432, Number 2, March III 2005 Page(s) L39 - L42 Section Letters DOI 10.1051/0004-6361:200500015

A&A 432, L39-L42 (2005)
DOI: 10.1051/0004-6361:200500015

Letter

First VLBI mapping of circumstellar SiO maser emission

R. Soria-Ruiz¹, F. Colomer², J. Alcolea¹, V. Bujarrabal², J.-F. Desmurs¹ and K. B. Marvel<sup>3

1</sup>  Observatorio Astronómico Nacional, Alfonso XII 3, 28014 Madrid, Spain
    e-mail: r.soria@oan.es
²  Observatorio Astronómico Nacional, Apartado 112, 28803 Alcalá de Henares, Spain
³  American Astronomical Society, 2000 Florida Avenue, NW Suite 400, Washington, DC 20009-1231, USA

(Received 15 December 2004 / Accepted 27 January 2005)

Abstract
We report the first VLBI map of the v=0 J= 1-0 maser line of ²⁹SiO in the long-period variable star IRC +10011. We have found that this maser emission is composed of multiple spots distributed in an incomplete ring, suggesting that this maser is also amplified tangentially, as already proposed in other SiO circumstellar masers. We present also VLBI maps for the 7 mm ²⁸SiO v=1 and 2 J= 1-0 and the 3 mm v=1 J= 2-1 lines. The ²⁹SiO masing region appears to be located in a layer in between the ²⁸SiO v=1 J= 1-0 and ²⁸SiO v=1 J= 2-1 lines. In addition, we confirm that the 86 GHz maser v=1 J= 2-1 forms in an outer region of the circumstellar envelope compared to the other ²⁸SiO masers studied. Finally, we discuss the possible implications of the observational results on the SiO maser pumping theory.

Key words: radio lines: stars -- masers -- technique: interferometric -- stars: circumstellar matter -- stars: AGB

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© ESO 2005

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