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Astron. Astrophys. 343, 801-805 (1999)

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A decade of unchanged 1.3 cm VLBI structure of Sgr A*

J.M. Marcaide 1, A. Alberdi 2, L. Lara 2, M.A. Pérez-Torres 1 and P.J. Diamond 3

1 Departamento de Astronomía, Universitat de València, E-46100 Burjassot, Spain
2 Instituto de Astrofísica de Andalucía, CSIC, Apdo. 3004, Granada, Spain
3 National Radio Astronomy Observatory, P.O. Box 0, Socorro, NM 87801, USA

Received 13 July 1998 / Accepted 20 November 1998

Abstract

We observed Sgr A* at 1.3 cm on 1992 November 8 with a 14 station VLBI array and, using data from 10 of these stations, obtained a high-dynamic range image with a beam of 3.35[FORMULA]1.7 milliarcseconds in position angle [FORMULA]. The observed surface brightness distribution of Sgr A* is best modelled by an elliptically shaped gaussian component with parameter values: flux density [FORMULA] Jy, major axis of FWHM [FORMULA] milliarcseconds in position angle [FORMULA], and axial ratio [FORMULA], which are almost the same as the estimates of Alberdi et al. (1993). We found no evidence of changes in the source structure of Sgr A* among four sets of 1.3 cm VLBI observations spanning almost a decade. It seems reasonable to conclude that both the emission of Sgr A* itself and the surrounding medium acting as a refractive screen have reasonably constant relative orientation, emission rates and structures.

Key words: galaxies: jets – Galaxy: center – techniques: interferometric

Send offprint requests to: J.M. Marcaide (jmm@vlbi.uv.es)

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© European Southern Observatory (ESO) 1999

Online publication: March 1, 1999
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