Astron. Astrophys. 339, 897-903 (1998)

Stellar positions from SiO masers in the Galactic center

Loránt O. Sjouwerman ^{1, 2, 3}, Huib Jan van Langevelde ³ and Philip J. Diamond <sup>4

1</sup> Onsala Rymdobservatorium, S-439 92 Onsala, Sweden
² Sterrewacht Leiden, P.O. Box 9513, 2300 RA Leiden, The Netherlands
³ Joint Institute for VLBI in Europe, P.O. Box 2, 7990 AA Dwingeloo, The Netherlands
⁴ N.R.A.O. Array Operations Center, P.O. Box 0, Socorro, NM 87801, USA

Received 5 February 1998 / Accepted 10 September 1998

Abstract

We report on the possibility of determining milli-arcsecond accurate positions (relative to Sgr A*) for 43 GHz SiO masers located at the Galactic center. The SiO masers were found in OH/IR stars in a previous Very Large Array survey. We used the Very Long Baseline Array and the phased Very Large Array in a phase-referencing scheme with a cycle time of 40 seconds. The continuum source Sgr A* is used as phase-reference source. Because of the atmospheric phase instability at 43 GHz and sensitivity considerations, only 2 sources (from 10) were detected. However, we show that reliable positions can be obtained with calculable errors, which allows one to measure the proper motion of these stars accurate to 30 in 5 years.

Key words: techniques: interferometric astrometry stars: kinematics stars: AGB and post-AGB Galaxy: kinematics and dynamics

Send offprint requests to: L.O. Sjouwerman (at JIVE in Dwingeloo), (sjouwerm@jive.nfra.nl)

SIMBAD Objects

Contents

• 1. Introduction
• 2. Observations
  • 2.1. May 1995 - VLBA test observations
  • 2.2. VLBA and phased VLA observations - December 1995, January 1996
  • 2.3. Data reduction
• 3. Results
  • 3.1. Detections
  • 3.2. Non-Detections
  • 3.3. Positional accuracy
• 4. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 1998

Online publication: October 22, 1998
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