Astrometry of OH/IR Stars Using 1612 MHz Hydroxyl Masers. I. Annual Parallaxes of WX Psc and OH138.0+7.2
Abstract
We report on the measurement of the trigonometric parallaxes of 1612 MHz hydroxyl masers around two asymptotic giant branch stars, WX Psc and OH 138.0+7.2, using the NRAO Very Long Baseline Array with in-beam phase referencing calibration. We obtain a 3σ upper limit of ≤5.3 mas on the parallax of WX Psc, corresponding to a lower limit distance estimate of ≳190 pc. The obtained parallax of OH 138.0+7.2 is 0.52 ± 0.09 mas (±18%), corresponding to a distance of {1.9}-0.3+0.4 {kpc}, making this the first hydroxyl maser parallax below one milliarcsecond. We also introduce a new method of error analysis for detecting systematic errors in the astrometry. Finally, we compare our trigonometric distances to published phase-lag distances toward these stars and find a good agreement between the two methods.
- Publication:
-
The Astronomical Journal
- Pub Date:
- March 2017
- DOI:
- 10.3847/1538-3881/153/3/119
- arXiv:
- arXiv:1701.05101
- Bibcode:
- 2017AJ....153..119O
- Keywords:
-
- astrometry;
- masers;
- stars: AGB and post-AGB;
- stars: individual: WX Psc;
- OH 138.0+7.2;
- techniques: interferometric;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Instrumentation and Methods for Astrophysics
- E-Print:
- Preprint, accepted for publication in The Astronomical Journal (January 17, 2017)