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arXiv · 1701.05101

Astrometry of OH/IR stars using 1612 MHz hydroxyl masers. I. Annual parallaxes of WX Psc and OH138.0+7.2

G. Orosz·H. Imai·R. Dodson·M. J. Rioja·S. Frey·R. A. Burns·S. Etoka·A. Nakagawa·H. Nakanishi·Y. Asaki·S. R. Goldman·D. Tafoya
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Abstract

We report on the measurement of the trigonometric parallaxes of 1612 MHz hydroxyl masers around two asymptotic giant branch stars, WX Psc and OH138.0+7.2, using the NRAO Very Long Baseline Array with in-beam phase referencing calibration. We obtained a 3-sigma 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 OH138.0+7.2 is 0.52+/-0.09 mas (+/-18%), corresponding to a distance of 1.9(+0.4,-0.3) 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.

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G. Orosz, H. Imai, R. Dodson, M. J. Rioja, S. Frey, R. A. Burns, S. Etoka, A. Nakagawa, H. Nakanishi, Y. Asaki, S. R. Goldman, D. Tafoya. 2017-01-18. Astrometry of OH/IR stars using 1612 MHz hydroxyl masers. I. Annual parallaxes of WX Psc and OH138.0+7.2. https://doi.org/10.3847/1538-3881%2F153%2F3%2F119

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