Astrometry of OH/IR Stars Using 1612MHz Hydroxyl Masers. I. Annual Parallaxes of WX Psc and OH138.0+7.2 MEConference on Why Galaxies Care About AGB Stars III: A Closer Look in Space and Time, JUL 28-AUG
Artikel i vetenskaplig tidskrift, 2017

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 3s 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.

agb stars




OH 138.0+7.2)

stars: AGB and post-AGB

vlbi astrometry



circumstellar oh masers

proper motions



stars: individual (WX Psc

Astronomy & Astrophysics


h2o masers


G. Orosz

Kagoshima University

H. Imai

Kagoshima University

R. Dodson

University of Western Australia

M. J. Rioja

Observatorio Astronomico Nacional

University of Western Australia

CSIRO Astronomy and Space Science

S. Frey

Konkoly Observatory Hungarian Academy of Sciences

R. A. Burns

Joint Institute for VLBI ERIC

Kagoshima University

S. Etoka

Universität Hamburg

A. Nakagawa

Kagoshima University

H. Nakanishi

SKA Organization

JAXA Institute of Space and Astronautical Science

Kagoshima University

Y. Asaki

National Institutes of Natural Sciences

Atacama Large Millimeter-submillimeter Array

S. R. Goldman

Keele University

Daniel Tafoya Martinez

Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik

Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium

Astronomical Journal

0004-6256 (ISSN) 1538-3881 (eISSN)

Vol. 153 119-


Astronomi, astrofysik och kosmologi


Grundläggande vetenskaper


Onsala rymdobservatorium