The Parallax of the Red Hypergiant VX Sgr with Accurate Tropospheric Delay Calibration

@article{Xu2018ThePO,
  title={The Parallax of the Red Hypergiant VX Sgr with Accurate Tropospheric Delay Calibration},
  author={Shuangjing 敬 Xu 徐双 and Bo 波 Zhang 张 and Mark J. Reid and Karl M. Menten and Xingwu 武 Zheng 郑兴 and Guangli 利 Wang 王广},
  journal={The Astrophysical Journal},
  year={2018},
  volume={859}
}
We report astrometric results of VLBI phase-referencing observations of 22 GHz H2O masers emission toward the red hypergiant VX Sgr, one of most massive and luminous red hypergiant stars in our Galaxy, using the Very Long Baseline Array. A background source, J1820−2528, projected 4.°4 from the target VX Sgr, was used as the phase reference. For the low decl. of these sources, such a large separation normally would seriously degrade the relative astrometry. We use a two-step method of… 

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