SIMBAD references

We report a trigonometric parallax measurement of 22 GHz H₂O masers toward the semi-regular variable RT Vir from multi-epoch Very Long Baseline Array observations. The parallax of 4.417 ± 0.134 mas, corresponding to a distance of 226 ± 7 pc, is significantly different from the Hipparcos parallax, but is consistent with a distance derived from the period-luminosity relation (PLR). This suggests that the Hipparcos parallax suffers from systematic bias, possibly owing to a variable photo-center for this giant star. As such, VLBI parallax measurements will serve as an important cross-check for Gaia. Combing our RT Vir parallax with other long period variable parallaxes, we find a Galactic PLR at an infrared K band of M_K=-3.52logP+(1.10±0.08), assuming that the slope of the Large Magellanic Cloud relation is the same to that of our Galaxy.