콜로퀴움
Parallax Measurements of the Mira-Type Star UX Cygni with Phase-Referencing VLBI 2008-02-21
- Speaker : Dr. Tomoharu Kurayama (Mizusawa VERA Observatory, NAOJ, Japan)
- Date : 2008-02-21 16:00 ~ 17:30
We have measured the annual parallax of the Mira-type variable star UX Cygni to be (pi) = 0.54 +/- 0.06 mas from phase-referencing VLBI observations of its circumsteller water masers with the VLBA. This is the first parallax from water maser observations. These are also the pilot observations for VERA (VLBI Exploration for Radio Astrometry) project in Japan, which measure the parallaxes and proper motions of galactic maser sources to reveal the three-dimensional structure of the Galaxy. <br /><br />
<br /><br />
Four epoch monitoring observations of water masers around the Mira-type star UX Cygni are carried out. The motions of maser spots referred to the position of phase-referencing source show the common annual parallax and proper motions of each spots. From the least-square fitting, the annual parallax is 0.54 +/- 0.06 mas. The corresponding distance is 1.85 (+0.25/-0.19) kpc. This result is consistent with the period-luminosity relation <br /><br />
(PLR) of Mira-type variables in P > 420 days. From this result and the PLR of Large Magellanic Cloud, we can derive the distance to the Large Magellanic Cloud to be <br /><br />
55.0 (+9.0/-7.2) kpc, which is consistent to the values from other methods. We can also get the three-dimensional position and velocity in the Galaxy. These results show <br /><br />
the possibility of astrometric observations with phase-referencing VLBI and research into galactic kinematics which is one of the big target of the VERA.
<br /><br />
Four epoch monitoring observations of water masers around the Mira-type star UX Cygni are carried out. The motions of maser spots referred to the position of phase-referencing source show the common annual parallax and proper motions of each spots. From the least-square fitting, the annual parallax is 0.54 +/- 0.06 mas. The corresponding distance is 1.85 (+0.25/-0.19) kpc. This result is consistent with the period-luminosity relation <br /><br />
(PLR) of Mira-type variables in P > 420 days. From this result and the PLR of Large Magellanic Cloud, we can derive the distance to the Large Magellanic Cloud to be <br /><br />
55.0 (+9.0/-7.2) kpc, which is consistent to the values from other methods. We can also get the three-dimensional position and velocity in the Galaxy. These results show <br /><br />
the possibility of astrometric observations with phase-referencing VLBI and research into galactic kinematics which is one of the big target of the VERA.