1,165 research outputs found
VLBI Observations of Water Masers in the Circumstellar Envelope of IRC+60169
Water masers around an AGB star, IRC+60169, were observed at four epochs
using the Japanese VLBI networks. The distribution of the maser features is
limited in a thick-shell region, which has inner and outer expansion velocities
of 7 km/s and 14 km/s at radii of 25 mas and 120 mas, respectively. The
distribution of the red-shifted features exhibits a ring-like structure, the
diameter of which is 30 mas, and corresponds to the inner radius of the maser
shell. This implies that dense gas around the star obscures red-shifted
emission. Although a position--radial velocity diagram for the maser features
is consistent with a spherical shell model, the relative proper motions do not
indicate an expansion motion of the shell. A remarkable property has been found
that is a possible periodic change of the alignment pattern of water maser
spots.Comment: 9 pages including 7 figures, to appear in PASJ, Vol. 54, No.
Sub-parsec-scale Accleration of the Radio Jet in the Powerful Radio Galaxy NGC 6251
In order to investigate the genesis of powerful radio jet, we have mapped the
central 10 pc region of the nearby radio galaxy NGC 6251 with a 0.2 pc
resolution using Very Long Baseline Interferometer (VLBI) at two radio
frequencies, 5 GHz and 15 GHz, we have found the sub-parsec-scale counterjet
for the first time in this radio galaxy. This discovery allows us to
investigate the jet acceleration based on the relativistic beaming model.Comment: 7 pages with 7 figures. To appear in PASJ, 52, No. 5, Oct. 25, 200
Distance of W3(OH) by VLBI annual parallax measurement
The most powerful tool for measuring distances within our Galaxy is the
annual parallax. We carried out phase-referencing VLBI observations of HO
masers in the star forming region W3(OH) with respect to the extragalactic
continuum source ICRF 0244+624 to measure their absolute proper motions. The
measured annual parallax is 0.484 0.004 milli-arcseconds which
corresponds to a distance of 2.07^{+0.01}_{-0.02}$ kpc from the sun. This
distance is consistent with photometric and kinematic distances from previous
observations.Comment: Proceedings of the 7th European VLBI Network Symposium (October 12-15
2004, Toledo, Spain), eds. Bachiller, R., Colomer, F., Desmurs, J. F., & de
Vicente, P., 4 pages, 4 figures, needs evn2004.cl
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