Snapshot VLBI Observations of SiO v=1 and v=2 (J=1-0) Maser Sources

2001/04/25 by Hiroshi Imai, Makoto Miyoshi, Nobuharu Ukita +7
Engineering · Earth and Planetary Sciences · Physics and Astronomy · #GNSS positioning and interference #Geophysics and Gravity Measurements #Ionosphere and magnetosphere dynamics

paper · pdf · doi:10.1093/pasj/53.2.259

Abstract

Abstract We have made snapshot VLBI observations of SiO masers of the J= 1−0 transition at two vibrational levels v=1 and v=2 using the Kashima–Nobeyama Interferometer (KNIFE). Out of 37 sources observed, we detected both of the lines from 16 sources with a typical detection limit of 10 Jy. Most of the SiO masers were significantly spatially resolved with a KNIFE baseline (200 km), indicating extended/complicated structures of the SiO masers with a typical angular size of a few milliarcseconds. Similar fringe-phase profiles along a radial velocity spanning larger than 1.0~km~s^-1 between the two lines indicate a similar spatial structure along the velocity spacings. This tendency, shown from 13 SiO maser sources except Orion KL, supports spatial coincidence of the two lines found previously for M-type stars VY CMa and W Hya. The spatial coincidence should enable us to measure group-delays of the SiO masers for stellar astrometry.

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