出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：Using the VLBA we have observed at six epochs H2O maser emission in the pre-planetary nebula
IRAS 19134+2131 (I19134), in which the water maser spectrum has two groups of emission
features separated in radial velocity by »100 km s−1. The spatio-kinematical structure of the
H2O masers indicates the existence of a fast, collimated (precessing) flow with an expansion
velocity of »90 km s−1 and a dynamical age of only »40 years. Such a “water fountain” source
is a signature of the recent operation of a stellar jet, that may be responsible for the final shape
of the planetary nebula into which I19134 is expected to evolve. Because the positions of all
detected maser features have been measured with respect to the extragalactic reference source
J1925+2106 over one year, we analyzed maser feature motions that consist of an annual parallax,
a secular motion following the Galactic rotation and the intrinsic motions by the flow. We obtained
an annual parallax distance to I19134, D = 8.0+0.9
−0.7 kpc and estimated the location of I19134 in
the Galaxy, (R,q , z) =(7.4+0.4
−0.3 kpc, 62±±5±, 0.65+0.07
−0.06 kpc). From a mean motion of the blueshifted
and red-shifted clusters of maser features, we estimated the 3-D secular motion of I19134,
(VR,Vq ,Vz) = (6+53
−46,123+20
−28,−11+39
−48) [km s−1]. We discuss the origin of I19134 on the basis of
its kinematics in the Galaxy.
