We have performed VLBI and single-dish monitoring of 22 GHz H2O maser
emission from the high mass young stellar object G353.273+0.641 with VERA (VLBI
Exploration of Radio Astrometry) and Tomakamai 11-m radio telescope. Two maser
flares have been detected, separated almost two years. Frequent VLBI monitoring
has revealed that these flare activities have been accompanied by structural
change of the prominent shock front traced by H2O maser alignments. We have
detected only blue-shifted emissions and all maser features have been
distributed within very small area of 200 × 200 au2 in spite of
wide velocity range (> 100 km s−1). The light curve shows notably
intermittent variation and suggests that the H2O masers in G353.273+0.641
are excited by episodic radio jet. The time-scale of \sim2 yr and
characteristic velocity of \sim500 km s−1 also support this
interpretation. Two isolated velocity components of C50 (-53 \pm 7 km s−1)
and C70 (-73 \pm 7 km s−1) have shown synchronised linear acceleration of
the flux weighted V_{\rmn{LSR}} values (\sim-5 km s−1 yr−1) during
the flare phase. This can be converted to the lower-limit momentum rate of 1.1
\times 10−3 M_{\sun} km s−1 yr−1. Maser properties are quite
similar to that of IRAS 20126+4104 especially. This corroborates the previous
suggestion that G353.273+0.641 is a candidate of high mass protostellar object.
The possible pole-on geometry of disc-jet system can be suitable for direct
imaging of the accretion disc in this case.Comment: 13 pages, 5 figures accepted for publication in MNRA