57 research outputs found
Implication of the period-magnitude relation for massive AGB stars and its astronomical applications
We present astrometric very long baseline interferometry (VLBI) studies of
AGB stars. To understand the properties and evolution of AGB stars, distances
are an important parameter. The distribution and kinematics of their
circumstellar matter are also revealed with the VLBI method. We used the VERA
array to observe 22\,GHz HO masers in various subclasses of AGB stars.
Parallaxes of the three OH/IR stars NSV17351, OH39.71.5, IRC30363, and
the Mira-type variable star AW~Tau were newly obtained. We present the
circumstellar distribution and kinematics of HO masers around NSV17351. The
absolute magnitudes in mid-infrared bands of OH/IR stars with very long
pulsation periods were investigated and a period-magnitude relation in the WISE
W3 band, , was found
for the Galactic AGB stars. The VLBI is still a powerful tool for parallax
measurements of the Galactic AGB stars surrounded by thick dust shells.Comment: 24 pages, 8 figures, Proceedings of the IAU symposium 376, At the
cross-roads of astrophysics and cosmology Period luminosity relations in the
2020
VLBI Observations of Water Masers in Onsala 1: Massive Binary Star Forming Site?
We present proper motions of water masers toward the Onsala 1 star forming
region, observed with the Japanese VLBI network at three epochs spanning 290
days. We found that there are two water maser clusters (WMC1 and WMC2)
separated from each other by 1".6 (2900 AU at a distance of 1.8 kpc). The
proper motion measurement reveals that WMC1 is associated with a bipolar
outflow elongated in the east-west direction with an expansion velocity of
69+-11 km/s. WMC1 and WMC2 are associated with two 345 GHz continuum dust
emission sources, and located 2" (3600 AU) east from the core of an
ultracompact HII region traced by 8.4 GHz radio continuum emission. This
indicates that star formation activity of Onsala 1 could move from the west
side of ultracompact HII region to the east side of two young stellar objects
associated with the water masers. We also find that WMC1 and UC HII region
could be gravitationally bound. Their relative velocity along the line of sight
is 3 km/s, and total mass is 37 Mo. Onsala 1 seems to harbor a binary star at
different evolutionary stage.Comment: 9 pages, 4 figures, accepted for PAS
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