3 research outputs found
Astrometric VLBI observations of HO masers in an extreme OH/IR star candidate NSV17351
Results of astrometric very long baseline interferometry (VLBI) observations
towards an extreme OH/IR star candidate NSV17351 are presented. We used the
VERA (VLBI Exploration of Radio Astrometry) VLBI array to observe 22\,GHz
HO masers of NSV17351. We derived an annual parallax of 0.2470.035 mas
which corresponds to a distance of 4.050.59 kpc. By averaging the proper
motions of 15 maser spots, we obtained the systemic proper motion of NSV17351
to be () (1.19
0.11, 1.30 0.19) mas\,yr. The maser spots spread out over a
region of 20 mas 30 mas, which can be converted to a spatial
distribution of 80 au 120 au at the source distance.
Internal motions of the maser spots suggest an outward moving maser region with
respect to the estimated position of the central star. From single dish
monitoring of the HO maser emission, we estimate the pulsation period of
NSV17351 to be 112224 days. This is the first report of the periodic
activity of NSV17351, indicating that NSV17351 could have a mass of
4\,M. We confirmed that the time variation of HO masers can
be used as a period estimator of variable OH/IR stars. Furthermore, by
inspecting dozens of double-peaked HO maser spectra from the last 40 years,
we detected a long-term acceleration in the radial velocity of the
circumstellar matter to be km\,s\,yr Finally, we
determined the position and kinematics of NSV17351 in the Milky Way Galaxy and
found that NSV17351 is located in an interarm region between the Outer and
Perseus arms. We note that astrometric VLBI observations towards extreme OH/IR
stars are useful samples for studies of the Galactic dynamics.Comment: Published in the Publications of the Astronomical Society of Japa
Correlation between degree of hallux valgus and kinematics in classical ballet: A pilot study.
Hallux valgus is a serious medical concern for classical ballet dancers. Although it is well-known that progression of hallux valgus is related to inappropriate movement techniques in classical ballet, the kinematic relationship between the degree of hallux valgus and ballet techniques has not been substantiated. To develop proper training methods that prevent progression of hallux valgus, this study aimed to investigate the relationship between the degree of hallux valgus and movement techniques in classical ballet. Seventeen female classical ballet dancers at the advanced college-level participated in this study. Kinematic analysis of standing and plié in the first position was conducted via video capture technique. The Pearson product-moment correlation analysis was performed to examine the degree of hallux valgus and the following three kinematic variables: (1) the extent to which turnout is forced by other joints in the lower extremity than the hip joint, (2) the direction difference between the knee and toe in the transverse plane, and (3) the pelvis obliquity angle. Among these kinematic variables, we found a significant correlation between the hallux valgus angle and the pelvis obliquity angle during plié (P = .045). The greater the hallux valgus angle, the greater the retroversion of the pelvis, a result which was contrary to our prediction. We present the first evidence that the degree of hallux valgus correlates with kinematics in a very basic technique of classical ballet