Tatsuya Kamezaki

VLBI Astrometry of the Semiregular Variable RX Bootis

We present distance measurements of the semiregular variable RX Bootis (RX Boo) with its annual parallax. Using the unique dual-beam system of the VLBI Exploration of Radio Astrometry (VERA) telescope, we conducted astrometric observations of a water maser spot accompanying RX Boo, referred to the quasar J1419+2706 separated by 1. i 69 from RX Boo. We measured the annual parallax of RX Boo to be 7.31 ˙ 0.50 mas, corresponding to a distance of 136 +10 � 9 pc, from one-year monitoring observation data of one maser spot at VLSR = 3.2 km s � 1 .T he distance, itself, is consistent with that obtained with Hipparcos. The distance uncertainty was reduced by a factor of two, allowing us to determine the stellar properties more accurately. Using our distance, we discuss the location of RX Boo in various sequences of Period-Luminosity (PL) relation. We found that RX Boo is located in the Mira sequence of the PL relation. In addition, we calculated the radius of the photosphere and the mass limitation of RX Boo, and evaluated its evolutionary status.

VLBI Observations of H2O Maser Annual Parallax and Proper Motion in IRAS 20143+3634: Reflection on the Galactic Constants

We report the results of VLBI observations of H2O masers in the IRAS 20143+3634 star forming region using VERA (VLBI Exploration of Radio Astronomy). By tracking masers for a period of over two years we measured a trigonometric parallax of � = 0.367±0.037 mas, corresponding to a source distance of D = 2.72 +0.31 −0.25 kpc and placing it in the Local spiral arm. Our trigonometric distance is just 60% of the previous estimation based on radial velocity, significantly impacting the astrophysics of the source. We measured proper motions of 2.99±0.16 mas yr −1 and 4.37±0.43 mas yr −1 in R.A. and Decl. respectively, which were used to estimate the peculiar motion of the source as (Us,Vs,Ws)=( 0.9±2.9, 8.5±1.6,+8.0±4.3) km s −1 for R0 = 8 kpc and �0 = 221 km s −1 , and (Us,Vs,Ws) = ( 1.0±2.9, 9.3±1.5,+8.0±4.3) km s −1 for R0 = 8.5 kpc and �0 = 235 km s −1 . IRAS 20143+3634 was found to be located near the tangent point in the Cygnus direction. Using our observations we derived the angular velocity of Galactic rotation of the local standard of rest (LSR), 0 = 27.3±1.6 km s −1 kpc −1 , which is consistent with previous values derived using VLBI astrometry of SFRs at the tangent points and Solar circle. It is higher than the value recommended by the IAU of 0 = 25.9 km s −1 kpc −1 which was calculated using the Galactocentric distance of the Sun and circular velocity of the LSR.

STAR FORMATION IN THE MOLECULAR CLOUD ASSOCIATED WITH THE MONKEY HEAD NEBULA: SEQUENTIAL OR SPONTANEOUS?

We mapped the (1,1), (2,2), and (3,3) lines of NH3 toward the molecular cloud associated with the Monkey Head Nebula (MHN) with a 1. � 6 angular resolution using a Kashima 34 m telescope operated by the National Institute of Information and Communications Technology (NICT). The kinetic temperature of the molecular gas is 15–30 K in the eastern part and 30–50 K in the western part. The warmer gas is confined to a small region close to the compact Hii region S252A. The cooler gas is extended over the cloud even near the extended Hii region, the MHN. We made radio continuum observations at 8.4 GHz using the Yamaguchi 32 m radio telescope. The resultant map shows no significant extension from the Hα image. This means that the molecular cloud is less affected by the MHN, suggesting that the molecular cloud did not form by the expanding shock of the MHN. Although the spatial distribution of the Wide-field Infrared Survey Explorer and Two Micron All Sky Survey point sources suggests that triggered low- and intermediate-mass star formation took place locally around S252A, but the exciting star associated with it should be formed spontaneously in the molecular cloud.

Trigonometric parallax of IRAS 22555+6213 with VERA: Three-dimensional view of sources along the same line of sight

We report the results of the measurement of the trigonometric parallax of an H

ASTROMETRY OF IRAS 22555+6213 WITH VERA: A 3-DIMENSIONAL VIEW OF SOURCES ALONG THE SAME LINE OF SIGHT

_2

ASTROMETRIC OBSERVATION OF MIRA VARIABLES WITH VERA

O maser source in \r22 with the VLBI Exploration of Radio Astrometry (VERA). The annual parallax was determined to be 0.314

VLBI astrometry of the semi-regular variable star RX Bootis

\pm

VLBI Observations and NH3 Mapping of the Star-forming Region NGC2264

0.070~mas, corresponding to a distance of 3.18

Infrared observation of Mira variables and their galactic distribution

^{+0.90}_{-0.66}

Annual Parallax Determination toward a New X-Ray-emitting Class 0 Candidate with the Water Maser in the NGC 2264 Star-forming Region

~kpc. Our results confirm \r22 to be located in the Perseus arm. We computed the peculiar motion of \r22 to be