Grant-in-Aid for Scientific Research (A)
|Research Institution||National Astronomical Observatory|
SASAO Tetsuo NAO,Division of Earth Rotation, Professor, 地球回転研究系, 教授 (20000177)
MIYOSHI Makoto NAO,Division of Earth Rotation, Assistant, 地球回転研究系, 助手 (50270450)
SHIBATA Katsunori NAO,Division of Earth Rotation, Assistant, 地球回転研究系, 助手 (60222030)
KAMEYA Osamu NAO,Mizusawa Astrogeodynamics Observatory, Assistant, 水沢観測センター, 助手 (70202025)
HARA Tadayoshi NAO,Division of Earth Rotation, Professor, 地球回転研究系, 助教授 (60000171)
KAWANO Nobuyuki NAO,Division of Earth Rotation, Professor, 地球回転研究系, 教授 (10186116)
|Project Fiscal Year
1995 – 1997
Completed(Fiscal Year 1997)
|Budget Amount *help
¥36,600,000 (Direct Cost : ¥36,600,000)
Fiscal Year 1997 : ¥2,900,000 (Direct Cost : ¥2,900,000)
Fiscal Year 1996 : ¥2,700,000 (Direct Cost : ¥2,700,000)
Fiscal Year 1995 : ¥31,000,000 (Direct Cost : ¥31,000,000)
|Keywords||maser source / differential VLBI / fast switching / annual parallax / Project VERA / star formation / phase compensation / J-net / メーサー源 / 相対VLBI法 / 高速スイッチング法 / 年周視差 / VERA計画 / 星生成 / 大気位相補償 / 国内VLBI網 / メーザー源 / VLBI / 基準電波源 / 視線速度変化 / クエ-サ / 相対VLBI / 位置天文 / メ-ザ源|
Results of present research as summarized below clearly confirmed feasibility of the the high-precision Galactic astorometry aimed at in VERA (VLBI Exploration of Radio Astrometry) Project.
(1) Search for Reference Radio Sources
Statistical survey using radio-source catalogs and VLBI observations showed that at least one compact and bright enough reference-source candidate is normally found within 2 degrees from any target source.
(2) Physical Properties of Maser Sources
Domestic VLBI observations revealed existence of water maser spots around late-type stars which are not resolved with 1000km baseline, surviving longer than a half year and, therefore, suited to VLBI astrometry. Systematic shift (acceleration) in line-of-sight velocity of the stellar maser spots was detected for the first time. New maser spots were discovered in Ori-KL sar-forming region which are almost aligned along the symmetry axis of the bipolar outflow and possibly associated with the jet-activity of the central youn
g stellar object.
(3) Test Observation for Maser Astrometry
Fringe-phase-difference observable was successfully detected between two adjacent quasars at 22 GHz in a switching differential VLBI experiment carried out with Japanese domestic VLBI Network (J-net).
(4) Compensation of Atmospheric Phase Fluctuations
Experiments using Nobeyama Millimeter Array and numerical simulations based on a statistical model of the turbulent troposphere demonstrated high performance expected in the phase compensation by means of the differential VLBI provided that the target and reference sources are separated by no more than a few degrees.
The simulations also revealed effectiveness of the phase compensation in terms of the fast-switching defferential VLBI with the switching cycle of 10-20 second at observing frequency up to 22-43 GHz.
(5) Estimation of Astrometric Accuracy
Estimated accuracy of the annual parallax determination with VERA array based on a model simulation was better than 10 microarcsecond for a pair of point-like maser and quasar sources observed in favorable atmospheric conditions. Less