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- Title
Trigonometric parallax and proper motion of Sagittarius A* measured by VERA using the new broad-band back-end system OCTAVE-DAS.
- Authors
Oyama, Tomoaki; Nagayama, Takumi; Yamauchi, Aya; Sakai, Daisuke; Imai, Hiroshi; Honma, Mareki; Asakura, Yu; Hada, Kazuhiro; Hagiwara, Yoshiaki; Hirota, Tomoya; Jike, Takaaki; Kono, Yusuke; Suzuki, Syunsaku; Kobayashi, Hideyuki; Kawaguchi, Noriyuki
- Abstract
We successfully measured the trigonometric parallax of Sagittarius A* (Sgr A*) to be 117 ± 17 micro-arcseconds (|$\, \mu \mbox{as}$|) using the VLBI Exploration of Radio Astrometry (VERA) with the newly developed broad-band signal-processing system named "OCTAVE-DAS." The measured parallax corresponds to a Galactocentric distance at the Sun of |$R_0 = 8.5^{+1.5}_{-1.1}\:$| kpc. By combining the astrometric results with VERA and the Very Long Baseline Array (VLBA) over a monitoring period of 25 yr, the proper motion of Sgr A* is obtained to be (μα, μδ) = (−3.133 ± 0.003, −5.575 ± 0.005) mas yr−1 in equatorial coordinates, corresponding to (μ l , μ b ) = (−6.391 ± 0.005, −0.230 ± 0.004) mas yr−1 in Galactic coordinates. This gives an angular orbital velocity of the Sun of Ω⊙ = 30.30 ± 0.02 km s−1 kpc−1. We find upper limits to the core wander, Δθ < 0.20 mas (1.6 au), peculiar motion, Δμ < 0.10 mas yr−1 (3.7 km s−1), and acceleration, a < 2.6 |$\, \mu \mbox{as} \:$| yr−2 (0.10 km s−1 yr−1) for Sgr A*. Thus, we obtained upper mass limits of |$\approx 3 \times 10^{4}\, M_{\odot }$| and |$\approx 3 \times 10^{3}\, M_{\odot }$| for the supposed intermediate-mass black holes at 0.1 and 0.01 pc from the Galactic center, respectively.
- Subjects
PARALLAX; ORBITAL velocity; GALACTIC center; ANGULAR velocity; BLACK holes
- Publication
Publications of the Astronomical Society of Japan, 2024, Vol 76, Issue 2, p163
- ISSN
0004-6264
- Publication type
Article
- DOI
10.1093/pasj/psad088