A Milliarcsecond-accurate Position for Sagittarius A* by Shuangjing Xu et al. on Wednesday 23 November

The absolute position of Sgr A*, the compact radio source at the center of

the Milky Way, had been uncertain by several tens of milliarcseconds. Here we

report improved astrometric measurements of the absolute position and proper

motion of Sgr A*. Three epochs of phase-referencing observations were conducted

with the Very Long Baseline Array for Sgr A* at 22 and 43 GHz in 2019 and 2020.

Using extragalactic radio sources with submilliarcsecond-accurate positions as

reference, we determined the absolute position of Sgr A* at a reference epoch

2020.0 to be at $\alpha$(J2000) = $17^{\rm h} 45^{\rm m}40.^{\rm

s}032863~\pm~0.^{\rm s}000016$ and $\delta$(J2000) = $-29^{\circ} 00^{\prime}

28.^{''}24260~\pm~0.^{''}00047$, with an updated proper motion

$-3.152~\pm~0.011$ and $-5.586~\pm~0.006$ mas yr$^{-1}$ in the easterly and

northerly directions, respectively.

arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.03390v3