A Milliarcsecond-accurate Position for Sagittarius A*

Abstract

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) = $17^{\mathrm{h}}45^{\mathrm{m}}40{.}^{\mathrm{s}}032863\pm 0{.}^{\mathrm{s}}000016$ and $\delta$(J2000) = $-29^{\circ }00^{\prime }28{.}^{{}^{\prime \prime }}24260\pm 0{.}^{{}^{\prime \prime }}00047$, 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.

9 pages, 2 figures, accepted by ApJ

References in corpus (5)

• Trigonometric Parallaxes Of High-Mass Star Forming Regions: Our View Of The Milky Way
• DiFX: A software correlator for very long baseline interferometry using multi-processor computing environments
• Astrometric accuracy of phase-referenced observations with the VLBA and EVN
• Precise radio astrometry and new developments for the next generation of instruments
• The Galactic Center: An Improved Astrometric Reference Frame for Stellar Orbits around the Supermassive Black Hole