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.

arXiv comment9 pages, 2 figures, accepted by ApJ

References in corpus (21)

• Astropy: A Community Python Package for Astronomy
• First Sagittarius A* Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way
• Monitoring stellar orbits around the Massive Black Hole in the Galactic Center
• Measuring Distance and Properties of the Milky Way's Central Supermassive Black Hole with Stellar Orbits
• A geometric distance measurement to the Galactic Center black hole with 0.3% uncertainty
• The Proper Motion of Sgr A*: II. The Mass of Sgr A*
• Trigonometric Parallaxes Of High-Mass Star Forming Regions: Our View Of The Milky Way
• Near-infrared flares from accreting gas around the supermassive black hole at the Galactic Centre
• First Light for GRAVITY: Phase Referencing Optical Interferometry for the Very Large Telescope Interferometer
• DiFX: A software correlator for very long baseline interferometry using multi-processor computing environments
• Micro-Arcsecond Radio Astrometry
• The Proper Motion of Sagittarius A*: III. The Case for a Supermassive Black Hole
• HST Paschen alpha and 1.9 micron imaging of Sgr A West
• Astrometric accuracy of phase-referenced observations with the VLBA and EVN
• Intrinsic Size OF Sgr A*: 72 Schwarzschild Radii
• II. Accurate Positions and Proper Motions of Stellar SiO Masers near the Galactic Center
• The Proper Motion of the Galactic Center Pulsar Relative to Sagittarius A*
• 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
• The Position of Sgr A${}^{\ast }$ at the Galactic Center
• ALMA Astrometry of the Objects within 0.5 pc of Sagittarius A${}^{\ast }$

Cited by in corpus (2)

• Searching Accretion-Enhanced Dark Matter Annihilation Signals in the Galactic Centre
• Trigonometric parallax and proper motion of Sagittarius A* measured by VERA using the new broad-band back-end system OCTAVE-DAS