The Galactic Center: An Improved Astrometric Reference Frame for Stellar Orbits around the Supermassive Black Hole

Abstract

Precision measurements of the stars in short-period orbits around the supermassive black hole at the Galactic Center are now being used to constrain general relativistic effects, such as the gravitational redshift and periapse precession. One of the largest systematic uncertainties in the measured orbits has been errors in the astrometric reference frame, which is derived from seven infrared-bright stars associated with SiO masers that have extremely accurate radio positions, measured in the Sgr A*-rest frame. We have improved the astrometric reference frame within 14'' of the Galactic Center by a factor of 2.5 in position and a factor of 5 in proper motion. In the new reference frame, Sgr A* is localized to within a position of 0.645 mas and proper motion of 0.03 mas/yr. We have removed a substantial rotation (2.25 degrees per decade), that was present in the previous less-accurate reference frame used to measure stellar orbits in the field. With our improved methods and continued monitoring of the masers, we predict that orbital precession predicted by General Relativity will become detectable in the next ~5 years.

17 pages, 10 figures

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Cited by in corpus (21)

• First Sagittarius A* Event Horizon Telescope Results. VI: Testing the Black Hole Metric
• Detection of the Schwarzschild precession in the orbit of the star S2 near the Galactic centre massive black hole
• Relativistic redshift of the star S0-2 orbiting the Galactic center supermassive black hole
• The mass distribution in the Galactic Centre from interferometric astrometry of multiple stellar orbits
• orvara: An Efficient Code to Fit Orbits using Radial Velocity, Absolute, and/or Relative Astrometry
• A hidden friend for the galactic center black hole, Sgr A*
• Search for a Variation of the Fine Structure around the Supermassive Black Hole in Our Galactic Center
• The dark mass signature in the orbit of S2
• Towards an observational test of black hole versus naked singularity at the galactic center
• The Galactic Center as a laboratory for theories of gravity and dark matter
• Constraining a companion of the galactic center black hole, Sgr A*
• Revised Astrometric Calibration of the Gemini Planet Imager
• Stellar Populations in the Central 0.5 pc of Our Galaxy III: The Dynamical Sub-structures
• Consistency of the Infrared Variability of Sgr A* over 22 years
• The Swansong of the Galactic Center Source X7: An Extreme Example of Tidal Evolution near the Supermassive Black Hole
• VaTEST II: Statistical Validation of 11 TESS-Detected Exoplanets Orbiting K-type Stars
• A Milliarcsecond-accurate Position for Sagittarius A*
• New Evidence for a Flux-independent Spectral Index of Sgr A* in the Near-infrared
• An adaptive scheduling tool to optimize measurements to reach a scientific objective: methodology and application to the measurements of stellar orbits in the Galactic Center
• The Galactic Center in Color: Measuring Extinction with High-Proper-Motion Stars
• 3D Kinematics of Stellar SiO Masers in the Galactic Center