The Position of Sgr A${}^{\ast }$ at the Galactic Center

Abstract

The absolute position of the compact radio source at the dynamical center of the Galaxy, Sgr A${}^{\ast }$, was known only to an accuracy of $0.2^{\prime \prime }$ in spite of its accurate location with respect to near-IR stellar sources to within 30 milliarcsecond (mas). To remedy this poor positional accuracy, we have selected 15 high-resolution, high-frequency VLA observations of Sgr A${}^{\ast }$ carried out in the last 13 years and determined the weighted average position with the average epoch 1992.4 to be at $\alpha$, $\delta$[1950] = $17^{\mathrm{h}}42^{\mathrm{m}}$ 29\dsec3076$\pm 0.0007$, $-28^{\circ }59^{\prime }18.484\pm 0.014^{\prime \prime }$, or $\alpha$, $\delta$[2000] = $17^{\mathrm{h}}45^{\mathrm{m}}$ 40\dsec0383$\pm 0.0007$, $-29^{\circ }00^{\prime }28.069\pm 0.014^{\prime \prime }$ which agrees with earlier published values to within the $0.2^{\prime \prime }$ error bars of the earlier measurements. An accurate absolute position of Sgr A${}^{\ast }$ can be useful for its identification with sources at other wavelengths, particularly, in soft and hard X-rays with implications for the models of a massive black hole at the Galactic center.

11 pages, one figure and one table. ApJL (in press)

References in corpus (1)

• High Proper Motion Stars in the Vicinity of Sgr A*: Evidence for a Supermassive Black Hole at the Center of Our Galaxy

Cited by in corpus (18)

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• HST Paschen alpha and 1.9 micron imaging of Sgr A West
• A New X-Ray Flare from the Galactic Nucleus Detected with the XMM-Newton Photon Imaging Cameras
• X-ray Echo from the Sagittarius C Complex and 500-year Activity History of Sagittarius A*
• Repeated X-ray Flaring Activity in Sagittarius A*
• The X-ray flaring properties of Sgr A* during six years of monitoring with Swift
• Observing the Galaxy's massive black hole with gravitational wave bursts
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• An X-Ray Face-on View of the Sgr B Molecular Clouds Observed with Suzaku
• Compact Radio Sources within 30" of Sgr A*: Proper Motions, Stellar Winds and the Accretion Rate onto Sgr A*
• Expectations for extreme-mass-ratio bursts from the Galactic Centre
• ALMA and VLA observations of emission from the environment of Sgr A*
• Position and Proper Motion of Sagittarius A* in the ICRF3 Frame from VLBI Absolute Astrometry
• A Milliarcsecond-accurate Position for Sagittarius A*
• A New X-Ray Flare from the Galactic Nucleus Detected with the XMM-Newton