Testing General Relativity with the Shadow Size of Sgr A(*).

Area of Science:

• Astrophysics
• General Relativity
• Black Hole Physics

Background:

• Black hole shadow size is mainly determined by mass and distance in general relativity.
• Deviations from general relativity could significantly alter black hole shadow size.

Purpose of the Study:

• To assess the capability of the Event Horizon Telescope (EHT) in measuring the angular radius of Sagittarius A*'s black hole shadow.
• To investigate the potential for improving mass and distance measurements and constraining deviations from the Kerr metric.

Main Methods:

• Utilizing a reconstructed image of Sagittarius A* from a simulated seven-station EHT observing run.
• Employing a Markov chain Monte Carlo algorithm to analyze the shadow size.

Main Results:

• Demonstrated the ability to measure the angular radius of Sagittarius A*'s shadow with an uncertainty of approximately 1.5 microarcseconds (6%).
• Showed that EHT measurements can significantly improve existing mass and distance estimates.

Conclusions:

• Upcoming EHT observations of Sagittarius A*'s shadow will provide precise measurements.
• These measurements will yield tight constraints on potential deviations from the Kerr metric, testing general relativity in the strong-field regime.