Detecting Stars at the Galactic Centre via Synchrotron Emission

TL;DR

This paper proposes that stars near the Galactic Centre can be detected through their synchrotron emission caused by bow shocks, especially at pericenter, providing a new observational method despite obscuration.

Contribution

It introduces a novel approach to detect stars near Sgr A* via synchrotron emission, with calculations showing luminosity comparable to Sgr A* at certain frequencies.

Findings

Synchrotron emission from stars near Sgr A* can be detectable at radio and infrared frequencies.

The emission strength depends on orbital velocity and is maximized at pericenter.

Star S2 in 2018 is an ideal candidate for testing these predictions.

Abstract

Stars orbiting within 1$\arcsec$ of the supermassive black hole in the Galactic Centre, Sgr A*, are notoriously difficult to detect due to obscuration by gas and dust. We show that some stars orbiting this region may be detectable via synchrotron emission. In such instances, a bow shock forms around the star and accelerates the electrons. We calculate that around the 10 GHz band (radio) and at 10$^{14}$ Hz (infrared) the luminosity of a star orbiting the black hole is comparable to the luminosity of Sgr A*. The strength of the synchrotron emission depends on a number of factors including the star's orbital velocity. Thus, the ideal time to observe the synchrotron flux is when the star is at pericenter. The star S2 will be $\sim 0.015\arcsec$ from Sgr A* in 2018, and is an excellent target to test our predictions.