Time-dependent absorption of very high-energy gamma-rays from the Galactic center by pair-production

TL;DR

This paper introduces a novel method to explore the association of VHE gamma-ray emissions from the Galactic center with Sgr A* by analyzing time- and energy-dependent gamma-ray absorption due to pair-production with nearby stellar photons.

Contribution

The study presents a new approach using pair-production absorption effects to link VHE gamma-ray sources with the environment of Sgr A*, overcoming positional uncertainty challenges.

Findings

Proposes a method to connect VHE gamma-ray emissions with Sgr A* using pair-eclipse effects.

Highlights the difficulty of precise localization of gamma-ray sources at the Galactic center.

Suggests potential for future observations to identify gamma-ray source counterparts.

Abstract

Very high energy (VHE) gamma-rays have been detected from the direction of the Galactic center. The H.E.S.S. Cherenkov telescopes have located this gamma-ray source with a preliminary position uncertainty of 8.5" per axis (6" statistic + 6" sytematic per axis). Within the uncertainty region several possible counterpart candidates exist: the Super Massive Black Hole Sgr A*, the Pulsar Wind Nebula candidate G359.95-0.04, the Low Mass X-Ray Binary-system J174540.0-290031, the stellar cluster IRS 13, as well as self-annihilating dark matter. It is experimentally very challenging to further improve the positional accuracy in this energy range and therefore, it may not be possible to clearly associate one of the counterpart candidates with the VHE-source. Here, we present a new method to investigate a possible link of the VHE-source with the near environment of Sgr A* (within approximately 1000 Schwarzschild radii). This method uses the time- and energy-dependent effect of absorption of gamma-rays by pair-production (in the following named pair-eclipse) with low-energy photons of stars closely orbiting the SMBH Sgr A*.