Signatures of an Encounter Between the G2 Cloud and a Jet from Sgr A*

TL;DR

The paper models the potential X-ray and radio signatures resulting from the G2 cloud's encounter with a jet from Sgr A*, predicting observable brightening and spectral changes that can confirm such an interaction.

Contribution

It provides the first detailed predictions of X-ray and radio emission signatures from the G2 cloud's interaction with Sgr A*'s jet, guiding future observational efforts.

Findings

X-ray luminosity could increase up to 10 times the quiescent flux of Sgr A*

Peak emission may emit approximately 3 solar luminosities above 10 keV

Radio emission could reach levels of a few Jansky

Abstract

The recent discovery of the G2 cloud of dense, ionized gas on a trajectory toward Sgr A*, the black hole at the dynamical center of the Galaxy, offers a unique opportunity to observe an accretion event onto a massive black hole as well as to probe its immediate environment. Simulations and models predict increased X-ray and radio variability resulting from increased accretion driven by drag on an atmosphere of hot, X-ray emitting gas surrounding Sgr A*. Here, we present X-ray and radio light curves of the emission resulting from the potential encounter of the G2 cloud with a relativistic jet from Sgr A*. This interaction would violently shock a portion of the G2 cloud to temperatures $\sim 10^8$\,K resulting in bright X-ray emission from the dense, shocked gas as it adiabatically expands. The 2-10\, keV luminosity may reach $\sim$10 times the quiescent X-ray flux of Sgr A*. approximately $3\,\lsol$ is emitted above 10\,keV at the peak of the light curve, with significant softening of the spectrum occurring as the gas subsequently cools. Observations with NuSTAR would therefore be able to confirm such an event as well as determine the cloud speed. At radio wavelengths, the associated synchrotron radio emission may reach levels of a few Jy.