No Microwave Flare of Sagittarius A* around the G2 Periastron Passing

TL;DR

This study monitored Sagittarius A* at 22 GHz over 18 months around the G2 cloud's periastron passage, finding no significant microwave flare or flux increase during this period.

Contribution

It provides the first extensive radio flux monitoring of Sgr A* during G2's periastron, showing no detectable enhancement in microwave emission.

Findings

No significant microwave flare detected during G2 periastron

Average flux density consistent with typical Sgr A* levels

Extended monitoring constrains models predicting G2-induced activity

Abstract

In order to explore any change caused by the G2 cloud approaching, we have monitored the flux density of Sgr A* at 22 GHz from Feb. 2013 to Aug. 2014 with a sub-array of Japanese VLBI Network . The observation period included the expected periastron dates. The number of observation epochs was 283 days. We have observed no significant microwave enhancement of Sgr A* in the whole observation period. The average flux density in the period is $S=1.23+/-0.33$ Jy. The average is consistent with the usually observed flux density range of Sgr A* at 22 GHz.