No microwave flare of Sagittarius A∗ around the G2 periastron passing

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 2013 February to 2014 August with a sub-array of the Japanese Very Long Baseline Interferometry 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 Sv = 1.23 ± 0.33 Jy. The average is consistent with the usually observed flux density range of Sgr A∗ at 22 GHz.