NIR triggered observations of Sgr A* at 43 GHz

Rauch, C.; Ros, E.; Krichbaum, T. P.; Eckart, A.; Zensus, J. A.; Lu, R.-S.; Shahzamanian, B.; Mužić, K.; Peißker, F.
The Multi-Messenger Astrophysics of the Galactic Centre, Proceedings of the International Astronomical Union, IAU Symposium, Volume 322, pp. 52-53 (2017).


The compact radio and near-infrared (NIR) source Sagittarius A* has been observed in the context of two NIR triggered global VLT and VLBA campaigns at 43 GHz (7 mm) on May 16-18 2012 and October 4 2014. While on October 4 2014 Sgr A* remained in a quiescent state, a NIR flare on May 17 2012 is accompanied by an increase in flux density of 0.22 Jy at 7 mm delayed by 4.5+/-0.5 h. Additionally, Sgr A* seems to develop a weak secondary radio off-core component of 0.02 Jy at a position angle of 140° and an angular distance of 1.5 mas shortly before the peak of the flare. This spatial extension and the time delay are in the range of expected values for events casually connected by adiabatic expansion.