The Sgr B2 X‐Ray Echo of the Galactic Center Supernova Explosion that Produced Sgr A East

Abstract

Using a combination of one-dimensional and three-dimensional hydrodynamic simulations, we have carried out the first in-depth analysis of the remnant's evolution and its various interactions: with the stellar winds flowing out from the inner ~2 pc; with the supermassive black hole, Sgr A*; and with the 50 km s-1 molecular cloud behind and to the east of the nucleus. We have found that, unlike previous estimates, a rather "standard" supernova explosion with energy ~1.5 × 1051 ergs would have been sufficient to create the remnant we see today and that the latter is probably only ~1700 yr old. We have found that the passage of the remnant across the black hole would have enhanced the accretion rate onto the central object by less than a factor of 2. Such a small increase cannot explain the current Fe fluorescence observed from the molecular cloud Sgr B2; this fluorescence would have required an increase in the luminosity of Sgr A* by 6 orders of magnitude several hundred years ago. Instead, we have uncovered what appears to be a more plausible scenario for this transient irradiation: the interaction between the expanding remnant and the 50 km s-1 molecular cloud. The first impact would have occurred about 1200 yr after the explosion, producing a 2-200 keV luminosity of ~1039 ergs s-1. During the intervening 300-400 yr, the dissipation of kinetic energy subsided considerably, leading to the much lower luminosity (~1036 ergs s-1 at 2-10 keV) we see today.