Vol. 558
In section 6. Interstellar and circumstellar matter

Echoes of multiple outbursts of Sagittarius A* revealed by Chandra

by M. Clavel, R. Terrier, A. Goldwurm, et al., A&A 558, A32


The supermassive black hole located in the center of our Galaxy, Sgr A*, is known to be variable. In a paper published this week, Clavel et al. use Chandra high-resolution data collected from 1999 to 2011 to study the most rapid variations detected in the region so far, namely variations from clouds between 5 and 20 arcmin from SgrA*, allowing these authors to characterize variations down to a 15 arcsec angular scale and a 1-year time scale. Their study reveals for the first time abrupt variations of only a few years, which they suggest are caused by the reflection of a luminous episode of hard X-ray emission that is most likely due to the past activity of Sgr A*. The timing of the complex illumination pattern is key for spotlighting the simultaneity in the illuminated cloud and therefore for constraining the relative positions of the clouds in this very special region of the Milky Way.