Caustic Echoes as X-ray follow-ups from Sagittarius A


The supermassive black hole Sgr A* at the center of our Galaxy is a source of bright X-ray flares. In certain cases, the bright flares are followed up by weaker ones, also referred to as X-ray hiccups. A recent X-ray Visionary Project (XVP) using the High Energy Transmission Grating Spectrometer (HETGS) of the Chandra X-ray Observatory is expected to observe about three dozen X-ray flares within 2012, thereby providing a unique opportunity to understand the mechanism behind X-ray flares in accretion disks around supermassive black holes and their follow-ups. Such follow-ups may also appear due to caustic echoes. A bright flare near the event horizon of a black hole leads to the formation of a caustic on the other side of the horizon. The echoes generated by these caustics may, in principle, be detected as X-ray follow-ups with sufficiently accurate instruments. Their detection would allow us to measure the …

American Astronomical Society Meeting Abstracts# 221