The high-energy reject rate on Chandra ACIS-S3 over the course of the mission. This metric traces variability in the particle background, which occurs on a range of timescales. The effects of the 11-year Solar cycle are clearly seen.

Movie of raw frames from the Chandra ACIS-I3 CCD. Each frame is a 3.3-second integration, and virtually all the visible signal is due to high-energy cosmic rays.

Current and past team members were instrumental in the development, fabrication, testing, and calibration of the Advanced CCD Imaging Spectrometer (ACIS) flying on the Chandra X-ray Observatory, and current members continue to monitor and calibrate this instrument more than 20 years after launch. The figures to the right show examples of monitoring we perform to understand variability in the particle background and its effect on science observations. More details on monitoring and calibration can be found at the following links:

• Catherine Grant’s ACIS page
• Grant et al. 2014. Fifteen years of the Advanced CCD Imaging Spectrometer
• Images of recent ACIS raw frames

We work closely with the Chandra HETG Group led by Prof. Claude Canizares, with Prof. Michael McDonald’s extragalactic group, and with Prof. Erin Kara’s black hole group, combining to form a large, active high-energy astrophysics research group at MKI. The interests of this group span a broad range including the evolution and physics of galaxy clusters, AGN and X-ray binaries, X-ray active stars, supernova remnants, and more.