Monitoring the Crab Nebula with Chandra:A Search for the Location of the   gamma-ray Flares
  Subsequent to announcements by the AGILE and by the Fermi-LAT teams of the discovery of gamma-ray flares from the Crab Nebula in the fall of 2010, an international collaboration has been monitoring X-Ray emission from the Crab on a regular basis using the Chandra X-Ray Observatory. Observations occur typically once per month when viewing constraints allow. The aim of the program is to characterize in depth the X-Ray variations within the Nebula, and, if possible, to much more precisely locate the origin of the gamma-ray flares. In 2011 April we triggered a set of Chandra Target-of-Opportunity observations in conjunction with the brightest gamma-ray flare yet observed. We briefly summarize the April X-ray observations and the information we have gleaned to date. 
Martin C. Weisskopf
astro-ph.HE