Special Astrophysics Seminar

HEFT measurement of the hard X-ray size of the Crab Nebula and the hard X-ray optics of the Nucelar Spectroscopic Telescope Array (NuSTAR)

Hongjun An

Columbia Astrophysics Laboratory
Columbia University

Hard X-ray focusing optics for astrophysical observations above 10 keV were first realized by the balloon-launched, High Energy Focusing Telescope (HEFT). HEFT used depth-graded multilayer coatings and novel techniques to form the glass and to mount the segmented glass to a conic approximation to the Wolter-I geometry. HEFT employed three hard X-ray focusing optics. It observed the hard X-ray sky for 24 hours, and successfully detected two very important astrophysical objects Cyg X-1 and the Crab Nebula. This is the first direct imaging measurement of the Crab spatial extent in hard X-rays, and we compare the result with theory. NuSTAR, the follow-on to HEFT, employs two hard X-ray focusing optics, and will test theories of how heavy elements are born, discover black holes on all mass scales and explore the most extreme physical environments. It will launch in Feb. 2012. In this talk, I will present the general concepts of hard X-ray focusing optics. I will discuss the Crab observations obtained with HEFT. And I will talk about the challenges we met in building the NuSTAR optics, and show how we solved them.