nstar http://astro.uchicago.edu/home/web/miller/nstar.html
      http://antwrp.gsfc.nasa.gov/apod/ap960909.html

whitedwarfs http://antwrp.gsfc.nasa.gov/apod/ap950910.html

crab http://oposite.stsci.edu/pubinfo/PR/96/22.html