These are Bill Wolf's notes for Andy Howell's PHYS 234: High Energy Astrophysics class, taught in the Spring of 2013 at UCSB. I try to update these after every class but will likely fall behind. If you could, please fork off this repo and add your own edits to make these notes even better! If you just want to download the pdf of the notes, go to 234-Notes.pdf and click "View Raw".