Eran Ofek of the Weizmann Institute is head of a team of researchers that has discovered the dying signature of stars. Just prior to becoming a supernova, stars emit gravity waves and eject up to one percent of their mass. The researchers studied a star, which became a supernova 40 days later.
http://wis-wander.weizmann.ac.il/observed-the-outburst-before-the-blast#.USOPh_L67hE