Recall, most stars are born in binary systems. Just as we saw
Nova and Supernova being created from White Dwarfs in orbit around
Red Giants, Neutron Stars or Black Holes can become detected if they
have a binary companion willing to feed their enourmous gravitational
potential.
How a Supergiant Companion can effect a Neutron Star or Black Hole (compact object):
Material falling onto the compact object heats up to X-ray temperatures,
and is seen in X-ray Bursts from the system.
The material falling on to the compact object adds angular momentum, thereby spinning it
"up" (makes it look young again!).
The compact object may BURN AWAY its Stellar Companion!
More recently, PLANETS (big rocks) have been discovered around Pulsars!
(why do you suppose these were the FIRST planets discovered?)
