Pulsars(rotating neutron stars) and black holes are two possible outcomes when a large star is burned up and implodes. When there’s enough mass, you get a black hole. When there is less, you can get a neutron star: all mass converted to neutrons, as tightly packed as possible. When it rotates, it’s rotation frequency is observable as a train of pulses. A quasar is essentially a galaxy, (long ago and far away), with a supermassive black hole at it’s center. The black hole swallows a lot of mass, causing a lot of high energy radiation, which is how why in the beginning they were mistaken for strange quasi-stars, hence the name.
I was going to ask whether the article was using the term "pulsar" when "neutron star" would have been more accurate; I would have said that a pulsar was a rotating neutron star with a beam that intermittently points at Earth (making the distinction observer-specific).
But don't essentially all neutron stars spin? I don't know how a non-rotating neutron star might form. If that's the case, they could have just said "neutron star", and I wouldn't then have this issue about the subjectivity of what a pulsar is.
Almost certainly, though they do slow down over time. The distinction is indeed observer-specific, which doesn't matter yet, but will eventually matter for things like the "galactic positioning system" that sometimes gets suggested as a galaxy-wide extension of the current research on pulsar-based_navigation: https://en.wikipedia.org/wiki/Pulsar-based_navigation
The neutron stars that the article uses to explain the observed antimatter all must spin to cause the radiation observed. They would appear as pulsars to some observer, not necessarily us here on earth.
To be clear, neutron stars and back holes do not contain all of the mass of the star they were created by. Usually they are only created from the core of the star, but the outer layers get blown into space.
