Radiation — in the form of photons — can't easily escape from hydrogen on the pulsar's surface. (discovermagazine.com)
That means they can not undergo the type of collisions that dissipate energy (or hardly any collisions at all) the way ordinary particles do, primarily turning kinetic energy into electromagnetic energy, in the form of photons. (scientificamerican.com)
At the same time, some of the energy is absorbed by the colliding atoms, then reradiated in the form of photons, or particles of light. (discovermagazine.com)