Pulsar "lighthouse" model more complicated
Deep in the cloud of dust and gas of Crab Nebula (shown here) is the Crab Pulsar, the remains of an exploded star once 8-12 times as massive as our Sun. The Crab Pulsar has a high-energy output among pulsars, yet emits only weak gamma rays. PSR B1055-52, a much older pulsar, is too weak to be imaged in optical light, yet produces high-energy gamma rays more efficiently than Crab. This is one example of how pulsars are more complicated than astronomers once sought.
Credit: Bill Schoening, AURA/NOAO/NSF
Multiwavelength light curves for PSR B1055-52. This plot shows at different wavelengths how the brightness of the pulsar varies as the neutron star rotates. The two complete rotations of the neutron star shown here last about four-tenths of a second. If the pulsar were a simple "lighthouse", the bright peaks would all occur at the same time. Instead, the pulsar is brightest at different times depending on the type of observation. The vertical dashed line shows the time when the pulsar is brightest in the radio. From the bottom panel, it can be seen that the high-energy gamma rays arrive a fraction of a second earlier.
CREDIT: David Thompson, et.al., ApJ vol. 516
This chart shows the efficiency in which gamma-ray pulsars convert their spin energy into gamma rays. Like a veteran artisan who grows more accomplished with age, pulsars seem to get more efficient at generating gamma rays with time. More data are needed, however, to confirm this trend -- for the seven pulsars shown here are the only ones known to produce gamma rays.
Credit: David Thompson, et.al.
