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Death Line of Gamma-ray Pulsars with Outer Gaps

Image Credit: Ren-Bo Wang and Kouichi Hirotani

Outer-gap death line on the period vs. derivative period plane. Left: entire parameter space. Right: close-up of the millisecond parameter range.

By the advent of Fermi space observatory, the number of rotation-powered, gamma-ray pulsars has been increased from seven to more than one hundred. Thus, it is desired to derive a theoretical condition for a pulsar to become a gamma-ray emitter in a wide pulsar parameter space. On these grounds, we derived the death line (red, solid line) of high-energy pulsars on the period versus period-derivative plane, by analyzing the condition for an outer-magnetospheric accelerator to be maintained by photon-photon pair productions. The thin dotted lines express the parameter region that gives the labeled magnetic-field strength at the light cylinder. The (blue) large points denote the gamma-ray detected pulsars, whereas the (green) small open circles the X-ray detected ones. The entire parameter space is depicted in the left panel, while a close up of millisecond parameter range is depicted in the right panel. This theoretical prediction (red line) is being testified by various X-ray and gamma-ray observations. (Ren-Bo Wang and Kouichi Hirotani, ApJ 2011 736, 127 )