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Spectral energy distribution of pulsed emission from a middle-aged pulsar B1951+32

Image Credit: Hirotani

Spectral energy distribution of pulsed emission from a middle-aged pulsar B1951+32. The abscissa denotes photon energies in Million electron volts (MeV), while the ordinate denotes photon energy fluxes. The green solid line designates the theoretical pred

Over the last few decades, a great deal of effort has been made on detecting gamma-rays between 50,000 MeV and 10,000,000 MeV energies with Air Cherenkov Telescopes (ACTs), and severer constraints are being obtained for several gamma-ray pulsars, including B1951+32. As a result, the spectrum extrapolated from the Energetic Gamma-Ray Experiment Telescope (EGRET) observations (black dash-dotted line in Figure 2) is found to be overestimated. For example, the MAGIC experiment, a German ACT project, obtained very recently the upper limits indicated by the red solid line. The theoretical prediction (green line) is consistent with all existing data from 0.01eV (infrared energies) to 10,000,000 MeV (very high energy gamma-rays). The predicted turnover between 5,000 MeV and 30,000 MeV will be checked by the next-generation gamma-ray space telescope, GLAST, which will be launched in 2007 and capable of detecting gamma-ray photons up to 300,000 MeV.