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Probing pulsar winds using inverse Compton scattering |
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| Authors: | Lewis Ball J G Kirk |
| Institution: | a Research Centre for Theoretical Astrophysics, University of Sydney, N.S.W. 2006, Australia b Max-Planck-Institut für Kernphysik, Postfach 10 39 80, D-69029, Heidelberg, Germany |
| Abstract: | We investigate the effects of inverse Compton scattering by electrons and positrons in the unshocked winds of rotationally-powered binary pulsars. This process can scatter low energy target photons to produce gamma rays with energies from MeV to TeV. The binary radio pulsars PSR B1259−63 and PSR J0045−73 are both in close eccentric orbits around bright main sequence stars which provide a huge density of low energy target photons. The inverse Compton scattering process transfers momentum from the pulsar wind to the scattered photons, and therefore provides a drag which tends to decelerate the pulsar wind. We present detailed calculations of the dynamics of a pulsar wind which is undergoing inverse Compton scattering, showing that the deceleration of the wind of PSR B1259−63 due to ‘inverse Compton drag' is small, but that this process may confine the wind of PSR J0045−73 before it attains pressure balance with the outflow of its companion star. We calculate the spectra and light curves of the resulting inverse Compton emission from PSR B1259−63 and show that if the size of the pulsar wind nebula is comparable to the binary separation, then the γ-ray emission from the unshocked wind may be detectable by atmospheric Cherenkov detectors or by the new generation of satellite-borne γ-ray detectors such as INTEGRAL and GLAST. This mechanism may therefore provide a direct probe of the freely-expanding regions of pulsar winds, previously thought to be invisible. |
| Keywords: | Pulsars Inverse Compton scattering Gamma-rays Cherenkov telescopes Pulsars: individual (PSR B1259−63 PSR J0045−73) |
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