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Colloquium: From gamma-rays to radio: the quest to understand pulsars emission mechanisms

Submitter: Maura Pilia (ASTRON)
Description: I will present the detection of emission at energies E > 30 MeV from PSR B1509-58 and PSR B1846-0258 with the satellites AGILE and Fermi. PSR B1509-58 was detected by COMPTEL up to at least 10 MeV, while EGRET reported only marginal evidence (< 4 sigma) for a weak source. AGILE detected pulsed emission from PSR B1509-58 at 6.4 sigma. The COMPTEL sharp spectral break between 10 and 30 MeV seems confirmed by AGILE point implying a cutoff at E=80 MeV. PSR B1846-0258 in the SNR Kes 75, formerly considered a standard rotation powered pulsar recently showed magnetically induced behavior. Its magnetic field is ~5e13 G, above the critical quantum field a nd its cutoff E = 20 MeV.
Such low-energy breaks, compared to the more common GeV spectral break in gamma-ray pulsars, could be the signature of the photon splitting process inducing significant electromagnetic cascade attenuation due to the strong magnetic polar field (>1e13 G). Higher magnetic field pulsars have been observed in gamma-rays by Fermi, so that a concurrence of factors has to be invoked in order to explain the soft break. With the AGILE capability of observing with good sensitivity at E>30 MeV, we investigate these two highly magnetized pulsars as possible contributors to a new class of "soft" gamma-ray pulsars.
From the X-rays in particular has come a wealth of discoveries of pulsar classes which are all linked but, at the same time, still mostly divided.
Some intermediate cases are shown, which can help disentangling the common properties of high magnetic field pulsars.
Finally, some preliminary results by LOFAR will be presented, also aiming at the characterization of the properties that determine the different emission phenomena in pulsars.
Copyright: M. Pilia
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