Maura Pilia, Alberto Pellizzoni, for the AGILE Team
We present the results of 2.5 years of AGILE observations of PSR B1509-58 and
of the same interval of Fermi observations. The modulation significance of
AGILE light curve above 30 MeV is at a 5 sigma confidence level and the light
curve shows a broad asymmetric first peak reaching its maximum $0.39 \pm 0.02$
cycles after the radio peak plus a second peak at$0.94 \pm 0.03$. The gamma-ray
spectral energy distribution of pulsed flux is well described by a power-law
(photon index $\alpha=1.87\pm0.09$) with a remarkable cutoff at below 100 MeV,
representing the softest spectrum observed among gamma-ray pulsars so far. The
unusual soft break in the spectrum of PSR B1509-58 has been interpreted in the
framework of polar cap models as a signature of the exotic photon splitting
process in the strong magnetic field of this pulsar. In the case of an
outer-gap scenario, or the two pole caustic model, better constraints on the
geometry of the emission would be needed from the radio band in order to
establish whether the conditions required by the models to reproduce AGILE
light curves and spectra match the polarization measurements.
View original:
http://arxiv.org/abs/1110.6929
No comments:
Post a Comment