Subexponential decay in Fermi-LAT pulsar spectra: The case for tachyonic Cherenkov radiation
Department of Physics, Hiroshima University - 1-3-1 Kagami-yama, Higashi-Hiroshima 739-8526, Japan
Received: 3 February 2014
Accepted: 22 April 2014
Tachyonic Cherenkov fits are performed to the Fermi-LAT γ-ray spectra of the Vela pulsar, PSR J1709 − 4429 and Geminga. The high-energy spectral tails of these pulsars exhibit pronounced subexponential Weibull decay, which can be modeled in a permeable spacetime by a frequency-dependent tachyon mass. The scaling exponent of the tachyon mass defines the Weibull shape parameter of the energy flux, and it also determines whether the radiation is sub- or superluminal. The negative mass-square in the tachyonic Maxwell-Proca equations gives rise to a longitudinal flux component. The radiation is generated by an ultra-relativistic thermal electron plasma via the inertial Cherenkov effect. The transversal and longitudinal γ-ray emission from Geminga is slightly superluminal, whereas γ-rays from the Vela pulsar and PSR J1709 − 4429 are subluminal despite the negative tachyonic mass-square in the dispersion relations.
PACS: 95.30.Gv – Radiation mechanisms; polarization / 41.60.Bq – Cherenkov radiation / 97.60.Gb – Pulsars
© EPLA, 2014