Orbital Modulation of Gamma Rays from PSR~J2339$-$0533

Abstract

We report on orbital modulation of the 100-600 MeV gamma-ray emission of the $P_{\mathrm{B}}=4.6$ hr millisecond pulsar binary PSR J2339$-$0533 using 11 yr of Fermi Large Area Telescope data. The modulation has high significance (chance probability $p\approx 10^{-7}$), is approximately sinusoidal, peaks near pulsar superior conjunction, and is detected only in the low-energy 100-600 MeV band. The modulation is confined to the on-pulse interval, suggesting that the variation is in the 2.9-ms pulsed signal itself. This contrasts with the few other known systems exhibiting GeV orbital modulations, as these are unpulsed and generally associated with beamed emission from an intrabinary shock. The origin of the modulated pulsed signal is not yet clear, although we describe several scenarios, including Compton upscattering of photons from the heated companion. This would require high coherence in the striped pulsar wind.

11 pages, 7 figures. Accepted for publication in ApJ

References in corpus (5)

• Tempo2, a new pulsar timing package. II: The timing model and precision estimates
• Gamma-ray Timing of Redback PSR J2339-0533: Hints for Gravitational Quadrupole Moment Changes
• The Synchrotron Emission Pattern of IntraBinary Shocks
• High-Energy Variability of PSR J1311-3430
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• Investigation of the broadband emission of the gamma-ray binary HESS J0632+057 using an intrabinary shock model
• Single Pulse Variability in Gamma-ray Pulsars
• Millisecond pulsars phenomenology under the light of graph theory
• Very high-energy gamma-ray and neutrino emission from hadronic interaction in compact binary millisecond pulsars
• Evidence for optical pulsations from a redback millisecond pulsar