Fermi Gamma-ray Space Telescope

Observations of Gamma-ray Spiders with the Fermi Large Area Telescope

T. J. Johnson
P. S. Ray, F. Camilo, M. S. E. Roberts, on behalf of the Fermi LAT Collaboration

Abstract:

Significant gamma-ray pulsations have been detected from at least 16 'black widow' and 4 'redback' millisecond pulsars (MSPs) using data from the Fermi Large Area Telescope (LAT). Gamma-ray flux changes have also been observed associated with transitions, in both directions, between rotation-powered pulsar and low-mass X-ray binary states of two redbacks. We present a summary of LAT observations of these 'gamma-ray spiders', including results on pulse profiles and spectral characteristics. Additionally, we describe searches for unpulsed gamma-ray emission from these MSPs, possibly arising from interactions between the wind of the pulsar and that of its companion, including tests of the LAT data for modulation at the orbital periods. For the latter study, we stress the importance of correcting for exposure variations across the orbital phase. Portions of this research performed at the US Naval Research Laboratory are sponsored by NASA DPR S-15633-Y and Fermi GO proposal 061103.