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Journal Article

Discovery of Gamma-ray Pulsations from the Transitional Redback PSR J1227-4853


Pletsch,  H. J.
Pulsar Observation and Data Analysis, AEI-Hannover, MPI for Gravitational Physics, Max Planck Society;

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Johnson, T. J., Ray, P. S., Roy, J., Cheung, C. C., Harding, A. K., Pletsch, H. J., et al. (2015). Discovery of Gamma-ray Pulsations from the Transitional Redback PSR J1227-4853. The Astrophysical Journal, 806(1): 91. doi:10.1088/0004-637X/806/1/91.

Cite as: http://hdl.handle.net/11858/00-001M-0000-0028-1D9B-B
The 1.69 ms spin period of PSR J1227-4853 was recently discovered in radio observations of the low-mass X-ray binary XSS J12270-4859 following the announcement of a possible transition to a rotation-powered millisecond pulsar state, inferred from decreases in optical, X-ray, and gamma-ray flux from the source. We report the detection of significant (5$\sigma$) gamma-ray pulsations after the transition, at the known spin period, using ~1 year of data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The gamma-ray light curve of PSR J1227-4853 can be fit by one broad peak, which occurs at nearly the same phase as the main peak in the 1.4 GHz radio profile. The partial alignment of light-curve peaks in different wavebands suggests that at least some of the radio emission may originate at high altitude in the pulsar magnetosphere, in extended regions co-located with the gamma-ray emission site. We folded the LAT data at the orbital period, both pre- and post-transition, but find no evidence for significant modulation of the gamma-ray flux. Analysis of the gamma-ray flux over the mission suggests an approximate transition time of 2012 November 30. Continued study of the pulsed emission and monitoring of PSR J1227-4853, and other known redback systems, for subsequent flux changes will increase our knowledge of the pulsar emission mechanism and transitioning systems.