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Title: Discovery of gamma-ray pulsations from the transitional redback PSR J1227-4853

Here, 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 (5σ) gamma-ray pulsations after the transition, at the known spin period, using ~1 year of data from the Large Area Telescope (LAT) 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 PSRmore » J1227–4853, and other known redback systems, for subsequent flux changes will increase our knowledge of the pulsar emission mechanism and transitioning systems.« less
 [1] ; ORCiD logo [2] ;  [3] ;  [2] ;  [4] ; ORCiD logo [5] ;  [5] ; ORCiD logo [6] ;  [7] ;  [8] ;  [8] ;  [9]
  1. George Mason Univ., Fairfax, VA (United States); Naval Research Lab., Washington, D.C. (United States)
  2. Naval Research Lab., Washington, D.C. (United States)
  3. The Univ. of Manchester, Manchester (United Kingdom); Pune Univ. Campus, Pune (India)
  4. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
  5. Max-Planck-Institut fur Gravitationsphysik, Hannover (Germany); Leibniz Univ. Hannover, Hannover (Germany)
  6. Columbia Univ., New York, NY (United States)
  7. National Academy of Sciences, Washington, D.C. (United States); Naval Research Lab., Washington, D.C. (United States)
  8. The Univ. of Manchester, Manchester (United Kingdom)
  9. Australia Telescope National Facility, Epping, NSW (Australia)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 806; Journal Issue: 1; Journal ID: ISSN 1538-4357
Institute of Physics (IOP)
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
Country of Publication:
United States
79 ASTRONOMY AND ASTROPHYSICS; pulsars: individual (J1227–4853); binaries: eclipsing; gamma rays: stars
OSTI Identifier: