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Title: The braking index of a radio-quiet gamma-ray pulsar

Here, we report the discovery and timing measurements of PSR J1208-6238, a young and highly magnetized gamma-ray pulsar, with a spin period of 440 ms. The pulsar was discovered in gamma-ray photon data from the Fermi Large Area Telescope (LAT) during a blind-search survey of unidentified LAT sources, running on the distributed volunteer computing system Einstein@Home. No radio pulsations were detected in dedicated follow-up searches with the Parkes radio telescope, with a flux density upper limit at 1369 MHz of 30 μJy. Furthermore, by timing this pulsar's gamma-ray pulsations, we measure its braking index over five years of LAT observations to be n = 2.598 ± 0.001 ± 0.1, where the first uncertainty is statistical and the second estimates the bias due to timing noise. Assuming its braking index has been similar since birth, the pulsar has an estimated age of around 2700 years, making it the youngest pulsar to be found in a blind search of gamma-ray data and the youngest known radio-quiet gamma-ray pulsar. Despite its young age, the pulsar is not associated with any known supernova remnant or pulsar wind nebula. The pulsar's inferred dipolar surface magnetic field strength is 3.8 × 10 13 G, almost 90%more » of the quantum-critical level. Finally, we investigate some potential physical causes of the braking index deviating from the simple dipole model but find that LAT data covering a longer time interval will be necessary to distinguish between these.« less
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  1. Max Planck Inst. for Gravitational Physics and Leibniz Univ., Hannover (Germany). Albert-Einstein Inst.
  2. Max Planck Inst. for Radio Astronomy, Bonn (Germany)
  3. Max Planck Inst. for Radio Astronomy, Bonn (Germany); Univ. of Orleans (France). Lab. of Physics and Chemistry; National Inst. for Earth Sciences and Astronomy (CNRS/INSU), Nancay (France). station of Radio Astronomy
  4. Square Kilometer Array (SKA) South Africa, Pinelands (South Africa)
  5. George Mason Univ., Fairfax, VA (United States). College of Science
  6. Commonwealth Scientific and Industrial Research Organisation (CSIRO) Astronomy and Space Science, Epping (Australia)
  7. Max Planck Inst. for Gravitational Physics and Leibniz Univ., Hannover (Germany). Albert-Einstein Inst.; Univ. of Wisconsin, Milwaukee, WI (United States). Dept. of Physics
  8. Max Planck Inst. for Radio Astronomy, Bonn (Germany); Univ. of Manchester (United Kingdom). Jodrell Bank Centre for Astrophysics
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
The Astrophysical Journal. Letters
Additional Journal Information:
Journal Volume: 832; Journal Issue: 1; Journal ID: ISSN 2041-8213
Institute of Physics (IOP)
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
Contributing Orgs:
Fermi LAT Collaboration
Country of Publication:
United States
79 ASTRONOMY AND ASTROPHYSICS; gamma rays: stars; pulsars: individual (PSR J1208-6238)
OSTI Identifier: