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Title: Constraints On The Emission Geometries And Spin Evolution Of Gamma-Ray Millisecond Pulsars

Millisecond pulsars (MSPs) are a growing class of gamma-ray emitters. Pulsed gamma-ray signals have been detected from more than 40 MSPs with the Fermi Large Area Telescope (LAT). The wider radio beams and more compact magnetospheres of MSPs enable studies of emission geometries over a broader range of phase space than non-recycled radio-loud gamma-ray pulsars. We have modeled the gamma-ray light curves of 40 LAT-detected MSPs using geometric emission models assuming a vacuum retarded-dipole magnetic eld. We modeled the radio pro les using a single-altitude hollow-cone beam, with a core component when indicated by polarimetry; however, for MSPs with gamma-ray and radio light curve peaks occurring at nearly the same rotational phase we assume that the radio emission is co-located with the gamma rays and caustic in nature. The best- t parameters and con dence intervals are determined using a maximum likelihood technique. We divide the light curves into three model classes, with gamma-ray peaks trailing (Class I), aligned (Class II) or leading (Class III) the radio peaks. Outer gap and slot gap (two-pole caustic) models best t roughly equal numbers of Class I and II, while Class III are exclusively t with pair-starved polar cap models. Distinguishing between themore » model classes based on typical derived parameters is diffcult. We explore the evolution of magnetic inclination angle with period and spin-down power, nding possible correlations. While the presence of signi cant off- peak emission can often be used as a discriminator between outer gap and slot gap models, a hybrid model may be needed.« less
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [3] ;  [5] ;  [9] ;  [10]
  1. National Academy of Sciences, Washington, DC (United States); Naval Research Lab. (NRL), Washington, DC (United States)
  2. North-West Univ., Potchefstroom (South Africa)
  3. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
  4. Laboratoire de Physique et Chimie de l'Environnement; Orleans (France); CNRS/IN2P3. Univ. Paris (France). Observatoire de Paris
  5. Univ. Bordeaux (France)
  6. Max-Planck-Institut für Radioastronomie, Bonn (Germany); Univ. of Manchester (United Kingdom)
  7. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States); Univ. of Maryland Baltimore County (UMBC), Baltimore, MD (United States)
  8. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  9. Twitter Inc., San Francisco, CA (United States)
  10. Naval Research Lab. (NRL), Washington, DC (United States)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Astrophysical Journal, Supplement Series
Additional Journal Information:
Journal Volume: 213; Journal Issue: 1; Journal ID: ISSN 0067-0049
American Astronomical Society
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
Country of Publication:
United States
OSTI Identifier: