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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 field. We modeled the radio profiles 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-fit parameters and confidence 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 fit roughly equal numbers of Class I and II, while Class III are exclusively fit with pair-starved polar cap models. Distinguishing between the model classes basedmore » on typical derived parameters is difficult. We explore the evolution of the magnetic inclination angle with period and spin-down power, finding possible correlations. While the presence of significant off-peak emission can often be used as a discriminator between outer gap and slot gap models, a hybrid model may be needed.« less
Authors:
 [1] ;  [2] ; ; ;  [3] ;  [4] ; ;  [5] ;  [6] ;  [7] ;  [8] ;  [9]
  1. National Research Council Research Associate, National Academy of Sciences, Washington, DC 20001 (United States)
  2. Centre for Space Research, North-West University, Potchefstroom Campus, Private Bag X6001, 2520 Potchefstroom (South Africa)
  3. NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
  4. Laboratoire de Physique et Chimie de l'Environnement, LPCE UMR 6115 CNRS, F-45071 Orléans Cedex 02 (France)
  5. Centre d'Études Nucléaires de Bordeaux Gradignan, IN2P3/CNRS, Université Bordeaux 1, BP120, F-33175 Gradignan Cedex (France)
  6. Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn (Germany)
  7. W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States)
  8. Twitter Inc., 1355 Market Street 900, San Francisco, CA 94103 (United States)
  9. Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States)
Publication Date:
OSTI Identifier:
22340205
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal, Supplement Series; Journal Volume: 213; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CONES; GALACTIC EVOLUTION; GAMMA RADIATION; GEOMETRY; INCLINATION; LIMITING VALUES; MAGNETIC FIELDS; MAXIMUM-LIKELIHOOD FIT; PHASE SPACE; POLARIMETRY; PULSARS; PULSES; SPIN; TELESCOPES; VISIBLE RADIATION