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Constraints On the Emission Geometries and Spin Evolution Of Gamma-Ray Millisecond PulsarsMillisecond 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 amaximum 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 based 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.

Document ID
20140017715
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
doi:10.1088/0067-0049/213/1/6
Authors
Johnson, T. J. (National Academy of Sciences - National Research Council Washington, DC, United States)
Venter, C. (North-West Univ. Potchefstroom, South Africa)
Harding, A. K. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Guillemot, L. (Centre National de la Recherche Scientifique Annecy-le-Vieux, France)
Smith, D. A. (Observatoire de Paris France)
Kramer, M. (Bordeaux 1 Univ. Gradignan, France)
Celik, O. (Maryland Univ. Baltimore, MD, United States)
den Hartog, P. R. (Stanford Univ. Stanford, CA, United States)
Ferrara, E. C. (Maryland Univ. Greenbelt, MD, United States)
Hou, X. (Bordeaux 1 Univ. Gradignan, France)
Lande, J. (Twitter, Inc. Headquaters San Francisco, CA, United States)
Ray, P. S. (Naval Research Lab. Washington, DC, United States)
Date Acquired
December 23, 2014
Publication Date
June 18, 2014
Publication Information
Publication: The Astrophysical Journal Supplement Series
Publisher: The American Astronomical Society
Volume: 213
Issue: 1
Subject Category
Astrophysics
Report/Patent Number
GSFC-E-DAA-TN17872
Funding Number(s)
CONTRACT_GRANT: NSF-AST-1100968
CONTRACT_GRANT: NNG06EO90A
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
pulsars: general
acceleration of particles
gamma rays: stars

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