Gamma-ray emission in dissipative pulsar magnetospheres: from theory to Fermi observations

Journal Article · Wed Oct 01 04:00:00 EDT 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/793/2/97· OSTI ID:22370574

Kalapotharakos, Constantinos ^[1]; Harding, Alice K.; Kazanas, Demosthenes ^[2]

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1. University of Maryland, College Park (UMDCP/CRESST), College Park, MD 20742 (United States)
2. Astrophysics Science Division, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

We compute the patterns of γ-ray emission due to curvature radiation in dissipative pulsar magnetospheres. Our ultimate goal is to construct macrophysical models that are able to reproduce the observed γ-ray light curve phenomenology recently published in the Second Fermi Pulsar Catalog. We apply specific forms of Ohm's law on the open field lines using a broad range for the macroscopic conductivity values that result in solutions ranging, from near-vacuum to near-force-free. Using these solutions, we generate model γ-ray light curves by calculating realistic trajectories and Lorentz factors of radiating particles under the influence of both the accelerating electric fields and curvature radiation reaction. We further constrain our models using the observed dependence of the phase lags between the radio and γ-ray emission on the γ-ray peak separation. We perform a statistical comparison of our model radio-lag versus peak-separation diagram and the one obtained for the Fermi standard pulsars. We find that for models of uniform conductivity over the entire open magnetic field line region, agreement with observations favors higher values of this parameter. We find, however, significant improvement in fitting the data with models that employ a hybrid form of conductivity, specifically, infinite conductivity interior to the light cylinder and high but finite conductivity on the outside. In these models the γ-ray emission is produced in regions near the equatorial current sheet but modulated by the local physical properties. These models have radio lags near the observed values and statistically best reproduce the observed light curve phenomenology. Additionally, they also produce GeV photon cut-off energies.

• OSTI ID: 22370574
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 793; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CATALOGS
COMPARATIVE EVALUATIONS
COMPUTERIZED SIMULATION
ELECTRIC FIELDS
EMISSION
GAMMA RADIATION
GEV RANGE
MAGNETIC FIELDS
NEUTRONS
PHOTONS
PULSARS
STARS
STELLAR MAGNETOSPHERES
TRAJECTORIES
VISIBLE RADIATION