PROBING MILLISECOND PULSAR EMISSION GEOMETRY USING LIGHT CURVES FROM THE FERMI/LARGE AREA TELESCOPE

Journal Article · Thu Dec 10 00:00:00 EST 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/707/1/800· OSTI ID:21389303

Venter, C; Harding, A K ^[1]; Guillemot, L ^[2]

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1. Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
2. Universite de Bordeaux, Centre d'Etudes Nucleaires Bordeaux Gradignan, UMR 5797, Gradignan, 33175 (France)

An interesting new high-energy pulsar sub-population is emerging following early discoveries of gamma-ray millisecond pulsars (MSPs) by the Fermi Large Area Telescope (LAT). We present results from three-dimensional emission modeling, including the special relativistic effects of aberration and time-of-flight delays and also rotational sweepback of B-field lines, in the geometric context of polar cap (PC), outer gap (OG), and two-pole caustic (TPC) pulsar models. In contrast to the general belief that these very old, rapidly rotating neutron stars (NSs) should have largely pair-starved magnetospheres due to the absence of significant pair production, we find that most of the light curves are best fit by TPC and OG models, which indicates the presence of narrow accelerating gaps limited by robust pair production-even in these pulsars with very low spin-down luminosities. The gamma-ray pulse shapes and relative phase lags with respect to the radio pulses point to high-altitude emission being dominant for all geometries. We also find exclusive differentiation of the current gamma-ray MSP population into two MSP sub-classes: light curve shapes and lags across wavebands impose either pair-starved PC (PSPC) or TPC/OG-type geometries. In the first case, the radio pulse has a small lag with respect to the single gamma-ray pulse, while the (first) gamma-ray peak usually trails the radio by a large phase offset in the latter case. Finally, we find that the flux correction factor as a function of magnetic inclination and observer angles is typically of order unity for all models. Our calculation of light curves and flux correction factor for the case of MSPs is therefore complementary to the 'ATLAS paper' of Watters et al. for younger pulsars.

• OSTI ID: 21389303
• Journal Information: Astrophysical Journal, Vol. 707, Issue 1; Other Information: DOI: 10.1088/0004-637X/707/1/800; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ACCELERATION
EMISSION
GAMMA RADIATION
INCLINATION
LUMINOSITY
NEUTRON STARS
NEUTRONS
PAIR PRODUCTION
PULSARS
PULSE SHAPERS
PULSES
RELATIVISTIC RANGE
SIMULATION
SPIN
TELESCOPES
THREE-DIMENSIONAL CALCULATIONS
TIME-OF-FLIGHT METHOD
VISIBLE RADIATION
ANGULAR MOMENTUM
BARYONS
COSMIC RADIO SOURCES
ELECTROMAGNETIC RADIATION
ELECTRONIC CIRCUITS
ELEMENTARY PARTICLES
ENERGY RANGE
FERMIONS
HADRONS
INTERACTIONS
IONIZING RADIATIONS
NUCLEONS
OPTICAL PROPERTIES
PARTICLE PRODUCTION
PARTICLE PROPERTIES
PHYSICAL PROPERTIES
PULSE CIRCUITS
RADIATIONS
SIGNAL CONDITIONERS
STARS