Light curve and SED modeling of the gamma-ray binary 1FGL J1018.6$-$5856: constraints on the orbital geometry and relativistic flow

Abstract

We present broadband spectral energy distributions (SEDs) and light curves of the gamma-ray binary 1FGL J1018.6$-$5856 measured in the X-ray and the gamma-ray bands. We find that the orbital modulation in the low-energy gamma-ray band is similar to that in the X-ray band, suggesting a common spectral component. However, above a GeV the orbital light curve changes significantly. We suggest that the GeV band contains significant flux from a pulsar magnetosphere, while the X-ray to TeV light curves are dominated by synchrotron and Compton emission from an intrabinary shock (IBS). We find that a simple one-zone model is inadequate to explain the IBS emission, but that beamed Synchrotron-self Compton radiation from adiabatically accelerated plasma in the shocked pulsar wind can reproduce the complex multiband light curves, including the variable X-ray spike coincident with the gamma-ray maximum. The model requires inclination $\sim$50${}^{\circ }$ and orbital eccentricity $\sim$0.35, consistent with the limited constraints from existing optical observations. This picture motivates searches for pulsations from the energetic young pulsar powering the wind shock.

10 pages, 5 figures, accepted for publication in ApJ

References in corpus (7)

• Development of the Model of Galactic Interstellar Emission for Standard Point-Source Analysis of Fermi Large Area Telescope Data
• Synchrotron Self-Compton Analysis of TeV X-ray Selected BL Lacertae Objects
• Gamma-ray binaries: pulsars in disguise ?
• Modeling interaction of relativistic and nonrelativistic winds in binary system PSR 1259-63/SS2883. I.Hydrodynamical limit
• Intra-Binary Shock Heating of Black Widow Companions
• Periodic Emission from the Gamma-ray Binary 1FGL J1018.6-5856
• Optical spectroscopy of the high-mass gamma-ray binary 1FGL J1018.6-5856: A probable neutron star primary

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