A Magnetized Black Hole Model of LS I +61°303

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Abstract
A model of the nonthermal emission from the binary LS I +61°303 and the coincident hard γ-ray source 2EG J0241+6119 is presented that identifies the compact companion with a magnetized black hole. The model describes the γ-ray spectrum from 100 keV to 30 GeV in terms of inverse Compton scattering in a relativistic black hole jet. Accordingly, it predicts significant variability in the high-energy regime on timescales much shorter than the orbital period (as observed). The jet also powers quiescent X-ray (inverse Compton) and radio emission (synchrotron) consistent with observation. At periastron, significant accretion necessarily occurs from the primary Be star to the compact companion. This periodic accretion is associated with the power source for periodic radio and X-ray flares observed in LS I +61°303. The accretion flow is shocked at the black hole magnetospheric boundary producing hot plasma that synchrotron-cools in the strong magnetic field, creating X-rays (the X-ray flare). The hot gas also drives an episodic hydrodynamic wind that collides with the black hole-driven jet at distances greater than 1013 cm from the hole. The resulting wind-jet interaction creates synchrotron radio emission (the periodic radio flare). The model predicts that the peak of the X-ray flare precedes the peak of the radio flare by ≈ 9 days (consistent with observation). It also predicts a size of the high-state radio emission consistent with VLBI measurements as well as a smaller angular size for the high-state emitting region as compared to the region producing the quiescent radio emission. One final prediction of note is the lack of pulsations in both the radio and X-rays (as observed), which is a difficulty with identifying the compact object with a pulsar.

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