Astrophysical Journal 620,2 (2005) 905-914;
Multiwavelength observations of the black hole X-ray binary XTE J1118+480 have offered abundant spectral and timing information about the source and have thus provided serious challenges to theoretical models. We propose a coupled accretion-jet model to interpret the observations. We model the accretion flow as an outer standard thin accretion disk truncated at a transition radius by an inner hot accretion flow. The accretion flow accounts for the observed UV and X-ray emission, but it substantially underpredicts the radio and infrared fluxes, even after we allow for nonthermal electrons in the hot flow. We attribute the latter components to a jet. We model the jet emission by means of the internal shock scenario, which is widely employed for gamma-ray bursts. In our accretion-jet model of XTE J1118+480, the jet dominates the radio and infrared emission, the thin disk dominates the UV emission, and the hot flow produces most of the X-ray emission. The optical emission has contributions from all three components: jet, thin disk, and hot flow. The model qualitatively accounts for timing features, such as the intriguing positive and negative time lags between the optical and X-ray emission and the wavelength-dependent variability amplitude.
accretion, accretion disks;; black hole physics;; ism : jets and outflows;; stars : individual (xte j1118+480);; x-rays : stars;; advection-dominated accretion;; radio/x-ray correlation;; sagittarius a-asterisk;; broad-band spectrum;; x-ray;; optical variability;; multiwavelength observations;; candidate xte-j1118+480;; relativistic jets;; burst afterglows
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