Panaitescu 2007 晚期喷流的散射解释X射线耀发、慢下降和拐折

主要内容:
用晚期的喷流逆康普顿散射正向激波的光子来同时解释这三样东西。chromatic breaks好像是指不同颜色并不同时拐折。

精彩摘抄:


文章信息:

arXiv:0708.1509 [ps, pdf, other]

Title: X-ray flares, plateaus, and chromatic breaks of GRB afterglows from up-scattered forward-shock emission

Authors: A. Panaitescu

Comments: 11 pages, 7 figures, 59 easy equations. Submitted to MNRAS

Subjects: Astrophysics (astro-ph)

Scattering of the forward-shock synchrotron emission by a relativistic outflow ejected up to 10 ks after the leading blast-wave, may produce a brighter emission than that coming directly from the forward-shock and may explain three novel features discovered by Swift in the X-ray emission of GRB afterglows: flares, plateaus (slow decays), and chromatic light-curve breaks. For a cold scattering outflow, the reflected flux overshines the primary one if the scattering outflow is nearly baryon-free and highly relativistic. These two requirements can be relaxed if the scattering outflow is energized by weak internal shocks, so that the incident forward-shock photons are also inverse-Compton scattered. This sweeping-up of the photons left behind by the forward shock naturally yields X-ray flares that are (much) shorter than the time when they occur. Because of the boost in photon energy produced by bulk-scattering (and inverse-Compton, if present), the reflected emission is more likely to overshine the forward shock's at higher photon energies, yielding light-curve plateaus and breaks that appear only in the X-ray (energy injection in the forward-shock can hardly account for the latter feature). The brightness, shape, and decay of the X-ray light-curve plateau depend on the spectrum of the primary emission, as well as on the radial distribution of the scatterer's Lorentz factor and mass-flux. Thus, the various durations and decay rates displayed by X-ray afterglow plateaus reflect the diversity in the radial structure of the late outflows produced by long-lived GRB engines.