Shedding light on the prompt high efficiency paradox - self consistent modeling of GRB afterglows
Journal
Date Issued
2015
Author(s)
Abstract
We examine GRBs with both Fermi-LAT and X-ray afterglow data. Assuming that the 100MeV (LAT) emission is radiation from cooled electrons accelerated by external shocks, we show that the kinetic energy of the blast wave estimated from the 100MeV flux is 50 times larger than the one estimated from the X-ray flux. This can be explained if either: i) electrons radiating at X-rays are significantly cooled by SSC (suppressing the synchrotron flux above the cooling frequency) or ii) if the X-ray emitting electrons, unlike those emitting at 100MeV energies, are in the slow cooling regime. In both cases the X-ray flux is no longer an immediate proxy of the blast wave kinetic energy. We model the LAT, X-ray and optical data and show that in general these possibilities are consistent with the data, and explain the apparent disagreement between X-ray and LAT observations. All possible solutions require weak magnetic fields: $10^{-6}< \epsilon_B < 10^{-3}$ (where $\epsilon_B$ is the fraction of shocked plasma energy in magnetic fields). Using the LAT emission as a proxy for the blast wave kinetic energy we find that the derived prompt efficiencies are of order 15%. This is considerably lower compared with previous estimates (87% and higher for the same bursts). This provides at least a partial solution to the "prompt high efficiency paradox"
Coverage
Swift: 10 Years of Discovery (SWIFT 10)
All editors
Caraveo, Patrizia; D’Avanzo, Paolo; Gehrels, Neil; Tagliaferri, Gianpiero
Volume
233
Conferenece
Swift: 10 Years of Discovery
Conferenece place
La Sapienza University, Rome, Italy
Conferenece date
2-5 December 2014
Issn Identifier
1824-8039
Ads BibCode
2015arXiv150303368B
Rights
open.access
File(s)![Thumbnail Image]()
Loading...
Name
SWIFT 10_064.pdf
Size
230.29 KB
Format
Adobe PDF
Checksum (MD5)
f09c99e60587b5fd9152b8983e0c9630