Numerical Modeling of the Radio Nebula from the 2004 December 27 Giant Flare of SGR 1806-20
The authors use the relativistic hydrodynamics code Cosmos++ to model the evolution of the radio nebula triggered by the Dec. 27, 2004 giant flare event of soft gamma repeater 1806-20. They primarily focus on the rebrightening and centroid motion occurring subsequent to day 20 following the flare event. They model this period as a mildly relativistic ({gamma} {approx} 1.07-1.67) jetted outflow expanding into the intergalactic medium (IGM). They demonstrate that a jet with total energy {approx} 10{sup 46} ergs confined to a half opening angle {approx} 20{sup o} fits the key observables of this event, e.g. the flux lightcurve, emission map centroid position, and aspect ratio. In particular, they find excellent agreement with observations if the rebrightening is due to the jet, moving at 0.5 c and inclined {approx} 0{sup o}-40{sup o} toward the observer, colliding with a density discontinuity in the IGM at a radius of several 10{sup 16} cm. They also find that a jet with a higher velocity, {approx}> 0.7c, and larger inclination, {approx}> 70{sup o}, moving into a uniform IGM can fit the observations in general, but tends to miss the details of rebrightening. The latter, uniform IGM model predicts an IGM density more than 100 times lower than that of the former model, and thus suggests an independent test which might discriminate between the two. One of the strongest constraints of both models is that the data seems to require a non-uniform jet in order to be well fit.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 900870
- Report Number(s):
- UCRL-JRNL-221643; TRN: US200711%%621
- Journal Information:
- The Astrophysical Journal, vol. 652, N/A, December 1, 2006, pp. 1508-1522, Vol. 652
- Country of Publication:
- United States
- Language:
- English
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