GRB3 - GRBs Observations vs. theory in the Swift era |
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Speaker |
Izzo, Luca |
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Co-autors |
Bernardini M.G., Bianco C.L., Caito L., Patricelli B., Ruffini R. |
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Talk Title |
GRB 090423 : a canonical GRB at redshift z = 8.1 |
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Abstract |
GRB090423 is the most distant GRB ever observed, with redshift z of about 8.1, a T90 duration is of 12 +- 1.2 s and an estimated Peak Energy of 40 +- 6 keV. We analyze Swift-BAT data in the band 15-150 keV and XRT data in the band 0.2-10 keV within the "fireshell" model. We can fit the source, for a total energy of the dyadosphere of 3.80 x 10^53 ergs, with a gravitational collapse to a ˜ 20 solar mass black hole. Possible solutions for such an e+e- black holes ranges from Mu = 1-50 solar masses for values of xi ranging from 0.15 to 0.88. Among these different Mu and xi we select one with Mu = 20 solar masses, and the corresponding xi = 0.233. We obtain an initial Lorentz gamma factor of 960 and a CBM average density in the range n = 10^-1 particles/cm^3 up to size of 10^18 cm, that corresponds to 1 light year. The conclusions are that this collapse occurred from a star by an almost complete gravitational collapse without any remnant up to a size of 1 light year. This is very different from all the other GRBs observed at smaller z factor, where an agreement with binary neutron stars or neutron stars / white dwarfs is possible. |
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