GRB afterglows in the Non-relativistic phase Y. F. Huang Dept
Astronomy, Nanjing University Tan Lu Purple Mountain
Observatory
Slide 2
Outline 1.The importance of Non- relativistic phase 2.A generic
dynamical model 3.The deep Newtonian phase 4.Numerical results
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Energy of the shocked ISM: Adiabatic case: E ~ const and Highly
radiative case: Shock jump conditions The Physics of GRB
Afterglows
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Outline 1.The importance of Non- relativistic phase 2.A generic
dynamical model 3.The deep Newtonian phase 4.Numerical results
Slide 5
GRBs are impressive for their huge energies (Eiso ~ 10 52 ---
10 54 ergs) and ultra-relativistic motion ( ~ 100 --- 1000) Why the
non-relativistic phase is important?
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t -3/8 (200 --- 400) (E 52 /n 0 ) -1/8 t s -3/8 t = 1 day 2.8
--- 5.6 t = 10 day 1.2 --- 2.4 t = 30 day 0.8 --- 1.6 t = 0.5 year
0.4 --- 0.8 t = 1 year 0.3 --- 0.6 The deceleration of the shock
is:
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Huang et al., 1998, MNRAS Theoretical afterglow light curve
when E=1e52 erg, n=1cm -3
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Kann et al. arXiv:0804.1959 Observed afterglows
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Outline 1.The importance of Non- relativistic phase 2.A generic
dynamical model 3.The deep Newtonian phase 4.Numerical results
Slide 10
We need a generic dynamical equation, that is applicable in
both relativistic phase and non-relativistic phase. For adiabatic
blastwave For highly radiative blastwave The evolution of external
shocks Highly radiative and when t < n hours Adiabatic when t
> n hours, and maybe n days later For Newtonian blastwave (Sedov
solution)
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We need a generic dynamical equation, that is applicable in
both relativistic phase and non-relativistic phase. The evolution
of external shocks Highly radiative and when t < n hours
Adiabatic when t > n hours, and maybe n days later
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A generic dynamical equation Huang, Dai & Lu 1999, MNRAS,
309, 513
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The equation is consistent with Sedov solution
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Slide 15
Outline 1.The importance of Non- relativistic phase 2.A generic
dynamical model 3.The deep Newtonian phase 4.Numerical results
Slide 16
The deep Newtonian phase The generic dynamical equation can be
used to describe the overall evolution of GRB shocks. However, to
calculate the emission at very late stages, we meet another
problem. It is related to the distribution function of
shock-accelerated electrons.
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Distribution function of e - Problem: t > 1 --- 2 years,
< 1.5 (deep Newtonian phase)
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Our improvement lg ( e -1) lg N e Huang & Cheng
(2003,MNRAS) lg e lg N e 0 o e =5
Huang & Cheng, 2003,MNRAS Numerical results (2) conical jet
People usually use to derive the jet break time t j. However, in
our calculation, and gives a time of ~4000 s. But the break time is
~40000 s. So, we should be careful in estimating the beaming angle
from the observed jet break time. The light curve does not break at
!
Radio light curve of GRB 980703 Frail et al. 2003, ApJ, 590,
992 Application (1): GRB 980703
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GRB 980703 See Kongs poster and references therein
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Application (2): GRB 030329 Density jump 2-component jet Energy
injection Huang, Cheng & Gao, 2006 Obs. data taken from Lipkin
et al. 2004
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To produce a GRB successfully we need: A stringent requirement
! i.e., for Eiso ~ 10 52 erg we need Miso < 10 -5 Msun There may
be many fireballs with We call them Failed GRBs They may manifest
as X-ray flashes, orphan afterglows Newtonian phase will be
especially important in these cases. Huang, Dai, Lu, 2002, MNRAS,
332, 735 Failed GRBs and orphan afterglows Application (3): Failed
GRBs
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How to distinguish a failed-GRB orphan afterglow and a jetted
but off-axis GRB orphan? It is not an easy task. a failed-GRB
orphan Jetted GRB orphan
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Although GRB fireballs are ultra-relativistic initially, they
may become Newtonian in tens of days, and may enter the deep
Newtonian phase in 1 --- 3 years. Conclusion Thank you!
