Testing the blast wave model with Swift GRBs
Peter A. CurranMullard Space Science Laboratory, UCL
withRLC Starling, AJ van der Horst,
A Kamble, RAMJ Wijers, M de Pasquale & M Page
pre-Swift versus Swift GRBs
pre-Swift versus Swift GRBs
pre-Swift (GRB 990510)
(Kuulkers et al. 2000)
X-ray
Optical
pre-Swift (GRB 990510) Swift era (GRB
070107)
(Evans et al. 2007)
(Kuulkers et al. 2000)
X-ray
Optical
X-ray only
pre-Swift versus Swift GRBs
pre-Swift (GRB 990510) Swift era (GRB
070107)
(Evans et al. 2007)
(Kuulkers et al. 2000)
X-ray
Optical
pre-Swift versus Swift GRBs
Does pre-Swift theory work?
X-ray only
The blast wave model
(CXC/M. Weiss)
The blast wave model
(CXC/M. Weiss)
k – circumburst density profile (ρ ~ r-k)
The blast wave model
(CXC/M. Weiss)
k – circumburst density profile (ρ ~ r-k)
q – continued energy injection
index (E ~ tq)
The blast wave model
(CXC/M. Weiss)
p – electron energy distribution (Fermi; dN/dE ~ E-
p)
k – circumburst density profile (ρ ~ r-k)
q – continued energy injection
index (E ~ tq)
Synchrotron spectra
(Sari et al. 1998)
Synchrotron spectra
Optical / X-ray
(Sari et al. 1998)
Derivation of p
α ➝ p(α,k,q) & accuracy of temporal fit⇒ multiple options
Derivation of p
α ➝ p(α,k,q) & accuracy of temporal fit⇒ multiple options
βopt ➝ p(βopt,EB-V) ⇒ multiple options
Derivation of p
α ➝ p(α,k,q) & accuracy of temporal fit⇒ multiple options
βopt ➝ p(βopt,EB-V) ⇒ multiple options
βX ➝ p(βX,NH) ⇒ multiple options
Derivation of p
α ➝ p(α,k,q) & accuracy of temporal fit⇒ multiple options
βopt ➝ p(βopt,EB-V) ⇒ multiple options
βX ➝ p(βX,NH) ⇒ multiple options⇒ above/below synchrotron cooling
frequency
Derivation of p
Sample of 10 Swift GRB afterglows
Sample of 10 Swift GRB afterglows
(GRB 060729)
X-ray
Optical
Consistent with the
blast wave model?
(GRB 060729)
X-ray
Optical
Sample of 10 Swift GRB afterglows
Blast wave interpretations
Compare possible multi-wavelength interpretations with blast wave†...
(†Nousek et al. 2006; Starling et al. 2008)
Blast wave interpretations
Compare possible multi-wavelength interpretations with blast wave†...
8/10 consistent with blast wave
4/10 unambiguous jet breaks
6/10 calculated k
3/10 require q ; 3/10 don’t
6/10 unambiguous p 4 above cooling break 2 below cooling break
(†Nousek et al. 2006; Starling et al. 2008)
(Curran et al. 2009)
k
Circumburst density profile, k
(Curran et al. 2009)
(Curran et al. 2009)
Circumburst density profile, k
Wind
(Curran et al. 2009)
Wind
ISM
Circumburst density profile, k
(Curran et al. 2009)
Wind
ISM
Circumburst density profile, k
Not consistent with only one of ISM or
Wind
q
Energy injection index, q
(Curran et al. 2009)
E ~ tq
Energy injection index, q
(Curran et al. 2009)
E ~ tq
Energy injection index, q
(Curran et al. 2009)
E ~ tq
Energy injection index, q
(Curran et al. 2009)
E ~ tqRequired but inconclusive..
.so far
p
Distribution of p
(Curran et al. 2009)
(Curran et al. 2009)
Distribution of p
Not consistent with a single, universal
value
Distribution of p
βX
Distribution of p
Distribution of spectral index, β
below cooling break
above cooling break
Distribution of spectral index, β
(Curran et al. in prep; data from Evans et al. 2009)
Distribution of spectral index, β
(Curran et al. in prep; data from Evans et al. 2009)
Distribution of spectral index, β
(Curran et al. in prep; data from Evans et al. 2009)
Most X-rays above cooling break?
Conclusions
8 out of 10 GRBs favour the blast wave model*
(*or at least don't disfavour it)
k is not consistent with only one of ISM or Wind
q is required in some bursts, inconclusive so far
• p is not consistent with a single, universal value
Most X-rays above the cooling break?
