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?