Transcript GRB 080319B: Naked-Eye Stellar Blast from the Distant Universe

Modeling GRB 080319B
Xuefeng Wu (X. F. Wu, 吴雪峰)
Penn State University
Purple Mountain Observatory
Collaborators: J. Racusin, D. Burrows, P. Meszaros (PSU)
B. Zhang (UNLV)
2008 Nanjing GRB Workshop, Nanjing, China, June 23-27
For more details about observations
J. Racusin’s talk (broad-band)
G. Beskin’s talk (TORTORA prompt optical)
V. D’Elia’s talk (spectroscopy)
Papers on this GRB on astro-ph:
J. Racusin et al., astro-ph/0805.1557,
J. Bloom et al., astro-ph/0803.3215,
S. Dado et al., astro-ph/0804.0621,
V. D’Elia et al., astro-ph/0804.2141
P. Kumar & A. Panaitescu, astro-ph/0805.0144,
Y. Yu et al., astro-ph/0806.2010
Outline
Interpreting the prompt emission;
Interpreting the very early afterglow;
Modeling the broad-band afterglow;
Prompt Emission
Konus-Wind
T0+11.4s – T0+21.3s
•
•
•
•
•
T90 ~ 57 s
Epeak = 651 ± 15 keV
Peak flux: 2.3 x 10-4 erg/cm2/s
Fluence: ~6x10-3 erg/cm2
Eγ,iso ~ 1.3 x 1054 ergs (DL=1.88 x 1028 cm)
Prompt Emission
See Guidorzi talk for details of correlation tests, and Beskin talk for TORTORA details
Prompt Emission
Prompt Emission
• Temporal coincidence and similar shape of
prompt optical and γ-rays light curves indicate
that they may originate from the same
physical region
• Optical flux ~4 orders of magnitude above
extrapolation of γ-rays requires that the
optical andγ-rays must come from different
emission components
Prompt Emission
Constraining the possible models:
the extremely bright prompt optical emission must
be emitted at a large radius (optical thin region,
~1016 cm), compared with typical internal shocks
radii (1013-14 cm)
For afterglow theory, cf. B. Zhang’s review talk
Prompt Emission
Models
• Synchrotron for optical and Syn. Self-Compton (SSC) for
MeV gamma-rays (Racusin et al. 2008; Kumar & Panaitescu
2008);
• Optical from the forward shock and MeV gamma-rays from
the reverse shock within the synchrotron internal shocks
model (Yu’s talk);
• Neutron-rich model (Fan, Wei, Zhang 2008)
• Residual internal shock model (Zhuo Li’s talk)
• External reverse shock propagating into a stratified-densityprofile GRB ejecta?
Prompt Emission
Constraining the prompt optical emission radius
Black body (Rayleigh-Jeans limit) assumption
specific intensity:
flux density:
: a constant ~1,
tobs ~ variability time tv (internal shocks model)
: (1010K – 1012K), comoving electron temperature
Prompt Emission
Constraining the prompt optical emission radius
tv~3 s (assuming), flux density ~ 25 Jansky
Г~103
R~ 1016 cm
a shorter variability time will result in larger Г and R
E2 N(E)
Prompt Emission
Syn.+ SSC Internal Shocks Model
Predictions
Optical depth due to IBL >1
for >30 GeV photons from z~1 GRB
Y ~ 10
Y ~ 10
Esyn~20 eV
Y2 ~100
ESSC1st ~650 keV
Klein-Nishina cut-off
ESSC2st
E
~25 GeV
obs., Y = ratio of E2N(E) between the Ist SSC and the syn. emission components.
theo., Y = (magnetic energy fraction / electron energy fraction)1/3 (Kobayashi et al. 2007)
E2 N(E)
Prompt Emission
Syn.+ SSC Internal Shocks Model
Predictions
Optical depth due to IBL >1
for >30 GeV photons from z~1 GRB
Y ~ 10
Y ~ 10
Esyn~20 eV
Y2 ~100
ESSC1st ~650 keV
Klein-Nishina cut-off
ESSC2st
E
~25 GeV
magnetic energy ~ 10-3 electron energy
GRB ejecta unmagnetized
E2 N(E)
Prompt Emission
Syn.+ SSC Internal Shocks Model
Predictions
Optical depth due to IBL >1
for >30 GeV photons from z~1 GRB
Y ~ 10
Y ~ 10
Y2 ~100
Klein-Nishina cut-off
2rd SSC photons ( ~ 20 GeV)
peak flux: 2.3x10-4 erg/cm2/s (1.5x10-1 MeV/cm2/s),
peak photon flux: ~10-5 photons/cm2/s,
total fluence of ~6x10-3 erg/cm2.
Esyn~20
eV
GLAST/LAT
sensitivities
@1st
20GeV
:
E
~650
keV
SSC
1.3x10-6 MeV/cm2/s,
3x10-10 photons/cm2/s,
2x10-5 erg/cm2.
Total energy released in
gamma-rays is
~ a few 1055 erg
(see also Kumar & Panaitescu08)
E
2st
ESSC ~25 GeV
This model could be easy
to be tested by GLAST
Afterglow
Optical light curve is normalized to UVOT v-band
X-ray and γ-ray arbitrarily scaled
Very Early Afterglow
high latitude emission
Very Early Afterglow
t2
t1

t0
R
t1
t2
schematic for high latitude emission
(cooling frequency < typical syn. frequency)
external reverse shock at the crossing time
Very Early Afterglow
t2
(Zou et al. 2005; Wu et al. 2003)
t1

t0
R
t1
t2
schematic for high latitude emission
(cooling frequency < typical syn. frequency)
external reverse shock at the crossing time
A relatively low Eiso (~1053 erg) and
a relatively large B (~0.1) are required
Afterglow
Evidence for a stellar wind environment: XRT LC
wind model:
Afterglow
Evidence for a stellar wind environment: UVOT LC
wind model:
Afterglow
X-ray Light Curve
Jet break without sideways expansion:
Afterglow Models
Two-Component Jet
Afterglow Models
Two-Component Jet
Afterglow Models
Two-Component Jet
Analytical Constrainments for Model Parameters
Narrow Jet:
Wide Jet:
Afterglow
Tail of
Prompt
Emission WJRS
NJFS
WJFS
WJFS
Afterglow Models
Numerical Calculation of the LC
Generic Hydrodynamic Model for Relativistic Shocks
(Huang, Dai, Gou, & Lu 2000)
Synchrotron Self-Absorption;
Synchrotron Self-Compton;
Adiabatic hydrodynamics (=0);
No sideways expansion (Cs=0);
Summary
• Prompt emission mechanisms are still in
debate, but will be solve in the GLAST era;
• Afterglow has been modeled well in the twocomponent jet model