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GRB
GReat
Bu’s GRB
2004 / 112
Early Mission History
1960s, the Vela series
Burst And Transient Source Experiment
(on the CGRO, launched in 1991)
BeppoSAX (launched in 1996/4/30)–
provide a much more accurate location
HETE– failed in 1996
GRB910421
1967/7/2 the first observation
1973 publish
“Model burst”
Distance:
1)galactic disc
2)halo
3)cosmological
~102pc
~104pc
~Mpc
For now
1)isotropic distribution
2)redshift determination(~30 now)
3)Angular distrubution
 strong suggest a cosmological origion!!
Z-known GRBs
So….
Huge energy Eiso~1051-54 erg
Rapid temporal variability on time scales
of ms  compact object
However, due to γ+γ e+ + eoptical depth should be >> 1,
non-thermal spectrum optical thin
Compactness problem
The “fire ball”
Large concentration of electromagnetic
radiation in small region of space with
small fraction of baryons
Sudden release of high intensity gammarays produces e+e- pairs which create an
opaque photon-lepton “fireball”
The solution??
The relativistic motion ( with Γ≧100 ) of the
emitting region
GRB are produced when an UR energy flow is
converted to radiation in an optically thin
region
aberration of light :
cos  '  
cos  
1  v cos  '
beaming effect :
for   1,
1
 ~

GRB all star
GRB970228 Afterglow, x-ray ,optical counterpart,
XT RT (a breakthrough)
GRB970508 Redshift ,absorption lines (FeII MgII),
radio counterpart
GRB971214 Host galaxy
GRB980425 SN association(SN1998bw) (z=0.0085,
the “closet”)
GRB990123 most energetic ( Eiso~3 X 1054erg )
optical counterpart (by ROTSE)
GRB030325 polarzation
GRB030329 SN association(SN2003dh)
m1 1  m2 2  (m1  m2 
m
E
)
C2
Adopt from SCIENCE@NASA
Summary of observation
Observation (I) --GRB
Eiso
Burst rate
in 1991-2000 (CGRO operation period)
1/day (~1/106-7yr/galaxy)
Duration
T90:5%~95% in the 50-300keV
Observation (II) --GRB
Spectrum
Non-thermal
No clear observational evidence for the
existence of spectral lines
Observation (III) -afterglow
Lightcurves Well fitted by power-laws
~5 GRB has line features in the early Xray afterglow
Some of them “Break” (low energy
poewer index ~2)
Offset from the center of the hot galaxy
Host galaxy (025~Z~4.5): are typically
low mass, faint galaxies (R~25) with
active star formation region
several re-brightenings, varying power law indices
Observation (IV) -afterglow
GRB/SN connection
red excess ,”SN bump”:
GRB980326, GRB011121
GRB980425 / SN1998bw : within the
error box
GRB030329 / SN2003dh: very similar
spectrum with that in SN1998bw case
“super” Type Ic
Types of SNe
according to the spectrum
with H = SN II
without H = SN I
with Si = SN Ia
without Si but with He = SN Ib
without Si and without He = SN Ic
The energy source for SN Ia is nuclear;
for the others is gravitational
The lack of a measured redsift
SNIc
Best fit : Z~0.95
Spectral evolution
Observation (V) -afterglow
Polarization
MNRAS 309,L7 1999
Consider a magnetic field
completely
tangled in the plane of the shock
front, but with a high degree of
coherence in the orthogonal
direction
Γ 1 light aberration vanishes,
The observe magnetic field is
Completed tangled and
Polarization disappears
Γ ~ 1/(θc+ θ0)
Γ <1/(θc- θ0) see only part of
the circle centred on θ0
Γ >>1, no polarization
Two maxima in the polarization light curve, the first for
The horizontial component and the second for the vertical one!!
GRB030325
Oh , Theory
Model forest
SGRs as a hint ??
Relativistic dust crash energetically into the
solar wind
Comets falling onto NSs
Precessing jets from pulsars
Canonballs from supernovae
Jet-disk in a binary system
Magnetar bubble collapse
NS collapse to a strange star
Collapse to a BH caused by accretion
Supermassive BH formation
Evaporating BHs
The “fireball” again
GRBs occur through the
dissipation of the kinetic energy of
a relativistic expanding fire ball
γ-ray emission mechanisms
The shape of things
Time variability (~milliesecond)
R~ CΓ∆T  compact object
Duration 10-2s ~ 103s
Energy Eiso~1051-54 (for z-known GRBs)
Beaming
Rates , R~1/106-7yr/galaxy
if beamed….. E jet ~ Eiso 2
2
j
 j : half - opening angle
 j 2
4
R'  R 
,   2   sin  d d

0 0
The internal-external model
Time-varying outflow makes different Γ(>100) shells
When a faster shell catch up with a slower one:
Kinetic energy
 internal energy (internal shock )
 radiation (accelerated electrons interact
with the ambient magnetic field )
internal shock  GRB
external forward shock  afterglow
The “inner engine”
Binary NS merge
WD-NS , NS-BH merge
failed supernova (Collapsar)
Collapsar – a BH is born
1993, by Woosley et al.
“Failed supernova”
Iron core collapse BH
MHD jet
ApJ 524:262 1999
Adopted from GSFC, NASA
The jet is erupting through the surface of the star.
Blue represents regions of low mass concentration,
red and yellow are denser .
Note the blue and red striations behind the head of the jet.
These are bounded by internal shocks.
Make story complete —
asymmetric supernova
2000, by wheeler et al.
The generation of jets
Make story more complete —
Wolf-Reyet star
Wolf-Rayet stars are hot (25-50,000+ degrees
K), massive stars (20+ solar mass) with a
high rate of mass loss. Strong, broad
emission lines (with equivalent widths up to
1000Å!) arise from the winds of material
being blown off the stars.
Wolf-Rayets stars are divided into 3 classes
based on their spectra,
WN stars (nitrogen dominant, some carbon),
WC stars (carbon dominant, no nitrogen),
WO stars with C/O < 1.
The whole story….
To make a collapsar need three essential
components:
1)Wolf-Rayet star
2)A rotating stellar core
3)A core collapse that failed to
produce a successful supernova
Summary
Conclusion
Multi-origion
MHD
Gravitational wave
Polarization
TeV photon observation
GRB 970828 no OT, “dark burst”
 be obscured by dust in their host galaxy
 associated with massive sar formation??
The unified model??
astro-ph/0410728
Reference and Special Thanks
Many of content are adopted from
“Jochen Greiner Homepage”
( http://www.mpe.mpg.de/~jcg/ )
Romanian Report in Phisics, Vol.56
No.2 P204, 2004 Valeriu Tudose et al.
ASTRONOMY, October 2004
Others….