Transcript Observation
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
R' R
4
, 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….