Transcript LOCALIZATION AND OBSERVATIONS OF GRB010921 BY THE …

CEA
Explosões Cósmicas
(Bursts) de Raios Gama
Novidades 2004/2005
Nova Física
no Espaço 2005
João Braga – INPE
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eventos recentes e implicações
para os modelos de GRBs
SWIFT e perspectivas
09/10/2000
17/10/2002
20/11/2004
Recent GRBs
burst
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satélite
031203
Integral
040511
HETE-2
040701X
HETE-2
040924
HETE-2
041006
HETE-2
041219
Integral/Swift
041223
Swift
SGR
1806-20
Geotail, Mars
Odyssey, RHESSI,
Wind, Swift
050124
AG
X
AG
óptico
AG
rádio
z
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0.105
X(?)
Associated to
SN 2003lw
Bright long GRB
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X
Obs.
0.215
XRF
(very soft GRB)
X
0.859
First AG seen for a
short (soft) burst
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0.716
Bump similar to
SN1998bw
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Swift
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050126
Swift
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050215B
Swift
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X
(VLA)
Long (9 min) and
bright burst
First bona-fide
Swift burst
Giant flare from
SGR 1806-20
(short burst)
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GRB 031203
Discovered by Integral (T ~ 30s) on Dec. 3, 2003
Optical and NIR (~9hs after) show faint AG
superimposed to host galaxy at z=0.1055
Rebrightening detected in all bands
peaking at 18 rest-frame days,
resembling light curve of SN 1998bw
Spectra taken close to maximum show extremely
broad features as in SN 1998bw  SN 2004lw
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Strong support to GRB/energetic Ic SN (“hypernova”)
association (after GRB 030329/SN 2003dh)
Reminder:
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GRB 030329
(Discovered by HETE-2, Vanderspek et al. 2003)
• GRB030329 is among the brightest 1% of bursts ever seen
• typical long burst (~25s), fluence of 1.6 x 10-4 erg cm-2
E,iso ≈ 1.3 x 1052 erg
• optical AG had magnitude ~12 after 1.5 h (more than 3 mag brighter
than GRB 990123 and GRB 021004)
• optical AG observed by an unprecedented number of telescopes (65)
• GRB030329 was the nearest “cosmological” GRB, at z = 0.17
(obtained 16h after the burst by the VLT and 8h later by Keck)
• ~ 10 days after the GRB, the spectral signature of an energetic
Type Ic supernova emerged (SN 2003dh).
z = 0.1675  probability of detecting a GRB this close by is ~1/3000
=> unlikely that HETE-2 or Swift will see another such event
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Optical light curve
of SN 2003dh
Spectrum of SN 2003dh
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Stanek et al. (2003)
Spectrum of SN 2003lw
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Malesani et al.
(2004)
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Type Ic SNe
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SN2003lw
absence of broad H lines  Type I
weak or absent Si II 6150  not Ia or Ib
unusually broad features and blended lines
remarkably similar to SN1998bw
very large expansion velocities – similar to SN1998bw
(~ 23000 km/s @ 10 days)
SN2003lw is yet another case of a hypernova,
albeit much less energetic than SN2003dh
GRB 031203 may be a cosmic analogue of GRB 980425:
sub-energetic GRBs with faint afterglows
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In 29 GRB/XRF with measured redshifts
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Evidence for SN
connection for GRBs
18 have light curve bumps  photometric evidence for SNe
4 cases have spectroscopic evidence for a SN
SNR W49B: GRB in the Milky Way @ 12 kpc? (Chandra)
Barrel-shaped nebula with bright IR rings and a bar of intense
X-ray emission
 X-rays flare out at hot caps surrounded by IR emission
 Jets produced in the SN collided with a cloud of gas and dust ?
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GRB 041006
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Discovered by HETE-2
Position available 42 s after
the burst
Light curve and spectrum
very similar to GRB 030329,
but 20 times fainter
OT absorption lines: z=0.716
Jet break tb at 0.14 days
(earliest known)
Deep optical photometry over
65 days shows bump well
fitted by SN1998bw corrected
light curve  another
hypernova (Stanek et al. 2004)
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GRB 041006
SN 1998bw light curve corrected for z=0.716
reminder
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Soft Gamma Ray Repeaters
SGR
Burst of March 5th, 1979 (SGR 0526-66)
 SNR N49 in LMC (~10,000 ys)
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SOFT GAMMA RAY REPEATERS
bursts repeat in random timescales (normally
hundreds of times) (4, maybe 5 objects known)
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soft spectra (E  100 keV)
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short duration (~100 ms)
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Galactic “distribution”, associated with SNRs
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possibly associated with magnetars and AXPs
Soft Gamma Ray Repeaters
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SGR
reminder
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GRB duration distribution
reminder
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Progenitors
Short GRBs - Possibilities:
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associated with mergers of compact objects
SGRs in external galaxies
phase transition to strange stars
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Giant flare from
SGR 1806-20
SGRs are thought to be magnetars: neutron stars with observable
emissions (up to 100 keV) powered by magnetic dissipation
Giant flare from SGR 1806-20 detected on December 27, 2004
6
 380s long, ~10 brighter than typical GRBs (emission followed
by hard X-ray tail modulated by the period of the neutron star – 7.56s)
energy greatly exceeds previous events
 initial (200 ms) spike has blackbody spectrum, characteristic of
relativistic pair/photon outflow
 observed light curve is well explained by emission from relativistic
expanding fireballs, like GRBs (Yamazaki et al., astro-ph 0502320)
 rapidly fading after 600 ms  emission from relativistic jet
 extreme energy suggests catastrophic instability involving global
crust failure and magnetic reconnection, perhaps with significant
large-scale untwisting of the magnetosphere (new physics !!)
 from a great distance this event would appear to be a
short-hard GRB ! (Hurley et al. 2005, subm. Nature)
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Giant flare from
SGR 1806-20
Terasawa et al. 2005
(Nature, subm.)
Yamazaki et al. 2005
(Nature, subm.)
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GRB models
Observations favor the collapsar
model
collapsar: high mass WR star, high
rotation, make black hole
 1% of supernovae are collapsars
 Maybe 1 GRB/galaxy/10.000 years
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The fireball model
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The fireball model
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Complex light curves are due to internal shocks
caused by velocity variations – blobs with different s
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Turbulent magnetic fields build up behind the shocks
 synchrotron power-law radiation spectrum
 Compton scattering to GeV range
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Jetted fireball: fireball can be significantly collimated
if progenitor is a massive star with rapid rotation
 escape route along the rotation axis
 jet formation
 alleviate energy requirements
 higher burst rates
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GRBs as a probe for
cosmology
Earliest massive stars form at z ≈ 20
GRBs may mark the moment of “first light”
(end of the “dark ages”, from z=1100)
 indeed, some calculations (Lamb & Reichart 2000)
suggest that 10-40% of GRBs may lie at z > 5
GRBs have -ray luminosities 10 billion times greater than
the associated SNe and host galaxies
 GRBs are easily detectable out to z ≈ 20
HETE-2 has shown that Liso and Eiso are correlated with z
 GRBS evolve with redshift: bursts at z=5 are ~1000
times more luminous than at z=0 !
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GRBs as a probe for
cosmology
Strong correlation found:
2/3
obs
Epeak  Epeak (1+z)  E 
(Guirlanda, Ghisellini & Lazzati 2004)
Epeak is the peak of the  F spectrum
E is the collimation-corrected GRB energy: E = (1 – cos j ) E,iso
Underlying physical reason is not known, but the radiation process
(and photon energy) should be related to the energy content
The correlation makes GRBs important cosmological tools,
because they probe redshifts not accessible by Ia SNe
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Rapid slewing satellite
for transient astronomy
Launched on Nov. 20, 2004
(2-year mission)
Detailed X-ray, UV/optical AG
observations from 1 min to days after the burst
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Instruments:
1. 15-150 keV burst detector (BAT)
with 1-4 arcmin position; triggers
autonomous spacecraft slews
2. narrow-field X-ray telescope (XRT),
spectroscopy from 0.2 to 10 keV with
5 arcsec positions
3. narrow-field UV/optical telescope,
170-600 nm, 0.3 arcsec positions,
optical finding-charts
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Redshift determination for most bursts
1 mCrab hard X-ray survey
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What to expect in
the coming years
 Early afterglows will be carefully studied  the missing link
between the prompt emission and the afterglow will be identified;
 The jet configuration will be identified  universal structured jet
model could be validated by future data;
 With accumulation of a large sample of spectral information and
redshifts for GRB/XRF with Swift, we will know a lot more about
the site(s) and mechanism(s) for the prompt emission;
 Detection of GRB afterglows with z > 6 may provide a unique way
to probe the primordial star formation, massive IMF, early IGM,
and chemical enrichment at the end of the cosmic reionization era.
(Djorgovski et al. 2003);
 With Swift, we should get ~120 GRBs to produce Hubble diagrams
free of all effects of dust extinction and out to redshifts impossible
to reach by any other method (Schaefer 2003).
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Open questions
 What is the exact nature of the central engine?
 Why does it work so intermittently, ejecting blobs
with large contrast in their bulk Lorentz factors?
 What is the radiation mechanism of the prompt
emission?
 What is the jet angle? If between 2o and 20o, the
energy can vary by ~500 (~1050 – 1052 erg)
 What is the efficiency of converting bulk motion
into radiation?
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“For theorists who may wish to enter this broad
and growing field, I should point out that there
are a considerable number of combinations,
for example, comets of antimatter falling onto
white holes, not yet claimed.”
M. Ruderman