Download Folie 1 - Pi of the Sky

Probing the high-redshift
Universe with Gamma-ray Bursts
Michael I. Andersen
Astrophysikalisches Institut Potsdam
Soltan Institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray bursts
M.I. Andersen
Outline of talk
A brief history of GRB’s.
 An emerging scenario, the progenitor.
 Tracking down star- and galaxy-formation.

Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
The Vela satellites
Launched by the US military to monitor
the test ban treaty.
 Pairwise in 110000km high orbit – 180deg
apart.
 Time delays up to 0.8sec for cosmic
events.

Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
The first GRB
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
The compactness problem
Cavallo & Rees (1978) and Schmidt
(1978) shows that self-absorption will be
severe, if distance is more than ~10 kPc.
This result was based on inferring the size
of the emitting region from the variability
time scale (approximately stellar).
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
Compton-GRO
Launched 1991. de-orbited 2000
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
Compton-GRO
Burst And Transient Source Experiment
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
BATSE sample light curves
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
Hardness-duration diagram
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
Duration diagram
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
The BATSE sky
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
The fireball model
The isotropic distribution observed by
BATSE prompts Rees & Meszaros to
propose the fireball model (the population
must be distant).
The basic idea is that the radiation can
only escape, if it originates in an ultrarelativistic blastwave.
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
Theoreticians playground
By 1995, about 140 theories on GRBs.
What about.......
“They are due to extra terrestrial civilizations
finding the infinite energy source – and
making a mistake during testing.”
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
Beppo-SAX
Italian-Dutch satellite,
1996-2002.
Combination of
Gamma-ray detectors
and X-ray telescope
was a unique feature.
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
GRB 970228
Detected by Beppo-SAX in Gamma-rays
Follow-up observations with the
Beppo-SAX X-ray telescope
First detection of a GRB at other wavelengths!
→ and the first precise position!
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
GRB970228 in X-rays
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
The optical afterglow
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
The origin of GRB970228
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
The post GRB970228 view
The distance scale is cosmological.
 The energy release is tremendous
(~10^53 erg in a minute)
 Most theories are off the table.

Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
The central engine
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
There is a jet!
Achromatic breaks in light curves are
interpreted as the presence of a jet.
 The actual energy release is thus much
lower than what is inferred from assuming
isotropic radiation.
 There are many more GRBs than those we
observe.

Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
ROTSE observations of
GRB990123
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
The redshift of GRB990123
Z = 1.60!
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
The brightest object
ever observed
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
The energy release
The isotropic energy release was
equivalent to the conversion of the
restmass of ~1 neutron star into energy.
GRBs can destroy life to a distance of
~100 Parsec.
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
GRB000131
Detected with Inter Planetary Network.
Position known only 3½ days after the
GRB, with a ~10 arcmin error box.
Observed with VLT, when 4 days old.
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
GRB000131 error box
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
The Gamma-ray light curve
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
Afterglow indentification
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
The SED of the afterglow
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
VLT spectroscopy
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
Record redshift
The location of Lyman forest shows that
GRB000131 was at z = 4.5.
GRB000131 remains the most distant
explosion ever observed.
Look back time is ~13Gyr.
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
The progenitor at large
From early GRB observations it was clear
that the progenitor was of ~ stellar size.
(as inferred from the variability time scale of ~ seconds)
The quest for the progenitor is a 30 year old problem!
Everything from supernovae to strange
quark stars and has been proposed.
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
GRB 980425/SN1998bw
The smoking gun
The temporal and spatial coincidence between
GRB980425 and the type Ic SN1998bw
(Galama et al. 1998)
Located in a low redshift (z=0.0085) galaxy.
Expansion velocity of 23000 ± 3000 km/s
Are (long) GRBs associated with SNe?
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
SN1998bw/GRB980425
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
GRB 980425 peculiar
Sub-luminous in γ-rays by a factor 10^4.
Optical afterglow fainter by 5-10 mags.
Not a classical burst → strong skepticism.
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
Other smoking guns
GRB 980329 – late bump on light curve
(Bloom et al., 1999)
GRB 011121/SN2001ke – late change of
SED consistent with underlying supernova.
(Garnavich et al. 2003)
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
Bloom et al.
Nature, 1999
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
GRB 030329
Localized by HETE
(Vanderspek et al. GCN #1997)
Fluence ~ 1.2 x 10^-4 erg/cm^2 →
in top 0.2% of the BATSE fluence distribution
Afterglow discovered after 1.5h, magnitude ~12!
(Price at al. 2003)
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
Afterglow spectroscopy
High resolution spectra with UVES@VLT
→ z = 0.1685
(Greiner et al., GCN #2000)
L ~ 9 x 10^51 erg (30-400 keV)
SN1998bw would be R~ 20 mag
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
Late spectroscopy
Observations obtained with
the FORS1 and FORS2
instruments on Antu and
Yepun at Paranal
Spectroscopy at 6 epochs,
from 4-32 days after the
GRB trigger
Resolution ~ 400
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
Hjorth et al.
Nature, 2003
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
Hjorth et al.
Nature, 2003
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
A Progenitor’s fingerprint
The Ic SN 2003dh unambigously identified
(J. Hjorth et al., Garnavich et al.)
Expansion velocity of 36000 ± 3000 km/s
(classifies as extreme hypernova)
Coeval with GRB 030329 to ± 2 days
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
Hjorth et al.
Nature, 2003
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
Implications
At least some long/soft GRBs are caused
by the death of a massive star
Taken together with GRB 980425, this is
compelling evidence that the death of a
massive star is the cause of long GRBs
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
Why type Ic SNe?
Characterized by the absence of
hydrogen lines and weak or absent
He/Si lines in the spectrum
→ Progenitor was a Wolf-Rayet star
which had lost its envelope (due to
a stellar wind or binary evolution)
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
Why a hypernova?
The extreme expansion velocity may be
understood as a consequence of a high
core-to-envelope mass ratio
This points towards binary evolution
(efficient stripping of envelope)
→ Easier to understand GRB penetration?
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
If a binary, then.....
Easier to understand the rarity of GRBs
(10^6 times less frequent than type II SNe)
Observed abundance anormalies could be
understood as the secondary going of as a
GRB inside the remanant of the primary.
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
Conclusions I
Long GRBs appear to be caused by the
core-collapse of a short-lived massive star.
 On a cosmological time scale, the GRB
therefore takes place nearly instantly.
 GRB therefore trace star- and galaxyformation from the first generation of
stars.

Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
The GRB 990705 host galaxy
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
The GRB000926 host galaxy
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
The distribution of GRBs
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
GRB000926: spectrum (z=2.0338)
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
Conclusions II
Quite independent of the physics of GRBs,
we can use these spectacular events to study
 The first generation of stars.
 Early galaxy formation.
 The chemical enrichment of the universe.
 The reionizaion of the universe, all the way
back to the ‘dark ages’.
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
How to discover many GRBs?
The SWIFT satellite will give100/year, but
it has limited life time.
 Alternative – discover the optical
counterparts from the ground.

You need a very wide field permanent
survey which goes sufficiently deep.
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
Absolute magnitude at 1 day
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
The afterglow
Luminosity Function
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
Discovery magnitude vs delay
Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
Requirements for
a continous all-sky survey
High time resolution, 10sec or better.
 Limiting magnitude of ~15 per exposure.
 Very efficient rejection of false events.

Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen
The double-PI on the sky
Use an array of ~100 fast Schmidt
cameras with a large CCD on each site.
 Install everything inside a glass dome to
convert it to a laboratory experiment.
 Dublicate the installation at another site,
located ~100km away (stereoscopic
coincidence imaging).

Soltan institute for Nuclear Studies
Warsaw 14.01.2005
Probing the high-redshift Universe with Gamma-ray Bursts
M.I.Andersen