Clues of GRB progenitors

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Relevance of GMT for GRB studies
Ram Sagar ARIES, NainiTal, India
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Overview

• Introduction to Gamma-Ray Bursts (GRBs)
• Discovered in 1967 by the Vela satellites
• Era of BATSE on CGRO 1991
• Beppo-SAX and HETE-II-- Afterglow era
• Multi-wavelength observations - 1997
• Swift multi-wavelength era 2005
• GRBs in GMT era Near IR and High resolution
  spectroscopy

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Introduction to Gamma Ray Bursts (GRBs)

• Discovered in 1967 by the Vela satellites but
  known to public in 1973
• Short lived (103 103 sec)
• Extremely luminous gamma-ray sources (release
  10 50-52 ergs energy)
• Non thermal spectra
• Short intense flashes of ? rays at Cosmological
  distances 0.008 lt z lt 6.3
• Hardness ratio F(50-100 Kev)/F(25-50 Kev)
  

Classification Evidence for 2 GRB classes
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The GRB light curves
970508
990316
990123
980703
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• BATSE on CGRO 1991 Statistical analyses
  started
• Isotropic distribution ? Cosmological distances

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• Bi-modal distribution of GRBs
• Long duration T90 gt 2 sec
• mean 25 sec and
• soft ?-ray spectrum
• Short duration T90 lt 2 sec
• mean 0.3 sec and
• Hard ?-ray spectrum

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GMT observations may provide better
classifications??
Bloom et al. 2005, Zhang Bing 2007
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Possible progenitors
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GRB Afterglow and Fireball model
The star collapses to form a black hole matter
is ejected
Layers of ejecta collide with each other to form
internal shocks
The ejected matter finally hits the ambient
medium driving an external shock into it
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GRB Afterglow and Fireball model
Shocks interact with ISM, the electrons gyrate
around the magnetic field and emits non-thermal
synchrotron radiation ranging from X-ray,
optical to radio known as Afterglows
Cartoon of fireball model
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GRBs vs Afterglows 2 phases

• Burst Afterglow
• - ray band alone
  multi-wavelength phenomena

Short lived seconds long lived
days to years depending upon the
burst band of observation

• Lessons from multi-wavelength observations of
  300 afterglows
• ( 250 in X-ray 175 in optical and 50 in Radio)
• Story of Smoking gun?? GMT ??
• Probe constraints on the current theoretical
  models
• Surroundings distance energetics
• Light curve break collimation
• Supernova association progenitors

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Sensitivity discovery space
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Angular resolution discovery space
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Afterglows of GRBs
Jet Signatures in Optical/X-ray
Temporal slope ? spectral slope ?, in the
synchrotron afterglow model with no spectral
breaks, are related as
F? (t, ?) ? t -? ? -?
where ? and ? are functions of p, p is the power
law exponent of the electron Lorentz factor
Achromatic break in light curves f?(t) 21/s f0
/ ( t/tj )?1s ( t/tj )?2s1/s fg
As a relativistic jet decelerates we see a larger
fraction of the emitting surface until we see the
edges of the jet. These leads to a panchromatic
break slope of the the afterglow light curve.
?j
E? (1 - cos?j) Eiso,?
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GRB 021211 afterglow, Optically dim burst

• Optically dim, 3 mag fainter than GRB 990123
• Detected 90 sec after the burst
• R band, single power law 11 min to 35 days
  with decay index ? 1.1
• Compared with GRB 000630 GRB 020224
• Similar GRBs have R 23 mag, one day after the
  burst
• It would have been classified as optically dark
  burst in absence of rapid follow-up
• Observed at very early hours from India,
  courtesy Longitudinal advantages
• Possible explanations
• Intrinsic faintness High red shift and
  extinction
• Advantage with GMT near-IR capabilities ??

GRB 021211, Pandey et al., 2003
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Afterglow temporal breaks
GRB 010222, Sagar et al. (2001)
GRB 030226, Pandey et al., (2004)
GMT near-IR observations are possible for similar
objects at high Z -gt Relevance
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Overlapped variability in the optical afterglow
light curve
Deviation from simple power law Bumps Wiggles
in the light curve
GRB 000301c (Sagar et al. 2000), GRB 021004
(Pandey et al. 2003)
Explanation
Complex density structure around the burst (Wang
Loeb 2000), Refreshed shocks (Rees Meszaros
1998), Patchy shell model (Kumar Piran 2000),
Microlensing (Garnavich et al. 2000)
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GRB 030329/SN 2003dh (Resmi et al 2004)
Monitored from 3 hours to 33 days After the
burst UBVI, earliest observations Peculiar
afterglow light curves with overlapped
variability and SN 2003dh contribution
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Swift era 2005 (launched in Nov 2004)
X-ray and optical behavior dissimilar Early steep
decay X-ray
Many afterglows exhibit jet breaks relatively
early Afterglows with jet break beyond 2 days
are not rare GRB 000301C, GRB 011211 and GRB
021004
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No supernova associated with two long duration
GRBs GRB 060505 GRB 060614
Could GRB 060505 GRB 060614 be short GRBs or at
higher redshifts?
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GRB 050724
The outflows of SHBs are collimated
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Caveats

• SHB facts
• Closer on average than
• long bursts ltzgt0.3
• Occur in both spiral
• elliptical galaxies (cf SN Ia)
• GRB/host offsets do not
• trace the blue light of their
• host galaxies
• Release less energy
• Central engines are
• long-lived

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• Long duration GRBs are most probably produced
  from stellar-like systems
• Some clues
• Association with star-forming regions in galaxies
• GRB 980425 ? SN 1998bw (Galama et al. 1998)
• GRB 030329 ? SN 2003dh (eg. Hjorth et al. 2003)
• At least, some GRBs are deaths of massive stars!
  -- especially from massive He stars (or WR stars)
• Chandra observations indicates presence of Fe
  lines in GRB 991216 GRB 000926 and 3 others
• Large amount of dust extinction (Av 1 mag)
  high star formation rate in the star forming host
  galaxies
• While Short duration GRBs are most likely formed
  with a merger of compact objects

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• GRBs as distance indicators alternative to SNe
  Ia
• can be discovered out to extremely high
  red-shift (Z 15-20)
• Cosmic star formation theory (10 GRBs have Z gt
  6)
• so far only one GRB 050904 have Z 6.3
• First generation star Z20
• First generation quasar Z7 and CMB Z 1100
• Unveil the dark universe and the re-ionization
  history
• of the Universe

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Star formation galaxy assembly

• There are discrepancies at z1 to z3 IMF??
• The star-formation history beyond z5 is even not
  understood

Instantaneous SFR
Inferred SFR
? z gt 5
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Internal properties of high-z galaxies

• GMT will be able to probe chemistry and dynamics
  of high-z galaxies and study their assembly with
  100 pc resolution.
• Use large single IFUs for detailed studies at
  moderate z
• Use multiple deployable IFUs to obtain population
  samples

Star-formation _at_ z 0.1 with HST (H?
continuum image)
Star-formation _at_ z 1.4 with GMT (1.6?m image,
1 hour exposure)
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Physics of galaxy formation

• GMT will be able to map the physical
  properties of galaxies over the redshift range
  (1ltzlt5)
• Star formation rate
• Metallicity maps
• Extinction maps
• Dynamical masses
• Gas kinematics

z 0.0
z 2.5
z 5.5
TMT IRMOS-UFHIA team
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SFH of old galaxies at zgt2

• NIR spectra star-formation histories, ages,
  abundances
• GMTGLAONIRMOS spectra to J24.5 in 5 hrs
• With better NIR detectors ? may be reach J27!

GMTGLAONIRMOS (simulation by P.McCarthy)
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Ly-? in high-z galaxies

• GLARE survey 36hr exp with GeminiGMOS Stanway,
  Glazebrook et al., 2006

• Simulated observation of z6 Ly? galaxy 30hr
  with GMTGMACS McCarthy 2007

Ly? flux (erg/cm2/s)
Ly? flux gt 5x10-18 erg/cm2/s
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Summary

• To observe faint GRB afterglows in near-IR
• GRB Z
  Tb(days) H mag
• 990510 1 2
  20
• ? 10
  11 24
• VLT 23 mag for 1 hour Exposure time
• GRB jet configuration absence of achromatic
  breaks
• Faint GRB afterglows so that dark GRBs can be
  studied.
• High resolution spectroscopic and near-IR
  imaging of the host galaxies -gt learn more
  about the GRB classification scheme and unveil
  the dark universe and the re-ionization history
  of the Universe

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• GRBs as distance indicators alternative to SNe
  Ia
• can be discovered out to extremely high
  red-shift (Z 15-20)
• Cosmic star formation theory (10 GRBs have Z gt
  6)
• so far only one GRB 050904 have Z 6.3
• First generation star Z20
• First generation quasar Z7 and CMB Z 1100

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Thanks
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Optical prompt emission in case of GRB 990123
(Galama et al. including ARIES GRB Team, 1999,
Nature). The Gamma-ray light curve with the ROTSE
optical observations (in Red-bands) are shown