Gamma-ray bursts and hypernovae

1
Gamma-ray bursts and hypernovae

• Konstantin Postnov
• Sternberg Astronomical Institute
• Moscow

Erice-2004, July 6, 2004
2
Outlook

• Introduction
• GRB as superstrong cosmic explosions
• Association with supernovae a critical view
• Thermal effects in ambient plasma
• Conclusions

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BATSE rate 1 per day No repetions, full isotropy
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Brief course of history of GRBs

• 1967- Discovery by American military Vela
  satellite
• 1973 Declassified for scientific community
• End of 1970s Konus experiments onboard
  Russian Veneras
• (E.P.Mazets et al)
• 1991-2000 BATSE (CGRO) era. Largest
  homogeneous data (a few thousands) on GRBs.
  Debates on galactic vs extragalactic origin
• 1997- Afterglow era. Discovery of afterglows in
  X-ray (BeppoSAX, 1997), optical, radio. Triumph
  of cosmological model for (long) GRB origin.
  Multivawelength GRB astronomy
• 1998 possible association of GRB980425 with
  nearby peculiar type Ic SN1998bw. Start of
  hypernova era (?)

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General properties

• Observed
• Duration 0.1-1000 s
• Fluence S10-7-10-3 erg/cm2
• Spectrum nonthermal,
• 10keV-100 MeV
• Variability high, 1-10 ms
• Rate 1 per day
• Location z0.17-4.5, (but 980425 z0.0085),
  star-forming galaxies
• Associated events X-ray (100), optical (70),
  radio (50) afterglows
• F(t)t-a a1-2
• Environment signatures transient X-ray
  em./abs. lines, metal rich material

• Derived (for long GRBs only!)
• Isotropic energy release
• E?4pdl2/(1z) 1051 -1054 erg (but 980425
  1048)
• Evidence for jets from afterglow breaks
  ?j0.01-0.1
• Points to standard energy release
  ?E1050-1051erg equally shared in kinetic energy
  and radiation
• Photon energy correlations
• vF?Eiso
• Association with SN Ib/c

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GRB spectra

• Two power laws smoothly joined together (Band et
  al 1993)

Slopes a, ß and peak energy Epeak vary with time
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Generally, spectrum gets softer
...but not always
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and even gets harderGRB 941017 (Gonzalez et
al. 2003)
EGRET-TASC detection Duration 150 s A new,
very hard component appeared E2 FEE1,
Epeakgt200 MeV Signals hadronic component
(UHECR) with subsequent photomeson
interactions? (Dermer Atoyan,2004)
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(Gonzalez et al.03)
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Amati et al. (02,03) Eiso-z, Ep-Eiso
correlations
22 events with known z and spectra
Lg Epeak0.45 lg Eiso
Are older GRB more energetic?
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Explanation of GRB spectra (not fully
satisfactory)

• Standard synchrotron shock model (SSM)
• Optically thin synchrotron radiation by
  energetic electrons left to radiate without
  further acceleration. Electrons are accelerated
  by the Fermi mechanism in relativistic shocks
  created by the central engine (dN/dEE-p,
  p2.2-2.3)
• BUT many individual GRB do not fit this!
  Additional acceleration, IC, change in electron
  energy index p with time, etc., etc., etc. are
  invoked

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Basic model ultrarelativistic (Ggt100) jets
associated with hyperstrong (1051 erg)
explosion (a hypernova)
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• Term hypernova introduced by B.Paczynski
  (1998) according to energy release in an
  explosive cosmic event
• Nova (thermonuclear explosion on white dwarf
  surface) ?E 10-9M?c21045erg
• galactic rate 1 per a few year
• Supernova (core collapse of massive star,
  SNII,Ib,Ibc or th/n explosion of a WD with
  MCh(mPl/mp)3mp 1.3 M?)
• ?E 10-1M?c21053erg (binding energy of
  neutron star, mostly in neutrino)
• kinetic energy 1050erg (binding energy
  of stellar envelope)
• galactic rate 1 per a few 10s years
• ? Hypernova (core collapse associated with black
  hole formation? Requires the most extremal
  conditions e.g.B1015G, rapid rotation, etc.)
• ?E? 1051-52erg
• kinetic energy gt1051erg
• galactic rate 1 per a few 104-106 years

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Evolution of massive stars Mlt25 M?? neutron
star Mgt25 M?? black hole Hypernova MNigt0.1
M? Ekingt1 foe Faint supernova
Nomoto et al.2004
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Fireball models for GRBs

• Rees Meszaros (1992, 1994) Recent review
  Piran 2004
• Thermal energy of explosion is converted to
  kinetic energy of thin baryon shell with
  ultrarelativistic speed (Ggt100) to avoid
  compactness problem and explain non-thermal
  spectra
• GRB is produced by internal (most likely) shocks
  within the expanding shell, or by external shock
  in inhomogeneous ISM.
• Internal shocks ? GRB itself, external shock in
  ISM ? X-ray, optical, radio emission of the GRB
  afterglow
• Initial interaction of GRB ejecta ? Reverse shock
  propagating inward and decelerating fireball
  ejecta. Erases the memory of the initial
  conditions. Expansion approaches self-similarity
  (Blandford McKee solution, 1976) GBMr-3/2
• (simply from E0(4p/3)r3n0 mpc2G2 )
• Parameters E0, no (const or 1/r2), G0, p, eB, ee

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ES
RS
IS
G1
G2gt
?
Afterglow
GRB
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Optical afterglows (synchrotron emission from
relativistic blast wave in ISM)
Early reverse shock in the ejecta
990123
Late external shock in ISM
021211
Breaks in ag lc decelerated jet
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Jet beaming effect in the GRB light curves
T1/G(t)t3/8
?0
G(r)r-3/2t-3/8 tr/G2
r
Emitting area Ar2?2r2/G2G4 t2/G2t10/8,
?lt?0,tlttj
Ar2?02G4t2t1/2, ?gt?0, tgttj
T(tj)?0
? A increases slower after tgttj
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Observed emission(emitting area)x(specific
intensity) For SSM, I(B2?e2)
G(eBG2)(eeG2)GG5t-15/8 so F(tlttj) AxI
t10/8t-15/8 t-5/8 F(tgttj)
t1/2t-15/8 t-11/8
?00.16(n0/E0,iso)1/8(tj/days)3/8 E?E0,iso(?o2/2
) E0,iso4pdl(z)2S/(1z)
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Evidence for associated SNe

1. GRB980425 and peculiar type Ib/c SN 1998bw in
   nearby galaxy ESO184-g8 (z0.0085)

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1998bw model light curve
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SN2002ap spectral evolution modeling
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2. Bumps in the late (10-30 days) optical
afterglows
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Yet another case GRB 021211
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Special cases GRB 030329 nearest (z0.168),
brightest (S10-4erg/cm2)
Host a SMC-like star-forming galaxy
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SN 2003dh signature in light curve?
Difficult to directly accommodate!
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SN2003dh spectral apperance (Matheson et al 2003)
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Zooming in MMT spectra
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Also in the VLT spectra
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Detailed light curve
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GRB030329 but earliest optical spectra (BTA 6m
telescope, Sokolov et al. 2003)
difficult to explain by shock breakout as pre-SN
must be compact!
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Light-curve residuals could supernova do this?
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Optical variability and polarisation suggests
structured environment
Greiner et al. 2003
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List of GRB/SN associations
s
(from Dar 2004)
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W49B a hypernova remnant? (Keohane et al. 2004)
red molecular hydrogen 2.12µ (Palomar Hale
WIRC) green 1.64µ FeII (Palomar Hale
WIRC) blue Fe Ka (Chandra). No NS. HN
explosion in a molecular cloud a few thousand
yrs ago?
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Clues from radio observations

• Radio scintillations in ISM Fresnel radius 5
  µas?direct measurement of angular size ? evidence
  for relativistic motion (970508, 030329)
• Vapp 4c

Frail et al. 1997
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Radio observations of GRB030329 (Taylor et al
2004)

1. Directly reveal apparent superluminal expansion
   v3-5c, in accord with relativistic blast wave
   model for GRB afterglows
2. Inconsistent with cannonball model prediction for
   plasmoid superluminal motion (Dado et al 2004)
   (NB general problem for CB model is absence of
   rapid radio diffractive scintillations in
   GRB030329, though the expected anglular size of
   plasmoids 0.01 µas ltlt Fresnel (5 µas ) scale)

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But radio luminosities of GRB and SN1b/c are
strongly different (Berger et al.2003)
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SN/GRB rates

• SNIbc in spiral galaxies 0.2/100yrs/1010L?(B)
• Local univesre 108L?(B) Mpc-3
• SNIbc rate 2 104Gpc-3
• GRB rate 250 Gpc-3 (factor 3-10 uncert. due
  to collimation)
• Only a few percent of SNIbc can be associated
  with GRBs (unlike CB model). Additional
  conditions (e.g. binarity etc.) must be imposed
  on the progenitors

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Standard energy issue

• Postnov, Prokhorov and Lipunov 1999, 2001 (idea)
• Standard explosions ?E 5x1051 ergs
• Structured jets

Frail et al. 2001 standard energy from
jet-corrected afterglow observations. Berger et
al. 2003 structured jets from radio calorimetry
of GRB 030329, 980425
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Jet-corrected energy release (Frail et al)
Beaming-correction factor for the rate/energy
30-200
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Radio calorimetry structured jet(Berger et al.
2003)
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Current models universal jet vs uniform jet
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Recent discoveries Light echo on dust for GRB
031203 (loc. INTEGRAL, X-ray rich)
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GRB031203 SN 2003lw appears
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HETE2 GRB-X-ray rich-XRF (Lamb et al. 2003)
Apparently continuous transition GRBgtX-ray
richgtXRF
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X-ray flashes XRF 020903 localization
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XRF 020903 host galaxy spectrum
Z0.251 Star-forming galaxy
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Thermal effects in ambient plasma(Kosenko,
Blinnikov, Sorokina, PK, Lundqvist 2001, 2002)
Bisnovatyj-Kogan Timokhin 1997 First
consideration of environmental effects
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Fading X-ray emission lines in 011211
Reves et al XMM observations of fading (10 ks)
emission lines
Kosenko et al 2002 thermal cooling of
plasma clouds heated by GRB
N106 1-3AU-sized clds ne1011 cm-3 within 0.1
pc are needed
51
Structured environment from X-ray and optical
variability
Jakobsson et al.2004, ?t1 hr in optical
and X-ray afterglows
0.5-10 keV
3-5 AU structures!
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Mini-SN effects (Blinnikov Postnov 1997) on
clouds
1.Optical thickness increases with plasma cooling
? appearance of effective photosphere
2. Clouds cool down producing bumps in
afterglow lc
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Statistical analysis of GRB distribution inside
host galaxies (Dasha Kosenkos talk on Wed. July
7)
Bloom et al 2000, 2001 Tsvetkov et
al 2001 Kosenko et al 2004
Basic idea to compare GRB distribution with
other astronomical objects (SNe, XRB)
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Problem GRB error boxes are (still) a few
arcsec-arcmin ? no straightforward comparison can
be made
Quantile-diagrams (surface density)
DM NFW, rs 15 kpc (right) rs 4 kpc (left)
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Quantile diagrams for error-weighted GRB positions
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Error-weighted GRB distribution vs NFW and
Burkert DM profiles
rs 15 kpc
rs4 kpc
Dark matter NFW profile (cuspy) ?(r)
1/(r/rs)(1(r/rs))2
Burkert (w/o cusp) ?(r) 1/(1r)(1r2)
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Central engine

• Requirements
• Energy 1051 erg (thermal or Poynting-dominated)
• Collimation ?01-20 degrees
• Long short GRBs (two different engines?)
• Rate 0.1-1 of SN rate
• Variability dt1 ms ? compact object GRB
  duration T10-100 s ? prolong activity
• Models
• Collapsar 10 M? black hole 0.1 M? accretion
  disk formed in a hypernova explosion
• Poynting-dominated energy release by rapidly
  rotating strongly magnetized newborn neutron star
  (Usov 1992)
• Binary neutron star merging (for short GRBs)

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Conclusions (statements)

• GRBs are (rare) violent cosmic explosions in
  remote galaxies some of them are associated with
  extremely strong (Ekingt 1051 erg) peculiar SNe
  (hypernovae)
• GRB power (1044erg/yr/Mpc3) is comparable with
  UHECR power
• GRB explosions produce ultrarelativistic jets and
  drive strong shocks in the ambient medium
• Environmental effects are important in shaping
  GRB afterglows
• We understand better GRB afterglows than GRB!

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Conclusion (Issues to be solved)

• Are all GRB (including short/hard) and XRF
  really universal (jets? energies? Off-axis jets?)
• Do GRB really associate with core-collapse
  supernovae and (rotating) black hole formation?
• Which is the mechanism for gamma-ray emission
  (relativistic shocks? If yes, internal vs
  external shocks?)
• Hot (fireball) or cold (Poynting-dominated) jets?
• Association with dark matter? (Are there
  elliptical hosts?)
• Close expectations SWIFT mission (sep 04) X-op
  afterglows, rapid alerts, good statistics
  (100/yr)
• More remote future GLAST mission (06),
  high-energy neutrinos(?), gravitational waves(?)