Collapse of Massive Stars

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Collapse of Massive Stars

• MacFadyen
• Caltech

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Delayed SN Explosion
Accretion vs. Neutrino heating
Burrows (2001)
ac
Muller (1999)
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Pre-Supernova Density Structure
Bigger stars Higher entropy Shallower density
gradients
Woosley Weaver (1995)
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Stellar Rotation
Fukuda (1982)
no mass loss
Mass loss
Heger (2000)
No B fields
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IF Two plausible conditions occur 1. Failure
of neutrino powered SN explosion a.
complete b. partial (fallback) 2. Rotating
stellar cores j gt 3 x 1016 cm2/s THEN Rapidly
accreting black hole, (M0.1 M?/s) fed by
collapsing star (tdyn 446 s/ ?½ 10 s) Disk
formation COLLAPSAR
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Superbowl Burst
GRB Light Curve
M E/ G c2 10-6 Msun
ms variability non-thermal spectrum Compactness
? G gt 100
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Gamma-Ray Bursts

• Short g-ray flashes
• E gt 100 keV
• 0.01 lt t90 lt 1000s
• Diverse lightcurves
• BATSE detected 1/day 1000 /year/universe
• Energy
• 1052 fg-1 fW/0.1erg

• Near star forming regions
• 2 SN Ibc associations
• Supernova component in lightcurves

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135 models (1993)
Note most are Galactic and are ruled out for
long bursts
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3. Palomar lt 1 day
2. BeppoSAX (X-ray)
Keck spectrum z1.60 Eiso 3x1054 erg
Msunc2 9th mag flash
6-33 hrs
GRB 990123
34-54 hrs
4. HST 17 days
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1. CGRO 1o
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Hyper-accreting black hole or high field neutron
star (rotating)
GRB photons are made far away from engine. Cant
observe engine directly in light. (neutrinos,
gravitational waves?) Electromagnetic process or
neutrino annihilation to tap power of central
compact object.
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SN2003dh/GRB030329
Hjorth et al (2003)
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Well-localized bursts are all long-soft short-h
ard bursts ?
hardness
Duration (s)
Kulkarni et al
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GRB central engine

• Relativity (SR GR)
• Magnetic Fields
• Rotation
• Nuclear Physics
• Neutrinos
• EOS
• Turbulence
• 3D
• Range of Lengthscales

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1st Collapsar Simulations

• pre-SN 15 Msun Helium star
• Newtonian Hydrodynamics (PPM)
• alpha viscosity
• rotation
• photodisintegration (NSE alpha, n, p)
• neutrino cooling, thermal URCA optically thin
• Ideal nucleons, radiation, relativistic
  degenerate electrons, positions
• 2D axisymmetric, spherical grid
• self gravity
• Rin 9 Rs Rout 9000 Rs

MacFadyen Woosley (1999)
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Initial Pre-Supernova Model (KEPLER 25 Msun)
He 8.06 Msun Fe 1.9 Msun
Collapse velocity 10,000 km/s
T
r
Angular momentum at Last stable orbit 1.5 x 1016
cm2 s-1 (Kerr) 4.6 x 1016 cm2 s-1 (Schwarzschild)
j
Heger, Langer Woosley (1999)
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Disk Formation Movie
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a 0.1 ltMgt 0.07 Msun /s 1.3 x 1053 erg/s
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Use 1D neutrino cooled slim disk models from
Popham et al (1999).
spin
mass
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Jet Birth
Thermal energy deposition focused by toroidal
funnel structure
T 5.7 ms E 5 x 1050 erg/s Edep 2.8 x 1048
erg
. . Ejet f Maccc2
fmax .06 - .4
MHD nn
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Relativistic Jet Movie
Zhang, Woosley MacFadyen (2003, ApJ March 21)
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Red Supergiant R1013 cm
Wolf-Rayet Star Rfew x1010 cm
Blue Supergiant R1012 cm
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Relativistic Kelvin-Helmholtz
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t7.598s
t7.540s
. Min . 1/2 Mout
gt Outflows
MacFadyen Woosley (1999)
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Nickel Wind Movie
Nickel Wind
T gt 5 x 109 K
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Disk Outflow Diagram
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Supernovae
Type I No Hydrogen
Type II Hydrogen
Ia WD cosmology
Ib, Ic exploding WR
core collapse massive stars
thermonuclear old pop. E galaxies
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Exploding star ? Supernovae

• Radioactive decay of Ni56
• tail of Type II, ALL of Type I
• Type I compact star WD or W-R
• Eexp -gt adiabatic expansion not light
• no Ni56 -gt no Supernova
• SN 1998bw 2003dh need 0.5 Msun

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Do all collapsars make supernovae?No. If
Nickel is made in wind, it depends on angular
momentum of star.

• jisco lt j lt jn efficient cooling GRB only
• jn lt j lt jg semi-efficient cooling GRB
  supernova
• j gt jg inefficient cooling supernova only
• j lt jisco nothing
• note supernova ? hypernova (Egt1052 erg, M(Ni) gt
  0.3M?)

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SN 1998bw/GRB 980425
NTT image (May 1, 1998) of SN 1998bw in the
barred spiral galaxy ESO 184-G82 Galama et al,
AAS, 138, 465, (1999)
WFC error box (8') for GRB 980425 and two NFI
x-ray sources. The IPN error arc is also shown.
1) Were the two events the same thing? 2) Was
GRB 980425 an "ordinary" GRB seen off-axis?
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What made SN1998bwGRB980425?
1. Accretion powered hypernova w/ Nickel wind
MacFadyen (2002) E 1052 erg, M(Ni)0.5 M?
2. Brief jet tengine ? tjet Engine dies
before jet breakout. Mildly relativistic shock
breakout

GRB from G3 shock breakout (Tan et al 2001,
Perna Vietri 2002)
MacFadyen (1999)
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Fallback in weak SN explosions
Shock reaches surface of star but parts of star
are not ejected to infinity.
MacFadyen, Woosley Heger (2001)
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Same star exploded with a range of explosion
energies. Significant accretion for thousands of
seconds to days.
Fallback accretion
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Principle Results

• Sustained accretion .1 Msun/s forgt10s
• Jet formation and collimation
• Sufficient energy for cosmo. GRB
• Neutrino cooling photodissociation allows
  accretion
• Massive bi-conical outflows develop
• Time-scale set by He core collapse
• Fallback -gt v. long GRB in WR star or asymmetric
  SN in SG

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Conclusions

• long GRBs from rotating WR stars. tengine gt
  tescape
• Need SN failure angular momentum
• Low metallicity, binary can help
• SN IF nickel is made. GRB/SN association. Type
  Ibc.
• SN/GRB ratio may depend on angular momentum.
• Nickel wind can explode star -gt hypernova
• H env. Type II (no GRB), no H Type I GRB
• Jet instabilities -gt variability, intermittancy
• Unique nucleosynthesis, r-process?
• Fallback -gt asymmetric SN, very long GRBs.
• magnetic models worth attention