Collapse of Massive Stars A.MacFadyen Caltech

Muller (1999) “Delayed” SN Explosion acac Accretion vs. Neutrino heating Burrows (2001)

Pre-Supernova Density Structure Woosley & Weaver (1995) Bigger stars: Higher entropy Shallower density gradients

Fukuda (1982) Heger (2000) Stellar Rotation no mass loss Mass loss No B fields

IF Two plausible conditions occur: 1. Failure of neutrino powered SN explosion a. complete b. partial (fallback) 2. Rotating stellar cores j > 3 x cm 2 /s THEN Rapidly accreting black hole, (M~0.1 M  /s) fed by collapsing star (t dyn ~ 446 s/  ½ ~ 10 s) Disk formation COLLAPSAR

Superbowl Burst ms variability + non-thermal spectrum Compactness   GRB Light Curve M = E/  c 2 ~ M sun

Gamma-Ray Bursts Short  -ray flashes E > 100 keV 0.01 < t 90 < 1000s Diverse lightcurves BATSE detected 1/day = 1000 /year/universe Energy ~ f  -1 f  erg Near star forming regions 2 SN Ibc associations Supernova component in lightcurves

135 models (1993) Note: most are Galactic and are ruled out for long bursts

GRB CGRO ~1 o 2. BeppoSAX (X-ray) 6-33 hrs hrs ~ 1’ 4. HST 17 days 3. Palomar < 1 day Keck spectrum z=1.60 E iso = 3x10 54 erg ~ M sun c 2 9 th mag flash

GRB photons are made far away from engine. Can’t observe engine directly in light. (neutrinos, gravitational waves?) Electromagnetic process or neutrino annihilation to tap power of central compact object. Hyper-accreting black hole or high field neutron star (rotating)

SN2003dh/GRB Hjorth et al (2003)

Well-localized bursts are all “long-soft” “short-hard” bursts ? Duration (s) hardness Kulkarni et al

GRB central engine: Relativity (SR & GR) Magnetic Fields Rotation Nuclear Physics Neutrinos EOS Turbulence 3D Range of Lengthscales

1 st 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 R in = 9 R s R out = 9000 R s MacFadyen & Woosley (1999):

Heger, Langer &Woosley (1999) Angular momentum at Last stable orbit: 1.5 x cm 2 s -1 (Kerr) 4.6 x cm 2 s -1 ( Schwarzschild) Initial Pre-Supernova Model (KEPLER 25 Msun) He 8.06 Msun Fe: 1.9 Msun j T  Collapse velocity = 10,000 km/s

Disk Formation Movie

 = 0.1 = 0.07 M sun /s = 1.3 x erg/s

spin mass Use 1D neutrino cooled “slim” disk models from Popham et al (1999).

.. E jet = f M acc c 2 MHD T = 5.7 ms E = 5 x erg/s E dep = 2.8 x erg Jet Birth Thermal energy deposition focused by toroidal funnel structure f max ~

Relativistic Jet Movie Zhang, Woosley & MacFadyen (2003, ApJ March 21)

Red Supergiant R~10 13 cm Blue Supergiant R~10 12 cm Wolf-Rayet Star R~few x10 10 cm

Relativistic Kelvin-Helmholtz

t=7.598s t=7.540s. M in. ~ 1/2 M out => Outflows MacFadyen & Woosley (1999)

Nickel Wind Movie “Nickel Wind” T > 5 x 10 9 K

Disk Outflow Diagram

Supernovae Ia WD cosmology Type II Hydrogen Type I No Hydrogen Ib, Ic exploding WR thermonuclear old pop. E galaxies core collapse massive stars

Exploding star  Supernovae Radioactive decay of Ni56 tail of Type II, ALL of Type I Type I compact star WD or W-R E exp -> adiabatic expansion not light no Ni56 -> no Supernova SN 1998bw & 2003dh need 0.5 M sun

Do all collapsars make supernovae ? No. If Nickel is made in wind, it depends on angular momentum of star. 1.j isco < j < j efficient cooling GRB only 2.j < j < j  semi-efficient cooling GRB + supernova 3.j > j  inefficient cooling supernova only j < j isco nothing note: supernova  hypernova (E>10 52 erg, M(Ni) > 0.3M  )

NTT image (May 1, 1998) of SN 1998bw in the barred spiral galaxy ESO 184-G82 [Galama et al, A&AS, 138, 465, (1999)] WFC error box (8') for GRB and two NFI x-ray sources. The IPN error arc is also shown. 1) Were the two events the same thing? 2) Was GRB an "ordinary" GRB seen off-axis? SN 1998bw/GRB

2. “Brief” jet t engine  t jet Engine dies before jet breakout. Mildly relativistic shock breakout MacFadyen (1999) What made SN1998bw+GRB980425? 1. Accretion powered hypernova w/ Nickel wind MacFadyen (2002) E~ erg, M(Ni)~0.5 M  GRB from  ~3 shock breakout (Tan et al 2001, Perna & Vietri 2002)

Fallback in weak SN explosions Shock reaches surface of star but parts of star are not ejected to infinity. MacFadyen, Woosley & Heger (2001)

Fallback accretion Same star exploded with a range of explosion energies. Significant accretion for thousands of seconds to days.

Principle Results Sustained accretion.1 Msun/s for>10s 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 -> v. long GRB in WR star or asymmetric SN in SG

Conclusions long GRBs from rotating WR stars. t engine > t escape 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 -> hypernova –H env. Type II (no GRB), no H Type I + GRB Jet instabilities -> variability, intermittancy Unique nucleosynthesis, r-process? Fallback -> asymmetric SN, very long GRBs. magnetic models worth attention