Download Implication of Observations for Gravitational Wave Burst Sources

What is a Gamma-Ray Burst?
• Short g-ray flashes • Near star
E > 100 keV
forming regions
• 0.01 < t90 < 1000s
• 2 SN Ibc
• Diverse lightcurves
associations
• BATSE detected
• Supernova
1/day = 1000
component in
/year/universe
lightcurves
• Energy
~ 1052 fg-1 fW/0.1erg
GRB Light Curve
Superbowl Burst
M = E/ G c2 ~ 10-6 Msun
ms variability + non-thermal spectrum
Compactness  G > 100
2. BeppoSAX (X-ray)
3. Palomar < 1 day
Keck
spectrum
z=1.60
Eiso =
3x1054 erg
~ Msunc2
9th mag
flash
6-33 hrs
GRB 990123
34-54 hrs
~ 1’
4. HST 17 days
1. CGRO ~1o
135 models (1993)
Note: most are
Galactic and are ruled
out for long bursts
Hyper-accreting black hole or high field neutron star (rotating)
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.
Well-localized bursts are all “long-soft”
“short-hard” bursts ?
hardness
Duration (s)
Kulkarni et al
SN 1998bw/GRB 980425
NTT image (May 1, 1998) of SN
1998bw in the barred spiral galaxy
ESO 184-G82 [Galama et al, A&AS,
138, 465, (1999)]
1) Were the two events the same
thing?
2) Was GRB 980425 an "ordinary"
GRB seen off-axis?
WFC error box (8') for GRB
980425 and two NFI x-ray
sources. The IPN error arc is
also shown.
GRB991121
Bloom et al (ApJL,2002)
GRB030329/SN2003DH
extremely close = 800 Mpc
see also: Hjorth et al , Fox et
al Nature (2003)
SN 1998bw/GRB 980425
The supernova - a Type Ic - was very unusual.
Large mass of 56Ni 0.3 - 0.9 solar masses;
(note: jets acting alone do not make 56Ni)
Sollerman et al, ApJL, 537, 127 (2000)
McKinzie & Schaefer, PASP, 111, 964, (1999)
Extreme energy and mass
> 1052 erg > 10 Msun
Iwamoto et al., Nature, 395, 672 (1998)
Woosley, Eastman, & Schmidt, ApJ, 516, 788 (1999)
Mazzali et al, ApJ, 559, 1047 (2001)
Exceptionally strong radio source
Li & Chevalier, ApJ, 526, 716, (1999)
Relativistic matter was ejected
1050 - 1051 erg
Wieringa, Kulkarni, & Frail, A&AS, 138, 467 (1999)
Frail et al, ApJL (2001), astroph-0102282
Probability favors the GRB-SN association
Pian et al ApJ, 536, 778 (2000)
Merging neutron star black hole pairs
Strengths:
a) Known event
b) Plenty of angular momentum
c) Rapid time scale
d) High energy
e) Well developed numerical models
Ruffert & Janka, Rosswog et al, Lee et al, Aloy et al
Weaknesses:
a) Outside star forming regions
b) Beaming and energy may be inadequate for long bursts
But this model may still be good for a class of bursts called
the “short hard” bursts for which we have no counterpart information
yet (SWIFT).
Requirements on the Central Engine
and its Immediate Surroundings
(long-soft bursts)
• Provide adequate energy at high Lorentz factor
• Collimate the emergent beam to approximately 0.1 radians
• In the internal shock model, provide a beam
with rapidly variable Lorentz factor
• Allow for the observed diverse GRB light curves
• Last approximately 10 s, but much longer in some cases
• Explain diverse events like GRB 980425
• Produce a (Type Ib/c) supernova in some cases
• Make bursts in star forming regions
GRB central engine:
•
•
•
•
•
•
•
•
•
Relativity (SR & GR)
Magnetic Fields
Rotation (progenitors)
Nuclear Physics
Neutrinos
EOS
Turbulence
3D
Range of Lengthscales
“Delayed” SN Explosion
Accretion vs. Neutrino heating
Burrows (2001)
a
c
Muller (1999)
Pre-Supernova Density Structure
Bigger
stars:
Higher
entropy
Shallower
density
gradients
Woosley & Weaver (1995)
Failure of delayed mechanism
Bigger stars:
1. Accrete faster & longer
2. Larger binding energy & smaller explosion
energy
explosion
binding
Fryer, ApJ, 522, 413 (1999), Burrows (1999)
Stellar Rotation
Mass loss
Fukuda
(1982)
no mass loss
Heger
(2000)
No B
fields
Collapsars
A rotating massive star whose core collapses to a
black hole and produces an accretion disk.
Type
Mass/sun
BH
I
15-40 He
prompt
II
10-40 He
delayed
III
>130 He
prompt
Time Scale Distance
20 s
Comment
all z
neutrino-dominated disk
20 s – 1 hr
all z
black hole by fall back
~20 s
*(1+z)
z>10?
time dilated, redshifted
very energetic, pair
instability, low Z
Type I is what we are usually talking about.
The 40 solar mass limit comes from assuming that all stars above 100 solar
masses on the main sequence are unstable (except Pop III).
IF
Two plausible conditions occur:
1. Failure of neutrino powered SN explosion
a. complete
b. partial (fallback)
THEN
2. Rotating stellar cores
j > 3 x 1016 cm2/s
Rapidly accreting black hole, (M~0.1 M/s)
fed by collapsing star (tdyn ~ 446 s/ ½ ~ 10 s)
Disk formation
COLLAPSAR
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, pseudo-Newtonian (PW)
• Rin = 9 Rs Rout = 9000 Rs
MacFadyen & Woosley (1999):
Collapsar Disk Animation
PPM hydrodynamics, Paczynski-Witta potential,
EOS, neutrino cooling, nuclear reactions, a viscosity
Stellar collapse w/ rotation.
Density structure. No disk, no wind.
Note: Accretion shock, funnel clearing, pole to
equator density contrast, fluctuating polar density
Initial model: 15 Msun Helium (Wolf-Rayet) star
evolved with mass loss.
R= 8 x 108 cm
Show inner 1% in radius disk mass = .001 M_sun
Low viscosity a=.001
Disk Formation Movie
Accretion
Shock,
Disk formation
t = .75 s
neutrino
coolong
allows
accretion
no cooling=>
Photodisintegration
Si,O,C -> free neutrons
And protons
Enhanced neutrino
cooling
dynamically
unstable
CDAF?
Could emit
GWs but
maybe no
GRB
a = 0.1 <M> = 0.07 Msun /s = 1.3 x 1053 erg/s
spin
mass
Use 1D
neutrino
cooled
“slim” disk
models
from
Popham et
al (1999).
Collapsar results
•
•
•
•
•
•
Sustained accretion >10s
Sufficient energy
Time scale set by He core collapse
Disk-feeding time scale not disk-draining
Neutrino cooling allows accretion
Neutrino annihilation energetically possible
– calculable in any case
Funnel
geometry
channels any
fireball.
Density
contrasts can
be huge.
Thermal
energy
deposition
focused by
toroidal
funnel
structure
T = 5.7 ms
E = 5 x 1050 erg/s
Edep = 2.8 x 1048 erg
Jet Birth
.
.
Ejet = f Maccc2
MHD
nn
fmax ~ .06 - .4
Relativistic Jet Movie
Collapsar stages
1.
Iron core collapse, disk formation
T~1010K, ~108gcm-3, photodisintegration,
n cooling, pair capture, disk is free
nucleons (2 s)
2. Polar density declines to allow jet birth
½v3  Edep (2-5 s)
3. Jet tunnels out of star (5 s) Wolf-Rayet
4. Jet powered for ~10 more seconds.
Evacuates polar channel and reaches
asymptotic speed. (10 s)
T_GRB  T_collapse
Red Supergiant
Type Ib
or Ic
R~1013 cm
Supernova
Blue Supergiant
R~1012 cm
Wolf-Rayet Star
R~1011 cm
Supernovae
Type I
Type II
No Hydrogen
Hydrogen
Ia
Ib, Ic
WD cosmology
exploding WR
thermonuclear old
pop. E galaxies
core collapse
massive stars
“Nickel Wind”
Nickel Wind Movie
T > 5 x 109 K
Fallback in weak SN explosions
Shock
reaches
surface of
star but
parts of
star are not
ejected to
infinity.
Fallback accretion Mms ~ 25 Msun
Same star
exploded with a
range of
explosion
energies.
Significant
accretion for
thousands of
seconds – days.
If fallback fuels a
jet with power
fmc2
May power
“hypernova” or
long duration GRB
Weak
supernova
shock
Shock breakout X-Ray transient
What made SN1998bw+GRB980425?
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 G~3 shock breakout
(Tan et al 2001, Perna & Vietri 2002)
MacFadyen (1999)
Collapsars
• Can make “long” GRBs in H stripped (WR) stars.
tengine > tescape
• Short bursts may be compact binary mergers.
• Need SN failure & angular momentum
– Low metallicity, binary can help
• Star can explode -> SN if nickel is made.
Predicts 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
GRB/GW
• Long GRBs
– not brighter than SN in GW?
– very far Gpc
– very rare < 1% SN
• Short GBs
–
–
–
–
merging ns-bh binaries?
maybe closer than long bursts
short delay between event and GRB?
good for SWIFT/LIGO
Rates
•
•
•
•
•
•
•
SN: 1/s = 100,000 /day
GRB: 1/day (BATSE) = 1,000/day
GRB rate = 1% of SN rate
maybe more collapsars than GRBs
=> more rapidly rotating SN
SN with collapsar engine
look for bright Type Ic (w/ broad lines)
SN GW
•
•
•
•
•
SN1998bw/GRB980425
40 Mpc
maybe dominant GRB
rapid rotaters
SNAP/ROTSE look for 1998bw 2003dh
like SN
• many light curves -> better t_explode
Implications
•
•
•
•
Probe engine directly
collapse duration vs. GRB duration
collapse/GRB delay (internal vs. external?)
disk properties – low viscosity? big disks?
Issues
•
•
•
•
•
•
too much j => no GRB? but bright GW?
may need low metallicity for GRB
prefer high redshift
don’t know nearby rate
but 980425 may imply rate is high
look for weak GRBs like 980425
•
•
•
•
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
Black hole formation may be unavoidable for low metallicity
Solar
metallicity
Low
metallicity
With decreasing metallicity, the binding
energy of the core and the size of the
silicon core both increase, making
black hole formation more likely at
low metallicity.
Woosley, Heger, & Weaver, RMP, (2002)
The more difficult problem is the angular momentum. This
is a problem shared by all current GRB models that invoke
massive stars...
In the absence of mass loss
and magnetic fields, there would
be abundant progenitors.
Unfortunately nature has both.
15 solar mass helium core born rotating rigidly at f times break up