‘Dark Side’ The ‘Dark Side’ of Gamma-Ray Bursts and Implications for Nucleosynthesis neutron...
-
Upload
ashlyn-carson -
Category
Documents
-
view
223 -
download
0
Transcript of ‘Dark Side’ The ‘Dark Side’ of Gamma-Ray Bursts and Implications for Nucleosynthesis neutron...
The ‘Dark Side’‘Dark Side’ of Gamma-Ray Burstsand Implications for Nucleosynthesis
neutron capture elements (‘n-process’)light elements (spallation?)
ApJ (2003) 595, 294
Susumu Inoue
Nucleosynthesis in Baryon-RichOutflows Associated with GRBs
in collaboration with
Nobuyuki Iwamoto (U. Tokyo)Manabu Orito (Tokyo Inst. Tech.)Mariko Terasawa (CNS)
‘‘Dark Side’Dark Side’
outflows in GRBs
ultrarelativistic (>100) , baryon-poor (M<10-4M◎ ) outflow E=c2
Meszaros ‘01
massive star core collapse, compact binary, etc… →
hot T0>~MeV, thick ~e≫1,n-rich initial conditions→ expansion→ nucleosynthesis?
GRB jet → limited nucleosynthesis (small amounts of D,4He)Lemoine 02, Pruet, et al 02, Beloborodov 03
entropy/baryon s/kb=4mpc2/3T0~1250T0/1MeV
dimensionless entropy 〜 final Lorentz factor=L/Mc2
.
baryon-rich outflow(BRO)
≪ → much more interesting! (n-capture elements, up to Pt, Au, U?)
evidence for the dark sidedark side of GRBs (baryon-rich outflows)numerical simulations of jet propagation in collapsars Zhang, Woosley & Heger ‘03
significant energy in peripheral, low outflow → X-ray flashes, statistics of afterglow light curve breaks
evidence for the dark sidedark side of GRBs (baryon-rich outflows)observations! of low outflow in GRB030329/SN2003dh Berger et al. ‘03, Nature, 426, 154
dominant energy in peripheral, low (~a few) outflow → dark energy rules (at least in some GRBs) !
evidence for the dark sidedark side of GRBs (baryon-rich outflows)numerical simulations of jet propagation in collapsars Zhang, Woosley & Heger ‘03
example of failed GRB → GRB-less hypernovae?
parametersL=1052 erg/s luminosityr0=107 cm central engine radius
=L/Mc2 dimensionless entropyYe=(nn/np+1)-1
initial electron fraction
.
log t’ [s] (comoving time)
log
T [M
eV]
=2
=102
=10
=103
T
0
2
4
6
-2
-4
-6
-6 -5 -4 -3 -2 -1
log
[g
cm
-3]
fireball &T profile(comoving frame trajectory)
exponential
power-law
start from the simplest dynamical model:spherical, adiabatic, freely expandingthermally-driven steady flow
choose 2 (M~10-2M◎)relativistic limit,validity of fireball model
parametersL=1052 erg/s luminosityr0=107 cm central engine radius
=L/Mc2 dimensionless entropyYe=(nn/np+1)-1
initial electron fraction
.
log t’ [s] (comoving time)
log
T [M
eV]
=2
=102
=10
=103
T
0
2
4
6
-2
-4
-6
-6 -5 -4 -3 -2 -1
log
[g
cm
-3]
fireball &T profile(comoving frame trajectory)
exponential
power-law
start from the simplest dynamical model:spherical, adiabatic, freely expandingthermally-driven steady flow
choose 2 (M~10-2M◎)relativistic limit,validity of fireball modelnuclear reaction network
>3000 n-rich speciesinclusion of light n-rich nuclei(Terasawa et al. ‘01)crucial for n-rich, rapid expansion
=100, Ye=0.4
T9
D2
He4
np
B11Be9
T3
He3
Li7
s/kb~105, 0~ 3 103 g/cm3
• some D, 4He production• freezeout t’>~1ms not very exciting…
D2
He4
n
p
B11
Be9
T3
He3
Li7
• reactions continue, t’>~100s, A>16 and beyond• late D production by n decay → p(n,)d a lot more interesting!
=2, Ye=0.4 s/kb~2500, 0~ 2 105 g/cm3
Ye=0.1, =2
• near r-process (n-dripline) path• flow > 3rd peak → fission cycling?• abundance at peaks Y1<<Y2~Y3~10-6, neutrons remaining
s/kb~20000~ 2 105 g/cm3
NS mergers? high M, low disks?.
Ye=0.4, =2
• intermediate path > 2nd peak• small flow > 3rd peak• abundance at peaks Y1~10-7,Y2~10-6,Y3~10-8, neutrons remaining
low M, high disks?.
final heavy element abundances =2, Ye=0.1-0.498
----- Ye=0.1----- Ye=0.3----- Ye=0.4----- Ye=0.48----- Ye=0.498
----- solar total arbitrary norm.
• production up to actinides for Ye<~0.4 → fission cycling?• peaks intermediate between r & s (n-process)• abundances at peaks Yp~10-6 for Ye<~0.4; small flow to high A for Ye~0.5• neutrons always remaining → external n-capture process?
heavy element abundances vs. observations
GRB-BRO (=2)peak abundance YF~10-
6
ejected mass MF~10-2
M◎
SN -driven windpeak abundance YSN~10-
4
ejected mass MSN~10-4M◎
Galactic abundances?assume:event rate RF~10-4-10-3/yr/gal ~1-10 RGRB(f=10-3) ~0.01-0.1 RSN
MGal=1011M◎, tGal=1010yrYGal=YF MF RF tGal/MGal
~10-13 ~ 10-2-10-1×solarpattern different from SN → contribution to some Galactic elements?
comparableper event!
kinetic energy EF =4 1052 erg
heavy element abundances vs. observations
GRB-BRO (=2)peak abundance YF~10-
6
ejected mass MF~10-2
M◎
SN -driven windpeak abundance YSN~10-
4
ejected mass MSN~10-4M◎
metal poor stars?assume:fMPS=MF/Msh~10-7.5 1 event dilution factor(Msh=3 105M◎ mass of mixing shell)YMPS=fMPSYF~10-13.5 ~ 10-2.5×solar
association with most massive stars → prominent contribution at low Fe/H?
comparableper event!
kinetic energy EF =4 1052 erg
assume:fbin=fcapMF/Mmix~10-3-10-1
binary dilution factor(Mmix=10-4-10-2M◎ mass of mixing zone)
BH binary companion surface
Ybin=fbinYF~10-9-10-7≫ solar! (Y◎~10-11) sensitivity to Ye → probe of GRB central engine conditions?
c.f. GRO J1655-60Israelian et al. (1999)
BH
companion
heavy element abundances vs. observations
GRB-BRO (=2)peak abundance YF~10-
6
ejected mass MF~10-2
M◎
SN -driven windpeak abundance YSN~10-
4
ejected mass MSN~10-4M◎
comparableper event!
kinetic energy EF =4 1052 erg
next directions
need good understanding of central engine… but we don’t
more realistic dynamical conditions, microphysics(→ more nucleosynthesis? r-process pattern?) non-relativistic, collimation, … -interactions, fission, p-rich heavy nuclei, , …
Pruet, Woosley & Hoffman 03, Pruet, Surman & McLaughlin 03…
BH accretion disk models? modeling of ‘wind’ difficult…
interaction with external matter (spallation, external n-capture, etc)…
crude estimateMCO~10M◎ r~1010cmXL~nBRO (p+CO->L) rp(GeV) f~10-7-10-6
CO
e.g. p+CO->Li, Be, B
contact discont.forward shock
p
CO
C+O->L?
Si, Fe layers?streaming neutrons?
after shock established:
Summary low baryon-rich outflows (the dark side) of GRBs
• synthesize heavy n-capture elements up to the actinides induce ‘n-process’ (intermediate between r & s)• synthesize some light elements D, Li, Be, B much more by spallation?
baryon-poor, ultrarelativistic outflows (successful GRBs): not much happens…
heavy n-capture elements possibly observable in:Galactic abundances, metal poor starsBH binary companions → probe of GRB central engine conditions?
baryon-rich, mildly relativistic outflows (circum-jet winds or failed GRBs) can:
observational implications
Something interesting may be going on in places not readily seen!
• energetically important (often dominant)• interesting for nucleosynthesis