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The ‘Dark Side’ of Gamma-Ray Bursts and Implications for Nucleosynthesis

‘Dark Side’. The ‘Dark Side’ of Gamma-Ray Bursts and Implications for Nucleosynthesis. Susumu Inoue. in collaboration with. Nobuyuki Iwamoto (U. Tokyo) Manabu Orito (Tokyo Inst. Tech.) Mariko Terasawa (CNS). Nucleosynthesis in Baryon-Rich Outflows Associated with GRBs.

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The ‘Dark Side’ of Gamma-Ray Bursts and Implications for Nucleosynthesis

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  1. ‘Dark Side’ The ‘Dark Side’ of Gamma-Ray Burstsand Implications for Nucleosynthesis Susumu Inoue in collaboration with Nobuyuki Iwamoto (U. Tokyo) Manabu Orito (Tokyo Inst. Tech.) Mariko Terasawa (CNS) Nucleosynthesis in Baryon-RichOutflows Associated with GRBs ApJ (2003) 595, 294 neutron capture elements (‘n-process’) light elements (spallation?)

  2. entropy/baryon s/kb=4mpc2/3T0~1250T0/1MeV dimensionless entropy〜final Lorentz factor =L/Mc2 . baryon-rich outflow (BRO) ≪ → much more interesting! (n-capture elements, up to Pt, Au, U?) massive star core collapse, compact binary, etc… → E=Gc2 ultrarelativistic (>100) , baryon-poor (M<10-4M◎ ) outflow outflows in GRBs hot T0>~MeV, thick ~e≫1, n-rich initial conditions → expansion → nucleosynthesis? Meszaros ‘01 →limited nucleosynthesis(small amounts of D,4He) GRB jet  Lemoine 02, Pruet, et al 02, Beloborodov 03

  3. . L=Gc2 numerical simulations of jet propagation in collapsars Zhang, Woosley & Heger ‘03 significant energy in peripheral, low G outflow →X-ray flashes, statistics of afterglow light curve breaks evidence for the dark side of GRBs (baryon-rich outflows) generic initial conditions for central engine • optically thick ~e≫1 • high temperature T>~MeV • → expansion • high neutron fraction • in most models • Pruet, Woosley, Hoffman ‘02 → nucleosynthesis likely!

  4. . L=Gc2 observations! of low G outflow in GRB030329/SN2003dh Berger et al. ‘03, Nature, 426, 154 evidence for the dark side of GRBs (baryon-rich outflows) dominant energy in peripheral, low G (~a few) outflow →dark energy rules (at least in some GRBs) ! generic initial conditions for central engine • optically thick ~e≫1 • high temperature T>~MeV • → expansion • high neutron fraction • in most models • Pruet, Woosley, Hoffman ‘02 → nucleosynthesis likely!

  5. . L=Gc2 numerical simulations of jet propagation in collapsars Zhang, Woosley & Heger ‘03 evidence for the dark side of GRBs (baryon-rich outflows) example of failed GRB →GRB-less hypernovae? generic initial conditions for central engine • optically thick ~e≫1 • high temperature T>~MeV • → expansion • high neutron fraction • in most models • Pruet, Woosley, Hoffman ‘02 → nucleosynthesis likely!

  6. 6  4 parameters L=1052 erg/s luminosity r0=107 cm central engine radius =L/Mc2 dimensionless entropy Ye=(nn/np+1)-1 initial electron fraction =2 log  [g cm-3] 2 =10 0 . T -2 log T [MeV] -4 =102 -6 =103 -6 -5 -4 -3 -2 -1 log t’ [s] (comoving time) start from the simplest dynamical model: spherical, adiabatic, freely expanding thermally-driven steady flow fireball r &T profile(comoving frame trajectory) power-law exponential choose h2 (M~10-2M◎) relativistic limit, validity of fireball model

  7. 6  4 parameters L=1052 erg/s luminosity r0=107 cm central engine radius =L/Mc2 dimensionless entropy Ye=(nn/np+1)-1 initial electron fraction =2 log  [g cm-3] 2 =10 0 . T -2 log T [MeV] -4 =102 -6 =103 -6 -5 -4 -3 -2 -1 log t’ [s] (comoving time) nuclear reaction network >3000 n-rich species inclusion of light n-rich nuclei (Terasawa et al. ‘01) crucial for n-rich, rapid expansion start from the simplest dynamical model: spherical, adiabatic, freely expanding thermally-driven steady flow fireball r &T profile(comoving frame trajectory) power-law exponential choose h2 (M~10-2M◎) relativistic limit, validity of fireball model

  8. n n p He4 p T3 r D2 r T3 T9 T9 He3 D2 He3 B11 Li7 Be9 He4 Li7 B11 Be9 h=2, Ye=0.4 s/kb~2500, 0~2 105 g/cm3 s/kb~105,0~3 103 g/cm3 h=100, Ye=0.4 • reactions continue, t’>~100s, • A>16 and beyond • late D production by n decay → p(n,g)d • a lot more interesting! • some D, 4He production • freezeout t’>~1ms • not very exciting…

  9. s/kb~2000 0~2 105 g/cm3 . NS mergers? high M, low a disks? Ye=0.1,h=2 • near r-process (n-dripline) path • flow > 3rd peak → fission cycling? • abundance at peaks Y1<<Y2~Y3~10-6, neutrons remaining

  10. . low M, high a disks? Ye=0.4,h=2 • intermediate path > 2nd peak • small flow > 3rd peak • abundance at peaks Y1~10-7,Y2~10-6,Y3~10-8, neutrons remaining

  11. h=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. final heavy element abundances • production up to actinidesfor 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?

  12. 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=1010yr YGal=YF MF RF tGal/MGal ~10-13 ~ 10-2-10-1×solar pattern different from SN → contribution to some Galactic elements? GRB-BRO (h=2) peak abundance YF~10-6 ejected mass MF~10-2M◎ SN n-driven wind peak abundance YSNn~10-4 ejected mass MSNn~10-4M◎ heavy element abundances vs. observations comparable per event! kinetic energy EF =4 1052 erg

  13. metal poor stars? assume: fMPS=MF/Msh~10-7.51 eventdilution 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? GRB-BRO (h=2) peak abundance YF~10-6 ejected mass MF~10-2M◎ SN n-driven wind peak abundance YSNn~10-4 ejected mass MSNn~10-4M◎ heavy element abundances vs. observations comparable per event! kinetic energy EF =4 1052 erg

  14. BH BH binary companion surface c.f. GRO J1655-60 Israelian et al. (1999) companion assume: fbin=fcapMF/Mmix~10-3-10-1 binarydilution factor (Mmix=10-4-10-2M◎mass of mixing zone) Ybin=fbinYF~10-9-10-7≫ solar! (Y◎~10-11) sensitivity to Ye → probe of GRB central engine conditions? GRB-BRO (h=2) peak abundance YF~10-6 ejected mass MF~10-2M◎ SN n-driven wind peak abundance YSNn~10-4 ejected mass MSNn~10-4M◎ heavy element abundances vs. observations comparable per event! kinetic energy EF =4 1052 erg

  15. more realistic dynamical conditions, microphysics (→more nucleosynthesis? r-process pattern?) non-relativistic, collimation, … n-interactions, fission, p-rich heavy nuclei, , … next directions need good understanding of central engine… but we don’t BH accretion disk models? modeling of ‘wind’ difficult… Pruet, Woosley & Hoffman 03, Pruet, Surman & McLaughlin 03… interaction with external matter (spallation, external n-capture, etc)… e.g. p+CO->Li, Be, B after shock established: crude estimate MCO~10M◎ r~1010cm XL~nBROs(p+CO->L) rp(GeV) f ~10-7-10-6 CO C+O->L? forward shock CO contact discont. p Si, Fe layers? streaming neutrons?

  16. energetically important (often dominant) • interesting for nucleosynthesis Summary low G baryon-rich outflows (the dark side) of GRBs baryon-poor, ultrarelativistic outflows (successful GRBs): not much happens… baryon-rich, mildly relativistic outflows (circum-jet winds or failed GRBs) can: • 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? observational implications heavy n-capture elementspossibly observable in: Galactic abundances, metal poor stars BH binary companions→ probe of GRB central engine conditions? Something interesting may be going on in places not readily seen!

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