We investigate the -process nucleosynthesis during the magnetohydrodynamical (MHD) explosion of a supernova in a helium star of 3.3？ , where effects of neutrinos are taken into account using the leakage scheme in the two-dimensional (2D) hydrodynamic code. Jet-like explosion due to the combined effects of differential rotation and magnetic field is able to erode the lower electron fraction matter from the inner layers. We find that the ejected material of low electron fraction responsible for the -process comes out from just outside the neutrino sphere deep inside the Fe-core. It is found that heavy element nucleosynthesis depends on the initial conditions of rotational and magnetic fields. In particular, the third peak of the distribution is significantly overproduced relative to the solar system abundances, which would indicate a possible -process site owing to MHD jets in supernovae. 1. Introduction Study of the -process has been developed considerably keeping pace with the terrestrial experiments of nuclear physics far from the stability line of nuclides [1]. In particular, among the three peaks, which correspond to the elements of , , and , in the abundance pattern for the solar system -elements, the transition from the second to third peak elements has been stressed by nuclear physicists [2]. Although supernovae could be one of the astrophysical sites of the -process [2, 3], explosion mechanism is not still completely resolved, where supernova explosions are originated from the gravitational collapse of massive stars of ？ [4, 5]. However it is unclear whether neutron-rich elements could be ejected or not during the shock wave propagation. As far as the one-dimensional calculations, almost all realistic numerical simulations concerning the collapse-driven supernovae of ？ have failed to explode the outer layer above the Fe-core due to drooping of the energetic shock wave propagation [6, 7]. Although there exist calculations for 8 and 11？ stars to explode, the explosion energies are very weak [8–15]. Therefore, a plausible site/mechanism of the -process has not yet been clarified. On the other hand, models of magnetorotational explosion (MRE) for core-collapse supernovae have been presented as a supernova mechanism [16–19] since both rapid rotations and/or strong magnetic fields could be resulted for neutron stars after the explosions. Furthermore, MRE with a realistic magnetic field configuration has been investigated [20–22]. In their series of papers, it has been shown that magnetorotational instability plays a critical role concerning the
References
[1]
M. Arnould, S. Goriely, and K. Takahashi, “The r-process of stellar nucleosynthesis: astrophysics and nuclear physics achievements and mysteries,” Physics Reports, vol. 450, no. 4-6, pp. 97–213, 2007.
[2]
F. K. Thielemann, A. Arcones, R. K？ppeli et al., “What are the astrophysical sites for the r-process and the production of heavy elements?” Progress in Particle and Nuclear Physics, vol. 66, no. 2, pp. 346–353, 2011.
[3]
Y. Z. Qian, “The r-process: current understanding and future tests,” in Proceedings of the 1st Argonne/MSU/JINA/INT RIA Wokshop, 2005.
[4]
M. Hashimoto, “Supernova nucleosynthesis in massive stars,” Progress of Theoretical Physics, vol. 94, no. 5, pp. 663–736, 1995.
[5]
A. Heger, C. L. Fryer, S. E. Woosley, N. Langer, and D. D. H. Hartmann, “How massive single stars end their life,” Astrophysical Journal Letters, vol. 591, no. 1, pp. 288–300, 2003.
[6]
H. T. Janka, R. Buras, K. Kifonidis, A. Marek, and M. Rampp, “Core-collapse supernovae at the threshold,” Springer Proceeding in Physics, vol. 99, pp. 253–262, 2005.
[7]
K. Sumiyoshi, S. Yamada, H. Suzuki, H. Shen, S. Chiba, and H. Toki, “Postbounce evolution of core-collapse supernovae: long-term effects of the equation of state,” Astrophysical Journal Letters, vol. 629, no. 2, pp. 922–932, 2005.
[8]
A. Burrows, E. Livne, L. Dessart, C. D. Ott, and J. Murphy, “A new mechanism for core-collapse supernova explosions,” Astrophysical Journal Letters, vol. 640, no. 2, pp. 878–890, 2006.
[9]
F. S. Kitaura, H. T. Janka, and W. Hillebrandt, “Explosions of O-Ne-Mg cores, the Crab supernova and subluminous type II-P supernovae,” Astronomy and Astrophysics, vol. 450, no. 1, pp. 345–350, 2006.
[10]
A. Burrows, L. Dessart, E. Livne, C. D. Ott, and J. Murphy, “Simulations of magnetically driven supernova and hypernova explosions in the context of rapid rotation,” The Astrophysical Journal, vol. 664, no. 1, p. 416, 2007.
[11]
S. W. Bruenn, A. Mezzacappa, W. R. Hix et al., “The explosion of a rotating star as a supernova mechanism,” in American Institute of Physics Conference Series, G. Giobbi, A. Tornambe, G. Raimondo et al., Eds., vol. 1111, pp. 593–601, 2009.
[12]
A. Marek and H. T. Janka, “Delayed neutrino-driven supernova explosions aided by the standing accretion-shock instability,” Astrophysical Journal Letters, vol. 694, no. 1, pp. 664–696, 2009.
[13]
Y. Suwa, K. Kotake, T. Takiwaki, S. C. Whitehouse, M. Liebend？rfer, and K. Sato, “Explosion geometry of a rotating 13m⊙ star driven by the sasi-aided neutrino-heating supernova mechanism,” Publications of the Astronomical Society of Japan, vol. 62, no. 6, pp. L49–L53, 2010.
[14]
T. Fischer, S. C. Whitehouse, A. Mezzacappa, F. K. Thielemann, and M. Liebend？rfer, “Protoneutron star evolution and the neutrino-driven wind in general relativistic neutrino radiation hydrodynamics simulations,” Astronomy & Astrophysics, vol. 517, article A80, 25 pages, 2010.
[15]
T. Takiwaki, K. Kotake, and Y. Suwa, “Three-dimensional hydrodynamic core-collapse supernova simulations for an 11.2 star with spectral neutrino transport,” Astronomical Journal, vol. 738, no. 2, article 165, 13 pages.
[16]
G. S. Bisnovaty-Kogan, “Mechanism of core-collapse supernovae & simulation results from the CHIMERA code,” Astronomicheskii Zhurnal, vol. 47, p. 813, 1970.
[17]
N. V. Ardeljan, G. S. Bisnovatyi-Kogan, and S. G. Moiseenko, “Explosion mechanisms of supernovae: the magnetorotational model,” Physics-Uspekhi, vol. 40, pp. 1076–1079, 1997.
[18]
N. V. Ardeljan, G. S. Bisnovatyi-Kogan, and S. G. Moiseenko, “Magnetorotational mechanism: 2D simulation,” in The Local Bubble and Beyond Lyman-Spitzer-Colloquium: Proceedings of the IAU Colloquium No. 166, vol. 506 of Lecture Notes in Physics, pp. 145–148, 1998.
[19]
G. S. Bisnovatyi-Kogan, N. V. Ardeljan, and S. G. Moiseenko, “Magnetorotational explosions: supernovae and jet formation,” Memorie della Societa Astronomica Italiana, vol. 73, pp. 1134–1143, 2002.
[20]
N. V. Ardeljan, G. S. Bisnovatyi-Kogan, and S. G. Moiseenko, “Magnetorotational supernovae,” Monthly Notices of the Royal Astronomical Society, vol. 359, no. 1, pp. 333–344, 2005.
[21]
S. G. Moiseenko, G. S. Bisnovatyi-Kogan, and N. V. Ardeljan, “A magnetorotational core-collapse model with jets,” Monthly Notices of the Royal Astronomical Society, vol. 370, no. 1, pp. 501–512, 2006.
[22]
G. S. Bisnovatyi-Kogan, S. G. Moiseenko, and N. V. Ardeljan, “Different magneto-rotational supernovae,” Astronomy Reports, vol. 12, no. 12, pp. 997–1008, 2008.
[23]
K. Kotake, H. Sawai, S. Yamada, and K. Sato, “Magnetorotational effects on anisotropic neutrino emission and convection in core-collapse supernovae,” Astrophysical Journal Letters, vol. 608, no. 1, pp. 391–404, 2004.
[24]
K. Kotake, S. Yamada, K. Sato, K. Sumiyoshi, H. Ono, and H. Suzuki, “Gravitational radiation from rotational core collapse: effects of magnetic fields and realistic equations of state,” Physical Review D, vol. 69, no. 12, Article ID 124004, 2004.
[25]
S. Yamada and H. Sawai, “Numerical study on the rotational collapse of strongly magnetized cores of massive stars,” Astrophysical Journal Letters, vol. 608, no. 2, pp. 907–924, 2004.
[26]
S. Yamada, K. Kotake, and T. Yamasaki, “The role of neutrinos, rotations and magnetic .elds in collapse-driven supernovae,” New Journal of Physics, vol. 6, article 79, pp. 1–24, 2004.
[27]
T. Takiwaki, K. Kotake, S. Nagataki, and K. Sato, “Magneto-driven shock waves in core-collapse supernovae,” Astrophysical Journal Letters, vol. 616, no. 2, pp. 1086–1094, 2004.
[28]
J. M. Stone and M. L. Norman, “ZEUS-2D: a radiation magnetohydrodynamics code for astrophysical flows in two space dimensions. II: the magnetohydrodynamic algorithms and tests,” Astrophysical Journal Supplement, vol. 80, p. 791, 1992.
[29]
H. Shen, H. Toki, K. Oyamatsu, and K. Sumiyoshi, “Relativistic equation of state of nuclear matter for supernova and neutron star,” Nuclear Physics A, vol. 637, no. 3, pp. 435–450, 1998.
[30]
S. Nishimura, K. Kotake, M. A. Hashimoto et al., “r-process nucleosynthesis in magnetohydrodynamic jet explosions of core-collapse supernovae,” Astrophysical Journal Letters, vol. 642, no. 1, pp. 410–419, 2006.
[31]
M. Liebend？rfer, A. Mezzacappa, F. K. Thielemann, B. Messer, W. R. Hix, and S. Bruenn, “Probing the gravitational well: no supernova explosion in spherical symmetry with general relativistic Boltzmann neutrino transport,” Physical Review D, vol. 63, no. 10, Article ID 103004, 13 pages, 2001.
[32]
C. Winteler, R. K？ppeli, A. Perego et al., “Magnetorotationally driven supernovae as the origin of early galaxy r-process elements?” Astrophysical Journal Letters, vol. 750, no. 1, article L22, 2012.
[33]
M. Saruwatari, M. Hashimoto, K. Kotake, and S. Yamada, “R-process nucleosynthesis during the magnetohydrodynamics explosions of a massive star,” in Proceedings of the 10th Internal Symposium on Origin of Matter and Evolution of Galaxies (OMEG '10), vol. 1269 of AIP Conference Proceedings, pp. 409–411, Osaka, Japan, March, 2010.
[34]
K. Mori, E. Gotthelf, S. Zhang et al., “NuSTAR discovery of A 3.76 s transient magnetar near sagittarius A,” The Astrophysical Journal, vol. 770, no. 2, article L23.
[35]
R. Epstein, “The generation of gravitational radiation by escaping supernova neutrinos,” The Astrophysical Journal, vol. 223, pp. 1037–1042, 1978.
[36]
M. Ruffert, H. T. Janka, and G. Schafer, “Coalescing neutron stars—a step towards physical models I. Hydrodynamical evolution and gravitational-wave emission,” Astronomy & Astrophysics, vol. 311, pp. 532–566, 1996.
[37]
A. Staudt and H. V. Klapdor-Kleingrothaus, “Calculation of beta-delayed fission rates of neutron rich nuslei far off stability,” Nuclear Physics A, vol. 549, no. 2, pp. 254–264, 1992.
[38]
K. A. van Riper and J. M. Lattimer, “Stellar core collapse. I: infall epoch,” The Astrophysical Journal, vol. 249, pp. 270–289, 1981.
[39]
K. Kotake, S. Yamada, and K. Sato, “Anisotropic neutrino radiation in rotational core collapse,” Astrophysical Journal Letters, vol. 595, no. 1, pp. 304–316, 2003.
[40]
S. Rosswog and M. Liebend？rfer, “High-resolution calculations of merging neutron stars. II: neutrino emission,” Monthly Notices of the Royal Astronomical Society, vol. 342, no. 3, pp. 673–689.
[41]
K. A. van Riper, “Stellar core collapse. II: inner core bounce and shock propagation,” The Astrophysical Journal, vol. 257, no. 15, pp. 793–820, 1982.
[42]
H. A. Bethe, “Supernova mechanisms,” Reviews of Modern Physics, vol. 62, no. 4, pp. 801–866, 1990.
[43]
H. T. Janka, “Conditions for shock revival by neutrino heating in core-collapse supernovae,” Astronomy and Astrophysics, vol. 368, no. 2, pp. 527–560, 2001.
[44]
D. L. Tubbs and D. N. Schramm, “Neutrino opacities at high temperatures and densities,” The Astrophysical Journal, vol. 201, pp. 467–488, 1975.
[45]
R. I. Epstein and C. J. Pethick, “Lepton loss and entropy generation in stellar collapse,” The Astrophysical Journal, vol. 243, pp. 1003–1012, 1981.
[46]
G. M. Fuller, W. A. Fowler, and M. J. Newmann, “Stellar weak interaction rates for intermediate-mass nuclei. II: A = 21 to A = 60,” The Astrophysical Journal, vol. 252, pp. 715–740, 1982.
[47]
K. Langanke, G. Martínez-Pinedo, J. M. Sampaio et al., “Electron capture rates on nuclei and implications for stellar core collapse,” Physical Review Letters, vol. 90, no. 24, Article ID 241102, pp. 1–4, 2003.
[48]
S. L. Shapiro and S. A. Teukolsky, Black Holes, White Dwarfs, and Neutron Stars, Wiley, 1983.
[49]
S. A. Bludman, I. Lichtenstadt, and G. Hayden, “Homologous collapse and deleptonization of an evolved stellar core,” The Astrophysical Journal, vol. 261, pp. 661–676, 1982.
[50]
J. Cooperstein, “Neutrinos in supernovae,” Physics Reports, vol. 163, no. 1-3, pp. 95–126, 1988.
[51]
A. Heger, S. E. Woosley, and H. C. Spruit, “Presupernova evolution of differentially rotating massive stars including magnetic fields,” Astrophysical Journal, vol. 626, no. 1, pp. 350–363, 2005.
[52]
D. D. Clayton, Principles of Stellar Evolution and Nucleosynthesis, McGraw-Hill, New York, NY, USA, 1968.
[53]
W. A. Fowler and F. Hoyle, “Neutrino processes and pair formation in massive stars and supernovae,” Astrophysical Journal Supplement, vol. 9, p. 201, 1964.
[54]
L. F. Roberts, S. Reddy, and G. Shen, “Medium modification of the charged-current neutrino opacity and its implications,” Physical Review C, vol. 86, no. 6, Article ID 065803, 10 pages, 2012.
[55]
G. Martinez-Pinedo, T. Fischer, A. Lohs, and L. Huther, “Charged-current weak interaction processes in hot and dense matter and its impact on the spectra of neutrinos emitted from proto-neutron star cooling,” Physical Review Letters, vol. 109, no. 25, Article ID 251104, 2012.
[56]
M. Liebend？rfer, S. C. Whitehouse, and T. Fischer, “The isotropic diffusion source approximation for supernova neutrino transport,” Astrophysical Journal Letters, vol. 698, no. 2, pp. 1174–1190, 2009.
[57]
M. Ono, M. A. Hashimoto, S. I. Fujimoto, K. Kotake, and S. Yamada, “Explosive nucleosynthesis in magnetohydrodynamical jets from collapsars,” Progress of Theoretical Physics, vol. 122, no. 3, pp. 755–777, 2009.
[58]
H. T. Janka and E. Müller, “Neutrino heating, convection, and the mechanism of Type-II supernova explosions,” Astronomy & Astrophysics, vol. 306, p. 167, 1996.
[59]
Y. Suwa, K. Kotake, T. Takiwaki, M. Liebendorfer, and K. Sato, “Impacts of collective neutrino oscillations on supernova explosions,” Astronomical Journal, vol. 749, no. 2, article 98, 17 pages.
[60]
S. I. Fujimoto, K. Kotake, M. A. Hashimoto, M. Ono, and N. Ohnishi, “Explosive nucleosynthesis in the neutrino-driven aspherical supernova explosion of a non-rotating 15 M∞ star with solar metallicity,” Astrophysical Journal, vol. 738, no. 1, article 61, 2011.
[61]
S. I. Fujimoto, K. Kotake, S. Yamada, M. A. Hashimoto, and K. Sato, “Magnetohydrodynamic simulations of a rotating massive star collapsing to a black hole,” Astrophysical Journal Letters, vol. 644, no. 2, pp. 1040–1055, 2006.
[62]
M. Ono, S. Nagataki, H. Ito et al., “Matter mixing in aspherical core-collapse supernovae: a search for possible conditions for conveying 56Ni into high velocity regions,” The Astrophysical Journal, vol. 773, no. 2, article 161, 2013.
[63]
V. V. Usov, “Millisecond pulsars with extremely strong magnetic fields as a cosmological source of γ-ray bursts,” Nature, vol. 357, pp. 472–474, 1992.
[64]
C. Thompson, “A model of gamma-ray bursts,” Monthly Notices of the Royal Astronomical Society, vol. 270, no. 3, p. 480, 1994.
[65]
E. G. Blackman and I. Yi, “On fueling gamma-ray bursts and their afterglows with pulsars,” Astrophysical Journal Letters, vol. 498, no. 1, pp. L31–L35, 1998.
[66]
J. C. Wheeler, I. Yi, P. H？flich, and L. Wang, “Asymmetric supernovae, pulsars, magnetars, and gamma-ray bursts,” The Astrophysica l Journal, vol. 537, no. 2, pp. 810–823, 2000.
[67]
B. Zhang and P. Meszaros, “Gamma-ray burst afterglow with continuous energy injection: signature of a highly magnetized millisecond pulsar,” The Astrophysical Journal Letters, vol. 552, no. 1, article L35, 2001.
[68]
T. A. Thompson, P. Chang, and E. Quataert, “Magnetar spin-down, hyperenergetic supernovae, and gamma-ray bursts,” Astrophysical Journal Letters, vol. 611, no. 1, pp. 380–393, 2004.
[69]
N. Bucciantini, E. Quataert, J. Arons, B. D. Metzger, and T. A. Thompson, “Magnetar-driven bubbles and the origin of collimated outflows in gamma-ray bursts,” Monthly Notices of the Royal Astronomical Society, vol. 380, no. 4, pp. 1541–1553, 2007.
[70]
N. Bucciantini, E. Quataert, J. Arons, B. D. Metzger, and T. A. Thompson, “Relativistic jets and long-duration gamma-ray bursts from the birth of magnetars,” Monthly Notices of the Royal Astronomical Society, vol. 383, no. 1, pp. L25–L29, 2008.
[71]
N. Bucciantini, E. Quataert, B. D. Metzger, T. A. Thompson, J. Arons, and L. Del Zanna, “Magnetized relativistic jets and long-duration GRBs from magnetar spin-down during core-collapse supernovae,” Monthly Notices of the Royal Astronomical Society, vol. 396, no. 4, pp. 2038–2050, 2009.
[72]
B. D. Metzger, T. A. Thompson, and E. Quataert, “Proto-neutron star winds with magnetic fields and rotation,” Astrophysical Journal Letters, vol. 659, no. 1, pp. 561–579, 2007.
