Physics
Scientific paper
Aug 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006iaujd...9e..32b&link_type=abstract
Supernovae: One Millennium After SN1006, 26th meeting of the IAU, Joint Discussion 9, 17-18 August 2006, Prague, Czech Republic,
Physics
Scientific paper
The r-process is one of the major nucleosynthesis processes responsible for the production of heavy elements beyond iron. Recent models of r-process nucleosynthesis rely on a neutrino-heated bubble developing at late times, which provides both the necessary conditions and the requisite amount of ejected mass for the r-process (Wooseley et al '94) . In the neutrino-driven explosion, only a small amount of matter is heated to the requisite high specific energy and entropy. Meyer et al (1992) first calculated the r-process under conditions appropriate to a neutrino-heated bubble and found that the solar r-process abundances could be replicated. They showed that the hot bubble that forms outside the protoneutron star during a SN explosion may be a viable site for the r-process as long as the entropy per baryon can be made sufficiently high. But in a very neutron rich environment such as a neutron star , the r-process could occur even at low entropy (Cowan and Thielemann, 2004). The high entropy wind is not the correct r-process site , owing to the inherent deficiencies in the abundance pattern below A=110 as well as the problems in obtaining the high entropies in SN II explosions required for producing the massive r-process nuclei up to A ≅ 195 and beyond ( Freiburghaus et al., 1999). Modelers of r-process nucleosynthesis find the entropy of the expanding matter and the overall n/p ratio to be more useful parameter than the temp and neutron density. We have tried to associate the explosion entropies with the site-independent classical approach (n[n] and T) and thereby compare the results of the two approaches from the abundances at different entropy conditions. We find that en entropy of ≈ 300 with Y[e] ≈ 0.45 can lead to a successful r-process. This is in agreement with the r-process abundance peaks at n[n] ≈ 10^32 cm^-3 and T[9] ≈ 1.5 . References : 1. Cowan J.J. and Thielemann F. K., Physics Today, 2004 2. Woosley S.E., Wilson J.R., Mathews G. J., Hoffman R.D. and Meyer B.S., 1994, ApJ, 433, 229 3. Takahashi K., Witti J. and Janka H.-Th., 1994, A & A , 286, 857 4. Meyer B. S., Mathews G. J., Howard W. M., Woosley S. E. and Hoffman R.D.,1992, ApJ, 399, 656 5. Freiburghaus C., Rembges J. F., Rauscher T.,Kolbe E., Thielemann F. K., kratz K. L., Pfeiffer B. and Cowan J. J., 1999, ApJ, 516, 381
Baruah Rulee
Duorah Hira Lal
Duorah Kalpana
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