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| Paper: |
Simulations of White Dwarf Mergers |
| Volume: |
469, 18th European White Dwarf Workshop (EUROWD12) |
| Page: |
137 |
| Authors: |
Staff, J.; Menon, A.; Herwig, F.; Clayton, G. C.; Even, W. P.; Fryer, C. L.; Motl, P.; Tohline, J. E.; Geballe, T.; Pignatari, M. |
| Abstract: |
R Coronae Borealis (RCB) stars may be the result of the merger of a CO and a
He WD. We have performed six 3 dimensional hydrodynamic simulations of the
merger of two WDs, keeping a total mass of 0.9 solar masses and varying the
mass ratio (q) between 0.5 and 1. The simulations show that for high
q, the two cores merge leading to a combined core consisting of material
from both the former accretor and donor. For lower q, the donor star gets
tidally disrupted and most of the donor material ends up outside the
accretor core, with a hot interaction layer forming between them. A lower q leads
to higher temperatures. We locate conditions that are suitable for
nucleosynthesis to take place, especially looking for conditions favorable
for creating 18O, since the 16O to
18O ratio in RCB stars is
observed to be unusually low, of order unity. Using conditions found in
the hydrodynamic simulations as input to our post-processing nucleosynthesis
code, we find that oxygen ratios down to 4 can be reached, but only after a
hundred years, assuming the conditions will remain constant for that long.
The main problem preventing the oxygen ratio to drop lower is that much
16O
is dredged up from the accretor in the merger process, thereby necessitating
production of large amount of 18O in order to achieve ratios of order
unity. |
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