Volume 543, July 2012
|Number of page(s)||10|
|Section||Stellar structure and evolution|
|Published online||11 July 2012|
The birth rate of supernovae from double-degenerate and core-degenerate systems
School of Physics and Chemistry, Henan Polytechnic University,
2 Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, 650011 Kunming, PR China
3 Department of Astronomy, Beijing Normal University, 100875 Beijing, PR China
Received: 12 January 2012
Accepted: 10 May 2012
Context. Some recent observations of the delay-time distribution (DTD) of Type Ia supernovae (SNe Ia) seem to uphold the double-degenerate (DD) scenario as the progenitor model of SNe Ia, but the core-degenerate (CD) scenario remains a strong competitor to the DD one.
Aims. We investigate the effects of metallicity and the different treatments of common envelope (CE) on the DTD of SNe Ia by considering the DD and CD scenarios, and check the suggestion that the total mass of DD system is the main dependent variable of Phillips relation.
Methods. We perform a series of Monte Carlo simulations based on a rapid binary evolution code and consider two treatments of CE evolution, i.e. α-formalism and γ-algorithm.
Results. We find that only when the α-formalism is considered with a high CE ejection efficiency, may the shape of the DTD for DD systems be consistent with that derived observationally, i.e. a power law of ~t-1, while the value of the birth rate of SNe Ia marginally matches observations. For the α-formalism with a low CE ejection efficiency and the γ-algorithm, neither the shape of the DTD nor the value of the birth rate can be compared with those of the observations. Metallicity may not have a significant influence on the shape of DTD, but a lower metallicity may lead to a slightly higher birth rate of SNe Ia by a factor of 2, especially for SNe Ia with long delay times. If the results for the single-degenerate (SD) channel are incorporated into those for the DTD, both the shape of DTD and its value may be closely consistent with observations for SNe Ia younger than 2.5 Gyr, and SD and DD channels provide comparable contributions to the total SNe Ia, while for SNe Ia with delay times longer than 2.5 Gyr, DD is the dominant channel and the birth rate is lower than that derived from observations by a factor up to about four. In addition, we calculate the evolutions of various integral parameters of DD systems, and do not find any one suitable to explain the correlation between the brightness of SNe Ia and its delay time. Moreover, there are three channels producing CD systems that may contribute a few SNe Ia, but the contribution of CD systems to the total SNe Ia is no more than 1%.
Conclusions. There may be other channels or mechanisms contributing to SNe Ia with long delay times.
Key words: white dwarfs / supernovae: general / binaries: general / stars: evolution
© ESO, 2012
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