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arXiv 0810.0031astro-ph
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Ia型超新星的母星年龄和金属丰度对光度和~(56)Ni产额的影响

The effect of progenitor age and metallicity on luminosity and 56Ni yield in Type Ia supernovae

D. A. Howell, M. Sullivan, E. F. Brown, A. Conley, D. Le Borgne, E. Y. Hsiao, P. Astier, D. Balam, C. Balland, S. Basa, R. G. Carlberg, D. Fouchez, J. Guy, D. H… 展开作者

D. A. Howell, M. Sullivan, E. F. Brown, A. Conley, D. Le Borgne, E. Y. Hsiao, P. Astier, D. Balam, C. Balland, S. Basa, R. G. Carlberg, D. Fouchez, J. Guy, D. Hardin, I. M. Hook, R. Pain, K. Perrett, C. J. Pritchet, N. Regnault, S. Baumont, J. Le Du, C. Lidman, S. Perlmutter, N. Suzuki, E. S. Walker, J. C. Wheeler

摘要:

Timmes、Brown和Truran发现,金属丰度的变化理论上可以解释Ia型超新星(SNe Ia)中合成的56 Ni质量的25%变化,因此可以解释观测到的SNe Ia光度的很大一部分散射。高金属量的母核更富含中子,相对于放射性56 Ni,产生更稳定的燃烧产物。我们开发了一种新的方法来估计在SNe Ia的热光度和56镍产量,并使用它来测试的理论与超新星遗产调查的数据。我们发现,Ia超新星的平均~(56)Ni产额确实在高金属丰度环境中下降,但理论只能解释~(56)Ni质量和光度弥散的7%-10%.这是因为该效应在金属丰度显著高于太阳能时占主导地位,而我们发现SN主机主要具有太阳能下或仅适度高于太阳能的金属丰度。我们还表明,允许在O/Fe与金属度[Fe/H]的变化不会有重大影响的理论预测的Timmes,布朗和Truran,只要一个是使用O/H作为自变量。年龄可能比金属丰度有更大的影响--我们发现宿主星系的光度加权年龄与56 Ni产量相关,因此更大质量的祖星会产生更明亮的爆炸。如果大部分的Ia超新星在其主恒星达到克拉塞卡质量时爆炸,这是很难理解的。最后,我们测试了Gallagher等人的发现,Ia超新星的残差与主星系的金属丰度相关,但我们没有发现这种相关性。

英文摘要:

Timmes, Brown & Truran found that metallicity variations could theoretically account for a 25% variation in the mass of 56Ni synthesized in Type Ia supernovae (SNe Ia), and thus account for a large fraction of the scatter in observed SN Ia luminosities. Higher-metallicity progenitors are more neutron-rich, producing more stable burning products relative to radioactive 56Ni. We develop a new method for estimating bolometric luminosity and 56Ni yield in SNe Ia and use it to test the theory with data from the Supernova Legacy Survey. We find that the average 56Ni yield does drop in SNe Ia from high metallicity environments, but the theory can only account for 7%--10% of the dispersion in SN Ia 56Ni mass, and thus luminosity. This is because the effect is dominant at metallicities significantly above solar, whereas we find that SN hosts have predominantly subsolar or only moderately above-solar metallicities. We also show that allowing for changes in O/Fe with the metallicity [Fe/H] does not have a major effect on the theoretical prediction of Timmes, Brown & Truran, so long as one is using the O/H as the independent variable. Age may have a greater effect than metallicity -- we find that the luminosity weighted age of the host galaxy is correlated with 56Ni yield, and thus more massive progenitors give rise to more luminous explosions. This is hard to understand if most SNe Ia explode when the primaries reach the Chandrasekhar mass. Finally, we test the findings of Gallagher et al., that the residuals of SNe Ia from the Hubble diagram are correlated with host galaxy metallicity, and we find no such correlation.

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