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arXiv 0906.2284astro-ph.SR
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Ib、Ic、SNe和GRB型的不同祖细胞

The different progenitors of type Ib, Ic SNe, and of GRB

Cyril Georgy, Georges Meynet, Rolf Walder, Doris Folini, André Maeder

摘要:

我们讨论的祖先的核心坍缩SNe的属性,因为它们可以推导出旋转恒星模型的单星。SN前体的类型由SN前阶段的表面丰度确定。SN事件的类型是从核心坍缩SN事件时喷出的氢和氦的质量获得的。我们发现,核心坍缩SN(无论何种类型)喷出的氦的最小量约为0.3 MSun。WC星和WO星在氦、CNO元素和重元素的喷射质量上没有差别。同样,正常演化或均匀演化所产生的WC星的化学成分之间预计也没有差异。Ib型SNe的祖先是WNL、WNE或质量较小的WC星。Ic型的是WC和WO星。WO星是在一个有限的质量范围内(大约60 MSun)产生的,并且只有在低金属丰度(<= 0.010)时才产生。WO星只是一小部分Ic型的祖先。目前的恒星模型表明,在太阳金属丰度下,大约有1个Ib型SN对应1个Ic型SN,在太阳金属丰度为2倍时,这一比例上升到3个Ic型SN对应1个Ib型SN。在这种金属丰度下,Ic型比Ib型更常见,因为大多数经历WNE阶段的大质量恒星会进一步演化为WC/WO阶段。目前的模型可以解释观测到的SN Ib/SN II和SN Ic/SN II的数量比,以及它们随金属丰度的变化。如果在黑洞形成时没有超新星发生,单星模型仍然可以解释超过一半的观测到的(SN Ib+SN Ic)/SN II比率,Z >= ZSun。对于GRB速率,我们的模型产生了太大的数字,这样的事件,即使我们限制的祖WO星。

英文摘要:

We discuss the properties of the progenitors of core collapse SNe, as they can be deduced from rotating stellar models of single stars. The type of the SN progenitor was determined from the surface abundances at the pre-SN stage. The type of the SN event was obtained from the masses of hydrogen and helium ejected at the time of the core-collapse SN event. We find that the minimum amount of helium ejected by a core-collapse SN (of whatever type) is around 0.3 MSun. There is no difference between the WC and WO stars in the ejected masses of helium, CNO elements, and heavy elements. Also no difference is expected between the chemical composition of a WC star resulting from a normal or a homogeneous evolution. The progenitors of type Ib SNe are WNL, WNE, or less massive WC stars. Those of type Ic are WC and WO stars. WO stars are produced in a limited mass range (around 60 MSun) and only at low metallicity (for <= 0.010) as already found. The WO stars are the progenitors of only a small fraction of type Ic. Present stellar models indicate that, at solar metallicity, there is about 1 type Ib SN for 1 type Ic, and this ratio rises to 3 type Ic for 1 type Ib SN at twice solar metallicity. At this metallicity, type Ic's are more frequent than type Ib's because most massive stars that go through a WNE stage evolve further into a WC/WO phase. Current models can account for the observed number ratios SN Ib/SN II and SN Ic/SN II and for their observed variation with the metallicity. In case no supernova occurs when a black hole is formed, single-star models can still account for more than half of the observed (SN Ib+SN Ic)/SN II ratio for Z >= ZSun. For the GRB rate, our models produce too large a number for such an event, even if we restrict the progenitor to the WO stars.

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