Are 44 Ti-producing supernovae exceptional?
Are 44 Ti-producing supernovae exceptional?
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DOI：
10.1051/0004-6361:20054626
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发表时间：
2006-01
影响因子：
6.5
通讯作者：
L. The;D. Clayton;R. Diehl;D. Hartmann;A. Iyudin;M. Leising;B. Meyer;Y. Motizuki;V. Schonfelder-V.-Sch
中科院分区：
文献类型：
--
作者：
L. The;D. Clayton;R. Diehl;D. Hartmann;A. Iyudin;M. Leising;B. Meyer;Y. Motizuki;V. Schonfelder-V.-Sch
根据标准模型，超新星会产生放射性的14ti，在经过几个世纪的衰变后，在伽马射线中应该可以看到14ca。钛的产生被认为是宇宙中Ca的来源，其丰度已得到证实。然而，伽玛射线望远镜并没有看到预期的核心坍缩事件的年轻残余物。89 y的44 Ti平均寿命和3/100 y的银河超新星速率意味着几个可探测的44 Ti伽玛射线源，但只有一个是清晰可见的，即340岁的Cas A信噪比。此外，产生大量44钛的超新星预计主要发生在银河系的内部，那里年轻的大质量恒星最为丰富。因为银河系对伽马射线是透明的，这应该是预期的伽马射线源的主要位置。然而，casa信噪比是唯一一个远离内星系（经度112）的源。我们评估了过去三个世纪以来令人惊讶的没有可探测到的超新星。我们讨论了我们对SN爆炸的理解，它们的44 Ti产量，它们的空间分布和统计参数是否可以扩展，以便这种明显的分歧可以容纳在合理的预期范围内，或者我们是否必须修改上述部分或全部方面以使预期与观测结果一致。我们的结论是，在过去的几个世纪里，要么核心坍缩超新星在银河系中罕见得令人难以置信，要么44颗产生钛的超新星是非典型超新星。我们还提出了一个基于主流SiC星尘颗粒中44 Ca/ 40 Ca比率的新论点，这可能会对大质量氦帽型I型超新星作为大多数星系44 Ca的来源产生怀疑。
According to standard models supernovae produce radioactive 44 Ti, which should be visible in gamma-rays follow- ing decay to 44 Ca for a few centuries. 44 Ti production is believed to be the source of cosmic 44 Ca, whose abundance is well established. Yet, gamma-ray telescopes have not seen the expected young remnants of core collapse events. The 44 Ti mean life of ' 89 y and the Galactic supernova rate of' 3/100 y imply' several detectable 44 Ti gamma-ray sources, but only one is clearly seen, the 340-year-old Cas A SNR. Furthermore, supernovae which produce much 44 Ti are expected to occur primarily in the inner part of the Galaxy, where young massive stars are most abundant. Because the Galaxy is transparent to gamma-rays, this should be the dominant location of expected gamma-ray sources. Yet the Cas A SNR as the only one source is located far from the inner Galaxy (at longitude 112 ). We evaluate the surprising absence of detectable supernovae from the past three centuries. We discuss whether our understanding of SN explosions, their 44 Ti yields, their spatial distributions, and statistical arguments can be stretched so that this apparent disagreement may be accommodated within reasonable expectations, or if we have to revise some or all of the above aspects to bring expectations in agreement with the observations. We conclude that either core collapse supernovae have been improbably rare in the Galaxy during the past few centuries, or 44 Ti -producing supernovae are atypical supernovae. We also present a new argument based on 44 Ca/ 40 Ca ratios in mainstream SiC stardust grains that may cast doubt on massive-He-cap Type I supernovae as the source of most galactic 44 Ca.