arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2103.02609astro-ph.SRastro-ph.GA
收藏

韦斯特伦德时代1重访

The Age of Westerlund 1 Revisited

Emma R. Beasor, Ben Davies, Nathan Smith, Robert D. Gehrz, Donald F. Figer

备注：
Accepted for publication in ApJ. 15 pages, 9 figures
阅读 PDF
arXiv 页面 ↗HTML 原文 ↗

摘要：

星团Westerlund~1（Wd 1）是一个拥有大量后主序星（MS）大质量恒星的星团。这些恒星的同时存在只能用恒星模型来解释，如果星团的年龄在400万年到500万年之间，有几项发表的研究独立地声称年龄在这个范围内。在这个年龄，恒星模型预测冷超巨星（CSG）的光度应该是$\log(L/L_\odot) \approx 5.5$，接近经验光度极限。在这里，我们使用SOFIA的档案数据和新的光度学来测试预测，以估计CSG的热光度。我们发现，无论使用哪种恒星演化模型，这些恒星的平均亮度为0.4 dex，太暗了，不可能有5 Myr的年龄，相反，这表明$10.4^{+1.3}_{-1.2}$ Myr的年龄要大得多。我们认为，无论是系统的不确定性的消光定律，恒星的变化，可以解释这种差异。在回顾文献中Wd 1的各种独立年龄估计时，我们首先指出，那些基于恒星多样性的估计是不可靠的。其次，我们重新分析Wd 1的前MS恒星采用Damineli消光定律，发现年龄为$7.2^{+1.1}_{-2.3}$百万年，比以前的研究，但这是容易受到系统误差，可能会推动年龄接近1000万年。然而，在CSG年龄和从食双星W13推断的年龄之间仍然存在着明显的矛盾。我们的结论是，恒星演化模型不能解释Wd 1下的单年龄范式。相反，我们认为Wd 1区域的恒星形成于几百万年的时间。

英文摘要：

The cluster Westerlund~1 (Wd1) is host to a large variety of post main-sequence (MS) massive stars. The simultaneous presence of these stars can only be explained by stellar models if the cluster has a finely-tuned age of 4-5Myr, with several published studies independently claiming ages within this range. At this age, stellar models predict that the cool supergiants (CSGs) should have luminosities of $\log(L/L_\odot) \approx 5.5$, close to the empirical luminosity limit. Here, we test that prediction using archival data and new photometry from SOFIA to estimate bolometric luminosities for the CSGs. We find that these stars are on average 0.4dex too faint to be 5Myr old, regardless of which stellar evolution model is used, and instead are indicative of a much older age of $10.4^{+1.3}_{-1.2}$Myr. We argue that neither systematic uncertainties in the extinction law nor stellar variability can explain this discrepancy. In reviewing various independent age estimates of Wd1 in the literature, we firstly show that those based on stellar diversity are unreliable. Secondly, we re-analyse Wd1's pre-MS stars employing the Damineli extinction law, finding an age of $7.2^{+1.1}_{-2.3}$Myr; older than that of previous studies, but which is vulnerable to systematic errors that could push the age close to 10Myr. However, there remains significant tension between the CSG age and that inferred from the eclipsing binary W13. We conclude that stellar evolution models cannot explain Wd1 under the single age paradigm. Instead, we propose that the stars in the Wd1 region formed over a period of several Myr.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

↑