标题： 低温恒星和太阳光谱中的Si II紫外发射线 显示英文标题

标题： Ultraviolet emission lines of Si II in cool star and solar spectra

摘要： 利用近期针对Si II的原子物理计算，在Cloudy建模代码中分析了哈勃太空望远镜（HST）空间观测天文台（STIS）获取的三颗凉星（双子座β星、半人马座α A和B）的紫外线光谱，以及之前发表的哈勃太空望远镜/高分辨光谱仪（GHRS）对御夫座α星的观测数据，还有来自高分辨率望远镜和光谱仪的太阳宁静区数据。 之前在理论上和观测值之间发现的涉及 Si II 的 2335 Å 谱线强度比的 3s$^{2}$3p $^{2}$P$_{J}$--3s3p$^{2}$ $^{4}$ P$_{J^{\prime}}$杂项跃迁的差异显著减小，同样减小的还有包含 1816 Å 处 3s$^{2}$3p $^{2}$P$_{J}$--3s3p$^{2}$$^{2}$D$_{J^{\prime}}$跃迁的强度比的差异。 这主要是由于新Si II跃迁概率的影响。 然而，这些原子数据不仅与先前的计算非常不同，而且与测量值也存在很大的分歧，特别是与Calamai等人（1993年）对于交错线的测量值存在较大差异。 因此，迫切需要新的Si II跃迁概率测量来确认（或否定）最近计算值的准确性。 如果新计算得到证实，那么长期以来理论与观测之间的差异将最终得以解决。 然而，如果旧的测量被发现是正确的，那么理论与观测之间的一致性只是巧合，现有的差异仍然存在。 显示英文摘要

摘要： Recent atomic physics calculations for Si II are employed within the Cloudy modelling code to analyse Hubble Space Telescope (HST) STIS ultraviolet spectra of three cool stars, Beta-Geminorum, Alpha-Centauri A and B, as well as previously published HST/GHRS observations of Alpha-Tau, plus solar quiet Sun data from the High Resolution Telescope and Spectrograph. Discrepancies found previously between theory and observation for line intensity ratios involving the 3s$^{2}$3p $^{2}$P$_{J}$--3s3p$^{2}$ $^{4}$P$_{J^{\prime}}$ intercombination multiplet of Si II at 2335 Angs are significantly reduced, as are those for ratios containing the 3s$^{2}$3p $^{2}$P$_{J}$--3s3p$^{2}$ $^{2}$D$_{J^{\prime}}$ transitions at 1816 Angs. This is primarily due to the effect of the new Si II transition probabilities. However, these atomic data are not only very different from previous calculations, but also show large disagreements with measurements, specifically those of Calamai et. al. (1993) for the intercombination lines. New measurements of transition probabilities for Si II are hence urgently required to confirm (or otherwise) the accuracy of the recently calculated values. If the new calculations are confirmed, then a long-standing discrepancy between theory and observation will have finally been resolved. However, if the older measurements are found to be correct, then the agreement between theory and observation is simply a coincidence and the existing discrepancies remain.