Dearborn D S, Schramm D N
Lawrence Livermore National Laboratory, University of California, L-58, P.O. Box 808, Livermore, CA 94550, USA.
Proc Natl Acad Sci U S A. 1997 May 13;94(10):4836-41. doi: 10.1073/pnas.94.10.4836.
Observers have found a small number of lithium-depleted halo stars in the temperature range of the Spite plateau. The current status of the mass-loss hypothesis for producing the observed lithium dip in Population (Pop) I stars is briefly discussed and extended to Pop II stars as a possible explanation for these halo objects. Based on detections of F-type main-sequence variables, mass loss is assumed to occur in a narrow temperature region corresponding to this "instability strip." As Pop II main-sequence stars evolve to the blue, they enter this narrow temperature region, then move back through the lower temperature area of the Spite plateau. If 0.05 M. (solar mass) or more have been lost, they will show lithium depletion. This hypothesis affects the lithium-to- beryllium abundance, the ratio of high- to low-lithium stars, and the luminosity function. Constraints on the mass-loss hypothesis due to these effects are discussed. Finally, mass loss in this temperature range would operate in stars near the turnoff of metal-poor globular clusters, resulting in apparent ages 2 to 3 Gyr (gigayears) older than they actually are.
观测者在斯皮泰高原温度范围内发现了少量锂元素耗尽的晕星。本文简要讨论了造成第一星族（Pop）恒星中观测到的锂元素下降的质量损失假说的现状，并将其扩展到第二星族恒星，作为这些晕星的一种可能解释。基于对F型主序星变星的探测，假定质量损失发生在对应于这个“不稳定带”的狭窄温度区域。当第二星族主序星向蓝色演化时，它们进入这个狭窄温度区域，然后再回到斯皮泰高原的较低温度区域。如果已经损失了0.05 M⊙（太阳质量）或更多质量，它们就会显示出锂元素耗尽。这一假说影响锂与铍的丰度、高锂与低锂恒星的比例以及光度函数。本文讨论了由于这些效应而对质量损失假说产生的限制。最后，在这个温度范围内的质量损失会在贫金属球状星团的拐点附近的恒星中起作用，导致其表观年龄比实际年龄大2至3吉年（千兆年）。
