We measured ³⁵Cl abundances in 52 M giants with metallicities in the range −0.5 < [Fe/H] < 0.12. Abundances and atmospheric parameters were derived using infrared spectra from CSHELL on the NASA Infrared Telescope Facility and from optical echelle spectra. We measured Cl abundances by fitting a H³⁵Cl molecular feature at 3.6985 μm with synthetic spectra. We also measured the abundances of O, Ca, Ti, and Fe using atomic absorption lines. We find that the [Cl/Fe] ratio for our stars agrees with chemical evolution models of Cl, and the [Cl/Ca] ratio is broadly consistent with the solar ratio over our metallicity range. Both indicate that Cl is primarily made in core-collapse supernovae with some contributions from Type Ia supernovae. We suggest that other potential nucleosynthesis processes, such as the ν-process, are not significant producers of Cl. Finally, we also find our Cl abundances are consistent with H ii and planetary nebular abundances at a given oxygen abundance, although there is scatter in the data.

我们测量了52 M巨型金属中的³⁵ Cl丰度，其金属度在-0.5 <[Fe / H] <0.12范围内。使用NASA红外望远镜设施上的CSHELL的红外光谱和光学echelle光谱得出丰度和大气参数。我们测量氯丰度通过拟合ħ ³⁵在3.6985氯分子特征μm具有合成光谱。我们还使用原子吸收线测量了O，Ca，Ti和Fe的丰度。我们发现，我们恒星的[Cl / Fe]比与Cl的化学演化模型一致，并且[Cl / Ca]比在我们的金属度范围内与日照比大致一致。两者都表明Cl主要是由核塌陷超新星产生的，而Ia型超新星也有贡献。我们认为，其他潜在的核合成过程，如ν进程外，都没有氯的显著生产者。最后，我们发现在给定的氧丰度下，我们的Cl丰度与H ii和行星状星云状的丰度一致，尽管数据中存在分散。