发表机构
Pontificia Universidad Católica de Chile; University of Amsterdam; Universidad Adolfo Ibáñez（智利天主教 Pontificia 大学; 阿姆斯特丹大学; 阿道夫·伊巴涅斯大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
通过多历元视向速度监测锂丰富巨行星样本，未发现其密近双星比例高于锂正常群体，从而约束了双星相互作用假说。
AI 中文摘要
通常考虑解释低质量红巨星具有异常高锂（Li）丰度的一个可能场景需要与密近双星伴星的相互作用。如果这一增丰通道占主导，则预测锂丰富巨行星中的双星比例相对于锂正常巨行星显著增强。我们旨在通过使用多历元视向速度（RVs）测量一个统计上稳健的锂丰富巨行星样本的密近双星比例，来约束双星相互作用假说。我们正在巡天红团簇（RC）和首次上升红巨星（RGB）目标，这使我们能够检查双星比例随演化阶段变化的潜在差异。我们正在使用VLT上的ESPRESSO监测70个目标（40个RC和30个RGB，全部为锂丰富），其中57个（32个RC+25个RGB）在约7个月的时间基线内已有4次或更多次访问；本文的分析基于后者。对于视向速度变化大于预期固有抖动（jitter）的目标，我们使用蒙特卡洛分析来估计观测到的视向速度变化是由恒星（$P_{SB}$）或亚恒星（$P_{SS}$）伴星引起的概率。排除38个与恒星抖动一致的目标后，我们剩下11个RC和8个RGB恒星（分别占各自子样本的34%和32%），其视向速度变化与存在轨道周期短于3000天的密近伴星一致。在这19个中，3个可确认为恒星质量伴星。$P_{SB}$和$P_{SS}$的分布在RC和RGB样本之间在统计上无法区分。因此，我们目前的数据中尚未发现锂丰富巨行星（无论处于哪个演化阶段）的双星比例大于锂正常群体预期的证据。延长视向速度基线以探测更长轨道周期将对继续探索这一场景的合理性至关重要。
英文摘要
One of the possible scenarios usually considered to explain the existence of low-mass red giants with anomalously high lithium (Li) abundances requires the interaction with a close binary companion. If dominant, this enrichment channel predicts a significantly enhanced binary fraction among Li-rich giants relative to Li-normal ones. We aim to constrain the binary interaction hypothesis by using multi-epoch radial velocities (RVs) to measure the close binary fraction of a statistically robust sample of Li-rich giants. We are surveying both red clump (RC) and first ascent red giant (RGB) targets, which allows us to examine potential differences in the binary fraction as a function of evolutionary stage. We are monitoring 70 targets (40 RC and 30 RGB, all Li-rich) using ESPRESSO at the VLT, 57 of which (32 RC + 25 RGB) already have 4 or more visits over a $\sim$7 month baseline; the analysis in this paper is based on the latter. For the targets with RV variation larger than that expected for intrinsic jitter, we use a Monte Carlo analysis to estimate the probability that the observed RV variation is due to a stellar ($P_{SB}$) or sub-stellar ($P_{SS}$) companion. Discounting the 38 targets consistent with stellar jitter, we are left with 11 RC and 8 RGB stars (34% and 32% of the respective sub-samples) with RV variability consistent with the presence of a close companion with an orbital period shorter than 3000 days. Of these 19, 3 can be confirmed as stellar-mass companions. The distributions of $P_{SB}$ and $P_{SS}$ are statistically indistinguishable between the RC and RGB samples. We thus find no evidence so far in our current data for a binary fraction for Li-rich giants (in either evolutionary stage) larger than that expected for a Li-normal population. Extending the RV baseline to probe longer orbital periods will be important to keep exploring the plausibility of this scenario.
Comments10 pages, 6 figures. Re-submitted to A&A following referee's comments. Comments welcome
