We have measured stellar parameters , [ Fe/H ] , lithium abundances , rotation , and ^ { 12 } C/ ^ { 13 } C in a small sample of red giants in three open clusters that are each home to a red giant star that hosts a substellar companion ( NGC2423 3 , NGC4349 127 , and BD+12 1917 in M67 ) .
Our goal is to explore whether the presence of substellar companions influences the Li content .
Both ^ { 12 } C/ ^ { 13 } C and stellar rotation are measured as additional tracers of stellar mixing .
One of the companion hosts , NGC2423 3 , is found to be Li-rich with A ( Li ) _ { NLTE } = 1.56 dex , and this abundance is significantly higher than the A ( Li ) of the two comparison stars in NGC 2423 .
All three substellar companion hosts have the highest A ( Li ) and ^ { 12 } C/ ^ { 13 } C when compared to the control red giants in their respective clusters ; however , except for NGC2423 3 , at least one control star has similarly high abundances within the uncertainties .
Higher A ( Li ) could suggest that the formation or presence of planets plays a role in the degree of internal mixing on or before the red giant branch .
However , a multitude of factors affect A ( Li ) during the red giant phase , and when the abundances of our sample are compared to abundances of red giants in other open clusters available in the literature , we find that they all fall well within a much larger distribution of A ( Li ) and ^ { 12 } C/ ^ { 13 } C. Thus , even the high Li in NGC2423 3 can not be concretely tied to the presence of the substellar companion .