High-resolution ( R = 143,000 ) , high signal-to-noise ( S/N = 700–1100 ) Gemini-S bHROS spectra have been analyzed in a search for ^ { 6 } Li in 5 stars which host extrasolar planets .
The presence of detectable amounts of ^ { 6 } Li in these mature , solar-type stars is a good monitor of accretion of planetary disk material , or solid bodies themselves , into the outer layers of the parent stars .
Detailed profile-fitting of the Li i resonance doublet at \lambda 6707.8 Å reveals no detectable amounts of ^ { 6 } Li in any star in our sample .
The list of stars analyzed includes HD 82943 for which ^ { 6 } Li has been previouly detected at the level of ^ { 6 } Li/ ^ { 7 } Li = 0.05 \pm 0.02 .
The typical limits in the derived isotopic fraction are ^ { 6 } Li/ ^ { 7 } Li \leq 0.00–0.02 .
These upper limits constrain the amount of accreted material to less than \sim 0.02 to 0.5 Jovian masses .
The presence of detectable amounts of ^ { 6 } Li would manifest itself as a red asymmetry in the Li i line-profile and the derived upper limits on such asymmetries are discussed in light of three-dimensional hydrodynamic model atmospheres , where convective motions also give rise to slight red asymmetries in line profiles .