Lithium abundances of the cool metal-poor dwarfs HD 103095, HD 134439, and HD 134440

We present high-resolution, high-S/N spectra in the lambda 6707 Li I region of the cool metal-poor dwarfs HD 103095 ( = HR 4550 = Gmb 1830), I-ID 134439, and HD 134440. Previous detections of weak Li in the first two stars are confirmed. We suggest that neither standard nor rotational stellar models we consider are able to satisfactorily account for the Li depletion of HD 103095. In contrast, both standard and rotational models are able to account for the Li abundance of HD 134439. This apparent disparity reappears when we find that the metallicity sensitivity of the Li depletion models cannot be confirmed by our, or previously published Li abundances of HD 103095 and HD 134439. HD 134439 and 134440 form a common proper-motion pair with virtually identical kinematics and heavy element abundances. Thus, it is likely that the Li abundances of these two field stars can be compared without undue concern for differences in their ages, compositions, or any Li enrichment history. Moreover, we do not find any significant Na abundance differences, hinted at by previous work, which would cloud the interpretation of the proper motion pair Li abundances, The greater than or equal to 0.6 dex Li abundance difference between HD 134439 and the similar to 200 K cooler HD 134440 implies that the Li-T-eff morphology is a sharp function of temperature below T-eff similar to 5000 K. This rather precipitous decline in Li abundance is consistent both with the standard and rotational stellar models considered here.