Probing the structure of a birthplace of intermediate-mass stars: Ammonia cores in Lynds 1340

We present an analysis of our high-resolution spectroscopic and high-precision UBV(RI)c photometric observations of a sample of 110 nearby late-F and G-type stars selected for their large rotational velocity. The relationships between Li abundance, X-ray luminosity, and v sin i are investigated. We find that, as expected, the stars in our sample show statistically higher Li abundance and activity level than field star samples with similar characteristics, but slower rotation. Surprisingly, however, we also find four rapidly-rotating single main-sequence stars with very low Li abundance. For both single and binary stars we find a large spread of Li abundance for stars with rotation lower than about 18 km s^-1. The well-established correlation between X-ray luminosity and rotation rate is clearly observed. All single unevolved solar type stars with v sin i larger than 18 km s^-1are strong X-ray emitters and have high Li abundance. Finally, we find also five evolved stars with very low Li abundance that are still rather fast rotators. The results from our sample confirm the presence of young very active stars close to the Sun, in agreement with recent findings from EUV and X-ray surveys, although our sample does not show such extreme characteristics as those selected from EUV and X-ray surveys at the current flux limits.