1994A&A...292..439P

We present spectroscopic observations of some 115 stars of the cluster Blanco 1, extending from the Ca II(H,K) region to the Ca II(I-R) triplet, supporting an age similar to that of the young cluster α Persei. The Hα absorption equivalent width vs (B-V) diagram forms a well-defined locus, with decreasing absorption equivalent width for decreasing effective temperature, akin to solar neighbourhood dwarfs. A large spread in the Ca II surface flux, as a function of (B-V), also indicates the presence of a high degree of surface inhomogeneity, synonymous with high magnetic activity in young stars. A drop-off in the Ca II flux at (B-V)=1.0 is also similar to the solar neighbourhood stars, and shows that the primary chromospheric cooling changes from the Ca II and Mg II lines to the Balmer lines. The mean chromospheric temperature for stars at 4800K lies between 8000K and 10000K, based on theoretical models, which is somewhat higher than the older solar neighbourhood dwarfs. The high mean Ca II surface flux of the sample is also consistent with that of other young clusters. We were able to measure the equivalent width of the Li(6708) line, whose strength as a function of (B-V) indicates an age similar to the young cluster α Persei. The lithium abundance decreases with decreasing effective temperature, consistent with the premise of lithium depletion in stars with larger convection zones. Using published photometry and a recent ZAMS fitting method, we also re-define the distance to the cluster to be 246pc.