SIMBAD references

We present new determinations of the blue to red supergiant ratio (B/R) in young open clusters at various metallicities. For this purpose, we examine the HR diagrams of 45 clusters in the Galaxy and of 4 clusters in the Magellanic Clouds. The identification of supergiants is based on spectroscopic measurements (with photometric counts to check the results). The new counts confirm the increase of the B/R ratio when the metallicity increases with the following normalized relation: (B/R)/((B/R)_☉)≃0.05.e^3(Z)/(Z☉_)^, where Z_☉=0.02 and (B/R)_☉ is the value of B/R at Z_☉ which depends on the definition of B and R and on the age interval considered (e.g. for spectroscopic counts including clusters with logage between 6.8 and 7.5, (B/R)_☉≃3 when B includes O, B and A supergiants).