SIMBAD references

The extinction curves observed in four environments: 1) The diffuse galactic interstellar medium, 2) the denser medium in the Orion nebula, 3) lines of sights with R(V) intermediate between those of 1) and 2), and 4) the region of S Doradus in the LMC, have been examined with MRN-type (Mathis et al. 1977) models, to explore the ranges of the parameters of the best-fit solutions allowed by the observational errors in the extinction curves. It was found the the permitted ranges of the parameters are rather wide. In particular the mass ratio of graphite/silicate locked in dust spans over an order of magnitude both in the diffuse galactic medium and in S Doradus. In the first case the interval is between 0.8 to 9 and in the second case is between 4 to 12.