Si II equivalent widths in SMC A-type supergiants.

Four B9-Ao supergiants in the SMC (MD 7583, 5030, 5277, R27) have Si ii (6347, 6371 A) equivalent widths which are about a factor 2 smaller than expected from the Rosendhal equivalent width-absolute magnitude relation. Either the Rosendhal relation breaks down or silicon is underabundant in these stars (despite the fact that Wolf derives a normal silicon abundance from these lines in HD 7583).