K-BAND SPECTROSCOPY OF BE-STAR X-RAY BINARIES

We present the first 2.0-2.5 mum spectra of four Be/X-ray binaries, at a resolution of lambda/DELTAlambda = 310-400. The spectra show strong hydrogen recombination lines, notably Brgamma and, in most cases, the higher order Pfund series. The relative recombination strengths imply that Brgamma has a large optical depth, whereas the Pfund lines have relative strengths close to case B and so may be optically thin. The H e I 2.06-mum line is also in emission. Mg II emission lines are presen t, as are Na I lines; the latter are normally associated with emission -zone temperatures that are cooler than the conventional Be-star circu mstellar disc. We conclude that optical effects are evident in H I lin e emission.