EMISSION-LINES IN THE LONG-PERIOD CEPHEID L-CARINAE

For the Cepheid l Carinae, with a pulsation period of 35.5 days, we ha ve studied the emission-line fluxes as a function of pulsational phase in order to find out whether we see chromospheric and transition-laye r emission or whether we see emission due to an outward-moving shock. All emission lines show a steep increase in flux shortly before maximu m light, suggestive of a shock moving through the surface layers. The large ratio of the C IV to C II line fluxes shows that these are not t ransition-layer lines. During maximum light the large ratio of the C I V to C II line fluxes also suggests that we see emission from a shock with velocities greater than 100 km s-1 such that C iv emission can be excited. With such velocities mass outflow appears possible. The vari ations seen in the Mg II line profiles show that there is an external absorption over a broad velocity band independent of the pulsational p hase. We attribute this absorption to a circumstellar ''shell.'' This ''shell'' appears to be seen also as spatially extended emission in th e O I line at 1300 angstrom, which is probably excited by resonance wi th Lybeta.