Emission Lines of the Long Period Copheid L Carinae
Abstract
We propose to observe the time dependence of the ultraviolet emission line fluxes in the Cepheid l Carinae. Previous observations by Schmidt and Parsons have shown that l Carinae appears to be the only Cepheid observed so far to show the high ionization lines up to C IV. This Cepheid therefore appears to be the best star to study the rise and decay of emission lines of different stages of ionization. During the phases of increasing emission we should be able to see the phase delay for the emission of high ionization line, as compared to low ionization lines, corresponding to the increasing amount of heating and the propagation of the ionization front through the surface layers when the transition region is built up. The amount of heating measures the amount of energy being deposited. If the emission is related to the onset of convection during the cool phases of the pulsation, as seems to be the case. then the rise and decay of the ultraviolet emission lines will be able to teach us a lot about the timescales for the generation of the mechanical flux heating the chromosphere and transition laver. This in turn will tell us something about the nature of this flux and about the time dependence of the developing convection.
- Publication:
-
IUE Proposal
- Pub Date:
- 1988
- Bibcode:
- 1988iue..prop.3051B