Emission Lines in the Long-Period Cepheid L Carinae
Abstract
For the Cepheid l Carinae, with a pulsation period of 35.5 days, we have studied the emission-line fluxes as a function of pulsational phase in order to find out whether we see chromospheric and transition-layer emission due to an outward-moving shock. All emission lines show a steep increase in flux shortly before maximum light, suggestive of a shock moving through the surface layers. The large ratio of C IV to C II line fluxes shows that these are not transition-layer lines. During maximum light the large ratio of the large ratio of the C IV to C II line fluxes also suggests that we see emission from a shock with velocities greater than 100 km/s such that C IV emission can be excited. With such velocities mass outflow appears possible. The variations seen in the MG II line profiles show that there is an external absorption over a broad velocity band independent of the pulsation phase. We attribute this absorption to a circumstellar 'shell.' This 'shell' appears to be seen also as spatially extended emission in the O I line at 1300 A, which is probably excited by resonance with Ly beta.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- January 1994
- DOI:
- 10.1086/173570
- Bibcode:
- 1994ApJ...420..401B
- Keywords:
-
- Carbon;
- Cepheid Variables;
- Emission Spectra;
- Periodic Variations;
- Shock Waves;
- Stellar Envelopes;
- Magnesium;
- Oxygen;
- Spectrum Analysis;
- Ultraviolet Astronomy;
- Astrophysics;
- SHOCK WAVES;
- STARS: INDIVIDUAL CONSTELLATION NAME: L CARINAE;
- STARS: VARIABLES: CEPHEIDS;
- ULTRAVIOLET: STARS