Dawe, John Alan;
(1967)
The atmosphere of late type stars.
Doctoral thesis (Ph.D), University of London.
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Abstract
The theoretical basis for the computation of model stellar atmospheres is reviewed and criticized. A programme for the automatic computation of late type stellar atmospheres is presented, whereby allowance is made for the transport of energy by convection and the effect of line blanketing and blocking, when evaluating the temperature distribution. This programme has been used to obtain a series of static models, representing the Cepheid variable Aquilae at various phases during its period. It is shown that, by means of a suitable transformation of the variation of effective gravity with time, it is possible to obtain a dynamical representation of the motion of the atmosphere. As observation suggests, the photosphere and the surface of lineformation are found to move in unison. The energy of pulsation of the outer layers has been evaluated, and is shown to be insufficient to remove material from the star. However, Jacobsen's observation (1956) of a bright emission component of the K line of Ca II, appearing at 0.85 with an apparent accel- p oration of 1U-0 cm/sec and disappearing with a velocity close to the escape velocity of the star, suggests that If there is mass loss, the energy must be provided by the variation of surface flux with time. A definitive radial velocity curve has been obtained for the Cepheid variable 1 Carinae, and a Wesselink analysis yields a mean radius of R = (152.9 - 1.1 J x lO^cms. The velocity curve defined by the absorption core of the K line is found to have a similar shape to the corresponding curve of £ Aquilae, but to be in phase with the mean velocity curve for the iron lines. An emission component is observed between 0.78 and 1.06.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | The atmosphere of late type stars |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| UCL classification: | UCL > Provost and Vice Provost Offices UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10212778 |
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