Book contents
- Frontmatter
- Contents
- Preface to the first edition
- Preface to the second edition
- Preface to the third edition
- 1 Background
- 2 Fourier transforms
- 3 Spectroscopic tools
- 4 Light detectors
- 5 Radiation terms and definitions
- 6 The black body and its radiation
- 7 Radiative and convective energy transport
- 8 The continuous absorption coefficient
- 9 The model photosphere
- 10 The measurement of stellar continua
- 11 The line absorption coefficient
- 12 The measurement of spectral lines
- 13 The behavior of spectral lines
- 14 The measurement of stellar radii and temperatures
- 15 The measurement of photospheric pressure
- 16 Chemical analysis
- 17 Velocity fields in stellar photospheres
- 18 Stellar rotation
- Appendix A A table of useful constants
- Appendix B Physical parameters of stars
- Appendix C A fast Fourier transform Fortran program
- Appendix D Atomic data
- Appendix E The strongest lines in the solar spectrum
- Appendix F Computation of random errors
- Index
- References
9 - The model photosphere
Published online by Cambridge University Press: 05 March 2015
- Frontmatter
- Contents
- Preface to the first edition
- Preface to the second edition
- Preface to the third edition
- 1 Background
- 2 Fourier transforms
- 3 Spectroscopic tools
- 4 Light detectors
- 5 Radiation terms and definitions
- 6 The black body and its radiation
- 7 Radiative and convective energy transport
- 8 The continuous absorption coefficient
- 9 The model photosphere
- 10 The measurement of stellar continua
- 11 The line absorption coefficient
- 12 The measurement of spectral lines
- 13 The behavior of spectral lines
- 14 The measurement of stellar radii and temperatures
- 15 The measurement of photospheric pressure
- 16 Chemical analysis
- 17 Velocity fields in stellar photospheres
- 18 Stellar rotation
- Appendix A A table of useful constants
- Appendix B Physical parameters of stars
- Appendix C A fast Fourier transform Fortran program
- Appendix D Atomic data
- Appendix E The strongest lines in the solar spectrum
- Appendix F Computation of random errors
- Index
- References
Summary
What is a model photosphere, and why build one? It would seem logical to take our stellar observations and deduce from them the physical conditions existing in the atmosphere of the star – somewhat like a parallax measurement yields the distance to a star. Alas, the formation of the stellar spectrum involves many physical variables, and a rigorous deductive interpretation cannot generally be made. Instead we hypothesize a model through which we organize and relate the information conveyed in the starlight. The model resembles a scientific theory in that it is constructed on the basis of our observations and known physical laws. We may then gather additional observations to test our model much like we would test a theory. The model is modified and improved as information is added. When our model closely reproduces all the available observations, we begin to feel that our model is worthy of some trust. Then properties associated with the model, or deduced from further application of the model, are associated with the star, properties such as effective temperature, surface gravity, radius, chemical composition, or rate of rotation.
The model photosphere consists of a table of numbers giving the source function and the pressure as a function of optical depth for an assumed chemical composition. Additional columns may be added to the table depending on the use intended for the model.
- Type
- Chapter
- Information
- The Observation and Analysis of Stellar Photospheres , pp. 170 - 203Publisher: Cambridge University PressPrint publication year: 2005