The Second Annual Lowell Observatory Fall Workshop

Solar-Type Stars: Basic Information on Their Characterization and Classification
David R. Soderblom & Jeremy R. King (Space Telescope Science Institute)

9. Questions

Here we summarize questions raised that are relevant to the issue of solar twinness.

1. Are stellar classifications based on the appearance of the spectrum (spectral types) still a quantitative tool in a time when we have good parallaxes (luminosities) and can obtain excellent spectra easily?
2. Is there a spread in metallicity within clusters? Can this result from, e.g., late accretion of chondritic material?
3. Do stars have uniform composition within themselves?
4. How good are our models of stars? Are there important parameters we have failed to take into account?
5. What counts when we see differences between stars? For example, differences in activity may just reflect different current states within identical long-term behavior. Current differences in lithium abundance may be a manifestation of past differences in angular momentum but may not imply any real difference in the present structure or evolutionary state.
6. Can rotation alter the macro-state of a star?
7. What constitutes "twinness''? What are the properties that must agree for us to judge two stars to be twins so that we can go on to study other properties and their consequences?

Twins can have different states within a common envelope.

Acknowledgments

We wish to thank the following for contributing materials shown here and for ongoing collaborations: Burt Jones (Lick Obs.); John Stauffer (CfA); D. Latham et al. (CfA); Todd Henry, Lionel Siess (STScI); S. Baliunas, R. Donahue (CfA); F. Benedict (U. Texas); O. Franz (Lowell Obs.); M. Pinsonneault, D. Terndrup (Ohio State); and finally G. Cayrel de Strobel, for inspiring us to get together. We also thank Larry Petro for his careful reading of the manuscript.

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