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Observing convection in stellar atmospheres

Published online by Cambridge University Press:  01 August 2006

John D. Landstreet
John D. Landstreet*
Affiliation:
Department of Physics & Astronomy, UWO, London, ON N6G 1P7, Canada email: [email protected]
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Abstract

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Convection occurs in the visible photospheric layers of most stars having Te less than about 10000 K, and in some hotter stars. The solar granulation pattern is a symptom of this, as is the non-zero microturbulent velocity often required in abundance analysis to make both weak and strong lines yield the same abundance.

In very sharp-lined stars, the presence of a non-thermal velocity field in the visible stellar atmosphere leads to several other effects which may be detected in spectral line profiles. These include radial velocities that vary systematically with equivalent width, distortions of the line profile as compared to a profile computed with a Voigt profile and rotational broadening (“macroturbulence”), and asymmetries with respect to the line centre (“bisector curvature”).

Detection and interpretation of these effects, with the goal of obtaining empirical information about a velocity field present in the visible layers, requires comparison with calculated synthetic spectra which incorporate model velocity fields. Thus, this review will summarize some of the observational clues concerning photospheric velocity fields, as well as modelling aimed at interpreting these data.

Keywords

ConvectionSun: atmospherestars: atmospheresline: profilesline: formation
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 2 , Symposium S239: Convection in Astrophysics , August 2006 , pp. 103 - 112
Copyright
Copyright © International Astronomical Union 2007

References

Allende Prieto, C., Asplund, M., García López, R. J. & Lambert, D. L. 2002, apj 567, 544CrossRefGoogle Scholar
Allende Prieto, C., Lambert, D. L., Tull, R. G. & MacQueen, P. J. 2002, apj 566, L93CrossRefGoogle Scholar
Allende Prieto, C., García López, R. J., Lambert, D. L. & Gustafsson, B. 1999, apj 526, 1000Google Scholar
Asplund, M. & García, Pérez 2001, aap 372, 601Google Scholar
Asplund, M., Nordlund, Å., Trampedach, R. & Stein, R. F. 1999, aap 346, L17Google Scholar
Dravins, D. 1987, aap 172, 211Google Scholar
Dravins, D. 1990, aap 228, 218Google Scholar
Dravins, D. 1999, in Hearnshaw, J.B. & Scarfe, C. D. (eds.), Precise Stellar Radial Velocities, ASP Conference Series, Vol. 185, p. 268Google Scholar
Dravins, D. & Nordlund, Å. 1990a, aap 228, 184Google Scholar
Dravins, D. & Nordlund, Å. 1990b, aap 228, 203Google Scholar
Fitzpatrick, E. L. & Massa, D. 1999, apj 525, 1011CrossRefGoogle Scholar
Freytag, B., Steffen, M. & Dorch, B. 2002, an 323, 213Google Scholar
Frutiger, C., Solanki, S. K., Fligge, M. & Bruls, J. H. M. J. 2000, aap 358, 1109Google Scholar
Frutiger, C., Solanki, S. K. & Mathys, G. 2005, aap 444, 549Google Scholar
Gardiner, R. B., Kupka, F. & Smalley, B. 1999, aap 347, 876Google Scholar
Gies, D. R. & Lambert, D. L. 1992, apj 387, 673CrossRefGoogle Scholar
Gray, D. F. 1982, apj 262, 682CrossRefGoogle Scholar
Gray, D. F. 1988, Lectures on Spectral-line Analysis: F, G and K Stars (Arva, ON, Canada: The Publisher)Google Scholar
Gray, D. F. 1989, pasp 101, 832Google Scholar
Gray, D. F. 2005, pasp 117, 711CrossRefGoogle Scholar
Gray, D. F. & Toner, C. G. 1986, pasp 98, 499CrossRefGoogle Scholar
Gray, D. F. & Nagel, T. 1989, apj 341, 421CrossRefGoogle Scholar
Hamilton, D. & Lester, J. B. 1999, pasp 111, 1132Google Scholar
Hill, G. M. 1995, aap 294, 536Google Scholar
Kupka, F. & Montgomery, M. H. 2002, mn 330, L6Google Scholar
Landstreet, J. D. 1998, aap 338, 1041Google Scholar
Lyubimkov, L. S., Rostopchin, S. I. & Lambert, D. L. 2004, mn 351, 745Google Scholar
Montalbán, J., D'Antona, F., Kupka, F. & Heiter, U. 2004, aap 416, 1081Google Scholar
Nave, G., Johanssen, S., Learner, R.C.M.Thorne, A. P. & Brault, J. W. 1994, apjs 94, 221CrossRefGoogle Scholar
Nordlund, Å., & Dravins, D. 1990, aap 228, 155Google Scholar
Schwarzschild, M. 1975, apj 195, 137Google Scholar
Smalley, B. & Kupka, F. 1997, aap 328, 349Google Scholar
Steffen, M., Freytag, B. & Ludwig, H.-G. 2005, in Favata, F. et al. (eds.), Proceedings 13th Cool Star Workshop, in pressGoogle Scholar
Stein, R. F. & Nordlund, Å. 1998, apj 499, 914Google Scholar
Struve, O. & Elvey, C. T. 1934, apj 79, 409Google Scholar
Varenne, O. & Monier, R. 1999, aap 351, 247Google Scholar