Hostname: page-component-76fb5796d-22dnz Total loading time: 0 Render date: 2024-04-26T21:14:42.524Z Has data issue: false hasContentIssue false
  • English
  • Français

The Role of Technetium in the Evolution of Red Giants

Published online by Cambridge University Press:  12 April 2016

Irene R. Little-Marenin
Irene R. Little-Marenin*
Affiliation:
Wellesley College, Wellesley, MA, USA 02181

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Tc is detected in many AGB stars providing unambiguous proof that recent nuclear s-processing and mixing (the third dredge-up) has taken place. During this evolutionary episode the atmospheres of AGB stars are progressively enhanced with helium burning products (primari ly l2C) and s-process elements as they evolve from M->MS->S->SC->C stars. The increase in s-process elements can be traced most easily by the presence and increasing strength of the Tc I lines accompanying this progression. We also find that the third dredge-up phase is accompanied by an increase in the amplitude of light variation since no non-variable or low amplitude variable M, MS, SC, or S (with one exception) have Tc lines. M star Mira variables show Tc if P > 300d (low mass Pop I stars). No Pop II star is known to have Tc. Nor do supergiants show Tc I lines. The significant fraction of MS, S and C stars that do not show Tc, are surmised to be cooler analogues to the Ba II stars, i.e. binaries. The source to provide the neutrons for the s-process is most likely the 13C(a, n)16O reaction since most of the stars in which we observe Tc are thought to have masses less than 3 solar masses.

Type
2. Model Photospheres and Chemical Compositions
Information
International Astronomical Union Colloquium , Volume 106: Evolution of Peculiar Red Giant Stars , 1989 , pp. 131 - 143
Copyright
Copyright © Cambridge University Press 1989

References

Ake, T.B and Johnson, H.R. 1988, Ap.J., 327, 224.Google Scholar
Beer, H., and Walter, G. 1985, in Cool Stars with Excesses in Heavy Elements, eds Jaschek, M. and Keenan, P.C., (Reidel: Dordrecht), p. 373.Google Scholar
Boesgaard, A.M. 1970, Ap.J., 161, 163.Google Scholar
Bohm-Vitense, E. 1980, Ap.J. (Letters), 239, L79.Google Scholar
Bohm-Vitense, E. and Johnson, H.R. 1985, Ap.J., 293, 288.Google Scholar
Bohm-Vitense, E., Nemec, J., and Proffitt, C. 1984, Ap.J., 278, 726.Google Scholar
Boothroyd, A.I., and Sackmann, I.-J., 1988a, Ap.J., 328, 653.Google Scholar
Boothroyd, A.I., and Sackmann, I.-J., 1988b, Ap.J., 328, 671.Google Scholar
Clayton, M.L, and Feast, M.W. 1969, Mon.Not.R.Astron.Soc., 146, 4ll.Google Scholar
Cosner, K., and Truran, J.W. 1981, Ap. Space Sci., 78, 85.Google Scholar
Dean, Ch. A. 1974, Astron.J., 81, 364.Google Scholar
Dominy, J.F. 1984, Ap. J. Suppl., 55, 27.Google Scholar
Dominy, J.F., and Wallerstein, G. 1986, Ap.J., 310, 371.Google Scholar
Dominy, J.F., Wallerstein, G., and Suntzeff, N.B. 1986, Ap.J., 300, 325.Google Scholar
Feast, M.W. 1963, Mon.Not.R.Astron.Soc, 125, 367.Google Scholar
Glass, L.S., and Lloyd Evans, T. 1981, Nature, 291, 303.Google Scholar
Hollowell, D.E. 1987, in Late Stages of Stellar Evolution, eds Kwok, S. and Pottasch, S.R., (Reidel: Dordrecht), p.239.Google Scholar
Iben, I., Jr. 1983, Ap.J. (Lett), 275, L6.Google Scholar
Iben, I., Jr. 1987, in Late Stages of Stellar Evolution, eds Kwok, S. and Pottasch, S.R., (Reidel: Dordrecht), p.175.Google Scholar
Iben, I. Jr., and Renzini, A. 1982a. Ap.J. (Letters), 259, L79.Google Scholar
Iben, I. Jr., and Renzini, A. 1982b, Ap.J. (Letters), 263, L23.Google Scholar
Iben, I. Jr., and Renzini, A. 1983, Annu. Rev. Astron. Astrophys., 21, 271.Google Scholar
Johnson, H.R. and Ake, T.B. 1986, New Insights in Astrophysics -- 8 Years of UV Astronomy with IUE, ed E.}Rolfe, , ESA-SP-263, p. 395.Google Scholar
Jorissen, A. and Mayor, M. 1988, Astron. Ap., (in press).Google Scholar
Keenan, P.C., 1954, Ap.J., 120, 484.Google Scholar
Lambert, D.L., Gustafsson, B., Eriksson, K., and Hinkle, K.H. 1986, Ap.J. Suppl., 62, 373.Google Scholar
Lattanzio, J.C. 1986, Ap.J., 311, 708.Google Scholar
Lattanzio, J.C. 1987a, Ap.J. (Letters), 313, L15.Google Scholar
Lattanzio, J.C. 1987b, in Late Stages of Stellar Evolution, eds Kwok, S. and Pottasch, S.R. (Dordrecht: Reidel), p.235.Google Scholar
Little-Marenin, I.R., and Little, S.J. 1979, Astron.J., 84, 1374.Google Scholar
Little-Marenin, I.R., and Little, S.J. 1987a Astron.J., 93, 1539.Google Scholar
Little, S.J., Little-Marenin, I.R., and Bauer, W.H. 1987, Astron. J., 94, 981.Google Scholar
Mathews, G.J., Takahashi, K., Ward, R.A., and Howard, W.H. 1986, Ap.J., 302, 41O.Google Scholar
McClure, R.D. 1983, Ap.J., 268, 264.Google Scholar
McClure, R.D. 1984, Pubi. Astron. Soc. Pac, 96, 117.Google Scholar
McClure, R.D., Fletcher, J.M., and Nemec, J.M. 1980, Ap.J. (Letters), 238, L35.Google Scholar
Merrill, P. 1952, Ap.J., 116, 21.Google Scholar
Peery, B.F. 1971, Ap.J., 163, LI.Google Scholar
Robertson, B.S.C., and Feast, M.W. 1981, Mon.Not.R.Astron.Soc, 196, 111.Google Scholar
Scalo, J.M., and Miller, G.E. 1981, Ap.J., 246, 251.Google Scholar
Schatz, G. (1983), Astron. Astrophys., 122, 327.Google Scholar
Smith, V.V. 1987, in Late Stages of Stellar Evolution, eds Kwok, S. and Pottasch, S.R. (Dordrecht: Reidei), p. 241.Google Scholar
Smith, V.V. and Lambert, D.L. 1985, Ap.J., 294, 326.Google Scholar
Smith, V.V. and Lambert, D.L. 1986 Ap.J., 311, 843.Google Scholar
Smith, V.V. and Lambert, D.L. 1987, Astron.J., 94, 977.Google Scholar
Smith, V.V. and Lambert, D.L. 1988, Ap.J., (in press).Google Scholar
Smith, V.V., and Wallerstein, G. 1983, Ap.J., 27, 742.Google Scholar
Smith, V.V. Lambert, D.L., and McWilliam, A. 1987, Ap.J., 320, 862.Google Scholar
Utsumi, K. 1985, in Cool Stars with Excesses of Heavy Elements, Ap. Space Sc. Library, Vol 114., (eds Jaschek, M. and Keenan, P.C.) (Reidel: Dordrecht), p. 243.Google Scholar
Wallerstein, G. and Dominy, J.F. 1988, Ap.J., 330, 937.Google Scholar
Willson, L.A. 1982, in Pulsations in Classical and Cataclysmic Variable Stars, ed. Cox, J.P. and Carl J. Hansen (Boulder, CO:JILA), p. 269.Google Scholar
Winters, P.R., and Macklin, R.L. 1987, Ap.J., 313, 808.Google Scholar
Wood, P.R., 1980, in Physical Processes in Red Giants, eds Iben, Jr, I. and Renzini, A. (Dordrecht: Reidel), p.135.Google Scholar
Wood, P.R., 1985, in Cool Stars with Excesses of Heavy Elements, Ap. Space Sc. Library, Vol 114., (eds Jaschek, M. and Keenan, P.C.) (Reidel: Dordrecht), p.357.Google Scholar