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7Li in Metal-Poor Stars: The Spread of the Li Plateau

Published online by Cambridge University Press:  25 May 2016

Sean G. Ryan
Sean G. Ryan*
Affiliation:
Dept of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK

Abstract

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A highly homogeneous study of 23 halo field dwarf stars has achieved a Li abundance accuracy of 0.033 dex per star. The work shows that the intrinsic spread of the Li abundances of these stars at a given metallicity is < 0.02 dex, and consistent with zero. That is, the Spite Li plateau for halo field dwarfs is incredibly thin. The thinness rules out depletion by more than 0.1 dex by a rotational-induced extra-mixing mechanism. Despite the thinness of the plateau, an increase of Li with [Fe/H] is seen, interpreted as evidence of Galactic chemical evolution (GCE) of Li, primarily due to Galactic cosmic ray (GCR) spallation reactions in the era of halo formation. The rate of Li evolution is concordant with: (1) observations of spallative 6Li in halo dwarfs; (2) GCE models; and (3) data on Li in higher metallicity halo stars. New data have also revealed four new ultra-Li-deficient halo dwarfs, doubling the number known. Based on their propensity to cluster at the halo main sequence turnoff and also to exist redward of the turnoff, we hypothesise that they are the products of binary mergers that ultimately will become blue stragglers. We explain their low Li abundances by normal pre-main-sequence (and possibly main-sequence) destruction in the low mass stars prior to their merging. If this explanation is correct, then such stars need no longer be considered an embarrassment to the existence of negligible Li destruction in the majority of field halo dwarfs.

Type
4. Lithium Abundances
Information
Symposium - International Astronomical Union , Volume 198: The Light Elements and their Evolution , 2000 , pp. 249 - 258
Copyright
Copyright © Astronomical Society of the Pacific 2000 

References

Alonso, A., Arribas, S., & Martínez-Roger, C. 1996, A&AS, 117, 227 Google Scholar
Bell, R. A. & Oke, J. B. 1986, ApJ, 307, 253 Google Scholar
Boesgaard, A. M., Deliyannis, C. P., Stephens, A., & King, J. R. 1998, ApJ, 493, 206 Google Scholar
Boesgaard, A. M. & Steigman, G. 1985, ARAA, 23, 319 Google Scholar
Boesgaard, A. M. & Tripicco, M. J. 1986a, ApJ, 302, L49 Google Scholar
Boesgaard, A. M. & Tripicco, M. J. 1986b, ApJ, 303, 724 Google Scholar
Bonifacio, P. & Molaro, P. 1997, MNRAS, 285, 847 Google Scholar
Cayrel, R., Spite, M., Spite, F., Vangioni-Flam, E., Cassé, M., & Audouze, J. 1999, A&A, 343, 923 Google Scholar
Deliyannis, C. P., Demarque, P., & Kawaler, S. D. 1990, ApJS, 73, 21 Google Scholar
Deliyannis, C. P., Pinsonneault, M. H., & Duncan, D. K. 1993, ApJ, 414, 740 Google Scholar
Deliyannis, C. P. & Ryan, S. G. 2000, in prep Google Scholar
Fields, B. D. & Olive, K. A. 1999, New Astronomy, 4, 255 Google Scholar
Fields, B. D. & Olive, K. A. 1999, ApJ, 516, 797 Google Scholar
Hanson, R. B., Sneden, C., Kraft, R. P., & Fulbright, J. 1998, AJ, 116, 1286 CrossRefGoogle Scholar
Hobbs, L. M., & Thorburn, J. A. 1994, ApJ, 428, L25–L28 Google Scholar
Hobbs, L. M., Welty, D. E., & Thorburn, J. A. 1991, ApJ, 373, L47 Google Scholar
Magain, P. 1987, A&A, 181, 323 Google Scholar
Hobbs, L. M. & Thorburn, J. A. 1997, ApJ, 491, 772 CrossRefGoogle Scholar
Lambert, D. L., Heath, J. E., & Edvardsson, B. 1991, MNRAS, 253, 610 Google Scholar
Norris, J. E., Ryan, S. G., & Stringfellow, G. S. 1994, ApJ, 423, 386 Google Scholar
Norris, J. E., Ryan, S. G., Beers, T. C., & Deliyannis, C. P. 1997, ApJ, 485, 370 Google Scholar
Pinsonneault, M. H., Deliyannis, C. P., and Demarque, P. 1992, ApJS, 78, 179 Google Scholar
Pinsonneault, M. H., Walker, T. P., Steigman, G., & Narayanan, V. K. 1999, ApJ, 527, 180 Google Scholar
Rebolo, R., Molaro, P., & Beckman, J. E. 1988, A&A, 192, 192 Google Scholar
Romano, D., Matteucci, F., Molaro, P., & Bonifacio, P. 1999, A&A, in press Google Scholar
Ryan, S. G., Beers, T. C., Deliyannis, C. P., & Thorburn, J. A. 1996, ApJ, 458, 543 Google Scholar
Ryan, S. G., Beers, T. C., Olive, K. A., Fields, B. D., & Norris, J. E. 2000a, ApJL, in press Google Scholar
Ryan, S. G., Beers, T. C., Kajino, T., & Rosolankova, K. 2000c, in prep Google Scholar
Ryan, S. G., Kajino, T., Beers, T. C., Suzuki, T., Rosolankova, K., & Romano, D. 2000b, in prep Google Scholar
Ryan, S. G., Norris, J. E., & Beers, T. C. 1998, ApJ, 506, 892 Google Scholar
Ryan, S. G., Norris, J. E., & Beers, T. C. 1999, ApJ, 523, 654 Google Scholar
Smith, V. V., Lambert, D. L., & Nissen, P.-E. 1993, ApJ, 408, 262 Google Scholar
Smith, V. V., Lambert, D. L., & Nissen, P. E. 1998, ApJ, 506, 405 Google Scholar
Spite, F. & Spite, M. 1982, A&A, 115, 357 Google Scholar
Spite, F. & Spite, M. 1993, A&A, 279, L9 Google Scholar
Spite, M., Molaro, P., Francois, P., & Spite, F. 1993, A&A, 271, L1 Google Scholar
Spite, M., & Spite, F. 1981, IAU Coll. 68, Astrophysical Parameters for Globular Clusters, David Phillip, A. G. & Haynes, D. S. eds (Kluwer, Dordrecht)Google Scholar
Thorburn, J. A. 1992, ApJ, 399, L83 Google Scholar
Thorburn, J. A. 1994, ApJ, 421, 318 Google Scholar