Proton-capture nucleosynthesis in globular cluster red giant stars

被引:80
作者
Cavallo, RM [1 ]
Sweigart, AV
Bell, RA
机构
[1] Univ Maryland, Dept Astron, College Pk, MD 20742 USA
[2] NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA
关键词
globular clusters; general; nuclear reactions; nucleosynthesis; abundances; stars; interiors; late-type; Population II;
D O I
10.1086/305053
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
Observational evidence suggests that many of the variations of the surface abundances of light- to intermediate-mass elements (A < 28) in globular cluster red giant branch (RGB) stars can be attributed to noncanonical mixing between the surface and the deep stellar interior during the RGB phase. As a first step to studying this mixing in more detail, we have combined a large nuclear reaction network with four detailed stellar evolutionary sequences of different metallicities in order to follow the production and destruction of the C, N, O, Ne, Na, Mg, and Al isotopes around the hydrogen-burning shell (H shell) of globular cluster RGB stars. The abundance distributions determined:by this method allow for the variation in the temperature and density around the H shell as well as for the dependence on both the stellar luminosity and cluster metallicity. Because our nuclear reaction network operates separately from the stellar evolution code, we are able to more readily explore the effects of the uncertainties in the reaction rates on the calculated abundances. We discuss implications of our results for mixing in the context of the observational data. Our results are qualitatively consistent with the observed C versus N, O versus N, Na versus O, and Al versus O anticorrelations and their variations with both luminosity and metallicity. We see evidence for variations in Na without requiring changes in O, independent of metallicity, as observed by Norris and Da Costa in 1995 and Briley and coworkers in 1997. Also, we derive C-12/C-13 ratios near the observed equilibrium value of 4 for all sequences and predict the temperature-dependent O-16/O-17 equilibrium ratio based on new data for the O-17(p, alpha)N-14 reaction rate. Additionally, we discuss the Mg isotopic abundances in light of the recent observations by Shetrone of M13 and NGC 6752.
引用
收藏
页码:575 / 595
页数:21
相关论文
共 86 条
[1]   ABUNDANCES OF THE ELEMENTS - METEORITIC AND SOLAR [J].
ANDERS, E ;
GREVESSE, N .
GEOCHIMICA ET COSMOCHIMICA ACTA, 1989, 53 (01) :197-214
[2]   CN AND CA ABUNDANCE VARIATIONS AMONG THE GIANTS IN M22 [J].
ANTHONYTWAROG, BJ ;
TWAROG, BA ;
CRAIG, J .
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC, 1995, 107 (707) :32-48
[3]   SPECTROSCOPY OVER A RANGE OF 5 MAGNITUDES IN NGC 6752 [J].
BELL, RA ;
HESSER, JE ;
CANNON, RD .
ASTROPHYSICAL JOURNAL, 1984, 283 (02) :615-625
[4]   CARBON ABUNDANCES IN RED GIANT STARS IN THE GLOBULAR-CLUSTERS M92 AND NGC-6397 [J].
BELL, RA ;
DICKENS, RJ ;
GUSTAFSSON, B .
ASTROPHYSICAL JOURNAL, 1979, 229 (02) :604-623
[5]   CHEMICAL ABUNDANCES IN THE GLOBULAR-CLUSTERS M3, M13, AND NGC-6752 [J].
BELL, RA ;
DICKENS, RJ .
ASTROPHYSICAL JOURNAL, 1980, 242 (02) :657-672
[6]   SPECTROSCOPIC ANALYSIS OF DWARF AND SUBGIANT STARS IN 47-TUCANAE [J].
BELL, RA ;
HESSER, JE ;
CANNON, RD .
ASTROPHYSICAL JOURNAL, 1983, 269 (02) :580-591
[7]   MEASUREMENT OF THE O-17(P,ALPHA)N-14 CROSS-SECTION AT STELLAR ENERGIES [J].
BLACKMON, JC ;
CHAMPAGNE, AE ;
HOFSTEE, MA ;
SMITH, MS ;
DOWNING, RG ;
LAMAZE, GP .
PHYSICAL REVIEW LETTERS, 1995, 74 (14) :2642-2645
[8]   C AND N ABUNDANCES AMONG 47 TUCANAE MAIN-SEQUENCE STARS [J].
BRILEY, MM ;
HESSER, JE ;
BELL, RA .
ASTROPHYSICAL JOURNAL, 1991, 373 (02) :482-496
[9]   VARIATIONS IN C-12/C-13 AS AN EXPLANATION FOR THE 3883-A CN-BIMODALITY AMONG 47 TUCANAE SUBGIANTS [J].
BRILEY, MM ;
BELL, RA ;
SMITH, GH ;
HESSER, JE .
ASTROPHYSICAL JOURNAL, 1989, 341 (02) :800-807
[10]   AN ANALYSIS OF G-BAND STRENGTHS IN NGC-6397 AND M55 RED GIANTS [J].
BRILEY, MM ;
BELL, RA ;
HOBAN, S ;
DICKENS, RJ .
ASTROPHYSICAL JOURNAL, 1990, 359 (02) :307-318