Abundances in NGC6397

1. Abundances in NGC6397 Summary prepared by John Lattanzio, Feb 2004 Center for Stellar and Planetary Astrophysics Monash University

2. NGC6397: Everything you need to know!?

3. NGC6397: Back to Basics • [Fe/H] = -2.0 • Age = Old… 13.9 Gyr • =13.5 with diffusion included • Distance = 9,000 ly = closest • Log (M/M0) = ? • m-M = 12.2 – 12.6 • C = 2.50

4. NGC6397: HRD etc • [a/Fe] = +0.34 • V (HB) = 13.1 V (TO) = 17 • V (RGB tip) = 10 • HB is short andblue

5. Carbon on the Giant Branch • Briley et al 1990 looked at many stars • Found C varies with L

6. Carbon on the Giant Branch

7. O-Na anti-correlation - a bit! Minniti et al 1996 • Look at O and Na • In 5 bright giants

8. Castillho et al 2000 • 5 giants • 11 subgiants • [a/Fe] mildly up • [O/Fe]  0.15 • [Ca/Fe]  0.2 • [Si/Fe]  0.2 • [Ti/Fe]  0.4 • Star to star < 0.25 dex • S-elements slightly down: [s/Fe]  -0.2

9. Castillho et al 2000 • 5 giants • 11 subgiants • [a/Fe] mildly up • [O/Fe]  0.15 • [Ca/Fe]  0.2 • [Si/Fe]  0.2 • [Ti/Fe]  0.4 • Star to star < 0.25 dex • S-elements slightly down: [s/Fe]  -0.2

10. Gratton et al 2001 • MS and TO of NGC6397 and NGC6752 • Whereas NGC6752 shows much variation, NGC6397 does not • [O/Fe] = 0.21 • [Na/fe] = 0.20 • Star-to-star  0.14 dex • Can be explained by obs error and variance in atmospheric parameters Its very homogeneous!

11. Thevenin et al 2001 • 7 Turnoff stars • Confirmed Gratton et al • Very little scatter

12. Lithium • Molaro and Pasquini 1994 • One turnoff star: A(Li) = 2.35 ± 0.25 • Consistent with Li plateau in field Pop II

13. Lithium: Pasquini and Molaro 1996 • 6 stars, 3 turnoff and 3 subgiants • Points label is A(Li) No/less Li in giants Turnoff all same!

14. Lithium: Pasquini and Molaro 1996 • 6 stars, 3 turnoff and 3 subgiants Consistent with field Pop II stars

15. Lithium • Same result found by Castillho et al 2000 • Bonifacio et al 2002 looked at 12 turnoff stars: A(Li) = 2.34 ± 0.06

16. Dynamics and Mass (for Jarrod) • Drukier et al 1993 • “There is an excess of low M over high M in outer fields compared to inner fields” • ie mass segregation, as expected • Gianpaolo et al 1997 • There is a deficiency of low mass stars • King et al 1998 • Mass Function very smooth down to 0.1M

17. Dynamics and Mass (for Jarrod)

18. Dynamics and Mass (for Jarrod) • Drukier et al 1993 • “There is an excess of low M over high M in outer fields compared to inner fields” • ie mass segregation, as expected • Piotto et al 1997 • There is a deficiency of low mass stars • King et al 1998 • Mass Function very smooth down to 0.1M • DeMarchi et al 2000 • MF turns over precipitously below 0.9M

19. Summary • Evidence for deep mixing on GB via the C and N variations • Slight O-Na correlation • All species below giant branch are HOMOGENEOUS! • Li on MS matches field Pop II • All normal: normal (field) deep mixing…

20. Druckier et al 1993, AJ, 106, 2335 Molaro & Pasquini 1994, A&A, 281, L77 Pasquini & Molaro 1996, A&A, 307, 761 Minniti et al 1996, ApJ, 470, 953 Piotto et al 1997, AJ, 113, 134 King et al 1998, ApJ, 492, L37 DeMarchi et al 2000, ApJ, 530, 342 Castilho et al 2000, A&A, 361, 92 Gratton et al 2001, A&A, 369, 87 Thevenin et al 2001, A&A, 373, 905 Bonifacio et al 2002, A&A, 390, 91 Gratton et al 2003, A&A, 408, 529 Smith and Martell 2003, PASP, 115, 1211 Briley et al 1990, ApJ, 359, 307 References