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Abundances in M92

Abundances in M92. Center for Stellar and Planetary Astrophysics Monash University. Summary prepared by John Lattanzio, Oct 2003. M92: Everything you need to know!. M92: Everything you need to know!. Lower HRD. Upper HRD. What’s special abut M92?. One of the most metal-poor:

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Abundances in M92

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  1. Abundances in M92 Center for Stellar and Planetary Astrophysics Monash University Summary prepared by John Lattanzio, Oct 2003

  2. M92: Everything you need to know!

  3. M92: Everything you need to know! Lower HRD Upper HRD

  4. What’s special abut M92? • One of the most metal-poor: [Fe/H] = -2.2 • One of the oldest: 16Gyr (according to Grundahl et al 2000)

  5. Basic Parameters for M92 • [Fe/H] = -2.2 • Age = 16 Gyr • C = 1.81 • Distance = 27,000 ly • Mass = 330,000 Msun

  6. It all started with….Carbon et al 1982 • Observed 71 red giants (above HB) Solar

  7. It all started with….Carbon et al 1982 • Observed 71 red giants, above HB Variation in C+N too! Large variation in C and N

  8. Langer and Kraft 1984 • Looked at C, N and C+N in various populations • M3 and M13 (same [Fe/H]) • Field Giants • M92 and M15 (same [Fe/H])

  9. Langer and Kraft 1984: M3 and M13

  10. Langer and Kraft 1984: Field giants [Fe/H] < -2 [Fe/H] > -2

  11. Langer and Kraft 1984: M92 and M15

  12. Langer and Kraft 1984 • Average abundances

  13. Norris and Pilachowski 1985 • C+N may be bimodal • N correlates with Na (in all 4 giants studied!)

  14. Langer et al 1986 • Clear decrease of C with L • From as low as Mv=1.5

  15. Pilachowski 1988 • C, N and O in 6 giants • C+N+O is very constant…

  16. Sneden et al 1991 • 9 giants • No variations in [Fe/H] from star to star

  17. Sneden et al 1991 • Two groups: O-rich and O-poor? Low O not seen in field stars! ON cycling?

  18. Sneden et al 1991 • Definite evidence for ON cycling!

  19. Sneden et al 1991 • Possible variation of O with L? Not convincing!

  20. C, N, O, and Na • Clear decrease of C with L • Corresponding increase of N with L • C+N+O constant for some stars • Large spread in C & N at any given L • ON cycling has occurred in some giants • No O variation with L • No Na variation with L

  21. C variation • Clear decrease of C with L from Mv=1.5 Bellman et al 2001

  22. Mv=1.5 is fairly low L… Should we be worried??? • The bump in the LF is at Mv=-0.4 • Nearly 2 mag difference… Bellman et al 2001

  23. First Dredge-Up Start Finish D log L = 0.8 below bump Or 2 mag! LF Bump

  24. C variation with L • So I think they just forgot about FDU! • FDU changes C from base of GB • When L exceeds LF bump then deep mixing continues (mu gradient removed)

  25. But… • Smith and Martell 2003 • Measured values of d[C/Fe]/dMV • Get same value above and below LF bump… Whole of GB Upper GB

  26. C variation with L • Its not clear that FDU and deep mixing should change C at the same rate!!! • Needs work!

  27. Heavy elements: More on Fe • King et al 1998 looked at 3 subgiants in M92: [Fe/H] is 2 x lower than giants!? Checked their data with a standard of similar [Fe/H] (HD 140283) and got same as everyone else…

  28. Heavy elements: More on Fe • King et al 1998: 3 subgiants in M92 were not homogeneous: one was 0.15 dex different to the other two • Gravitational settling? Radiation effects? Richard et al 2002 expect factors of 2 or more in most metal poor systems • Later added data for 2 more subgiants: same average value of [Fe/H]

  29. Heavy elements: More on Fe • Langer et al 1998 • Used over 100 lines of various metals and looked at 3 bright giants • Two are identical • One differs by 0.18 dex from the other two…

  30. Heavy elements:Shetrone looked at Mg, Al, Eu in 6 giants • Intermediate [Fe/H] • High [Fe/H] • Low [Fe/H] Al up when Na up

  31. Heavy elements:Shetrone looked at Mg, Al, Eu in 6 giants • Intermediate [Fe/H] • High [Fe/H] • Low [Fe/H] Al up when Na up and O down

  32. Heavy elements:Shetrone looked at Mg, Al, Eu in 6 giants • Intermediate [Fe/H] • High [Fe/H] • Low [Fe/H] Mg down when Al up

  33. Heavy elements:Shetrone looked at Mg, Al, Eu in 6 giants • Intermediate [Fe/H] • High [Fe/H] • Low [Fe/H] No variation in Eu

  34. Heavy elements:Shetrone looked at Mg, Al, Eu in 6 giants No variation of Al with L

  35. Heavy elements: Neutron capture stuffAronsky et al 1994: 9 giants Elements as expected Ba constant

  36. Heavy elements: Neutron capture stuffAronsky et al 1994: 9 giants No variation with other elements No variation with Te

  37. Heavy elements: Neutron capture stuffAronsky et al 1994: 9 giants • No variation from star-to-star • No variation with evolutionary state • No variation with other elements • At last – something we understand 

  38. Heavy elements: 3 subgiants • King et al 1998 looked at 3 subgiants: Field star Mg depleted compared to field: just like giants in M92 Na enriched compared to field: just like giants in M92 Ba higher compared to field: just like giants in M92 Subgiants show same anomalies as giants!

  39. Heavy Elements: Sneden et al 2000 • 34 giants in M92 (and 31 in M15)

  40. Heavy Elements: Sneden et al 2000 • Ca: no variation • Na: • Large spread • No variation with L or Te • Correlates with N • Ba: no variation

  41. Heavy Elements: Sneden et al 2000 • Ba and Eu are useful… • Ba is lower in M92 than M15 (same [Fe/H]) • Just like M4 and M5 [Ba/Eu] = -0.4 for pure r-process [Ba/Eu] = -0.4 in M4 s-process active in M5 [Ba/Eu] = +0.2 in M5 (only 2 stars!) [Ba/Eu] = -0.4 in M92 [Ba/Eu] = -0.4 in M15 also pure r-process in M15 and M92

  42. Heavy Elements: Sneden et al 2000 • Si varies a lot from cluster to cluster [Si/Fe] = +0.59 M92 Si is primarily made in supernovae from stars With M=20-25 Msun [Si/Fe] = +0.23 NGC6752 NGC6723 [Si/Fe] = +0.68 M4 [Si/Fe] = +0.55 M5 [Si/Fe] = +0.60 Could we be seeing variations in the IMF?

  43. Constraints from Li abundances? • Deliyannis et al 1995 • 4 subgiants have A(Li) = 2 – 2.5 • Boesgaard et al 1998 • 7 subgiants have A(Li) = 2 – 2.6 • Bonifacio reanalized these stars: • Claims A(Li) = 2.3  0.1 ie little spread

  44. Constraints from Li abundances? • Subgiants now a problem • They show Na and Al enhancements • As expected from ON, NeNa and MgAl cycle • But Li not destroyed! • Wherever the hot H burning happened, the Li was added afterwards 

  45. Constraints from Li abundances? • Pilachowski et al 2000 • 60 giants in M92 • None have A(Li) > 0 (Te = 4500K) > 1 (Te = 5000K) Is this consistent with first dredge-up? Is it consistent with deep mixing? Should make some Li!

  46. Summary • Clear evidence for deep mixing on GB via the C and N variations • ON cycling has produced N and Na • Some Al made and Mg destroyed at the same time as the ON cycling and Na production • Na (etc?) variations seen in subgiants also • Some variation in Fe from star to star? From giant to subgiant? • Pure r-process in earlier life, no s-process • Need mixing and primordial variations • Is Li a problem? Or a useful constraint?

  47. Armosky et al, 1994, AJ, 108, 1364 Bellman, et al, 2001, PASP, 113, 326 Boesgaard et al, 1998, ApJ, 493, 206 Bonifacio, 2002, A&A, 395, 515 Buonanno et al, 1985, A&A, 145, 97 Carbon et al , 1982, ApJS, 49, 207 Deliyannis et al, 1995, ApJ, 452, L13 Grundahl et al, 2000, AJ, 120, 1884 King et al, 1998, AJ, 115, 666 Langer & Kraft, 1984, PASP, 96, 339 Langer et al, 1986, PASP, 98, 473 Langer et al, 1998, AJ, 115, 685 Norris & Pilachowski, 1985, ApJ, 299, 295 Pilachowski, 1988, ApJ, 326, L57 Pilachowski et al, 2000, AJ, 119, 2895 Richard et al, 2002, ApJ, 580, 1100 Shetrone, 1996, AJ, 112, 1517 Smith & Martell, 2003, PASP, 115, 1211 Sneden et al, 1991, AJ, 102, 2001 Sneden et al, 2000, AJ, 120, 1351 References

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