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

M92: Everything you need to know!

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)

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

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

It all started with….Carbon et al 1982 Observed 71 red giants, above HB

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])

Langer and Kraft 1984: M3 and M13

Langer and Kraft 1984: Field giants

Langer and Kraft 1984: M92 and M15

Langer and Kraft 1984 Average abundances

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

Langer et al 1986 Clear decrease of C with L From as low as M v =1.5

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

Sneden et al giants No variations in [Fe/H] from star to star

Sneden et al 1991 Two groups: O-rich and O-poor?

Sneden et al 1991 Definite evidence for ON cycling!

Sneden et al 1991 Possible variation of O with L?

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

C variation Clear decrease of C with L from M v =1.5 Bellman et al 2001

M v =1.5 is fairly low L… Bellman et al 2001 The bump in the LF is at M v =-0.4 Nearly 2 mag difference…

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

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)

But… Smith and Martell 2003 Measured values of d[C/Fe]/dM V Get same value above and below LF bump…

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

Heavy elements: More on Fe King et al 1998 looked at 3 subgiants in M92: Checked their data with a standard of similar [Fe/H] (HD ) and got same as everyone else…

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]

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…

Heavy elements: Shetrone looked at Mg, Al, Eu in 6 giants Intermediate [Fe/H] High [Fe/H] Low [Fe/H]

Heavy elements: Shetrone looked at Mg, Al, Eu in 6 giants Intermediate [Fe/H] High [Fe/H] Low [Fe/H]

Heavy elements: Shetrone looked at Mg, Al, Eu in 6 giants Intermediate [Fe/H] High [Fe/H] Low [Fe/H]

Heavy elements: Shetrone looked at Mg, Al, Eu in 6 giants Intermediate [Fe/H] High [Fe/H] Low [Fe/H]

Heavy elements: Shetrone looked at Mg, Al, Eu in 6 giants

Heavy elements: Neutron capture stuff Aronsky 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

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

Heavy Elements: Sneden et al giants in M92 (and 31 in M15)

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

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 [Ba/Eu] = +0.2 in M5 [Ba/Eu] = -0.4 in M92 (only 2 stars!) [Ba/Eu] = -0.4 in M15 also

Heavy Elements: Sneden et al 2000 Si varies a lot from cluster to cluster M92 NGC6752 NGC6723 M4 M5 [Si/Fe] = [Si/Fe] = [Si/Fe] = [Si/Fe] = [Si/Fe] = Si is primarily made in supernovae from stars With M=20-25 Msun

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

Constraints from Li abundances? Subgiants now a problem 1) They show Na and Al enhancements 2) As expected from ON, NeNa and MgAl cycle 3) But Li not destroyed! 4) Wherever the hot H burning happened, the Li was added afterwards 

Constraints from Li abundances? Pilachowski et al ) 60 giants in M92 2) 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!

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?

References 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