Center for Stellar and Planetary AstrophysicsMonash University
Summary prepared by John Lattanzio, Oct 2003
Abundances in M92
M92: Everything you need to know!
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 Mv=1.5
Pilachowski 1988
C, N and O in 6 giants C+N+O is very constant…
Sneden et al 1991
9 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 Mv=1.5
Bellman et al 2001
Mv=1.5 is fairly low L…
Bellman et al 2001
The bump in the LF is at Mv=-0.4
Nearly 2 mag difference…
LF Bump
First Dredge-Up
Start
Finish
log L = 0.8 below bumpOr 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]/dMV
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 140283) 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 stuffAronsky et al 1994: 9 giants
Heavy elements: Neutron capture stuffAronsky et al 1994: 9 giants
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
Heavy elements: 3 subgiants King et al 1998 looked at 3
subgiants: Field star
Mg depleted compared to field: just like giants in M92Na enriched compared to field: just like giants in M92Ba higher compared to field: just like giants in M92
Heavy Elements: Sneden et al 2000
34 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
M92NGC6752NGC6723
M4M5
[Si/Fe] = +0.59[Si/Fe] = +0.23[Si/Fe] = +0.68[Si/Fe] = +0.55[Si/Fe] = +0.60
Si is primarily made in supernovae from starsWith M=20-25 Msun
Constraints from Li abundances?
Deliyannis et al 19951) 4 subgiants have A(Li) = 2 – 2.5
Boesgaard et al 19981) 7 subgiants have A(Li) = 2 – 2.62) Bonifacio reanalized these stars:
Claims A(Li) = 2.3 0.1 ie little spread
Constraints from Li abundances?
Subgiants now a problem1) They show Na and Al enhancements2) As expected from ON, NeNa and MgAl
cycle3) But Li not destroyed!4) Wherever the hot H burning happened,
the Li was added afterwards
Constraints from Li abundances?
Pilachowski et al 20001) 60 giants in M922) 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