Li isotopes in halo stars Spectral line formation Big Bang - - PowerPoint PPT Presentation

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Li isotopes in halo stars Spectral line formation Big Bang - - PowerPoint PPT Presentation

Jul 11, 2023 230 likes •523 views

Li isotopes in halo stars Spectral line formation Big Bang nucleosynthesis Stellar evolution Karin Lind, MPA Garching In collaboration with Martin Asplund, Corinne Charbonnel, Remo Collet, Frank Grundahl, Jorge Melndez & Francesca

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SLIDE 1

Li isotopes in halo stars

Karin Lind, MPA Garching

In collaboration with Martin Asplund, Corinne Charbonnel, Remo Collet, Frank Grundahl, Jorge Meléndez & Francesca Primas

Big Bang nucleosynthesis Spectral line formation Stellar evolution

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SLIDE 2

Outline

  • 7Li surface evolution in metal-poor globular

clusters

– Has 7Li been depleted? YES MAYBE NO

  • Measuring 6Li in three metal-poor halo stars

– Has 6Li been detected? YES MAYBE NO

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SLIDE 3

Outline

  • 7Li surface evolution in metal-poor globular

clusters

– Has 7Li been destroyed ? YES MAYBE NO

  • Measuring 6Li in three metal-poor halo stars

– Do they contain 6Li ? YES MAYBE NO Said about the cosmological Li problems:

”There is too little of

  • ne of them and too

much of the other, right?”

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SLIDE 4

Li depletion in Pop I & II

Data sources: Boesgaard et al 1986 Cayrel et al 1984 Burkhart & Coupry 1986 Melendez et al 2010

Hyades 0.7Gyr [Fe/H]~0 Halo field 13Gyr [Fe/H]~-2 Initial A(Li)~3.3? Initial A(Li)~2.7? AGE

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SLIDE 5

Li evolution in low- mass stars

Lind+ 2009

NGC6397

Spite plateau

1st dredge up Extension of CZ Extra mixing

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SLIDE 6

How much 7Li is destroyed

  • n the Spite Plateau?

0.0 0.2 0.4 0.6 0.8 log(L/Lsun) 1.6 1.8 2.0 2.2 2.4 2.6 2.8 A(Li) NGC6397 M30 12500Myr_T6.0_FeH2.11 Initial abundance WMAP+SBBN dwarfs turnoff point subgiants

Models by Richard +

“Low” turbulence: ~0.2dex depletion “High” turbulence: ~0.4dex depletion New Li data for M30 [Fe/H]=-2.4

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SLIDE 7

How much 7Li is destroyed

  • n the Spite Plateau?

0.0 0.2 0.4 0.6 0.8 log(L/Lsun) 1.6 1.8 2.0 2.2 2.4 2.6 2.8 A(Li) NGC6397 M30 12500Myr_T6.0_FeH2.11 Initial abundance WMAP+SBBN dwarfs turnoff point subgiants 0.0 0.2 0.4 0.6 0.8 log(L/Lsun) 1.6 1.8 2.0 2.2 2.4 2.6 2.8 A(Li) NGC6397 M30 12500Myr_T6.25_FeH2.11 Initial abundance WMAP+SBBN dwarfs turnoff point subgiants

Models by Richard +

“Low” turbulence: ~0.2dex depletion “High” turbulence: ~0.4dex depletion New Li data for M30 [Fe/H]=-2.4

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SLIDE 8

Another aspect of the problem

– “High turbulence” (T6.25)

  • Explains ~0.4dex of 7Li depletion
  • Cannot explain why subgiants appear more Li rich

than turn-off stars – “Low turbulence” (T6.00)

  • Explains ~0.2dex of 7Li depletion - not enough
  • Reproduces qualitatively a dredge up of settled 7Li

in subgiants Predicts >1.6dex depletion of 6Li Predicts similar depletion of 6Li

  • cf. Meléndez+,

Gonzalez-Hernandez+

  • cf. Korn+,

Nordlander poster

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SLIDE 9

Outline

  • 7Li surface evolution in metal-poor globular

clusters

– Has 7Li been depleted? YES MAYBE NO

  • Measuring 6Li in three metal-poor halo stars

– Has 6Li been detected YES MAYBE NO But how much?

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SLIDE 10

Origin of 6Li?

6Li

depletion?

Galactic cosmic ray production Asplund +

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SLIDE 11

A brief history of HD84937 ([Fe/H]=-2.1)

  • Hobbs et al. 1993/1997

– 8 ± 4% 1D LTE

  • Smith et al. 1993/1998

– 6 ± 3% 1D LTE

  • Asplund et al 2009:

– 5 ± 1 % 3D NLTE

  • Steffen et al 2009:

– 5 ± 1 % 3D NLTE

Asplund +

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SLIDE 12

A brief history of HD84937 ([Fe/H]=-2.1)

  • Hobbs et al. 1993/1997

– 8 ± 4% 1D LTE

  • Smith et al. 1993/1998

– 6 ± 3% 1D LTE

  • Asplund et al 2009:

– 5 ± 1 % 3D NLTE

  • Steffen et al 2009:

– 5 ± 1 % 3D NLTE

Asplund +

Steffen+ 2009

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SLIDE 13

Convective asymmetry mistaken for 6Li?

Line strength:

7Li abundance

1D/3D LTE/NLTE Line profile:

6Li/7Li

1D/3D LTE/NLTE Broadening

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SLIDE 14

3D+NLTE spectrum synthesis

STAGGER (R. Collet) simulations of 3 metal-poor halo stars on Spite plateau LTE profiles computed with SCATE (W. Hayek) from 20 snapshots NLTE/LTE ratio of LiI and CaI lines obtained with MULTI3D (J. Leenaarts+) from 4 snapshots

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SLIDE 15

3D+NLTE spectrum synthesis

STAGGER (R. Collet) simulations of 3 metal-poor halo stars on Spite plateau LTE profiles computed with SCATE (W. Hayek) from 20 snapshots NLTE/LTE ratio of LiI and CaI lines obtained with MULTI3D (J. Leenaarts+) from 4 snapshots

I.e. this analysis uses: New STAGGER models New 3D spectrum synthesis codes in LTE and NLTE New χ2-minimization routines

Independent of previous work

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SLIDE 16

3D+NLTE spectrum synthesis

NLTE level populations computed column-by- column for efficiency LC rays cast into tilted cube at different anglesà 3D, NLTE flux profile

LiI & CaI treated in NLTE

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SLIDE 17

3D+NLTE spectrum synthesis

LiI & CaI treated in NLTE

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SLIDE 18

3D+NLTE spectrum synthesis

LiI & CaI treated in NLTE

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SLIDE 19

Rotational broadening

Δvsini :1km/s à Δ6Li/7Li: ~7% Need independent constraints on broadening for credible results Remember that micro- &macroturbulence are

  • bsolete in 3D
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SLIDE 20

Observational data

Extremely challenging measurement. Keck spectra: HD84937 G64-12 HD140283 S/N = 800 – 1200 R=~100 000

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SLIDE 21

χ2-minimization

1) Determine RV and re- normalize 2) Determine abundance 3) Determine rotational broadening 4) Determine Isotopic ratio

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SLIDE 22

Results: G64-12

Method (3D) vsini 7Li 6Li/7Li Only Li LTE 3.67±0.27 2.128 1.5±2.2% Only Li NLTE 1.69±0.61 2.222 1.3±1.6%

  • Sel. LTE (18)

2.80±0.02 2.115 4.8±1.4%

  • Sel. NLTE (13) 1.93±0.07

2.223 1.1±1.2%

[Fe/H]=-3.0 Teff=6400K log(g)=4.2 vsini from NaI, MgI, CaI, FeI in LTE vsini from CaI in NLTE + ScII, TiII, FeII in LTE

Preliminary

Anything between 1-5%..

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SLIDE 23

Results: G64-12

[Fe/H]=-3.0 Teff=6400K log(g)=4.2

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SLIDE 24

Results: HD140283

Method (3D) vsini 7Li 6Li/7Li Only Li LTE 3.53±0.09 1.843 2.3±0.5% Only Li NLTE 1.71±0.19 2.126 (-0.1±0.3%)

  • Sel. LTE (16)

2.31±0.02 1.824 5.5±0.4%

  • Sel. NLTE (4)

2.14±0.03 2.127 (-1.3±0.3%)

[Fe/H]=-2.5 Teff=5750K log(g)=3.7

Preliminary

Anything between 0-5%..

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SLIDE 25

Results: HD84937

Method (3D) vsini 7Li 6Li/7Li Only Li LTE 3.51±0.26 1.956 2.9±2.1% Only Li NLTE 2.25±0.42 2.151 0.7±1.0%

  • Sel. LTE (10)

2.82±0.03 1.944 5.5±1.3%

  • Sel. NLTE (3)

1.99±0.04 2.150 0.8±0.8%

[Fe/H]=-2.0 Teff=6250K log(g)=4.0

Preliminary

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SLIDE 26

Results: HD84937

[Fe/H]=-2.0 Teff=6250K log(g)=4.0

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SLIDE 27

Outline

  • 7Li surface evolution in metal-poor globular

clusters

– Has 7Li been depleted? YES MAYBE NO

  • Measuring 6Li in three metal-poor halo stars

– Has 6Li been detected? YES MAYBE NO Significant isotopic ratios (~5%) are found when constraining broadening by other neutral lines in LTE. It is possible that these are artificially produced by the LTE assumption. But how much?

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SLIDE 28

Outline

  • 7Li surface evolution in metal-poor globular

clusters

– Has 7Li been destroyed ? YES MAYBE NO

  • Measuring 6Li in three metal-poor halo stars

– Do they contain 6Li ? YES MAYBE NO Significant isotopic ratios (~5%) are found when constraining broadening by other neutral lines in LTE. It is possible that these are artificially produced by the LTE assumption. But how much? WARNING!

Differences and inconsistencies w.r.t. previous work have not yet been carefully investigated