Non lte abundance analysis k sc
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Non-LTE abundance analysis: K & Sc. Huawei Zhang Department of Astronomy, School of Physics, Peking University. Collaborators:. Thomas Gehren (LMU) Keith Butler (LMU) Shi Jianrong (NAOC) Zhao Gang (NAOC). The history of the Galaxy is written in the evolution of its composition .

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Non-LTE abundance analysis: K & Sc

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Non lte abundance analysis k sc

Non-LTE abundance analysis:K & Sc

Huawei Zhang

Department of Astronomy,

School of Physics, Peking University


Non lte abundance analysis k sc

Collaborators:

  • Thomas Gehren (LMU)

  • Keith Butler (LMU)

  • Shi Jianrong (NAOC)

  • Zhao Gang (NAOC)


Non lte abundance analysis k sc

  • The history of the Galaxy is written in the evolution of its composition.

  • The low mass unevolved stars have long lifetimes, some of them have comparable to the age of the Galaxy.

  • Their atmospheric compositions have preserved much of their natal interstellar clouds.


Non lte abundance analysis k sc

  • The determination of the element abundances in stars of different metallicities is important for understanding the chemical evolution of the Milky way.


Abundance analysis

Abundance analysis

  • Still today, the vast majority of abundance analyses of late-type stars rely on the assumption of local thermodynamic equilibrium (LTE).

  • Departures from LTE are common place and often quite important.


Lte vs nlte

LTE vs. NLTE

  • LTE: The level populations can be directly computed from the local gas temperature by the use of the Boltzmann and Saha distributions.

  • NLTE: These rate equations must be solved simultaneously with radiative transfer equation for all relevant frequencies.


Non lte abundance analysis k sc

  • K (Z=19) and Sc (Z=21) are odd-Z elements.


K sc nlte model

K & Sc NLTE model

K

Sc


Non lte abundance analysis k sc

K lines: LTE vs. NLTE

KI: 7698


Potassium results the sun zhang et al 2006 a a 453 723

Potassium results: the SunZhang et al., 2006,A&A, 453, 723

  • Average solar potassium abundance:

    log (K) = 5.12±0.03

  • Corresponds to the meteoritic value (Grevesse & Sauval, 1998).


Potassium results metal poor stars zhang et al 2006 a a 457 645

Potassium results: metal-poor starsZhang et al., 2006, A&A, 457, 645

  • 58 metal-poor stars

  • DSAZ FOCES

  • R ~ 40000

  • S/N ~ 100-200


Non lte abundance analysis k sc

  • The NLTE corrections for metal-poor stars are negative and the average of -0.40 dex.


Potassium results metal poor stars zhang et al 2006 a a 457 6451

Potassium results: metal-poor starsZhang et al., 2006, A&A, 457, 645

Samland(1998)

Goswami & Prantzos (2000)

Timmes et al. (1995)


Scandium results the sun zhang et al 2008 a a 481 489

Scandium results: the SunZhang et al., 2008,A&A, 481, 489

NLTE

LTE

Sc I 5671

LTE

NLTE

Sc II 5526


Non lte abundance analysis k sc

LTE result:

Sc II

  • Sc I: 2.90±0.09

  • Sc II: 3.10±0.05

Sc I


Non lte abundance analysis k sc

NLTE result:

Sc I

  • Sc I: 3.08±0.05

  • Sc II: 3.07±0.04

Sc II

Sc I

Sc II

Sc II

Sc I


Scandium results metal poor stars zhang et al 2008 in preparation

Scandium results: metal-poor starsZhang et al., 2008,in preparation

[Sc/Fe] ~ [Fe/H]

Thick disk

Halo

Thin disk


Non lte abundance analysis k sc

Thank You !


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