Hobby-Eberly Telescope Chemical Abundances of Stars in the Halo (CASH) Project: Spectroscopic Analyses of the First ~80 Stars 5 May 2010 Julie Krugler Hollek

Acknowledgments ● Advisor: Chris Sneden ● Committee Members: ● Volker Bromm ● Harriet Dinerstein ● Matthew Shetrone ● Collaborators: ● Anna Frebel ● Ian Roederer

Talk Outline ● Background ● CASH Project ● Data Processing ● Calibration ● Results ● Outlook

What do MPS tell us?

Why do we need large surveys?

Chemical Abundances of Stars in the Halo ● “high” resolution survey of ~500 halo stars ● Using HET High Resolution Spectrograph ● R ~ ● S/N ~ 50 ● Analysis: ● Chemical abundances ● Radial velocities

CASH Goals ● Statistical ● Abundance trends ● Abundance frequencies ● Discovery of chemically peculiar stars

CASH To Do List ● Data Processing ● Data reduction ● Wavelength calibration ● Equivalent width measurement ● Stellar parameter determination ● Abundance determination ● Calibration ● Check on pipelines and equivalent width measurement – Standard stars – Comparison to high resolution data ● Science

Data Reduction ● REDUCE IDL software (Piskanov 200?) ● Wavelength calibration – IDL ● Normalization - IRAF

Equivalent Width Measurement ● IDL program (Roederer, in prep 2010) ● Fits a Voigt profile to each line ● Lorentzian + Gaussian

Stellar Parameters and Abundance Determination ● Newly created batch mode MOOG ● Iteratively determines stellar parameters based on Fe, Ti lines ● Determines abundances for multiple elements – Equivalent width – Synthesis ● Carbon abundances determined through by-hand synthesis

Calibration ● Need to test stellar parameter and abundance pipelines for accuracy ● Comparison to standard (HD and BD) stars ● Comparison to high resolution spectra of new stars

Standard Stars: Equivalent Width Comparison ● Equivalent width comparison ● (IUR, Gratton Plots) ● Standard deviations:

Standard Stars: Stellar Parameters ● HRD plot ● Spectroscopic T eff, log g, v t

Standard Stars: Abundances

AAT Stars: Equivalent Width Comparison

AAT Stars: Abundance Comparison

Abundances ● Distribution in [Fe/H]

Elemental ● Plots for: Ca, Mg, Ba, Li, Sr, O, C, Ni

Chemically Peculiar Stars ● HK II Li giant (Roederer et al. 2007/8) ● HE ● DLSB ● Alpha-poor? ● HE ● High C, low Ba, Sr ● ● High Ba, Sr, low C

Future Work ● Completing set of 500 stars ● Comparison to supernova yields ● Double lined spectroscopic binaries ● Abundance frequencies ● Follow up interesting stars

Conclusions