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PI Total time #CoIs, team

Verification of the “Be age” of NGC 6397.

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PI Total time #CoIs, team

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  1. Verification of the “Be age” of NGC 6397. High resolution near-UV spectroscopy of selected turn-off stars in globular cluster NGC 6397, in order to measure beryllium abundances of these stars to determine so-called “Be age” of the cluster. Main objective is to verify the value obtained by Pasquini et al. (2005). • PI • Total time • #CoIs, team Gabriel Szász 3.1n (ELT 42m) team of 4 people, experienced in near-UV spectroscopy, data reduction and spectrum synthesis

  2. Scientific Rationale • Beryllium abundance of TO stars in globular cluster, can be used as independent indicator of the cluster age • To use “Be age” as reliable cosmic chronometer for distant objects, it is necessary to test it on the close objects first and compare it to independent methods.

  3. Immediate Objective • Perform near UV spectroscopic observation around wavelength 313.1 nm (Be II doublet) of: • selected TO stars in NGC 6397 (S/N > 100) • reference star HD 218502 NGC 6397 HD 218502 log(Be/H)

  4. ELT Justification: The brightest TO stars in the cluster (V=16.5) are already at the limit of the UVES instrument. Legacy Value: Precise age of the cluster TO stars, in combination with known C, N, O abundances provides insight into the formation of the cluster. This is also the first step to exploit E-ELT capabilities to determine the “Be age” of the more distant globular clusters. Data Reduction: E-ELT provides sufficient S/N. There are expected no serious data reduction challenges. Run MP Mode AO T. FOV Pixel  Notes 313.1 nm A 5 R=50000 None 3.1n 5’ 50 Be II doublet Run Target R.A. Dec. ToT Mag Notes A NGC 6397 23h -54˚ 3n <16.5 S/N ~ 102 A HD 218502 18h -15˚ 0.1n 8.5 S/N > 102

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