Pinning Down Gravitational Settling
  We analyse high-resolution archival UVES data of turnoff and subgiant stars in the nearby globular cluster NGC 6397 ([Fe/H] = -2). Balmer-profile analyses are performed to derive reddening-free effective temperatures. Due to the limited S/N and uncertainties related to blaze removal, we find the data quality insufficient to exclude the existence of gravitational settling. If the newly derived effective temperatures are taken as a basis for an abundance analysis, the photospheric iron (Fe II) abundance in the turnoff stars is 0.11 dex lower than in the (well-mixed) subgiants. 
Andreas J. Korn (1), Nikolai Piskunov (1), Frank Grundahl (2), Paul   Barklem (1) and Bengt Gustafsson (1) ((1) Uppsala Astr...