Keck HIRES spectroscopy of SkyMapper commissioning survey candidate extremely metal-poor stars. Issue 4 (7th March 2019)

• Record Type: Journal Article
• Authors: Marino, A F; Da Costa, G S; Casey, A R; Asplund, M; Bessell, M S; Frebel, A; Keller, S C; Lind, K; Mackey, A D; Murphy, S J; Nordlander, T; Norris, J E; Schmidt, B P; Yong, D
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 485:Issue 4(2019)
• Page Start: 5153
• Page End: 5167
• Publication Date: 2019-03-07
• Subjects: stars: abundances -- stars: Population II -- Galaxy: halo -- Galaxy: stellar content; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stz645
• Languages: English
• ISSNs: 0035-8711

Abstract

Abstract: We present results from the analysis of high-resolution spectra obtained with the Keck HIRES spectrograph for a sample of 17 candidate extremely metal-poor (EMP) stars originally selected from commissioning data obtained with the SkyMapper telescope. Fourteen of the stars have not been observed previously at high dispersion. Three have [Fe/H] ≤ −3.0, while the remainder, with two more metal-rich exceptions, have −3.0 ≤ [Fe/H] ≤ −2.0 dex. Apart from Fe, we also derive abundances for the elements C, N, Na, Mg, Al, Si, Ca, Sc, Ti, Cr, Mn, Co, Ni, and Zn, and for n -capture elements Sr, Ba, and Eu. None of the current sample of stars is found to be carbon-rich. In general, our chemical abundances follow previous trends found in the literature, although we note that two of the most metal-poor stars show very low [Ba/Fe] (∼−1.7) coupled with low [Sr/Ba] (∼−0.3). Such stars are relatively rare in the Galactic halo. One further star, and possibly two others, meet the criteria for classification as a r -I star. This study, together with that of Jacobson et al. (2015 ), completes the outcomes of the SkyMapper commissioning data survey for EMP stars.