Chemical Compositions of Evolved Stars from Near-infrared IGRINS High-resolution Spectra. I. Abundances in Three Red Horizontal Branch Stars

WOS: 000445108500005
We have derived elemental abundances of three field red horizontal branch stars using high-resolution (R similar or equal to 45,000), high signal-to-noise ratio (S/N greater than or similar to 200) H-and K-band spectra obtained with the Immersion Grating Infrared Spectrograph (IGRINS). We have determined the abundances of 21 elements, including alpha (Mg, Si, Ca, S), odd-Z (Na, Al, P, K), Fe-group (Sc, Ti, Cr, Co, Ni), neutron-capture (Ce, Nd, Yb), CNO-group elements. S, P, and K are determined for the first time in these stars. H- and K-band spectra provide a substantial number of S I lines, which potentially can lead to a more robust exploration of the role of sulfur in the cosmochemical evolution of the Galaxy. We have also derived C-12/C-13 ratios from synthetic spectra of the first-overtone (CO)-C-12 (2-0) and (3-1) and (CO)-C-13 (2-0) lines near 23440 angstrom and (CO)-C-13 (3-1) lines at about 23730 angstrom. Comparison of our results with the ones obtained from the optical region suggests that the IGRINS high-resolution H- and K-band spectra offer more internally self-consistent line abundances of the same species for several elements, especially the alpha-elements. This in turn provides more reliable abundances for the elements with analytical difficulties in the optical spectral range.
Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [112T929]; US National Science FoundationNational Science Foundation (NSF) [AST 1211585, AST 1616040, AST-1229522]; University of Texas Rex G. Baker Jr. Centennial Research Endowment; NSFNational Science Foundation (NSF) [AST-1516182]; University of Texas at Austin; Korean GMT Project of KASI
We like to thank Nils Ryde, Brian Thorsbro, and Elisabetta Caffau for helpful discussions. Our work has been supported by The Scientific and Technological Research Council of Turkey (TUBITAK, project No. 112T929), by the US National Science Foundation grants AST 1211585 and AST 1616040, and by the University of Texas Rex G. Baker Jr. Centennial Research Endowment. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. One of the authors (J.E.L.) is supported by the NSF under grant AST-1516182. This work used the Immersion Grating Infrared Spectrometer (IGRINS), which was developed under a collaboration between the University of Texas at Austin and the Korea Astronomy and Space Science Institute (KASI) with the financial support of the US National Science Foundation under grant AST-1229522, of the University of Texas at Austin, and of the Korean GMT Project of KASI.