IGRINS for Stellar Abundances & Nucleosynthesis Chris Sneden, Natalie Gosnell, Dan Jaffe, Greg Mace, Richard Seifert (UT Austin) Hwihyun Kim + IGRINS team members (KASI) Melike Afşar (Ege U, Izmir Turkey) Caty Pilachowski (Indiana U)

Topics for today  two famous very low metallicity stars  is there anything left to discover?  red horizontal-branch stars  better CNO will help solve their existence puzzle  open cluster stars:  IR data can refine their evolutionay states Abundance Definitions  log ε(X) = log 10 (N X /N H ) + 12 for element “X”  [X/Y] = log 10 (N X /N Y ) ★ – log 10 (N X /N Y ) 

Topic I what can we learn about very metal-poor stars with H- and K- band IR spectra?

Two famous very bright, very metal-poor stars HD  B = 7.10 V = 6.19 H = 3.76 K = 3.73  575 papers in the literature have something about this star  red giant: T eff = 4500K, log(g) = 0.8, [Fe/H] = –2.9  40+ years after my PhD, I’m still working on this same star HD  B = 7.11 V = 7.21 H = 5.70 K = 5.59  first high-res metal-poor star: Chamerlain & Aller (1952)  warm: T eff = 5650K, log(g) = 3.4, [Fe/H] = –2.7  a legendary “cheat” on metallicity; a moral lesson for us Afşar et al. 2015, ApJ, submitted

most of the IGRINS H-band in our stars HIP is a solar metallicity red horizontal branch star ✔ ✔ stay tuned

and most of the IGRINS K Band ✔ ✔ ends of orders with lots of tellurics have been chopped here

reductions & analyses in brief  IGRINS pipeline, and IRAF “telluric” package  standard analysis techniques using MOOG code  NIST transition probabilities when available, otherwise Kurucz database  line-to-line scatter is reasonable: σ ≈ 0.1  happiest results: better abundances for “alpha” elements (Mg, Si, S, Ca)  OH, CO molecular lines visible in HD  probably detections of 1 Na line and 2 Al lines, but we are not confident of abundances

some lines are obvious, with some unexpected detections simple extrapolations from Arcturus spectrum predict that Mg I will be strong at low metallicity good question for thesis defenses: why is weak, fragile molecule OH visible in HD ? Note the 1% deep S I lines; these are real

Si I lines are BETTER in the IR analysis issues; watch out! lines are too weak lines are just right for reliable abundances

IGRINS alpha abundances are trustworthy No possibility of getting sulfur in the optical much of the line-line scatter must be in the (NIST) basic line data HD gives similar results, but there are fewer lines in that warmer star optical IGRINS

how low in metallicity can we go??? we could have added in more CO lines only a simple mean was done here arbitrary C, O to fit observed line the syntheses differ by 0.3 dex in C abundan ce

Topic II Application of H- and K-band IGRINS spectra to the curious case of field red horizontal- branch stars

red clump vs red horizontal branch ures/colors/colors.html young, higher-mass metal-rich field stars: the red clump orizontal_branch old, low mass, usually metal-poor stars: the blue and red horizontal branch

why are there so many bright RHB field stars? Afşar et al RC HR diagram of color- selected sample of bright G-type giants Many with Hipparcos parallaxes that confirm their “giant” status filled circles and x symbols have “evolved” carbon isotopic ratios: 12 C/ 13 C < 30

they are not very metal-poor; they are often thin disk; they really(?) are chemically evolved this is a“Toomre” diagram for the field RHB stars low 12 C/ 13 C is a telltale sign of CN- cycle H-burning and envelope mixing many are low velocity thin disk stars Afşar et al. 2012

But believing carbon isotopes from one very weak transition is very risky Afşar et al. 2012

IGRINS to the rescue! one 2%-deep CN optical feature versus a whole IR CO bandheads

and for HIP 54048, better light-element abundances in the IR than in the optical note especially P I, S I, K I only in IR; good agreement between Ti I & Ti II Afşar et al.,in prep

Topic III Some uses of IGRINS spectra for fundamental evolution of open cluster stars

our first effort used optical spectra of NGC Böcek Topcu et al. 2015

light elements + HR-diagram = stellar evolution open cluster NGC 752 Böcek Topcu et al. 2015

fred red symbols are stars observed by IGRINS Now attack with IGRINS

fred red symbols are stars observed by IGRINS Now attack with IGRINS

CNOLi abundances in open cluster giants ELEMENTOPTICAL LINESIGRINS LINES lithiumLi I 6707Åno features carbonCH 4300Å – saturatedCO all over C , 5630Å – weak nitrogenCN mostly >8000ÅCN strong in H oxygen[O I] 6300,6363Å - ??OH all over some other considerations  red giants typically 2-3 mag brighter in K than in V  H and K bands have drastically reduced extinction  mostly can get around gravity worries with CMD

a first IGRINS look at an exotic light element in M67

mostly an easy victory: 12 C/ 13 C = 25 but what are the things that don’t “fit”? ? ? ? ??

where IR spectrum analyses struggle: ions also in the heavy neutron-capture elements

IGRINS spectra of cool stars are dazzling – let’s be half as good as our data! from Pierre Magain’s contribution at IAU Symp 132 (1988): It is just a matter of will: do we intend to continue to provide the Galactic evolution theorists with data we cannot reasonably guarantee their reliability, or will we concentrate part of our efforts on checking the validity of our assumptions? the good news is that IGRINS will bring qualitative advances to our knowledge of stellar chemical compositions... and employment for us for many years! Many thanks for this excellent meeting!

fred