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) = log10(NX/NH) + 12 for element “X” [X/Y] = log10(NX/NY)★– log10(NX/NY)

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 122563 B = 7.10 V = 6.19 H = 3.76 K = 3.73 575 papers in the literature have something about this star red giant: Teff = 4500K, log(g) = 0.8, [Fe/H] = –2.9 40+ years after my PhD, I’m still working on this same star

HD 140283 B = 7.11 V = 7.21 H = 5.70 K = 5.59 first high-res metal-poor star: Chamerlain & Aller (1952) warm: Teff = 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 54048 is a solar metallicity red horizontal branch star

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staytuned

and most of the IGRINS K Band

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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 122563 probably detections of 1 Na line and 2 Al lines, but

we are not confident of abundances

some lines are obvious, withsome 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 122563?

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 140283 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

http://spiff.rit.edu/classes/phys373/lectures/colors/colors.html

young, higher-mass metal-rich field stars: the red clump

https://en.wikipedia.org/wiki/Horizontal_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. 2012

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:

12C/13C < 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 12C/13C is a telltale sign of CN-

cycle H-burning and envelope mixing

many are low velocity thin disk starsAfşar 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 752

http://www.employees.org/~ddavison/Astro/astro.php?image=ngc752-2.jpg&images=NGC

Böcek Topcu et al. 2015

light elements + HR-diagram = stellar evolutionopen cluster NGC 752

Böcek Topcu et al. 2015

fred

http://www.alsonwongastro.com/ngc6940.htm

red symbols are stars observed by IGRINS

Now attack with IGRINS

fred

http://cs.astronomy.com/asy/m/starclusters/464451.aspx

red symbols are stars observed by IGRINS

Now attack with IGRINS

CNOLi abundances in open cluster giantsELEMENT OPTICAL LINES

IGRINS LINES

lithium Li I 6707Åno features

carbon CH 4300Å – saturated CO all over

C2 5160, 5630Å – weak

nitrogen CN 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: 12C/13C = 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

fred