David L. Lambert McDonald Observatory

1. RED GIANTS, MOLECULES AND ISOTOPES David L. Lambert McDonald Observatory The IGRINS Workshop – Seoul, Korea August 2010

2. William Herschel (1738-1822) • Discovery of Uranus in 1781 • Discovered the infra-red in 1800 “By placing one thermometer within the [solar] red rays, separated by a prism, and another beyond them, he found the temperature of the outside thermometer raised by more than that of the inside.” Humphrey Davy to Davis Giddy 3 July 1800

3. William Herschel (1738-1822) • Telescope builder and entrepreneur Requested funds from King George III in 1785 for construction (£ 1,395) and operation (£ 150/yr.) of 40-foot long and five feet in diameter reflector.

4. Introduction Certain exciting problems in stellar astrophysics demand high-resolution IR spectra for their solution. IR advantages include: • Cool stars - bright in IR - IR spectra “simpler” than optical - key signatures in IR: molecules primarily for elemental and isotopic abundances - H- opacity minimum at 1.6 µm - higher dust transparency • Cool gas and dust - circumstellar envelopes - prestellar disks IGRINS: Full H plus K coverage

5. Introduction Spectra must be paired with model atmospheres and atomic/molecular data • Atomic spectroscopy: generally high-excitation neutral atomic lines - Limited current or past work on classification and term analyses - Quantitative lab spectroscopy even more limited (gf-values for LTE) - Expect theoretical gf-values to be fairly reliable - Astrophysical data (e.g., gf’s from Sun, Arcturus, etc.)

6. Introduction Molecular spectroscopy • Mix of electronic and vibration-rotation transitions • Molecular data generally good but incomplete, but there are few active centers for lab/theoretical work on astrophysical molecules • Incomplete: stellar column densities » laboratory possibilities (beware of extrapolation) : dissociation energies? : gf-values? : new molecules (ZrS, TiS) • Can usually predict isotopic wavelength shifts

7. Introduction Warm stars – some common molecules detectable in H and K: • H2 quadruple V-R lines (rare) • CN red system • CO V-R υ = 2, 3 • C2 Phillips and Ballik-Ramsay systems • OH V-R υ = 2 • HF V-R υ = 1 Cooler stars – some common polyatomics • H2O • C2H2, HCN

8. A few illustrative examples 1. IR spectra can be simpler - Early M dwarfs in optical dominated by TiO

9. Chavez & Lambert (2009)

10. A few illustrative examples IR spectra can be simpler - M dwarfs have simpler spectra in IR R = 2700 Red = NaI Blue = CaI Grey = H2O Oh for IGRINS! Rojas-Ayala et al. (2010)

11. A few illustrative examples 2. Isotopic Abundances: 12C/13C of Carbon stars - Optical spectra dominated by saturated CN (and C2) lines and very difficult to isolate weak 12CN and 13CN lines - H and K spectra are an easier target from CN and CO lines

12. 13CN • 12CN • Y CVn is 13C-rich Lambert et al. (1986)

13. 13C-rich J stars clearly separated from others Lambert et al. (1986)

14. Lambert et al. (1986)

15. A few illustrative examples 3. Isotopic Abundances: 16O/17O and 16O/18O in M, MS, and S stars M35 TcX 16O/18O = 450 16O/17O = 1900 C17O C18O MS Tc√ 16O/18O = 1000 16O/17O = 1000 Smith & Lambert (1990)

16. Elemental and Isotopic Abundances: The Theoretical Setting Stellar Evolution: The Giant Branches Wasserburg et al. (1999)

17. Stellar Evolution: Asymptotic Giant Branch Unsolved issues in stellar evolution and nucleosynthesis • third dredge-up • hot bottom burning • mass loss Wasserburg et al. (1999)

18. Elemental Abundances: Fluorine from HF Stellar Evolution: Giant Branch Fluorine variations in the Globular Cluster M4 • F variations of 6 times • F correlated with O • F anticorrelated with Na and Al • Polluting stars have M > 3.5MSolar Smith et al. (2005)

19. Fluorine in Asymptotic Giant Branch Carbon Stars Abia et al. (2010)

20. Fluorine in Asymptotic Giant Branch Carbon Stars Abia et al. (2010) ●N▲ J ○ M (Tc)■SC

21. Elemental Abundances: C/O and 12C/13C in early AGB stars Smith & Lambert (1990)

22. Elemental Abundances: CNO and Carbon stars Lambert et al. (1986)

23. Very H-poor and He-rich • Unpredictable declines – R CrBs • Abundance as a means to test • - origins • - links to HdC (cooler) and EHe (hotter) stars • Simple spectroscopic test? • - continuous opacity from photoionization of • neutral carbon • - many excited lines of neutral carbon • - predict strength of C I lines independent of • “everything” Enjoying the surprises: R CrB stars

25. The Carbon Problem for RCBs • Spectrum rich in excited CI lines • Continuous opacity = photoionization of C  CI line strength is independent of “everything” • Yes — that’s so, but lines are a factor of 4 weaker than predicted. • All proposed solutions failed except an ad hoc adjustment to the atmosphere • Investigate IR spectrum: exploit the wavelength dependent continuous opacity

26. Rao & Lambert (2008)

27. Enjoying the surprises: 18O in HdC stars Clayton et al. (2005)

28. 18O in HdC and RCB stars Garcia-Hernandez et al. (2010)

29. IGRINS at the McDonald Observatory Tackle key problems in stellar astrophysics • Globular cluster giant branches • Field giants and first dredge-up: Oxygen isotopes • RCBs - carbon problem - spectra in decline • Tests of atmospheric models – giants and supergiants - radial velocity of atoms and molecules - optical and IR line intensities

30. Forward to GMTNIRS!