1. Early Galactic Nucleosynthesis: The Impact of HST/STIS Spectra of Metal-Poor Stars Chris Sneden University of Texas

2. A Very Collaborative Effort John Cowan Jim Truran Scott Burles Tim Beers Jim Lawler Inese Ivans Jennifer Simmerer Caty Pilachowski Jennifer Sobeck Betsy den Hartog David Lai Scott Burles George Fuller Anna Frebel Bob Kraft Angela Bragaglia Norbert Christlieb Beatriz Barbuy Anna Marino Raffaele Gratton Jennifer Johnson George Preston Debra Burris Bernd Pfeiffer Eugenio Carretta Jackson Doll Karl-Ludwig Kratz Francesca Primas Sara Lucatello Taft Armandroff Andy McWilliam Roberto Gallino Evan Kirby Vanessa Hill Ian Roederer Christian Johnson Sloane Simmons Valentina D’Orazi Ian Thompson Matt Alvarez Definitions: [A/B] = log 10 (N A /N B ) star – log 10 (N A /N B ) Sun log ε(A) = log 10 (N A /N H ) + 12.0 (spectroscopic) log N(A) = log 10 (N A /N Si ) + 6.0 (meteoritic)

3. today two topics: - the neutron-capture elements - return to the Fe-peak the common thread: nucleosynthesis at the end of stellar lives

4. HST/STIS spectra: relevant to entire nuclide range Heaviest stable elements a.k.a 3 rd neutron-capture peak Understudied lighter neutron-capture elements Fe-group elements Light elements (Be, B) http://atom.kaeri.re.kr/

5. The ultimate question? How did our Galaxy produce the solar chemical composition? SCG08 = Sneden, Cowan, & Gallino 2008, ARA&A, 46, 241

6. Most isotopes of elements with Z>30 are formed by: A Z + n A+1 Z Followed by, for unstable nuclei: A+1 Z A+1 (Z+1) +  - RbSrYZrNbMoTcRuRhPdAgCdInSnSbTeI ScCaK Xe TiVCrMnFeCoNiCuZnGaGeAsSeBrKr H BeLi Mg Na HfTaWReOsIrPtAuHgTlPbBiPoAtRn RaFr BaCs RfDbSgBhHsMtUunUuuUub CBOFNe ArAlSiPSCl N He LaCePrNdPmSmEuGdTbDyHoErTmYbLu AcThPaUNpPuAmCmBkCfEsFmMdNoLr First discussion: n(eutron)-capture elements

7. s-process: β-decays occur between successive n-captures r-process: rapid, short-lived neutron blast temporarily overwhelms β-decay rates r- or s-process element: origin in solar-system dominated by one or the other process Rolfs & Rodney (1988) Buildup of n-capture elements

8. A detailed look at the r- and s-process paths SCG08 “s-process” element “r-process” element

9. n-capture spectra of metal-poor stars HD 122563: [Fe/H] = -2.7 T eff ~ 4750 LOW n-capture CS 22892-052: [Fe/H] = -3.1 T eff ~ 4750 HIGH n-capture

10. “r-process-rich” metal-poor stars first example, HD 115444, was reported by Griffin et al. 1982 SCG08 An important abundance ratio: log  (La/Eu) = +0.6 (solar total) = +0.2 (solar r-only) = +1.5 (solar s-only)

11. HfBa LaCePrNdPmSmEuGdTbDyHoErTmYbLu Wisconsin lab studies: log gf and hyperfine/isotopic structure Lawler et al. 2000a Lawler et al. 2001 Lawler et al. 2000b Lawler et al. 2004 Lawler et al. 2006 Lawler et al. 2007 Lawler et al. 2008 Den Hartog et al. 2003 Lawler et al. 2009 Sneden et al. 2009 14 36 14 20 2 13 3 8 3 1 1 4 45 5 46 Sun: # transitions used in analysis 15 32 15 4 7 29 13 21 6 1 8 37 55 9 32 CS 22892-052 : # transitions used in analysis why are rare earths well understood? (unstable element)(well studied in literature)

12. n-capture compositions of well- studied r-rich stars: Così fan tutte?? SCG08 lines are solar-system abundances differences from solar-system means of the differences

13. Thorium/Uranium detections promise alternate Galactic ages Frebel et al. 2007

14. leading to possible radioactive decay ages U/Th ratio should be best age indicator, if both elements can be detected reliably Persistent question: why is Pb usually low? Frebel et al. 2007

15. good abundances really confront r-process predictions Ivans et al. 2006

16. But! crucial element groups for further progress Ivans et al. 2006

17. Johnson & Bolte 2002 Beyond simplest results: de-coupling of the heavy/light r-process elements See also Aoki et al. 2005, 2007 Z Y = 39 Z Ba = 56

18. r-process abundance distribution variations: "normal" Roederer et al 2010

19. But various densities must contribute to r-process Kratz et al. 2007 increasing density componentsdecreasing density components

20. Niobium (Nb, Z=41): surrogate for remaining n-capture elements (and their “issues”) these are the best transitions in the most favorable detection cases Nilsson et al. 2010

21. All reasonably strong lines are in the vacuum UV; this is why STIS is good here Niobium: here is why there are difficulties Nilsson et al. 2010

22. UV spectra of 3 metal-poor giants Roederer et al 2010 HD 122563: [Fe/H] = -2.7 T eff ~ 4750 LOW n-capture HD 115444: [Fe/H] = -2.9 T eff ~ 4650 HIGH n-capture BD+17 3248 [Fe/H] = -2.2 T eff ~ 5200 HIGH n-capture

23. Initial STIS exploration HD 122563: [Fe/H] = -2.7 T eff ~ 4750 LOW n-capture HD 115444: [Fe/H] = -2.9 T eff ~ 4650 HIGH n-capture CS 22892-052 [Fe/H] = -3.1 T eff ~ 4750 HIGH n-capture Cowan et al. 2005

24. Heaviest stable elements scale with Eu Cowan et al. 2005 Again, Eu is the usual “pure” r-process element

25. But light n-capture elements do NOT scale with Eu Cowan et al. 2005

26. Upon further review of these same STIS data … Roederer et al 2010 Points = data Lines = syntheses: best fit (color) ± 0.3dex (dotted) no element (solid)

27. Helps “complete” the n-capture distribution Roederer et al 2010 Points = observations Blue line = SN ν wind Farouqi et al. 2009 Gray lines = scaled solar-system

28. Second discussion: back to the Fe-peak McWilliam 1997

29. sharpening & extension by “First Stars” group Cayrel et al. 2004

30. elements that can be directly predicted in SNe models Kobayashi et al. 2006 (following Timmes et al. 1995) crucial distinction from n-capture elements: the Fe-peak element productions can actually be predicted theoretically

31. for some elements, all seems well Kobayashi et al. 2006 (solid line new results

32. but for others, discomfort Kobayashi et al. 2006 neutral lines ionized lines same predicted Cr abundances

33. should be simple to do Fe-peak elements: their abundances >> n-capture ones

34. Fe-peak light n-cap heavy n-cap = rare-earth 3 rd peak, Th α, etc. r-process-rich stars give false impression of # of lines in metal-poor abundance work! For Fe-peak elements #/species <10 in most cases

35. The reality is grim for metal-poor turnoff stars

36. AND, can you believe ANY past analysis??

37. the outcome for Bergemann et al.?

38. Comparison of low metallicity spectra in the “visible” spectral region

39. a new attack: UV STIS spectra

40. The complex UV spectrum of HD 84937

41. dotted line, no Fe; solid line, best fit dashed lines: ±0.5 dex from best fit red line, perfect agreement; other lines, deviations

42. Why is working in the UV a problem? Opacity competition: metal-poor red giant

43. Opacity competition: metal-poor turnoff star

44. A summary of our results on Fe

45. probable explanation of the abundance “dip”

46. Other Fe-peak elements: a start Or, [Co/Fe] ~ +0.3 from both of these neutral and ionized lines Bergemann 2009: [Co/Fe] = +0.18 (LTE) = +0.66 (NLTE) {probably ~+0.3 (LTE) on our [Fe/H] scale}

47. This rough cobalt estimate is not too bad … the red line is the [Co/Fe] trend with [Fe/H] derived by the “first stars” group (Cayrel et al. 2004) HD 84937

48. work on Cr I and Cr II is underway Matt Alvarez, Chris Sneden (UT), Jennifer Sobeck (U Chicago), Betsy den Hartog, Jim Lawler (U Wisconsin)

49. Summary: metal-poor stars hold keys to understanding Galactic nucleosynthesis Atomic physics dictates “non-standard” wavelengths for some elements STIS in the vacuum UV is the only choice for some poorly understood element regimes neutron-capture elements: observers are in the lead! STIS is crucial for both lightest and heaviest stable elements Fe-peak elements: theorists are in the lead! No sane person should believe Fe-peak abundances right now but STIS data hold promise for the near-future