Stellar Ashes or Planetary Debris: Studying Light Element Abundances in Red Giant Atmospheres Joleen Carlberg July 12, 2017 Abstract: The light elements Li, Be, and B are generally very depleted in red giant atmospheres, as is expected from the relatively low temperatures at which they are destroyed in stellar interiors and the deep mixing that takes place when stars being their ascent up the red giant branch. Nevertheless, red giants with atmospheres enriched in lithium are well known. Is this Li stellar ash dredged up from even deeper layers in the star, or is it debris from a giant planet that once orbited the star? Beryllium is expected to be enhanced in the latter scenario, but not in the former. In this talk, I will present preliminary results on a project to measure Be in a small sample of Li-rich red giant stars.

Outline Background: Beryllium: Changes in light element abundances (Li, Be, B) during stellar evolution The Li-rich red giant phenomenon Beryllium: Why it’s important Why it’s hard to measure Preliminary results

Background We tend to think of fusion occurring in stellar cores Li, Be, and B all efficiently “burn” at relatively cool temperatures  surface abundance changes Going to talk about LI for a bit, b/c it’s easiest burned, most abundant initially, easiest to observe What stage of is my plot Cunha and Smith 1999 has the temperatures Li burns at 2.5 MK Be: 3.5 MK B: 5 MK

Background First dredge-up (FDU): dilutes surface Li, Be, B 13C dredge-up  reduced surface 12C/13C CORE INTERMEDIATE CONVECTIVE ENVELOPE RED GIANT Li/Be/B pockets – size dependent on M★, rotation, [Fe/H]… SUN

Background Most red giants should be (and are) depleted in Li. What happened in the ones that are Li-rich? Sun (present) Li-rich Meteorites/young sun Going to talk about LI for a bit, b/c it’s easiest burned, most abundant initially, easiest to observe What stage of is my plot Cunha and Smith 1999 has the temperatures Li burns at 2.5 MK Be: 3.5 MK B: 5 MK A(Li) = log(NLi/NH) + 12 Data: de Medeiros+ 2000, Carlberg+ 2012

Are Li-rich red giants planet eaters? γ ν e- 3He 4He 7Be 7Li or

The Beryllium Test No change in 12C/13C 12C/13C reduced

The Beryllium Test: Selecting Stars Evidence of deep mixing Too Li rich(for engulfment) Clearly Li enriched Engulfment “sweet spot” Previous Be non-detections (Melo et al 2005; Takeda & Tajitsu 2017) What is Li/Si? Stuff in box can be donw with BDs into a 0.8 M_sun envelope or planets into a 0.1 M_sun envelope Stuff in circle, hard to explain with engulfment even if BD into a 0.1 M_sun envelope Melo et al A(Li) 12C/13C # in T17 HD 787 1.8 9 20 HD 19745 4.1 16 X HD 30238 0.8 26 X HD 39853 2.8 6 X HD 95799 3.2 10 X HD 176588 1.1 ?? X HD 183492 2.0 9 11 ---------------------------------------------- HD 217352 HD 219025 T17 did 18 unique new ones NAME A(LI) 12C/13C/ HD 174104 3.17 missing? HD 21018 2.93 ?? HD 203136 2.40 ?? ON PLOT HD 232862 2.57 9 HD 212430 1.94 ?? ON PLOT KIC 9821622 1.85 18 HD 12203 2.12 7.5 ON PLOT HD 194937 3.15 ?? ON PLOT HD 8676 3.81 5 HD 167304 2.79 7.5 ON PLOT HD 214995 3.06 13 PDS 100 2.59 9 HD 6665 2.80 ?? HD 9746 3.73 24 HD 30834 2.63 13 HD 205379 1.88 Missing? Detections Takeda & Tajitsu 2017 New Subaru HDS observations (Li-rich stars selected from Kumar+ 2011) Data: Carlberg+ 2012, Kumar+ 2011, Gilory 1989

The Beryllium Test: Selecting Stars

Measuring A(X): Be vs. Li Vesta/Sun (Subaru spectrum): various line lists with undepleted Be Li lines Be lines Dmag ~ 2.5 Pollux (STIS spectrum): various line lists with NO Be Teff ~ 4600 K, A(Li) < –0.11 dex Teff ~ 4600 K, A(Li) = +1.56 dex Carlberg+ 2017, in prep

Measuring A(Be): “By hand” analysis – adjust parameters interactively in MOOG Semi-automated analysis: Amoeba Fitter with different free parameters. All runs fit the overall scale, plus fit abundances of: Be Be/C/O Be/Ti Be/C/O/Ti Visually inspect to select best fits…

Measuring A(Be):

Preliminary Results Engulfment prediction FDU prediction A(Be) is… < FDU predictions for low 12C/13C for normal 12C/13C, > FDU predictions < engulfment predictions for unknown 12C/13C, ≈ FDU for one > engulfment for other  post engulfment Li burning? 12C/13C normal 12C/13C low 12C/13C unknown T17, 12C/13C ◯ unknown, ⬤ low NAME A(LI) 12C/13C/ HD 194937 3.15 ?? ON PLOT HD 167304 2.79 7.5 ON PLOT HD 203136 2.40 ?? ON PLOT HD 12203 2.12 7.5 ON PLOT HD 212430 1.94 ?? ON PLOT

Comparison to previous results: Our presumed engulfment A(Be) is within distribution seen in Li-normal stars Due to line list difference? Due to sample differences? Evidence of post-engulfment Li-burning? Takeda & Tajitsu (2014 – Li normal, 2017 – Li-rich)

Summary: Selected sample of Li-rich stars with (mostly) known 12C/13C Using a newly created spectral line list, measured A(Be) in 8 Li- rich stars Stars for which we have strongest suspicion of planet engulfment do have largest A(Be) Observed Be enhancement is generally lower than expected One Be enhancement is much higher than expected  was star previously more Li-rich? Future: Well defined error bars Tailor engulfment predictions to each star Investigate biases between this sample and literature sample

EXTRA

Pollux (STIS spectrum): various line lists with NO Be

Preliminary Results

The Beryllium Test Too Li rich(for engulfment) Engulfment “sweet spot” Evidence of deep mixing Too Li rich(for engulfment) Clearly Li enriched Engulfment “sweet spot” Previous Be non-detections (Melo et al 2005); Takeda & Tajitsu 2017 What is Li/Si? Stuff in box can be donw with BDs into a 0.8 M_sun envelope or planets into a 0.1 M_sun envelope Stuff in circle, hard to explain with engulfment even if BD into a 0.1 M_sun envelope Melo et al A(Li) 12C/13C # in T17 HD 787 1.8 9 20 HD 19745 4.1 16 X HD 30238 0.8 26 X HD 39853 2.8 6 X HD 95799 3.2 10 X HD 176588 1.1 ?? X HD 183492 2.0 9 11 ---------------------------------------------- HD 217352 HD 219025 T17 did 18 unique new ones NAME A(LI) 12C/13C/ HD 174104 3.17 missing? HD 21018 2.93 ?? HD 203136 2.40 ?? ON PLOT HD 232862 2.57 9 HD 212430 1.94 ?? ON PLOT KIC 9821622 1.85 18 HD 12203 2.12 7.5 ON PLOT HD 194937 3.15 ?? ON PLOT HD 8676 3.81 5 HD 167304 2.79 7.5 ON PLOT HD 214995 3.06 13 PDS 100 2.59 9 HD 6665 2.80 ?? HD 9746 3.73 24 HD 30834 2.63 13 HD 205379 1.88 Missing? New observations of Li-rich stars (selected from Kumar et al 2011)