Origin of Li Anomaly in K giants. Planet engulfment scenario plays role? Bharat Kumar Yerra. Lunch Talk, 22nd October 2014

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1 : Planet engulfment scenario plays role? Stellar Abundances & Galactic Evolution Group NAOC, Beijing Lunch Talk, 22nd October 2014 Collaborators: Dr. B. Eswar Reddy (IIAP, Bangalore, India) Dr. David L. Lambert (McDonald Observatory, USA) Dr. Gang Zhao (NAOC, China)

2 Outline * Starter/Welcome drink - problems: General Introduction * Main course/lunch box - Origin of Li anomaly in K giants * Bill - Issues with planet engulfment scenario

3 is Fragile! I Product of Big-Bang Nucleosynthesis (D, 3 He, 4 He, 7 Li) I Production in stars - 3 He(,) 7 Be(e,) 7 Li - Cameron Fowler mechanism I Fragile element, destroys at K I Isotope - 6 Li

4 Primordial Li Discrepancy I Diusion I Pre-mainsequence depletion I Mainsequence depletion I Still primordial Li to be detected in rst stars I SBBN value may be revised I 6 Li contribution?

5 Evolution of Li in the Universe Primordial Li P Cyburt 2008 Primordial Li O Lind 2009 Age of Universe Gyr WMAP Gyr Gratton 2003 Turn-o stars 3.20 Lambert & Reddy 2004 ISM 3.25 Knauth 2000;2003 Meteroitic 3.28 Lodders 2003 A(Li) = log(li/h)+12

6 Galactic Li enrichment I Li got enriched in the universe!

7 Possible Contributors for Galactic Li: I Galactic Cosmic Rays : Spallation reactions I Supernovae : Explosion of end stage of high and intermediate mass stars I Novae: Explosion of the end stage of low-mass stars I Asymptotic Giant Branch (AGB) Stars : Cameron-Fowler Mechanism + Hot bottom burning + Stellar winds & Massloss I Red Giant Branch (RGB) Stars : high Li (A(Li) 4.0 dex) origin is still debate + Massloss not well understood Ref: Matteucci (2010)

8 Li in RGB stars I Pre-main sequence depletion (< 1.0 M) - observed in open clusters I Mainsequence depletion (< 2.0 M) - observed in sun, open clusters I Post-main sequence depletion: Deepening convective envelope dilutes the surface Li of giants - Observed in G- and K- giants I Expected on K giants - A(Li) 1.4 Ref: Iben (1967)

9 Li-rich K giants (LRKG): Under 1% of RGB stars I A(Li) > Li-rich, A(Li) Super Li-rich I First LRKG - HD A(Li) = Wallerstein and Sneden (1982) I Solar Neighbourhood - Brown et al (1989) (7/644), Bharat Kumar et al (2011) (15/2000) I Thick disk - Monaco et al (2011) (5/824) I Halo - RAVE survey - Ruchti et al (2011) (8/700) I Bulge - Gonzalez et al (2009) (6/400), Lebzelter et al (2012) (3/401) I Milky way satellite galaxies - Kirby et al (2012) (14/2054) I SDSS - Martell et al (2013) (23/8535) I Stars for planet search - Liu et al (2014) (3/378), Adamow et al (2014) (7/1000) I Carlberg et al. - Open Clusters (ongoing) I Kirby et al. - Globular Clusters (ongoing) I LAMOST - Our group (ongoing)

10 Suggestions for Origin of Li enhancement I Preservation of initial lithium I External scenario - Planet or brown dwarf engulfment I Internal scenario - Nucleosynthesis and convective extra mixing I Extra Mixing - Structural changes of star during evolution and/or triggers due to engulfment of external objects

11 Li Preservation - Unlikely - Ruled out! 1 HD HD HD HD HD HD Super Li-rich (A(Li) > 3.3) and 12 C/ 13 C 3.5?? Bharat Kumar & Reddy, 2009

12 Nucleosynthesis & Stellar mixing Charbonnel & Balachandran (2000) Li-rich K giants at RGB Bump I Palacios (2001) Li-Flash mechanism based on rotation induced mixing explained Li production during RGB Bump

13 RGB Bump and/or Red Clump: Li at Core He-Flash? [Fe/H] = 0.0 [Fe/H] = Sample: 2000 (blue: Our survey) (Green:Brown et al. 1989) Li-rich Giants: Blue (Our survey)+ Green (Brown1989)+ Magenta(others) Bharat Kumar, Reddy & Lambert, 2011

14 I Bump - H-burning shell crosses the molecular weight discontinuity, leads to kink on luminosity I Clump - Experiences He-core ash and settles near red horizontal branch with similar He core mass and slight variation in envelope mass I Tracks computed for solar metallicity, [Fe/H] =

15 Not supporting Core-He ash I Black, Green lines - 1.7, 2.2 M tracks I Red line - Bifurcation curves caused by ecient convective heat transport, = 1 (upper), 0.75 (lower) I Cyan line with diamonds: 0.125, 0.25, 0.5 from left to right I Open symbols separated by one million years I Blue stars: KRL (2011) I Red stars: Giant component of RS CVn binaries I Denissenkov (2012) explained that the stars during bump evolution make excursion (Zig-zag motion) towards lower luminosities before resuming their ascents along the RGB

16 Supporting Red Clump: Core-He ash Figure : Kepler core He-burning star (Red) and KRL2011(open symbols) Silva Aguiree et al. (2014) Figure : Super Li-rich giant (blue) occupied red clump of open cluster Trumpler 5 Monaco et al. (2014)

17 RGB Bump and Red Clump [Fe/H] = 0.0, Figure : Li-rich (lled) and Li-normal (open) giants on Far-IR color-color diagram Bharat Kumar et al. (2014) (under review) Figure : Li-rich giants with and without IR excess and Li-normal giants with and without IR excess

18 RGB Bump and Red Clump I Li timescales: 10 4 yrs (Palacios 2001) I Dust evolutionary timescales: 10 5 yrs (Our work) I Bump timescales: 10 6 yrs - Bertelli et al. (2008) I Bump to Clump timescales: 10 7 yrs - Bertelli et al. (2008) I Clump timescales: 10 7 yrs - Bertelli et al. (2008) I Li production at Bump can't survive till clump! I Alternate site to explain clump stars: May be Core-He Flash which may or may not be associated with mass-loss!

19 Nucleosynthesis & Stellar mixing: Summary I Wallerstein & Sneden (1982) discovered Li-rich K giant and suggested Li production and stellar mixing I Brown et al (1989) supported the Li production and stellar mixing I Charbonnel & Balachandran (2000) suggested the Li production is associated with RGB Bump I Bharat Kumar, Reddy, and Lambert (2011) suggested the association of Li-rich giants with Bump and/or Red clump I Silva Augerre et al (2014) and Monoco et al (2014) supported Li-rich K giants with Red clump I Bharat Kumar, Reddy et al. (2014) suggesting Li-rich K giants may be more than one group: RGB Bump and Red Clump

20 Planet Engulfment Scenario I \A Possible source of in the Atmospheres of some Red Giants" by J. B. Alexandar in 1967 * Planets evapourate and then engulfed by host-star while convective envelope expands during RGB evolution * Li-rich material of planets mix with host-star envelopes resulted in enrichment of surface Li abundance I Seiss & Livio (1999) * Planet dissipates at the bottom of convective envelope of host-star after engulfment * Results: Surface Li increases, ejection of mass, stellar metallicity enrichment, spin-up of the star, possible generation of magnetic elds and the related X-ray activity. I Denissenkov & Herwig (2004) I Enhanced extra mixing due to spinning up by an external source of angular momentum- Binary companion or planets or Brown dwarfs

21 Observational Attempts I 6 Li detection: \Evidence for planet engulfment by the star HD82943"- Israelian et al. (2001) in NATURE I Not able to reproduce by Reddy et al and Ghezzi et al I Enhanced Li and rapid rotation due to engulfment of giant planet - Carlberg et al (2012)

22 I Adamow et al. (2014) surveyed Li in stars with and without planets and suggested that planet engulfment scenario is likely than any other scenario for Li production No Direct Evidence...Unlikely!

23 Li vs Vsini Vs 12 C/ 13 C: Ongoing Work 10 Rotational Velocity Distribution among Li-rich Giants All Number of Vsini A(Li) A(Li) No Direct Corelation! A(Li) Continue...

24 Evolution of Rotational velocity: Ongoing work

25 Thanks for your Attention