: 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)
Outline * Starter/Welcome drink - problems: General Introduction * Main course/lunch box - Origin of Li anomaly in K giants * Bill - Issues with planet engulfment scenario
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 2.5 10 6 K I Isotope - 6 Li
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?
Evolution of Li in the Universe Primordial Li P 2.72 0.06 Cyburt 2008 Primordial Li O 2.27 0.03 Lind 2009 Age of Universe 13.7 0.13 Gyr WMAP 13.8 1.1 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
Galactic Li enrichment I Li got enriched in the universe!
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)
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 3 2 1 1.8 1.6 1.4 1.2 1 0.8 0.6 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)
Li-rich K giants (LRKG): Under 1% of RGB stars I A(Li) > 1.4 - Li-rich, A(Li) 3.3 - Super Li-rich I First LRKG - HD 112127 - A(Li) = 2.7 - 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)
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
Li Preservation - Unlikely - Ruled out! 1 HD 10437 0.5 2 0 HD 77361 HD 8676-0.5 6707 6707.5 6708 6708.5 1.5 HD 77361 1 0.5 1 HD 19745 0 HD 19745 0.5-0.5 6707 6707.5 6708 6708.5 8002 8003 8004 8005 Super Li-rich (A(Li) > 3.3) and 12 C/ 13 C 3.5?? Bharat Kumar & Reddy, 2009
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
RGB Bump and/or Red Clump: Li at Core He-Flash? 3 3 2.5 2.5 2 2 1.5 1.5 1 1 [Fe/H] = 0.0 [Fe/H] = 0.0 0.5 0.5 5500 5000 4500 4000 5500 5000 4500 4000 Sample: 2000 (blue: Our survey) + 644 (Green:Brown et al. 1989) Li-rich Giants: Blue (Our survey)+ Green (Brown1989)+ Magenta(others) Bharat Kumar, Reddy & Lambert, 2011
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 2.5 2 I Tracks computed for solar metallicity, [Fe/H] = 0.0 1.5 1 0.5 5500 5000 4500 4000
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
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)
RGB Bump and Red Clump 0.5 0 3-0.5 2-1 -1.5 1 [Fe/H] = 0.0, -0.3-1 -0.5 0 0.5 5000 4000 3000 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
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!
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
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
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. 2002 and Ghezzi et al. 2009 I Enhanced Li and rapid rotation due to engulfment of giant planet - Carlberg et al (2012)
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 1 2.5 0.8 2 0.6 1.5 0.4 1 0.2 0.5 5200 5000 4800 4600 4400 4200 0 6707 6707.5 6708 6708.5 No Direct Evidence...Unlikely!
Li vs Vsini Vs 12 C/ 13 C: Ongoing Work 10 Rotational Velocity Distribution among Li-rich Giants All 4 8 3 2 Number of 6 4 2 0 0 5 10 15 20 25 30 35 40 Vsini 1 1 2 3 4 5 A(Li) 40 30 20 10 0 1 2 3 4 5 A(Li) 30 20 10 No Direct Corelation! 0 1 2 3 4 5 A(Li) Continue...
Evolution of Rotational velocity: Ongoing work
Thanks for your Attention