The Gaia-ESO Survey: A lithium-rotation connection at 5 Myr?

Context. The evolution of lithium abundance in cool dwarfs provides a unique probe of nonstandard processes in stellar evolution. Aims. We investigate the lithium content of young low-mass stars in the 5 Myr old, star forming region NGC 2264 and its relationship with rotation. Methods. We combine lithium equivalent width measurements (EW(Li)) from the Gaia-ESO Survey with the determination of rotational periods from the CSI 2264 survey. We only consider bona fide nonaccreting cluster members to minimize the uncertainties on EW(Li). Results. We report the existence of a relationship between lithium content and rotation in NGC 2264 at an age of 5 Myr. The Li-rotation connection is seen over a restricted temperature range (T_(eff) = 3800–4400 K), where fast rotators are Li-rich compared to slow rotators. This correlation is similar to, albeit of lower amplitude than, the Li-rotation connection previously reported for K dwarfs in the 125 Myr old Pleiades cluster. We investigate whether the nonstandard pre-main-sequence models developed so far to explain the Pleiades results, which are based on episodic accretion, pre-main-sequence, core-envelope decoupling, and/or radius inflation due to enhanced magnetic activity, can account for early development of the Li-rotation connection. While radius inflation appears to be the most promising possibility, each of these models has issues. We therefore also discuss external causes that might operate during the first few Myr of pre-main-sequence evolution, such as planet engulfment and/or steady disk accretion, as possible candidates for the common origin for Li excess and fast rotation in young low-mass pre-main-sequence stars. Conclusions. The emergence of a connection between lithium content and rotation rate at such an early age as 5 Myr suggests a complex link between accretion processes, early angular momentum evolution, and possibly planet formation, which likely impacts early stellar evolution and has yet to be fully deciphered.

[1]  P. Stetson,et al.  DAOSPEC: An Automatic Code for Measuring Equivalent Widths in High-Resolution Stellar Spectra , 2008, 0811.2932.

[2]  M. Pinsonneault,et al.  Rotation of low-mass stars - A new probe of stellar evolution , 1990 .

[3]  F. Gallet,et al.  Improved angular momentum evolution model for solar-like stars , 2013, 1306.2130.

[4]  William H. Press,et al.  Book-Review - Numerical Recipes in Pascal - the Art of Scientific Computing , 1989 .

[5]  R. Jayawardhana,et al.  Spectroscopy of very low mass stars and brown dwarfs in the Lambda Orionis star forming region I. Enlarging the census down to the planetary mass domain in Collinder 69 , 2011, 1109.4917.

[6]  Gottingen,et al.  CAN WE PREDICT THE GLOBAL MAGNETIC TOPOLOGY OF A PRE-MAIN-SEQUENCE STAR FROM ITS POSITION IN THE HERTZSPRUNG–RUSSELL DIAGRAM? , 2012, 1206.5238.

[7]  P. Denissenkov.  A MODEL OF MAGNETIC BRAKING OF SOLAR ROTATION THAT SATISFIES OBSERVATIONAL CONSTRAINTS , 2010, 1002.2261.

[8]  P. Bonifacio,et al.  Solar twins in M67 , 2008, 0807.0092.

[9]  F. Allard,et al.  New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit , 2015, 1503.04107.

[10]  D. Lambert,et al.  Lithium Abundances in the alpha Per Cluster , 2010, 1009.2323.

[11]  R. Makidon,et al.  Periodic Variability of Pre-Main-Sequence Stars in the NGC 2264 OB Association , 2004 .

[12]  N. Pizzolato,et al.  Dependence of coronal X-ray emission on spot-induced brightness variations in cool main sequence stars , 2003 .

[13]  Garrett Somers,et al.  Rotation, inflation, and lithium in the Pleiades , 2014, 1410.4238.

[14]  S. Vauclair,et al.  METAL-RICH ACCRETION AND THERMOHALINE INSTABILITIES IN EXOPLANET-HOST STARS: CONSEQUENCES ON THE LIGHT ELEMENTS ABUNDANCES , 2011, 1109.4238.

[15]  J. Bouvier,et al.  Protostellar spin-down: a planetary lift? , 2015, 1509.02951.

[16]  A rotational and variability study of a large sample of PMS stars in NGC 2264 , 2004, astro-ph/0402188.

[17]  H. M. Günther,et al.  CSI 2264: SIMULTANEOUS OPTICAL AND INFRARED LIGHT CURVES OF YOUNG DISK-BEARING STARS IN NGC 2264 WITH CoRoT and SPITZER—EVIDENCE FOR MULTIPLE ORIGINS OF VARIABILITY , 2014, 1401.6582.

[18]  R. P. Butler,et al.  OBLIQUITIES OF HOT JUPITER HOST STARS: EVIDENCE FOR TIDAL INTERACTIONS AND PRIMORDIAL MISALIGNMENTS , 2012, 1206.6105.

[19]  John R. Stauffer,et al.  The evolution of the lithium abundances of solar-type stars. III - The Pleiades , 1993 .

[20]  É. Bolmont,et al.  Effect of the stellar spin history on the tidal evolution of close-in planets , 2012, 1207.2127.

[21]  G. Micela,et al.  Mapping accretion and its variability in the young open cluster NGC 2264: a study based on u-band photometry , 2014, 1408.0432.

[22]  Sofia Randich,et al.  Time scales of Li evolution: A Homogeneous analysis of open clusters from ZAMS to late-MS , 2005 .

[23]  R. Jeffries.  Using rotation, magnetic activity and lithium to estimate the ages of low mass stars , 2014, 1404.7156.

[24]  S. Sciortino,et al.  Supersaturation and activity-rotation relation in PMS stars: the young cluster h Persei , 2016, 1602.03696.

[25]  D. Soderblom,et al.  Evolution Of The Lithium Abundances Of Solar-Type Stars. IX. High-Resolution Spectroscopy of Low-Mass Stars in NGC 2264 , 1999 .

[26]  F. Palla,et al.  Age Spreads in Star-forming Regions: The Lithium Test in the Orion Nebula Cluster , 2005 .

[27]  F. Gallet,et al.  Improved angular momentum evolution model for solar-like stars II. Exploring the mass dependence , 2015, 1502.05801.

[28]  Gilles Chabrier,et al.  Evolution of low-mass star and brown dwarf eclipsing binaries , 2007, 0707.1792.

[29]  T. Naylor,et al.  Fitting the young main-sequence: distances, ages and age spreads , 2008, 0801.4085.

[30]  M. Pinsonneault,et al.  A TALE OF TWO ANOMALIES: DEPLETION, DISPERSION, AND THE CONNECTION BETWEEN THE STELLAR LITHIUM SPREAD AND INFLATED RADII ON THE PRE-MAIN SEQUENCE , 2014, 1402.6333.

[31]  J. Bouvier.  Lithium depletion and the rotational history of exoplanet host stars , 2008, 0808.3917.

[32]  M. Asplund,et al.  Departures from LTE for neutral Li in late-type stars , 2009, 0906.0899.

[33]  S. Turck-chièze,et al.  Lithium Depletion in Pre-Main-Sequence Solar-like Stars , 2001, astro-ph/0111223.

[34]  S. Littlefair,et al.  Pre-main-sequence isochrones - II. Revising star and planet formation time-scales , 2013, 1306.3237.

[35]  S. Solanki,et al.  Toroidal versus poloidal magnetic fields in Sun-like stars: a rotation threshold , 2008, 0804.1290.

[36]  J. Valenti,et al.  Spectroscopy Made Easy: A New Tool for Fitting Observations with Synthetic Spectra , 1996 .

[37]  F. Ménard,et al.  Magnetospheric accretion on the fully convective classical T Tauri star DN Tau , 2013, 1308.5143.

[38]  F. Favata,et al.  CoRoT ? 223992193: A new, low-mass, pre-main sequence eclipsing binary with evidence of a circumbinary disk , 2013, 1311.3990.

[39]  J. Innis,et al.  The Variation of Lithium Equivalent Width in Active Cool Stars , 1986, Publications of the Astronomical Society of Australia.

[40]  J. Bouvier,et al.  Investigating the rotational evolution of young, low mass stars using Monte Carlo simulations , 2015, 1504.04717.

[41]  C. Aerts,et al.  Echography of young stars reveals their evolution , 2014, Science.

[42]  J. D. Medeiros,et al.  Rotation and lithium abundance of solar-analog stars. Theoretical analysis of observations , 2010, 1006.3861.

[43]  F. Favata,et al.  Rotation in NGC 2264: a study based on CoRoT photometric observations , 2013, 1301.1856.

[44]  R. P. Butler,et al.  The Pleiades Rapid Rotators: Evidence for an Evolutionary Sequence , 1987 .

[45]  M. Giampapa.  Lithium abundances and chromospheric activity. I: Empirical results , 1984 .

[46]  G. Meynet,et al.  Impact of rotation and disc lifetime on pre-main sequence lithium depletion of solar-type stars , 2012, 1207.0372.

[47]  Sergey E. Koposov,et al.  The Gaia-ESO Survey: Kinematic structure in the Gamma Velorum cluster , 2014, 1401.4979.

[48]  Sergio Ortolani,et al.  The Gaia-ESO Public Spectroscopic Survey , 2012 .

[49]  T. Naylor,et al.  No evidence for intense, cold accretion on to YSOs from measurements of Li in T-Tauri stars , 2013, 1306.2282.

[50]  G. Chabrier,et al.  Effect of episodic accretion on the structure and the lithium depletion of low-mass stars and planet-hosting stars , 2010, 1008.4288.

[51]  M. Pinsonneault,et al.  Evolutionary models of the rotating sun , 1989 .

[52]  C. Charbonnel,et al.  Hydrodynamical stellar models including rotation, internal gravity waves, and atomic diffusion - I. Formalism and tests on Pop I dwarfs , 2005 .

[53]  C. Babusiaux,et al.  Gaia-ESO Survey: Analysis of pre-main sequence stellar spectra , 2015, 1501.04450.

[54]  C. Prieto,et al.  LITHIUM ABUNDANCES IN NEARBY FGK DWARF AND SUBGIANT STARS: INTERNAL DESTRUCTION, GALACTIC CHEMICAL EVOLUTION, AND EXOPLANETS , 2012, 1207.0499.

[55]  G. Carraro,et al.  The Gaia-ESO Survey: Stellar radii in the young open clusters NGC 2264, NGC 2547 and NGC 2516 , 2015, 1511.06900.

[56]  J. Landstreet,et al.  Magnetic Fields of Nondegenerate Stars , 2009, 0904.1938.

[57]  R. Jeffries.  On the lithium abundance dispersion in late-type Pleiades stars , 1999, astro-ph/9906189.