Rotation, Activity and Lithium Depletion in the Hyades Late Main Sequence

Author(s):  
R. Rebolo ◽  
J. E. Beckman
1988 ◽  
Vol 132 ◽  
pp. 469-472
Author(s):  
R. Rebolo ◽  
J. E. Beckman

Selecting stars with previously measured or estimated rotational periods we measured Li equivalent widths in 8 stars of the Hyades late main sequence. Combining our data with literature values, we derive a homogeneous set of Li abundances. Plotting log N(Li) against Rossby number we can separate the effects of temperature and rotation. We find for stars later than F8 increased depletion with longer period, at constant surface temperature. Discounting, as improbable, spurious abundances due to surface activity effects, we give a tentative view of the implications of these results for stellar modelling.


2020 ◽  
Vol 500 (1) ◽  
pp. 1158-1177
Author(s):  
R D Jeffries ◽  
R J Jackson ◽  
Qinghui Sun ◽  
Constantine P Deliyannis

ABSTRACT New fibre spectroscopy and radial velocities from the WIYN telescope are used to measure photospheric lithium in 242 high-probability, zero-age main-sequence F- to K-type members of the rich cluster M35. Combining these with published rotation periods, the connection between lithium depletion and rotation is studied in unprecedented detail. At Teff < 5500 K there is a strong relationship between faster rotation and less Li depletion, although with a dispersion larger than measurement uncertainties. Components of photometrically identified binary systems follow the same relationship. A correlation is also established between faster rotation rate (or smaller Rossby number), decreased Li depletion and larger stellar radius at a given Teff. These results support models where star-spots and interior magnetic fields lead to inflated radii and reduced Li depletion during the pre-main-sequence (PMS) phase for the fastest rotators. However, the data are also consistent with the idea that all stars suffered lower levels of Li depletion than predicted by standard PMS models, perhaps because of deficiencies in those models or because saturated levels of magnetic activity suppress Li depletion equally in PMS stars of similar Teff regardless of rotation rate, and that slower rotators subsequently experience more mixing and post-PMS Li depletion.


2008 ◽  
Vol 4 (S258) ◽  
pp. 81-94 ◽  
Author(s):  
Lynne A. Hillenbrand

AbstractThis overview summarizes the age dating methods available for young sub-solar mass stars. Pre-main sequence age diagnostics include the Hertzsprung-Russell (HR) diagram, spectroscopic surface gravity indicators, and lithium depletion; asteroseismology is also showing recent promise. Near and beyond the zero-age main sequence, rotation period or vsiniand activity (coronal and chromospheric) diagnostics along with lithium depletion serve as age proxies. Other authors in this volume present more detail in each of the aforementioned areas. Herein, I focus on pre-main sequence HR diagrams and address the questions: Do empirical young cluster isochrones match theoretical isochrones? Do isochrones predict stellar ages consistent with those derived via other independent techniques? Do the observed apparent luminosity spreads at constant effective temperature correspond to true age spreads? While definitive answers to these questions are not provided, some methods of progression are outlined.


1989 ◽  
Vol 98 ◽  
pp. 1451 ◽  
Author(s):  
Don A. Vandenberg ◽  
Helena E. Poll

1976 ◽  
Vol 204 ◽  
pp. 481 ◽  
Author(s):  
J. M. Straus ◽  
J. B. Blake ◽  
D. N. Schramm

Author(s):  
Da-run Xiong

A non-local and time-dependent theory of convection was briefly described. This theory was used to calculate the structure of solar convection zones, the evolution of massive stars, lithium depletion in the atmosphere of the Sun and late-type dwarfs, and stellar oscillations (in Part Ⅱ). The results show that: 1) the theoretical turbulent velocity and temperature fields in the atmosphere and the thermal structure of the convective envelope of the Sun agree with the observations and inferences from helioseismic inversion very well. 2) The so-called semi-convection contradiction in the evolutionary calculations of massive stars was removed automatically, as predicted by us. The theoretical evolution tracks of massive stars run at higher luminosity and the main sequence band becomes noticeably wider in comparison with those calculated using the local mixing-length theory (MLT). This means that the evolutionary mass for a given luminosity was overestimated and the width of the main sequence band was underestimated by the local MLT, which may be part of the reason for the contradiction between the evolutionary and pulsational masses of Cepheid variables and the contradiction between theoretical and observed distributions of luminous stars in the H-R diagram. 3) The predicted lithium depletion, in general, agrees well with the observation of the Sun and Galactic open clusters of different ages. 4) Our theoretical results for non-adiabatic oscillations are in good agreement with the observed mode instability from classic variables of high-luminosity red giants. Almost all the instability strips of the classical pulsating variables (including the Cepheid, δ Scuti, γ Doradus, βCephei, and SPB strips) were reproduced (Part Ⅱ).


2003 ◽  
Vol 412 (1) ◽  
pp. 213-218 ◽  
Author(s):  
F. D'Antona ◽  
J. Montalbán

2002 ◽  
Vol 581 (1) ◽  
pp. L43-L46 ◽  
Author(s):  
Inseok Song ◽  
M. S. Bessell ◽  
B. Zuckerman

2015 ◽  
Vol 10 (S314) ◽  
pp. 91-94
Author(s):  
Garrett Somers ◽  
Marc H. Pinsonneault

AbstractWe investigate the impact of starspots on the evolution of late-type stars during the pre-main sequence (pre-MS). We find that heavy spot coverage increases the radii of stars by 4–10%, consistent with inflation factors in eclipsing binary systems, and suppresses the rate of pre-MS lithium depletion, leading to a dispersion in zero-age MS Li abundance (comparable to observed spreads) if a range of spot properties exist within clusters from 3-10 Myr. This concordance with data implies that spots induce a range of radii at fixed mass during the pre-MS. These spots decrease the luminosity and Teff of stars, leading to a displacement on the HR diagram. This displacement causes isochrone derived masses and ages to be systematically under-estimated, and can lead to the spurious appearance of an age spread in a co-eval population.


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