Behavior of Li abundances in solar-analog stars. II. Evidence of the connection with rotation and stellar activity
Abstract
Context. We previously attempted to ascertain why the Li i 6708 line-strengths of Sun-like stars differ so significantly despite the superficial similarities of stellar parameters. We carried out a comprehensive analysis of 118 solar analogs and reported that a close connection exists between the Li abundance (ALi) and the line-broadening width (vr+m; mainly contributed by rotational effect), which led us to conclude that stellar rotation may be the primary control of the surface Li content.
Aims: To examine our claim in more detail, we study whether the degree of stellar activity exhibits a similar correlation with the Li abundance, which is expected because of the widely believed close connection between rotation and activity.
Methods: We measured the residual flux at the line center of the strong Ca ii 8542 line, r0(8542), known to be a useful index of stellar activity, for all sample stars using newly acquired spectra in this near-IR region. The projected rotational velocity (ve sin i) was estimated by subtracting the macroturbulence contribution from vr+m that we had already established.
Results: A remarkable (positive) correlation was found in the ALi versus (vs.) r0(8542) diagram as well as in both the r0(8542) vs. ve sin i and ALi vs. ve sin i diagrams, as had been expected. With the confirmation of rotation-dependent stellar activity, this clearly shows that the surface Li abundances of these solar analogs progressively decrease as the rotation rate decreases.
Conclusions: Given this observational evidence, we conclude that the depletion of surface Li in solar-type stars, probably caused by effective envelope mixing, operates more efficiently as stellar rotation decelerates. It may be promising to attribute the low-Li tendency of planet-host G dwarfs to their different nature in the stellar angular momentum.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- June 2010
- DOI:
- 10.1051/0004-6361/200913897
- arXiv:
- arXiv:1003.1564
- Bibcode:
- 2010A&A...515A..93T
- Keywords:
-
- stars: abundances;
- stars: activity;
- stars: atmospheres;
- stars: solar-type;
- stars: rotation;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 12 pages, 9 figures