Free access article

A&A 371, 652-666 (2001)
DOI: 10.1051/0004-6361:20010409

The effect of stellar activity on the Li I 6708, Na I 5896 and K I 7699 Ålines

A comparison with the Pleiades, field stars and the Sun

D. Barrado y Navascués¹, R. J. García López^{2, 3}, G. Severino⁴ and M. T. Gomez<sup>4

1</sup>  Departamento de Física Teórica, C-XI-506, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
²  Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain
    e-mail: rgl@ll.iac.es
³  Departamento de Astrofísica, Universidad de La Laguna, Av. Astrofísico Francisco Sánchez s/n, 38071 La Laguna, Tenerife, Spain
⁴  Osservatorio Astronomico di Capodimonte, Via Moiariello, 16, 80131 Napoli, Italy
    e-mail: severino@na.astro.it; gomez@na.astro.it

(Received 9 June 2000 / Accepted 12 March 2001)

Abstract
An analytical model has been developed to empirically study the effects of stellar spots and faculae on the observed equivalent widths of Li I 6708, Na I 5896 and K I 7699 Ålines (and abundances in the case of lithium) in late-type stars, taking into account the changes in the observed magnitudes and colors. Solar spectra corresponding to different active regions are used as input data and a range of filling factors are applied to simulate the surfaces of stars with different levels of activity. Detailed comparisons between predicted and observed photometric colors and equivalent widths are made for late-type stars of the Pleiades and the field. The observed dispersions in K I and Li I equivalent widths for Pleiades stars can be partially accounted by the simultaneous effects of activity on colors and the line formation, indicating that the lithium-rotation connection suggested for ~ Pleiades stars could be due in part to the stellar activity. However, under realistic values for the filling factors, only a small portion of the observed spread could be explained by these effects.

Key words: Sun: activity -- Sun: faculae, plages -- sunspots -- stars: abundances -- stars: activity -- stars: late type

Offprint request: D. Barrado y Navascués, barrado@pollux.ft.uam.es

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