El doblete D del Sodio como indicador de la actividad cromosférica en estrellas de la secuencia principal

RODRIGO F. DÍAZ; PABLO J. D. MAUAS

San Juan, Argentina

Congreso; 47a Reunión Anual de la Asociación Argentina de Astronomía; 2004

Complejo Astronómico El Leoncito

We study the line profile of the sodium D doublet (5890 A and 5896 A) in dwarf stars with spectral type between M5.5 and F6. We find that the equivalent width of these lines shows a very good correlation with spectral type for stars later than K4. The flux absorbed in this region of the spectrum is then compared with the flux absorbed in the calcium H&K lines -a traditional activity indicator. For stars with (B-V)> 1.15 the correlation between absorbed fluxes is good and hence the sodium doublet is a good activity indicator. Since the doublet is found at longer wavelenghts than the calcium H & K lines, it is particularly useful for the study of chromospheric activity in late-type stars.