On the potassium-rotation connection in late-type Alpha Persei stars

Abstract

Abstract. We present measurements of the K  λ7699 line from spectra of 19 late-type members of the αPersei cluster obtained with the Intermediate Dispersion Spectrograph at the Isaac Newton Telescope. These stars span a narrow range of T eff , from 5091 K to 4771 K, and a wide range of v sin i values (9 km s −1 -170 km s −1 ). For a given star, we find empirically that larger rotational broadening apparently increases the equivalent width of K  λ7699 linearly for v sin i values from 15 km s −1 to 75 km s −1 . This correlation breaks down for v sin i > 75 km s −1 . After correction for this effect, we show that the potassium line equivalent widths do not really correlate with v sin i.

The seven sisters DANCe

“…We have already discussed its relation with activity via surface inhomogeneities in Barrado y Navascués et al (2001b), and compared with other lines produced by alkali elements such as sodium and potassium, which are not depleted in the stellar interior, concluding that at least partially the change in effective temperature (lower when compared with the spotless photosphere) should produce an increase in the observed lithium equivalent width for the same abundance. A similar conclusion has been derived by Randich (2001), at least for stars warmer than ∼ 5400 K: activity modifies the potassium equivalent widths, and thus the inferred potassium abundances (but see also the study of stars in the Alpha Per cluster by Martín et al 2005).…”

Lithium in LP 944−20★

“…Indeed, only pEW of atomic lines can be measured in respect to the background formed by the haze of TiO lines (Pavlenko 1997a,b; Zapatero Osorio et al 2002). The pEW values depend on the strength of the background molecular bands of TiO, on the spectral resolution of the data and on other broadening parameters (see Martín et al 2005 for an example of how rotation affects the EWs of K i resonance lines). Reducing the TiO absorption in the region across the 670.8‐nm line increases the relative strength of the computed Li lines and the formally determined lithium abundance decreases.…”