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

We present measurements of the KI 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 sini 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 I 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.