Rotation and lithium in the late-type stars of NGC 2516

Abstract

We present CCD photometry and high-resolution spectroscopy of low-mass stars in the open cluster NGC 2516, which has an age of about 150Myr and may have a much lower metallicity than the Pleiades. 24 probable F to early K type, single cluster members have been identified from their photometry and radial velocities, along with three possible spectroscopic binaries. The projected equatorial velocities are measured and compared with younger and older clusters. Several fast rotating late G /early K stars are seen, but all hotter stars have ve sini < 20kms ¹1 . The data are consistent with angular momentum loss models with spindowntime-scales thatincreasefromtensofMyrforGstarstohundredsofMyrforKstars.The observed X-ray activity is consistent with the currently accepted rotation–activity paradigm. Lithium abundances are derived from the Li I 6708-Au line. The pattern of Li depletion is indistinguishablefromthatinthePleiades,including aspreadinthe,K0stars,wherethemost rapid rotators suffer the least Li depletion. The observations argue in favour of either a metallicity in the range ¹0:1 <[Fe/H]< 0:0 for NGC 2516, or a lower metallicity and extra Li depletion through non-standard mixing modes which occurs on time-scales of only ,50Myr. Neither our low signal-to-noise ratio spectroscopy nor our photometry can constrain [Fe/H] sufficiently to decide between these possibilities. A detailed spectroscopic chemical abundance analysis is urgently required.