Membership, lithium, and metallicity in the young open clusters IC 2602 and IC 2391: Enlarging the sample

Abstract

Abstract. We present lithium abundances for ∼50 X-ray selected candidate members of the 30-50 Myr old open clusters IC 2602 and IC 2391. These data enlarge and extend to cooler temperatures previous Li surveys of these clusters by Stauffer et al. (1989) and Randich et al. (1997). We also give for the first time an estimate of the metallicity of the two clusters which turns out to be close to solar. Radial velocity measurements together with Hα chromospheric emission and the presence/absence of other spectroscopic features are used to ascertain the membership status for the sample stars not yet confirmed as cluster members; rotational velocities have also been determined for all sample stars. Stars more massive than ∼1 M in both clusters show no sign of significant Li depletion, while lower mass stars are all lithium depleted, with the amount of Li depletion increasing to cooler temperatures. We confirm that the late-G and early-K stars in IC 2602 present a star-to-star scatter in Li abundances similar to, but not as large as the one in the Pleiades. A scatter is also seen among late-K and M dwarfs. Unlike in the Pleiades and Alpha Per clusters, the scatter among early-K stars in IC 2602 shows only marginal correlation with rotation. Our data suggest that the drop-off of lithium towards lower masses may start at an earlier color in IC 2391 than in IC 2602, but larger cluster samples are needed to confirm this result. In addition, whereas G and early K stars in the two clusters are, on average, more Li rich than their counterparts in the Pleiades, a fraction of the coolest stars, in particular in IC 2391, are as depleted as the lowest-Li Pleiades stars of the same mass. If they continue depleting Li on their way to the main sequence, they are expected to be more Li depleted than the Pleiades at the age of the latter cluster.

Search for associations containing young stars (SACY)

“…As expected, Li abundances for stars with temperatures hotter than about 5000 K are almost constant over the time span (∼65 Myr) covered by our sample of associations (King 1998;Soderblom et al 1999;Randich et al 1997Randich et al , 2001Stauffer et al 1989;Martin & Montes 1997;Jeffries et al 2003;Balachandran et al 1988Balachandran et al , 1996Randich et al 1998;Martín 1997). On the other hand, for those associations possessing members with effective temperatures as low as to 3600 K, the observed LDPs are clearly distinguishable (right panel of Fig.…”

“…As an additional test, we compared our abundances for IC 2391 (considered to be ArgA members) with those from Randich et al (2001). Using the EW from these authors, we also computed the Li abundances for the IC 2602 members as described above.…”

“…The present work continues this study and aims to derive the distribution of Li abundances for each of the nine associations resulting from a consolidated list of members. Since these associations are young, covering ages from about 5 Myr up to that of the Pleiades, they form an interesting "laboratory" for studying the Li depletion with age, as achieved for some open clusters (Randich et al 2001;Jeffries 2006).…”

Constraining the Lifetime of Circumstellar Disks in the Terrestrial Planet Zone: A Mid‐Infrared Survey of the 30 Myr old Tucana‐Horologium Association

“…For our calculations we adopt the long-baseline Tycho-2 proper motion (Høg et al 2000) and the Tuc-Hor space motion vector from ZW00. In subjecting HD 105 to the ( Randich et al 2001) and stronger than that found in $120 Myr old Pleiades stars (Soderblom et al 1993). Finally, the X-ray luminosity of HD 105 [log (L X ) ¼ 29:4 ergs s À1 ; Cutispoto et al 2002] is similar to what is expected for early-G stars with ages of 10-100 Myr ( Briceño et al 1997).…”

Lithium abundances of nearby young solar-type stars based on optical high-resolution spectroscopy

“…three strong lines included in our spectral range (Ni I 664.36 nm, Fe I 666.34 nm, and V I 662.48 nm) for all target stars. We then compared them with those measured in the spectra of stars of similar temperature in IC 2391 and IC 2602, which were old enough (30-50 Myr, Randich et al 2001) to ensure that their spectra are not affected by veiling. Therefore, we did not attempt any veiling correction in our young solar-type stars.…”