RACE-OC project: Rotation and variability in the Ïμ Chamaeleontis, Octans, and Argus stellar associations

Abstract

Context. Rotational properties of late-type low-mass members of associations of known age provide a fundamental source of information on stellar internal structure and its evolution. Aims. We aim at determining the rotational and magnetic-related activity properties of stars at different stages of evolution. We focus our attention primarily on members of young stellar associations of known ages. Specifically, we extend our previous analysis in Paper I (Messina et al. 2010, A&A 520, A15) to 3 additional young stellar associations beyond 100 pc and with ages in the range 6-40 Myr: Chamaeleontis (∼6 Myr), Octans (∼20 Myr), and Argus (∼40 Myr). Additional rotational data of η Chamaeleontis and IC  2391 clusters are also considered. Methods. Rotational periods were determined by applying the Lomb-Scargle periodogram technique to photometric time-series data obtained by the All Sky Automated Survey (ASAS) and the Wide Angle Search for Planets (SuperWASP) archives. The magnetic activity level was derived from the amplitude of the V light curves. Results. We detected the rotational modulation and measured the rotation periods of 56 stars for the first time, confirmed 11 and revised 3 rotation periods already known from the literature. Adding the periods of 10 additional stars retrieved from the literature we determined a sample of 80 periodic stars at ages of ∼6, ∼20, and ∼40 Myr. Using the SuperWASP data we also revisited some of the targets studied in Paper I. Conclusions. With the present study we have completed the analysis of the rotational properties of the late-type members of all known young loose associations in the solar neighbourhood. Considering also the results of Paper I, we have derived the rotation periods of 241 targets: 171 confirmed, 44 likely, 26 uncertain. The period of the remaining 50 stars known to be part of loose associations still remains unknown. The rotation period distributions we provided in the 0.8-1.2 M⊙ mass range span nine different ages from 1 to ∼100 Myr. This rotation period catalogue, and specifically the new information presented in this paper at ∼6, 20, and 40 Myr, contributes significantly to a better observational description of the angular momentum evolution of young stars. The results of the angular momentum evolution model based on this period database will be presented in forthcoming papers. © 2011 ESO.