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Abstract:

We report on the results of a time-series photometric survey of NGC 2362, carried out using the CTIO 4-m Blanco telescope and Mosaic-II detector as part of the Monitor project. Rotation periods were derived for 271 candidate cluster members over the mass range 0.1 ≲ M/M⊙ ≲ 1.2. The rotation period distributions show a clear mass-dependent morphology, qualitatively similar to that in NGC 2264, as would be expected from the age of this cluster. Using models of angular momentum evolution, we show that angular momentum losses over the ∼1-5 Myr age range appear to be needed in order to reproduce the evolution of the slowest rotators in the sample from the ONC to NGC 2362, as found by many previous studies. By incorporating Spitzer IRAC mid-infrared (mid-IR) measurements, we found that three to four objects showing mid-IR excesses indicative of the presence of circumstellar discs were all slow rotators, as would be expected in the disc regulation paradigm for early pre-main-sequence angular momentum evolution, but this result is not statistically significant at present, given the extremely limited sample size. © 2008 RAS.

Abstract:

We present the results of a systematic search for transiting planets in a ∼5 Myr open cluster, NGC 2362. We observed ∼1200 candidate cluster members, of which ∼475 are believed to be genuine cluster members, for a total of ∼100 h. We identify 15 light curves with reductions in flux that pass all our detection criteria, and six of the candidates have occultation depths compatible with a planetary companion. The variability in these six light curves would require very large planets to reproduce the observed transit depth. If we assume that none of our candidates are, in fact, planets then we can place upper limits on the fraction of stars with hot Jupiters (HJs) in NGC 2362. We obtain 99 per cent confidence upper limits of 0.22 and 0.70 on the fraction of stars with HJs (fp) for 1-3 and 3-10 d orbits, respectively, assuming all HJs have a planetary radius of 1.5RJup. These upper limits represent observational constraints on the number of stars with HJs at an age ≲10 Myr, when the vast majority of stars are thought to have lost their protoplanetary discs. Finally, we extend our results to the entire Monitor project, a survey searching young, open clusters for planetary transits, and find that the survey as currently designed should be capable of placing upper limits on fp near the observed values of fp in the solar neighbourhood. © 2008 RAS.