The Monitor project: Rotation of low-mass stars in the open cluster NGC 2547

TL;DR

This study conducted a detailed photometric survey of the open cluster NGC 2547, analyzing low-mass star rotation periods to understand stellar rotational evolution across different ages.

Contribution

It provides the first comprehensive rotation period distribution for low-mass stars in NGC 2547 and compares it with other clusters to test stellar rotational evolution models.

Findings

Rotation period distribution varies with stellar mass.

Models of rotational evolution match observed data without major modifications.

Cluster's rotation distribution is intermediate between younger and older clusters.

Abstract

We report on the results of an I-band time-series photometric survey of NGC 2547 using the MPG/ESO 2.2m telescope with WFI, achieving better than 1% photometric precision per data point over 14 <~ I <~ 18. Candidate cluster members were selected from a V vs V-I colour magnitude diagram over 12.5 < V < 24 (covering masses from 0.9 Msol down to below the brown dwarf limit), finding 800 candidates, of which we expect ~330 to be real cluster members, taking into account contamination from the field (which is most severe at the extremes of our mass range). Searching for periodic variations in these gave 176 detections over the mass range 0.1 <~ M/Msol <~ 0.9. The rotation period distributions were found to show a clear mass-dependent morphology, qualitatively intermediate between the distributions obtained from similar surveys in NGC 2362 and NGC 2516, as would be expected from the age of this cluster. Models of the rotational evolution were investigated, finding that the evolution from NGC 2362 to NGC 2547 was qualitatively reproduced (given the uncertainty in the age of NGC 2547) by solid body and core-envelope decoupled models from our earlier NGC 2516 study without need for significant modification.