SCYON Abstract

Received on February 27 2007

The Monitor project: Rotation of low-mass stars in the open cluster NGC 2516

AuthorsJonathan Irwin, Simon Hodgkin, Suzanne Aigrain, Leslie Hebb, Jerome Bouvier, Cathie Clarke, Estelle Moraux, and D.M. Bramich
Affiliation
Institute of Astronomy, Cambridge
University of St Andrews
Laboratoire d'Astrophysique, Grenoble
ING, La Palma
Accepted byMonthly Notices of the Royal Astronomical Society
Contactjmi@ast.cam.ac.uk
URLhttp://arxiv.org/abs/astro-ph/0702518
Links NGC 2516

Abstract

We report on the results of an i-band time-series photometric survey of NGC 2516 using the CTIO 4m Blanco telescope and 8k Mosaic-II detector, achieving better than 1% photometric precision per data point over 15 ~< i ~< 19. Candidate cluster members were selected from a V vs V-I colour magnitude diagram over 16 < V < 26 (covering masses from 0.7 M(sun) down to below the brown dwarf limit), finding 1685 candidates, of which we expect ~1000 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 362 detections over the mass range 0.15 ~< M/M(sun) ~< 0.7. The rotation period distributions were found to show a remarkable morphology as a function of mass, with the fastest rotators bounded by P > 0.25 days, and the slowest rotators for M ~< 0.5 M(sun) bounded by a line of P α M3, with those for M >~ 0.5 M(sun) following a flatter relation closer to P ~ constant. Models of the rotational evolution were investigated, finding that the evolution of the fastest rotators was well-reproduced by a conventional solid body model with a mass-dependent saturation velocity, whereas core-envelope decoupling was needed to reproduce the evolution of the slowest rotators. None of our models were able to simultaneously reproduce the behaviour of both populations.