X-ray emission and low-mass stars in the young open cluster NGC 2547

Abstract

We present the results of deep ROSAT High Resolution Imager X-ray observations and broad-band BVIC CCD photometry of the young open cluster NGC 2547. We have been able to find cluster counterparts for the majority of the 102 significant X-ray sources detected, confirming the power of high spatial resolution X-ray observations to find low-mass, magnetically active members of distant open clusters. The age of the cluster has been determined by fitting the main-sequence turn-off and the positions of low-mass stars on their pre-main-sequence tracks. The two methods yield 55 ± 25 and 14 ± 4 Myr respectively, but we consider the lower age to be more reliable because of the comparatively large number of low-mass stars that constrain the fit. We deduce that any age spread among the low-mass stars is < 10 Myr and any small spread that exists could be attributable to binarity and starspots.