THE DISTANCE TO NGC 2264

Abstract

We determine the distance to the open cluster NGC 2264 using a statistical\nanalysis of cluster member inclinations. We derive distance-dependent values of\nsin i (where i is the inclination angle) for 97 stars in NGC 2264 from the\nrotation periods, luminosities, effective temperatures, and projected\nequatorial rotation velocities, v sin i, measured for these stars. We have\nmeasured 96 of the v sin i values in our sample by analyzing high-resolution\nspectra with a cross-correlation technique. We model the observed distribution\nof sin i for the cluster by assuming that member stars have random axial\norientations and by adopting prescriptions for the measurement errors in our\nsample. By adjusting the distance assumed in the observed sin i distribution\nuntil it matches the modeled distribution, we obtain a best-fit distance for\nthe cluster. We find the data to be consistent with a distance to NGC 2264 of\n913 pc. Quantitative tests of our analysis reveals uncertainties of 40 and 110\npc due to sampling and systematic effects, respectively. This distance estimate\nsuggests a revised age for the cluster of 1.5 Myrs, although more detailed\ninvestigations of the full cluster membership are required to draw strong\nconclusions.\n