UBVI and Hα photometry of the young open cluster NGC 2244.
PARK B.-G. and SUNG H.
Abstract (from CDS):
New UBVI and Hα photometry has been performed for the young open cluster NGC 2244. We classified 30 OB stars as being members of the cluster using proper-motion data and spectral types from previous investigators, along with photometric diagrams obtained in this study. We measured Hα emission strength of the stars by Hα photometry and set up a selection criterion to select pre-main-sequence (PMS) stars with Hα emission. Fourteen PMS stars and seven PMS candidates were found using the criterion. In addition, six stars found near the positions of ROSAT HRI X-ray sources were assumed to be PMS stars and the optical counterparts of these X-ray sources. We determined a reddening of <E(B-V)>=0.47±0.04 for the cluster and a total-to-selective extinction ratio of RV=3.1±0.2. The distance modulus derived was V0-MV=11.1. By comparing our photometric results with theoretical evolution models, we derived a main-sequence turnoff age of 1.9 Myr and a PMS age spread of about 6 Myr. The slope of the initial mass function, Γ, calculated in the mass range 0.5≤logm≤2.0 could be flat (Γ=-0.7±0.1).
open clusters and associations: individual (NGC 2244) - Stars: Pre-Main-Sequence