SIMBAD references

UBVI and Hα photometry is presented for 17319 stars in vicinity of the young double cluster h and χ Persei. Our photometry extends over a 37'x1° field centered on the association. We construct reddening contours within the imaged field. We find that the two clusters share a common distance modulus of 11.75±0.05 and ages of logage(yr)=7.1±0.1. From the V-Hα color, a measure of the Hα emission strength, we conduct a survey for emission line objects within the association. We detect a sample of 33 Be stars, eight of which are new detections. We present a scenario of evolutionary enhancement of the Be phenomenon to account for the peak in Be fraction toward the top of the main sequence in the population of h and χ Persei and similar young clusters.