Photometric and Spectroscopic Study of the Young Open Cluster NGC 1893

We present uvbyβ CCD photometry of the field of the open cluster NGC 1893. Our photometry is deep enough to cover the complete main-sequence B spectral type. We identify ~50 very likely members of the cluster down to spectral type B9-A0, some of which have much higher reddenings than the average. We derive a color excess E(b-y)=0.33+/-0.03 and a dereddened distance modulus V0-MV=13.9+/-0.2. From the β index, we identify several candidates as emission-line stars, for which we have obtained spectroscopy. Three of them display spectra corresponding to spectral type F but showing Hα in emission. Photometric measurements in this and previous studies indicate strong variability. These characteristics show them to be pre-main-sequence stars of spectral type F. We also identify two likely Herbig Be stars. These results hint at the existence of a sizable pre-main-sequence population in NGC 1893.