Photometric and spectroscopic study of the young open cluster NGC 1893

We present uvby beta CCD photometry of the field of the open cluster NGC 18 93. Our photometry is deep enough to cover the complete main-sequence B spe ctral type. We identify similar to 50 very likely members of the cluster do wn to spectral type B9-A0, some of which have much higher reddenings than t he average. We derive a color excess E(b-y) = 0.33 +/- 0.03 and a dereddene d distance modulus V-0 - M-V = 13.9 +/- 0.2. From the beta index, we identi fy several candidates as emission-line stars, for which we have obtained sp ectroscopy. Three of them display spectra corresponding to spectral type F but showing H alpha in emission. Photometric measurements in this and previ ous 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.