SIMBAD references

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-M_V=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.