Ultraviolet flux distributions of stars in the Orion nebula cluster.

Abstract

New observations with the IUE have been used to derive the flux distributions of 15 stars in the Orion Nebula cluster, complete over the range 0.12-3.5 microns. Extinction curves are derived for the six stars which are significantly reddened, with E(B-V) greater than 0.2. When normalized to the visual, most of these show the weak far-UV extinction, similar to but not quite as pronounced as in the Trapezium stars. The lightly reddened stars are compared with a grid of reference stars of similar spectral type to investigate the intrinsic flux distributions of the upper main sequence of the cluster. No significant abnormalities are found, even for the spectroscopically peculiar broad-hydrogen-lined stars. The F-type pre-main-sequence star NV Ori evidences strong Mg II emission. The amplitude of the variability of T Ori was found to vary with wavelength in a fashion similar to the extinction curve formed relative to an A2 V star.