Rotational modulation of the chromospheric activity in KHI 1 Orionis (GO V).

Abstract

The solar type star χ¹ Ori is thought to have an age of 6×10⁸yr and an apparent rotation period of 5^d.1. These characteristics make it well suited for a rotational modulation study of its strong ultraviolet emission lines. The authors have made IUE observations at four different phases during each of three separate rotation cycles over a time span of 325^d. The data show cyclical variations in the emission lines due to C IV (1549 Å) and He II (1640 Å). The amplitude of the flux variations in C IV exceeds a factor of 2. On the other hand, the flux in the Mg II emission (2800 Å) is constant to within the photometric uncertainties of IUE. These observations are consistent with a uniform spatial distribution and brightness for the Mg II emission network and a more complicated distribution of the regions producing the ultraviolet transition region emission.