SIMBAD references

The analysis of 14 high resolution spectra of the Hg star HD 209459 recorded by the SWP camera on board the International Ultraviolet Explorer reveals large variations of the far ultraviolet flux of this star over the 18 yr of the mission. The two available Transiting Exoplanet Survey Satellite lightcurves of HD 209459 are periodic. The period, measured between two successive minima, is close to 6.25 ± 0.03 days which could be the rotational period of HD 209459. The FUV variations, which are unexpected for a late normal B-type star or a Hg-rich star, could be caused by large horizontal chemical or occasional thermal gradients.