BX Trianguli

[5] The large occurrence of flares on BX Trianguli is the highest among eclipsing binaries after Castor C (YY Geminorum)[8] and might be related to rapid mass transfer between the components.

[5] BX Trianguli also has strong magnetic activity, manifested as starspots on the primary's surface and Hα emission.

[6][8] This system is composed of two red dwarfs, which have an ultra-short period of just 4.6 hours and a separation of 1.33 solar radii, or two and a half times the distance to the Moon.

[6] A circumbinary planet was discovered after analysis of eclipse timing variations by a high school student and his teacher.

After rulling out alternative expanations for the eclipse timing variations, the two discoverers found that they are caused by a seven-Jupiter-mass planet at a separation of 4.5 astronomical units (670,000,000 km), with an orbital eccentricity of 0.4.

Light curves for BX Triangluli, plotted from TESS data. The upper plot shows the variability as a function of orbital phase, and the lower plot shows a flare.