FF Andromedae

Lore & Background

FF Andromedae is a spectroscopic binary system consisting of two main sequence red dwarfs, both of spectral type M1Ve, indicating strong emission lines of H-alpha and CaII in their spectra. The stars are tidally locked, so their rotation period equals the orbital period of 2.17 days. The total mass of the system is 1.10 solar masses. The secondary component is not to be confused with a line-of-sight giant star listed in the Washington Double Star Catalog as WDS J00428+3533B, sometimes called GJ 29.1B, which is much more distant. The designation GJ 29.1B is also applied to the secondary red dwarf in the close spectroscopic binary.

Reader's Guide

FF Andromedae is significant as a BY Draconis variable star, showing regular brightness variations tied to its rotation period, but also exhibiting occasional stellar flares that increase its brightness by about a magnitude. Small amplitude variations on timescales of several minutes have been reported during quiescent phases. Notably, small but highly significant dips in the light curve have been detected approximately 25 minutes before a large flare, suggesting a precursor phenomenon. The system's tidally locked binary nature and flare activity make it a valuable object for studying stellar activity and flare prediction.

Did You Know?

• FF Andromedae is a spectroscopic binary with both stars being main sequence red dwarfs of spectral type M1Ve.
• The system has a total mass of 1.10 M☉ and an orbital period of 2.17 days.
• Small dips in the light curve occur about 25 minutes before a large flare.
• The secondary red dwarf is also designated GJ 29.1B, but a different, distant giant star shares that catalog number.