IM Pegasi

IM Pegasi is a binary star system located in the constellation Pegasus. It is a close binary, meaning the two stars are in close proximity to each other and orbit each other rapidly. This rapid orbit causes the system to exhibit extreme activity, making it a popular subject for stellar astrophysics research.

IM Pegasi is classified as an RS Canum Venaticorum (RS CVn) variable, a type of binary star system characterized by strong chromospheric activity, including starspots (analogous to sunspots) and flares. These starspots significantly impact the system's brightness, causing periodic variations in its light curve. The rapid rotation of the stars in the system amplifies these effects.

The primary star in the IM Pegasi system is a G-type subgiant, while the secondary star is a K-type main sequence star. Due to its proximity and rapid rotation, the primary star is tidally locked to the secondary star, meaning its rotational period is synchronized with its orbital period. This tidal locking contributes to the enhanced magnetic activity observed in the system.

One of the key characteristics of IM Pegasi is its use in Very Long Baseline Interferometry (VLBI) experiments. The strong radio emission from the system, generated by its intense magnetic activity, makes it an excellent source for calibrating astronomical instruments. By precisely tracking its radio emissions, astronomers can improve the accuracy of VLBI observations of more distant objects. Therefore, it plays a crucial role in astrometry and geodesy.

Further research into IM Pegasi helps astronomers better understand the dynamics of close binary star systems, the formation and behavior of starspots, and the generation of stellar magnetic fields.