HIP 107773

HIP 107773 is a star located 344 light years from Earth in the southern constellation Indus. It is classified as a horizontal branch K-type giant star, having a spectral type K0III and a radius of 11.6. With an apparent magnitude of 5.6, the star can be faintly seen with the naked eye. It has an exoplanet, HIP 107773 b, a gas giant orbiting it at a distance of 0.72 AU, about the same distance from Venus to the Sun.

Characteristics
HIP 107773 is a giant star, having a spectral type K0III, where K0 means it is a K-type star and III (luminosity class) means it is a giant star. The star is in the horizontal branch phase of evolution. HIP 107773 has a radius equivalent to 11.6 solar radii, and a mass equivalent to about 2.4 solar masses. It is cooler than the Sun, having an effective temperature of 4945 K. Given the mass and the evolutionary stage of the star, its age is estimated to be at least about one billion years.

Planetary system
HIP 107773 has an exoplanet, HIP 107773 b, discovered in 2015 using the radial velocity method. The planet is classified as a gas giant, having a minimum mass of 2 and an estimated radius of 1.19. It orbits its star at a distance of 0.72 AU, about the same distance as Venus is from the Sun, and completes one orbit every 144 day. Its orbit is almost circular, with an eccentricity of just 0.09.

With a mass of $105.5$, the star HIP 107773 is one of the most massive stars with a close-in planet.

Notes and references
