35 Leonis (HIP 53019, HD 89010) is a spectroscopic binary star system located in the constellation of Leo, next to the star Zeta Leonis. It is located from Earth based upon parallax measurements. The system consists of a G-type star (yellow dwarf) and a red dwarf star. With an apparent magnitude of 5.97, it can be naked-eye visible only from dark skies.
35 Leonis was discovered to be a binary system in 2024, after analysis from Daniel Echeverri et al. using vortex fiber nulling, which is a technique for detecting and characterizing faint stellar companions that are close to their parent star. The team derived a visual separation of 56.9 milliarcseconds between both components using the CHARA array. Both stars are completing one orbit around each other every 537day. The system classifies as a single-lined spectroscopic binary (SB1).
35 Leonis the Flamsteed designation. Other designations for this system include HD 89010 from the Henry Draper Catalogue, HIP 53019 from the Hipparcos Catalogue and HR 4030 from the Bright Star Catalogue.
The main component, 35 Leonis A, is currently a main-sequence star that is evolving into a subgiant, based on its spectral class of G1.5V-IV. It has 34% more mass than the Sun, 2.12 times the radius of the Sun, and irradiates four times more luminosity than it. The effective temperature of 35 Leonis A is, which gives it the typical hue of a G-type star. The age of the star is around 5.25 billion years, which is around 14% older than the Solar System.
The secondary component, 35 Leonis B, is a red dwarf star. The mass of 35 Leonis B is estimated at, based on a mass of for the primary and a mass ratio of 0.11. An effective temperature of and an upper limit in the rotational velocity of are derived from the vortex fiber nulling's parameters. Other characteristics, such as the radius and luminosity, are unknown.