HD 81817
HD 81817 is a binary or possibly triple star system in the northern circumpolar constellation of Draco. It has an orange hue and is visible to the naked eye with an apparent visual magnitude of 4.28. The system is located at a distance of approximately 990 light years from the Sun based on parallax, and is drifting closer with a radial velocity of −7 km/s. It is a member of the IC 2391 moving group. The primary component of this system is an aging giant star with a stellar classification of K3III. The star's chromosphere is  of the type called "hybrid", displaying a cool stellar wind in combination with hot emission lines. It appears to be the source for the X-ray emission coming from this system. The star is 32 million years old with 4.3 times the mass of the Sun. With the supply of hydrogen at its core exhausted, the star has expanded to 109 times the Sun's radius. It is radiating 2,885 times the luminosity of the Sun from its photosphere at an effective temperature of 4,043. A possible companion star was discovered in 1984 based upon its ultraviolet spectrum. The distribution  of the far ultraviolet flux matches that of a white dwarf star of class DA. A 2020 study was unable to confirm or disprove this candidate white dwarf. In 2020, a substellar companion, probably a brown dwarf, was discovered in orbit around HD 81817 by radial velocity observations. It has a minimum mass of 27.1 , and orbits at 3.3 AU with a period of 1047.1 days and an eccentricity of 0.17. Gaia DR2 astrometry has also detected a companion with a mass of about 124 (with a high margin of error) orbiting at 2.67 AU, consistent with the radial velocity  detection. If the latter mass estimate is correct, this object would be a low-mass star, probably a red dwarf.