HD 165259

HD 165259, also known as HR 6751 is a triple star system located in the southern circumpolar constellation of Apus. It has an apparent magnitude of 5.86, making it faintly visible to the naked eye Parallax measurements place the system at a distance of 138 light years,  and it is currently receding with a heliocentric radial velocity of $$.

HD 165259 consists of two main sequence stars, with stellar classifications of F5 V and G1 V, separated by two arc-seconds as of 2020. Speckle interferometry in 2008 revealed the primary to be a close binary itself, with the two components separated by $98 AU$. By 2020, the separation had decreased to $13.3 AU$. The outer pair take 542 years to complete a revolution while the inner pair complete their orbit within 32 years.

At present the primary has 122% the mass of the Sun and a slightly enlarged radius of as it is nearing the end of its main sequence life. It radiates at 6.2 times the luminosity of the Sun from its photosphere at an effective temperature of $$, giving a yellow-white hue. HD 165259A has an iron abundance 82% above solar levels, making it metal enriched. It is estimated to be nearly 2 billion years old and has a projected rotational velocity of less than $$. HD 165259B has 85% the mass of the Sun and an effective temperature of 5,328 K, giving an orange glow. The faint star orbiting the primary has a mass 76% that of the Sun.