HD 204018
HD 204018, also designated as HR 8202, is a visual binary located in the southern constellation Microscopium. The primary has an apparent magnitude of 5.58,[2] making it faintly visible to the naked eye under ideal conditions. The companion has an apparent magnitude of 8.09.[2] The system is located relatively close at a distance of 176 light years based on Gaia DR3 parallax measurements[1][3] but is receding with a heliocentric radial velocity of 18.3 km/s.[8] At its current distance, HD 204018's combined brightness is diminished by 0.13 magnitudes due to interstellar dust.[22]
HD 204018A is an Am star with a stellar classification of kA4hF0 VmF6,[5] indicating that it has the calcium K-line of an A4 star, the hydrogen lines of a F0 main-sequence star and the metallic lines of a F6 star. It has 1.65 times the mass of the Sun[10] and 2.55 times the Sun's radius.[11] It radiates 15 times the luminosity of the Sun[12] from its photosphere at an effective temperature of 6,778 K,[14] giving it a yellowish-white hue. At an age of 1.5 billion years, HD 2014018A is estimated to be on the subgiant branch.[4] An alternate model places it on the main sequence at an age of 1,35 billion years.[1] The object spins at a moderate speed with a projected rotational velocity of 85 km/s.[15]
The companion is an F8 main sequence star[7] located 2+1⁄2" away along a position angle of 151°.[23] It has an angular diameter of 0.186±0.035 arcseconds,[18] which yields a radius of 1.09 R☉ at its estimated distance.[17] It has 102% times the mass of the Sun[16] and an effective temperature of 6,235 K.[18] HD 204018B is estimated to be 3.46 billion years old and is slightly metal deficent.[19]
There is a magnitude 12 co-moving companion located 295.3" away from the system along a position angle of 75°.[23] It is a red dwarf with an estimated spectral class of K6 and any orbit would take over a million years.[24]
References
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