HD 59686 Ab

HD 59686 Ab is an exoplanet that orbits the giant star HD 59686 A in a close binary star system. It has a nearly circular orbit with a period of 300 days and a semi-major axis of 1.09 AU, slightly greater than the distance between Earth and the Sun. It has a minimum mass 6.9 times that of Jupiter, with the true mass depending on the orbital inclination, which is not yet known.^[2] HD 59686 Ab was discovered by radial velocity and first announced in November 2003,^[1] but the discovery was not formally published until 2016.^[2]

HD 59686 Ab

Discovery[1][2]
Discovered by	Mitchell et al., Ortiz et al.
Discovery site	Lick Observatory
Discovery date	November 16, 2003 (announced) October 2016 (published)
Detection method	Doppler spectroscopy
Orbital characteristics[2]
Epoch 2451482.024
Semi-major axis	1.0860+0.0006 −0.0007 AU
Eccentricity	0.05+0.03 −0.02
Orbital period (sidereal)	299.36+0.26 −0.31 d
Mean anomaly	301°+26° −85°
Argument of periastron	121°+28° −24°
Star	HD 59686 A
Physical characteristics[2]
Mass	≥6.92+0.18 −0.24 MJ

HD 59686, along with Nu Octantis, is one of the closest binary star systems known to host a planet orbiting a single star (i.e., not a circumbinary planet), posing a challenge to theories of planet formation.^[2]

References

1. Mitchell, D.; Frink, S.; Quirrenbach, A.; Fischer, D.; Marcy, G.; Butler, P. (2003). "Four Substellar Companions Found Around Nearby K Giant Stars". Bulletin of the American Astronomical Society. 35: 1234. Bibcode:2003AAS...203.1703M.
2. Ortiz, Mauricio; et al. (October 2016), "Precise radial velocities of giant stars. IX. HD 59686 Ab: a massive circumstellar planet orbiting a giant star in a 13.6 au eccentric binary system", Astronomy & Astrophysics, 595: 14, arXiv:1608.00963, Bibcode:2016A&A...595A..55O, doi:10.1051/0004-6361/201628791, S2CID 26289447, A55.