XO-7 b: A Transiting Hot Jupiter with a Massive Companion on a Wide Orbit

Nicolas Crouzet , Brian F. Healy , Guillaume Hébrard (1) , P. R. Mccullough , Doug Long , Pilar Montañés-Rodríguez , Ignasi Ribas , Francesc Vilardell , Enrique Herrero , Enrique Garcia-Melendo , Matthieu Conjat (2) , Jerry Foote , Joe Garlitz , Phillip Vo , Nuno C. Santos , Jos de Bruijne , Hugh P. Osborn (3) , Shweta Dalal (1) , Louise D. Nielsen

1 IAP - Institut d'Astrophysique de Paris
2 OCA - Observatoire de la Côte d'Azur
3 LAM - Laboratoire d'Astrophysique de Marseille

Transiting planets orbiting bright stars are the most favorable targets for follow-up and characterization. We report the discovery of the transiting hot Jupiter XO-7 b and of a second, massive companion on a wide orbit around a circumpolar, bright, and metal-rich G0 dwarf (V = 10.52, {T}_eff}=6250+/- 100 {{K}}, [{Fe}/{{H}}]=0.432+/- 0.057 {dex}). We conducted photometric and radial velocity follow-up with a team of amateur and professional astronomers. XO-7 b has a period of 2.8641424+/- 0.0000043 days, a mass of 0.709+/- 0.034 {M}_{{J}}, a radius of 1.373+/- 0.026 {R}_{{J}}, a density of 0.340+/- 0.027 {{g}} {cm}}^-3, and an equilibrium temperature of 1743+/- 23 {{K}}. Its large atmospheric scale height and the brightness of the host star make it well suited to atmospheric characterization. The wide-orbit companion is detected as a linear trend in radial velocities with an amplitude of ∼ 100 {{m}} {{{s}}}^-1 over two years, yielding a minimum mass of 4 {M}_{{J}}; it could be a planet, a brown dwarf, or a low-mass star. The hot Jupiter orbital parameters and the presence of the wide-orbit companion point toward a high-eccentricity migration for the hot Jupiter. Overall, this system will be valuable to understand the atmospheric properties and migration mechanisms of hot Jupiters and will help constrain the formation and evolution models of gas giant exoplanets.

Keywords: Surveys; Visible astronomy; Radial velocity; 486; 498; 509; 753; 1711; 1709; 1708; 484; 2096; 1671; 1776; 1332; Astrophysics - Earth and Planetary Astrophysics; Astrophysics - Instrumentation and Methods for Astrophysics; Astrophysics - Solar and Stellar Astrophysics; Exoplanet astronomy; Exoplanets; Extrasolar gas giants; Hot Jupiters; Transits; Transit photometry; Transit instruments; Exoplanet systems; High resolution spectroscopy

Domains: Sciences of the Universe [physics]

Nicolas Crouzet, Brian F. Healy, Guillaume Hébrard, P. R. Mccullough, Doug Long, et al.. XO-7 b: A Transiting Hot Jupiter with a Massive Companion on a Wide Orbit. The Astronomical Journal, 2020, 159, ⟨10.3847/1538-3881/ab5b12⟩. ⟨insu-03667137⟩