XO-7 b: A transiting hot Jupiter with a massive companion on a wide orbit

Abstract

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, $T_{\mathrm{eff}}=6250\pm 100\mathrm{K}$, $[Fe/H]=0.432\pm 0.057\mathrm{dex}$). We conducted photometric and radial velocity follow-up with a team of amateur and professional astronomers. XO-7 b has a period of $2.8641424\pm 0.0000043$ days, a mass of $0.709\pm 0.034{\mathrm{M}}_{\mathrm{J}}$, a radius of $1.373\pm 0.026{\mathrm{R}}_{\mathrm{J}}$, a density of $0.340\pm 0.027\mathrm{g}{\mathrm{cm}}^{-3}$, and an equilibrium temperature of $1743\pm 23\mathrm{K}$. 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 $\sim 100\mathrm{m}{\mathrm{s}}^{-1}$ over two years, yielding a minimum mass of $4{\mathrm{M}}_{\mathrm{J}}$; 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 towards 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.

16 pages, 6 figures, Accepted for publication in AJ

References in corpus (21)

• Modules for Experiments in Stellar Astrophysics (MESA)
• The Transiting Exoplanet Survey Satellite
• Spectroscopic parameters for 451 stars in the HARPS GTO planet search program. Stellar [Fe/H] and the frequency of exo-Neptunes
• Gaia Data Release 1: Catalogue validation
• Astrometric exoplanet detection with Gaia
• WASP-1b and WASP-2b: Two new transiting exoplanets detected with SuperWASP and SOPHIE
• Kepler constraints on planets near hot Jupiters
• Misaligned spin-orbit in the XO-3 planetary system?
• XO-2b: Transiting Hot Jupiter in a Metal-rich Common Proper Motion Binary
• XO-3b: A Massive Planet in an Eccentric Orbit Transiting an F5V Star
• A Transiting Planet of a Sun-like Star
• Friends of Hot Jupiters II: No Correspondence Between Hot-Jupiter Spin-Orbit Misalignment and the Incidence of Directly Imaged Stellar Companions
• H2O abundances in the atmospheres of three hot Jupiters
• Friends of Hot Jupiters. IV. Stellar companions beyond 50 AU might facilitate giant planet formation, but most are unlikely to cause Kozai-Lidov migration
• The asteroseismic potential of TESS: exoplanet-host stars
• EXOFASTv2: A public, generalized, publication-quality exoplanet modeling code
• A Class of Warm Jupiters with Mutually Inclined, Apsidally Misaligned, Close Friends
• Detecting stars, galaxies, and asteroids with Gaia
• Testing asteroseismology with Gaia DR2: Hierarchical models of the Red Clump
• Discovery of XO-6b: a hot Jupiter transiting a fast rotating F5 star on an oblique orbit
• Average Albedos of Close-in Super-Earths and Neptunes from Statistical Analysis of Long Cadence Kepler Secondary Eclipse Data

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