[Paper Review] Transiting exoplanets from the CoRoT space mission XIV. CoRoT-11b: a transiting massive "hot-Jupiter" in a prograde orbit around a rapidly rotating F-type star

D. Gandolfi, G. Hébrard+53 more|Kölner Universitäts PublikationsServer (Universität zu Köln)|Sep 14, 2010

Stellar, planetary, and galactic studies91 references49 citations

TL;DR

This paper presents the discovery and characterization of CoRoT-11b, a massive hot-Jupiter exoplanet (2.33 M_Jup) transiting a rapidly rotating F-type star (T_eff = 6440 K, v sin i = 40 km/s). Using CoRoT photometry and radial velocity measurements from HARPS and UVES, the study confirms a prograde orbit with a short orbital period of 2.994 days and derives a high equilibrium temperature of 1657 K, contributing to the understanding of hot-Jupiter systems around evolved, fast-rotating stars.

ABSTRACT

The CoRoT exoplanet science team announces the discovery of CoRoT-11b, a fairly massive hot-Jupiter transiting a V=12.9 mag F6 dwarf star (M*=1.27 +/- 0.05 Msun, R*=1.37 +/- 0.03 Rsun, Teff=6440 +/- 120 K), with an orbital period of P=2.994329 +/- 0.000011 days and semi-major axis a=0.0436 +/- 0.005 AU. The detection of part of the radial velocity anomaly caused by the Rossiter-McLaughlin effect shows that the transit-like events detected by CoRoT are caused by a planet-sized transiting object in a prograde orbit. The relatively high projected rotational velocity of the star (vsini=40+/-5 km/s) places CoRoT-11 among the most rapidly rotating planet host stars discovered so far. With a planetary mass of mp=2.33+/-0.34 Mjup and radius rp=1.43+/-0.03 Rjup, the resulting mean density of CoRoT-11b (rho=0.99+/-0.15 g/cm^3) can be explained with a model for an inflated hydrogen-planet with a solar composition and a high level of energy dissipation in its interior.

Motivation & Objective

• To identify and characterize a transiting exoplanet orbiting a rapidly rotating F-type star detected by the CoRoT space mission.
• To determine the orbital and physical parameters of the planet and its host star using combined photometric and spectroscopic data.
• To investigate the spin-orbit alignment of the system to assess whether the planet's orbit is prograde or misaligned.
• To constrain the planetary mass, radius, density, and equilibrium temperature through transit and radial velocity modeling.
• To examine the implications of the planet's high mass and short orbital period in the context of planetary migration and evolution around active, fast-rotating stars.

Proposed method

• CoRoT space telescope monitored the star's brightness over time to detect transit events, providing light curves for orbital and planetary parameter estimation.
• Radial velocity measurements from the HARPS and UVES spectrographs at ESO telescopes were used to detect the star's Doppler shift due to planetary gravitational pull.
• Stellar parameters were derived from high-resolution spectroscopy, including effective temperature, surface gravity, metallicity, and rotational velocity (v sin i = 40.0 ± 5.0 km/s).
• Orbital parameters were fitted using a joint analysis of transit light curves and radial velocity curves, assuming zero eccentricity (e = 0 fixed).
• Stellar evolution models were applied to estimate the star's mass (1.27 ± 0.05 M☉), radius (1.37 ± 0.03 R☉), age (2.0 ± 1.0 Gyr), and distance (560 ± 30 pc).
• Planetary parameters such as mass (2.33 ± 0.34 M_Jup), radius (1.43 ± 0.03 R_Jup), density (0.99 ± 0.15 g/cm³), and equilibrium temperature (1657 ± 55 K) were derived from the combined analysis of transit depth and radial velocity amplitude.

Experimental results

Research questions

• RQ1 What are the orbital and physical parameters of the transiting exoplanet CoRoT-11b?
• RQ2 Is the planetary orbit aligned with the spin axis of its rapidly rotating F-type host star?
• RQ3 What is the equilibrium temperature of CoRoT-11b, and how does it compare to other hot Jupiters?
• RQ4 How does the high mass and short orbital period of CoRoT-11b affect its evolutionary and dynamical context?
• RQ5 What constraints does the system place on theories of planetary migration and tidal evolution around active, fast-rotating stars?

Key findings

• CoRoT-11b has a mass of 2.33 ± 0.34 M_Jup and a radius of 1.43 ± 0.03 R_Jup, resulting in a low density of 0.99 ± 0.15 g/cm³.
• The planet orbits its host star in a very short period of 2.994330 ± 0.000011 days, with a semi-major axis of 0.0436 ± 0.005 AU.
• The host star is a rapidly rotating F-type star with an effective temperature of 6440 ± 120 K, surface gravity log g = 4.22 ± 0.23 dex, and a projected rotational velocity of 40.0 ± 5.0 km/s.
• The system exhibits a prograde orbit, with the planet's orbital inclination at 83.170 ± 0.150 degrees, and an impact parameter of 0.818 ± 0.008.
• The equilibrium temperature of CoRoT-11b is 1657 ± 55 K, indicating extreme irradiation, consistent with its close-in orbit.
• The star is relatively young (2.0 ± 1.0 Gyr), has a metallicity of [Fe/H] = -0.03 ± 0.08 dex, and is located at a distance of 560 ± 30 pc with significant interstellar extinction (A_V = 0.55 ± 0.10 mag).