Transiting exoplanets from the CoRoT space mission: XXVI. CoRoT-24: A transiting multi-planet system

Abstract

We present the discovery of a candidate multiply-transiting system, the first one found in the CoRoT mission. Two transit-like features with periods of 5.11 and 11.76d are detected in the CoRoT light curve, around a main sequence K1V star of r=15.1. If the features are due to transiting planets around the same star, these would correspond to objects of 3.7$\pm$0.4 and 5.0$\pm$0.5 R_earth respectively. Several radial velocities serve to provide an upper limit of 5.7 M_earth for the 5.11~d signal, and to tentatively measure a mass of 28${}_{-11}^{+11}$ M_earth for the object transiting with a 11.76~d period. These measurements imply low density objects, with a significant gaseous envelope. The detailed analysis of the photometric and spectroscopic data serve to estimate the probability that the observations are caused by transiting Neptune-sized planets as $>$26$\times$ higher than a blend scenario involving only one transiting planet, and $>$900$\times$ higher than a scenario involving two blends and no planets. The radial velocities show a long term modulation that might be attributed to a 1.5 M_jup planet orbiting at 1.8~A.U. from the host, but more data are required to determine the precise orbital parameters of this companion.

13 pages, 13 figures, accepted to A&A, minor typos corrected

References in corpus (4)

• KEPLER's First Rocky Planet: Kepler-10b
• The ACS Nearby Galaxy Survey Treasury IX. Constraining asymptotic giant branch evolution with old metal-poor galaxies
• Modeling Kepler transit light curves as false positives: Rejection of blend scenarios for Kepler-9, and validation of Kepler-9d, a super-Earth-size planet in a multiple system
• Periodic variable stars in CoRoT field LRa02 observed with BEST II

Cited by in corpus (9)

• Aeronomical constraints to the minimum mass and maximum radius of hot low-mass planets
• An Overabundance of Low-density Neptune-like Planets
• A New Model of Roche-lobe Overflow for Short-Period Gaseous Planets and Binary Stars
• ExoClock Project: An open platform for monitoring the ephemerides of Ariel targets with contributions from the public
• Original Research By Young Twinkle Students (ORBYTS): Ephemeris Refinement of Transiting Exoplanets
• Ephemeris refinement of 21 Hot Jupiter exoplanets with high timing uncertainties
• Resonant sub-Neptunes are puffier
• The Occurrence-weighted Median Planets Discovered by Transit Surveys Orbiting Solar-type Stars and Their Implications for Planet Formation and Evolution
• CoRoT: The First Space-Based Transit Survey to Explore the Close-in Planet Population