The spin-orbit angle of the transiting hot jupiter CoRoT-1b

TL;DR

This paper measures the spin-orbit angle of the transiting hot Jupiter CoRoT-1b, revealing a significant misalignment that challenges previous patterns and suggests planet-planet scattering as a key migration mechanism.

Contribution

It provides the first high-accuracy measurement of the spin-orbit angle for CoRoT-1b, a Jovian-mass planet on a circular orbit, indicating a strong misalignment.

Findings

CoRoT-1b has a projected spin-orbit angle of 77 ± 11 degrees.

The system's misalignment challenges previous correlations with planet mass and orbit eccentricity.

Supports planet-planet scattering as a mechanism for close-in gas giant migration.

Abstract

We measure the angle between the planetary orbit and the stellar rotation axis in the transiting planetary system CoRoT-1, with new HIRES/Keck and FORS/VLT high-accuracy photometry. The data indicate a highly tilted system, with a projected spin-orbit angle lambda = 77 +- 11 degrees. Systematic uncertainties in the radial velocity data could cause the actual errors to be larger by an unknown amount, and this result needs to be confirmed with further high-accuracy spectroscopic transit measurements. Spin-orbit alignment has now been measured in a dozen extra-solar planetary systems, and several show strong misalignment. The first three misaligned planets were all much more massive than Jupiter and followed eccentric orbits. CoRoT-1, however, is a jovian-mass close-in planet on a circular orbit. If its strong misalignment is confirmed, it would break this pattern. The high occurence of misaligned systems for several types of planets and orbits favours planet-planet scattering as a mechanism to bring gas giants on very close orbits.