Looking for Super-Earths in the HD 189733 System: A Search for Transits in Most Space-Based Photometry

TL;DR

This study conducted a detailed search for small transiting exoplanets in the HD 189733 system using space-based photometry, setting limits on the presence of Super-Earths and Neptunes in close orbits.

Contribution

It provides the first comprehensive transit search for small exoplanets in HD 189733 using MOST data, constraining the existence of Super-Earths and Neptunes in that system.

Findings

No additional close-in exoplanets detected within size limits.

Constraints placed on the presence of Super-Earths and Neptunes in the system.

Demonstrates the feasibility of detecting small planets around active stars.

Abstract

We have made a comprehensive transit search for exoplanets down to ~1.5 - 2 Earth radii in the HD 189733 system, based on 21-days of nearly uninterrupted broadband optical photometry obtained with the MOST (Microvariability & Oscillations of STars) satellite in 2006. We have searched these data for realistic limb-darkened transits from exoplanets other than the known hot Jupiter, HD 189733b, with periods ranging from about 0.4 days to one week. Monte Carlo statistical tests of the data with synthetic transits inserted into the data-set allow us to rule out additional close-in exoplanets with sizes ranging from about 0.15 - 0.31 RJ (Jupiter radii), or 1.7 - 3.5 RE (Earth radii) on orbits whose planes are near that of HD 189733b. These null results constrain theories that invoke lower-mass hot Super-Earth and hot Neptune planets in orbits similar to HD 189733b due to the inward migration of this hot Jupiter. This work also illustrates the feasibility of discovering smaller transiting planets around chromospherically active stars.