Modelling solar-like variability for the detection of Earth-like planetary transits. I. Performance of the three-spot modelling and harmonic function fitting

Abstract

We present a comparison of two methods of fitting solar-like variability to increase the efficiency of detection of Earth-like planetary transits across the disk of a Sun-like star. One of them is the harmonic fitting method that coupled with the BLS detection algorithm demonstrated the best performance during the first CoRoT blind test. We apply a Monte Carlo approach by simulating a large number of light curves of duration 150 days for different values of planetary radius, orbital period, epoch of the first transit, and standard deviation of the photon shot noise. Stellar variability is assumed in all the cases to be given by the Total Solar Irradiance variations as observed close to the maximum of solar cycle 23. After fitting solar variability, transits are searched for by means of the BLS algorithm. We find that a model based on three point-like active regions is better suited than a best fit with a linear combination of 200 harmonic functions to reduce the impact of stellar microvariability provided that the standard deviation of the noise is 2-4 times larger than the central depth of the transits. On the other hand, the 200-harmonic fit is better when the standard deviation of the noise is comparable to the transit depth. Our results show the advantage of a model including a simple but physically motivated treatment of stellar microvariability for the detection of planetary transits when the standard deviation of the photon shot noise is greater than the transit depth and stellar variability is analogous to solar irradiance variations.

8 pages, 6 figures, accepted by Astronomy & Astrophysics

References in corpus (6)

• A box-fitting algorithm in the search for periodic transits
• Characterising stellar micro-variability for planetary transit searches
• Observational Limits on Terrestrial-Sized Inner Planets Around the CM Draconis System Using the Photometric Transit Method with a Matched-Filter Algorithm
• Practical Planet Prospecting
• Exoplanet detection capability of the COROT space mission
• Comparing different approaches to model the rotational modulation of the Sun as a star

Cited by in corpus (11)

• Transit Detection in the MEarth Survey of Nearby M Dwarfs: Bridging the Clean-First, Search-Later Divide
• Short-lived spots in solar-like stars as observed by CoRoT
• Multiwavelength flux variations induced by stellar magnetic activity: effects on planetary transits
• A study of the performance of the transit detection tool DST in space-based surveys. Application of the CoRoT pipeline to Kepler data
• An iterative filter to reconstruct planetary transit signals in the presence of stellar variability
• Detection of Neptune-size planetary candidates with CoRoT data. Comparison with the planet occurrence rate derived from Kepler
• Determination of rotation periods in solar-like stars with irregular sampling: the Gaia case
• Correcting the effect of stellar spots on ARIEL transmission spectra
• Photospheric activity, rotation and magnetic interaction in LHS 6343 A
• Angular dependence of the facular-sunspot coverage relation as derived by MDI magnetograms
• Modelling solar-like variability for the detection of Earth-like planetary transits. II) Performance of the three-spot modelling, harmonic function fitting, iterative non-linear filtering and sliding boxcar filtering