Poster abstract details

The effect of stellar spots on the high precision transit light curve
M. Oshagh and N. C. Santos and I. Boisse and X. Dumusque and M. Montalto and N. Haghighipour and G. Boue


Stellar activity features like spots can cause difficulties in the determination of planetary parameters through spectroscopic and photometric observations. For example, the overlap of the transiting planet and stellar spots can produce anomalies in the transit
light curves. These can lead to the wrong estimation of the transit duration and timings, with consequences e.g. for the precise derivation of planetary radii. In this study, we carried out a quantitative study on the effect of stellar spot on high
precision transit light curves. We show that spot anomalies can lead to the estimate of a planet radius that is 4\% smaller than real value. The effects on the transit duration can also be of the order of 4\%, longer or shorter. More importantly, depending on the spot
sizes and distribution, anomalies can produce a transit timing variation signal with the amplitudes of the order of 200 seconds for typical sun-like spots. This amplitude can be corresponded to the transit timing variation amplitude produced by an Earth like planet on a Jovian planet in mean motion resonance. Furthermore we obtain the minimum size of the stellar spots which, can not affect the high precision transit light curve, to be around 0.03 of stellar radius. We also show that the strategy of allowing more parameters to be free (such as transit depth and duration) during fitting procedure to measure the transit time of each individual transit, will not work properly in the case of active stars.

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