SIMBAD references

The photometric data from HI-1A on-board Solar TErrestrial RElations Observatory (STEREO)-A is investigated for the possibility of detecting planetary transits. If this is achievable, then STEREO could benefit the exoplanet community, which is lacking in continuous space-based observations around bright stars (R ≤ 9). The original light curves for ∼60 000 stellar targets with R-magnitudes between 4 and 12 exhibit a variety of trends due to solar contamination, tracking errors and vignetting, among others. In addition, there are noise components which are not so easily distinguishable, such as from overestimated sky corrections or satellite jitter. The trend removal pipeline (TRP) is a multi-stage process designed to minimize the noise in the HI-1A photometry, while conserving genuine stellar signals. The focus is on reducing the impact from noise on short and longer time-scales to increase the probability of detecting planetary transits. Following the TRP, the point-to-point scatter was measured in the original and detrended light curves. This indicates a substantial reduction in the overall noise levels, up to 49 per cent at R = 6. The correlated noise on 2 and 5 h time-scales was also estimated to assess the possibility of planet detection. These results show that, with the enhanced photometry, transit-like signals are detectable at depths of ≤ 1 per cent (10 mmag) for the majority of stars with R ≤ 10 and down to ∼0.2 per cent (2 mmag) for many stars with R ≤ 8. This statement is supported by a figure given in the article, which shows a primary signal with a depth of 6 mmag, detected with 4σ confidence and a possible secondary signal with a depth of 2 mmag. This is evidence that with STEREO, there is the capability to detect not only Hot-Jupiters, but also Hot-Neptunes, orbiting solar-type stars. This is the goal of a subsequent investigation, for which the results will be published in due course.