First results of YSES – a direct imaging survey for exoplanets around solar mass stars in Sco-Cen

Many large-scale direct imaging surveys for extra-solar planets are plagued by two problems: (i) The estimated exoplanet masses are strongly limited by uncertainty in the age of the system and (ii) the statistical significance is diluted by the wide range of stellar masses selected. Furthermore, a lot of telescope time is spent for first-epoch observations of targets that do not host any companions.

We overcome these issues by observing a new sample of 72 solar-mass members of the approximately 16 Myr-old Lower Centaurus-Crux subgroup of Scorpius-Centaurus (Sco-Cen). We have taken short first-epoch observations with SPHERE/IRDIS at the Very Large Telescope (VLT). Each target star has been observed for five minutes in two filters. We construct a reference library of Point Spread Functions (PSFs) from all the observed target stars and apply Principal Component Analysis to remove the effects of the stellar halo.

Since all target stars have almost identical spectral types and apparent magnitudes, we show that our reference library PSF subtraction outperforms currently used methods for reduction of individual datasets. Despite the very short integration time, we are able to detect 10M_{jup} objects at separations of ~0.2’’ (25au at Sco-Cen) with 5-sigma significance. In the background limited regime, we are sensitive to companions with masses as low as 4M_{jup}.

At the current stage of our Young Suns Exoplanet Survey (YSES), we have identified 23 candidate planetary mass companions by comparison to evolutionary models within a color-magnitude diagram. Second epoch observations of these targets will be performed in April, 2018.

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