First Results of YSES – A Direct Imaging Survey for Exoplanets around Solar Mass Stars in Sco-Cen

Wednesday, 13 February 2019 8 a.m. — 9 a.m. MST

AURA Lecture Hall

NOIRLab South Colloquia
ALEXANDER BOHN (Leiden University, The Netherlands and Gemini South Visiting Astronomer)

Within the Young Suns Exoplanet Survey (YSES), we have observed a new sample of 72 solar-mass members of the approximately 16 Myr-old Lower Centaurus-Crux subgroup of the Scorpius-Centaurus Association (Sco-Cen). All targets have been observed with SPHERE/IRDIS for two minutes in each of two broadband filters. We construct a reference library of Point Spread Functions (PSFs) from the full sample of 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 10 M_{jup} objects at separations of ~0.2’’ with 5-sigma significance. In the background-limited regime, we are sensitive to companions with masses as low as 3 Mjup.

At the current stage of the survey, we have discovered new brown dwarf companions and identified several candidate planetary mass companions by comparison to evolutionary models within a color-magnitude diagram. Most fascinating is the detection of an almost face-on transition disk that shows a very strong gradient in its azimuthal brightness distribution that is also detected in polarized light. A possible explanation for that peculiar appearance might be an unresolved inner disk that is misaligned due to a sub-stellar perturber. Follow-up observations of all interesting targets will be carried out in the upcoming periods.