WIde Separation Planets In Time (WISPIT)

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Context. Wide separation gas giant planets present a challenge to current planet formation theories, and the detection and characterisation of these systems enables us to constrain their formation pathways. Aims. The WIde Separation Planets In Time (WISPIT) survey aims to detect and characterise wide separation planetary-mass companions over a range of ages from <5 to 20 Myr around solar-type host stars at distances of 75-500 (median 140) parsecs. Methods. The WISPIT survey carries out two five-minute H -band exposures with the VLT/SPHERE instrument and IRDIS camera separated by at least six months to identify co-moving companions via proper motion analysis. These two H -band observations in combination with a follow-up K s -band observation were used to determine the colour and magnitude of the co-moving companions and to derive their masses through comparison to AMES-COND and AMES-DUSTY evolutionary tracks. Results. We report the discovery of WISPIT 1b and WISPIT 1c, two gas giant exoplanets that are co-moving with the stellar binary WISPIT 1, which itself consists of a K4 star and M5.5 star in a multi-decadal orbit. The planets are at projected separations of 338 au and 840 au and have masses of 10 M J and 4 M J , respectively. Conclusions. We identified two common proper motion planetary companions of a (previously unknown) stellar binary with a Sunlike primary. These targets are ideal for follow-up characterisation with both ground- and space-based telescopes. Monitoring of the orbit with the GRAVITY interferometer will place constraints on their eccentricity, and spectroscopic characterisation will identify the composition and metallicity, providing information on their formation pathways.

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