Astrometric planet search around southern ultracool dwarfs. V. Discovery of the exoplanet candidate PALTA-1 b

Abstract

We report the discovery of ,M_̊m Jup, depending on the uncertain mass of the ultracool dwarf host. The system's mass ratio is about 0.010, and the relative separation is estimated at 1.6--3.4 au. This discovery finalises a larger astrometric planet search survey that targeted 20 nearby ultracool dwarfs and previously discovered three new ultracool binary systems. a sub-Jupiter mass exoplanet candidate orbiting the nearby early-L dwarf DENIS-P J1253108-570924 ( over more than eight years and characterising the deviations from the expected single-source motion. The estimated planet mass is between 0.54,M_̊m Jup and located at a distance of ∼17 pc. The exoplanet was discovered by monitoring the L dwarf's astrometric motion with FORS2 at the Very Large Telescope 0.77 If confirmed, would be one of the very few known examples of a giant planet orbiting a nearby ultracool dwarf.