An imaged 15 MJup companion within a hierarchical quadruple system
Henning, T.; Janson, M.; Langlois, M.; Lagrange, A. -M.; Desidera, S.; Rubini, P.; Delorme, P.; Bonnefoy, M.; Chomez, A.; Squicciarini, V.; Gratton, R.; Chauvin, G.; Samland, M.; Reffert, S.; Meyer, M. R.; Mamajek, E. E.; Engler, N.; Marleau, G. -D.; Flasseur, O.; Viswanath, G.; Bergeon, S.; Albert, D.; Ringqvist, S. C.
France, Italy, Sweden, Switzerland, Germany, United States
Abstract
Context. Since 2019, the direct imaging B-star Exoplanet Abundance STudy (BEAST) at SPHERE@VLT has been scanning the surroundings of young B-type stars in order to ascertain the ultimate frontiers of giant planet formation. Recently, the 17−4+3 Myr HIP 81208 was found to host a close-in (∼50 au) brown dwarf and a wider (∼230 au) late M star around the central 2.6 M⊙ primary.
Aims: Alongside the continuation of the survey, we are undertaking a complete reanalysis of archival data aimed at improving detection performances so as to uncover additional low-mass companions.
Methods: We present here a new reduction of the observations of HIP 81208 using the patch covariance algorithm (PACO), a recent and powerful algorithm dedicated to processing high-contrast imaging datasets, as well as more classical algorithms and a dedicated point spread function subtraction approach. The combination of different techniques allowed for a reliable extraction of astrometric and photometric parameters.
Results: A previously undetected source was recovered at a short separation from the C component of the system. Proper motion analysis provided robust evidence for the gravitational bond of the object to HIP 81208 C. Orbiting C at a distance of ∼20 au, this 15 MJup brown dwarf becomes the fourth object of the hierarchical HIP 81208 system.
Conclusions: Among the several BEAST stars which are being found to host substellar companions, HIP 81208 stands out as a particularly striking system. As the first stellar binary system with substellar companions around each component ever found by direct imaging, it yields exquisite opportunities for thorough formation and dynamical follow-up studies.