Population of giant planets around B stars from the first part of the BEAST survey^★

¹ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
² LESIA, Observatoire de Paris, Université PSL, CNRS, 5 Place Jules Janssen, 92190 Meudon, France
³ INAF – Osservatorio Astronomico di Padova ; Vicolo dell’Osservatorio 5, 35122 Padova, Italy
⁴ Institutionen för astronomi, Stockholms universitet; AlbaNova universitetscentrum, 106 91 Stockholm, Sweden
⁵ Centre de Recherche Astrophysique de Lyon (CRAL) UMR 5574, CNRS, Univ. de Lyon, Univ. Claude Bernard Lyon 1, ENS de Lyon, 69230 Saint-Genis-Laval, France
⁶ Physikalisches Institut, Universität Bern, Gesellschaftsstr. 6, 3012 Bern, Switzerland
⁷ Université Côte d’Azur, OCA, CNRS, UMR Lagrange, 06304 Nice, France
⁸ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁹ Fakultät für Physik, Universität Duisburg-Essen, Lotharstraße 1, 47057 Duisburg, Germany
¹⁰ Institüt für Astronomie und Astrophysik, Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
¹¹ Department of Astronomy, University of Michigan; 1085 S. University Ave, Ann Arbor MI 48109, USA
¹² Landessternwarte, Zentrum für Astronomie der Universität Heidelberg, Königstuhl 12, 69117 Heidelberg, Germany
¹³ University of Zurich, Department of Astrophysics, Winterthurerstr. 190 8057 Zurich, Switzerland
¹⁴ Trottier Institute for Research on Exoplanets, Université de Montréal, Montréal, H3C 3J7 Québec, Canada
¹⁵ Leiden Observatory, Leiden University, Leiden, The Netherlands
¹⁶ Scottish Universities Physics Alliance, Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
¹⁷ Aix-Marseille Univ., CNRS, CNES, LAM, Marseille, France

^★★ Corresponding author; philippe.delorme@univ-grenoble-alpes.fr

Received: 11 July 2024
Accepted: 27 September 2024

Abstract

Context. Exoplanets form from circumstellar protoplanetary disks whose fundamental properties (notably their extent, composition, mass, temperature, and lifetime) depend on the host star properties, such as their mass and luminosity. B stars are among the most massive stars and their protoplanetary disks test extreme conditions for exoplanet formation.

Aims. This paper investigates the frequency of giant planet companions around young B stars (median age of 16 Myr) in the Scorpius-Centaurus (Sco-Cen) association, the closest association containing a large population of B stars.

Methods. We systematically searched for massive exoplanets with the high-contrast direct imaging instrument SPHERE using the data from the BEAST survey, which targets a homogeneous sample of young B stars from the wide Sco-Cen association. We derived accurate detection limits in the case of non-detections.

Results. We found evidence in previous papers for two substellar companions around 42 stars. The masses of these companions are straddling the ~13 Jupiter mass deuterium burning limit, but their mass ratio with respect to their host star is close to that of Jupiter. We derived a frequency of such massive planetary-mass companions around B stars of 11₋₅⁺⁷%, accounting for the survey sensitivity.

Conclusions. The discoveries of substellar companions b Centaurib and μ² Sco B happened after only a few stars in the survey had been observed, raising the possibility that massive Jovian planets might be common around B stars. However, our statistical analysis shows that the occurrence rate of such planets is similar around B stars and around solar-type stars of a similar age, while B-star companions exhibit low mass ratios and a larger semi-major axis.