A complete census of planet-hosting binaries

¹ LIRA, Observatoire de Paris, Université PSL, 5 Place Jules Janssen, 92195 Meudon, France
² Sapienza Università di Roma, Piazzale Aldo Moro 5, 00185 Rome, Italy

^★ Corresponding author.

Received: 9 May 2025
Accepted: 23 June 2025

Abstract

Aims. Estimating the effect that binarity can have on planet formation is of crucial importance, as almost half of field stars reside in multiple systems. One effective way to assess this effect is to get an accurate picture of the population of planet-hosting binaries and compare the characteristics to those of field star binaries.

Methods. We have constructed an extensive database through intensive literature exploration to achieve a complete census of all planet-hosting binaries known to date. Despite the heterogeneous character of the different surveys this database is built on and the biases and selection effects that unavoidably affect any sample of planet-hosting binaries, we looked for statistically significant trends and correlations within our sample.

Results. Our database provides the characteristics (orbit or projected separation, stellar masses, distance, dynamical stability) for 759 systems (among which 31 are circumbinaries), representing an increase by a factor of nine with respect to the previous complete census of planet-hosting binaries. Of the 728 S-type systems, 651 are binaries, 73 are triples, and 4 are quadruples. The raw distribution of planet-hosting binary separations peaks around 500 au instead of 50 au for field binaries. By analysing the distribution of on-sky angular separations as a function of distance (d_b) to the systems, we argue that the observed deficit of planet-hosting close-in binaries cannot be explained solely by observational biases. Likewise, by exploring how multiplicity fractions among planet hosts vary with d_b, we suggest that the subsample of known planet-hosting binaries at <500 pc is not bias dominated (but also not bias-free). In this <500 pc domain, the multiplicity fraction of planet-hosting stars is ~22.5%, which is approximately half of the value for field stars, and the deficit of binaries extends to separations of ~500 au, giving an approximate estimate of the detrimental effect binarity has on planet formation.