Update of SB9 orbits using HERMES/Mercator radial velocities

Abstract

Aims. By combining astrometric orbits (delivered in large numbers by the Gaίa mission) with spectroscopic orbits for systems with two observable spectra (SB2), it is possible to derive the masses of both stellar components. However, to get masses with a good accuracy requires accurate spectroscopic orbits, which is the primary aim of the present paper. A subsidiary aim is to discover SB2 systems hiding among known SB1 systems and even though this search may often prove unsuccessful, the acquired radial velocities may still be used to improve the existing spectroscopic orbits. Methods. New radial velocities for 58 binary systems from the Ninth Catalogue of Spectroscopic Binary Orbits (SB9), obtained using the high-resolution HERMES spectrograph installed on the 1.2 m Mercator telescope, were used to possibly identify hitherto undetected SB2 systems. For SB1 systems with inaccurate orbits, we used these new radial-velocity measurements to improve the orbital accuracy. Results. This study provides 51 orbits (41 SB1 and 10 SB2) that have been improved with respect to the solution listed in the SB9 catalogue, out of the 58 SB9 orbits studied, which belong to 56 stellar systems. Among them, there are five triple and four quadruple systems. Despite the high resolution of HERMES, the only system we detected as anew SB2 system is HIP 115142 A. The B component of the visual binary HIP 92726 has now been found to be a spectroscopic system as well, which makes HIP 92726 a newly discovered quadruple system (SB 1+SB 1). Moreover, the high resolution of HERMES has enabled us to better isolate the signature of the secondary component of HIP 12390, HIP 73182, and HIP 111170. Thus, we derived more accurate masses for them. Among the 30 SB also present in Gaia Data Release 3 (DR3), with periods shorter than the Gaia DR3 time span (~1000 d), only five had been flagged as binaries by DR3. Various DR3 selection criteria are responsible for this discrepancy.