The HARPS search for southern extra-solar planets. XLVII. Five Jupiter-mass planets in long-period orbits, one highly irradiated Neptune, one brown dwarf, and five stellar binaries

Abstract

Our aim is to detect and characterise long-period companions around main sequence stars (spectral types late F to early M). We use the RV method to search for exoplanets around stars. The RV variations are measured with HARPS at the ESO 3.6 metre telescope. The true mass and inclination of our heavier companions are provided by astrometry, for which we use proper motions from Hipparcos and Gaia. Five Jupiter-mass exoplanets are reported to orbit HIP54597, BD-210397 (x2), HD74698, and HD94771 with 8.9 yr, 5.2 yr, 17.4 yr, 9.4 yr, and 5.9 yr orbits, and to have minimum masses of $2.01\pm 0.03$, $0.7\pm 0.1$, $2.4_{-0.2}^{+1.5}$, $0.40\pm 0.06$, and $0.53\pm 0.03M_J$ respectively. HD74698 also hosts a highly irradiated Neptune in a 15 day orbit with a minimum mass of $0.07\pm 0.01M_J$. The mass of HIP54597 b can maximally increase by 10% - 30%, the minimum mass of HD74698 c is likely equal to its true mass, and BD-210397 c has a mass of $2.66_{-0.32}^{+0.63}{M}_J$. HD62364 hosts a brown dwarf with a true mass of $18.77_{-0.63}^{+0.66}{M}_J$ in an orbit of 14 yr. HD56380B, HD221638B, and HD33473C have minimum masses within the brown dwarf limits, in orbits of 8.9 yr, 16.6 yr, and 50 yr respectively; however, astrometric measurements reveal them to be stellar binaries, with masses of $375.3_{-8.4}^{+8.6}$, $110.0_{-3.7}^{+3.9}$, and $271.0_{-3.8}^{+3.9}{M}_J$. The orbits of the stellar binaries HD11938 and HD61383 are incomplete. The preliminary result for HD61383 is a 0.190 $M_{\odot }$ binary in a 39 yr orbit. The secondary of the binary system HD11938 has a mass of 0.33 $M_{\odot }$ - which is confirmed by a secondary peak in the CCF - and a preliminary period of 35 yr. The origin of the 3.0 yr RV signal of HD3964 is uncertain as it shows entanglement with the magnetic cycle of the star. We finally report one more star, HD11608, with a magnetic cycle that mimics a planetary signal.

22 pages, 32 figures, accepted for publication in A&A

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