Hipparcos preliminary astrometric masses for the two close-in companions to HD 131664 and HD 43848. A brown dwarf and a low mass star

Abstract

[abridged] We attempt to improve on the characterization of the properties (orbital elements, masses) of two Doppler-detected sub-stellar companions to the nearby G dwarfs HD 131664 and HD 43848. We carry out orbital fits to the Hipparcos IAD for the two stars, taking advantage of the knowledge of the spectroscopic orbits, and solving for the two orbital elements that can be determined in principle solely by astrometry, the inclination angle $i$ and the longitude of the ascending node $\Omega$. A number of checks are carried out in order to assess the reliability of the orbital solutions thus obtained. The best-fit solution for HD 131664 yields $i=55\pm 33$ deg and $\Omega =22\pm 28$ deg. The resulting inferred true companion mass is then $M_c=23_{-5}^{+26}$ $M_J$. For \object{HD 43848}, we find $i=12\pm 7$ deg and $\Omega =288\pm 22$ deg, and $M_c=120_{-43}^{+167}$ $M_J$. Based on the statistical evidence from an $F$-test, the study of the joint confidence intervals of variation of $i$ and $\Omega$, and the comparison of the derived orbital semi-major axes with a distribution of false astrometric orbits obtained for single stars observed by Hipparcos, the astrometric signal of the two companions to HD 131664 and HD 43848 is then considered detected in the Hipparcos IAD, with a level of statistical confidence not exceeding 95%. We constrain the true mass of HD 131664b to that of a brown dwarf to within a somewhat statistically significant degree of confidence ($\sim 2-\sigma$). For HD 43848b, a true mass in the brown dwarf regime is ruled out at the $1-\sigma$ confidence level. [abridged]

arXiv comment13 pages, 6 figures, 4 tables. Accepted for publication in Astronomy & Astrophysics

Cited by in corpus (23)

• Extrasolar planet population synthesis IV. Correlations with disk metallicity, mass and lifetime
• Search for brown-dwarf companions of stars
• Statistical Properties of Brown Dwarf Companions: Implications for Different Formation Mechanisms
• Precise Dynamical Masses of Directly Imaged Companions from Relative Astrometry, Radial Velocities, and Hipparcos-Gaia DR2 Accelerations
• Stellar companions to exoplanet host stars: Lucky Imaging of transiting planet hosts
• Mass constraints on substellar companion candidates from the re-reduced Hipparcos intermediate astrometric data: Nine confirmed planets and two confirmed brown dwarfs
• 3-D selection of 167 sub-stellar companions to nearby stars
• Improved Dynamical Masses for Six Brown Dwarf Companions Using Hipparcos and Gaia EDR3
• The detection and characterisation of 54 massive companions with the SOPHIE spectrograph -- 7 new brown dwarfs and constraints on the BD desert
• The SOPHIE search for northern extrasolar planets. IV. Massive companions in the planet-brown dwarf boundary
• The SOPHIE search for northern extrasolar planets IX. Populating the brown dwarf desert
• True masses of the long-period companions to HD 92987 and HD 221420 from Hipparcos-Gaia astrometry
• Determining the true mass of radial-velocity exoplanets with Gaia: 9 planet candidates in the brown-dwarf/stellar regime and 27 confirmed planets
• The Masses of a Sample of Radial-Velocity Exoplanets with Astrometric Measurements
• Optimized modeling of Gaia-Hipparcos astrometry for the detection of the smallest cold Jupiter and confirmation of seven low mass companions
• Precise radial velocities of giant stars. XI. Two brown dwarfs in 6:1 mean motion resonance around the K giant star $\nu$ Ophiuchi
• Precise dynamical masses of new directly imaged companions from combining relative astrometry, radial velocities, and Hipparcos-Gaia eDR3 accelerations
• Gaia predicted brown dwarf detection rates around FGK stars in astrometry, radial velocity, and photometric transits
• A possible dividing line between massive planets and brown-dwarf companions
• A long-period massive planet around HD106515A
• Precise Masses and Orbits for Nine Radial Velocity Exoplanets
• htof: A new open-source tool for analyzing Hipparcos, Gaia, and future astrometric missions
• Model Independent Periodogram for Scanning Astrometry