Dynamical masses for two M1 + mid-M dwarf binaries monitored during the SPHERE-SHINE survey

¹ SUPA, Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK
e-mail: bb@roe.ac.uk
² Centre for Exoplanet Science, University of Edinburgh, Edinburgh, UK
³ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
⁴ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
⁵ INAF – Catania Astrophysical Observatory, via S.Sofia, 78 95123 Catania, Italy
⁶ INAF – Osservatorio Astronomico di Padova, Vicolo della Osservatorio 5, 35122 Padova, Italy
⁷ LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Jules Janssen, 92195 Meudon, France
⁸ IMCCE – Observatoire de Paris, 77 Avenue Denfert-Rochereau, 75014 Paris, France
⁹ American Association of Variable Star Observers (AAVSO), 49 Bay State Rd., Cambridge, MA 02138, USA
¹⁰ Vereniging Voor Sterrenkunde (VVS), Oostmeers 122 C, 8000 Brugge, Belgium
¹¹ Institutionen för astronomi, Stockholms Universitet, Stockholm, Sweden
¹² CRAL, UMR 5574, CNRS, Université de Lyon, ENS, 9 avenue Charles André, 69561 Saint Genis Laval Cedex, France
¹³ Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France
¹⁴ STAR Institute, Université de Liège, Allée du Six Août 19c, 4000 Liège, Belgium
¹⁵ Exoplanets and Stellar Astrophysics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA
¹⁶ Núcleo de Astronomía, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile
¹⁷ Escuela de Ingeniería Industrial, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile
¹⁸ Geneva Observatory, University of Geneva, 51 ch. Pegasi, 1290 Versoix, Switzerland
¹⁹ ESO Vitacura, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago de Chile, Chile
²⁰ Unidad Mixta Internacional Franco-Chilena de Astronomía, CNRS/INSU UMI 3386 and Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
²¹ Department of Astronomy, University of Michigan, Ann Arbor, MI, USA
²² Institute for Particle Physics and Astrophysics, ETH Zurich, Wolfgang-Pauli-Strasse 27, 8093 Zurich, Switzerland
²³ European Southern Observatory (ESO), Karl-Schwarzschild-Str. 2, 85748 Garching, Germany

Received: 14 October 2021
Accepted: 4 December 2021

Abstract

We present orbital fits and dynamical masses for HIP 113201AB and HIP 36985AB, two M1 + mid-M dwarf binary systems monitored as part of the SPHERE-SHINE survey. To robustly determine the age of both systems via gyrochronology, we undertook a photometric monitoring campaign for HIP 113201 and GJ 282AB, the two wide K star companions to HIP 36985, using the 40 cm Remote Observatory Atacama Desert telescope. Based on this monitoring and gyrochronological relationships, we adopt ages of 1.2 ± 0.1 Gyr for HIP 113201AB and 750 ± 100 Myr for HIP 36985AB. These systems are sufficiently old that we expect that all components of these binaries have reached the main sequence. To derive dynamical masses for all components of the HIP 113201AB and HIP 36985AB systems, we used parallel-tempering Markov chain Monte Carlo sampling to fit a combination of radial velocity, direct imaging, and Gaia and HIPPARCOS astrometry. Fitting the direct imaging and radial velocity data for HIP 113201 yields a primary mass of 0.54 ± 0.03 M_⊙, fully consistent with its M1 spectral type, and a secondary mass of 0.145 ± M_⊙. The secondary masses derived with and without including HIPPARCOS-Gaia data are all considerably more massive than the 0.1 M_⊙ mass estimated from the photometry of the companion. Thus, the dynamical impacts of this companion suggest that it is more massive than expected from its photometry. An undetected brown dwarf companion to HIP 113201B could be a natural explanation for this apparent discrepancy. At an age >1 Gyr, a 30 M_Jup companion to HIP 113201B would make a negligible (<1%) contribution to the system luminosity but could have strong dynamical impacts. Fitting the direct imaging, radial velocity, and HIPPARCOS-Gaia proper motion anomaly for HIP 36985AB, we find a primary mass of 0.54 ± 0.01 M_⊙ and a secondary mass of 0.185 ± 0.001 M_⊙, which agree well with photometric estimates of component masses, the masses estimated from M_K– mass relationships for M dwarf stars, and previous dynamical masses in the literature.