Evidence of a Substellar Companion to AB Dor C

J. B. Climent , J. P. Berger (1) , J. C. Guirado , J. M. Marcaide , I. Martí-Vidal , A. Mérand , E. Tognelli , M. Wittkowski

1 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble

Studies of fundamental parameters of very low-mass objects are indispensable to provide tests of stellar evolution models that are used to derive theoretical masses of brown dwarfs and planets. However, only objects with dynamically determined masses and precise photometry can effectively evaluate the predictions of stellar models. AB Dor C (0.090 M _⊙) has become a prime benchmark for calibration of theoretical evolutionary models of low-mass young stars. One of the ambiguities remaining in AB Dor C is the possible binary nature of this star. We observed AB Dor C with the VLTI/AMBER instrument in low-resolution mode at the J, H, and K bands. The interferometric observables at the K band are compatible with a binary brown dwarf system with tentative components AB Dor Ca/Cb with a K-band flux ratio of 5% ± 1% and a separation of 38 ± 1 mas. This implies theoretical masses of 0.072 ± 0.013 M _⊙ and 0.013 ± 0.001 M _⊙ for each component, near the hydrogen-burning limit for AB Dor Ca, and near the deuterium-burning limit, straddling the boundary between brown dwarfs and giant planets, for AB Dor Cb. The possible binarity of AB Dor C alleviates the disagreement between observed magnitudes and theoretical mass-luminosity relationships.

Keywords: Binary stars; Interferometric binary stars; Low mass stars; Brown dwarfs; Exoplanets; Interferometry; Infrared astronomy; Pre-main sequence stars; Young stellar objects; Stellar evolutionary models; Stellar evolution; Stellar evolutionary tracks; 154; 806; 2050; 185; 498; 808; 786; 1290; 1834; 2046; 1599; 1600; Astrophysics - Solar and Stellar Astrophysics; Astrophysics - Earth and Planetary Astrophysics

Domains: Sciences of the Universe [physics]

J. B. Climent, J. P. Berger, J. C. Guirado, J. M. Marcaide, I. Martí-Vidal, et al.. Evidence of a Substellar Companion to AB Dor C. The Astrophysical Journal Letters, 2019, 886, ⟨10.3847/2041-8213/ab5065⟩. ⟨insu-03702947⟩