Astrometric planet search around southern ultracool dwarfs III. Discovery of a brown dwarf in a 3-year orbit around DE0630-18

Abstract

Using astrometric measurements obtained with the FORS2/VLT camera, we are searching for low-mass companions around 20 nearby ultracool dwarfs. With a single-measurement precision of 0.1 milli-arcseconds, our survey is sensitive to a wide range of companion masses from planetary companions to binary systems. Here, we report the discovery and orbit characterisation of a new ultracool binary at a distance of 19.5 pc from Earth that is composed of the M8.5-dwarf primary DE0630-18 and a substellar companion. The nearly edge-on orbit is moderately eccentric (e=0.23) with an orbital period of 1120 d, which corresponds to a relative separation in semimajor axis of approximately 1.1 AU. We obtained a high-resolution optical spectrum with UVES/VLT and measured the system's heliocentric radial velocity. The spectrum does not exhibit lithium absorption at 670.8 nm, indicating that the system is not extremely young. A preliminary estimate of the binary's physical parameters tells us that it is composed of a primary at the stellar-substellar limit and a massive brown-dwarf companion. DE0630-18 is a new very low-mass binary system with a well-characterised orbit.

4 pages, 7 figures. Accepted for publication in A&A

References in corpus (3)

• Discovery of new nearby L and late-M dwarfs at low Galactic latitude from the DENIS database
• Astrometric planet search around southern ultracool dwarfs I: First results, including parallaxes of 20 M8-L2 dwarfs
• Astrometric planet search around southern ultracool dwarfs II: Astrometric reduction methods and a deep astrometric catalogue

Cited by in corpus (8)

• Investigating the properties of stripped-envelope supernovae, what are the implications for their progenitors?
• Gaia DR3 astrometric orbit determination with Markov Chain Monte Carlo and Genetic Algorithms. Systems with stellar, substellar, and planetary mass companions
• The Hawaii Infrared Parallax Program. IV. A Comprehensive Parallax Survey of L0-T8 dwarfs with UKIRT
• Astrometric orbits of spectral binary brown dwarfs I: Massive T dwarf companions to 2M1059$-$21 and 2M0805$+$48
• Individual Dynamical Masses of DENIS J063001.4$-$184014AB Reveal A Likely Young Brown Dwarf Triple
• Gaia and VLT astrometry of faint stars: Precision of Gaia DR1 positions and updated VLT parallaxes of ultracool dwarfs
• New constraints on the minimum mass for thermonuclear lithium burning in brown dwarfs
• Astrometric planet search around southern ultracool dwarfs IV. Relative motion of the FORS2/VLT CCD chips