Orbital motion and dynamical mass of the complex periodic variable binary system 2MASS J05082729-2101444

Abstract

We used very long baseline interferometry to constrain the orbit of the binary system 2MASS J05082729-2101444. We observed the system with the VLBA in three epochs at a frequency of 4.85 GHz, which provides an angular resolution of about 3 mas. We combined the three radio astrometric observations, 119 RVs (60 VIS and 59 NIR) obtained with the CARMENES high-resolution spectrograph over a period of 8.1 years, and a relative astrometric measurement of an archival H-band Keck NIRC adaptive optics image to fit the orbital motion of the binary system. The VLBA observations resolved the binary system and show emission from both stellar components, with similar flux-density levels (0.34-0.67 mJy), and showing slight temporal flux variations. The emission appears quiescent, with no significant circular polarization, and with no flare events. We obtained an orbital motion fit of the binary system, which shows an eccentric orbit (e = 0.71), an orbital period of 2.19 yr, and a semimajor axis of 26.964 mas (1.3 au). The VLBA observations made it possible to resolve the binary system and identify both stars as radio-loud sources. The combined fit shows that 2M0508-21 is an M-dwarf binary with a total dynamical mass of $0.459\pm 0.007$ M${}_{\odot }$, assuming Gaia's parallax. This mass is slightly higher than those estimated from the luminosity and theoretical evolutionary models. The upper limit of the circular polarization at 4.85 GHz ($\lesssim$10\%), the persistence of the quiescent emission, and the relatively low brightness temperatures are consistent with a gyro-synchrotron or synchrotron origin of the radio emission. Further VLBA observations are needed to obtain the individual masses of the stars, as well as to verify Gaia's parallax of the system. A complete characterization of the system will help improve evolutionary models for young objects at the substellar boundary.

12 pages, 8 figures, 2 tables. Accepted in A&A

References in corpus (52)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Astropy: A Community Python Package for Astronomy
• emcee: The MCMC Hammer
• The NumPy array: a structure for efficient numerical computation
• Gaia Data Release 3: Summary of the content and survey properties
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• Spectrum radial velocity analyser (SERVAL). High-precision radial velocities and two alternative spectral indicators
• The Role of Multiplicity in Disk Evolution and Planet Formation
• Radio Observations of a Large Sample of Late-M, L, and T Dwarfs: The Distribution of Magentic Field Strengths
• The Gould's Belt Distances Survey (GOBELINS) I. Trigonometric parallax distances and depth of the Ophiuchus complex
• Gaia Data Release 3: Catalogue Validation
• VLBA determination of the distance to nearby star-forming regions II. Hubble 4 and HDE 283572 in Taurus
• Rotation of Low-Mass Stars in Upper Scorpius and Rho Ophiuchus with K2
• The CARMENES search for exoplanets around M dwarfs. First visual-channel radial-velocity measurements and orbital parameter updates of seven M-dwarf planetary systems
• Coherent radio emission from a quiescent red dwarf indicative of star-planet interaction
• Auroral radio emission from late L and T dwarfs: A new constraint on dynamo theory in the substellar regime
• The SPOTS Models: A Grid of Theoretical Stellar Evolution Tracks and Isochrones For Testing The Effects of Starspots on Structure and Colors
• Dynamical traceback age of the $\beta$ Pictoris moving group
• The Strongest Magnetic Fields on the Coolest Brown Dwarfs
• The Arecibo Detection of the Coolest Radio-flaring Brown Dwarf
• The population of M dwarfs observed at low radio frequencies
• A Panchromatic View of Brown Dwarf Aurorae
• Orbiting Clouds of Material at the Keplerian Co-Rotation Radius of Rapidly Rotating Low Mass WTTs in Upper Sco
• ACRONYM III: Radial Velocities for 336 Candidate Young Low-Mass Stars in the Solar Neighborhood, Including 78 Newly Confirmed Young Moving Group Members
• A circular polarisation survey for radio stars with the Australian SKA Pathfinder
• A scaling relationship for non-thermal radio emission from ordered magnetospheres: from the top of the Main Sequence to planets
• Spectroscopic confirmation of M-dwarf candidate members of the Beta Pictoris and AB Doradus Moving Groups
• The Rotation Period and Magnetic Field of the T Dwarf 2MASSI J1047539+212423 Measured From Periodic Radio Bursts
• Radio Flaring from the T6 Dwarf WISEPC J112254.73+255021.5 with A Possible Ultra-short Periodicity
• High-Precision Radio and Infrared Astrometry of LSPM J1314+1320AB - II: Testing Pre--Main-Sequence Models at the Lithium Depletion Boundary with Dynamical Masses
• Variable and polarized radio emission from the T6 brown dwarf WISEP J112254.73+255021.5
• Resolved imaging of an extrasolar radiation belt around an ultracool dwarf
• Quasi-Quiescent Radio Emission from the First Radio-Emitting T Dwarf
• Radio detections of southern ultracool dwarfs
• The 5 GHz Arecibo Search for Radio Flares from Ultracool Dwarfs
• Fine structures of radio bursts from flare star AD Leo with FAST observations
• Rotation of Low-Mass Stars in Upper Centaurus Lupus and Lower Centaurus Crux with TESS
• Periodic Radio Emission from the T8 Dwarf WISE J062309.94-045624.6
• Evidence for a radiation belt around a brown dwarf
• An astrometric planetary companion candidate to the M9 Dwarf TVLM 513-46546
• The Multiplicity of M-Dwarfs in Young Moving Groups
• Complex Modulation of Rapidly Rotating Young M Dwarfs: Adding Pieces to the Puzzle
• Dynamical masses of M-dwarf binaries in young moving groups: I - The case of TWA 22 and GJ 2060
• 3D orbital architecture of a dwarf binary system and its planetary companion
• Even More Rapidly Rotating Pre-Main Sequence M Dwarfs with Highly Structured Light Curves: An Initial Survey in the Lower Centaurus-Crux and Upper Centaurus-Lupus Associations
• Non-thermal radio continuum emission from young nearby stars
• Radio Burst from a Stellar Coronal Mass Ejection
• Updated orbital monitoring and dynamical masses for nearby M-dwarf binaries
• Can scallop-shell stars trap dust in their magnetic fields?
• Hints of auroral and magnetospheric polarized radio emission from the scallop-shell star 2MASS J05082729$-$2101444
• Polarized, variable radio emission from the scallop-shell binary system DG CVn