Radio emission in a nearby ultracool dwarf binary: a multi-frequency study

Abstract

The substellar triple system VHS J125601.92$-$125723.9 is composed by an equal-mass M7.5 brown dwarf binary and a L7 low-mass substellar object. In this work, we aim to identify the origin of the radio emission occurring in the central binary of VHS 1256$-$1257 while discussing the expected mechanisms involved in the radio emission of ultracool dwarfs (UCDs). We observed this system with the Karl G. Jansky Very Large Array, the European very-long-baseline interferometry (VLBI) Network, the enhanced Multi Element Remotely Linked Interferometer Network, the NOrthern Extended Millimeter Array, and the Atacama Large Millimetre Array at frequencies ranging from 5 GHz up to 345 GHz in several epochs during 2017, 2018, and 2019. We have found radio emission at 6 GHz and 33 GHz coincident with the expected position of the central binary of VHS~1256$-$1257. The Stokes I density flux detected were 73 $\pm$ 4 $\mu$Jy and 83 $\pm$ 13 $\mu$Jy, respectively, with no detectable circular polarisation or pulses. No emission is detected at higher frequencies (230 GHz and 345 GHz) nor at 5 GHz with VLBI arrays. The emission appears to be stable over almost 3 years at 6 GHz. To explain the constraints obtained both from the detections and non-detections we considered multiple scenarios including thermal and non-thermal emission, and different contributions from each component of the binary. Our results can be well explained by non-thermal gyrosynchrotron emission originating at radiation belts with a low plasma density (n${}_e$ = 300$-$700 cm${}^{-3}$), a moderate magnetic field strength (B $\approx$ 140 G), and an energy distribution of electrons following a power-law ($dN/dE\propto E^{-\delta }$) with $\delta$ fixed at 1.36. These radiation belts would need to be present in both components and also be viewed equatorially.

arXiv commentAccepted for publication in A&A. 13 pages, 6 figures

References in corpus (49)

• Direct Imaging of Multiple Planets Orbiting the Star HR 8799
• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• Evolutionary models for very-low-mass stars and brown dwarfs with dusty atmospheres
• Images of a fourth planet orbiting HR 8799
• Stellar Radio Astronomy. Probing Stellar Atmospheres from Protostars to Giants
• Simulations of dynamo action in fully convective stars
• Testing a Predictive Theoretical Model for the Mass Loss Rates of Cool Stars
• Confirmation of the Electron Cyclotron Maser Instability as the Dominant Source of Radio Emission from Very Low Mass Stars and Brown Dwarfs
• The large-scale axisymmetric magnetic topology of avery-low-mass fully-convective star
• Activity in Very Cool Stars: Magnetic Dissipation in late-M and L Dwarf Atmospheres
• The Extremely Red, Young L Dwarf PSO J318-22: A Free-Floating Planetary-Mass Analog to Directly Imaged Young Gas-Giant Planets
• Radio Observations of a Large Sample of Late-M, L, and T Dwarfs: The Distribution of Magentic Field Strengths
• Periodic Bursts of Coherent Radio Emission from an Ultracool Dwarf
• A Volume-limited Sample of 63 M7-M9.5 Dwarfs II. Activity, magnetism, and the fade of the rotation-dominated dynamo
• Flaring Up All Over -- Radio Activity in Rapidly-Rotating Late-Type M and L Dwarfs
• Discovery of a young planetary mass companion to the nearby M dwarf VHS J125601.92-125723.9
• Substructure in the Circumstellar Disk around the Young Star AU Mic (GJ 803)
• Strong dipole magnetic fields in fast rotating fully convective stars
• Auroral radio emission from late L and T dwarfs: A new constraint on dynamo theory in the substellar regime
• Magnetic Inhibition of Convection and the Fundamental Properties of Low-Mass Stars. II. Fully Convective Main Sequence Stars
• Periodic Radio and H-alpha Emission from the L Dwarf Binary 2MASSW J0746425+200032: Exploring the Magnetic Field Topology and Radius of an L Dwarf
• Bistability and hysteresis of dipolar dynamos generated by turbulent convection in rotating spherical shells
• What controls the magnetic geometry of M dwarfs?
• Discovery of an Unusually Red L-type Brown Dwarf
• Simultaneous, Multi-Wavelength Variability Characterization of the Free-Floating Planetary Mass Object PSO J318.5-22
• Cloud Atlas: Discovery of Patchy Clouds and High-amplitude Rotational Modulations In a Young, Extremely Red L-type Brown Dwarf
• A three-dimensional model for the radio emission of magnetic chemically peculiar stars
• Weak and Strong Field Dynamos: from the Earth to the stars
• Spectral Variability of VHS J1256-1257 b from 1 to 5 $\mu$m
• Periodic Radio Emission from the M7 Dwarf 2MASS J13142039+1320011: Implications for the Magnetic Field Topology
• Adaptive Optics imaging of VHS 1256-1257: A Low Mass Companion to a Brown Dwarf Binary System
• Imaging Jupiter's radiation belts down to 127 MHz with LOFAR
• A possible third component in the L dwarf binary system DENIS-P J020529.0-115925 discovered with the Hubble Space Telescope
• The ultracool dwarf DENIS-P J104814.7-395606. Chromospheres and coronae at the low-mass end of the main-sequence
• Radio Flaring from the T6 Dwarf WISEPC J112254.73+255021.5 with A Possible Ultra-short Periodicity
• Steady and Transient Radio Emission from Ultracool Dwarfs
• Discovery of a Visual T-Dwarf Triple System and Binarity at the L/T Transition
• Radio Emission from the Exoplanetary System $\epsilon$ Eridani
• VLA multifrequency observations of RS CVn binaries
• Radio Stars: from kHz to THz
• Spectral energy distribution simulations of a possible ring structure around the young, red brown dwarf G196-3B
• Thermal Infrared Imaging and Atmospheric Modeling of VHS J125601.92-125723.9 b: Evidence for Moderately Thick Clouds and Equilibrium Carbon Chemistry in a Hierarchical Triple System
• X-ray emission from the M9 dwarf 1RXS J115928.5-524717 - Quasi-quiescent coronal activity at the end of the main sequence
• Radio emission in ultracool dwarfs: the nearby substellar triple system VHS 1256$-$1257
• Probing the magnetosphere of the M8.5 dwarf TVLM513-46546 by modelling its auroral radio emission. Hint of star exoplanet interaction?
• Modelling the environment around five ultracool dwarfs via the radio domain
• Detection of 2$-$4 GHz Continuum Emission from $\epsilon$ Eridani
• Detection of photometric variability in the very low-mass binary VHS J1256-1257AB using TESS and Spitzer

Cited by in corpus (5)

• Resolved imaging of an extrasolar radiation belt around an ultracool dwarf
• Evidence for a radiation belt around a brown dwarf
• The effects of resistivity on oscillatory reconnection and consequences for solar flare Quasi Periodic Pulsations
• New constraints on the presence of debris disks around G 196-3 B and VHS J125601.92-125723.9 b
• Radio Emission from a Nearby M dwarf Binary