Modelling the environment around five ultracool dwarfs via the radio domain

Abstract

We present the results of a series of short radio observations of six ultracool dwarfs made using the upgraded VLA in S (2--4GHz) and C (4--7GHz) bands. LSR J1835+3259 exhibits a 100 percent right-hand circularly polarised burst which shows intense narrowband features with a fast negative frequency drift of about $-30$ MHz ${\text{s}}^{-1}$. They are superimposed on a fainter broadband emission feature with a total duration of about 20 minutes, bandwidth of about 1 GHz, centred at about 3.5 GHz, and a slow positive frequency drift of about 1 MHz ${\text{s}}^{-1}$. This makes it the first such event detected below 4 GHz and the first one exhibiting both positive and negative frequency drifts. Polarised radio emission is also seen in 2MASS J00361617+1821104 and NLTT 33370, while LP 349-25 and TVLM 513-46546 have unpolarised emission and BRI B0021-0214 was not detected. We can reproduce the main characteristics of the burst from LSR J1835+3259 using a model describing the magnetic field of the dwarf as a tilted dipole. We also analyse the origins of the quiescent radio emission and estimate the required parameters of the magnetic field and energetic electrons. Although our results are non-unique, we find a set of models which agree well with the observations.

arXiv comment16 pages, 9 figures, 5 tables

References in corpus (63)

• Evolutionary models for very-low-mass stars and brown dwarfs with dusty atmospheres
• Constraining the Age-Activity Relation for Cool Stars: The SDSS DR5 Low-Mass Star Spectroscopic Sample
• New Neighbors from 2MASS: Activity and Kinematics at the Bottom of the Main Sequence
• Large-scale magnetic topologies of late M dwarfs
• Large-scale magnetic topologies of mid-M dwarfs
• A morphological algorithm for improving radio-frequency interference detection
• Simulations of dynamo action in fully convective stars
• Post-correlation radio frequency interference classification methods
• The First Direct Measurements of Magnetic Fields on Very Low-Mass Stars
• Improved Astrometry and Photometry for the Luyten Catalog. II. Faint Stars and the Revised Catalog
• Confirmation of the Electron Cyclotron Maser Instability as the Dominant Source of Radio Emission from Very Low Mass Stars and Brown Dwarfs
• Radio Observations of a Large Sample of Late-M, L, and T Dwarfs: The Distribution of Magentic Field Strengths
• L Dwarfs and the Substellar Mass Function
• Periodic Bursts of Coherent Radio Emission from an Ultracool Dwarf
• Large-scale alpha^2-dynamo in low-mass stars and brown dwarfs
• The NIRSPEC Ultracool Dwarf Radial Velocity Survey
• A Volume-limited Sample of 63 M7-M9.5 Dwarfs II. Activity, magnetism, and the fade of the rotation-dominated dynamo
• Activity and Kinematics of Ultracool Dwarfs Including An Amazing Flare Observation
• Rotation Velocities for M-dwarfs
• Flaring Up All Over -- Radio Activity in Rapidly-Rotating Late-Type M and L Dwarfs
• Magnetospherically driven optical and radio aurorae at the end of the stellar main sequence
• Rotational Modulation of the Radio Emission from the M9 Dwarf TVLM 513-46546: Broadband Coherent Emission at the Substellar Boundary?
• Simultaneous Multi-Wavelength Observations of Magnetic Activity in Ultracool Dwarfs. III. X-ray, Radio, and H-alpha Activity Trends in M and L Dwarfs
• The Solar Neighborhood XXXII. The Hydrogen Burning Limit
• The Radio Activity-Rotation Relation of Ultracool Dwarfs
• BOSS Ultracool Dwarfs I: Colors and Magnetic Activity of M and L dwarfs
• 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
• The Magnetic Properties of an L Dwarf Derived from Simultaneous Radio, X-ray, and H-alpha Observations
• Trends in Ultracool Dwarf Magnetism. I. X-Ray Suppression and Radio Enhancement
• Studying the Physical Diversity of Late-M Dwarfs with Dynamical Masses
• Simultaneous Multi-Wavelength Observations of Magnetic Activity in Ultracool Dwarfs. I. The Complex Behavior of the M8.5 Dwarf TVLM513-46546
• Spectroscopic classification of red high proper motion objects in the Southern Sky
• Photometric Variability in the Ultracool Dwarf BRI 0021-0214: Possible Evidence for Dust Clouds
• Ultra-high-time Resolution Observations of Radio Bursts on AD Leonis
• New Neighbors: Parallaxes of 18 nearby stars selected from the LSPM-north catalog
• Wideband Spectroscopy of Two Radio Bursts on AD Leonis
• On the Radii of Brown Dwarfs Measured with AKARI Near-Infrared Spectroscopy
• Periodic Radio Emission from the M7 Dwarf 2MASS J13142039+1320011: Implications for the Magnetic Field Topology
• The Radio Spectrum of TVLM513-46546: Constraints on the Coronal Properties of a Late M Dwarf
• Imaging Jupiter's radiation belts down to 127 MHz with LOFAR
• Periodic Optical Variability of Radio Detected Ultracool Dwarfs
• Simultaneous Multiwavelength Observations of Magnetic Activity in Ultracool Dwarfs. IV. The Active, Young Binary NLTT 33370 AB (=2MASS J13142039+1320011)
• Wideband Dynamic Radio Spectra of Two Ultra-cool dwarfs
• Trends in Ultracool Dwarf Magnetism. II. The Inverse Correlation Between X-ray Activity and Rotation as Evidence for a Bimodal Dynamo
• Volume-limited radio survey of ultracool dwarfs
• The Rotation Period and Magnetic Field of the T Dwarf 2MASSI J1047539+212423 Measured From Periodic Radio Bursts
• Discovery of Radio Emission from the Tight M8 Binary: LP 349-25
• 3D simulations of gyrosynchrotron emission from mildly anisotropic nonuniform electron distributions in symmetric magnetic loops
• High-Precision Radio and Infrared Astrometry of LSPM J1314+1320AB - II: Testing Pre--Main-Sequence Models at the Lithium Depletion Boundary with Dynamical Masses
• LP 349-25: a new tight M8V binary
• Rotational Modulation of M/L Dwarfs due to Magnetic Spots
• Magnetic fields in fully convective M-dwarfs: oscillatory dynamos vs bistability
• Radio detections of southern ultracool dwarfs
• Steady and Transient Radio Emission from Ultracool Dwarfs
• The First Millimeter Detection of a Non-Accreting Ultracool Dwarf
• Comparative analysis of two formation scenarios of bursty radio emission from ultracool dwarfs
• Timing Analysis of the Periodic Radio and Optical Brightness Variations of the Ultracool Dwarf, TVLM 513-46546
• The magnetosphere of the ultracool dwarf DENIS 1048-3956
• Towards understanding dynamo action in M dwarfs
• High-Precision Radio and Infrared Astrometry of LSPM J1314+1320AB - I: Parallax, Proper Motions, and Limits on Planets
• Characterization of the Benchmark Binary NLTT 33370
• Rotational modulation of the linear polarimetric variability of the cool dwarf TVLM 513$-$46546
• Electron beam induced radio emission from ultracool dwarfs

Cited by in corpus (10)

• A scaling relationship for non-thermal radio emission from ordered magnetospheres: from the top of the Main Sequence to planets
• Evidence for a radiation belt around a brown dwarf
• Probing the magnetosphere of the M8.5 dwarf TVLM513-46546 by modelling its auroral radio emission. Hint of star exoplanet interaction?
• Low-frequency GMRT observations of ultra-cool dwarfs
• Radio emission in a nearby ultracool dwarf binary: a multi-frequency study
• Greening of the Brown Dwarf Desert. EPIC 212036875 b -- a 51 M${}_{\mathrm{J}}$ object in a 5 day orbit around an F7 V star
• Radio Emission from Ultra-Cool Dwarfs
• Searching for stellar flares from low mass stars using ASKAP and TESS
• The Potential of Detecting Radio-flaring Ultracool Dwarfs at L band in the FAST Drift-scan Survey
• A scaling relationship for non-thermal radio emission from ordered magnetospheres - II. Investigating the efficiency of relativistic electron production in magnetospheres of BA-type stars