The Discovery of Solar-like Activity Cycles Beyond the End of the Main Sequence?

Abstract

The long-term magnetic behavior of objects near the cooler end of the stellar main sequence is poorly understood. Most theoretical work on the generation of magnetism in these ultracool dwarfs (spectral type >=M7 stars and brown dwarfs) suggests that their magnetic fields should not change in strength and direction. Using polarized radio emission measurements of their magnetic field orientations, I demonstrate that these cool, low-mass, fully-convective objects appear to undergo magnetic polarity reversals analogous to those that occur on the Sun. This powerful new technique potentially indicates that the patterns of magnetic activity displayed by the Sun continue to exist, despite the fully convective interiors of these objects, in contravention of several leading theories of the generation of magnetic fields by internal dynamos.

Accepted to ApJL; 6 pages, 1 table

References in corpus (14)

• Large-scale magnetic topologies of late M dwarfs
• Confirmation of the Electron Cyclotron Maser Instability as the Dominant Source of Radio Emission from Very Low Mass Stars and Brown Dwarfs
• Periodic Bursts of Coherent Radio Emission from an Ultracool Dwarf
• Rotational Modulation of the Radio Emission from the M9 Dwarf TVLM 513-46546: Broadband Coherent Emission at the Substellar Boundary?
• Deciphering Solar Magnetic Activity I: On The Relationship Between The Sunspot Cycle And The Evolution Of Small Magnetic Features
• The Arecibo Detection of the Coolest Radio-flaring Brown Dwarf
• Simultaneous Multi-Wavelength Observations of Magnetic Activity in Ultracool Dwarfs. II. Mixed Trends in VB10 and LSR1835+32 and the Possible Role of Rotation
• Simultaneous Multi-Wavelength Observations of Magnetic Activity in Ultracool Dwarfs. I. The Complex Behavior of the M8.5 Dwarf TVLM513-46546
• Cyclic and Long-term Variation of Sunspot Magnetic Fields
• 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
• A Mini-survey of Ultracool Dwarfs at 4.9 GHz
• The Second Arecibo Search for 5 GHz Radio Flares from Ultracool Dwarfs
• Timing Analysis of the Periodic Radio and Optical Brightness Variations of the Ultracool Dwarf, TVLM 513-46546

Cited by in corpus (15)

• A Panchromatic View of Brown Dwarf Aurorae
• 154 MHz detection of faint, polarized flares from UV Ceti
• Monitoring the large-scale magnetic field of AD~Leo with SPIRou, ESPaDOnS and Narval. Toward a magnetic polarity reversal?
• An update of Leighton's solar dynamo model
• Periodic Radio Emission from the T8 Dwarf WISE J062309.94-045624.6
• The Rise of ROME. I. A Multiwavelength Analysis of the Star-Planet Interaction in the HD 189733 System
• Radio-flaring Ultracool Dwarf Population Synthesis
• Platform for Probing Radiation Transport Properties of Hydrogen at Conditions Found in the Deep Interiors of Red Dwarfs
• A BCool survey of stellar magnetic cycles
• Unravelling sub-stellar magnetospheres
• The Potential of Detecting Radio-flaring Ultracool Dwarfs at L band in the FAST Drift-scan Survey
• The Solar Neighborhood LII: M Dwarf Twin Binaries -- Presumed Identical Twins Appear Fraternal in Variability, Rotation, H$\alpha$, and X-rays
• Is WISEP J060738.65+242953.4 Really A Magnetically Active, Pole-on L Dwarf?
• Magnetic geometry of M dwarfs in the southern PLATO field
• Magnetism in the Brown Dwarf Regime