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.

arXiv commentAccepted to ApJL; 6 pages, 1 table

References in corpus (36)

• Theory of Low-Mass Stars and Substellar Objects
• 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
• Activity in Very Cool Stars: Magnetic Dissipation in late-M and L Dwarf Atmospheres
• Periodic Bursts of Coherent Radio Emission from an Ultracool Dwarf
• Large-scale alpha^2-dynamo in low-mass stars and brown dwarfs
• Multiple and changing cycles of active stars II. Results
• Flaring Up All Over -- Radio Activity in Rapidly-Rotating Late-Type M and L Dwarfs
• The stable magnetic field of the fullly-convective star V374 Peg
• 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?
• H-alpha Activity of Old M Dwarfs: Stellar Cycles and Mean Activity Levels For 93 Low-Mass Stars in the Solar Neighborhood
• Auroral radio emission from late L and T dwarfs: A new constraint on dynamo theory in the substellar regime
• The Radio Activity-Rotation Relation of Ultracool 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
• Deciphering Solar Magnetic Activity I: On The Relationship Between The Sunspot Cycle And The Evolution Of Small Magnetic Features
• Quiescent Radio Emission from Southern Late-type M Dwarfs and a Spectacular Radio Flare from the M8 Dwarf DENIS 1048-3956
• Buoyant Magnetic Loops Generated by Global Convective Dynamo Action
• 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
• A Survey for H-alpha Emission from Late L dwarfs and T dwarfs
• Looking for a Pulse: A search for Rotationally Modulated Radio Emission from the Hot Jupiter, Tau Bootis b
• Periodic Radio Emission from the M7 Dwarf 2MASS J13142039+1320011: Implications for the Magnetic Field Topology
• 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
• 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
• A Mini-survey of Ultracool Dwarfs at 4.9 GHz
• Magnetic fields in fully convective M-dwarfs: oscillatory dynamos vs bistability
• The Second Arecibo Search for 5 GHz Radio Flares from Ultracool Dwarfs
• The 5 GHz Arecibo Search for Radio Flares from Ultracool Dwarfs
• Spin-orbit alignment in the very low mass binary regime: The L dwarf tight binary 2MASSW J0746425+200032AB
• Timing Analysis of the Periodic Radio and Optical Brightness Variations of the Ultracool Dwarf, TVLM 513-46546

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