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

Route, Matthew

doi:10.3847/2041-8205/830/2/l27

Cited by 25 publications

(30 citation statements)

References 51 publications

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“…Such possible magnetic-polarity reversal, acting also in the case of the fast rotating UCDs, was claimed as the origin of the detection in different observing epochs of auroral pulses with opposite polarisation sense (Route 2016). Our analysis highlights that the planet-induced stellar auroral radio emission scenario is also able to explain this observational evidence.…”

Section: Planet-induced Auroral Emissionsupporting

confidence: 63%

“…Their magnetic dipole axis is tilted with respect to the rotational axis (oblique rotator model) (Babcock 1949). Furthermore, at the bottom of the main sequence, the signature of the auroral radio emission has been clearly identified in many very low mass stars and brown dwarfs, with spectral type ranging from M8 to T6.5 (Berger 2002;Burgasser & Putman 2005;Antonova et al 2008;Hallinan et al 2008;Route & Wolszczan 2012, 2016Williams et al 2015a;Burgasser et al 2015;Kao et al 2016).…”

Section: Introductionmentioning

confidence: 99%

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Probing the magnetosphere of the M8.5 dwarf TVLM 513−46546 by modelling its auroral radio emission. Hint of star exoplanet interaction?

Leto

Trigilio

Buemi

et al. 2017

Monthly Notices of the Royal Astronomical Society

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In this paper we simulate the cyclic circularly-polarised pulses of the ultra-cool dwarf TVLM 513-46546, observed with the VLA at 4.88 and 8.44 GHz on May 2006, by using a 3D model of the auroral radio emission from the stellar magnetosphere. During this epoch, the radio light curves are characterised by two pulses left-hand polarised at 4.88 GHz, and one doubly-peaked (of opposite polarisations) pulse at 8.44 GHz. To take into account the possible deviation from the dipolar symmetry of the stellar magnetic field topology, the model described in this paper is also able to simulate the auroral radio emission from a magnetosphere shaped like an offset-dipole. To reproduce the timing and pattern of the observed pulses, we explored the space of parameters controlling the auroral beaming pattern and the geometry of the magnetosphere. Through the analysis of the TVLM 513-46546 auroral radio emission, we derive some indications on the magnetospheric field topology that is able to simultaneously reproduce the timing and patterns of the auroral pulses measured at 4.88 and 8.44 GHz. Each set of model solutions simulates two auroral pulses (singly or doubly peaked) per period. To explain the presence of only one 8.44 GHz pulse per period, we analyse the case of auroral radio emission limited only to a magnetospheric sector activated by an external body, like the case of the interaction of Jupiter with its moons.

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Section: Planet-induced Auroral Emissionsupporting

confidence: 63%

Section: Introductionmentioning

confidence: 99%

Probing the magnetosphere of the M8.5 dwarf TVLM 513−46546 by modelling its auroral radio emission. Hint of star exoplanet interaction?

Leto

Trigilio

Buemi

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…Radio emission models of TVLM 513-46546 might show some indications of this behavior (Leto et al 2017). The long-term orbital variations may be responsible for the observed changes in pulse polarization observations, alternatively interpreted as a potential indication of stellar cycles in UCDs (Route 2016). For a single object hosting both of these electrodynamic engines, the co-rotation breakdown and a satellite flux tube, depending on the relative viewing geometry and underlying parameters, the observer might intercept both, none, or only one of the radio beam patterns of the ECMI emission.…”

Section: Auroral Beaming Geometry and Radio Emissionmentioning

confidence: 99%

A Panchromatic View of Brown Dwarf Aurorae

Pineda

Hallinan

Kao

2017

ApJ

118

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Stellar coronal activity has been shown to persist into the low-mass star regime, down to late M-dwarf spectral types. However, there is now an accumulation of evidence suggesting that at the end of the main sequence, there is a transition in the nature of the magnetic activity from chromospheric and coronal to planet-like and auroral, from local impulsive heating via flares and MHD wave dissipation to energy dissipation from strong large-scale magnetospheric current systems. We examine this transition and the prevalence of auroral activity in brown dwarfs through a compilation of multiwavelength surveys of magnetic activity, including radio, X-ray, and optical. We compile the results of those surveys and place their conclusions in the context of auroral emission as a consequence of large-scale magnetospheric current systems that accelerate energetic electron beams and drive the particles to impact the cool atmospheric gas. We explore the different manifestations of auroral phenomena, like Hα, in brown dwarf atmospheres and define their distinguishing characteristics. We conclude that large-amplitude photometric variability in the near-infrared is most likely a consequence of clouds in brown dwarf atmospheres, but that auroral activity may be responsible for long-lived stable surface features. We report a connection between auroral Hα emission and quiescent radio emission in electron cyclotron maser instability pulsing brown dwarfs, suggesting a potential underlying physical connection between quiescent and auroral emissions. We also discuss the electrodynamic engines powering brown dwarf aurorae and the possible role of satellites around these systems both to power the aurorae and seed the magnetosphere with plasma.

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“…I observed the HD 189733 system using the 305 m William E. Gordon radio telescope at Arecibo Observatory on 2011 September 7, for ∼7.2 ks, the time it takes for the target to transit the fixed dish. I monitored the system with the C-band receiver operating at 4.25-5.25 GHz with the same instrumental setup that has been used in my surveys of magnetized brown dwarf radio emission , 2016. The antenna gain and system temperatures were approximately 8 K Jy −1 and 30 K, respectively, at low zenith angles 1 .…”

Section: Radio Observationsmentioning

confidence: 99%

The Rise of ROME. I. A Multiwavelength Analysis of the Star–Planet Interaction in the HD 189733 System

Route

2019

ApJ

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Several "hot Jupiter" host stars appear to exhibit enhanced chromospheric activity, coronal flaring, and starspot development synchronized to their planetary orbits. These effects have been attributed to tidal and/or magnetic interactions between the star and exoplanet. The best studied among such systems is HD 189733, which has previously been observed from radio to X-ray wavelengths. Here, I present ∼4.75 GHz Arecibo radio telescope observations of HD 189733 during a fraction of the exoplanet orbital phase range previously associated with enhanced coronal X-ray flaring. No radio flares from the lower corona were detected. I also leverage Microvariability and Oscillations of Stars, Automated Photoelectric Telescope, and Wise photometry to measure the occurences of minima associated with enhanced starspot activity. The phasing of these minima with the exoplanet orbit does not reveal any synchronized active region behavior. Moreover, for the first time, I combine X-ray, ultraviolet, photometric, Ca II H&K, Hα, and radio observations of HD 189733 to conduct an extensive, holistic reexamination of stellar activity in this system. Through the presentation of new data, and by merging physical and statistical analytic approaches, I demonstrate that the previously asserted enhancements in activity, allegedly synchronized to certain exoplanet orbital phases, are likely the result of inadequately sampled intrinsic stellar activity from an active star, rather than star-planet interactions.

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

Cited by 25 publications

References 51 publications

Probing the magnetosphere of the M8.5 dwarf TVLM 513−46546 by modelling its auroral radio emission. Hint of star exoplanet interaction?

Probing the magnetosphere of the M8.5 dwarf TVLM 513−46546 by modelling its auroral radio emission. Hint of star exoplanet interaction?

A Panchromatic View of Brown Dwarf Aurorae

The Rise of ROME. I. A Multiwavelength Analysis of the Star–Planet Interaction in the HD 189733 System

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