Radio Emission from Binary Ultracool Dwarf Systems

Kao, Melodie M.; Pineda, J. Sebastian

doi:10.3847/1538-4357/ac660b

Cited by 8 publications

(3 citation statements)

References 79 publications

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“…As noted above, the ultracool dwarfs are the closest thing to giant planets that have been detected in the radio. The radio luminosities of nine quiescent binary ultracool dwarf systems discussed by Kao & Sebastian Pineda (2022) are in the range of 10 11.9−14.6 erg s −1 Hz −1 . JuMBO 24 has a radio luminosity of 10 16.0 erg s −1 Hz −1 .…”

Section: Nature Of the Radio Emissionmentioning

confidence: 98%

“…The objects with known radio emission that are more similar to the components of the JuMBOs are the ultracool dwarfs (Kao & Sebastian Pineda 2022). The radio emission from the latter objects has two main components: a periodically bursting emission arising in aurorae and a slowly varying, quiescent emission with a low degree of circular polarization arising from a structure similar in morphology to the Jovian radiation belts (Climent et al 2023;Kao et al 2023).…”

Section: Nature Of the Radio Emissionmentioning

confidence: 99%

“…We have searched for radio counterparts to the 42 JuMBOs in Orion using sensitive observations from the archive of the Karl G. Jansky Very Large Array (VLA) of the National Radio Astronomy Observatory (NRAO). Here we report the radio detection of JuMBO 24 in three epochs distributed across a decade, in 2012, 2018, and 2022 Letter is organized as follows. In Section 2 we present the observations, while in Section 3 we discuss the implications of this detection.…”

Section: Introductionmentioning

confidence: 99%

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A Radio Counterpart to a Jupiter-mass Binary Object in Orion

Rodríguez,

Loinard,

Zapata

2024

ApJL

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Using James Webb Space Telescope near-infrared data of the inner Orion Nebula, Pearson & McCaughrean detected 40 Jupiter-mass binary objects (JuMBOs). These systems are not associated with stars and their components have masses of giant Jupiter-like planets and separations in the plane of the sky of order ∼100 au. The existence of these wide free-floating planetary-mass binaries was unexpected in our current theories of star and planet formation. Here we report the radio continuum (6.1 and 10.0 GHz) Karl G. Jansky Very Large Array detection of a counterpart to JuMBO 24. The radio emission appears to be steady at a level of ∼50 μJy over timescales of days and years. We set an upper limit of ≃15 km s−1 to the velocity of the radio source in the plane of the sky. As in the near-infrared, the radio emission seems to be coming from both components of the binary.

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Section: Nature Of the Radio Emissionmentioning

confidence: 98%

Section: Nature Of the Radio Emissionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Radio Counterpart to a Jupiter-mass Binary Object in Orion

Rodríguez,

Loinard,

Zapata

2024

ApJL

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Polarised radio pulsations from a new T-dwarf binary

Vedantham¹,

Evans²,

Callingham³

et al. 2023

A&A

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Brown dwarfs display Jupiter-like auroral phenomena such as magnetospheric Hα emission and coherent radio emission. Coherent radio emission is a probe of magnetospheric acceleration mechanisms and it provides a direct measurement of the magnetic field strength at the emitter’s location, both of which are difficult to access by other means. Observations of the coldest brown dwarfs (spectral types T and Y) are particularly interesting as their magnetospheric phenomena may be very similar to those in gas-giant exoplanets. Here we present 144 MHz radio and infrared adaptive optics observations of the brown dwarf WISEP J101905.63+652954.2 made using the Low Frequency Array (LOFAR) and Keck telescopes, respectively. The radio data show pulsed, highly circularly polarised emission which yields a rotation rate of 0.32 ± 0.03 h−1. The infrared imaging reveals the source to be a binary with a projected separation of 423.0 ± 1.6 mas between components of spectral type T5.5 ± 0.5 and T7.0 ± 0.5. With a simple ‘toy model’, we show that the radio emission can, in principle, be powered by the interaction between the two dwarfs with a mass-loss rate of at least 25 times the Jovian value. WISEP J101905.63+652954.2 is interesting because it is the first pulsed methane dwarf detected in a low radio-frequency search. Unlike previous gigahertz-frequency searches that were only sensitive to objects with kiloGauss fields, our low-frequency search is sensitive to surface magnetic fields of ≈50 G and above which might reveal the coldest radio-loud objects down to planetary mass scales.

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Phenomenology and periodicity of radio emission from the stellar system AU Microscopii

Bloot,

Callingham,

Vedantham

et al. 2024

A&A

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Stellar radio emission can measure a star's magnetic field strength and structure, plasma density, and dynamics, and the stellar wind pressure impinging on exoplanet atmospheres. However, properly interpreting the radio data often requires temporal baselines that cover the rotation of the stars, orbits of their planets, and any longer-term stellar activity cycles. Here we present our monitoring campaign on the young, active M\,dwarf AU\,Microscopii with the Australia Telescope Compact Array between 1.1 and 3.1\,GHz. With over 250 hours of observations, these data represent the longest radio monitoring campaign on a single main-sequence star to date. We find that AU\,Mic produces a wide variety of radio emission, for which we introduce a phenomenological classification scheme predicated on the polarisation fraction and time-frequency structure of the emission. Such a classification scheme is applicable to radio emission from other radio-bright stars. The six types of radio emission detected on AU\,Mic can be broadly categorised into five distinct types of bursts, and broadband quiescent emission. We find that the radio bursts are highly circularly polarised and periodic with the rotation period of the star, implying that the emission is beamed. It is therefore most likely produced by the electron cyclotron maser instability. We present a model to show that the observed pattern of emission can be explained by emission from auroral rings on the magnetic poles. The total intensity of the broadband emission is stochastic, but we show that its circular polarisation fraction is also periodic with the rotation of the star. Such a periodicity in the polarised fraction of emission has not been observed on an M\,dwarf before. We present a qualitative model to describe the periodicity in the polarisation fraction of the broadband emission, using low-harmonic gyromagnetic emission. Using a simple qualitative model, we infer a magnetic obliquity of at least 20 from the observed variation in polarisation fraction. Finally, we show that the radio emission might be evolving on long timescales, hinting at a potential stellar magnetic activity cycle.

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Radio Emission from Binary Ultracool Dwarf Systems

Cited by 8 publications

References 79 publications

A Radio Counterpart to a Jupiter-mass Binary Object in Orion

A Radio Counterpart to a Jupiter-mass Binary Object in Orion

Polarised radio pulsations from a new T-dwarf binary

Phenomenology and periodicity of radio emission from the stellar system AU Microscopii

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