Physical properties and astrometry of radio-emitting brown dwarf TVLM 513-46546 revisited

Gawroński, M.; Goździewski, Krzysztof

doi:10.1093/mnras/stw3329

Cited by 9 publications

(3 citation statements)

References 43 publications

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“…Finally, observations spanning 10 yr confirmed that the quiescent emission can be temporally stable (e.g. Hallinan et al 2006;Gawroński, Goździewski & Katarzyński 2017), though we note two exceptions in the existing literature where the L2.5 dwarf 2MASS J05233822−1403022 (Berger 2006;Antonova et al 2007;Berger et al 2010) and the M9.5 dwarf BRI 0021 (Berger et al 2010) show long term variability in the quiescent emission at C-band frequencies.…”

Section: O B S E Rvat I O N Ssupporting

confidence: 72%

Constraints on magnetospheric radio emission from Y dwarfs

Kao

Hallinan

Pineda

2019

Monthly Notices of the Royal Astronomical Society

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As a pilot study of magnetism in Y dwarfs, we have observed the three known infrared variable Y dwarfs WISE J085510.83−071442.5, WISE J140518.40+553421.4, and WISEP J173835.53+273258.9 with the NSF’s Karl G. Jansky Very Large Array in the 4–8 GHz frequency range. The aim was to investigate the presence of non-bursting quiescent radio emission as a proxy for highly circularly polarized radio emission associated with large-scale auroral currents. Measurements of magnetic fields on Y dwarfs may be possible by observing auroral radio emission, and such measurements are essential for constraining fully convective magnetic dynamo models. We do not detect any pulsed or quiescent radio emission, down to rms noise levels of 7.2 µJy for WISE J085510.83−071442.5, 2.2 µJy for WISE J140518.40+553421.4, and 3.2 µJy for WISEP J173835.53+273258.9. The fractional detection rate of radio emission from T dwarfs is ∼10 per cent suggesting that a much larger sample of deep observations of Y dwarfs is needed to rule out radio emission in the Y dwarf population. We discuss a framework that uses an empirical relationship between the auroral tracer Hα emission and quiescent radio emission to identify brown-dwarf auroral candidates. Finally, we discuss the implications that Y dwarf radio detections and non-detections can have for developing a picture of brown dwarf magnetism and auroral activity.

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Section: O B S E Rvat I O N Ssupporting

confidence: 72%

Constraints on magnetospheric radio emission from Y dwarfs

Kao

Hallinan

Pineda

2019

Monthly Notices of the Royal Astronomical Society

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“…Note that some objects have multiple observations in the same bandpass with both a detection and non-detection of O/IR variability. However, we do not expect the stability of O/IR variability to significantly impact the presence of quiescent radio emission, which observations confirm can persist for at least 10 yr (e.g., Hallinan et al 2006;Gawroński et al 2017), since the underlying driving mechanisms are different. In cases where data was re-examined, we defer to the updated results.…”

Section: Occurrence Rates Of Quiescent Radio Activitymentioning

confidence: 59%

On the Correlation between L Dwarf Optical and Infrared Variability and Radio Aurorae

Richey-Yowell

Kao

Pineda

et al. 2020

ApJ

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Photometric variability attributed to cloud phenomena is common in L/T transition brown dwarfs. Recent studies show that such variability may also trace aurorae, suggesting that localized magnetic heating may contribute to observed brown dwarf photometric variability. We assess this potential correlation with a survey of 17 photometrically variable brown dwarfs using the Karl G. Jansky Very Large Array at 4-8 GHz. We detect quiescent and highly circularly polarized flaring emission from one source, 2MASS J17502484-0016151, which we attribute to auroral electron cyclotron maser emission. The detected auroral emission extends throughout the frequency band at ∼5-25σ, and we do not detect evidence of a cutoff. Our detection confirms that 2MASS J17502484-0016151 hosts a magnetic field strength of 2.9 kG, similar to those of other radio-bright ultracool dwarfs. We show that Hα emission continues to be an accurate tracer of auroral activity in brown dwarfs. Supplementing our study with data from the literature, we calculate the occurrence rates of quiescent emission in L dwarfs with low-and high-amplitude variability and conclude that high-amplitude optical and infrared variability does not trace radio magnetic activity in L dwarfs.

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“…We optimized the astrometric model with the same approach as presented in Gawroński et al (2017). Uncertainties of the model parameters ξ ξ ξ = (α 0 , δ 0 , µ α , µ δ , π) depend on complex way on the residual phase in phase-referencing, sub-mas changes of the phase calibrator radio structures and the atmospheric zenith delay residuals.…”

Section: Astrometric Model and An Estimate Of The Absolute Parallaxmentioning

confidence: 99%

Another look at AM Herculis – radio-astrometric campaign with the e-EVN at 6 cm

Gawroński

Goździewski

Rycyk

2018

Monthly Notices of the Royal Astronomical Society

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We conducted radio-interferometric observations of the well known binary cataclysmic system AM Herculis. This particular system is formed by the magnetic white dwarf (primary) and the red dwarf (secondary), and is the prototype of so-called polars. Our observations were conducted with the European VLBI Network (EVN) in the e-EVN mode at 5 GHz. We obtained six astrometric measurements spanning one year, which make it possible to update the annual parallax for this system with the best precision to date (π = 11.29 ± 0.08 mas), equivalent to the distance of 88.6 ± 0.6 pc. The system was observed mostly in the quiescent phase (visual magnitude m v ∼ 15.3), when the radio emission was at the level of about 300 µJy. Our analysis suggests that the radio flux of AM Herculis is modulated with the orbital motion. Such specific properties of the radiation can be explained using the emission mechanism similar to the scenario proposed for V471 Tau and, in general, for RS CVn type stars. In this scenario the radio emission arises near the surface of the red dwarf, where the global magnetic field strength may reach a few kG. We argue that the quiescent radio emission distinguishes AM Herculis together with AR Ursae Majoris (the second known persistent radio polar) from other polars, as the systems with a magnetized secondary star.

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Physical properties and astrometry of radio-emitting brown dwarf TVLM 513-46546 revisited

Cited by 9 publications

References 43 publications

Constraints on magnetospheric radio emission from Y dwarfs

Constraints on magnetospheric radio emission from Y dwarfs

On the Correlation between L Dwarf Optical and Infrared Variability and Radio Aurorae

Another look at AM Herculis – radio-astrometric campaign with the e-EVN at 6 cm

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