Radio masers on WX UMa: hints of a Neptune-sized planet, or magnetospheric reconnection?

Kavanagh, Robert D.; Vidotto, A. A.; Vedantham, H. K.; Jardine, M.; Callingham, J. R.; Morin, J.

doi:10.1093/mnras/stac1264

Cited by 12 publications

(21 citation statements)

References 76 publications

(121 reference statements)

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“…The V-LoTSS M-dwarf sample is composed of stars at all coronal and chromospheric activity levels, as well as slow and fast rotators (Callingham et al 2021b). In particular, it has been suggested that the highly circularly polarised radio emission from the inactive, slow-rotating M dwarfs in this sample is evidence of a sub-Alfvénic interaction between a star and a putative planet (Vedantham et al 2020b;Callingham et al 2021b;Pope et al 2021;Kavanagh et al 2022). For the more active M dwarfs, the circularly polarised radio emission could be generated by plasma processes or ECMI via the breakdown of co-rotation (Callingham et al 2021a).…”

Section: Galactic Non-degenerate Circularly Polarised Sourcesmentioning

confidence: 82%

“…LoTSS will cover the entire northern sky with an unprecedented root-mean-square (rms) noise of ≈100 µJy beam −1 in full-Stokes polarisation. The unique discovery space that LoTSS provides has already been exemplified by the several studies already published that use preliminary Stokes V data, such as the first direct detection of a brown dwarf from its radio properties (Vedantham et al 2020a), the inference of a star-planet interaction (Vedantham et al 2020b;Kavanagh et al 2022), long-term auroral emission from an active M-dwarf system (Callingham et al 2021a), evidence of closed-field lines extending to large stellar radii around an M-dwarf (Davis et al 2021), new pulsars missed in previous time-domain searches (Sobey et al 2022), and coherent emission detected from chromospherically active binaries (Toet et al 2021).…”

Section: Introductionmentioning

confidence: 99%

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V-LoTSS: The circularly polarised LOFAR Two-metre Sky Survey

Callingham

Shimwell

Vedantham

et al. 2023

A&A

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We present the detection of 68 sources from the most sensitive radio survey in circular polarisation conducted to date. We used the second data release of the 144 MHz LOFAR Two-metre Sky Survey to produce circularly polarised maps with a median noise of 140 µJy beam−1 and resolution of 20″ for ≈27% of the northern sky (5634 deg2). The leakage of total intensity into circular polarisation is measured to be ≈0.06%, and our survey is complete at flux densities ≥1 mJy. A detection is considered reliable when the circularly polarised fraction exceeds 1%. We find the population of circularly polarised sources is composed of four distinct classes: stellar systems, pulsars, active galactic nuclei, and sources unidentified in the literature. The stellar systems can be further separated into chromospherically active stars, M dwarfs, and brown dwarfs. Based on the circularly polarised fraction and lack of an optical counterpart, we show it is possible to infer whether the unidentified sources are likely unknown pulsars or brown dwarfs. By the completion of this survey of the northern sky, we expect to detect 300±100 circularly polarised sources.

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Section: Galactic Non-degenerate Circularly Polarised Sourcesmentioning

confidence: 82%

Section: Introductionmentioning

confidence: 99%

V-LoTSS: The circularly polarised LOFAR Two-metre Sky Survey

Callingham

Shimwell

Vedantham

et al. 2023

A&A

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“…The proximity of hot Jupiters to their host stars can potentially cause sub-Alfvénic SPIs, which is expected to produce observable signatures in the stellar atmosphere (e.g., chromospheric emission Ca II H & K line emission; Shkolnik et al 2003Shkolnik et al , 2008Cauley et al 2019) or the planetary atmosphere (e.g., auroral radio emission; Cohen et al 2018;Turnpenney et al 2018;Bastian et al 2022;Kavanagh et al 2021Kavanagh et al , 2022. Such magnetic SPIs in exoplanetary systems were excessively studied by means of magnetohydrodynamic (MHD) simulations (e.g., Preusse et al 2006Preusse et al , 2007Zhilkin & Bisikalo 2020;Varela et al 2018Varela et al , 2022, partly with a focus on the far-field interaction and incorporating self-consistent stellar wind models (e.g., Strugarek et al 2014Strugarek et al , 2019aCohen et al 2011Cohen et al , 2014Vidotto et al 2015;Vidotto & Donati 2017).…”

Section: Introductionmentioning

confidence: 99%

Space environment and magnetospheric Poynting fluxes of the exoplanet τ Boötis b

Elekes

Saur

2023

A&A

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Context. The first tentative detection of a magnetic field on the hot-Jupiter-type exoplanet τ Boötis b was recently reported by Turner et al. (A&A, 645, A59). The magnetic field was inferred from observations of circularly polarized radio emission obtained with the LOFAR telescopes. The observed radio emission is possibly a consequence of the interaction of the surrounding stellar wind with the planet's magnetic field. Aims. We aim to better understand the near space environment of τ Boötis b and to shed light on the structure and energetics of its near-field interaction with the stellar wind. We are particularly interested in understanding the magnetospheric energy fluxes powered by the star-planet interaction and in localizing the source region of possible auroral radio emission. Methods. We performed magnetohydrodynamic simulations of the space environment around τ Boötis b and its interaction with the stellar wind using the PLUTO code. We investigated the magnetospheric energy fluxes and effects of different magnetic field orientations in order to understand the physical processes that cause the energy fluxes that may lead to the observed radio emission given the magnetic field strength proposed in Turner et al. (A&A, 645, A59). Furthermore, we study the effect of various stellar wind properties, such as density and pressure, on magnetospheric energy fluxes given the uncertainty of extrasolar stellar wind predictions. Results. We find in our simulations that the interaction is most likely super-Alfvénic and that energy fluxes generated by the stellar wind-planet interaction are consistent with the observed radio powers. Magnetospheric Poynting fluxes are on the order of 1–8 × 1018 W for hypothetical open, semi-open, and closed magnetospheres. These Poynting fluxes are energetically consistent with the radio powers in Turner et al. (A&A, 645, A59) for a magnetospheric Poynting flux-to-radio efficiency >10−3 when the magnetic fields of the planet and star are aligned. In the case of lower efficiency factors, the magnetospheric radio emission scenario is, according to the parameter space modeled in this study, not powerful enough. A sub-Alfvénic interaction with decreased stellar wind density could channel Poynting fluxes on the order of 1018W toward the star. In the case of a magnetic polarity reversal of the host star from an aligned to anti-aligned field configuration, the expected radio powers in the magnetospheric emission scenario fall below the observable threshold. Furthermore, we constrain the possible structure of the auroral oval to a narrow band near the open-closed field line boundary. The strongest emission is likely to originate from the night side of the planet. More generally, we find that stellar wind variability in terms of density and pressure does significantly influence magnetospheric energy fluxes for close-in magnetized exoplanets.

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“…chromospheric emission Ca II H & K line emission Shkolnik et al 2003Shkolnik et al , 2008Cauley et al 2019) or the planetary atmosphere (e.g. auroral radio emission Cohen et al 2018;Turnpenney et al 2018;Bastian et al 2022;Kavanagh et al 2021Kavanagh et al , 2022. Such magnetic SPI in exoplanetary systems were excessively studied by means of magnetohydrodynamic simulations (e.g.…”

Section: Introductionmentioning

confidence: 99%

Space environment and magnetospheric Poynting fluxes of the exoplanet $τ$ Boötis b

Elekes¹,

Saur²

2023

Preprint

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Context. The first tentative detection of a magnetic field on the Hot Jupiter type exoplanet τ Boötis b was recently reported by Turner et al. (2021). The magnetic field was inferred from observations of circularly-polarized radio emission obtained with the LOFAR telescopes. The observed radio emission is possibly a consequence of the interaction of the surrounding stellar wind with the planet's magnetic field. Aims. We aim to better understand the near space environment of τ Boötis b and to shed light on the structure and energetics of its near-field interaction with the stellar wind. We are particularly interested in understanding the magnetospheric energy fluxes powered by the star-planet interaction and in localizing the source region of possible auroral radio emission. Methods. We perform magnetohydrodynamic simulations of the space environment around τ Boötis b and its interaction with the stellar wind using the PLUTO code. We investigate the magnetospheric energy fluxes and effects of different magnetic field orientations in order to understand the physical processes which cause energy fluxes that may lead to the observed radio emission given the proposed magnetic field strength in Turner et al. ( 2021). Furthermore we study the effect of various stellar wind properties, such as density and pressure, on magnetospheric energy fluxes given the uncertainty of extrasolar stellar wind predictions. Results. We find in our simulations that the interaction is most likely super-Alfvénic and energy fluxes generated by the stellar windplanet interaction are consistent with the observed radio powers. Magnetospheric Poynting fluxes are of the order of 1-8 ×10 18 W for hypothetical open, semi-open and closed magnetospheres. These Poynting fluxes are energetically consistent with the radio powers in Turner et al. ( 2021) for a magnetospheric Poynting flux-to-radio efficiency > 10 −3 when the magnetic fields of the planet and star are aligned. In case of lower efficiency factors the magnetospheric radio emission scenario is according to the parameter space modeled in this study not powerful enough. A sub-Alfvénic interaction with decreased stellar wind density could channel Poynting fluxes on the order of 10 18 W towards the star. In case of a magnetic polarity reversal of the host star from an aligned to anti-aligned field configuration, expected radio powers in the magnetospheric emission scenario fall below the observable threshold. Furthermore we constrain the possible structure of the auroral oval to a narrow band near the open-closed field line boundary. Strongest emission is likely to originate from the night side of the planet. More generally, we find that stellar wind variability in terms of density and pressure does influence magnetospheric energy fluxes significantly for close-in magnetized exoplanets.

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Radio masers on WX UMa: hints of a Neptune-sized planet, or magnetospheric reconnection?

Cited by 12 publications

References 76 publications

V-LoTSS: The circularly polarised LOFAR Two-metre Sky Survey

V-LoTSS: The circularly polarised LOFAR Two-metre Sky Survey

Space environment and magnetospheric Poynting fluxes of the exoplanet τ Boötis b

Space environment and magnetospheric Poynting fluxes of the exoplanet $τ$ Boötis b

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