Phenomenology and periodicity of radio emission from the stellar system AU Microscopii
Article
Bloot, S., Callingham, J. R., Vedantham, H. K., Kavanagh, R. D,, Pope, B. J. S., Climent, J. B., Guirado, J. C., Peña-Moñino, L. and Pérez-Torres, M.. 2024. "Phenomenology and periodicity of radio emission from the stellar system AU Microscopii." Astronomy and Astrophysics: a European journal. 682. https://doi.org/10.1051/0004-6361/202348065
| Article Title | Phenomenology and periodicity of radio emission from the stellar system AU Microscopii |
|---|---|
| ERA Journal ID | 1050 |
| Article Category | Article |
| Authors | Bloot, S., Callingham, J. R., Vedantham, H. K., Kavanagh, R. D,, Pope, B. J. S., Climent, J. B., Guirado, J. C., Peña-Moñino, L. and Pérez-Torres, M. |
| Journal Title | Astronomy and Astrophysics: a European journal |
| Journal Citation | 682 |
| Article Number | A170 |
| Number of Pages | 16 |
| Year | 2024 |
| Publisher | EDP Sciences |
| Place of Publication | France |
| ISSN | 0004-6361 |
| 1432-0746 | |
| Digital Object Identifier (DOI) | https://doi.org/10.1051/0004-6361/202348065 |
| Web Address (URL) | https://www.aanda.org/articles/aa/full_html/2024/02/aa48065-23/aa48065-23.html |
| Abstract | 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 h 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. |
| Keywords | radio continuum: stars |
| Contains Sensitive Content | Does not contain sensitive content |
| ANZSRC Field of Research 2020 | 5101. Astronomical sciences |
| Byline Affiliations | Netherlands Institute for Radio Astronomy, Netherlands |
| University of Groningen, Netherlands | |
| Leiden University, Netherlands | |
| Centre for Astrophysics | |
| University of Queensland | |
| Polytechnic University of Valencia, Spain | |
| Valencian International University, Spain | |
| Institute of Astrophysics of Andalusia, Spain | |
| University of Zaragoza, Spain | |
| European University Cyprus, Cyprus |
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https://research.usq.edu.au/item/z5qq5/phenomenology-and-periodicity-of-radio-emission-from-the-stellar-system-au-microscopii
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