000132872 001__ 132872
000132872 005__ 20240315113108.0
000132872 0247_ $$2doi$$a10.1051/0004-6361/202348065
000132872 0248_ $$2sideral$$a137688
000132872 037__ $$aART-2024-137688
000132872 041__ $$aeng
000132872 100__ $$aBloot, S.
000132872 245__ $$aPhenomenology and periodicity of radio emission from the stellar system AU Microscopii
000132872 260__ $$c2024
000132872 5060_ $$aAccess copy available to the general public$$fUnrestricted
000132872 5203_ $$aStellar 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.
000132872 536__ $$9info:eu-repo/grantAgreement/ES/AEI/PID2020-117404GB-C22$$9info:eu-repo/grantAgreement/ES/MICINN-AEI/PRTR-C17.I1$$9info:eu-repo/grantAgreement/ES/MICINN/CEX2021-001131-S$$9info:eu-repo/grantAgreement/ES/MICINN/PID2020-117404GB-C21$$9info:eu-repo/grantAgreement/ES/MICINN PRE2020-095421
000132872 540__ $$9info:eu-repo/semantics/openAccess$$aby$$uhttp://creativecommons.org/licenses/by/3.0/es/
000132872 655_4 $$ainfo:eu-repo/semantics/article$$vinfo:eu-repo/semantics/publishedVersion
000132872 700__ $$aCallingham, J. R.
000132872 700__ $$aVedantham, H. K.
000132872 700__ $$aKavanagh, R. D.
000132872 700__ $$aPope, B. J. S.
000132872 700__ $$aCliment, J. B.
000132872 700__ $$aGuirado, J. C.
000132872 700__ $$aPeña-Moñino, L.
000132872 700__ $$0(orcid)0000-0001-5654-0266$$aPérez-Torres, M.
000132872 773__ $$g682, A170 (2024), 1-16$$pAstron. astrophys.$$tAstronomy and Astrophysics$$x0004-6361
000132872 8564_ $$s6032943$$uhttps://zaguan.unizar.es/record/132872/files/texto_completo.pdf$$yVersión publicada
000132872 8564_ $$s3380459$$uhttps://zaguan.unizar.es/record/132872/files/texto_completo.jpg?subformat=icon$$xicon$$yVersión publicada
000132872 909CO $$ooai:zaguan.unizar.es:132872$$particulos$$pdriver
000132872 951__ $$a2024-03-15-08:51:43
000132872 980__ $$aARTICLE