The magnetic field and multiple planets of the young dwarf AU~Mic
2023
Online
report
In this paper we present an analysis of near-infrared spectropolarimetric and velocimetric data of the young M dwarf AU Mic, collected with SPIRou at the Canada-France-Hawaii telescope from 2019 to 2022, mostly within the SPIRou Legacy Survey. With these data, we study the large- and small-scale magnetic field of AU Mic, detected through the unpolarized and circularly-polarized Zeeman signatures of spectral lines. We find that both are modulated with the stellar rotation period (4.86 d), and evolve on a timescale of months under differential rotation and intrinsic variability. The small-scale field, estimated from the broadening of spectral lines, reaches $2.61\pm0.05$ kG. The large-scale field, inferred with Zeeman-Doppler imaging from Least-Squares Deconvolved profiles of circularly-polarized and unpolarized spectral lines, is mostly poloidal and axisymmetric, with an average intensity of $550\pm30$ G. We also find that surface differential rotation, as derived from the large-scale field, is $\simeq$30% weaker than that of the Sun. We detect the radial velocity (RV) signatures of transiting planets b and c, although dwarfed by activity, and put an upper limit on that of candidate planet d, putatively causing the transit-timing variations of b and c. We also report the detection of the RV signature of a new candidate planet (e) orbiting further out with a period of $33.39\pm0.10$ d, i.e., near the 4:1 resonance with b. The RV signature of e is detected at 6.5$\sigma$ while those of b and c show up at $\simeq$4$\sigma$, yielding masses of $10.2^{+3.9}_{-2.7}$ and $14.2^{+4.8}_{-3.5}$ Earth masses for b and c, and a minimum mass of $35.2^{+6.7}_{-5.4}$ Earth masses for e.
Comment: MNRAS, in press (20 pages and 12 figures + 9 pages of supplementary material)
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The magnetic field and multiple planets of the young dwarf AU~Mic
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Autor/in / Beteiligte Person: | Donati, J. F. ; Cristofari, P. I. ; Finociety, B. ; Klein, B. ; Moutou, C. ; Gaidos, E. ; Cadieux, C. ; Artigau, E. ; Correia, A. C. M. ; Boué, G. ; Cook, N. J. ; Carmona, A. ; Lehmann, L. T. ; Bouvier, J. ; Martioli, E. ; Morin, J. ; Fouqué, P. ; Delfosse, X. ; Royon, R. ; Hébrard, G. ; Alencar, S. H. P. ; Laskar, J. ; Arnold, L. ; Petit, P. ; Kospal, A. ; Vidotto, A. ; Folsom, C. P. ; collaboration, the SLS |
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Veröffentlichung: | 2023 |
Medientyp: | report |
DOI: | 10.1093/mnras/stad1193 |
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