The large-scale magnetic field of Proxima Centauri near activity maximum

Klein, Baptiste; Donati, J.‐F.; Hébrard, E.; Zaire, B.; Folsom, C. P.; Morin, J.; Delfosse, X.; Bonfils, X.

doi:10.1093/mnras/staa3396

Cited by 32 publications

(48 citation statements)

References 66 publications

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“…Prox Cen is expected to have a relatively weak stellar wind, with a mass-loss rate of 𝑀 < 0.2 𝑀 (Wood et al 2001), where 𝑀 = 2×10 −14 𝑀 yr −1 is the solar wind mass-loss rate. The star also possesses a strong large-scale surface magnetic field of ∼ 200 G (Klein et al 2021). Its proximity to Earth along with its potentially habitable planet make it an interesting system to search for planet-induced radio emission.…”

Section: Introductionmentioning

confidence: 99%

Planet-induced radio emission from the coronae of M dwarfs: the case of Prox Cen and AU Mic

Kavanagh,

Vidotto,

Klein

et al. 2021

Preprint

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There have recently been detections of radio emission from low-mass stars, some of which are indicative of star-planet interactions. Motivated by these exciting new results, in this paper we present Alfvén wave-driven stellar wind models of the two active planet-hosting M dwarfs Prox Cen and AU Mic. Our models incorporate large-scale photospheric magnetic field maps reconstructed using the Zeeman-Doppler Imaging method. We obtain a mass-loss rate of 0.25 𝑀 for the wind of Prox Cen. For the young dwarf AU Mic, we explore two cases: a low and high mass-loss rate. Depending on the properties of the Alfvén waves which heat the corona in our wind models, we obtain mass-loss rates of 27 and 590 𝑀 for AU Mic. We use our stellar wind models to assess the generation of electron cyclotron maser instability emission in both systems, through a mechanism analogous to the sub-Alfvénic Jupiter-Io interaction. For Prox Cen we do not find any feasible scenario where the planet can induce radio emission in the star's corona, as the planet orbits too far from the star in the super-Alfvénic regime. However, in the case that AU Mic has a stellar wind mass-loss rate of 27 𝑀 , we find that both planets b and c in the system can induce radio emission from ∼ 10 MHz -3 GHz in the corona of the host star for the majority of their orbits, with peak flux densities of ∼ 10 mJy. Detection of such radio emission would allow us to place an upper limit on the mass-loss rate of the star.

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Section: Introductionmentioning

confidence: 99%

Planet-induced radio emission from the coronae of M dwarfs: the case of Prox Cen and AU Mic

Kavanagh,

Vidotto,

Klein

et al. 2021

Preprint

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“…Together with the results of Lafarga et al (2021), the K I line studied here appears to provide a powerful indicator of the changing photospheric magnetic field on these stars, which may be expected to perform well as a tracer of rotational modulation, and as an RV activity indicator. Recently, Klein et al (2021) used Zeeman Doppler Imaging to recover the magnetic field geometry of Proxima Centauri, an old, slowly-rotating, fully-convective star similar to GJ 699 and Teegarden's Star (albeit more active). They additionally found a significant rotational modulation in Stokes I spectra of Proxima Cen, and discuss the value of contrasting polarized and unpolarized indicators for diagnosing the properties of the dynamos of these fully-convective stars.…”

Section: Discussionmentioning

confidence: 99%

“…These effects have been leveraged to estimate the total magnetic fields of several M dwarfs (Shulyak et al 2019;Moutou et al 2017), and have also revealed apparent saturation behavior of the dynamo (Reiners et al 2009;Muirhead et al 2020). Measurements of unpolarized Zeeman signatures have even revealed rotational modulation in a small number of cases (Kochukhov & Lavail 2017;Klein et al 2021), and may contribute to the periodic variability observed in numerous lines in M dwarf spectra (Lafarga et al 2021).…”

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confidence: 99%

Rotational modulation of spectroscopic Zeeman signatures in low-mass stars

Terrien,

Keen,

Oda

et al. 2022

Preprint

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Accurate tracers of the stellar magnetic field and rotation are cornerstones for the study of M dwarfs and for reliable detection and characterization of their exoplanetary companions. Such measurements are particularly challenging for old, slowly rotating, fully convective M dwarfs. To explore the use of new activity and rotation tracers, we examined multi-year near-infrared spectroscopic monitoring of two such stars-GJ 699 (Barnard's Star) and Teegarden's Star-carried out with Habitable Zone Planet Finder spectrograph. We detected periodic variations in absorption line widths across the stellar spectrum with higher amplitudes towards longer wavelengths. We also detected similar variations in the strength and width of the 12435.67 Å neutral potassium (K I) line, a known tracer of the photospheric magnetic field. Attributing these variations to rotational modulation, we confirm the known 145 ± 15 d rotation period of GJ 699, and measure the rotation period of Teegarden's Star to be 99.6±1.4 d. Based on simulations of the K I line and the wavelength-dependence of the line width signal, we argue that the observed signals are consistent with varying photospheric magnetic fields and the associated Zeeman effect. These results highlight the value of detailed line profile measurements in the near-infrared for diagnosing stellar magnetic field variability. Such measurements may be pivotal for disentangling activity and exoplanet-related signals in spectroscopic monitoring of old, low-mass stars.

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“…The M dwarfs in our sample with spectropolarimetric constraints are EV Lac (Morin et al 2008b), YZ CMi (Morin et al 2008b), Proxima Cen (Klein et al 2021), andGJ 205 (Hébrard et al 2016). There are nine other stars in Table 3 with spectropolarimetric measurements.…”

Section: Relating ṁ and Magnetic Topologymentioning

confidence: 99%

New Observational Constraints on the Winds of M Dwarf Stars

Wood,

Mueller,

Redfield

et al. 2021

Preprint

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High resolution UV spectra of stellar H I Lyman-α lines from the Hubble Space Telescope (HST) provide observational constraints on the winds of coronal main sequence stars, thanks to an astrospheric absorption signature created by the interaction between the stellar winds and the interstellar medium. We report the results of a new HST survey of M dwarf stars, yielding six new detections of astrospheric absorption. We estimate mass-loss rates for these detections, and upper limits for nondetections. These new constraints allow us to characterize the nature of M dwarf winds and their dependence on coronal activity for the first time. For a clear majority of the M dwarfs, we find winds that are weaker or comparable in strength to that of the Sun, i.e. Ṁ ≤ 1 Ṁ⊙ . However, two of the M dwarfs have much stronger winds: YZ CMi (M4 Ve; Ṁ = 30 Ṁ⊙ ) and GJ 15AB (M2 V+M3.5 V; Ṁ = 10 Ṁ⊙ ). Even these winds are much weaker than expectations if the solar relation between flare energy and coronal mass ejection (CME) mass extended to M dwarfs. Thus, the solar flare/CME relation does not appear to apply to M dwarfs, with important ramifications for the habitability of exoplanets around M dwarfs. There is evidence for some increase in Ṁ with coronal activity as quantified by X-ray flux, but with much scatter. One or more other factors must be involved in determining wind strength besides spectral type and coronal activity, with magnetic topology being one clear possibility.

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The large-scale magnetic field of Proxima Centauri near activity maximum

Cited by 32 publications

References 66 publications

Planet-induced radio emission from the coronae of M dwarfs: the case of Prox Cen and AU Mic

Planet-induced radio emission from the coronae of M dwarfs: the case of Prox Cen and AU Mic

Rotational modulation of spectroscopic Zeeman signatures in low-mass stars

New Observational Constraints on the Winds of M Dwarf Stars

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