Modelling the RV jitter of early-M dwarfs using tomographic imaging

Hébrard, E.; Donati, J.‐F.; Delfosse, X.; Morin, J.; Moutou, C.; Boisse, I.

doi:10.1093/mnras/stw1346

Cited by 85 publications

(95 citation statements)

References 49 publications

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“…Zeeman Doppler Imaging (ZDI) studies (e.g. Morin et al 2008;Petit et al 2008;Fares et al 2009;Vidotto et al 2014b;Jeffers et al 2014;See et al 2015See et al , 2016Folsom et al 2016;Hébrard et al 2016;See et al 2017), provide information on the large scale surface magnetic fields of active stars. Observations have shown stellar magnetic fields to be much more complex than simple dipoles, containing combinations of many different field modes.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Combined Magnetic Geometries on Thermally Driven Winds. I. Interaction of Dipolar and Quadrupolar Fields

Finley

2017

ApJ

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Cool stars with outer convective envelopes are observed to have magnetic fields with a variety of geometries, which on large scales are dominated by a combination of the lowest order fields such as the dipole, quadrupole and octupole modes. Magnetised stellar wind outflows are primarily responsible for the loss of angular momentum from these objects during the main sequence. Previous works have shown the reduced effectiveness of the stellar wind braking mechanism with increasingly complex, but singular, magnetic field geometries. In this paper, we quantify the impact of mixed dipolar and quadrupolar fields on the spin-down torque using 50 MHD simulations with mixed field, along with 10 of each pure geometries. The simulated winds include a wide range of magnetic field strength and reside in the slow-rotator regime. We find that the stellar wind braking torque from our combined geometry cases are well described by a broken power law behaviour, where the torque scaling with field strength can be predicted by the dipole component alone or the quadrupolar scaling utilising the total field strength. The simulation results can be scaled and apply to all main-sequence cool stars. For Solar parameters, the lowest order component of the field (dipole in this paper) is the most significant in determining the angular momentum loss.

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Section: Introductionmentioning

confidence: 99%

The Effect of Combined Magnetic Geometries on Thermally Driven Winds. I. Interaction of Dipolar and Quadrupolar Fields

Finley

2017

ApJ

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“…This technique has now successfully mapped the large-scale surface field of hundreds of cool, pre-mainsequence and main-sequence stars [e.g., 15]. Due to the increasing sample of stars with mapped fields, several trends are emerging [13,[15][16][17][18][19]. For example, it has been shown that the topology of surface magnetic fields depends on the internal structure, where fully convective stars present mainly poloidal fields [17,18] as compared to stars that have a radiative core.…”

Section: Stellar Surface Magnetism: Brief Overview Of Its Latest Resultsmentioning

confidence: 99%

Stellar magnetic activity and exoplanets

Vidotto¹

2017

EPJ Web Conf.

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Abstract. It has been proposed that magnetic activity could be enhanced due to interactions between close-in massive planets and their host stars. In this article, I present a brief overview of the connection between stellar magnetic activity and exoplanets. Stellar activity can be probed in chromospheric lines, coronal emission, surface spot coverage, etc. Since these are manifestations of stellar magnetism, these measurements are often used as proxies for the magnetic field of stars. Here, instead of focusing on the magnetic proxies, I overview some recent results of magnetic field measurements using spectropolarimetric observations. Firstly, I discuss the general trends found between large-scale magnetism, stellar rotation, and coronal emission and show that magnetism seems to be correlated to the internal structure of the star. Secondly, I overview some works that show evidence that exoplanets could (or not) act as to enhance the activity of their host stars.

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“…Zeeman broadening of spectral features in unpolarized light occurs in the presence of strong magnetic fields that cause Zeeman splitting; an effect that grows with wavelength. Reiners et al (2013) and Hébrard et al (2014) used polarized radiative transfer at nIR wavelengths to compute the effect of Zeeman splitting from both atomic and molecular sources on stellar line profiles. Reiners et al (2013) report the following simplified model for the RV signal resulting from Zeeman broadening in M dwarfs (T eff ∈ [2800, 3700] K)…”

Section: Zeeman Broadeningmentioning

confidence: 99%

“…The empirical distribution of this quantity in M dwarfs is incomplete despite contributions from various observing campaigns (e.g. Reiners & Basri 2007;Shulyak et al 2014;Hébrard et al 2016;Moutou et al 2017;Shulyak et al 2017). Instead of sampling Bf from an empirical distribution, we use an ad hoc method of sampling Bf which exploits what is known about small-scale Bf fields in M dwarfs as a function of spectral type and rotation.…”

Section: Zeeman Broadeningmentioning

confidence: 99%

See 1 more Smart Citation

Predictions of Planet Detections with Near-infrared Radial Velocities in the Upcoming SPIRou Legacy Survey-planet Search

Cloutier¹,

Artigau²,

Delfosse³

et al. 2018

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The SPIRou near infrared spectro-polarimeter is destined to begin science operations at the CanadaFrance-Hawaii Telescope in mid-2018. One of the instrument's primary science goals is to discover the closest exoplanets to the Solar System by conducting a 3-5 year long radial velocity survey of nearby M dwarfs at an expected precision of ∼ 1 m s −1 ; the SPIRou Legacy Survey-Planet Search (SLS-PS). In this study we conduct a detailed Monte-Carlo simulation of the SLS-PS using our current understanding of the occurrence rate of M dwarf planetary systems and physical models of stellar activity. From simultaneous modelling of planetary signals and activity, we predict the population of planets detected in the SLS-PS. With our fiducial survey strategy and expected instrument performance over a nominal survey length of ∼ 3 years, we expect SPIRou to detect 85.3 −3.2 Earth-like planets from a sample of 100 M1-M8.5 dwarfs out to 11 pc. By studying mid-to-late M dwarfs previously inaccessible to existing optical velocimeters, SPIRou will put meaningful constraints on the occurrence rate of planets around those stars including the value of η ⊕ at an expected level of precision of 45%. We also predict a subset of 46.7 +16.0 −6.0 planets may be accessible with dedicated high-contrast imagers on the next generation of ELTs including 4.9 +4.7 −2.0 potentially imagable Earth-like planets. Lastly, we compare the results of our fiducial survey strategy to other foreseeable survey versions to quantify which strategy is optimized to reach the SLS-PS science goals. The results of our simulations are made available to the community on github.

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Modelling the RV jitter of early-M dwarfs using tomographic imaging

Cited by 85 publications

References 49 publications

The Effect of Combined Magnetic Geometries on Thermally Driven Winds. I. Interaction of Dipolar and Quadrupolar Fields

The Effect of Combined Magnetic Geometries on Thermally Driven Winds. I. Interaction of Dipolar and Quadrupolar Fields

Stellar magnetic activity and exoplanets

Predictions of Planet Detections with Near-infrared Radial Velocities in the Upcoming SPIRou Legacy Survey-planet Search

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