Magnetic fields of intermediate mass T Tauri stars

Lavail, Alexis; Kochukhov, Oleg; Hussain, G. A. J.; Alécian, E.; Herczeg, Gregory J.; Johns–Krull, Christopher M.

doi:10.1051/0004-6361/201731889

Cited by 40 publications

(43 citation statements)

References 36 publications

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“…stars from Alecian et al (2013) -using similar symbols as the IMTTS but with faded colors; as well as other IMTTS and LMTTS -using blue symbols (Donati et al 2007(Donati et al , 2008(Donati et al , 2010b(Donati et al , 2011b(Donati et al ,c, 2013(Donati et al , 2015Hussain et al 2009;Kochukhov 2015;Hill et al 2017;Lavail et al 2017;Yu & Donati 2017). In the latter case, all stars are magnetic, and the light-blue (blue) color indicates a lack (or not) of information on the B values.…”

Section: The Origin Of Magnetic Fields In Herbig and Ap Starsmentioning

confidence: 98%

“…The three most massive stars in this study (Par 2244, Par 1379 and V410 Tau, at around 1.4-1.8 M ) overlap with the lightest and most convective stars of our sample and display similar magnetic topologies. Lavail et al (2017) measure the averaged modulus of the magnetic field over the visible stellar hemisphere ( B ) of six IMTTS from the Zeeman broadening of IR spectral lines. When compared to LMTTS in which similar measurements have been performed, Lavail et al (2017) proposed that we cannot find as strong magnetic fields in IMTTS as in some LMTTS.…”

Section: Low-mass T Tauri Stars and The Role Of Accretionmentioning

confidence: 99%

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Magnetic fields of intermediate-mass T Tauri stars

Villebrun

Alécian

Hussain

et al. 2019

A&A

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Context. The origin of the fossil magnetic fields detected in 5 to 10% of intermediate-mass main sequence stars is still highly debated. Aims. We want to bring observational constraints to a large population of intermediate-mass pre-main sequence (PMS) stars in order to test the theory that convective-dynamo fields generated during the PMS phases of stellar evolution can occasionally relax into fossil fields on the main sequence. Methods. Using distance estimations, photometric measurements, and spectropolarimetric data from HARPSpol and ESPaDOnS of 38 intermediate-mass PMS stars, we determined fundamental stellar parameters (Teff, L and v sin i) and measured surface magnetic field characteristics (including detection limits for non-detections, and longitudinal fields and basic topologies for positive detections). Using PMS evolutionary models, we determined the mass, radius, and internal structure of these stars. We compared different PMS models to check that our determinations were not model-dependant. We then compared the magnetic characteristics of our sample accounting for their stellar parameters and internal structures. Results. We detect magnetic fields in about half of our sample. About 90% of the magnetic stars have outer convective envelopes larger than ∼25% of the stellar radii, and heavier than ∼2% of the stellar mass. Going to higher mass, we find that the magnetic incidence in intermediate-mass stars drops very quickly, within a timescale on the order of few times 0.1 Myr. Finally, we propose that intermediate-mass T Tauri stars with large convective envelopes, close to the fully convective limit, have complex fields and that their dipole component strengths may decrease as the sizes of their convective envelopes decrease, similar to lower-mass T Tauri stars.

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Section: The Origin Of Magnetic Fields In Herbig and Ap Starsmentioning

confidence: 98%

Section: Low-mass T Tauri Stars and The Role Of Accretionmentioning

confidence: 99%

Magnetic fields of intermediate-mass T Tauri stars

Villebrun

Alécian

Hussain

et al. 2019

A&A

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“…Apart from being induced by a misaligned planet, inner disk warps can be due to a strong misaligned dipolar magnetic field as in the well-documented case of AA Tau. Lavail et al (2017) find a magnetic field of 1.4 kG in HD 143006 (called V1149 Sco in their paper), but the data are not sufficient to obtain a topology of the magnetic field. If the magnetic field is strongly inclined, and warps the inner disk edge, such a warp would rotate with the stellar period (approximately a few days), and lead to fast changing shadows.…”

Section: Origin Of the Warpmentioning

confidence: 99%

Shadows and asymmetries in the T Tauri disk HD 143006: evidence for a misaligned inner disk

Benisty

Juhász

Facchini

et al. 2018

A&A

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Context. While planet formation is thought to occur early in the history of a protoplanetary disk, the presence of planets embedded in disks, or of other processes driving disk evolution, might be traced from their imprints on the disk structure. Aims. We study the morphology of the disk around the T Tauri star HD 143006, located in the ∼5-11 Myr-old Upper Sco region, and we look for signatures of the mechanisms driving its evolution. Methods. We observed HD 143006 in polarized scattered light with VLT/SPHERE at near-infrared (J-band, 1.2 µm) wavelengths, reaching an angular resolution of ∼0.037 (∼6 au). We obtained two datasets, one with a 145 mas diameter coronagraph, and the other without, enabling us to probe the disk structure down to an angular separation of ∼0.06 (∼10 au). Results. In our observations, the disk of HD 143006 is clearly resolved up to ∼0.5 and shows a clear large-scale asymmetry with the eastern side brighter than the western side. We detect a number of additional features, including two gaps and a ring. The ring shows an overbrightness at a position angle (PA) of ∼140 • , extending over a range in position angle of ∼60 • , and two narrow dark regions. The two narrow dark lanes and the overall large-scale asymmetry are indicative of shadowing effects, likely due to a misaligned inner disk. We demonstrate the remarkable resemblance between the scattered light image of HD 143006 and a model prediction of a warped disk due to an inclined binary companion. The warped disk model, based on the hydrodynamic simulations combined with three-dimensional radiative transfer calculations, reproduces all major morphological features. However, it does not account for the observed overbrightness at PA∼140 • . Conclusions. Shadows have been detected in several protoplanetary disks, suggesting that misalignment in disks is not uncommon. However, the origin of the misalignment is not clear. As-yet-undetected stellar or massive planetary companions could be responsible for them, and naturally account for the presence of depleted inner cavities.

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“…All these factors limit practical applications of the Zeeman broadening diagnostic to active, very slowly rotating stars observed at R > ∼ 10 5 with high signal-to-noise ratio spectra (Robinson 1980;Marcy 1984;Saar et al 1986;Basri & Marcy 1988;Johns-Krull & Valenti 1996;Rüedi et al 1997;Anderson et al 2010). These restrictions can be partly relaxed with the help of observations at near-infrared wavelengths (Saar & Linsky 1985;Valenti et al 1995;Johns-Krull 2007;Yang & Johns-Krull 2011;Lavail et al 2017Lavail et al , 2019Flores et al 2019) thanks to a faster increase of Zeeman splitting with wavelength (grows as λ 2 ) compared to other broadening mechanisms (grow as λ). For instance, ∆v B ≈ 10 km s −1 for a 1 kG field and a g eff = 3 line at λ = 2.3 µm, enabling magnetic measurements of moderately fast rotators using lower quality data.…”

Section: Zeeman Broadening and Intensification Of Spectral Linesmentioning

confidence: 99%

Hidden magnetic fields of young suns

Kochukhov

Hackman

Lehtinen

et al. 2020

A&A

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Global magnetic fields of active solar-like stars are nowadays routinely detected with spectropolarimetric measurements and are mapped with Zeeman-Doppler imaging (ZDI). However, due to the cancellation of opposite field polarities, polarimetry captures only a tiny fraction of the magnetic flux and cannot assess the overall stellar surface magnetic field if it is dominated by a smallscale component. Analysis of Zeeman broadening in high-resolution intensity spectra can reveal these hidden complex magnetic fields. Historically, there were very few attempts to obtain such measurements for G dwarf stars due to the difficulty of disentangling Zeeman effect from other broadening mechanisms affecting spectral lines. Here we developed a new magnetic field diagnostic method based on relative Zeeman intensification of optical atomic lines with different magnetic sensitivity. Using this technique we obtained 78 field strength measurements for 15 Sun-like stars, including some of the best-studied young solar twins. We find that the average magnetic field strength B f drops from 1.3-2.0 kG in stars younger than about 120 Myr to 0.2-0.8 kG in older stars. The mean field strength shows a clear correlation with the Rossby number and with the coronal and chromospheric emission indicators. Our results suggest that magnetic regions have roughly the same local field strength B ≈ 3.2 kG in all stars, with the filling factor f of these regions systematically increasing with stellar activity. Comparing our results with the spectropolarimetric analyses of global magnetic fields in the same stars, we find that ZDI recovers about 1% of the total magnetic field energy in the most active stars. This figure drops to just 0.01% for the least active targets.

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Magnetic fields of intermediate mass T Tauri stars

Cited by 40 publications

References 36 publications

Magnetic fields of intermediate-mass T Tauri stars

Magnetic fields of intermediate-mass T Tauri stars

Shadows and asymmetries in the T Tauri disk HD 143006: evidence for a misaligned inner disk

Hidden magnetic fields of young suns

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