The Mean Magnetic Field Strength of CI Tau

Sokal, Kimberly R.; Johns–Krull, Christopher M.; Mace, Gregory N.; Nofi, Larissa; Prato, L.; Lee, Jae‐Joon; Jaffe, D. T.

doi:10.3847/1538-4357/ab59d8

Cited by 32 publications

(33 citation statements)

References 139 publications

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“…As shown in Figure 5, our measured magnetic field strengths positively correlate with literature optical temperatures. This finding, however, is in contradiction with results found in the previous study of Sokal et al (2020) who compiled magnetic field strengths of classical T Tauri stars (cTTS) and weak-line T Tauri stars from different authors (e.g., Johns-Krull 2007; Yang & Johns-Krull 2011; Lavail et al 2017), and plotted them against their optical temperatures. With a sample of 28 cTTS, 12 wTTS, and one Class I source, they found an anti-correlation between the measured magnetic field strengths and the optically measured temperatures, which was attributed to a possible evolutionary change in the stars.…”

Section: Starspots On Young Starscontrasting

confidence: 99%

The Effects of Starspots on Spectroscopic Mass Estimates of Low-mass Young Stars

Flores,

Connelley,

Reipurth

et al. 2021

Preprint

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Magnetic fields and mass accretion processes create dark and bright spots on the surface of young stars. These spots manifest as surface thermal inhomogeneities, which alter the global temperature measured on the stars. To understand the effects and implications of these starspots, we conducted a large iSHELL high-resolution infrared spectroscopic survey of T Tauri stars in Taurus-Auriga and Ophiuchus star-forming regions. From the K band spectra, we measured stellar temperatures and magnetic field strengths using a magnetic radiative transfer code. We compared our infrared-derived parameters against literature optical temperatures and found a) a systematic temperature difference between optical and infrared observations, and b) a positive correlation between the magnetic field strengths and the temperature differences. The discrepant temperature measurements imply significant differences in the inferred stellar masses from stellar evolutionary models. To discern which temperature better predicts the mass of the star, we compared our model-derived masses against dynamical masses measured from ALMA and PdBI for a sub-sample of our sources. From this comparison we conclude that, in the range of stellar masses from 0.3 to 1.3 M , neither infrared nor optical temperatures perfectly reproduce the stellar dynamical masses. But, on average, infrared temperatures produce more precise and accurate stellar masses than optical ones.

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Section: Starspots On Young Starscontrasting

confidence: 99%

The Effects of Starspots on Spectroscopic Mass Estimates of Low-mass Young Stars

Flores,

Connelley,

Reipurth

et al. 2021

Preprint

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“…Coronal TTS X-ray emission indicates the presence of a strong surface magnetic field (Stassun et al 2006(Stassun et al , 2007. The typical mean-field strengths measured at the surface of classical (fully convective) TTS are 1-3 kG, and decrease to a few 100 G for weak-line (mainly radiative) TTS (Hill et al 2019;Villebrun et al 2019;Donati et al 2019;Sokal et al 2020). The dynamos producing these magnetic fields are driven by convective interior structure, typical of low-mass TTS evolving along Hayashi tracks.…”

Section: Introductionmentioning

confidence: 99%

Characterizing the X-Ray Emission of Intermediate-mass Pre-main-sequence Stars

Nuñez

Povich

Binder

et al. 2021

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We use X-ray and infrared observations to study the properties of three classes of young stars in the Carina Nebula: intermediate-mass (2-5 M e ) pre-main-sequence stars (IMPS; i.e., intermediate-mass T Tauri stars), late-B and A stars on the zero-age main sequence (AB), and lower-mass T Tauri stars (TTS). We divide our sources among these three subclassifications and further identify disk-bearing young stellar objects versus diskless sources with no detectable infrared (IR) excess emission using IR (1-8 μm) spectral energy distribution modeling. We then perform X-ray spectral fitting to determine the hydrogen-absorbing column density (N H ), absorption-corrected X-ray luminosity (L X ), and coronal plasma temperature (kT) for each source. We find that the X-ray spectra of both IMPS and TTS are characterized by similar kT and N H , and on average L X /L bol ∼4×10 −4 . IMPS are systematically more luminous in X-rays (by ∼0.3 dex) than all other subclassifications, with median L X =2.5×10 31 erg s −1 , while AB stars of similar masses have X-ray emission consistent with TTS companions. These lines of evidence converge on a magnetocoronal flaring source for IMPS X-ray emission, a scaled-up version of the TTS emission mechanism. IMPS therefore provide powerful probes of isochronal ages for the first ∼10 Myr in the evolution of a massive stellar population, because their intrinsic, coronal X-ray emission decays rapidly after they commence evolving along radiative tracks. We suggest that the most luminous (in both X-rays and IR) IMPS could be used to place empirical constraints on the location of the intermediate-mass stellar birth line.

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“…Observations show strong, kG-strength surface magnetic fields on lowmass stars that weaken as they age (e.g. Yang et al 2005;Donati & Landstreet 2009;Lavail et al 2017;Donati et al 2020;Sokal et al 2020). Since young, low-mass stars are fully convective, it is generally assumed that any birth magnetic fields are quickly diffused and replaced by dynamo-generated fields (Chabrier & Küker 2006).…”

Section: Introductionmentioning

confidence: 99%

On the origin of magnetic fields in stars – II. The effect of numerical resolution

Wurster

Bate

Price

et al. 2022

Monthly Notices of the Royal Astronomical Society

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Are the kG-strength magnetic fields observed in young stars a fossil field left over from their formation or are they generated by a dynamo? Our previous numerical study concluded that magnetic fields must originate by a dynamo process. Here, we continue that investigation by performing even higher numerical resolution calculations of the gravitational collapse of a 1 M⊙ rotating, magnetised molecular cloud core through the first and second collapse phases until stellar densities are reached. Each model includes Ohmic resistivity, ambipolar diffusion, and the Hall effect. We test six numerical resolutions, using between 105 and 3 × 107 particles to model the cloud. At all but the lowest resolutions, magnetic walls form in the outer parts of the first hydrostatic core, with the maximum magnetic field strength located within the wall rather than at the centre of the core. At high resolution, this magnetic wall is disrupted by the Hall effect, producing a magnetic field with a spiral-shaped distribution of intensity. As the second collapse occurs, this field is dragged inward and grows in strength, with the maximum field strength increasing with resolution. As the second core forms, the maximum field strength exceeds 1 kG in our highest resolution simulations, and the stellar core field strength exceeds this threshold at the highest resolution. Our resolution study suggests that kG-strength magnetic fields may be implanted in low-mass stars during their formation, and may persist over long timescales given that the diffusion timescale for the magnetic field exceeds the age of the Universe.

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The Mean Magnetic Field Strength of CI Tau

Cited by 32 publications

References 139 publications

The Effects of Starspots on Spectroscopic Mass Estimates of Low-mass Young Stars

The Effects of Starspots on Spectroscopic Mass Estimates of Low-mass Young Stars

Characterizing the X-Ray Emission of Intermediate-mass Pre-main-sequence Stars

On the origin of magnetic fields in stars – II. The effect of numerical resolution

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