Evidence of radius inflation in stars approaching the slow-rotator sequence

Lanzafame, A. C.; Spada, F.; Distefano, E.

doi:10.1051/0004-6361/201628833

Cited by 12 publications

(11 citation statements)

References 43 publications

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“…Although a correlation between rotation and radius inflation has been reported for both the Pleiades (Somers & Stassun 2017) and M35 (Jeffries et al 2021), there is a lot of scatter and it is much weaker than that between rotation and the lithium abundance, and uncertainties on empirical radii are generally relatively large (e.g. Rebull et al 2004;Lanzafame et al 2017;Jackson et al 2019). Jeffries et al (2021) also found a correlation between radius inflation and Li below about 4800 K, providing support for the idea that these structural changes are an important mechanism.…”

Section: Introductionmentioning

confidence: 89%

Suppression of lithium depletion in young low-mass stars from fast rotation

Constantino,

Baraffe,

Goffrey

et al. 2021

Preprint

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We compute rotating 1D stellar evolution models that include a modified temperature gradient in convection zones and criterion for convective instability inspired by rotating 3D hydrodynamical simulations performed with the music code. In those 3D simulations we found that convective properties strongly depend on the Solberg-Høiland criterion for stability. We therefore incorporated this into 1D stellar evolution models by replacing the usual Schwarzschild criterion for stability and also modifying the temperature gradient in convection zones. We computed a grid of 1D models between 0.55 and 1.2 stellar masses from the pre-main sequence to the end of main sequence in order to study the problem of lithium depletion in low-mass main sequence stars. This is an ideal test case because many of those stars are born as fast rotators and the rate of lithium depletion is very sensitive to the changes in the stellar structure. Additionally, observations show a correlation between slow rotation and lithium depletion, contrary to expectations from standard models of rotationally driven mixing. By suppressing convection, and therefore decreasing the temperature at the base of the convective envelope, lithium burning is strongly quenched in our rapidly rotating models to an extent sufficient to account for the lithium spread observed in young open clusters.

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Section: Introductionmentioning

confidence: 89%

Suppression of lithium depletion in young low-mass stars from fast rotation

Constantino,

Baraffe,

Goffrey

et al. 2021

Preprint

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“…A maximum likelihood method is used to determine the average radius ratio or over-radius, ρ = R/Rm of the measured data relative to BHAC15 model radii, as a function of luminosity. The approach is similar to that used by Lanzafame et al (2017) 2). Diamonds with error bars show r sin i for targets with a relative uncertainty 30 per cent.…”

Section: Maximum Likelihood Methodsmentioning

confidence: 99%

“…2012), and with respect to a 5 Gyr solar-metallicity isochrone from BHAC15. The green point shows a previously reported measurement of ρ for Pleiades stars of 0.6 < M/M ⊙ < 0.8 and periods in the transition between the C and I gyrochronological sequences defined by Barnes (2007) (P > 2d, see Table 2 of Lanzafame et al 2017).…”

Section: ρmentioning

confidence: 96%

“…Jackson & Jeffries (2014a) used the same dataset and a similar modelling technique to compare the radii of Pleiades stars with 0.55 M/M⊙ < 1.0 with the interferometric radii of inactive main sequence field stars, finding an over-radius of 13 ± 3 per cent. Lanzafame et al (2017) performed their own analysis showing that the effect appears to be driven by a ∼ 30 per cent inflation for a subset of stars with 0.6 < M/M⊙ < 0.8 that are intermediate in rotation rate, but that faster rotators or more massive stars have radii consistent with model predictions.…”

Section: Introductionmentioning

confidence: 99%

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The inflated radii of M dwarfs in the Pleiades

Jackson

Deliyannis

Jeffries

2018

Monthly Notices of the Royal Astronomical Society

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Rotation periods obtained with the Kepler satellite have been combined with precise measurements of projected rotation velocity from the WIYN 3.5-m telescope to determine the distribution of projected radii for several hundred low-mass (0.1 M/M ⊙ 0.8), fastrotating members of the Pleiades cluster. A maximum likelihood modelling technique, that takes account of observational uncertainties, selection effects and censored data, and considers the effects of differential rotation and unresolved binarity, has been used to find that the average radius of these stars is 14 ± 2 per cent larger at a given luminosity than predicted by the evolutionary models of Dotter et al. (2008) and Baraffe et al. (2015). The same models are a reasonable match to the interferometric radii of older, magnetically inactive field M-dwarfs, suggesting that the over-radius may be associated with the young, magnetically active nature of the Pleiades objects. No evidence is found for any change in this over-radius above and below the boundary marking the transition to full convection. Published evolutionary models that incorporate either the effects of magnetic inhibition of convection or the blocking of flux by dark starspots do not individually explain the radius inflation, but a combination of the two effects might. The distribution of projected radii is consistent with the adopted hypothesis of a random spatial orientation of spin axes; strong alignments of the spin vectors into cones with an opening semi-angle < 30 • can be ruled out. Any plausible but weaker alignment would increase the inferred over-radius.

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“…Jackson & Jeffries 2010) and observational biases are understood, then a set of R sin i estimates can be modelled to determine the true average radius for a group of stars. This technique has been used to claim the detection of inflated radii in the young K-and M-type stars of several young clusters, notably the Pleiades at an age of ≃ 120 Myr (Jackson, Jeffries & Maxted 2009;Hartman et al 2010;Jackson & Jeffries 2014a;Jackson et al 2016;Lanzafame et al 2017). In Jackson et al (2018, hereafter Paper I), we obtained the largest ever set of homogeneously determined values of v sin i and P for low-mass stars in the Pleiades to investigate radius inflation as a function of mass using Eqn.…”

Section: Introductionmentioning

confidence: 99%

A search for radius inflation among active M-dwarfs in Praesepe

Jackson

Jeffries

Deliyannis

et al. 2018

Monthly Notices of the Royal Astronomical Society

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Rotation periods from Kepler K2 are combined with projected rotation velocities from the WIYN 3.5-m telescope, to determine projected radii for fast-rotating, low-mass (0.15 M/M ⊙ 0.6) members of the Praesepe cluster. A maximum likelihood analysis that accounts for observational uncertainties, binarity and censored data, yields marginal evidence for radius inflation -the average radius of these stars is 6 ± 4 per cent larger at a given luminosity than predicted by commonly-used evolutionary models. This over-radius is smaller (at 2-sigma confidence) than was found for similar stars in the younger Pleiades using a similar analysis; any decline appears due to changes occurring in higher mass (> 0.25M ⊙ ) stars. Models incorporating magnetic inhibition of convection predict an over-radius, but do not reproduce this mass dependence unless super-equipartition surface magnetic fields are present at lower masses. Models incorporating flux-blocking by starspots can explain the mass dependence but there is no evidence that spot coverage diminishes between the Pleiades and Praesepe samples to accompany the decline in over-radius. The fastest rotating stars in both Praesepe and the Pleiades are significantly smaller than the slowest rotators for which a projected radius can be measured. This may be a selection effect caused by more efficient angular momentum loss in larger stars leading to their progressive exclusion from the analysed samples. Our analyses assume random spin-axis orientations; any alignment in Praesepe, as suggested by Kovacs (2018), is strongly disfavoured by the broad distribution of projected radii.

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Evidence of radius inflation in stars approaching the slow-rotator sequence

Cited by 12 publications

References 43 publications

Suppression of lithium depletion in young low-mass stars from fast rotation

Suppression of lithium depletion in young low-mass stars from fast rotation

The inflated radii of M dwarfs in the Pleiades

A search for radius inflation among active M-dwarfs in Praesepe

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