The Gaia -ESO Survey: Stellar radii in the young open clusters NGC 2264, NGC 2547, and NGC 2516

R. J. Jackson, R. D. Jeffries, S. Randich, A. Bragaglia, G. Carraro, M. T. Costado, E. Flaccomio, A. C. Lanzafame, C. Lardo, L. Monaco, L. Morbidelli, R. Smiljanic, S. Zaggia

Resultado de la investigación: Article

13 Citas (Scopus)

Resumen

Context. Rapidly rotating, low-mass members of eclipsing binary systems have measured radii that are significantly larger than predicted by standard evolutionary models. It has been proposed that magnetic activity is responsible for this radius inflation. Aims. By estimating the radii of low-mass stars in three young clusters (NGC 2264, NGC 2547, NGC 2516, with ages of ∼5, ∼35 and ∼140 Myr respectively), we aim to establish whether similar radius inflation is seen in single, magnetically active stars. Methods. We use radial velocities from the Gaia-ESO Survey (GES) and published photometry to establish cluster membership and then combine GES measurements of projected equatorial velocities with published rotation periods to estimate the average radii for groups of fast-rotating cluster members as a function of their luminosity and age. The average radii are compared with the predictions of both standard evolutionary models and variants that include magnetic inhibition of convection and starspots. Results. At a given luminosity, the stellar radii in NGC 2516 and NGC 2547 are larger than predicted by standard evolutionary models at the ages of these clusters. The discrepancy is least pronounced and not significant (10 per cent) in zero age main sequence stars with radiative cores, but more significant in lower-mass, fully convective pre main-sequence cluster members, reaching 30 ± 10 per cent. The uncertain age and distance of NGC 2264 preclude a reliable determination of any discrepancy for its members. Conclusions. The median radii we have estimated for low-mass fully convective stars in the older clusters are inconsistent (at the 2-3σ level) with non-magnetic evolutionary models and more consistent with models that incorporate the effects of magnetic fields or dark starspots. The available models suggest this requires either surface magnetic fields exceeding 2.5 kG, spots that block about 30 per cent of the photospheric flux, or a more moderate combination of both.

Idioma originalEnglish
Número de artículoA52
PublicaciónAstronomy and Astrophysics
Volumen586
DOI
EstadoPublished - 1 feb 2016

Huella dactilar

open clusters
European Southern Observatory
radii
starspots
inflation
stars
magnetic field
luminosity
young
main sequence stars
convection
magnetic fields
radial velocity
photometry
estimating
prediction
estimates
predictions

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Citar esto

Jackson, R. J., Jeffries, R. D., Randich, S., Bragaglia, A., Carraro, G., Costado, M. T., ... Zaggia, S. (2016). The Gaia -ESO Survey: Stellar radii in the young open clusters NGC 2264, NGC 2547, and NGC 2516. Astronomy and Astrophysics, 586, [A52]. https://doi.org/10.1051/0004-6361/201527507
Jackson, R. J. ; Jeffries, R. D. ; Randich, S. ; Bragaglia, A. ; Carraro, G. ; Costado, M. T. ; Flaccomio, E. ; Lanzafame, A. C. ; Lardo, C. ; Monaco, L. ; Morbidelli, L. ; Smiljanic, R. ; Zaggia, S. / The Gaia -ESO Survey : Stellar radii in the young open clusters NGC 2264, NGC 2547, and NGC 2516. En: Astronomy and Astrophysics. 2016 ; Vol. 586.
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title = "The Gaia -ESO Survey: Stellar radii in the young open clusters NGC 2264, NGC 2547, and NGC 2516",
abstract = "Context. Rapidly rotating, low-mass members of eclipsing binary systems have measured radii that are significantly larger than predicted by standard evolutionary models. It has been proposed that magnetic activity is responsible for this radius inflation. Aims. By estimating the radii of low-mass stars in three young clusters (NGC 2264, NGC 2547, NGC 2516, with ages of ∼5, ∼35 and ∼140 Myr respectively), we aim to establish whether similar radius inflation is seen in single, magnetically active stars. Methods. We use radial velocities from the Gaia-ESO Survey (GES) and published photometry to establish cluster membership and then combine GES measurements of projected equatorial velocities with published rotation periods to estimate the average radii for groups of fast-rotating cluster members as a function of their luminosity and age. The average radii are compared with the predictions of both standard evolutionary models and variants that include magnetic inhibition of convection and starspots. Results. At a given luminosity, the stellar radii in NGC 2516 and NGC 2547 are larger than predicted by standard evolutionary models at the ages of these clusters. The discrepancy is least pronounced and not significant (10 per cent) in zero age main sequence stars with radiative cores, but more significant in lower-mass, fully convective pre main-sequence cluster members, reaching 30 ± 10 per cent. The uncertain age and distance of NGC 2264 preclude a reliable determination of any discrepancy for its members. Conclusions. The median radii we have estimated for low-mass fully convective stars in the older clusters are inconsistent (at the 2-3σ level) with non-magnetic evolutionary models and more consistent with models that incorporate the effects of magnetic fields or dark starspots. The available models suggest this requires either surface magnetic fields exceeding 2.5 kG, spots that block about 30 per cent of the photospheric flux, or a more moderate combination of both.",
keywords = "Open clusters and associations: individual: NGC 2264, Open clusters and associations: individual: NGC 2516, Open clusters and associations: individual: NGC 2547, Stars: activity, Stars: low-mass, Stars: rotation",
author = "Jackson, {R. J.} and Jeffries, {R. D.} and S. Randich and A. Bragaglia and G. Carraro and Costado, {M. T.} and E. Flaccomio and Lanzafame, {A. C.} and C. Lardo and L. Monaco and L. Morbidelli and R. Smiljanic and S. Zaggia",
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Jackson, RJ, Jeffries, RD, Randich, S, Bragaglia, A, Carraro, G, Costado, MT, Flaccomio, E, Lanzafame, AC, Lardo, C, Monaco, L, Morbidelli, L, Smiljanic, R & Zaggia, S 2016, 'The Gaia -ESO Survey: Stellar radii in the young open clusters NGC 2264, NGC 2547, and NGC 2516', Astronomy and Astrophysics, vol. 586, A52. https://doi.org/10.1051/0004-6361/201527507

The Gaia -ESO Survey : Stellar radii in the young open clusters NGC 2264, NGC 2547, and NGC 2516. / Jackson, R. J.; Jeffries, R. D.; Randich, S.; Bragaglia, A.; Carraro, G.; Costado, M. T.; Flaccomio, E.; Lanzafame, A. C.; Lardo, C.; Monaco, L.; Morbidelli, L.; Smiljanic, R.; Zaggia, S.

En: Astronomy and Astrophysics, Vol. 586, A52, 01.02.2016.

Resultado de la investigación: Article

TY - JOUR

T1 - The Gaia -ESO Survey

T2 - Stellar radii in the young open clusters NGC 2264, NGC 2547, and NGC 2516

AU - Jackson, R. J.

AU - Jeffries, R. D.

AU - Randich, S.

AU - Bragaglia, A.

AU - Carraro, G.

AU - Costado, M. T.

AU - Flaccomio, E.

AU - Lanzafame, A. C.

AU - Lardo, C.

AU - Monaco, L.

AU - Morbidelli, L.

AU - Smiljanic, R.

AU - Zaggia, S.

PY - 2016/2/1

Y1 - 2016/2/1

N2 - Context. Rapidly rotating, low-mass members of eclipsing binary systems have measured radii that are significantly larger than predicted by standard evolutionary models. It has been proposed that magnetic activity is responsible for this radius inflation. Aims. By estimating the radii of low-mass stars in three young clusters (NGC 2264, NGC 2547, NGC 2516, with ages of ∼5, ∼35 and ∼140 Myr respectively), we aim to establish whether similar radius inflation is seen in single, magnetically active stars. Methods. We use radial velocities from the Gaia-ESO Survey (GES) and published photometry to establish cluster membership and then combine GES measurements of projected equatorial velocities with published rotation periods to estimate the average radii for groups of fast-rotating cluster members as a function of their luminosity and age. The average radii are compared with the predictions of both standard evolutionary models and variants that include magnetic inhibition of convection and starspots. Results. At a given luminosity, the stellar radii in NGC 2516 and NGC 2547 are larger than predicted by standard evolutionary models at the ages of these clusters. The discrepancy is least pronounced and not significant (10 per cent) in zero age main sequence stars with radiative cores, but more significant in lower-mass, fully convective pre main-sequence cluster members, reaching 30 ± 10 per cent. The uncertain age and distance of NGC 2264 preclude a reliable determination of any discrepancy for its members. Conclusions. The median radii we have estimated for low-mass fully convective stars in the older clusters are inconsistent (at the 2-3σ level) with non-magnetic evolutionary models and more consistent with models that incorporate the effects of magnetic fields or dark starspots. The available models suggest this requires either surface magnetic fields exceeding 2.5 kG, spots that block about 30 per cent of the photospheric flux, or a more moderate combination of both.

AB - Context. Rapidly rotating, low-mass members of eclipsing binary systems have measured radii that are significantly larger than predicted by standard evolutionary models. It has been proposed that magnetic activity is responsible for this radius inflation. Aims. By estimating the radii of low-mass stars in three young clusters (NGC 2264, NGC 2547, NGC 2516, with ages of ∼5, ∼35 and ∼140 Myr respectively), we aim to establish whether similar radius inflation is seen in single, magnetically active stars. Methods. We use radial velocities from the Gaia-ESO Survey (GES) and published photometry to establish cluster membership and then combine GES measurements of projected equatorial velocities with published rotation periods to estimate the average radii for groups of fast-rotating cluster members as a function of their luminosity and age. The average radii are compared with the predictions of both standard evolutionary models and variants that include magnetic inhibition of convection and starspots. Results. At a given luminosity, the stellar radii in NGC 2516 and NGC 2547 are larger than predicted by standard evolutionary models at the ages of these clusters. The discrepancy is least pronounced and not significant (10 per cent) in zero age main sequence stars with radiative cores, but more significant in lower-mass, fully convective pre main-sequence cluster members, reaching 30 ± 10 per cent. The uncertain age and distance of NGC 2264 preclude a reliable determination of any discrepancy for its members. Conclusions. The median radii we have estimated for low-mass fully convective stars in the older clusters are inconsistent (at the 2-3σ level) with non-magnetic evolutionary models and more consistent with models that incorporate the effects of magnetic fields or dark starspots. The available models suggest this requires either surface magnetic fields exceeding 2.5 kG, spots that block about 30 per cent of the photospheric flux, or a more moderate combination of both.

KW - Open clusters and associations: individual: NGC 2264

KW - Open clusters and associations: individual: NGC 2516

KW - Open clusters and associations: individual: NGC 2547

KW - Stars: activity

KW - Stars: low-mass

KW - Stars: rotation

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U2 - 10.1051/0004-6361/201527507

DO - 10.1051/0004-6361/201527507

M3 - Article

AN - SCOPUS:84956985321

VL - 586

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

SN - 0004-6361

M1 - A52

ER -