Skip to main content

Research Repository

Advanced Search

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

Jackson, Richard J.; Jeffries, Robin 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 Thumbnail


Authors

Richard J. Jackson

S. Randich

A. Bragaglia

G. Carraro

M.T. Costado

E. Flaccomio

A.C. Lanzafame

C. Lardo

L. Monaco

L. Morbidelli

R. Smiljanic

S. Zaggia



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 2–3s 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.

Journal Article Type Article
Acceptance Date Nov 17, 2015
Online Publication Date Jan 26, 2016
Publication Date 2016-02
Publicly Available Date Mar 28, 2024
Journal Astronomy and Astrophysics
Print ISSN 0365-0138
Publisher EDP Sciences
Peer Reviewed Peer Reviewed
Volume 586
Article Number A52
DOI https://doi.org/10.1051/0004-6361/201527507
Keywords stars: rotation, stars: low-mass, stars: activity, open clusters and associations: individual: NGC 2264, open clusters and associations: individual: NGC 2547, open clusters and associations: individual: NGC 2516
Publisher URL https://doi.org/10.1051/0004-6361/201527507

Files




You might also like



Downloadable Citations