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

Abstract

Average stellar radii in open clusters can be estimated from rotation periods and projected rotational velocities under the assumption of random orientation of the spin axis. Such estimates are independent of distance, interstellar absorption, and models, but their validity can be limited by missing data (truncation) or data that only represent upper/lower limits (censoring). We present a new statistical analysis method to estimate average stellar radii in the presence of censoring and truncation. We use theoretical distribution functions of the projected stellar radius $R\sin i$ to define a likelihood function in the presence of censoring and truncation. Average stellar radii in magnitude bins are then obtained by a maximum likelihood parametric estimation procedure. This method is capable of recovering the average stellar radius within a few percent with as few as $\approx$ 10 measurements. Here it is applied for the first time to the dataset available for the Pleiades. We find an agreement better than $\approx$ 10 percent between the observed $R$ vs $M_K$ relationship and current standard stellar models for 1.2 $\ge M/M_{\odot }\ge$ 0.85 with no evident bias. Evidence of a systematic deviation at $2\sigma$ level are found for stars with 0.8 $\ge M/M_{\odot }\ge$ 0.6 approaching the slow-rotator sequence. Fast-rotators ($P$ < 2 d) agree with standard models within 15 percent with no systematic deviations in the whole 1.2 $\ge M/M_{\odot }\ge$ 0.5 range. The evidence found of a possible radius inflation just below the lower mass limit of the slow-rotator sequence indicates a possible connection with the transition from the fast to the slow-rotator sequence.

arXiv commentAccepted by Astronomy and Astrophysics, 11 pages, 6 figures

References in corpus (26)

• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• Accurate masses and radii of normal stars: modern results and applications
• How to Constrain Your M Dwarf: measuring effective temperature, bolometric luminosity, mass, and radius
• On the rotational evolution of solar- and late-type stars, its magnetic origins, and the possibility of stellar gyrochronology
• Stellar Diameters and Temperatures II. Main Sequence K & M Stars
• Parallaxes and proper motions for 20 open clusters as based on the new Hipparcos catalogue
• Keck Spectra of Pleiades Brown Dwarf Candidates and a Precise Determination of the Lithium Depletion Edge in the Pleiades
• Evolution of low-mass star and brown dwarf eclipsing binaries
• The radius discrepancy in low mass stars: single vs. binaries
• Magnetic Inhibition of Convection and the Fundamental Properties of Low-Mass Stars. I. Stars with a Radiative Core
• Confirmation of Errors in Hipparcos Parallaxes from HST/FGS Astrometry of the Pleiades
• A VLBI Resolution of the Pleiades Distance Controversy
• Near and Mid-IR Photometry of the Pleiades, and a New List of Substellar Candidate Members
• Older and Colder: The impact of starspots on pre-main sequence stellar evolution
• Reevaluating the Mass-Radius Relation for Low-Mass, Main Sequence Stars
• Magnetic Inhibition of Convection and the Fundamental Properties of Low-Mass Stars. II. Fully Convective Main Sequence Stars
• Rotational velocities of low-mass stars in the Pleiades and Hyades
• Rotation, inflation, and lithium in the Pleiades
• Differential rotation in rapidly rotating F-stars
• A Tale of Two Anomalies: Depletion, Dispersion, and the Connection Between the Stellar Lithium Spread and Inflated Radii on the Pre-Main Sequence
• Rotational evolution of slow-rotators sequence stars
• Are the spin axes of stars randomly aligned within a cluster?
• The effect of starspots on the radii of low-mass pre-main sequence stars
• The radii of M-dwarfs in the young open cluster NGC 2516
• The effects of inclination, gravity darkening and differential rotation on absorption profiles of fast rotators
• Lower limit for differential rotation in members of young loose stellar associations

Cited by in corpus (11)

• The Yale-Potsdam Stellar Isochrones (YaPSI)
• The lithium-rotation connection in the 125 Myr-old Pleiades cluster
• A Measurement of Radius Inflation in the Pleiades and its Relation to Rotation and Lithium Depletion
• The inflated radii of M-dwarfs in the Pleiades
• Stellar Rotation of T Tauri stars in the Orion Star-Forming Complex
• A search for radius inflation among active M-dwarfs in Praesepe
• Stellar Spins in the Pleiades, Praesepe, and M35 Open Clusters
• Stellar Characterization and Radius Inflation of Hyades M Dwarf Stars From the APOGEE Survey
• Improved calibration of the radii of cool stars based on 3D simulations of convection: implications for the solar model
• Suppression of lithium depletion in young low-mass stars from fast rotation
• Rotational Velocities and Radii Estimates of Low-Mass Pre-Main Sequence Stars in NGC 2264