The Lower Main Sequence of Stars in the Solar Neighborhood: Model Predictions Versus Observation

Bartasiute, S.; Deveikis, V.; Raudeliunas, S.; Sperauskas, J.

doi:10.1515/astro-2017-0398

Cited by 3 publications

(5 citation statements)

References 16 publications

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“…With the exception of a significant number of the fainter components (42), all of the MCC stars have photoelectric BVRI data, obtained mainly by Upgren (1987), including recent homogeneous U BV(RI) C photometry by Koen et al (2010) . The thick line is the mean relation for the color interval 0.9 < V − I C < 2.8, defined by Bartašiūtė et al (2012) using the present sample stars with σ π /π ≤ 0.05 (red and blue circles). The error bars represent uncertainties due to trigonometric parallax error.…”

Section: The Samplementioning

confidence: 99%

“…As is apparent, there is considerable scatter of points, an appreciable fraction of which is certainly caused by parallax error (black solid and black open points representing stars with σ π /π ≥ 0.05) and the presence of double and variable stars. The gray thick line represents the mean relation defined in the paper by Bartašiūtė et al (2012) using the present program stars with σ π /π ≤ 0.05, which belong kinematically to the thin disk population and which were carefully selected to be single and non-variable (i.e., showing no signs of radial-velocity variability and not contained in the "double and multiple star" or "variability" annex of the Hipparcos catalog or reported elsewhere as binaries and variables). These selected stars (a total of 347 with V I C photometry) are shown in the diagram by red (MCC) and blue (CNS) symbols.…”

Section: The Samplementioning

confidence: 99%

“…3, the relations (M V , B − V) and (M V , V − R C ) were also defined in the above-quoted paper by Bartašiūtė et al (2012). These three relations were used in the present paper to infer the absolute magnitudes and distances to 29 stars of the MCC sample, which had no any, or very poor, trigonometric parallax data (see Sect.…”

Section: The Samplementioning

confidence: 99%

“…For a few other stars the trigonometric parallax data were found in several other literature sources. However, 29 stars had no any or very poor trigonometric parallax measurements available in the literature, and we adopted, in this case, their photometric parallaxes inferred from the magnitude-color relations in the ( Bartašiūtė et al (2012). As a final value of photometric parallax, an average over the three magnitude-color relations was taken, with its error including the rms scatter around the relations (±0.25 mag in M V ) that contributes a major amount to the total uncertainty.…”

Section: Datamentioning

confidence: 99%

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Radial velocities of K–M dwarfs and local stellar kinematics

Sperauskas

Bartasiute

Boyle

et al. 2016

A&A

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Aims. The goal of this paper is to present complete radial-velocity data for the spectroscopically selected McCormick sample of nearby K-M dwarfs and, based on these and supplementary data, to determine the space-velocity distributions of late-type stars in the solar neighborhood. Methods. We analyzed nearly 3300 measurements of radial velocities for 1049 K-M dwarfs, that we obtained during the past decade with a CORAVEL-type instrument, with a primary emphasis on detecting and eliminating from kinematic calculations the spectroscopic binaries and binary candidates. Combining radial-velocity data with Hipparcos/Tycho-2 astrometry we calculated the space-velocity components and parameters of the galactic orbits in a three-component model potential for the stars in the sample, that we use for kinematical analysis and for the identification of possible candidate members of nearby stellar kinematic groups. Results. We present the catalog of our observations of radial velocities for 959 stars which are not suspected of velocity variability, along with the catalog of U, V, W velocities and Galactic orbital parameters for a total of 1088 K-M stars which are used in the present kinematic analysis. Of these, 146 stars were identified as possible candidate members of the known nearby kinematic groups and suspected subgroups. The distributions of space-velocity components, orbital eccentricities, and maximum distances from the Galactic plane are consistent with the presence of young, intermediate-age and old populations of the thin disk and a small fraction (∼3%) of stars with the thick disk kinematics. The kinematic structure gives evidence that the bulk of K-M type stars in the immediate solar vicinity represents a dynamically relaxed stellar population. The star MCC 869 is found to be on a retrograde Galactic orbit (V = −262 km s −1 ) of low inclination (4 • ) and can be a member of stellar stream of some dissolved structure. The Sun's velocity with respect to the Local Standard of Rest, derived from the distributions of space-velocity components, is (U , V , W ) = (9.0 ± 1.4, 13.1 ± 0.6, 7.2 ± 0.8) km s −1 . The radial solar motion derived via the Strömberg's relation, V = 14.2 ± 0.8 km s −1 , agrees within the errors with the value obtained directly from the V distribution of stars on nearly circular orbits.

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Section: The Samplementioning

confidence: 99%

Section: The Samplementioning

confidence: 99%

Section: The Samplementioning

confidence: 99%

Section: Datamentioning

confidence: 99%

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Radial velocities of K–M dwarfs and local stellar kinematics

Sperauskas

Bartasiute

Boyle

et al. 2016

A&A

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“…At this temperature, the NextGen and Bessell et alK magnitudes are similar. Although there is evidence that the Victoria-Regina model isochrones, which use the VandenBerg & Clem colors, match observational color-absolute magnitude diagrams of nearby K-M dwarfs with precise Hipparcos parallaxes better than other isochrones (e.g Bartašiūtė et al 2012),. we have opted not to use the VandenBerg & Clem results because of the lack of a K magnitude counterpart to their I magnitude.…”

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confidence: 99%

Magnetic Effects and Oversized M Dwarfs in the Young Open Cluster NGC 2516

MacDonald

Mullan

2013

ApJ

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By combining rotation periods with spectroscopic determinations of projected rotation velocity, Jackson, Jeffries & Maxted (2009) have found that the mean radii for low-mass M-dwarfs in the young, open cluster NGC 2516 are larger than model predictions at a given absolute I magnitude or I -K color and also larger than measured radii of magnetically inactive M-dwarfs. The relative radius difference is correlated with magnitude, increasing from a few per cent at M I = 7 to greater than 50 per cent for the lowest luminosity stars in their sample at M I ~ 9.5. Jackson et al (2009) have suggested that a two-temperature star spot model is capable of explaining the observations, but their model requires spot coverage fractions of at least 50 per cent in rapidly rotating M-dwarfs. Here we examine these results in terms of stellar models that include the inhibiting effects of magnetic fields on convective energy transport, with and without the effects of star spots. We find that a pure spot model is inconsistent with the color -magnitude diagram. The observations of radii versus color and radii versus absolute magnitude in NGC 2516 are consistent with models which include only magnetic inhibition or a combination of magnetic inhibition and spots. At a given mass we find a large dispersion in the strength of the vertical component of the magnetic field in the stellar photosphere but the general trend is that the vertical field increases with decreasing mass from a few hundred Gauss at 0.65 M⊙ to 600 -900 Gauss, depending on spot coverage, in the lowest mass stars in the sample at 0.25 M⊙.

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