Rotational velocities of low mass stars in intermediate age open clusters

2008 ◽  
pp. 94-104
Author(s):  
J. R. Stauffer
Keyword(s):  
Open Clusters ◽  
Low Mass Stars ◽  
Low Mass

scholarly journals Ages of Galactic and Extragalactic Star Clusters of Various Abundances

1983 ◽  
Vol 6 ◽  
pp. 109-117 ◽  
Author(s):  
R.D. Cannon
Keyword(s):  
Star Clusters ◽  
Magellanic Clouds ◽  
Open Clusters ◽  
Simultaneous Solution ◽  
Low Mass Stars ◽  
Cluster Systems ◽  
Distant Cluster ◽  
Low Mass

In this review I shall concentrate mainly on globular star clusters in our Galaxy since these are the objects for which most work has been done recently, both observationally and theoretically. However, I shall also discuss briefly the oldest open clusters and clusters in the Magellanic Clouds. Little can be said about more distant cluster systems, since the only observations available are of integrated colours or spectra and these seem to be rather unreliable indicators of age. It is perhaps worth pointing out that the title may be slightly misleading; the problem is not so much to determine the ages of clusters of known abundances, as to obtain the best simultaneous solution for both age and composition, since some of the most important abundances (notably helium and oxygen) are virtually unobservable in little-evolved low mass stars.

scholarly journals Observations of low mass stars in clusters: Some constraints and puzzles for stellar evolution theory

1984 ◽  
Vol 105 ◽  
pp. 123-138
Author(s):  
R.D. Cannon
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Star Clusters ◽  
Variable Stars ◽  
Open Clusters ◽  
Low Mass Stars ◽  
Theory Of Evolution ◽  
Theoretical Predictions ◽  
Low Mass ◽  
Red Giant

This review will attempt to do two things: (i) discuss some of the data which are available for testing the theory of evolution of low mass stars, and (ii) point out some problem areas where observations and theory do not seem to agree very well. This is of course too vast a field of research to be covered in one brief review, so I shall concentrate on one particular aspect, namely the study of star clusters and especially their colour-magnitude (CM) diagrams. Star clusters provide large samples of stars at the same distance and with the same age, and the CM diagram gives the easiest way of comparing theoretical predictions with observations, although crucial evidence is also provided by spectroscopic abundance analyses and studies of variable stars. Since this is primarily a review of observational data it is natural to divide it into two parts: (i) galactic globular clusters, and (ii) old and intermediate-age open clusters. Some additional evidence comes from Local Group galaxies, especially now that CM diagrams which reach the old main sequence are becoming available. For each class of cluster I shall consider successive stages of evolution from the main sequence, up the hydrogen-burning red giant branch, and through the helium-burning giant phase.

scholarly journals Measurements of the Ca ii infrared triplet emission lines of pre-main-sequence stars

2020 ◽  
Vol 72 (5) ◽  
Author(s):  
Mai Yamashita ◽  
Yoichi Itoh ◽  
Yuhei Takagi
Keyword(s):  
Main Sequence ◽  
Open Clusters ◽  
Emission Lines ◽  
Main Sequence Stars ◽  
Low Mass Stars ◽  
Chromospheric Activity ◽  
Low Mass ◽  
Pms Stars ◽  
Infrared Triplet ◽  
Narrow Emission

Abstract We investigated the chromospheric activity of 60 pre-main-sequence (PMS) stars in four molecular clouds and five moving groups. It is considered that strong chromospheric activity is driven by the dynamo processes generated by stellar rotation. In contrast, several researchers have pointed out that the chromospheres of PMS stars are activated by mass accretion from their protoplanetary disks. In this study, the Ca ii infrared triplet (IRT) emission lines were investigated utilizing medium- and high-resolution spectroscopy. The observations were conducted with Nayuta/MALLS and Subaru/HDS. Additionally, archive data obtained by Keck/HIRES, VLT/UVES, and VLT/X-Shooter were used. The small ratios of the equivalent widths indicate that Ca ii IRT emission lines arise primarily in dense chromospheric regions. Seven PMS stars show broad emission lines. Among them, four PMS stars have more than one order of magnitude brighter emission line fluxes compared to the low-mass stars in young open clusters. The four PMS stars have a high mass accretion rate, which indicates that the broad and strong emission results from a large mass accretion. However, most PMS stars exhibit narrow emission lines. No significant correlation was found between the accretion rate and flux of the emission line. The ratios of the surface flux of the Ca ii IRT lines to the stellar bolometric luminosity, $R^{\prime }_{\rm IRT}$, of the PMS stars with narrow emission lines are as large as the largest $R^{\prime }_{\rm IRT}$ of the low-mass stars in the young open clusters. This result indicates that most PMS stars, even in the classical T Tauri star stage, have chromospheric activity similar to zero-age main-sequence stars.

scholarly journals ENHANCED PRODUCTION OF BARIUM IN LOW-MASS STARS: EVIDENCE FROM OPEN CLUSTERS

2009 ◽  
Vol 693 (1) ◽  
pp. L31-L34 ◽  
Author(s):  
Valentina D'Orazi ◽  
Laura Magrini ◽  
Sofia Randich ◽  
Daniele Galli ◽  
Maurizio Busso ◽  
...  
Keyword(s):  
Open Clusters ◽  
Low Mass Stars ◽  
Enhanced Production ◽  
Low Mass

scholarly journals A Study of Convection with δ Scuti Stars in Open Clusters: the Pleiades

2002 ◽  
Vol 185 ◽  
pp. 490-493
Author(s):  
J.-C. Suárez ◽  
E. Michel ◽  
G. Houdek ◽  
Y. Lebreton ◽  
F. Pérez Hernández
Keyword(s):  
Linear Instability ◽  
Open Clusters ◽  
High Mass ◽  
Mixing Length ◽  
Low Mass Stars ◽  
Fast Rotation ◽  
Strong Disagreement ◽  
Low Mass ◽  
Scuti Stars ◽  
Δ Scuti Stars

AbstractIn this work we propose a preliminary seismic investigation of δ Scuti stars in the Pleiades cluster, focusing on potential diagnostics of convection and core-overshooting. Taking into account the effect of fast rotation in the modelling, we compare observed frequencies for 4 δ Scuti stars with radial linear instability predictions. A satisfying agreement is reached between the predicted ranges of unstable modes and those derived from observations for “low-mass” stars (∼ 1.55M⊙). However, a strong disagreement is found for “high-mass” stars (∼ 1.77M⊙), whatever the mixing length (α) value. These results are compared with previous ones obtained for Praesepe.

scholarly journals A Review on Substellar Objects below the Deuterium Burning Mass Limit: Planets, Brown Dwarfs or What?

Geosciences ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 362 ◽  
Author(s):  
José Caballero
Keyword(s):  
Brown Dwarfs ◽  
Open Clusters ◽  
Formation Mechanisms ◽  
Mass Limit ◽  
Low Mass Stars ◽  
Open Clusters And Associations ◽  
Substellar Objects ◽  
History Of ◽  
Low Mass ◽  
Moving Groups

“Free-floating, non-deuterium-burning, substellar objects” are isolated bodies of a few Jupiter masses found in very young open clusters and associations, nearby young moving groups, and in the immediate vicinity of the Sun. They are neither brown dwarfs nor planets. In this paper, their nomenclature, history of discovery, sites of detection, formation mechanisms, and future directions of research are reviewed. Most free-floating, non-deuterium-burning, substellar objects share the same formation mechanism as low-mass stars and brown dwarfs, but there are still a few caveats, such as the value of the opacity mass limit, the minimum mass at which an isolated body can form via turbulent fragmentation from a cloud. The least massive free-floating substellar objects found to date have masses of about 0.004 Msol, but current and future surveys should aim at breaking this record. For that, we may need LSST, Euclid and WFIRST.

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