7 papers · 1 filter
The distance to the Orion Nebula Cluster
R. D. Jeffries
The distance to the Orion Nebula Cluster (ONC) is estimated using the rotational properties of its low-mass pre main-sequence (PMS) stars. Rotation periods, projected equatorial ve…
Synthesis of the Beryllium 3131A Spectral Region
Johanna F. Ashwell, R. D. Jeffries, B. Smalley
The Beryllium spectral region of the Sun, Procyon and 4 stars in the open cluster NGC6633 up to Teff = 7500K have been synthesised using ATLAS9 model atmospheres and the MOOG spect…
Low Mass Stars and Brown Dwarfs around Sigma Orionis
M. J. Kenyon, R. D. Jeffries, T. Naylor
We present optical spectroscopy of 71 photometric candidate low-mass members of the cluster associated with Sigma Orionis. Thirty-five of these are found to pass the lithium test a…
The Lithium Depletion Boundary as a Clock and Thermometer
R. D. Jeffries, T. Naylor
We take a critical look at the lithium depletion boundary (LDB) technique that has recently been used to derive the ages of open clusters. We identify the sources of experimental a…
Ages, Distances, and the Initial Mass Functions of Stellar Clusters
J. R. Stauffer, R. D. Jeffries, E. L. Martin +1
We provide a review of the current status of several topics on the ages, distances, and mass functions of open clusters, with a particular emphasis on illuminating the areas of unc…
Lithium depletion in open clusters
R. D. Jeffries
The current status of observational studies of lithium depletion in open clusters is reviewed, concentrating mainly on G and K type stars. I attempt to answer the following questio…