scholarly journals Lithium abundances in the α Persei Cluster

2009 ◽  
Vol 5 (S268) ◽  
pp. 339-340
Author(s):  
Sushma V. Mallik ◽  
Suchitra C. Balachandran ◽  
David L. Lambert
Keyword(s):  
High Resolution ◽  
Cluster Membership ◽  
Young Clusters ◽  
Larger Sample

AbstractAs a sequel to the Li observations by Balachandran, Lambert & Stauffer (1988, 1996) in 35 stars of the 50 Myr old cluster α Persei, we have obtained and analyzed high resolution spectra of another 51 stars. Following a reconsideration of the cluster membership of the stars (Prosser 1992, Makarov 2006, Mermilliod et al. 2008, and Patience et al. 2002), we discuss the Li abundances for 70 stars. With our larger sample, we reexamine the question of whether the scatter in Li abundance at a given Teff seen in young clusters at cool temperatures is real or not.

scholarly journals The Redshift Distribution of Ly α Forest Lines in Spectra of QSOs

1994 ◽  
Vol 159 ◽  
pp. 509-510
Author(s):  
Huang Keliang ◽  
Zhou Hongnan
Keyword(s):  
High Resolution ◽  
Early Universe ◽  
Equivalent Width ◽  
Large Scale ◽  
Strong Line ◽  
Redshift Distribution ◽  
Medium Resolution ◽  
The Universe ◽  
Larger Sample ◽  
Line Sample

Numerous narrow absorption lines in the region of wavelength shorter than 1216(1+zem) (zem is the emission redshift), i.e. so-called Ly α forest lines, detected in QSO spectra are usually thought to be produced in intervening primeval clouds. The study of Ly α clouds may reveal how matter distributes in space and how it evolves with time at the early universe and provide valuable information about the large scale structure of the universe and its evolution. Based on intermediate resolution (1 ∼ 2 A) spectra, many authors (e.g. Lu et al. 1991) deduced that the evolutionary index γ ∼ 2, (dN/dz ∼ (1 + z)γ, dN/dz is the number of clouds per unit redshift interval at redshift z). It means that Ly α clouds have strong cosmological evolution. In recent years, there appear high-resolution (< 30km/sec) spectra of QSOs. High resolution spectra may provide more information than medium resolution spectra. Hence, it is necessary to study the evolution of Ly α clouds, using the spectra with higher resolution. Carswell et al. (1987) found γ=1 in the redshift interval 1.9–3.8. But Rauch et al. (1992) found γ=2.1 for the line sample with logN(HI) ≥ 13.75. It is more interesting that Giallongo (1991) found a differential evolution: γ is depended on the equivalent width W of line and no evolution for the strong line sample with 0.5 > W > 0.3. However, these studies involved very few QSOs (three or four). In this paper, we use a larger sample of QSOs to study the evolution of Ly α clouds.

scholarly journals Lithium in Young Open Clusters

2000 ◽  
Vol 198 ◽  
pp. 350-353 ◽  
Author(s):  
R. Pallavicini ◽  
S. Randich ◽  
J. R. Stauffer ◽  
S. C. Balachandran
Keyword(s):  
Temperature Distribution ◽  
High Resolution ◽  
General Framework ◽  
Main Sequence ◽  
Open Clusters ◽  
Late Type ◽  
Lithium Depletion ◽  
Young Clusters

We present lithium abundances for ∼50 late-type members of the ∼30 — 50 Myr old open clusters IC 2602 and IC 2391 derived from high-resolution spectra obtained at ESO and CTIO. These data enlarge and extend to cooler temperatures previous Li surveys of these clusters by Stauffer et al. (1989) and Randich et al. (1997). We discuss the lithium vs. temperature distribution in the two clusters and we compare our results with those obtained for the Pleiades (∼120 Myr). The results are discussed in the general framework of lithium depletion in young clusters, from the pre-main sequence to the age of the Pleiades.

scholarly journals High Resolution VLA Observations of Quasars with Distorted Radio Stucture

1982 ◽  
Vol 97 ◽  
pp. 39-40
Author(s):  
J. Stocke ◽  
W. Christiansen ◽  
J. Burns
Keyword(s):  
High Resolution ◽  
Dynamic Range ◽  
High Dynamic Range ◽  
Radio Galaxies ◽  
Cluster Membership ◽  
Double Structure ◽  
Structural Distortions ◽  
Extended Radio ◽  
High Dynamic ◽  
Structure Class

Most quasars with extended radio structures have the classical linear double structure (Class II) which is also characteristic of the most luminous radio galaxies. A very small fraction of quasars do, however, show deviations from the classical double structure which are similar to the distortions observed in some low luminosity radio galaxies, e.g., bent double sources. Among radio galaxies, structural distortions seem to be associated with membership in a cluster of galaxies. Indeed, Scott and Hintzen, 1978, have suggested that such distortions might be indicators of cluster membership for quasars as well. To test this hypothesis and examine the physics of distorted quasars, we have mapped the quasars 3C 270.1 and 3C 275.1 in both I and P using the VLA A-Array at 20 cm and 6 cm. Our high resolution (0.1 arc sec at 6 cm) and high dynamic range (200:1) observations demonstrate that the displaced components reported previously for these sources are indeed connected with the quasars themselves and, therefore, the distortions are not simply projection effects. We also report the discovery of a very narrow northwesterly pointing jet in the quasar 3C 275.1.

High-Resolution CCD Spectra of Stars in Globular Clusters.IX.The "Young" Clusters Ruprecht 106 and PAL 12

1997 ◽  
Vol 114 ◽  
pp. 180 ◽  
Author(s):  
Jeffrey A. Brown ◽  
George Wallerstein ◽  
Daniel Zucker
Keyword(s):  
High Resolution ◽  
Young Clusters

scholarly journals Stellar ages from stellar rotation

2008 ◽  
Vol 4 (S258) ◽  
pp. 357-362 ◽  
Author(s):  
Søren Meibom
Keyword(s):  
Open Clusters ◽  
The Sun ◽  
Stellar Rotation ◽  
Cluster Membership ◽  
Rotation Periods ◽  
Stellar Ages ◽  
Direct Measurements ◽  
Young Clusters ◽  
Definition Of ◽  
Membership Information

AbstractOur ability to determine stellar ages from measurements of stellar rotation, hinges on how well we can measure the dependence of rotation on age for stars of different masses. Rotation periods for stars in open clusters are essential to determine the relations between stellar age, rotation, and mass. Until recently, ambiguities in vsini data and lack of cluster membership information, prevented a clear empirical definition of the dependence of rotation on color. Direct measurements of stellar rotation periods for members in young clusters have now revealed a well-defined period-color relation. We show new results for the open clusters M35 and M34. However, rotation periods based on ground-based observations are limited to young clusters. The Hyades represent the oldest coeval population of stars with measured rotation periods. Measurements of rotation periods for older stars are needed to properly constrain the dependence of stellar rotation on age. We present our plans to use the Kepler space telescope to measure rotation periods in clusters as old as and older than the Sun.

Observations of the spatial structure of interstellar hydrogen

1967 ◽  
Vol 31 ◽  
pp. 45-46
Author(s):  
Carl Heiles
Keyword(s):  
High Resolution ◽  
Spatial Structure ◽  
Velocity Dispersion ◽  
Temperature Variations

High-resolution 21-cm line observations in a region aroundlII= 120°,b11= +15°, have revealed four types of structure in the interstellar hydrogen: a smooth background, large sheets of density 2 atoms cm-3, clouds occurring mostly in groups, and ‘Cloudlets’ of a few solar masses and a few parsecs in size; the velocity dispersion in the Cloudlets is only 1 km/sec. Strong temperature variations in the gas are in evidence.

Combining integrated systems-biology approaches with intervention-based experimental design provides a higher-resolution path forward for microbiome research

2019 ◽  
Vol 42 ◽  
Author(s):  
J. Alfredo Blakeley-Ruiz ◽  
Carlee S. McClintock ◽  
Ralph Lydic ◽  
Helen A. Baghdoyan ◽  
James J. Choo ◽  
...  
Keyword(s):  
Systems Biology ◽  
High Resolution ◽  
Experimental Design ◽  
Integrated Systems ◽  
Microbiome Research ◽  
Constructive Criticism

Abstract The Hooks et al. review of microbiota-gut-brain (MGB) literature provides a constructive criticism of the general approaches encompassing MGB research. This commentary extends their review by: (a) highlighting capabilities of advanced systems-biology “-omics” techniques for microbiome research and (b) recommending that combining these high-resolution techniques with intervention-based experimental design may be the path forward for future MGB research.

Very High Resolution Analysis of the Dynamics of a Coronal Plasmoid

1994 ◽  
Vol 144 ◽  
pp. 593-596
Author(s):  
O. Bouchard ◽  
S. Koutchmy ◽  
L. November ◽  
J.-C. Vial ◽  
J. B. Zirker
Keyword(s):  
High Resolution ◽  
Solar Eclipse ◽  
Total Solar Eclipse ◽  
Field Of View ◽  
Small Field ◽  
High Resolution Analysis ◽  
Ccd Observations ◽  
Resolution Analysis ◽  
Very High ◽  
Small Field Of View

AbstractWe present the results of the analysis of a movie taken over a small field of view in the intermediate corona at a spatial resolution of 0.5“, a temporal resolution of 1 s and a spectral passband of 7 nm. These CCD observations were made at the prime focus of the 3.6 m aperture CFHT telescope during the 1991 total solar eclipse.

FeXIV Line Emission Polarization of the July 11, 1991 Solar Corona

1994 ◽  
Vol 144 ◽  
pp. 541-547
Author(s):  
J. Sýkora ◽  
J. Rybák ◽  
P. Ambrož
Keyword(s):  
High Resolution ◽  
Solar Corona ◽  
Emission Line ◽  
Solar Eclipse ◽  
White Light ◽  
Preliminary Analysis ◽  
Line Emission ◽  
Total Solar Eclipse ◽  
Degree Of Polarization ◽  
High Resolution Images

AbstractHigh resolution images, obtained during July 11, 1991 total solar eclipse, allowed us to estimate the degree of solar corona polarization in the light of FeXIV 530.3 nm emission line and in the white light, as well. Very preliminary analysis reveals remarkable differences in the degree of polarization for both sets of data, particularly as for level of polarization and its distribution around the Sun’s limb.

Microcalorimeters for X-Ray Spectroscopy

1988 ◽  
Vol 102 ◽  
pp. 41
Author(s):  
E. Silver ◽  
C. Hailey ◽  
S. Labov ◽  
N. Madden ◽  
D. Landis ◽  
...  
Keyword(s):  
High Resolution ◽  
High Efficiency ◽  
Thermal Response ◽  
Low Noise ◽  
High Resolution Spectroscopy ◽  
Superconducting Transition ◽  
Sapphire Substrates ◽  
Laboratory Plasmas ◽  
Adiabatic Demagnetization ◽  
Theoretical Predictions

The merits of microcalorimetry below 1°K for high resolution spectroscopy has become widely recognized on theoretical grounds. By combining the high efficiency, broadband spectral sensitivity of traditional photoelectric detectors with the high resolution capabilities characteristic of dispersive spectrometers, the microcalorimeter could potentially revolutionize spectroscopic measurements of astrophysical and laboratory plasmas. In actuality, however, the performance of prototype instruments has fallen short of theoretical predictions and practical detectors are still unavailable for use as laboratory and space-based instruments. These issues are currently being addressed by the new collaborative initiative between LLNL, LBL, U.C.I., U.C.B., and U.C.D.. Microcalorimeters of various types are being developed and tested at temperatures of 1.4, 0.3, and 0.1°K. These include monolithic devices made from NTD Germanium and composite configurations using sapphire substrates with temperature sensors fabricated from NTD Germanium, evaporative films of Germanium-Gold alloy, or material with superconducting transition edges. A new approache to low noise pulse counting electronics has been developed that allows the ultimate speed of the device to be determined solely by the detector thermal response and geometry. Our laboratory studies of the thermal and resistive properties of these and other candidate materials should enable us to characterize the pulse shape and subsequently predict the ultimate performance. We are building a compact adiabatic demagnetization refrigerator for conveniently reaching 0.1°K in the laboratory and for use in future satellite-borne missions. A description of this instrument together with results from our most recent experiments will be presented.

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