The Titanium Comparison Spectrum as a Photometric Scale

1931 ◽  
Vol 73 ◽  
pp. 118 ◽  
Author(s):  
Philip C. Keenan
Keyword(s):  
Comparison Spectrum ◽  
Photometric Scale

scholarly journals XIX. On the photographic arc spectrum of iron meteorites

1894 ◽  
Vol 185 ◽  
pp. 1023-1028
Keyword(s):  
Royal Society ◽  
Solar Spectrum ◽  
British Museum ◽  
Iron Meteorites ◽  
Electrolytic Iron ◽  
Comparison Spectrum ◽  
Size And Shape ◽  
Previous Communication ◽  
Oxyhydrogen Flame ◽  
Made In

In a communication to the Royal Society in 1887, I gave an account of certain experiments which I had made in connection with the spectra of various meteorites at various temperatures. The spectra were observed at the temperature of the oxyhydrogen flame and the electric spark without jar, and when glowed in vacuum tubes. Some larger specimens of the iron meteorites, Nejed and Obernkirchen, cut so that they were of a size and shape suitable for forming the poles of an arc lamp, having afterwards been kindly placed at my disposal by the Trustees of the British Museum, it became possible to study the arc spectra of these meteorites under very favourable conditions, all impurities introduced by the use of the carbon poles being thus avoided. The region of the spectrum photographed extends from K to D, in the case of each meteorite, and in addition to the solar spectrum, that of electrolytic iron, prepared by Professor Roberts-Austen, referred to in a previous communication, has been used as a comparison spectrum in one case.

Thorium Comparison Spectrum

1975 ◽  
Vol 29 ◽  
pp. 97 ◽  
Author(s):  
James B. Breckinridge ◽  
A. Keith Pierce ◽  
Clifford P. Stoll
Keyword(s):  
Comparison Spectrum

scholarly journals The San Pedro Mártir Open Cluster Survey: Progress, Techniques, Preliminary Results

2006 ◽  
Vol 2 (S235) ◽  
pp. 331-331 ◽  
Author(s):  
W. Schuster ◽  
R. Michel ◽  
W. Dias ◽  
T. Tapia-Peralta ◽  
R. Vázquez ◽  
...  
Keyword(s):  
Open Cluster ◽  
Open Clusters ◽  
Small Subset ◽  
Main Sequence Stars ◽  
San Pedro ◽  
Reduction Methods ◽  
Red Clump ◽  
Different Color ◽  
Photometric Scale ◽  
Selection Of

AbstractA CCD UBVRI survey of northern open clusters is being undertaken at San Pedro Mártir, México, and performed using always the same instrumental setup (telescope, CCD, filters), reduction methods, and system of standards of Landolt (1992). To date more than 300 clusters (mostly unstudied previously) have been observed, and about half the data reduced using aperture-photometry and PSF techniques. Our analysis procedures are being refined by studying in detail a small subset of these clusters. For example, the heavily reddened clusters Be80 and Be95 are being examined in the color-color diagrams: (B-V, U-B) and (B-V, R-I) to better understand the problems of curvature and variable reddening. For clusters for which our U data reaches the F-type stars, such as NGC2192 and NGC7296, techniques are being examined for estimating both the reddening E(B-V) and metallicity [Fe/H] via the use of the (U-B) excess. If the clusters also have “red clump” stars, such as NGC1798 and Do02, these procedures can be iterated between the clump and main sequence stars to establish even better the values of E(B-V) and [Fe/H]. Finally, color-magnitude diagrams, such as (B-V, V) and (V-I, V), are being employed together with the SchmidtKaler (1982) colors and Padova isochrones of Girardi et al. (2000) to obtain distances and ages for these clusters. A java-based computer program is being developed to help in the visualization and analysis of these photometric data. This system is capable of displaying each cluster simultaneously in different color-color and color-magnitude diagrams and has an interactive way to identify a star, or group of stars, in one diagram and to see were it falls in the other diagrams, facilitating the elimination of field stars and the apperception of cluster features. This program is capable of displaying up to 16 different diagrams for one cluster and processing up to 20 clusters at the same time. Our aims are the following: (1) a common UBVRI photometric scale for open clusters, (2) an atlas of color-color and color-magnitude diagrams for open clusters, (3) a homogeneous set of cluster reddenings, distances, and ages, (4) an increased number of old and distant open clusters, and (5) a selection of interesting clusters for further study.

National Institute of Standards and Technology detector-based photometric scale

1993 ◽  
Vol 32 (16) ◽  
pp. 2936 ◽  
Author(s):  
C. L. Cromer ◽  
G. Eppeldauer ◽  
J. E. Hardis ◽  
T. C. Larason ◽  
A. C. Parr
Keyword(s):  
Photometric Scale

scholarly journals Facing problems in the determination of stellar temperatures and gravities: Galactic globular clusters

2020 ◽  
Vol 640 ◽  
pp. A87 ◽  
Author(s):  
A. Mucciarelli ◽  
P. Bonifacio
Keyword(s):  
Low Temperatures ◽  
Globular Clusters ◽  
Simple Relation ◽  
Spectroscopic Parameters ◽  
Giant Stars ◽  
Excitation Potential ◽  
Galactic Globular Clusters ◽  
Stellar Temperatures ◽  
Red Giant ◽  
Photometric Scale

We analysed red giant branch stars in 16 Galactic globular clusters, computing their atmospheric parameters both from the photometry and from excitation and ionisation balances. The spectroscopic parameters are lower than the photometric ones and this discrepancy increases with decreasing metallicity, reaching differences of ~350 K in effective temperature and ~1 dex in surface gravity at [Fe/H] ~ –2.5 dex. We demonstrate that the spectroscopic parameters are inconsistent with the position of the stars in the colour-magnitude diagram, providing overly low temperatures and gravities, and predicting that the stars are up to about 2.5 magnitudes brighter than the observed magnitudes. The parameter discrepancy is likely due to inadequacies in the adopted physics; in particular the assumption of a one-dimensional geometry could be the origin of the observed slope between iron abundances and excitation potential that leads to low temperatures. However, the current modelling of 3D/NLTE radiative transfer for giant stars seems to be unable to totally erase this slope. We conclude that the spectroscopic parameters are incorrect for metallicity lower than –1.5 dex and that photometric temperatures and gravities should be adopted for these red giant stars. We provide a simple relation to correct the spectroscopic temperatures in order to put them onto a photometric scale.

scholarly journals The Calibration of Stellar Spectra Used in Measurements of the Generalized Compton Shift

1985 ◽  
Vol 111 ◽  
pp. 595-597
Author(s):  
M. Missana
Keyword(s):  
Spectral Range ◽  
Planetary Nebula ◽  
Thomson Scattering ◽  
Compton Effect ◽  
Spectral Lines ◽  
Comparison Spectrum ◽  
Stellar Spectra ◽  
The Continuum

In the study of the changes induced by the Compton effect and Thomson scattering on the shape of spectral lines in light traversing a chromosphere or a planetary nebula it is necessary to have accurate wavelength measurements, central intensities and half widths (FWHM) of the lines. In the comparison of FWHM measures belonging to different spectra it is useful to have the intensities of the continuum at the wavelengths of the lines. The studied spectra should have a dispersion higher than 10 Å/mm and a spectral range larger than 700 Å. A short recommendation is also given about the comparison spectrum and the calibration plate.

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