NIR Low-Resolution Spectroscopy of L-Dwarfs: An Efficient Classification Scheme for Faint Dwarfs

2003 ◽  
pp. 187-194
Author(s):  
Leonardo Testi ◽  
Francesca D’Antona ◽  
Francesca Ghinassi ◽  
Javier Licandro ◽  
Antonio Magazzù ◽  
...  
Keyword(s):  
Classification Scheme ◽  
Low Resolution ◽  
L Dwarfs

NIR Low-Resolution Spectroscopy of L-Dwarfs: An Efficient Classification Scheme for Faint Dwarfs

2002 ◽  
pp. 186-192
Author(s):  
Leonardo Testi ◽  
Francesca D’Antona ◽  
Francesca Ghinassi ◽  
Javier Licandro ◽  
Antonio Magazzù ◽  
...  
Keyword(s):  
Classification Scheme ◽  
Low Resolution ◽  
L Dwarfs

NICS-TNG Low-Resolution 0.85–2.45 micron Spectra of L Dwarfs: A Near-Infrared Spectral Classification Scheme for Faint Dwarfs

2001 ◽  
Vol 552 (2) ◽  
pp. L147-L150 ◽  
Author(s):  
L. Testi ◽  
F. D’Antona ◽  
F. Ghinassi ◽  
J. Licandro ◽  
A. Magazzù ◽  
...  
Keyword(s):  
Near Infrared ◽  
Classification Scheme ◽  
Spectral Classification ◽  
Low Resolution ◽  
Infrared Spectral ◽  
L Dwarfs

scholarly journals An Efficient Low-Resolution NIR Classification Scheme for M, L, and T dwarfs and Its Application to Young BDs

2003 ◽  
Vol 211 ◽  
pp. 359-360
Author(s):  
L. Testi ◽  
A. Natta ◽  
C. Baffa ◽  
G. Comoretto ◽  
S. Gennari ◽  
...  
Keyword(s):  
Near Infrared ◽  
Classification Scheme ◽  
Optical Element ◽  
System Throughput ◽  
Single Shot ◽  
Low Resolution ◽  
Near Infrared Spectra ◽  
Infrared Spectral ◽  
High System ◽  
Large Telescopes

We present the preliminary results of a programme aimed at defining a low-resolution near-infrared spectral classification scheme for faint M, L, and T-dwarfs. The method is based on the global shape of R˜100 complete near-infrared spectra from 0.8 to 2.4μm as obtained through a high-throughput prism-based optical element, the Amici device, mounted inside the NICS instrument at the TNG 3.5m telescope (Baffa et al. 2001; Oliva 2000). The aim of our project is to provide an efficient classification scheme based on very low-resolution near infrared spectroscopy, which can be carried on at a 4m-class telescope. The results for the L-type dwarfs have already been presented in Testi et al. (2001), sample spectra for the M and T-dwarfs range are shown in Figure 1. A preliminary application of the method to the classification of young embedded brown-dwarf candidates has been successfully attempted by Testi et al. (2002) and Natta et al. (2002). The method is shown to be accurate and competitive: the high system throughput coupled with the possibility of obtaining in a “single shot” the complete spectrum of the objects make the NICS/TNG system more efficient than existing large telescopes.

Statistical analysis of classification

1966 ◽  
Vol 24 ◽  
pp. 188-189
Author(s):  
T. J. Deeming
Keyword(s):  
Multivariate Analysis ◽  
Statistical Analysis ◽  
Classification Scheme ◽  
Analytical Procedure ◽  
Narrow Band ◽  
Scientific Research ◽  
Maximum Amount ◽  
Amount Of Information

If we make a set of measurements, such as narrow-band or multicolour photo-electric measurements, which are designed to improve a scheme of classification, and in particular if they are designed to extend the number of dimensions of classification, i.e. the number of classification parameters, then some important problems of analytical procedure arise. First, it is important not to reproduce the errors of the classification scheme which we are trying to improve. Second, when trying to extend the number of dimensions of classification we have little or nothing with which to test the validity of the new parameters.Problems similar to these have occurred in other areas of scientific research (notably psychology and education) and the branch of Statistics called Multivariate Analysis has been developed to deal with them. The techniques of this subject are largely unknown to astronomers, but, if carefully applied, they should at the very least ensure that the astronomer gets the maximum amount of information out of his data and does not waste his time looking for information which is not there. More optimistically, these techniques are potentially capable of indicating the number of classification parameters necessary and giving specific formulas for computing them, as well as pinpointing those particular measurements which are most crucial for determining the classification parameters.

Introductory paper

1966 ◽  
Vol 24 ◽  
pp. 3-5
Author(s):  
W. W. Morgan
Keyword(s):  
Line Intensity ◽  
Classification Scheme ◽  
Two Dimensional ◽  
Spectral Classification ◽  
Dimensional Array ◽  
Rr Lyrae ◽  
Metallic Line ◽  
Introductory Paper ◽  
Parameter Varying ◽  
Definition Of

1. The definition of “normal” stars in spectral classification changes with time; at the time of the publication of theYerkes Spectral Atlasthe term “normal” was applied to stars whose spectra could be fitted smoothly into a two-dimensional array. Thus, at that time, weak-lined spectra (RR Lyrae and HD 140283) would have been considered peculiar. At the present time we would tend to classify such spectra as “normal”—in a more complicated classification scheme which would have a parameter varying with metallic-line intensity within a specific spectral subdivision.

A Perturbation Theory for the Population of Atomic Energy Levels in Non-Lte Plasmas

1988 ◽  
Vol 102 ◽  
pp. 343-347
Author(s):  
M. Klapisch
Keyword(s):  
Perturbation Theory ◽  
Small Parameter ◽  
Classification Scheme ◽  
Sum Rules ◽  
Energy Levels ◽  
Natural Classification ◽  
Quantum Numbers ◽  
Formal Expansion ◽  
Atomic Energy Levels ◽  
As Effects

AbstractA formal expansion of the CRM in powers of a small parameter is presented. The terms of the expansion are products of matrices. Inverses are interpreted as effects of cascades.It will be shown that this allows for the separation of the different contributions to the populations, thus providing a natural classification scheme for processes involving atoms in plasmas. Sum rules can be formulated, allowing the population of the levels, in some simple cases, to be related in a transparent way to the quantum numbers.

The value of Electron Microscope studies of imperfect natural diamonds

1990 ◽  
Vol 48 (4) ◽  
pp. 194-195
Author(s):  
J C Walmsley ◽  
A R Lang
Keyword(s):  
Electron Microscope ◽  
Classification Scheme ◽  
Natural Diamond ◽  
Sudden Change ◽  
Growth Conditions ◽  
Diamond Growth ◽  
Major Constituent ◽  
Natural Diamonds ◽  
Type Ia ◽  
Platelet Defects

Interest in the defects and impurities in natural diamond, which are found in even the most perfect stone, is driven by the fact that diamond growth occurs at a depth of over 120Km. They display characteristics associated with their origin and their journey through the mantle to the surface of the Earth. An optical classification scheme for diamond exists based largely on the presence and segregation of nitrogen. For example type Ia, which includes 98% of all natural diamonds, contain nitrogen aggregated into small non-paramagnetic clusters and usually contain sub-micrometre platelet defects on {100} planes. Numerous transmission electron microscope (TEM) studies of these platelets and associated features have been made e.g. . Some diamonds, however, contain imperfections and impurities that place them outside this main classification scheme. Two such types are described.First, coated-diamonds which possess gem quality cores enclosed by a rind that is rich in submicrometre sized mineral inclusions. The transition from core to coat is quite sharp indicating a sudden change in growth conditions, Figure 1. As part of a TEM study of the inclusions apatite has been identified as a major constituent of the impurity present in many inclusion cavities, Figure 2.

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