scholarly journals Near Infrared Spectra of Southern Be Stars

1987 ◽  
Vol 92 ◽  
pp. 239-241
Author(s):  
L. Pastori
Keyword(s):  
Infrared Spectra ◽  
Spectral Type ◽  
Near Infrared ◽  
Infrared Region ◽  
Bright Star ◽  
Be Stars ◽  
Star Catalogue ◽  
Near Infrared Spectra ◽  
Near Infrared Region ◽  
Right Ascension

Spectra of northern Be stars in the near infrared region have been already described by some authors (see Slettebak, 1979 for a brief review). This paper presents general results for southern Be stars obtained from more than 100 spectrograms in the region λλ7750-9000 Å the spectra were taken in four nights of February 1985 at the 1.5m ESO telescope with the reticon instrumentation; the dispersion is 58 Åmm-1. All the available southern Be stars (right ascension between 4h and 17h) listed in the Bright Star Catalogue (Hoffleit and Jaschek, 1982) were observed. Table 1 lists the number of stars vs. spectral type (columns 1 and 2) and the number of stars which display emission at the Paschen series, 0I λ8446 Å and Call triplet (columns 3 to 5).

Near infrared spectra of some cobalt(II) compounds

1968 ◽  
Vol 21 (7) ◽  
pp. 1775
Author(s):  
DP Graddon ◽  
GM Mockler
Keyword(s):  
Absorption Band ◽  
Absorption Spectra ◽  
Metal Atom ◽  
Infrared Spectra ◽  
Near Infrared ◽  
Infrared Region ◽  
Absorption Bands ◽  
Heterocyclic Base ◽  
Near Infrared Spectra ◽  
Near Infrared Region

Absorption spectra of compounds CoX2B2 and CoX2B4 (X = Cl, Br, I, or NCS; B = a heterocyclic base) have been obtained by reflectance and in solution in the near infrared region between 1000 and 2000 mμ. The spectra are characteristic of the stereochemistry of the metal atom: octahedral compounds have a single absorption band near 1100 mμ, e < 10; tetrahedral compounds have three overlapping absorption bands near 1100,1400, and 1700 mp, 30 < < 150. Comparisons are made with previously observed spectra of octahedral and tetrahedral species of the types CoL2+6 and CoX2-4.

Mid and near Infrared Study of Carbohydrates by Canonical Correlation Analysis

1993 ◽  
Vol 1 (2) ◽  
pp. 99-108 ◽  
Author(s):  
P. Robert ◽  
M.F. Devaux ◽  
A. Qannari ◽  
M. Safar
Keyword(s):  
Correlation Analysis ◽  
Infrared Spectra ◽  
Canonical Correlation ◽  
Near Infrared ◽  
Sugar Content ◽  
Infrared Region ◽  
Total Sugar ◽  
Mid Infrared ◽  
Total Sugar Content ◽  
Near Infrared Spectra

Multivariate data treatments were applied to mid and near infrared spectra of glucose, fructose and sucrose solutions in order to specify near infrared frequencies that characterise each carbohydrate. As a first step, the mid and near infrared regions were separately studied by performing Principal Component Analyses. While glucose, fructose and sucrose could be clearly identified on the similarity maps derived from the mid infrared spectra, only the total sugar content of the solutions was observed when using the near infrared region. Characteristic wavelengths of the total sugar content were found at 2118, 2270 and 2324 nm. In a second step, the mid and near infrared regions were jointly studied by a Canonical Correlation Analysis. As the assignments of frequencies are generally well known in the mid infrared region, it should be useful to study the relationships between the two infrared regions. Thus, the canonical patterns obtained from the near infrared spectra revealed wavelengths that characterised each carbohydrate. The OH and CH combination bands were observed at: 2088 and 2332 nm for glucose, 2134 and 2252 nm for fructose, 2058 and 2278 nm for sucrose. Although a precise assignment of the near infrared bands to chemical groups within the molecules was not possible, the present work showed that near infrared spectra of carbohydrates presented specific features.

Quantum mechanical simulations of near-infrared spectra of biomolecules – Long-chain fatty acids

NIR news ◽  
2018 ◽  
Vol 29 (6) ◽  
pp. 13-19 ◽  
Author(s):  
Krzysztof B Beć ◽  
Justyna Grabska
Keyword(s):  
Fatty Acids ◽  
Infrared Spectra ◽  
Near Infrared ◽  
Infrared Region ◽  
Quantum Mechanical ◽  
Long Chain Fatty Acids ◽  
Near Infrared Spectra ◽  
Technical Article ◽  
Long Chain ◽  
Chain Fatty Acids

Exact and in-depth interpretation of near-infrared spectra has often appeared problematic in any case stepping beyond the simplest molecules. The inherent complexity of near-infrared spectra due to the abundance of combination modes and the resulting extensive band overlay frequently limits our comprehension of the spectral bands to vague wavenumber regions in which certain modes likely appear. Coincidently, quantum mechanical simulation of spectra which could offer momentous support in solving such problems has rather been rare in the case of near-infrared region due to practical limitations. Recent years have seen a trending development of accurate and affordable methods of near-infrared spectra simulation. A trend in modelling increasingly complex molecules can be noticed reaching even fairly large biomolecules. In this technical article we overview the most recent accomplishments in the field on the example of long-chain fatty acids and their cyclic dimers, which extend beyond 100 atoms.

scholarly journals The number of Be stars compared with the number of B stars, taking into account the specific physical characteristics of Be stars

1994 ◽  
Vol 162 ◽  
pp. 356-357
Author(s):  
D. Briot ◽  
J. Zorec
Keyword(s):  
Spectral Type ◽  
Bright Star ◽  
Physical Parameters ◽  
Emission Characteristics ◽  
Be Stars ◽  
Constant Mass ◽  
B Stars ◽  
The Past ◽  
Star Catalogue

It is very important for the understanding of the Be phenomenon, and particularly for locating a possible Be phase in the evolutionary track of B stars, to accurately determine the proportion of Be stars among all B stars. This type of study was already made several times in the past. Results obtained generally show a maximum Be frequency around spectral type B2 then a decrease towards late spectral types. Actually Be stars do not have the same characteristics as “normal” B stars and we have to take this into account in the determination of the ratio : number of Be stars / number of B stars. We use the Bright Star Catalogue (Hoffleit & Jaschek 1982) and the Supplement to the Bright Star Catalogue (Hoffleit, Saladyga & Wlasuk 1983) containing stars V= 7.10 and brighter. This study needed to be made separately for the different spectral types because:- Physical parameters of B stars are very different from B0 to B9;- Emission characteristics of Be stars vary very much, with a decrease from B0e to B9e.We successively consider three effects which can influence the frequency of Be stars:- The over-luminosity of Be stars as compared with B stars;- Spectral type changes during constant mass evolution;- Spectral type changes due to the fast rotation of Be stars.

scholarly journals Search and characterization of T-type planetary mass candidates in the σ Orionis cluster

2010 ◽  
Vol 6 (S276) ◽  
pp. 489-490
Author(s):  
Karla Peña Ramírez ◽  
Maria R. Zapatero Osorio ◽  
Victor J.S. Béjar
Keyword(s):  
Infrared Spectra ◽  
Spectral Type ◽  
Spectroscopic Data ◽  
Near Infrared ◽  
Cluster Membership ◽  
Planetary Mass ◽  
Near Infrared Spectra ◽  
Motion Measurements ◽  
Astrometric Data

AbstractWe present new photometric and astrometric data available for S Ori 70 and 73, the two T-type planetary-mass member candidates in the σ Orionis cluster (~3 ± 2 Myr, d~360 pc). S Ori 70 (J ~ 19.9 mag) has a spectral type of T5.5 ± 1.0 measured from published near-infrared spectra, while no spectroscopic data are available for S Ori 73 (J ~ 21 mag). We estimate the spectral type of S Ori 73 by using J, H, and CH4off (λc=1.575 μm, Δλ=0.112 μm) photometry and comparing the H-CH4off index of S Ori 73 with the colors of field stars and brown dwarfs of spectral types in the range F to late T. The locations of S Ori 70 and 73 in the J-H vs H-CH4off color-color diagram are consistent with spectral types T8 ± 1 and T4 ± 1, respectively. Proper motion measurements of the two sources are larger than the motion of the central σ Ori star, making their cluster membership somehow uncertain.

scholarly journals Recent advances in modeling vibrational spectra of food adulterants – Theoretical simulation of IR and NIR bands of melamine

NIR news ◽  
2019 ◽  
Vol 30 (4) ◽  
pp. 5-10
Author(s):  
Krzysztof B Beć
Keyword(s):  
Infrared Spectroscopy ◽  
Near Infrared ◽  
Infrared Region ◽  
Spectral Information ◽  
Complex Data ◽  
Theoretical Simulation ◽  
Methods Of Analysis ◽  
Near Infrared Spectra ◽  
Near Infrared Region ◽  
Detection And Quantification

Food safety may be one of the major concerns of the global society in the forthcoming decades. Analytical vibrational spectroscopy is expected to become a major tool used for controlling the food quality at every stage of its production, storage and delivery. Near-infrared and infrared spectroscopy have rapidly been evolving in analytical applications over the last decades with strong hyphenation to numerical and statistical methods of analysis of complex data, which are known as chemometrics. Analytical spectroscopy has reached a remarkable value for both industrial and institutional laboratories nowadays. However, the routinely used methods of analysis do not attempt to interpret the analysed spectral information in physicochemical sense. Therefore, analytical routines seldom take advantage of the molecular background underlying the properties of analysed sample. In the present article, we review the most recent accomplishments that evidence the progress which may be achieved when that background becomes actually available. We focus on the example of infrared and near-infrared spectra simulation applied to melamine, one of the most infamous food adulterant. This sheds light on the correspondences between infrared and near-infrared region observed earlier in the analytical papers dealing with detection and quantification of melamine in food products.

scholarly journals FI Lyr: A Candidate Binary System Consisting of Carbon-Rich and Oxygen-Rich Companions

1993 ◽  
Vol 155 ◽  
pp. 334-334
Author(s):  
J.J. Wang ◽  
J.Y. Hu ◽  
X. Zhou
Keyword(s):  
Binary System ◽  
Infrared Spectra ◽  
Spectral Type ◽  
Near Infrared ◽  
Dust Shell ◽  
Near Infrared Spectra

FI Lyr=IRAS18401+2854 is listed in the GCVS as type of SRb, the spectral type is M. In the IRAS LRS Catalog it is classified as 41, namely having the SiC feature at 11.3μm from a carbon-rich dust shell. We have obtained optical and near infrared spectra in the same period, but they show different chemical natures. We suggest that FI Lyr is a good candidate of a binary system consisting of carbon-rich and oxygen-rich companions.

scholarly journals Anomalous Spectral Types and Intrinsic Colors of Young Stars

2015 ◽  
Vol 10 (S314) ◽  
pp. 85-90 ◽  
Author(s):  
Mark J. Pecaut
Keyword(s):  
Infrared Spectra ◽  
Spectral Type ◽  
Main Sequence ◽  
Near Infrared ◽  
Systematic Errors ◽  
Optical Spectra ◽  
Young Stars ◽  
Main Sequence Stars ◽  
Near Infrared Spectra ◽  
Dynamical Masses

AbstractWe highlight differences in spectral types and intrinsic colors observed in pre-main sequence (pre-MS) stars. Spectral types of pre-MS stars are wavelength-dependent, with near-infrared spectra being 3-5 spectral sub-classes later than the spectral types determined from optical spectra. In addition, the intrinsic colors of young stars differ from that of main-sequence stars at a given spectral type. We caution observers to adopt optical spectral types over near-infrared types, since Hertzsprung-Russell (H-R) diagram positions derived from optical spectral types provide consistency between dynamical masses and theoretical evolutionary tracks. We also urge observers to deredden pre-MS stars with tabulations of intrinsic colors specifically constructed for young stars, since their unreddened colors differ from that of main sequence dwarfs. Otherwise, V-band extinctions as much as ~0.6 mag erroneously higher than the true extinction may result, which would introduce systematic errors in the H-R diagram positions and thus bias the inferred ages.

scholarly journals Spectea of Of and Be Stabs in the near Infrared Region up to 1.1μ

1979 ◽  
Vol 47 ◽  
pp. 137-150
Author(s):  
Yvette Andrillat
Keyword(s):  
Near Infrared ◽  
Infrared Region ◽  
Be Stars ◽  
Small Interval ◽  
Extended Study ◽  
Near Infrared Region ◽  
Temperature Class ◽  
Made In

AbstractThe classification of Of stars presents a number of problems, in part due to the small interval of the spectrum explored up to now. With J.M. Vreux an extended study has been made in the infrared region, up to 1.1μ. Be stars have been studied with L. Houziaux, The hydrogen Paschen lines and lines of helium I and II can be studied in the region and used to determine temperature class and luminosity.

scholarly journals Near Infrared Spectra of 103 Bright Be Stars

1987 ◽  
Vol 92 ◽  
pp. 237-238
Author(s):  
Y. Andrillat
Keyword(s):  
Spectral Range ◽  
Infrared Spectra ◽  
Near Infrared ◽  
High Dispersion ◽  
Be Stars ◽  
Near Infrared Spectra ◽  
Low Dispersion

We have observed 103 bright Be stars in the near infrared up to 10500 A with a dispersion of 230 and 50 A mm-1. The observations were performed with a Reticon (1024 diodes) attached to the ROUCAS spectrograph at the 193 cm telescope of the Haute Provence Observatory.In this spectral range, the Be stars are characterized by the lines of HI (Paschen series), 0I(7772-74-75, 8446 A), CaII(8542, 8662, 8498 A), FeII(7712, 9997 A) and NI(8686-83-80, 8719-12-03, 8629 A).On our spectra, the CaII triplet is always blended with P13, P15, P16, and only the enhancement of these lines permits to conclude to the CaII presence. The 0I 8446 A is perturbed by the Paschen lines P17 and P18 (low dispersion spectra) and P18 (high dispersion spectra). The NI 8686-83-80 A lines also perturb the P13 profile.

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