scholarly journals Evidence of an evolved nature of MWC 349A

2020 ◽  
Vol 493 (3) ◽  
pp. 4308-4314 ◽  
Author(s):  
M Kraus ◽  
M L Arias ◽  
L S Cidale ◽  
A F Torres
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
Gas Temperature ◽  
Band Emission ◽  
Galactic Emission ◽  
Near Infrared Spectra ◽  
Infrared Spectral ◽  
Significant Enrichment ◽  
Excellent Tool ◽  
Radio Stars

ABSTRACT The Galactic emission-line object MWC 349A is one of the brightest radio stars in the sky. The central object is embedded in an almost edge-on oriented Keplerian rotating thick disc that seems to drive a rotating bipolar wind. The dense disc is also the site of hot molecular emission such as the CO bands with its prominent band heads in the near-infrared spectral range. Despite numerous studies, the nature of MWC 349A is still controversial with classifications ranging from a pre-main sequence object to an evolved supergiant. We collected new high-resolution near-infrared spectra in the K and Lbands using the GNIRS spectrograph at Gemini-North to study the molecular disc of MWC 349A, and in particular to search for other molecular species such as SiO and the isotope 13CO. The amount of 13CO, obtained from the 12CO/13CO ratio, is recognized as an excellent tool to discriminate between pre-main-sequence and evolved massive stars. We find no signatures of SiO band emission, but detect CO band emission with considerably lower intensity and CO gas temperature compared to previous observations. Moreover, from detailed modelling of the emission spectrum, we derive an isotope ratio of 12CO/13CO = 4 ± 1. Based on this significant enrichment of the circumstellar environment in 13CO, we conclude that MWC 349A belongs to the group of B[e] supergiants, and we discuss possible reasons for the drop in CO intensity.

N-way partial least squares combined with new self-construction strategy—A promising approach of using near infrared spectral data for quantitative determination of multiple compounds

2019 ◽  
Vol 28 (2) ◽  
pp. 113-121
Author(s):  
Xiang-Zhi Zhang ◽  
Ai-Jun Ma ◽  
Na Feng ◽  
Bao Qiong Li
Keyword(s):  
Quantitative Analysis ◽  
Least Squares ◽  
Partial Least Squares ◽  
Near Infrared ◽  
Least Squares Method ◽  
Three Dimensional ◽  
Near Infrared Spectra ◽  
Infrared Spectral ◽  
Construction Strategy ◽  
Partial Least Squares Method

Because of the complexity of near infrared spectral data, effective strategies are necessary proposed for accurate quantitative analysis purpose. This work explores a new self-construction strategy for the arrangement of conventional near infrared two-dimensional spectra into new self-constructed three-dimensional spectra, and investigate the feasibility of N-way partial least squares combined with the new self-constructed three-dimensional near infrared spectra for obtaining accurate quantitative determination results. A proof-of-concept model system, the quantitative analysis of four components (moisture, oil, protein, and starch) in corn samples, was applied to evaluate the performance of the proposed strategy. The ability of the newly proposed approach to predict the target compounds was checked with test samples. The established models have good predictive power for the target compounds with acceptable values of Rp (range from 0.82 to 0.997) and RMSEP (range from 0.03 to 0.47). Compared with partial least squares method on pretreated near infrared spectra and N-way partial least squares method on the basis of near infrared self-constructed three-dimensional spectra, the proposed method is competitive.

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.

Near- versus Mid-Infrared Spectroscopy: Relationships between Spectral Changes Induced by Water and Relative Information Content of the Two Spectral Regions in Regard to High-Moisture Samples

1995 ◽  
Vol 49 (3) ◽  
pp. 295-303 ◽  
Author(s):  
James B. Reeves
Keyword(s):  
Infrared Spectra ◽  
Near Infrared ◽  
High Moisture ◽  
Mid Infrared ◽  
Spectral Changes ◽  
Near Infrared Spectra ◽  
Infrared Spectral ◽  
Water Ph ◽  
Relative Information Content ◽  
Relationship Of

The objectives of this work were to examine similarities and differences in the near-infrared and mid-infrared spectral regions when one is working with high-moisture materials and to study spectral changes in these regions as a method to identify the relationship of spectral information in the near-IR to fundamental absorptions in the mid-IR. Near- and mid-infrared spectra were taken with a Digilab FTS-65 Fourier transform spectrometer. Liquids were examined by transmission and solids by reflectance. Results with solutions showed that less spectral distortion arises when one is subtracting water from mid- rather than from near-infrared spectra. It was also easier to produce high-quality spectra in the mid-infrared by using attenuated total reflectance than by using transmission in the near-infrared. While mid-infrared spectra showed changes (induced by water, pH, physical state, and ionic strength) similar to those found in the near-infrared, there appeared to be more information available in the mid-infrared, even in the presence of water.

scholarly journals Rapid identification of Lactobacillus species using near infrared spectral features of bacterial colonies

2019 ◽  
Vol 27 (4) ◽  
pp. 302-313
Author(s):  
Jiyong Shi ◽  
Xuetao Hu ◽  
Xiaobo Zou ◽  
Zhiming Guo ◽  
Mel Holmes ◽  
...  
Keyword(s):  
Support Vector Machine ◽  
Near Infrared ◽  
Rapid Identification ◽  
Lactobacillus Species ◽  
Support Vector ◽  
Spectral Features ◽  
Mid Infrared ◽  
Near Infrared Spectra ◽  
Infrared Spectral ◽  
Chemical Groups

The feasibility of rapid identification of Lactobacillus species using near-infrared spectral features coupled with chemometrics was investigated. First, bacterial colonies of 11 Lactobacillus strains covering four species ( Lactobacillus casei, Lactobacillus reuteri, Lactobacillus brevis, and Lactobacillus fermentum) were cultured using the spread-plate technique. Near-infrared spectra data of the Lactobacillus species were collected directly from the bacterial colonies. Second, 10 wavenumbers were selected from the near-infrared spectra data using uninformative variables elimination and genetic algorithm, and calibration models based on the 10 selected wavenumbers were built using least squares support vector machine. The identification rates for the prediction set and validation set were 89.04 and 85%, respectively. Third, chemical groups of the Lactobacillus cells contributing to the identification of the Lactobacillus strains were identified using mid infrared. The results of mid infrared data analysis indicated that 9 chemical groups could be considered characteristics for categorizing the 11 Lactobacillus strains. The relationship between the 10 selected wavenumbers and identified chemical groups was identified, which supported the satisfactory performance of the least squares support vector machine calibration model. This study demonstrated that near-infrared spectral features of bacterial colonies could be used for Lactobacillus typing at the strain level.

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.

scholarly journals Red and Near Infrared Spectra* of Pre-Main Sequence Stars I. A Preliminary Investigation of T Tauri Stars

1977 ◽  
Vol 42 ◽  
pp. 100-105 ◽  
Author(s):  
Y. Andrillat
Keyword(s):  
Color Index ◽  
Main Sequence ◽  
Near Infrared ◽  
Preliminary Investigation ◽  
Visible Spectrum ◽  
T Tauri Stars ◽  
Main Sequence Stars ◽  
Type K ◽  
T Tauri ◽  
Near Infrared Spectra

230 Å mm-1 spectra of 30 stars of T Tauri or related type were obtained in the 8000-11000 Å region using a grating spectrograph equipped with an S-1 photocathode image-tube. In addition a few T Tauri stars were observed at the same dispersion in the 6200-8800 Å region on IN plate. A preliminary qualitative analysis of the observations leads to possible correlations between the intensities of emissions of the Ca II triplet, Paschen series and He I 10830 Å, and the spectral type, K-L color index of the star, or the [0 I] and Fe II intensities in the visible spectrum.

scholarly journals Characterizing stellar parameters from high-resolution spectra of main sequence cool stars. I. The G2V–K2V stars

2019 ◽  
Vol 487 (1) ◽  
pp. 1335-1362
Author(s):  
Logithan Kulenthirarajah ◽  
Jean-François Donati ◽  
Gaitee Hussain ◽  
Julien Morin ◽  
France Allard
Keyword(s):  
High Resolution ◽  
Main Sequence ◽  
Near Infrared ◽  
Absolute Accuracy ◽  
Spectral Library ◽  
M Dwarfs ◽  
Near Infrared Spectra ◽  
Cool Stars ◽  
Error Bars ◽  
Good Agreement

Abstract The goal of the present study is to construct, test, and validate a high-resolution synthetic spectral library using PHOENIX model atmospheres and develop a reliable tool to estimate stellar parameters from high-resolution optical and/or near-infrared spectra of M dwarfs. We report here the preliminary results of tests characterizing main sequence G–K stars from high-resolution spectra. We anchored the atomic line-list using the stellar standards Sun, ξ Boo A, and ϵ Eri to ensure the synthetic spectra computed with PHOENIX reproduce their observed counterparts. These stars were chosen because their parameters are very well characterized, and on which the absolute accuracy of our method depends on. We successfully estimated the stellar parameters with associated error bars for 17 stars. Using a pseudo Monte Carlo statistical analysis, we present overall improved uncertainties on the stellar parameters compared to those in the literature (on average 9 K, 0.014 dex, and 0.008 dex for the effective temperature, the surface gravity, and the metallicity, respectively). Our estimated stellar parameters are also in good agreement with values found in the literature.

A data-driven near infrared calibration process including near infrared spectral thumbprints

2018 ◽  
Vol 26 (3) ◽  
pp. 169-185
Author(s):  
Sharon Nielsen ◽  
Kenneth G Russell ◽  
Alison Kelly ◽  
Glen Fox
Keyword(s):  
Infrared Spectra ◽  
Near Infrared ◽  
Calibration Model ◽  
Calibration Process ◽  
Near Infrared Spectra ◽  
Infrared Spectral ◽  
Highly Correlated ◽  
Complex Relationships ◽  
High Level ◽  
The Relationship

Near infrared spectra are highly correlated, complex and noisy, and potentially have many more predictor variables than are required to estimate a parsimonious calibration equation. It is difficult to appreciate the implication of pre-processing choices that are made during calibration, especially in connection with the relationship between the transformed data and the reference values. Graphical methods can be used to understand these relationships better and decisions made during the calibration process can be based on the data alone. In this paper, new graphical tools are introduced to help the researcher better understand these complex relationships in the data. When combined with the proposed algorithm to explore spectra in relation to calibration, these tools enable a parsimonious calibration model to be formed. The results from two different (diesel and wheat) near infrared spectra show that it is possible to form successful calibration equations based on the proposed algorithm, which includes the two new graphical tools. There is a high level of correlation between the results of the different transformations considered, suggesting that in terms of parsimony, developing a calibration using the raw spectra could provide the most judicious outcome.

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