scholarly journals S Coronae Australis: a T Tauri twin

2018 ◽  
Vol 614 ◽  
pp. A117 ◽  
Author(s):  
G. F. Gahm ◽  
P. P. Petrov ◽  
L. V. Tambovsteva ◽  
V. P. Grinin ◽  
H. C. Stempels ◽  
...  
Keyword(s):  
Near Infrared ◽  
Numerical Models ◽  
Spectral Characteristics ◽  
Line Emission ◽  
Nir Spectroscopy ◽  
Free Fall ◽  
Balmer Line ◽  
Line Profiles ◽  
Fall Velocity ◽  
T Tauri

Context. The star S CrA is a tight visual binary consisting of two classical T Tauri stars. Both components are outstanding regarding their spectral characteristics and brightness variations. Aims. Our aim is to explore the extraordinary spectral features seen in these stars, derive stellar parameters, define spectral signatures of accreting gas and winds, estimate the inclinations of the disks, and to match numerical models with observed properties. Methods. High-resolution spectra were collected of each component over several nights at the European Southern Observatory (ESO) combined with photometric observations covering several years in UBVRI with the SMARTS telescope. The models developed include magnetospheric accretion and a disk wind. Results. Both stars undergo large variation in brightness, ≥2 mag in V band. The variations are caused mainly by variable foreground extinction from small-size dust grains, which may be carried along with the accreting gas. The photospheric absorption lines are washed out by superimposed continuous and line emission, and this veiling becomes occasionally exceptionally high. Nevertheless, we extracted the stellar spectra and found that both stars are very similar with regard to stellar parameters (Teff, log g, v sin i, mass, radius, luminosity). The rotational periods, inferred from velocity shifts in lines originating in surface areas off-set from the pole, are also similar. Combined with the v sin i:s related inclinations were obtained, which agree well with those derived from our model simulations of Balmer line profiles: ~65° for both stars. At this orientation the trajectories of infalling gas just above the stellar surfaces are parallel to the line-of-sight, and accordingly we observe extended red-shifted absorption components extending to +380 km s−1, the estimated free-fall velocity at the surface. Rates of accretion and mass loss were obtained from the models. Conclusions. The two stars are remarkably similar, and S CrA can be regarded as a T Tauri twin. The components differ, however, in terms of degree of veiling and emission line profiles. We have found a good match between observed signatures of accreting gas, wind features, and rotational velocities with those resulting from our modelling for inclinations of ~65°. These inclinations differ from those derived from interferometric near-infrared (NIR) spectroscopy, and possible causes for this puzzling discrepancy are discussed.

Monitoring the performance of a broad-based calibration for measuring the nutritive value of two independent populations of pasture using near infrared reflectance (NIR) spectroscopy

1991 ◽  
Vol 31 (2) ◽  
pp. 205 ◽  
Author(s):  
KF Smith ◽  
PC Flinn
Keyword(s):  
Nutritive Value ◽  
Near Infrared ◽  
Linear Regression Analysis ◽  
Spectral Characteristics ◽  
Nir Spectroscopy ◽  
Cost Effective ◽  
Multiple Linear Regression Analysis ◽  
Infrared Reflectance ◽  
Near Infrared Reflectance

Near infrared reflectance (NIR) spectroscopy is a rapid and cost-effective method for the measurement of organic constituents of agricultural products. NIR is widely used to measure feed quality around the world and is gaining acceptance in Australia. This study describes the development of an NIR calibration to measure crude protein (CP), predicted in vivo dry matter digestibility (IVDMD) and neutral detergent fibre (NDF) in temperate pasture species grown in south-western Victoria. A subset of 116 samples was selected on the basis of spectral characteristics from 461 pasture samples grown in 1987-89. Several grass and legume species were present in the population. Stepwise multiple linear regression analysis was used on the 116 samples to develop calibration equations with standard errors of 0.8,2.3 and 2.2% for CP, NDF and IVDMD, respectively. When these equations were tested on 2 independent pasture populations, a significant bias existed between NIR and reference values for 2 constituents in each population, indicating that the calibration samples did not adequately represent the new populations for these constituents. The results also showed that the H statistic alone was inadequate as an indicator of equation performance. It was confirmed that it was possible to develop a broad-based calibration to measure accurately the nutritive value of closed populations of temperate pasture species. For the resulting equations to be used for analysis of other populations, however, they must be monitored by comparing reference and NIR analyses on a small number of samples to check for the presence of bias or a significant increase in unexplained error.

Winds from T Tauri stars. II - Balmer line profiles for inner disk winds

1992 ◽  
Vol 386 ◽  
pp. 229 ◽  
Author(s):  
Nuria Calvet ◽  
Lee Hartmann ◽  
Robert Hewett
Keyword(s):  
T Tauri Stars ◽  
Balmer Line ◽  
Line Profiles ◽  
T Tauri

Magnetic Accretion Funnels in Young Stellar Objects: Thermal Structure and Emission Signatures

1997 ◽  
Vol 163 ◽  
pp. 760-760
Author(s):  
Steven C. Martin ◽  
Arieh Königl
Keyword(s):  
Magnetic Field ◽  
Near Infrared ◽  
Thermal Structure ◽  
Line Emission ◽  
Young Stellar Objects ◽  
Rate Equations ◽  
Gas Temperature ◽  
Ionization State ◽  
Object A ◽  
T Tauri

AbstractA self-consistent procedure is outlined for determining the thermal structure of gas inflowing along magnetic field lines of a young stellar object. A young pre-main-sequence star (e.g., a classical T Tauri star) is assumed to possess a dipole magnetic field that disrupts a geometrically thin accretion disk and channels the incoming gas toward the stellar surface, leading to the formation of a pair of accretion funnels that terminate in shocks at high stellar latitudes. The heat equation is solved together with the rate equations for hydrogen, and the main physical processes that heat and cool the gas are identified. In particular, in the case of T Tauri stars, it is found that adiabatic compression is the principal heat source and that the Ca II and Mg II ions act as a powerful thermostat that regulates the gas temperature. The ionization state of the gas in the radiation field of the stellar photosphere and of the accretion shocks is found in this case to be controlled by Balmer continuum photons. The implications of these calculations to the observational signatures of accreting YSOs (e.g., their near-infrared hydrogen and CO overtone line emission) are discussed.

scholarly journals Interacting Nuclei in Distant Galaxies

1990 ◽  
Vol 124 ◽  
pp. 251-253
Author(s):  
Wei Zheng ◽  
Steven A. Grandi
Keyword(s):  
Emission Line ◽  
Active Galactic Nuclei ◽  
Accretion Disk ◽  
Outer Part ◽  
Line Emission ◽  
Galactic Nuclei ◽  
Balmer Line ◽  
Line Profiles ◽  
Double Peaks ◽  
Distant Galaxies

The interaction of galaxies not only occurs in galactic scales, but also may be linked to the binary cores in active galactic galaxies. The presence of a binary in the center of galaxies was suggested by Begelman, Blandford and Rees (1980). Gaskell (1983) suggests that supermassive binaries may account for the observed structure of emission line profiles such as double peaks displaced by a significant velocity difference. Collin-Souffrin, et al. (1986) argue that line emission may be formed in the outer part of an accretion disk. The resultant profile, as expected from rotational motion, would be very broad and often possess a double-horn shape. However, the emission line profiles in most active galactic nuclei do not share such a resemblance, and there are only two reported cases, 3C390.3 (Pérez et al. 1987) and Arp102B (Chen, Halpern and Filippenko 1989), in which the broad Balmer line profile may be of such a shape. Therefore, the assumption for accretion disk is to be verified with care.

scholarly journals Agronomic characteristics of annual Trifolium legumes and nutritive values as predicted by near-infrared reflectance (NIR) spectroscopy

2011 ◽  
Vol 62 (12) ◽  
pp. 1078 ◽  
Author(s):  
X. Li ◽  
R. L. Ison ◽  
R. C. Kellaway ◽  
C. Stimson ◽  
G. Annison ◽  
...  
Keyword(s):  
Organic Matter ◽  
Near Infrared ◽  
Spectral Characteristics ◽  
Nir Spectroscopy ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Infrared Reflectance ◽  
Near Infrared Reflectance ◽  
Stem Leaf

A range of annual legume genotypes comprising one line of Trifolium subterraneum, four lines of T. michelianum, 11 of T. resupinatum var. resupinatum, and one line of T. resupinatum var. majus were grown in glasshouses under temperature regimes of 10−15°C and 16−21°C. Dry matter (DM) weights of stem, leaf, and flower tissues were measured when plants had six nodes, at first flower appearance, and at senescence. All samples were scanned by near-infrared reflectance spectroscopy (NIRS). One-third of the samples, covering the range of spectral characteristics, were analysed for in vitro digestible organic matter (DOMD), organic matter, crude protein (CP), neutral detergent fibre (NDF), lignin, cellulose, and the hemicellulosic polysaccharide monomers arabinose, xylose, mannose, galactose, and rhamnose. These data were used to develop calibration equations from which the composition of the remaining samples was predicted by NIRS. The higher temperature resulted in plants reaching respective phenological stages earlier, but did not affect either DM yields of total plant, stem, leaf, and petiole tissues or the proportions of each fraction. In vitro DOMD and arabinose and galactose levels decreased, while lignin, cellulose, NDF, xylose, mannose, and rhamnose levels increased with advancing maturity. In vitro DOMD was positively associated with contents of CP, arabinose, galactose, and the arabinose/xylose ratio and was negatively associated with contents of lignin, cellulose, NDF, xylose, mannose, and rhamnose. Lignin contents were highly correlated with levels of both xylose and mannose. Stems were more digestible than leaves in subterranean clover and T. resupinatum var. majus. The study also demonstrated that NIRS can be used routinely as a quick, inexpensive, and reliable laboratory technique to predict feed components of annual Trifolium legumes.

scholarly journals Do Herbig Ae/Be Stars Have Disks?

1997 ◽  
Vol 163 ◽  
pp. 525-530 ◽  
Author(s):  
T.P. Ray ◽  
M. Corcoran
Keyword(s):  
Equivalent Width ◽  
Near Infrared ◽  
Mass Loss Rate ◽  
Line Emission ◽  
Circumstellar Disks ◽  
T Tauri Stars ◽  
Be Stars ◽  
Infrared Excess ◽  
T Tauri ◽  
Outflow Rate

AbstractThe Herbig Ae/Be stars are optically visible pre-main sequence stars of intermediate mass (M* ≈ 3−8M⊙) and are thought to be the higher mass analogues of the T Tauri stars. While there is no doubt that classical T Tauri stars, i.e. those with EW(Hα) ≳ 10 Å, are surrounded by disks, it remains controversial as to whether this is the case with the equivalent Herbig Ae/Be stars. It has even been questioned whether the powerful winds that are ejected by Herbig Ae/Be stars are driven by accretion. To address these problems we have examined a large sample of these stars with the idea of using their forbidden line emission as an indirect diagnostic for the presence of disks. Striking similarities with the classical T Tauri stars are found. For example we have discovered evidence not only for a strong correlation between near-infrared colours and the equivalent width of the forbidden line emission but also that the forbidden line emission normally arises in a blueshifted outflow component. It has already been shown in the case of the classical T Tauri stars that the correlation of near-infrared colour with forbidden line equivalent width is due to a link between the accretion rate and the outflow rate. The virtually identical relationship seen in the case of the Herbig Ae/Be stars must then also have a similar origin. Our finding that the forbidden line emission in Herbig Ae/Be stars is normally blueshifted shows not only that it arises in an outflow but, as in the classical T Tauri stars, such an asymmetry in the velocity centre of the line must be caused by the obscuring effects of a disk. We find that the correlation seen in the classical T Tauri stars between the mass-loss rate and infrared excess can be extended, when we include the Herbig Ae/Be stars, to cover almost 5 orders of magnitude in stellar luminosity. Our observations therefore broaden the findings of earlier observers for low mass young stars and indicate the presence of circumstellar disks around the majority of Herbig Ae/Be stars with forbidden line emission. A corollary of our results is that the same outflow mechanism must operate in both the classical T Tauri stars and the Herbig Ae/Be stars with forbidden line emission.

scholarly journals Nondestructive Determination of Diastase Activity of Honey Based on Visible and Near-Infrared Spectroscopy

Molecules ◽  
2019 ◽  
Vol 24 (7) ◽  
pp. 1244
Author(s):  
Zhenxiong Huang ◽  
Lang Liu ◽  
Guojian Li ◽  
Hong Li ◽  
Dapeng Ye ◽  
...  
Keyword(s):  
Least Squares ◽  
High Temperatures ◽  
Near Infrared ◽  
Spectral Characteristics ◽  
Nir Spectroscopy ◽  
Kinetic Mechanism ◽  
National Standard ◽  
Support Vector ◽  
Heating Process

The activities of enzymes are the basis of evaluating the quality of honey. Beekeepers usually use concentrators to process natural honey into concentrated honey by concentrating it under high temperatures. Active enzymes are very sensitive to high temperatures and will lose their activity when they exceed a certain temperature. The objective of this work is to study the kinetic mechanism of the temperature effect on diastase activity and to develop a nondestructive approach for quick determination of the diastase activity of honey through a heating process based on visible and near-infrared (Vis/NIR) spectroscopy. A total of 110 samples, including three species of botanical origin, were used for this study. To explore the kinetic mechanism of diastase activity under high temperatures, the honey of three kinds of botanical origins were processed with thermal treatment to obtain a variety of diastase activity. Diastase activity represented with diastase number (DN) was measured according to the national standard method. The results showed that the diastase activity decreased with the increase of temperature and heating time, and the sensitivity of acacia and longan to temperature was higher than linen. The optimum temperature for production and processing is 60 °C. Unsupervised clustering analysis was adopted to detect spectral characteristics of these honeys, indicating that different botanical origins of honeys can be distinguished in principal component spaces. Partial least squares (PLS) and least squares-support vector machine (LS-SVM) algorithms were applied to develop quantitative relationships between Vis/NIR spectroscopy and diastase activity. The best result was obtained through Gaussian filter smoothing-standard normal variate (GF-SNV) pretreatment and the LS-SVM model, known as GF-SNV-LS-SVM, with a determination coefficient (R2) of prediction of 0.8872, and root mean square error (RMSE) of prediction of 0.2129. The overall results of this paper showed that the diastase activity of honey can be determined quickly and non-destructively with Vis/NIR spectral methods, which can be used to detect DN in the process of honey production and processing, and to maximize the nutrient content of honey.

scholarly journals Quantitative estimation of soil salinity by means of different modeling methods and visible-near infrared (VIS–NIR) spectroscopy, Ebinur Lake Wetland, Northwest China

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e4703 ◽  
Author(s):  
Jingzhe Wang ◽  
Jianli Ding ◽  
Aerzuna Abulimiti ◽  
Lianghong Cai
Keyword(s):  
Fractional Derivative ◽  
Soil Salinity ◽  
Spectral Reflectance ◽  
Near Infrared ◽  
Quantitative Estimation ◽  
Spectral Characteristics ◽  
Nir Spectroscopy ◽  
Soil Parameters ◽  
Modeling Methods ◽  
Ebinur Lake

Soil salinization is one of the most common forms of land degradation. The detection and assessment of soil salinity is critical for the prevention of environmental deterioration especially in arid and semi-arid areas. This study introduced the fractional derivative in the pretreatment of visible and near infrared (VIS–NIR) spectroscopy. The soil samples (n = 400) collected from the Ebinur Lake Wetland, Xinjiang Uyghur Autonomous Region (XUAR), China, were used as the dataset. After measuring the spectral reflectance and salinity in the laboratory, the raw spectral reflectance was preprocessed by means of the absorbance and the fractional derivative order in the range of 0.0–2.0 order with an interval of 0.1. Two different modeling methods, namely, partial least squares regression (PLSR) and random forest (RF) with preprocessed reflectance were used for quantifying soil salinity. The results showed that more spectral characteristics were refined for the spectrum reflectance treated via fractional derivative. The validation accuracies showed that RF models performed better than those of PLSR. The most effective model was established based on RF with the 1.5 order derivative of absorbance with the optimal values of R2 (0.93), RMSE (4.57 dS m−1), and RPD (2.78 ≥ 2.50). The developed RF model was stable and accurate in the application of spectral reflectance for determining the soil salinity of the Ebinur Lake wetland. The pretreatment of fractional derivative could be useful for monitoring multiple soil parameters with higher accuracy, which could effectively help to analyze the soil salinity.

scholarly journals Near-infrared spectroscopy of SN 2009ip's 2012 brightening reveals a dusty pre-supernova environment

2013 ◽  
Vol 434 (4) ◽  
pp. 2721-2726 ◽  
Author(s):  
Nathan Smith ◽  
Jon C. Mauerhan ◽  
Mansi M. Kasliwal ◽  
Adam J. Burgasser
Keyword(s):  
Near Infrared ◽  
Spectral Characteristics ◽  
Emission Lines ◽  
Circumstellar Dust ◽  
Line Profiles ◽  
Blue Colour ◽  
Near Ir ◽  
Dust Temperature ◽  
Expansion Speed ◽  
Peak Luminosity

Abstract We present low-resolution near-infrared (IR) 0.8–2.5 μm spectra of Supernova (SN) 2009ip, taken immediately before, during and just after its rapid brightening in late September/October 2012. The first epoch shows the same general spectral characteristics as the later epochs (smooth continuum, narrow H and He i emission lines), but the IR continuum shape is substantially redder than the later epochs. The epoch 1 continuum can be approximated by reddening the peak-luminosity (epoch 3) spectrum by E(B − V) = 1.0 mag, but the blue colour seen in visual-wavelength spectra at the same time indicates that strong wavelength-dependent extinction by circumstellar dust is not the correct explanation. Instead, we favour the hypothesis that the redder colour before the brightening arises from excess emission from hot ∼2000 K circumstellar dust. The minimum radius ( ≳ 120 au) deduced from the dust temperature and observed luminosity of the transient, combined with the observed expansion speed in the precursor outbursts of SN 2009ip, is consistent with an ejection at least 1.1 yr earlier. The mass of hot dust indicated by the IR excess is ∼4 × 10−7 M⊙, although this is only a lower limit since the near-IR data do not constrain the mass of cooler dust. Thus, the observed pre-SN outbursts of this object were able to efficiently form dust into which the SN ejecta and radiation now propagate. This is consistent with the notion that the same pre-SN eruptions that generally give rise to SNe IIn also give rise to the dust needed for their commonly observed IR echoes. We also discuss some aspects of the IR line profiles, including He i λ10 830.

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