Static phase aberrations in near-IR interferometry and GRAVITY's determination of the galactic center distanceStatic phase aberrations in near-IR interferometry and GRAVITY's determination of the galactic center distance

2020 ◽  
Author(s):  
Julia Stadler ◽  
Guy Perin ◽  
Wolfgang Brandner ◽  
Christian Straubmeier ◽  
Karine Rousselet-Perraut ◽  
...  
Keyword(s):  
Galactic Center ◽  
Near Ir ◽  
Static Phase ◽  
Phase Aberrations ◽  
Center Distance

scholarly journals Milky Way Rotation Models from Neutral Hydrogen and Molecular Clouds: Galactic Constants, Common Details and Differences

2000 ◽  
Vol 174 ◽  
pp. 403-407
Author(s):  
Igor’ I. Nikiforov
Keyword(s):  
Milky Way ◽  
Galactic Center ◽  
Kinematic Model ◽  
Neutral Hydrogen ◽  
Galactic Rotation ◽  
Kinematic Data ◽  
Galactic Rotation Curve ◽  
The Common ◽  
Center Distance

Kinematic data from neutral hydrogen observations provide information to solve the interdependent problems of the determination of the main Galactic constants (the Solar-Galactic center distance R0, the Oort constant A and others) and the Galactic rotation curve (Nikiforov & Petrovskaya 1994, hereafter NP94, and references therein). However, in the standard method for finding R0 by comparing the rotations of HI clouds and some other objects (typically HII regions/CO clouds), the kinematic model, constructed typically solely from HI data, is considered to be the same for both galactic subsystems (e.g. Merrifield 1992). In practice a discrepancy between their rotation curves can produce strongly erroneous results (Merrifield 1992, NP94). Establishing the common rotation law from HI plus HII/CO data in NP94 is only a part of attacking the problem.

Near-IR Spectroscopic Determination of NaCl in Aqueous Solution

1992 ◽  
Vol 46 (12) ◽  
pp. 1809-1815 ◽  
Author(s):  
Jie Lin ◽  
Chris W. Brown
Keyword(s):  
Aqueous Solution ◽  
Temperature Effects ◽  
Continuous Monitoring ◽  
Principal Component Regression ◽  
Principal Component ◽  
Standard Errors ◽  
Near Ir ◽  
Linear And Nonlinear ◽  
Ir Spectroscopic

The concentrations of NaCl in aqueous solutions have been determined with the use of near-IR spectra between 1100 and 1900 nm. Models expressing the concentration of NaCl are developed with linear and nonlinear regression with the use of the absorbances at selected wavelengths and with principal component regression (PCR) using entire spectra. Temperature perturbations on water bands interfere with the measurement of NaCl but can be removed by linear or nonlinear regressions using the absorbances at the wavelengths where the temperature effects are zero, or they can be accounted for by PCR. Standard errors of 5 mM and a detection limit of IS mM are obtained for NaCl. This technique can be applied for quantitative analysis of NaCl in the laboratory or can be readily adapted for continuous monitoring in process control.

AN EASY APPROACH FOR ESTIMATING ABSORPTION LOSS IN ORGANIC THIN SOLID FILMS

1999 ◽  
Vol 08 (04) ◽  
pp. 519-525
Author(s):  
SHEN YUQUAN ◽  
LI ZHAO ◽  
ZHAO YUXIA ◽  
ZHAI JIANFENG ◽  
ZHOU JIAYUN ◽  
...  
Keyword(s):  
Spectroscopic Method ◽  
Optical Loss ◽  
Polymeric Films ◽  
Absorption Loss ◽  
Optical Losses ◽  
Thin Solid Films ◽  
Solid Films ◽  
Near Ir ◽  
Ir Spectroscopic

An UV-VIS-Near-IR spectroscopic method for determination of optical loss in organic/polymeric films has been suggested. The optical losses of two polyimide polymers with push-pull azobenzene chromophore attached were examined by this method and the data were calibrated by conventional optical method.

scholarly journals Proper Motions of H2O Masers in W49(N) and the Distance to the Galactic Center

1989 ◽  
Vol 136 ◽  
pp. 47-49 ◽  
Author(s):  
C. R. Gwinn ◽  
J. M. Moran ◽  
M. J. Reid ◽  
M. H. Schneps ◽  
R. Genzel ◽  
...  
Keyword(s):  
Galactic Center ◽  
Proper Motions ◽  
Source Data

A distance of R0 = 7.6 ± 1.6 kpc for the galactic center is given by comparison of expansion parallax of a cluster of H2O masers in W49(N) with the kinematic distance of that source. Data from additional epochs, now being calibrated, should further improve the accuracy of our determination of R0.

scholarly journals Determination of the C/M5+ Ratio in the Galactic Disk

1995 ◽  
Vol 148 ◽  
pp. 276-279
Author(s):  
Francisco J. Fuenmayor
Keyword(s):  
Near Infrared ◽  
Galactic Center ◽  
Galactic Disk ◽  
Mean Value ◽  
Galactocentric Distance ◽  
The Galaxy ◽  
Metal Abundance ◽  
Objective Prism ◽  
M Stars

AbstractA determination of the C/M5+ ratio, as a function of the galactocentric distance, in the galactic disk is presented. These results are based upon previous determinations of the space density for cool carbon stars and for late giant M stars in the Milky Way. Most of these results were obtained from objective-prism surveys in the near infrared using mainly Schmidt-type telescopes. The ratio C/M5+ appears to increase from 0.05 to 0.25 in the galactic disk, from the galactic center outwards. A mean value of 0.15 of this ratio for the Galaxy is suggested. Correlations between the C/M5+ ratio and currently known metal abundance gradients in the galactic disk are discussed.

Universal Approach for Determination of Physical and Chemical Properties of Water by Near-IR Spectroscopy

1993 ◽  
Vol 47 (10) ◽  
pp. 1720-1727 ◽  
Author(s):  
Jie Lin ◽  
Chris W. Brown
Keyword(s):  
Ir Spectroscopy ◽  
Chemical Properties ◽  
Fiber Optic Sensor ◽  
Universal Method ◽  
Physical And Chemical Properties ◽  
Near Ir ◽  
Universal Approach ◽  
Physical And Chemical ◽  
And Chemical Properties

Near-IR spectroscopy has been investigated as a universal approach for determination of physical and chemical properties of water and their functions of temperature. Principal component regression and multilinear regression models were used to correlate the spectra with the properties of water at temperatures between 5 and 65°C. Fifteen properties of water were investigated including density, refractive index, dielectric constant, relative viscosity, surface tension, vapor pressure, sound velocity, isothermal compressibility, thermal expansivity, thermal capacity, thermal conductivity, enthalpy, free energy, entropy, and ionization constant. Very good correlations were found between the near-IR predicted values of all the properties and those obtained by the traditional methods. This investigation demonstrates that these fifteen properties of water can be simultaneously determined simply by measuring a set of near-IR spectra of water, and, thus, near-IR spectroscopy can be used as a universal method for the determinations of physical and chemical properties of water. Remote sensing of the properties can be performed with the use of a fiber-optic sensor.

scholarly journals New kinematic distance scale for the Galactic planetary nebulae

2011 ◽  
Vol 7 (S283) ◽  
pp. 406-407
Author(s):  
Alexander F. Kholtygin ◽  
Igor' I. Nikiforov ◽  
Vitalii V. Akimkin
Keyword(s):  
Galactic Center ◽  
Planetary Nebulae ◽  
Distance Scale ◽  
Statistical Distance ◽  
Center Distance ◽  
Good Agreement

AbstractWe analyze the kinematics of disk planetary nebulae (PNe) to derive the formal Galactic center distance, R0, for three catalogues of PNe distances. Then we correct the catalogues' distance scales renormalizing the PNe distances by the ratios of formal R0 values to a best modern value of R0 =7.9 kpc. The created new catalogue of disk's PNe distances was found to be in a good agreement with distances by Stanghellini et al. (2008). Our catalogue of PNe distances was used to recalibrate the statistical distance scale for all Galactic PNe.

Characterisation of Diamond-like Carbon by Raman Spectroscopy and Optical Constants

1996 ◽  
Vol 423 ◽  
Author(s):  
C. Mölßner ◽  
P. Grant ◽  
H. Tran ◽  
G. Clarke ◽  
D. J. Lockwood ◽  
...  
Keyword(s):  
Raman Spectra ◽  
Diamond Coatings ◽  
Protective Layers ◽  
Near Ir ◽  
Field Emission Displays ◽  
Chemical Inertness ◽  
Krf Excimer Laser ◽  
Substrate Temperatures ◽  
Hardness Values

AbstractCrystalline diamond coatings and, increasingly, diamond like amorphous carbon (DLC) films are used for tribological and protective layers for their hardness and chemical inertness. They are also under investigation for their electron emitting properties, with possible applications in field emission displays. DLC films were deposited by laser ablation using a KrF excimer laser and fluences between 0.5 and 2 J/cm2. FTIR measurements did not show the presence of hydrogen in the films. Raman spectra allowed for the determination of the nature of the graphitic and diamond bonds (sp2 and sp3) as well as information about the disorder and short range order in the films. For a better determination of the sp3-content, which is often hidden in the Raman spectra, a correlation with optical properties in the near IR to near UV region was established. These values depended strongly on the substrate temperature and the laser fluence. DLC formation could be demonstrated even at substrate temperatures close to room temperature. Vickers hardness values and first measurements on the electron emissivity of the films can be correlated to the diamond character and the preparation method of the films.

scholarly journals Red Clump Stars – Further Improved Distance Indicator

2002 ◽  
Vol 12 ◽  
pp. 688 ◽  
Author(s):  
P.M. Garnavich ◽  
K. Stanek
Keyword(s):  
Galactic Center ◽  
Hubble Constant ◽  
Large Magellanic Cloud ◽  
Solar Neighborhood ◽  
Horizontal Branch Stars ◽  
Standard Value ◽  
Distance Indicator ◽  
Red Clump ◽  
Distance Indicators

AbstractThe ideal distance indicator would be a standard candle abundant enough to provide many examples within reach of parallax measurements and sufficiently bright to be seen out to Local Group galaxies. The red clump stars closely match this description. These are the metal rich equivalent of the better known horizontal branch stars, and their brightness dispersion is only 0.2 mag (one sigma) in the Solar neighborhood. Using Hipparcos to calibrate a large, local sample, the red clump method has been used to measure accurate distances to the Galactic center (Paczyński & Stanek 1998), M31 (Stanek & Garnavich 1998), LMC (Udalski et al. 1998; Stanek et al. 1998; Udalski 1999) and some clusters in our Galaxy (e.g. 47Tuc: Kaluzny et al. 1998). As with all the distance indicators, the main worry lies in the possible systematics of the method, in particular, the brightness dependence on the stellar metallicity and age. These dependences have come under close scrutiny and, indeed, the population effects on the red clump brightness appear small and calibratable. Perhaps the most controversial result from the red clump method is the estimation of a “short” distance to the Large Magellanic Cloud (Udalski et al. 1998; Stanek, Zaritsky & Harris 1998; Udalski 2000). This distance to the LMC is shorter by 12% than the “standard” value, and has very important implications for the Cepheid distance scale and the determination of the Hubble constant.

Near-IR Reflectance Spectroscopy for the Determination of Motor Oil Contamination in Sandy Loam

1996 ◽  
Vol 50 (3) ◽  
pp. 334-338 ◽  
Author(s):  
Brian R. Stallard ◽  
Manuel J. Garcia ◽  
Sumanth Kaushik
Keyword(s):  
Organic Contaminants ◽  
Sandy Loam ◽  
Sampling Error ◽  
Reflectance Spectroscopy ◽  
Oil Contamination ◽  
Motor Oil ◽  
Near Ir ◽  
Ir Reflectance ◽  
The One

We have investigated the application of near-IR reflectance spectroscopy to the determination of motor oil contamination in sandy loam. Although the present work is concerned with a specific case of contamination, we discuss the possibility of applying the method to other organic contaminants and other types of soil. The spectral region considered was 1600–1900 nm, which contains the first overtone of the CH stretch. Using a commercial Fourier transform spectrometer together with cross-validated partial least-squares data analysis, the one-sigma precision for the determination of motor oil in sandy loam was 0.17 wt % (0.13 to 0.26 wt % at the 95% confidence level). The largest contribution to the precision of the determination was sampling error, or inhomogeneity in each sample. Given the precision limit imposed by the sampling error, we found that the performance of the spectrometer could be lowered without affecting the overall precision. In a modeling exercise, adequate performance was obtained with a spectrometer having only seven spectral channels with a spectral resolution of 10 nm and a spectral noise level of 10−3 absorbance units. A design for an inexpensive miniature instrument is presented.

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