scholarly journals The Composition of Warm Giants in M 71 and M 5

1988 ◽  
Vol 126 ◽  
pp. 497-498
Author(s):  
Catherine A. Pilachowski ◽  
Christopher Sneden
Keyword(s):  
High Resolution ◽  
Globular Cluster ◽  
Globular Clusters ◽  
High Dispersion ◽  
High Signal ◽  
Signal To Noise

In 1979 a disturbing controversy arose in the field of globular cluster research when Cohen (1980) and Pilachowski, Canterna, and Wallerstein (1980) announced the results of the first high dispersion studies of the composition of giants in the globular clusters M 71 and 47 Tucanae. In contrast to earlier studies, which found metallicities of typically −0.3 and −0.5 dex, these investigators obtained values of −1.3 and −1.1. Since then, many have attempted to redetermine the abundances of M 71 and 47 Tuc to explain the discrepant results. These efforts have all suffered from the absence of high signal-to-noise, high resolution spectra of stars with temperatures above 4300 K.

scholarly journals The Distribution of Iron over the Surface of 21 Com

2021 ◽  
Vol 5 (12) ◽  
pp. 284
Author(s):  
Richard Monier
Keyword(s):  
High Resolution ◽  
High Dispersion ◽  
High Signal ◽  
Rotational Period ◽  
Signal To Noise ◽  
Maximum Flux ◽  
Iron Abundance

Abstract Comparison of high dispersion LWP spectra obtained in 24 hr of monitoring of 21 Com with IUE in April 1991 reveals variations of low excitation Fe ii lines at phase 0.65 of the rotational period (FUV minimum flux) compared to phase 0.18 (FUV maximum flux). All 10 Fe ii lines of UV Multiplets 1 and 62 are consistently stronger at phase 0.65, which shows that the FUV flux minimum can be partially explained to an increase of the disk averaged iron abundance. In contrast, comparison of optical high resolution high signal-to-noise ELODIE spectra of 21 Com taken in 2004 April and separated by about half of the 2 days rotational period, reveals no significant variations of the Fe ii and Fe i lines. The lines monitored in the mid UV are strong low-lying transitions which are probably more sensitive to small abundance gradients over the surface of 21 Com.

Accurate Abundances in Some Giant Stars of the Globular Cluster ω Centauri

1988 ◽  
Vol 132 ◽  
pp. 537-540
Author(s):  
F. Spite ◽  
M. Spite ◽  
P. François
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Dwarf Galaxies ◽  
Magellanic Clouds ◽  
High Signal ◽  
Signal To Noise ◽  
Giant Stars ◽  
Great Complexity ◽  
Made In

The globular cluster ω Cen is known as a very peculiar cluster : some stars show anomalous abundances. Accurate abundance determinations of various elements have been made in six giants of ω Cen, using spectra with high signal to noise ratios. The results suggest some constraints on the origin of the anomalies, but also show the great complexity of the problem, which requires more observations for approaching a solution. A solution would help to understand the evolution of other objects : globular clusters in the Magellanic Clouds, and dwarf galaxies.

Recent Advances in High Dispersion Spectroscopy of Globular Cluster Stars

1988 ◽  
Vol 132 ◽  
pp. 525-530
Author(s):  
Raffaele G. Gratton
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
High Dispersion ◽  
Photographic Material ◽  
Recent Advances ◽  
Metal Abundances ◽  
Ccd Detectors ◽  
Major Progress

The use CCD detectors has allowed a major progress in abundance derivations for globular cluster stars in the last years. Abundances deduced from high dispersion spectra now correlates well with other abundance indicators. I discuss some problems concerning the derivation of accurate metal abundances for globular clusters using high dispersion spectra from both the old photographic and the most recent CCD data. The discrepant low abundances found by Cohen (1980), from photographic material for M71 giants, are found to be due to the use of too high microturbulences.

scholarly journals Airglow Derived Measurements of Q-Branch Transition Probabilities for Several Hydroxyl Meinel Bands

Atmosphere ◽  
2019 ◽  
Vol 10 (10) ◽  
pp. 637 ◽  
Author(s):  
Christoph Franzen ◽  
Patrick Joseph Espy ◽  
Niklas Hofmann ◽  
Robert Edward Hibbins ◽  
Anlaug Amanda Djupvik
Keyword(s):  
High Resolution ◽  
Spontaneous Emission ◽  
Transition Probabilities ◽  
High Signal ◽  
Hitran Database ◽  
Signal To Noise ◽  
Optical Telescope ◽  
Spectroscopic Observations ◽  
Emission Transition ◽  
Airglow Emissions

Spectroscopic measurements of the hydroxyl (OH) airglow emissions are often used to infer neutral temperatures near the mesopause. Correct Einstein coefficients for the various transitions in the OH airglow are needed to calculate accurate temperatures. However, studies from some studys showed experimentally and theoretically that the most commonly used Einstein spontaneous emission transition probabilities for the Q-branch of the OH Meinel (6,2) transition are overestimated. Extending their work to several Δv = 2 and 3 transitions from v′ = 3 to 9, we have determined Einstein coefficients for the first four Q-branch rotational lines. These have been derived from high resolution, high signal to noise spectroscopic observations of the OH airglow in the night sky from the Nordic Optical Telescope. The Q-branch Einstein coefficients calculated from these spectra show that values currently tabulated in the HITRAN database overestimate many of the Q-branch transition probabilities. The implications for atmospheric temperatures derived from OH Q-branch measurements are discussed.

A Study of the Orbital and Intrinsic Variability of the Double-Lined Spectroscopic Binary β Centauri

2002 ◽  
Vol 185 ◽  
pp. 86-87
Author(s):  
M. Ausseloos ◽  
C. Aerts ◽  
K. Uytterhoeven
Keyword(s):  
High Resolution ◽  
Orbital Motion ◽  
High Signal ◽  
Mass Ratio ◽  
Eccentric Orbit ◽  
Intrinsic Variability ◽  
Signal To Noise ◽  
Orbital Parameters ◽  
Spectroscopic Binary ◽  
First Time

AbstractWe introduce our observational study of the orbital motion of β Cen. Using 463 high signal-to-noise, high-resolution spectra obtained over a timespan of 12 years it is shown that the radial velocity of β Cen varies with an orbital period of 357.0 days. We derive for the first time the orbital parameters of β Cen and find a very eccentric orbit (e = 0.81) and similar component masses with a mass ratio M1/M2 = 1.02. Both the primary and the secondary exhibit periodic line-profile variations.

scholarly journals The well correlated diffuse interstellar bands at λλ 6196, 6614 Å and their possible companions

2020 ◽  
Vol 496 (2) ◽  
pp. 2231-2240
Author(s):  
A Bondar
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
High Resolution ◽  
Aromatic Hydrocarbons ◽  
Correlation Coefficients ◽  
High Signal ◽  
Signal To Noise ◽  
B Stars ◽  
Diffuse Interstellar Bands ◽  
Polycyclic Aromatic ◽  
First Time

ABSTRACT Considered here is the interrelation between five diffuse interstellar bands (DIBs), λλ 5545, 6113, 6196, 6445 and 6614 Å. Two DIBs (λλ 6196 and 6614 Å) are already known as being well correlated with each other; their relation with three other weaker bands is investigated for the first time. To accomplish this task, high-resolution spectra (λ/δλ ≈100 000) with high signal-to-noise ratios (S/N) of 54 hot O–B stars with reddening 0.12–1.45 mag were used. Analysis of measured equivalent widths has allowed us to establish linear dependences and evaluate linear correlation coefficients as high as 0.968–0.988 between the intensities of these five DIBs. Such a degree of correlation may indicate their common origin. Several spacings in wavenumbers found between these DIBs correspond to the energies of vibrational transitions in some polycyclic aromatic hydrocarbons resulting in IR emissions at λλ 16.4, 11.3, 7.7, 6.2 and 3.3 μm.

scholarly journals 53 Piscium, an SPB Star with Activity

2002 ◽  
Vol 185 ◽  
pp. 236-237
Author(s):  
J.-M. Le Contel ◽  
P. Mathias ◽  
E. Chapellier ◽  
J.-C. Valtier
Keyword(s):  
High Resolution ◽  
False Alarm ◽  
High Frequency ◽  
Signal To Noise Ratio ◽  
High Signal ◽  
Correlation Technique ◽  
Signal To Noise ◽  
Spectroscopic Observations ◽  
Auto Correlation ◽  
Frequency Variations

The star 53 Psc (HD 3379, B2.5IV) has been observed as variable by several authors (Sareyan et al., 1979) with frequencies around 10 c d–1 and has been classified as a β Cephei star. Conversely, other authors (e.g. Percy, 1971) found it to be constant.New high resolution, high signal-to-noise ratio, Spectroscopic observations have been performed at the Observatoire de Haute-Provence in 1996 over 11 nights. The spectral domain covers around 200 Å and is centered on Hδ. Radial velocities were deduced from an auto-correlation technique with a scatter around 0.4kms−1.No high frequency variations are observed. Three frequencies have been detected with a false alarm detection above the 1 % level. A fourth one may be present but its amplitude is below this 1 % level. Results are displayed in Table 1.

Sign in / Sign up

Export Citation Format

Share Document