scholarly journals A collection of model stellar spectra for spectral types B to early-M

2018 ◽  
Vol 618 ◽  
pp. A25 ◽  
Author(s):  
C. Allende Prieto ◽  
L. Koesterke ◽  
I. Hubeny ◽  
M. A. Bautista ◽  
P. S. Barklem ◽  
...  
Keyword(s):  
High Resolution ◽  
Interstellar Medium ◽  
Effective Temperature ◽  
Molecular Data ◽  
Chemical Compositions ◽  
Wavelength Interval ◽  
Atmospheric Parameters ◽  
Stellar Spectra ◽  
Synthetic Spectra ◽  
Wide Range

Context. Models of stellar spectra are necessary for interpreting light from individual stars, planets, integrated stellar populations, nebulae, and the interstellar medium. Aims. We provide a comprehensive and homogeneous collection of synthetic spectra for a wide range of atmospheric parameters and chemical compositions. Methods. We compile atomic and molecular data from the literature. We adopt the largest and most recent set of ATLAS9 model atmospheres, and use the radiative code ASSϵT. Results. The resulting collection of spectra is made publicly available at medium and high-resolution (R ≡ λ/δλ = 10 000, 100 000 and 300 000) spectral grids, which include variations in effective temperature between 3500 K and 30 000 K, surface gravity (0 ≤ log g ≤ 5), and metallicity (−5 ≤ [Fe/H] ≤ +0:5), spanning the wavelength interval 120–6500 nm. A second set of denser grids with additional dimensions, [α/Fe] and micro-turbulence, are also provided (covering 200–2500 nm). We compare models with observations for a few representative cases.

scholarly journals Detailed Analyses of Four Solar Analogs Analysed On High S/N CFH and ESO Spectra

1988 ◽  
Vol 132 ◽  
pp. 429-432
Author(s):  
C. Bentolila ◽  
G. Cayrel de Strobel
Keyword(s):  
High Resolution ◽  
Effective Temperature ◽  
The Sun ◽  
Atmospheric Parameters ◽  
Iron Abundance ◽  
Solar Type ◽  
Solar Analogs

Four solar type G stars claimed to be photometrically very similar to the Sun have been analyzed in detail on high resolution, high S/N spectra. Their atmospheric parameters : effective temperature, spectroscopic gravity, microturbulence and iron abundance, [Fe/H], have been determined.

scholarly journals Commission 29: Stellar Spectra

2005 ◽  
Vol 1 (T26A) ◽  
pp. 203-204
Author(s):  
Christopher Sneden ◽  
M. Parthasarathy ◽  
Fiorella Castelli ◽  
Katia Cunha ◽  
Philippe Eenens ◽  
...  
Keyword(s):  
Molecular Data ◽  
Variable Stars ◽  
Stellar Atmospheres ◽  
Chemical Compositions ◽  
Research Topics ◽  
Star Clusters And Associations ◽  
Stellar Spectra ◽  
Multiple Stars ◽  
Double And Multiple Stars ◽  
Surface Envelope

Participants in Commission 29 study various aspects of stellar spectra and the information that can be extracted from spectra. The list of fields of interest of the Organizing Committee members suggest some major current research topics in this area are stellar chemical compositions and surface/envelope phenomena. Some of the topics of this commission have overlap with other commissions, such as Commission 14 (Atomic and Molecular Data), 26 (Double and Multiple Stars), 27 (Variable Stars), 30 (Radial Velocities), 36 (Theory of Stellar Atmospheres), and 37 (Star Clusters and Associations). Many Commission 29 members are also members of these other commissions.

scholarly journals HIGH-RESOLUTION SPECTROSCOPY OF EXTREMELY METAL-POOR STARS FROM SDSS/SEGUE. I. ATMOSPHERIC PARAMETERS AND CHEMICAL COMPOSITIONS

2012 ◽  
Vol 145 (1) ◽  
pp. 13 ◽  
Author(s):  
Wako Aoki ◽  
Timothy C. Beers ◽  
Young Sun Lee ◽  
Satoshi Honda ◽  
Hiroko Ito ◽  
...  
Keyword(s):  
High Resolution ◽  
High Resolution Spectroscopy ◽  
Chemical Compositions ◽  
Atmospheric Parameters

LITHIUM IN THE STELLAR OPEN CLUSTER M67

2007 ◽  
Vol 16 (02n03) ◽  
pp. 391-396 ◽  
Author(s):  
B. L. CANTO MARTINS ◽  
J. D. DO NASCIMENTO ◽  
J. R. DE MEDEIROS ◽  
A. LÈBRE ◽  
O. RICHARD ◽  
...  
Keyword(s):  
High Resolution ◽  
Spectroscopic Analysis ◽  
Open Cluster ◽  
Atmospheric Parameters ◽  
Large Sample ◽  
Giant Stars ◽  
Evolved Stars ◽  
Synthetic Spectra

In this work we present atmospheric parameters and Li abundances, obtained from a detailed spectroscopic analysis, for a large sample of stars with different evolutionary stages (turn-off, subgiant and giant stars) in the open cluster M67. The observations were carried out with high resolution (R ~ 47,000) and high S/N using the UVES+FLAMES at VLT/UT2. From available photometry and computed synthetic spectra for the region around the lithium line at 6707.75 Å, we derive atmospheric parameters (T eff , log g, [ Fe/H ], v sin i) and Li abundances for each star, in order to better understand the level of mixing and convective dilution of evolved stars in M67.

scholarly journals Interpretation of Carbon Stars Spectra from Model Atmospheres Computations

1974 ◽  
Vol 3 ◽  
pp. 341-356
Author(s):  
F. Querci ◽  
M. Querci
Keyword(s):  
High Resolution ◽  
Effective Temperature ◽  
Carbon Star ◽  
Model Atmosphere ◽  
Distribution Functions ◽  
Carbon Stars ◽  
Molecular Line ◽  
Probability Distribution Functions ◽  
Synthetic Spectra ◽  
Made In

The first part of this paper presents a grid of model atmospheres for carbon stars in which the most striking feature is the inclusion of the molecular line blanketing effect of CO, CN and C2 through opacity probability distribution functions. The techniques and the main results have been fully discussed in previous papers (Querci, 1972; Querci et al., 1972 and 1973), and consequently we will give just a rapid description asking the reader to refer to these papers for details. However, the grid has been extended here to lower temperatures.The second part presents original results from the M. Querci’s ‘Thèse d’Etat’ (1974), and concerns the computation of synthetic spectra. A kind of grid of synthetic spectra has been computed from each model atmosphere, that is to say for each particular effective temperature and gravity, over a selected spectral range. The influence of the gravity and of the effective temperature on the computed spectra and the problem of the line cutting procedure are considered. Finally, comparisons with a high resolution infrared spectrum of a carbon star are made.The conclusion summarizes the experimental progress that must be made in order to be able to make meaningful comparisons between predictions and observations.

scholarly journals NLTE modeling and spectroscopically derived abundances of lithium and beryllium for classical nova ejecta

2020 ◽  
Vol 639 ◽  
pp. L12
Author(s):  
Steven N. Shore ◽  
Ivan De Gennaro Aquino
Keyword(s):  
Effective Temperature ◽  
Recent Literature ◽  
Absorption Feature ◽  
Expansion Velocity ◽  
Classical Novae ◽  
Synthetic Spectra ◽  
Classical Nova ◽  
Wide Range ◽  
Spectroscopic Feature ◽  
Solar Abundances

Context. Extreme super-solar abundances of lithium and beryllium have been reported in recent years for classical novae based on absorption lines in ultraviolet and optical spectra during the optically thick stages, but these findings have not been compared with spectrum syntheses of the ejecta. Aims. We present a grid of nova ejecta models calculated with PHOENIX aimed at simulating the reported Li I and Be II features with super-solar abundances. Methods. We computed a sequence of models, finely exploring the parameter space of effective temperature, ejecta expansion velocity, and Li and Be overabundances. Results. Regardless of temperature and expansion velocity, the synthetic spectra for large Li and Be overabundances strongly disagree with those presented in recent literature. Assuming a wide range of Be overabundances (factors of 100 to 10 000 relative to solar), we predict a much stronger spectroscopic feature at Be II 3130 Å than those so far observed. A similar overabundance for Li would instead result in a barely observable change in the emitted flux at Li I 6709 Å. The observed extended absorption feature at 3131 Å reported in V838 Her and other novae appears even in zero-Be models with only solar abundances (which for novae are underestimates). Conclusions. The computed spectra do not support the lithium and beryllium abundances, and caution is warranted in the interpretation of the phenomenology.

scholarly journals Fitting of Silicon lines in UV and Balmer Hδ Line in Optical Spectra of B supergiant HD 198478

2011 ◽  
Vol 7 (S282) ◽  
pp. 263-264
Author(s):  
Tomislav Jurkić ◽  
Mariza Sarta Deković ◽  
Dubravka Kotnik-Karuza
Keyword(s):  
Effective Temperature ◽  
Optical Spectra ◽  
Surface Gravity ◽  
Numerical Code ◽  
Atmospheric Parameters ◽  
Synthetic Spectra ◽  
Temperature Surface

AbstractAtmospheric parameters of the Galactic early B-supergiant HD 198478 (55 Cyg) were determined from the UV silicon lines and optical Balmer Hδ 4101 Å line. TLUSTY synthetic spectra were broadened using the ROTIN numerical code in order to determine effective temperature, surface gravity, rotational and macroturbulent velocity.

Development of a conical anode Fe-gun for low voltage SEM

1988 ◽  
Vol 46 ◽  
pp. 978-979
Author(s):  
T. Miyokawa ◽  
S. Norioka ◽  
S. Goto
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Low Voltage ◽  
Irradiation Damage ◽  
Cold Cathode ◽  
Virtual Source ◽  
Source Position ◽  
Electrostatic Lens ◽  
Electrostatic Lenses ◽  
Wide Range

Field emission SEMs (FE-SEMs) are becoming popular due to their high resolution needs. In the field of semiconductor product, it is demanded to use the low accelerating voltage FE-SEM to avoid the electron irradiation damage and the electron charging up on samples. However the accelerating voltage of usual SEM with FE-gun is limited until 1 kV, which is not enough small for the present demands, because the virtual source goes far from the tip in lower accelerating voltages. This virtual source position depends on the shape of the electrostatic lens. So, we investigated several types of electrostatic lenses to be applicable to the lower accelerating voltage. In the result, it is found a field emission gun with a conical anode is effectively applied for a wide range of low accelerating voltages.A field emission gun usually consists of a field emission tip (cold cathode) and the Butler type electrostatic lens.

Three-fold astigmatism: An important TEM aberration

1993 ◽  
Vol 51 ◽  
pp. 972-973 ◽  
Author(s):  
O.L. Krivanek ◽  
M.L. Leber
Keyword(s):  
High Resolution ◽  
Spatial Frequency ◽  
Field Emission ◽  
Azimuthal Angle ◽  
Hollow Cone ◽  
Small Probe ◽  
Wide Range ◽  
High Resolution Images ◽  
Image Position

Three-fold astigmatism resembles regular astigmatism, but it has 3-fold rather than 2-fold symmetry. Its contribution to the aberration function χ(q) can be written as:where A3 is the coefficient of 3-fold astigmatism, λ is the electron wavelength, q is the spatial frequency, ϕ the azimuthal angle (ϕ = tan-1 (qy/qx)), and ϕ3 the direction of the astigmatism.Three-fold astigmatism is responsible for the “star of Mercedes” aberration figure that one obtains from intermediate lenses once their two-fold astigmatism has been corrected. Its effects have been observed when the beam is tilted in a hollow cone over a wide range of angles, and there is evidence for it in high resolution images of a small probe obtained in a field emission gun TEM/STEM instrument. It was also expected to be a major aberration in sextupole-based Cs correctors, and ways were being developed for dealing with it on Cs-corrected STEMs.

Scanning tunneling microscopy of polymers: A status report

1989 ◽  
Vol 47 ◽  
pp. 330-331
Author(s):  
P.E. Russell ◽  
I.H. Musselman
Keyword(s):  
High Resolution ◽  
Scanning Tunneling Microscopy ◽  
Sample Surface ◽  
Atomic Scale ◽  
Constant Current ◽  
Scanning Tunneling ◽  
Status Report ◽  
Tunneling Microscopy ◽  
Research Issues ◽  
Wide Range

Scanning tunneling microscopy (STM) has evolved rapidly in the past few years. Major developments have occurred in instrumentation, theory, and in a wide range of applications. In this paper, an overview of the application of STM and related techniques to polymers will be given, followed by a discussion of current research issues and prospects for future developments. The application of STM to polymers can be conveniently divided into the following subject areas: atomic scale imaging of uncoated polymer structures; topographic imaging and metrology of man-made polymer structures; and modification of polymer structures. Since many polymers are poor electrical conductors and hence unsuitable for use as a tunneling electrode, the related atomic force microscopy (AFM) technique which is capable of imaging both conductors and insulators has also been applied to polymers.The STM is well known for its high resolution capabilities in the x, y and z axes (Å in x andy and sub-Å in z). In addition to high resolution capabilities, the STM technique provides true three dimensional information in the constant current mode. In this mode, the STM tip is held at a fixed tunneling current (and a fixed bias voltage) and hence a fixed height above the sample surface while scanning across the sample surface.

Sign in / Sign up

Export Citation Format

Share Document