scholarly journals Calculated Energy Distributions for SN II

1988 ◽  
Vol 108 ◽  
pp. 412-414
Author(s):  
P.H. Hauschildt ◽  
W. Spies ◽  
R. Wehrse ◽  
G. Shaviv
Keyword(s):  
Ir Spectra ◽  
Spherical Geometry ◽  
Energy Distributions ◽  
Density Profiles ◽  
Continuous Processes ◽  
Uv And Ir Spectra ◽  
Effective Temperatures ◽  
Potential Methods ◽  
Good Agreement ◽  
Large Grid

AbstractWe have calculated a large grid of hydrogen-rich supernova photospheres, in which radii, effective temperatures, density profiles, and expansion velocities have been varied. Spherical geometry, radiative equilibrium and LTE level populations are assumed. In the quasi-exact radiative transfer, the dilution of the radiation field, and scattering as well as absorption (by all relevant continuous processes and up to 150 000 lines in some models) are accurately considered. Good agreement can be obtained with the UV and IR spectra of supernovae 1979C, 1980K, and 1987A as observed during the coasting phase. Potential methods of parameter determinations for SN II are briefly discussed.

scholarly journals Model Atmospheres for Very Cool Hydrogen-Rich White Dwarfs

1989 ◽  
Vol 114 ◽  
pp. 236-239
Author(s):  
France C. Allard ◽  
Rainer Wehrse
Keyword(s):  
White Dwarfs ◽  
Gas Pressure ◽  
Special Consideration ◽  
Solar Photosphere ◽  
Energy Distributions ◽  
Effective Temperatures ◽  
Cool White Dwarfs

In recent years cool white dwarfs have been studied for various aspects ( see e.g.Winget et al.,1987 Winget and van Horn, 1987, Koester, 1987, Llebert, 1980) and much effort has been Invested in attempts to interpret the energy distributions of these stars ( Greenstein, 1984, Zeldler-K.T. et al, 1986, Llebert et al., 1987, and others). However, it seems that in spite of these efforts the spectra in particular of the very cool objects with effective temperatures below about 6000 K are not yet fully under-stood, since they are extremely diverse and each objects needs special consideration. In addition, the analyses are extremely difficult because the principal constiuents of the atmospheres ( H, He ) and elements, which may donate the majority of electrons, are essentially invisible. Since usually only one ionlsatlon stage of an element is present, this implies that the gas pressure Pg is high ( compared e.g. to the solar photosphere ), the accurate value of Pg, however, cannot be determined reliably.

scholarly journals A comparison of EISCAT and Dynasonde measurements of the auroral ionosphere

1996 ◽  
Vol 14 (12) ◽  
pp. 1403-1412 ◽  
Author(s):  
K. J. F. Sedgemore ◽  
P. J. S. Williams ◽  
G. O. L. Jones ◽  
J. W. Wright
Keyword(s):  
Auroral Ionosphere ◽  
Incoherent Scatter Radar ◽  
Density Profiles ◽  
Incoherent Scatter ◽  
Scatter Radar ◽  
Complementary Techniques ◽  
Electron Density Profiles ◽  
Ionospheric Sounding ◽  
Over Time ◽  
Good Agreement

Abstract. Incoherent-scatter radar and ionospheric sounding are powerful and complementary techniques in the study of the Earth's ionosphere. The work presented here involves the use of the Tromsø Dynasonde as a correlative diagnostic with the EISCAT incoherent-scatter radar. A comparison of electron-density profiles shows how a Dynasonde can be used to calibrate an incoherent-scatter radar and to monitor changes in the system. Skymaps of the direction of Dynasonde echoes are compared with EISCAT-derived density profiles to illustrate how a Dynasonde can be used to measure the drift velocity of auroral features. Vector velocities fitted to Dynasonde echoes are compared with EISCAT-derived plasma velocities. The results show good agreement when the data are taken during quiet to moderately active conditions and averaged over time scales of 30 min or more.

Spectral Investigations of the Effects of 60Co-Gamma Irradiation on Iodothyronine and Iodotyrosines

1987 ◽  
Vol 41 (1) ◽  
pp. 74-79
Author(s):  
A. Obaid ◽  
S. Basahl ◽  
A. Diefallah ◽  
R. Abu-Eittah
Keyword(s):  
Ir Spectra ◽  
Gamma Irradiation ◽  
Uv Spectra ◽  
Uv And Ir Spectra ◽  
60Co Gamma ◽  
Carbonyl Absorption

Solids of 3-iodo-, 3–5–di-iodotyrosine and 3,5-di-iodothyronine were irradiated by 60Co-gamma irradiation for a period of about twenty hours. The effects of irradiation were investigated through a study of the UV and IR spectra of irradiated samples. UV spectra showed the presence of a new band at 360 nm which was assigned to the formation of IO−. IR spectra showed a strong carbonyl absorption and the removal of the carboxylate band in the case of thyronine only. For comparison, the spectra of the studied compounds were investigated before irradiation.

scholarly journals Using the CIFIST grid of CO5BOLD 3D model atmospheres to study the effects of stellar granulation on photometric colours

2018 ◽  
Vol 613 ◽  
pp. A24 ◽  
Author(s):  
A. Kučinskas ◽  
J. Klevas ◽  
H.-G. Ludwig ◽  
P. Bonifacio ◽  
M. Steffen ◽  
...  
Keyword(s):  
Main Sequence ◽  
Broad Band ◽  
Stellar Atmospheres ◽  
Spectral Energy ◽  
Energy Distributions ◽  
Different Types ◽  
Convective Motions ◽  
Effective Temperatures ◽  
Red Giant ◽  
Colour Indices

Aims. We studied the influence of convection on the spectral energy distributions (SEDs), photometric magnitudes, and colour indices of different types of stars across the H–R diagram. Methods. The 3D hydrodynamical CO5BOLD, averaged ⟨3D⟩, and 1D hydrostatic LHD model atmospheres were used to compute SEDs of stars on the main sequence (MS), main sequence turn-off (TO), subgiant branch (SGB), and red giant branch (RGB), in each case at two different effective temperatures and two metallicities, [M∕H] = 0.0 and − 2.0. Using the obtained SEDs, we calculated photometric magnitudes and colour indices in the broad-band Johnson-Cousins UBVRI and 2MASS JHKs, and the medium-band Strömgren uvby photometric systems. Results. The 3D–1D differences in photometric magnitudes and colour indices are small in both photometric systems and typically do not exceed ± 0.03 mag. Only in the case of the coolest giants located on the upper RGB are the differences in the U and u bands able reach ≈−0.2 mag at [M∕H] = 0.0 and ≈−0.1 mag at [M∕H] = −2.0. Generally, the 3D–1D differences are largest in the blue-UV part of the spectrum and decrease towards longer wavelengths. They are also sensitive to the effective temperature and are significantly smaller in hotter stars. Metallicity also plays a role and leads to slightly larger 3D–1D differences at [M∕H] = 0.0. All these patterns are caused by a complex interplay between the radiation field, opacities, and horizontal temperature fluctuations that occur due to convective motions in stellar atmospheres. Although small, the 3D–1D differences in the magnitudes and colour indices are nevertheless comparable to or larger than typical photometric uncertainties and may therefore cause non-negligible systematic differences in the estimated effective temperatures.

scholarly journals The Dark Halo – Spheroid Conspiracy

2012 ◽  
Vol 8 (S295) ◽  
pp. 208-208
Author(s):  
Rhea-Silvia Remus ◽  
Andreas Burkert ◽  
Klaus Dolag ◽  
Peter H. Johansson ◽  
Thorsten Naab ◽  
...  
Keyword(s):  
Elliptical Galaxies ◽  
Total Density ◽  
Dark Halo ◽  
Coma Cluster ◽  
Density Profiles ◽  
Stellar Component ◽  
Strong Lensing ◽  
The Galaxy ◽  
Good Agreement

AbstractObservational results from strong lensing and dynamical modeling indicate that the total density profiles of early-type galaxies are close to isothermal, i.e. ρtot ∝ rγ with γ ≈ −2. To understand the origin of this universal slope we study a set of simulated spheroids formed in cosmological hydrodynamical zoom-in simulations (see Oser et al. 2010 for more details). We find that the total stellar plus dark matter density profiles of all our simulations on average can be described by a power law with a slope of γ ≈ −2.1, with a tendency towards steeper slopes for more compact, lower mass ellipticals, while the total intrinsic velocity dispersion is flat for all simulations, independent of the values of γ. Our results are in good agreement with observations of Coma cluster ellipticals (Thomas et al. 2007) and results from strong lensing (Sonnenfeld et al. 2012). We find that for z ≳ 2 the majority of the stellar build-up occurs through in-situ star formation, i.e. the gas falls to the center of the galaxy and forms stars, causing the galaxy to be more compact and thus the stellar component to be more dominant. As a result, the total density slopes at z ≈ 2 are generally steeper (around γ ≈ −3). Between z = 2 and z = 0 galaxies grow mostly through dry merging, with each merging event shifting the slope more towards γ ≈ −2. We conclude from our simulations that the steepness of the slope of present day galaxies is a signature of the importance of mostly dry mergers in the formation of an elliptical, and suggest that all elliptical galaxies will with time end up in a configuration with a density slope of γ ≈ −2. For a more detailed analysis with a larger sample of simulations see Remus et al. (2013).

Rotational temperature profiles of shock waves in diatomic gases

1971 ◽  
Vol 49 (2) ◽  
pp. 337-351 ◽  
Author(s):  
A. K. Macpherson
Keyword(s):  
Shock Waves ◽  
Rotational Temperature ◽  
Rotational Velocity ◽  
Three Dimensional ◽  
Intermolecular Potential ◽  
Collision Dynamics ◽  
Density Profiles ◽  
Frequency Distributions ◽  
Dimensional Approximation ◽  
Good Agreement

The variation of the translational temperature, rotational temperature, and density through shock waves in oxygen and nitrogen was studied using classical laws of mechanics and a Monte Carlo scheme. The collision dynamics were calculated using an intermolecular potential by Parker with both a two-dimensional approximation and the full three-dimensional calculations. The rotational velocity frequency distributions were also calculated. The average number of collisions a molecule will experience a t various stages passing through a shock wave were found and plotted with the temperature and density profiles. The nitrogen results were compared with experimental results and good agreement was found. This also provided a method for giving a first approximation to the three-dimensional intermolecular potential.

ChemInform Abstract: UV and IR Spectra of the ClClO Molecule.

ChemInform ◽  
2010 ◽  
Vol 26 (31) ◽  
pp. no-no
Author(s):  
K. JOHNSSON ◽  
A. ENGDAHL ◽  
B. NELANDER
Keyword(s):  
Ir Spectra ◽  
Uv And Ir Spectra
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