scholarly journals The Abundances of Cobalt and Nickel in the Atmosphere of 78 Vir (A2p SrCrEu)

2022 ◽  
Vol 6 (1) ◽  
pp. 9
Author(s):  
Richard Monier
Keyword(s):  
Convincing Evidence ◽  
Ultraviolet Spectrum ◽  
Rotational Period ◽  
Solar Abundance ◽  
Long Wavelength ◽  
Chemically Peculiar ◽  
Long Wave ◽  
Cobalt And Nickel

Abstract Cobalt and nickel abundances are rarely available for normal and Chemically Peculiar A stars because the strongest transitions of Co ii and Ni ii fall in the mid-UV. The abundances of cobalt and nickel are derived for 78 Vir using a mean mid-ultraviolet spectrum constructed by coadding 10 spectra collected with the Long Wave Prime and Long wavelength Redundant cameras over the 18 yr of the IUE mission. The strong transitions of Co ii at 2286.16 Å, 2307.86 Å, 2324.32 Å and 2580.33 Å and that of Ni ii et 2287.09 Å are present and more or less affected by blends. The least blended, λ 2286.16 Å, yields a mean overabundance of cobalt of 5 times the solar abundance, the Ni ii line at 2287.09 Å yields a 3 times solar overabundance. There is no convincing evidence that these lines varied in the spectra analyzed. The rotational period of 78 Vir estimated from its recent TESS lightcurve is 3.723 ± 0.055 days.

scholarly journals The Abundances of Zinc and Copper in the Atmospheres of 78 Vir (A2p SrCrEu) and θ Leo (A2 IV)

2022 ◽  
Vol 6 (1) ◽  
pp. 15
Author(s):  
Richard Monier
Keyword(s):  
Spectral Synthesis ◽  
Convincing Evidence ◽  
Long Wavelength ◽  
Ultraviolet Spectra ◽  
Chemically Peculiar ◽  
Long Wave ◽  
Strong Transition

Abstract Zinc and Copper abundances are rarely available for normal and Chemically Peculiar A stars because the strongest transitions of Zn ii and Cu ii fall in the mid-UV. Estimates of the abundances of zinc and copper are derived for 78 Vir (A2p SrCrEu) and θ Leo (A2 IV) using mean mid-ultraviolet spectra constructed by coadding individual spectra collected with the Long Wave Prime and Long wavelength Redundant cameras over the 18 yr of the IUE mission. The strong transition of Cu ii at 2135.98 Å is present in 78 Vir and θ Leo but definitely stronger in 78 Vir, whereas all Zn ii lines are blended. Spectral synthesis of the least blended lines yields estimates of the abundances of zinc and copper of about 4.92 and 4.95 respectively in θ Leo and 5.82 and 5.19 in 78 Vir (on a scale where log(H) = 12). There is no convincing evidence that these lines varied in the spectra analyzed for both stars.

scholarly journals An update on the rotational period of the magnetic chemically peculiar star CU Virginis

2013 ◽  
Vol 431 (3) ◽  
pp. 2106-2110 ◽  
Author(s):  
Diane M. Pyper ◽  
Ian R. Stevens ◽  
Saul J. Adelman
Keyword(s):  
Rotational Period ◽  
Peculiar Star ◽  
Chemically Peculiar

scholarly journals The IUE Ultraviolet Spectrum of PC 11

1993 ◽  
Vol 155 ◽  
pp. 398-398 ◽  
Author(s):  
M. Parthasarathy ◽  
S.R. Pottasch ◽  
J. Clavel
Keyword(s):  
Short Wavelength ◽  
Planetary Nebula ◽  
Significant Variation ◽  
Central Star ◽  
Ultraviolet Spectrum ◽  
Emission Lines ◽  
Symbiotic Star ◽  
Iras Source ◽  
Long Wavelength ◽  
Cold Dust

PC 11 (HD 149427, PK 331-5 1) is classified as a young planetary nebula with strong OIII 4363Å and a Zanstra temperature of TZ = 27000K. It is also classified as (D′ — type) yellow symbiotic star with A — F type companion. It is an IRAS source with detached cold dust with far intrared (IRAS) colours similar to planetary nebulae. The IUE short wavelength (SWP) spectra show emission lines due to OIII] (1661/1666Å). NIII] (1746/1754Å) CIII] (1907/1909Å). The OIII] and NIII] emission lines show significant variation. Variation in the strength of CIII] is not very significant. The strength of OIII] has decreased and NIII] has increased. The long wavelength (LWP) spectrum shows stellar continuum (A-F) and absorption lines due Mg II 2800Å feature. It also show emission lines at 2772Å (?) 3133Å −3140Å (very strong) (OIII, [FeV], 3209Å (He II?) ([FEII]). The variation in the strength of emission line due OIII] and NIII] and the presence of stellar continuum (A-F) suggests that the central star of PC 11 is a binary.

Long Wave-Length Buckling of Periodic Open-Cell Foams Subjected to Uniaxial Compression

2007 ◽  
Vol 345-346 ◽  
pp. 81-84
Author(s):  
Dai Okumura ◽  
Atsushi Okada ◽  
Nobutada Ohno
Keyword(s):  
Finite Element ◽  
Uniaxial Compression ◽  
Wave Length ◽  
Elastic Buckling ◽  
Element Analysis ◽  
Open Cell ◽  
Long Wavelength ◽  
Onset Condition ◽  
Long Wave ◽  
Open Cell Foams

In this study, the elastic buckling strength of cubic open-cell foams subjected to uniaxial compression is investigated using the homogenization framework developed by the present authors (Ohno et al., JMPS 2002; Okumura et al., JMPS 2004). First of all, based on the framework, the microscopic bifurcation and macroscopic instability of cubic open-cell foams are numerically analyzed by performing finite element analysis. It is thus shown that long wavelength buckling is the primary mode and occurs just after the onset of macroscopic instability. Then, a solution for predicting the stress of long wavelength buckling is analytically derived from the onset condition of macroscopic instability. The validity of this analytical solution is demonstrated by the finite element results.

scholarly journals HST/STIS analysis of the first main sequence pulsar CU Virginis

2019 ◽  
Vol 625 ◽  
pp. A34 ◽  
Author(s):  
J. Krtička ◽  
Z. Mikulášek ◽  
G. W. Henry ◽  
J. Janík ◽  
O. Kochukhov ◽  
...  
Keyword(s):  
Radio Emission ◽  
Main Sequence ◽  
Flux Distribution ◽  
Mass Loss Rate ◽  
Rotational Period ◽  
Uv Spectrum ◽  
Chemically Peculiar ◽  
Peculiar Stars ◽  
Chemically Peculiar Stars

Context. CU Vir has been the first main sequence star that showed regular radio pulses that persist for decades, resembling the radio lighthouse of pulsars and interpreted as auroral radio emission similar to that found in planets. The star belongs to a rare group of magnetic chemically peculiar stars with variable rotational period. Aims. We study the ultraviolet (UV) spectrum of CU Vir obtained using STIS spectrograph onboard the Hubble Space Telescope (HST) to search for the source of radio emission and to test the model of the rotational period evolution. Methods. We used our own far-UV and visual photometric observations supplemented with the archival data to improve the parameters of the quasisinusoidal long-term variations of the rotational period. We predict the flux variations of CU Vir from surface abundance maps and compare these variations with UV flux distribution. We searched for wind, auroral, and interstellar lines in the spectra. Results. The UV and visual light curves display the same long-term period variations supporting their common origin. New updated abundance maps provide better agreement with the observed flux distribution. The upper limit of the wind mass-loss rate is about 10−12 M⊙ yr−1. We do not find any auroral lines. We find rotationally modulated variability of interstellar lines, which is most likely of instrumental origin. Conclusions. Our analysis supports the flux redistribution from far-UV to near-UV and visual domains originating in surface abundance spots as the main cause of the flux variability in chemically peculiar stars. Therefore, UV and optical variations are related and the structures leading to these variations are rigidly confined to the stellar surface. The radio emission of CU Vir is most likely powered by a very weak presumably purely metallic wind, which leaves no imprint in spectra.

On the stability of nonlinear waves coexisting with plasma beams

1975 ◽  
Vol 13 (1) ◽  
pp. 173-187 ◽  
Author(s):  
E. Infeld ◽  
G. Rowlands
Keyword(s):  
Nonlinear Wave ◽  
Growth Rates ◽  
Three Dimensional ◽  
Stationary Waves ◽  
One Dimensional ◽  
Long Wavelength ◽  
Long Wave ◽  
Set Up ◽  
The Stability ◽  
The One

In this paper we consider the stability of one-dimensional stationary waves set up by two counter-streaming beams of electrons in a background of stationary ions. The perturbations considered are long-wave in a direction perpendicular to the wave. The presence of a uniform magnetic field in the direction of the wave and the effect of a perpendicular pressure are taken into account. In the long-wavelength limit growth rates are diminished by the nonlinear wave. When the amplitude of this wave tends to its maximum value, the growth rates tend to zero. Thus the wave has a stabilizing effect for long-wave perturbations. Three- dimensional effects lead to additional instabilities which are also quenched by the nonlinear wave, but not as fast as the one-dimensional calculation indicates.

scholarly journals First detection of bromine and antimony in hot stars

2018 ◽  
Vol 614 ◽  
pp. A96 ◽  
Author(s):  
K. Werner ◽  
T. Rauch ◽  
M. Knörzer ◽  
J. W. Kruk
Keyword(s):  
Model Atmosphere ◽  
Atomic Diffusion ◽  
Laboratory Measurements ◽  
Solar Abundance ◽  
Hot Stars ◽  
Chemically Peculiar ◽  
Peculiar Stars ◽  
Resonance Doublet ◽  
Chemically Peculiar Stars ◽  
Far Ultraviolet

Bromine (Z = 35) and antimony (Z = 51) are extremely difficult to detect in stars. In very few instances, weak and mostly uncertain identifications of Br I, Br II, and Sb II in relatively cool, chemically peculiar stars were successful. Adopted solar abundance values rely on meteoritic determinations. Here, we announce the first identification of these species in far-ultraviolet spectra of hot stars (with effective temperatures of 49 500–70 000 K), namely in helium-rich (spectral type DO) white dwarfs. We identify the Br VI resonance line at 945.96 Å. A previous claim of Br detection based on this line is incorrect because its wavelength position is inaccurate by about 7 Å in atomic databases. Taking advantage of precise laboratory measurements, we identify this line as well as two other, subordinate Br VI lines. Antimony is detected by the Sb V resonance doublet at 1104.23/1225.98 Å as well as two subordinate Sb VI lines. A model-atmosphere analysis reveals strongly oversolar Br and Sb abundances that are caused by radiative-levitation dominated atomic diffusion.

scholarly journals Concentration Fluctuation in Long Wavelength Limit in Liquid Magnesium Alloy

2011 ◽  
Vol 2 ◽  
pp. 47-49
Author(s):  
D Adhikari ◽  
B. P. Singh ◽  
I. S. Jha
Keyword(s):  
Order Parameter ◽  
Short Range ◽  
Short Range Order ◽  
Wave Length ◽  
Concentration Fluctuation ◽  
Chemical Order ◽  
Long Wavelength ◽  
Long Wave ◽  
Associated Solution Model ◽  
Associated Solution

The microscopic structure of MgSn liquid alloy at 1073K has been studied by using regular associated solution model. For this we have calculated the concentration fluctuation in long wave length limit [SCC(0)] and chemical short range order parameter (α1) of liquid MgSn alloy at 1073 K.Keywords: Binary Alloy; Complex; Chemical order; Microscopic FunctionThe Himalayan Physics Vol.2, No.2, May, 2011Page: 47-49Uploaded Date: 1 August, 2011

Fluctuation Hydrodynamics, Thermophoresis of Nanoparticles and Heat Transfer in Nanofluids

2012 ◽  
Author(s):  
Alexandr S. Dmitriev
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Brownian Motion ◽  
Temperature Gradient ◽  
Long Wavelength ◽  
Long Wave ◽  
New Type ◽  
The One ◽  
Fluid Hydrodynamics ◽  
Two Fluid

In this paper we studied in the framework of two-fluid hydrodynamics with fluctuations the behavior of nanoparticles in the liquid with temperature gradient [1, 2]. It is shown that the acoustic long-wave fluctuations are not damped in liquids (long-wavelength phonons) and leads to an additional force acting on the nanoparticles, as well as lead to the emergence of a new force of thermophoresis [3], which is proportional to the temperature in three second degree. It is also shown that such a thermophoresis force arising under the two-fluid hydrodynamics, can lead to instability of an ensemble of nanoparticles in the presence of a temperature gradient. The last effect leads to the possible merger of the nanoparticles in the form of elongated clusters. The appearance of such clusters on the one hand, leads to an increase in effective thermal conductivity of nanofluids, and secondly, appearing elongated clusters contribute to the propagation of long-wavelength phonons along of such clusters. In fact, this new type of heat transfer in nanofluids, which must be considered in addition to the Brownian motion of nanoparticles.

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