scholarly journals High Resolution Optical Spectra of 120 White Dwarfs

1989 ◽  
Vol 114 ◽  
pp. 524-524 ◽  
Author(s):  
David Tytler ◽  
Eric Rubenstein

AbstractHigh quality optical spectra of 120 white dwarfs have been obtained to search for double degenerate systems, some of which might become type I supernovae. No systems with high amplitude velocity variations have been found. However several exceptionally cool DA white dwarfs have been found to show weak Helium absorption lines, and four stars have split H-alpha line cores indicative of binary systems.

1987 ◽  
Vol 122 ◽  
pp. 319-320
Author(s):  
Klaus-Peter Schröder

Results from 58 chromospheric eclipse spectra of three ζ Aurigae type binary systems - with a K supergiant primary and a B star companion -taken with IUE at high resolution are presented. Curves of growth have been constructed at 20 phases using selected chromospheric absorption lines superposed upon the B star spectrum. In order to fit average density models to the chromospheres, 3 samples of column densities (for ζ Aur., 32 Cyg. (fig.1) and 31 Cyg. K giants) have been used.


2020 ◽  
Vol 493 (2) ◽  
pp. 2805-2816 ◽  
Author(s):  
Mukremin Kilic ◽  
A Bédard ◽  
P Bergeron ◽  
Alekzander Kosakowski

ABSTRACT We present radial velocity observations of four binary white dwarf candidates identified through their overluminosity. We identify two new double-lined spectroscopic binary systems, WD 0311–649 and WD 1606+422, and constrain their orbital parameters. WD 0311–649 is a 17.7 h period system with a mass ratio of 1.44 ± 0.06 and WD 1606+422 is a 20.1 h period system with a mass ratio of 1.33 ± 0.03. An additional object, WD 1447–190, is a 43 h period single-lined white dwarf binary, whereas WD 1418–088 does not show any significant velocity variations over time-scales ranging from minutes to decades. We present an overview of the 14 overluminous white dwarfs that were identified by Bédard et al., and find the fraction of double- and single-lined systems to be both 31 per cent. However, an additional 31 per cent of these overluminous white dwarfs do not show any significant radial velocity variations. We demonstrate that these must be in long-period binaries that may be resolved by Gaia astrometry. We also discuss the overabundance of single low-mass white dwarfs identified in the SPY survey, and suggest that some of those systems are also likely long-period binary systems of more massive white dwarfs.


2013 ◽  
Vol 9 (S297) ◽  
pp. 117-120
Author(s):  
J. Maíz Apellániz ◽  
A. Sota ◽  
R. H. Barbá ◽  
N. I. Morrell ◽  
A. Pellerin ◽  
...  

AbstractWe are using five different surveys to compile the largest sample of diffuse interstellar band (DIB) measurements ever collected. GOSSS is obtaining intermediate-resolution blue-violet spectroscopy of ~2500 OB stars, of which 60% have already been observed and processed. The other four surveys have already collected multi-epoch high-resolution optical spectroscopy of 700 OB stars with different telescopes, including the 9 m Hobby-Eberly Telescope in McDonald Observatory. Some of our stars are highly-extinguished targets for which no good-quality optical spectra have ever been published. For all of the targets in our sample we have obtained accurate spectral types, measured non-DIB ISM lines, and compiled information from the literature to calculate the extinction. Here we present the first results of the project, the properties of twenty DIBs in the 4100-5500 Å range. We clearly detect a couple of previously elusive DIBs at 4170 Å and 4591 Å; the latter could have coronene and ovalene cations as carriers.


1987 ◽  
Vol 93 ◽  
pp. 413-417
Author(s):  
R. Lopez ◽  
J. Isern ◽  
J. Labay ◽  
R. Canal

AbstractWe present models for Type I supernova light curves based on the explosion of partially solid white dwarfs in close binary systems. Studies of such explosions show that they leave bound remnants of different size. Our results reproduce quite well the maximun luminosities, the expansion velocities and the shape of the light curve. As the two basic papameters that govern the light curve, the ejected mass and the mass of 56Ni produced, are variable our models reproduce the slow and fast subclasses of “classical” Type I supernovae.


2021 ◽  
Vol 34 ◽  
pp. 40-47
Author(s):  
D.N. Doikov ◽  
A.V. Yushchenko

The induced γ-ray emissions are considered in contact cataclysmic binary systems with strong magnetic fields near white dwarfs and companion’s stars’ components. He-C-O atoms in white dwarf’s atmospheres collide with flows falling to poles as a magnetic column. Near white dwarf’s surface the falling flows with speed reaches 3 ∙ 10 6  m /s   and creates sufficient conditions for nuclear γ-radiation emission. The cross sections of nuclear γ-radiation emission are presented in 0.1 – 150 MeV energy intervals depending on the colliding atoms and particles. The mass loss from binary components is of the order of   ̇ ≈ (10 −11 − 10 −7 )Msun. We considered the collisions of p – He, α – He, p – C, α – C, p – N, α – N, p – O, α – O, C – He, C – C, C – N, C – O, N – He, N – C, N – N, N – O, O – He, O – C, O – N, and O – O types. Monochromatic energy luminosities Lγ in the above energy intervals for different modes in cataclysmic systems were calculated taking into account the loss of mass M , chemical composition and dynamics of fluxes incident on the magnetic poles. We found the dependencies between   Lγ    and chemical composition and calibrated the synthetic γ-spectra in the above pointed energy intervals. It has been concluded that power flyers are detected from p-p detonation in surface layers in white dwarf’s atmospheres. From calculation we estimated that p-p detonation time scale is in frame of the 0.07-0.1 sec. From which it is concluded that in some surface p-p explosions in the column of the magnetic field are produce significant number of positrons who has a sufficient probability to inject beyond the atmosphere of a white dwarf. It has been shown that the induce γ-ray spectroscopy together with positron spectroscopy are opens new possibilities for diagnostics of the flayers in AM Her polar system. The mechanism of triple detonation, which leads to the explosion of type I supernovae, is proposed. In this context, it is assumed that SN I type explosions occur in white dwarfs with masses not reaching the Chandrasekhar limit. The neutron formation in the matter that are in an explosive state after p-p detonation is considered separately.


Author(s):  
A. V. Crewe ◽  
J. Wall ◽  
L. M. Welter

A scanning microscope using a field emission source has been described elsewhere. This microscope has now been improved by replacing the single magnetic lens with a high quality lens of the type described by Ruska. This lens has a focal length of 1 mm and a spherical aberration coefficient of 0.5 mm. The final spot size, and therefore the microscope resolution, is limited by the aberration of this lens to about 6 Å.The lens has been constructed very carefully, maintaining a tolerance of + 1 μ on all critical surfaces. The gun is prealigned on the lens to form a compact unit. The only mechanical adjustments are those which control the specimen and the tip positions. The microscope can be used in two modes. With the lens off and the gun focused on the specimen, the resolution is 250 Å over an undistorted field of view of 2 mm. With the lens on,the resolution is 20 Å or better over a field of view of 40 microns. The magnification can be accurately varied by attenuating the raster current.


Author(s):  
Thorkild M. Rasmussen

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article. Rasmussen, T. M. (1). Aeromagnetic survey in central West Greenland: project Aeromag 2001. Geology of Greenland Survey Bulletin, 191, 67-72. https://doi.org/10.34194/ggub.v191.5130 The series of government-funded geophysical surveys in Greenland was continued during the spring and summer of 2001 with a regional aeromagnetic survey north of Uummannaq, project Aeromag 2001 (Fig. 1). The survey added about 70 000 line kilometres of high-quality magnetic measurements to the existing database of modern airborne geophysical data from Greenland. This database includes both regional high-resolution aeromagnetic surveys and detailed surveys with combined electromagnetic and magnetic airborne measurements.


Sign in / Sign up

Export Citation Format

Share Document