scholarly journals THE POSIBILITY OF TRIPLE DETONATION IN WHITE DWARFS

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.

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.


1979 ◽  
Vol 53 ◽  
pp. 52-55
Author(s):  
R. Canal ◽  
J. Isern

The presence of neutron stars in close binary systems, shown by the pulsating X-ray sources, poses the problem of their origin. In the case of the low-mass (M1 + M2 ≤ 5 M⊙) X-ray binaries, the neutron star might have originated from a massive white dwarf, driven over the Chandrasekhar limit by mass transfer (Schatzman 1974). A similar scenario had been put forward by Whelan and Iben (1973) for type I supernovae. To solve the problem of the very low eccentricities observed for the orbits, and to facilitate keeping the system bound after neutron star formation, Canal and Schatzman (1976) suggested a non explosive collapse of the white dwarf to a neutron star. The occurence of this kind of collapse depended on the possibility of avoiding thermonuclear ignition by means of neutronization. Since there is a density interval where the electron captures on carbon go faster than the pycnonuclear reactions, just above the critical density for the beginning of the collapse, there seemed also to be a chance of escape from thermonuclear runaway. A closer examination of this picture leads, however, to significant changes.


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.


2007 ◽  
Vol 667 (2) ◽  
pp. 1119-1125 ◽  
Author(s):  
L. B. Zhao ◽  
P. C. Stancil

2021 ◽  
Vol 503 (4) ◽  
pp. 5397-5408
Author(s):  
Mukremin Kilic ◽  
P Bergeron ◽  
Simon Blouin ◽  
A Bédard

ABSTRACT We present an analysis of the most massive white dwarf candidates in the Montreal White Dwarf Database 100 pc sample. We identify 25 objects that would be more massive than $1.3\, {\rm M}_{\odot }$ if they had pure H atmospheres and CO cores, including two outliers with unusually high photometric mass estimates near the Chandrasekhar limit. We provide follow-up spectroscopy of these two white dwarfs and show that they are indeed significantly below this limit. We expand our model calculations for CO core white dwarfs up to M = 1.334 M⊙, which corresponds to the high-density limit of our equation-of-state tables, ρ = 109 g cm−3. We find many objects close to this maximum mass of our CO core models. A significant fraction of ultramassive white dwarfs are predicted to form through binary mergers. Merger populations can reveal themselves through their kinematics, magnetism, or rapid rotation rates. We identify four outliers in transverse velocity, four likely magnetic white dwarfs (one of which is also an outlier in transverse velocity), and one with rapid rotation, indicating that at least 8 of the 25 ultramassive white dwarfs in our sample are likely merger products.


2003 ◽  
Vol 583 (2) ◽  
pp. 878-884 ◽  
Author(s):  
Oscar Straniero ◽  
Inmaculada Dominguez ◽  
Gianluca Imbriani ◽  
Luciano Piersanti

2021 ◽  
Vol 104 (1) ◽  
Author(s):  
J. L. Ullmann ◽  
T. Kawano ◽  
B. Baramsai ◽  
T. A. Bredeweg ◽  
A. Couture ◽  
...  
Keyword(s):  

2002 ◽  
Vol 90 (2) ◽  
Author(s):  
I. Fatima ◽  
Jamshed H. Zaidi ◽  
Shujaat Ahmad ◽  
M. S. Subhani

SummaryEmploying the activation technique in combination with radiochemical separations and high-resolution γ-ray spectroscopy fission neutron spectrum averaged cross sections were measured for several (


1971 ◽  
Vol 42 ◽  
pp. 130-135 ◽  
Author(s):  
K. H. Böhm ◽  
J. Cassinelli

Outer convection zones of white dwarfs in the range 5800 K ≤ Teff ≤ 30000 K have been studied assuming that they have the same chemical composition as determined by Weidemann (1960) for van Maanen 2. Convection is important in all these stars. In white dwarfs Teff < 8000 K the adiabatic temperature gradient is strongly influenced by the pressure ionization of H, HeI and HeII which occurs within the convection zone. Partial degeneracy is also important.Convective velocities are very small for cool white dwarfs but they reach considerable values for hotter objects. For a white dwarf of Teff = 30000 K a velocity of 6.05 km/sec and an acoustic flux (generated by the turbulent convection) of 1.5 × 1011 erg cm−2 sec−1 is reached. The formation of white dwarf coronae is briefly discussed.


2020 ◽  
Vol 66 (3) ◽  
pp. 139-148
Author(s):  
Maja Vončina ◽  
Peter Cvahte ◽  
Ana Kračun ◽  
Tilen Balaško ◽  
Jožef Medved

AbstractThe alloys from Al–Mg–Si system provide an excellent combination of mechanical properties, heat treatment at extrusion temperature, good weldability, good corrosion resistance and formability. Owing to the high casting speed of rods or slabs, the solidification is rather non-equilibrium, resulting in defects in the material, such as crystalline segregations, the formation of low-melting eutectics, the unfavourable shape of intermetallic phases and the non-homogeneously distributed alloying elements in the cross-section of the rods or slabs and in the entire microstructure. The inhomogeneity of the chemical composition and the solid solution negatively affects the strength, the formability in the warm and the corrosion resistance, and can lead to the formation of undesired phases due to segregation in the material. In this experimental investigation, the cross-sections of the rods from two different alloys of the 6xxx group were investigated. From the cross-sections of the rods, samples for differential scanning calorimetry (DSC) at three different positions (edge, D/4 and middle) were taken to determine the influence of inhomogeneity on the course of DSC curve. Metallographic sample preparation was used for microstructure analysis, whereas the actual chemical composition was analysed using a scanning electron microscope (SEM) and an energy dispersion spectrometer (EDS).


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