Showing papers on "White dwarf published in 1972"
TL;DR: In this paper, the spectrum, colours and interstellar features in the star HD 226868, which is coincident with the X-ray star Cygnus X-1 and a radio star, were those of a normal BOIb supergiant.
Abstract: WE have reported1 that the spectrum, colours and interstellar features in the star HD 226868, which is coincident with the X-ray star Cygnus X-1 and a radio star2,3, were those of a normal BOIb supergiant. We made measurements of the radial velocity of the star from August 1971 to October 1971 and find it to be a velocity variable, whose changes of velocity correlate with changes in the X-ray flux.
346 citations
TL;DR: In this paper, the authors used a fully implicit Lagrangian, hydrodynamic computer code incorporating a nuclear reaction network to follow thermonuclear runaways in the hydrogen-rich envelopes of white dwarfs in order to produce a nova outburst.
Abstract: We have used a fully implicit, Lagrangian, hydrodynamic computer code incorporating a nuclear reaction network to follow thermonuclear runaways in the hydrogen-rich envelopes of white dwarfs in order to produce a nova outburst. Because of the short time-scales and the high nuclear burning rates produced in our models, the nuclear reactions are far out of equilibrium and the beta-plus unstable nuclei become the most abundant nuclei in the envelope except for hydrogen and helium. Our models have ejected 1.00017 solar mass with kinetic energies of 8 times 10 to the 44-th power ergs, a value that agrees quite closely with the observed values for novae.
210 citations
TL;DR: In this article, an upper bound of 0.7 ± 0.14 M was obtained for the mass of the pulsar component of Cen X-3, indicating that the system is likely to be a massive close binary in the second stage of mass exchange.
Abstract: An upper limit of 0.7 ± 0.14 M⊙ is obtained for the mass of the pulsar component of Cen X-3. The system is likely to be a massive close binary in the second stage of mass exchange.
145 citations
79 citations
TL;DR: In this article, five more oscillating white dwarf stars have been discovered and the data now available from these and other sources support an explanation of observed oscillations in dwarf novae in terms of g-mode pulsations.
Abstract: Five more oscillating white dwarf stars have been discovered. The data now available from these and other sources support an explanation of observed oscillations in dwarf novae in terms of g-mode pulsations.
58 citations
TL;DR: This work states that even for a modest mass transfer rate, 2023 g yr−1, the maximum probable X-ray luminosity Lx≈1036 erg s−1 can be accommodated (assuming GM/Rc2∼10−1 as in a neutron star).
Abstract: RECENT observations of the two pulsating binary X-ray sources Her X-1 (ref. 1) and Cen X-3 (ref. 2) have led to a great deal of speculation about the X-ray emission mechanism involved. Because orbital parameters have been derived from their respective Doppler curves implying orbital radii R0 of only 1011 to 1012 cm, it is natural to suppose that matter is accreted on one star from its companion. In the case of Cen X-3 with one binary member a massive star3 (∼15 M⊙), the low-mass companion (M≲0.1–1 M⊙) is presumably a collapsed object with high surface gravity (either a white dwarf, neutron star or black hole). So a large source of gravitational energy is tantalizingly available for radiation. If this were released during accretion of gas on the collapsed star (with mass M and radius R) at a rate dm/dt, the resulting steady state luminosity L≈(GM/R) (dm/dt). Even for a modest mass transfer rate, 2023 g yr−1, the maximum probable X-ray luminosity Lx≈1036 erg s−1 can be accommodated (assuming GM/Rc2∼10−1 as in a neutron star).
49 citations
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33 citations
TL;DR: The existence of variable white dwarfs has recently been spectroscopically and photometrically confirmed as discussed by the authors, and they have periods between about 200 and 1,600 s. Because the radial pulsation periods of a few s, Lasker and Hesser have attempted to explain them in terms of rotation, by analogy with pulsar theories, although the erratic nature of the periods presents some difficulties.
Abstract: THE existence of variable white dwarfs has recently been spectroscopically and photometrically confirmed1–3; they have periods between about 200 and 1,600 s. Because the radial pulsation periods of white dwarfs are of the order of a few s, Lasker and Hesser3 have attempted to explain them in terms of rotation, by analogy with pulsar theories4, although the erratic3 nature of the periods presents some difficulties.
TL;DR: In this article, it was suggested that both the 250-eV background radiation and the recently observed variations in the optical emission from certain white dwarfs may be due to thermal bremsstrahlung from hot coronae surrounding such stars.
Abstract: It is suggested that both the 250-eV background radiation and the recently observed variations in the optical emission from certain white dwarfs may be due to thermal bremsstrahlung from hot coronae surrounding such stars. The X-ray flux from the variable white dwarfs is predicted and in the most favorable case, R548, is sufficiently large to allow an observational test of the model. The possibility that the variations observed in strong X-ray sources are due to pulsations in the coronae surrounding degenerate stars, rather than in stars themselves, is also discussed. For the white dwarfs, both pulsation and rotation of the central star are found to be adequate sources of coronal energy, with pulsation being subject to relatively easy observational test. The energy requirements for the strong X-ray sources are briefly discussed.
TL;DR: In this paper, observations of the white dwarf G195-19 made for over a year show that the periodic variation in circular polarization continues with constant frequency and amplitude; an accurate value of 13309 plus or minus 00004 days is obtained for the period.
Abstract: Observations of the white dwarf G195-19 made for over a year show that the periodic variation in circular polarization continues with constant frequency and amplitude; an accurate value of 13309 plus or minus 00004 days is obtained for the period While the variation in blue-green light is sinusoidal, extensive measurements in red light show an asymmetric curve, reaching a minimum about 6 hours earlier than in the blue-green
TL;DR: In this article, photoelectric UBVr photometry is presented for 33 white-dwarf suspects from the Lowell Observatory lists, on the basis of (B- V) and (U- B) color indices, eight probable white dwarfs are identified.
Abstract: Photoelectric UBVr photometry is presented for 33 white-dwarf suspects from the Lowell Observatory lists. On the basis of (B- V) and (U- B) color indices, eight probable white dwarfs are identffied. Key words: white dwarfs - photometry
TL;DR: In this paper, a model for Cen X-3 according to which the X-ray emission comes from an atmosphere heated by shock waves produced by surface pulsations of a white dwarf is presented.
Abstract: Description of a model for Cen X-3 according to which the X-ray emission comes from an atmosphere heated by shock waves produced by surface pulsations of a white dwarf. This model can explain the luminosity, period, and spectrum of Cen X-3. The way in which these quantities vary with pulsation period and amplitude is discussed.
TL;DR: Canuto et al. as mentioned in this paper showed that a gas of free electrons can, through its magnetic moment, self consistently maintain a magnetic field B, of order 107−108 G at typical white dwarf densities, even after dissipation has extinguished any external sources (charge drifts) of the magnetic field.
Abstract: THE discovery of magnetic fields of up to ≃107 G in two white dwarfs1,2 has stimulated interest in the magnetic properties of high density matter. Discussion largely centres around the theory of Landau Orbital Ferromagnetism3–6 (LOFER), proposed by Canuto et al.3,7, which states that a gas of free electrons can, through its magnetic moment, self consistently maintain a magnetic field B, of order 107−108 G at typical white dwarf densities, even after dissipation has extinguished any external sources (charge drifts) of the magnetic field. Similarly the 1012 G fields expected for pulsars on theoretical grounds8 are comparable with the 1012−1013 G values predicted by LOFER theory for objects at neutron star densities.
01 Jan 1972
TL;DR: In this article, the structure of neutron stars and white dwarfs is discussed, and the role of solid state physics in determining their properties is also discussed; this is followed by a description of the resulting stellar models.
Abstract: This talk reviews the structure of neutron stars and white dwarfs, and the role of solid state physics in determining their properties. The nature of the matter in neutron stars (matter essentially in its absolute ground state), and the determination of its equation of state are first discussed; this is followed by a description of the resulting stellar models. Superconductivity and superfluidity in the interior, and other solid state aspects of these stars are then reviewed.