Neutron Star Formation Research Articles

Neutrino damping of nonradial pulsations in gravitational collapse

Using simple classical neutron-gas models, it is shown that neutrino radiation may in some cases be more efficient than gravitational radiation for damping out nonradial pulsations during gravitational collapse. This implies that previous estimates of gravitational radiation from neutron-star or black-hole formation following supernovae may have been overly optimistic. Final conclusions for any particular model await detailed hydrodynamic calculations. However, this paper shows that neutrino damping is potentially important in such calculations and must be taken into account.

Competition between neutrino and gravitational radiation

This essay discusses the competition between neutrino radiation and gravitational radiation for the dominant method by which forming neutron stars radiate away their gravitational collapse energy. It is shown that neutrinos may, in fact, be the dominant mode; thus a failure to detect gravitation radiation from a supernova does not imply an error in general relativity but rather the existence of a more efficient radiation mechanism.

Observational constraints on the masses of neutron stars

Direct information on the masses of five neutron stars is available at present. The mass estimates do not yet place any serious constraints on nuclear physics theory. However, if all five neutron stars have about the same mass, then the allowed mass range is quite narrow (∼l.4–l.8M⊙) and is consistent with conventional pictures of neutron-star formation.

Evolution of massive close binaries and formation of neutron stars and black holes

Main results of computations of evolution for massive close binaries (10M⊙+9.4M⊙, 16M⊙+15M⊙, 32M⊙+30M⊙, 64M⊙+60M⊙) up to oxygen exhaustion in the core are described. Mass exchange starting in core hydrogen, shell hydrogen and core helium burning stages was studied. Computations were performed assuming both the Ledoux and Schwarzschild stability criteria for semiconvection. The influence of UFI-neutrino emission on evolution of close binaries was investigated. The results obtained allow to outline the following evolutionary chain: two detached Main-Sequence stars — mass exchange — Wolf-Rayet star or blue supergiant plus main sequence star — explosion of the initially more massive star appearing as a supernova event — collapsed or neutron star plus Main-Sequence star, that may be observed as a ‘runaway star’ — mass exchange leading to X-rays emission — collapsed or neutron star plus WR-star or blue supergiant — second explosion of supernova that preferentially disrupts the system and gives birth to two single high spatial velocity pulsars.

Competition of neutrino and gravitational radiation in neutron star formation

An investigation is conducted concerning the possibility that neutrino radiation rather than gravitational radiation may be the dominant way by which nonradial pulsations are damped out in a collapsing star. The effects of neutrino radiation on the nonradial oscillations of such objects are examined and damping times corresponding to a particular neutrino production mechanism are evaluated. The obtained results imply that neutrino radiation, by more rapid damping of the nonradial oscillations of a newly formed neutron star in a supernova explosion, would hinder gravitational radiation, thus reducing the possibility of its detection.

Supernovae and Neutron Stars

The formation of a neutron star and the event observed as a supernova are presumed by most astrophysicists to be simultaneous. The theoretical difficulty of understanding this is compounded by a hierarchy of conflicting phenomena dominated by the possibility of effective neutrino transport of the heat of the neutron star formation to the outer envelope. A thermonuclear detonation of a carbon core may take place at just the right density such that both neutron star formation and neutrino assisted envelope ejection can occur together.

On the Possibility of Neutron-Star Formation in Carbon-Detonation Supernovae

view Abstract Citations (13) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the Possibility of Neutron-Star Formation in Carbon-Detonation Supernovae Bruenn, Stephen W. Abstract The detonation-postdetonation evolutions of a variety of pre-" carbon-detonation" supernovae have been computed in order to determine the influence of model parameters and input physics on the possibility of forming neutron stars in these events. A number of conclusions are drawn. In particular, a collapse immediately prior to detonation would have a very positive influence on neutron star formation if this collapse were reasonably dynamic. The nonadiabaticity of this collapse, and the abundance of 12C in the core at this time, are also very important considerations. On the other hand, it is shown that possible future revisions in the -rates are unlikely to significantly affect the postdetonation evolution, and that a prior quasi-static phase of electron capture, or the occurrence of an off-center detonation, tends to have a negative influence on neutron-star formation. Subject headings: neutron stars - nuclear reactions - supernovae Publication: The Astrophysical Journal Pub Date: December 1973 DOI: 10.1086/152578 Bibcode: 1973ApJ...186.1157B full text sources ADS |

Neutron-Star Formation in the Carbon-Detonation Supernova

Neutrino losses, such as those driven by the convective Urca process, may affect the evolution of stars in the mass range from 4 to 8 solar masses so as to lead to collapse of their degenerate carbon/oxygen cores. A corresponding hydrodynamic model is computed which leads to the formation of a 1.3 to 1.4 solar mass neutron star with the expulsion of a small fraction of the mass, about 0.l solar mass at about 20,000 km/sec into the overlying hydrogen envelope. This sets the stage for the Ostriker-Gunn mechanism in which Type II supernovae and pulsars are formed.

Multiple Pulsar Ejection in Supernova Events

Fragmentation in the collapse of a supernova core, followed by energy loss in neutron star formation, is shown to lead to disruption of the resulting system. The elements of the system, some of which should be pulsars, can attain velocities of the order of 103 km/sec if currently quoted parameters are correct.

Pulsars and Close Binary Systems

It is first considered what must happen if pulsars (i.e. neutron stars) are formed in close binary systems (CBS), and whether the resulting orbital motion and mass transfer should be observable. As this set of alternatives seems unlikely, there follow suggestions of how one might prevent the formation of neutron stars in close binaries. Finally, it is shown that ‘runaway’ pulsars with velocities larger than about 15 km/sec cannot be produced by isotropic supernova explosions within close binaries, and an alternative explanation is suggested for the observed correlation of periods of pulsars with their distances from the galactic plane.

Relativistic isentropic stellar models

Relativistic, isentropic, homogeneous models are constructed by a method that automatically detects instabilities, and evolutionary tracks of central conditions are shown on a (T, ϱ) diagram. Models heavier than 20M⊙ become unstable because of pair creation. Iron photodisintegration causes instability in the mass range between 1.5M⊙ and 20M⊙. General relativistic effects bring about the onset of instability in models of 1.2–1.5M⊙ when the central density is about 1010 g/cm3. Lighter models become white dwarfs. It is pointed out that general relativistic instability will prevent the formation of neutron stars through hydrostatic evolution and may be relevant in setting off low-mass supernovae.

Pulsars and Neutron Star Formation

THE current popularity of the rotating neutron star hypothesis as an explanation of pulsars suggests that a re-examination of the problem of the formation of neutron stars is appropriate. In particular it is of interest to know the predictions of the theory of stellar evolution concerning the formation of neutron stars and the type of object from which they are formed. I present here a few plausible assumptions that lead to some surprising]y general predictions. It will be suggested that pulsars are formed from massive O stars; observational tests of this hypothesis are possible and will be discussed.

An Observable Peculiarity of the Brans-Dicke Radiation Zone

It is pointed out that the Brans-Dicke theory predicts a transverse spin-0 component of the $O({r}^{\ensuremath{-}1})$ radiative Riemann tensor. Unlike the conventional spin-2 radiative Riemann tensor, monopole oscillations may serve as a source. Under favorable conditions, neutron star formation within our galaxy will be detectable by Weber's gravitational-wave receiver.

Dense Stars and Problems of Their Detection.

Extraterrestrial detection and final evolution of presupernova stars culminating in neutron star formation

On the Theory and Observation of Highly Collapsed Stars

The investigation presented here falls into two parts. In the first part (Sections A to H) the general relativistic solution given by Schwarzschild of the problem of a homogeneous sphere of constant density is discussed. For every given density a characteristic mass Ml exists, for which the pressure in the center of the sphere becomes infinite, and for which the velocity of light in the same point becomes equal to zero. In the case of collapsed neutron stars. Ml is of the order of a large stellar mass. The effective mass and the gravitational energy of the sphere are determined as functions of its proper mass. Equations are developed which express the velocity and the wave-length of light as functions of the distance from the center of the sphere. The characteristic mass Ml of collapsed neutron stars is expressed in terms of the charge and mass of the electron and the proton and the universal gravitational constant. Some possible relations of the results obtained with recent cosmological theories are pointed out. The second part of this paper deals with the possibility of actually observing the formation of collapsed neutron stars. The hypothesis is examined that supernova outbursts are caused by the formation of neutron stars. A number of reasons are advanced which make this hypothesis attractive. From the data which were obtained from numerous observations of the bright supernova (1937) in the extragalactic spiral IC 4182, a number of consequences of the neutron star hypothesis are developed. In particular the redshift in the spectrum of the supernova IC 4182 is interpreted as a gravitational redshift. On this interpretation it follows that some of the physical characteristics of the central star of a supernova one year after maximum brightness are (in order of magnitude) as follows: radius 100 km, average density 10^12 g/cm^3 and effective surface temperature greater than 5×10^6 degrees. The light curves, the spectra and the total generation of energy in supernovae are discussed in the light of the neutron star hypothesis.