April 30, 2002
The binaries PSR J1141-6545 and PSR B2303+46 each appear to contain a white dwarf which formed before the neutron star. We describe an evolutionary pathway to produce these two systems. In this scenario, the primary transfers its envelope onto the secondary which is then the more massive of the two stars, and indeed sufficiently massive later to produce a neutron star via a supernova. The core of the primary produces a massive white dwarf which enters into a common envelope with the core of the secondary when the latter evolves off the main sequence. During the common envelope phase, the white dwarf and the core of the secondary spiral together as the envelope is ejected. The evolutionary history of PSR J1141-6545 and PSR B2303+46 differ after this phase. In the case of PSR J1141--6545, the secondary (now a helium star) evolves into contact transferring its envelope onto the white dwarf. We propose that the vast majority of this material is in fact ejected from the system. The remains of the secondary then explode as a supernova producing a neutron star. Generally the white dwarf and neutron star will remain bound in tight, often eccentric, systems resembling PSR J1141-6545. These systems will spiral in and merge on a relatively short timescale and may make a significant contribution to the population of gamma ray burst progenitors. In PSR B2303+46, the helium-star secondary and white dwarf never come into contact. Rather the helium star loses its envelope via a wind, which increases the binary separation slightly. Only a small fraction of such systems will remain bound when the neutron star is formed (as the systems are wider). Those systems which are broken up will produce a population of high-velocity white dwarfs and neutron stars.
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October 30, 1997
The formation and evolution of binaries which contain two neutron stars or a neutron star with a black hole are discussed in detail. The evolution of the distributions in orbital period and eccentricity for neutron star binaries are studied as a function of time. In the model which fits the observations of high mass binary pulsars best the deposition of orbital energy into common envelopes has to be very efficient and a kick velocity distribution has to contain a significant ...
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We discuss the formation of pulsars with massive companions in eccentric orbits. We demonstrate that the probability for a non-recycled radio pulsar to have a white dwarf as a companion is comparable to that of having an old neutron star as a companion. Special emphasis is given to PSR B1820-11 and PSR B2303+46. Based on population synthesis calculations we argue that PSR B1820-11 and PSR B2303+46 could very well be accompanied by white dwarfs with mass > 1.1Msun. For PSR B18...
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We have recently measured the angle between the spin and orbital angular momenta of PSR B1534+12 to be either 25+/-4 deg or 155+/-4 deg. This misalignment was almost certainly caused by an asymmetry in the supernova explosion that formed its companion neutron star. Here we combine the misalignment measurement with measurements of the pulsar and companion masses, the orbital elements, proper motion, and interstellar scintillation. We show that the orbit of the binary in the Ga...
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We report on the discovery of PSR J1141-6545, a radio pulsar in an eccentric, relativistic 5-hr binary orbit. The pulsar shows no evidence for being recycled, having pulse period P = 394 ms, characteristic age tau_c = 1.4 x 10^6 yr, and inferred surface magnetic dipole field strength B = 1.3 x 10^12 G. From the mass function and measured rate of periastron advance, we determine the total mass in the system to be (2.300 +/- 0.012) solar masses, assuming that the periastron adv...
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