Binary Radio Pulsars Research Articles

A refractive model for eclipsing binary radio pulsars

view Abstract Citations (19) References (16) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Refractive Model for Eclipsing Binary Radio Pulsars Emmering, Robert T. ; London, Richard A. Abstract A model for binary radio pulsars is presented in which refraction by a plasma in an extended stellar atmosphere or wind causes radio eclipses. Based on PSR applying this model to PSR 1957 + 20, it is found that refractive eclipses can be created with wind densities of order 10 to the 7th/cu cm near the apparent eclipse radius of 0.7 solar. This density is easily obtained in an X-ray excited wind. A power-law density falloff can match the observed frequency dependence of the eclipse. The physics of a wind resulting from high-energy irradiation of the pulsar's companion is described. It is estimated that the mass flux in such a wind is sufficient to achieve the densities needed for refractive eclipses. Publication: The Astrophysical Journal Pub Date: November 1990 DOI: 10.1086/169368 Bibcode: 1990ApJ...363..589E Keywords: Eclipsing Binary Stars; Pulsars; Radio Stars; Stellar Models; Companion Stars; Cosmic Plasma; Density Distribution; Stellar Atmospheres; Stellar Winds; Astrophysics; PULSARS; STARS: ECLIPSING BINARIES; STARS: WINDS full text sources ADS | data products SIMBAD (1)

The evolutionary history of PSR 0655+64 and PSR 1913+16

We intend to point out that existing evolutionary scenario for the genesis of the binary radio pulsars like PSR 0655+64 (P∼1 d) and 1913+16 (P∼8 hr) having short orbital periods and relatively massive companion (>0.5M *) is inconsistent in that it does not allow for a prolonged phase of angular momentum transfer. We propose here a modified evolutionary scenario where there is such a prolonged phase of angular momentum transfer from a low mass helium star to the neutron star mediated by an accretion disk along the so-called caseB evolutionary track.

Evolution of wide binary millisecond pulsars in globular clusters

The evolution of a binary radio pulsar in a wide orbit about a low-mass degenerate dwarf companion in a globular cluster environment is investigated. An extensive series of numerical scattering experiments is used to study encounters between such a pulsar and passing cluster field stars. A wide range of initial orbital periods from 3 to 1000 days is considered with a corresponding range of masses for the degenerate dwarf companions. The calculative results are summarized in the form of scattering cross sections. In particular, cross sections are presented for three final 'channels' in which the end product of the encounter is an isolated neutron star. Cross sections for inducing various orbital eccentricities into initially circular orbits are also derived. The implications of the results for the formation of the single millisecond pulsars in M28 and M15 and for the nearly circular obit of the M4 binary radio pulsar are discussed.

Pulsar magnetic moment decay due to radiation damping and the pulsar in SN 1987 A

A new theory is proposed to account for the decay of the pulsar magnetic moment in terms of radiation damping mechanism. Detailed comparisons with the up-to-date pulsar observations are made. The theory is then applied to binary radio pulsars thereby resolving the dilemma concerning the ages and the magnetic fields of the pulsars PSR 0655+64 and PSR 1855+09. Finally a prediction is made concerning the period and period derivative of the pulsar in SN 1987 A.

Gravitational Collapse of Mass-Accreting White Dwarfs

Massive star (M ≥ 10 M ) core collapse is the standard mechanism for neutron star formation (see Brown 1988 for a recent review). It has long been realized (see, for instance, van den Heuvel 1988, and references therein) that the neutron stars found in different types of binary systems cannot come from such a standard mechanism. Those systems include wide binary radio pulsars, millisecond pulsars (not in wide binaries), galactic bulge X–ray sources (including QPO’s), type I X–ray burst sources and X–ray transients, andγ–ray sources. Formation of those neutron stars is now widely attributed to the gravitational collapse of a white dwarf, growing above Chandrasekhar’s limit by mass accretion from the current neutron star’s companion in the binary system (Canal and Schatzman 1976; Canal and Isern 1979; Canal, Isern, and Labay 1980; Miyaji et al. 1980). Mass growth up to dynamical instability means that both explosive ejection of the accreted layers and explosive disruption of the whole star must be avoided. The former is associated with the nova phenomenon. The latter, with the occurrence of type I supernovae.

Birthrates of low-mass binary pulsars and low-mass X-ray binaries

The commonly accepted hypothesis that low-mass binary radio pulsars (LMBPs) are the end products of low-mass X-ray binaries (LMXBs). The birthrates of LMBPs are determined from a careful analysis of nine pulsar surveys, including several recent ones that were sensitive to millisecond pulsars. It is shown that only the long-period LMXBs can evolve to form objects similar to the known LMBPs. The birthrates of the Galactic LMXBs are evaluated using published X-ray catalogs and accretion lifetimes from stellar evolution models. 59 references.

Formation of binary radio pulsars

In the framework of the standard scenario of the evolution of massive binary stars a study is made of the formation of final binary systems in which at least one of the components is a neutron star. It is found that about every fortieth radio pulsar must be a member of a close binary system. This is confirmed by observations. Radio pulsars are not formed in wide binary systems, possibly because of the very slow rotation of the presupernova stars.

Binary Pulsars: Observations and Implications

The Galaxy contains a large number of neutron stars in gravitation-ally bound binary systems. Among the most fruitful of these to study have been the binary radio pulsars, of which seven are now known. Unlike the “accretion-powered” neutron stars located in mass-exchanging X-ray binary systems, the “rotation-powered” binary radio pulsars are found in dynamically simple, clean systems in which both stellar components have already completed their nuclear evolution, thereby shedding their atmospheres and most of their mass. In such circumstances the orbital parameters of the system and the rotational parameters of the pulsar can be determined with high precision from analysis of pulse timing data. These measurements constrain the component masses and yield an estimate of the pulsar's magnetic dipole moment, which turns out to be an essential parameter in understanding the evolution of the systems. In this paper I review the known facts concerning binary pulsars, and then briefly discuss some implications for our understanding of the place of neutron stars in stellar evolution.

Millisecond Pulsar Formation and Evolution

The evolutionary history of binary radio pulsars, including the two millisecond binary pulsars, is reviewed. There are two groups of binary pulsars, the PSR 1913+16-group, which descended from massive X-ray binaries, and the PSR 1953+29-group, which descended from fairly wide low-mass X-ray binaries. The neutron stars in the second group probably formed by the accretion-induced collapse of a massive white dwarf. The companion stars in both groups of systems are expected to be dead stars, i.e. white dwarfs or neutron stars.The large total number of millisecond binary pulsars in the galaxy (∼ 104), indicates that magnetic fields of neutron stars do not decay below a value of order 109 G. Possible explanations for this phenomenon are discussed.Coalescence with a close degenerate companion provides a viable model for the formation of the single millisecond pulsar.

The Galactic Pulsar Population and Neutron Star Birth

The radio pulsars in the Galaxy are found predominantly in the disk, with a scale height of several hundred parsecs. After allowing for pulsar velocities, the data are consistent with the hypothesis that single pulsars form from massive stellar progenitors. The number of active single pulsars in the Galaxy is ∼ 1.5 × 105, and their birthrate is 1 per ∼ 60 yrs. There is some evidence that many single pulsars, particularly those with high magnetic fields, are born spinning slowly, with initial periods ∼ 0.5–1s. This could imply an origin through binary “recycling” followed by orbit disruption, or might suggest that the pre-supernova stellar core efficiently loses angular momentum to the envelope through magnetic coupling. The birthrate of binary radio pulsars, particularly of the millisecond variety, seems to be much larger than previous estimates, and might suggest that these systems do not originate in low mass X-ray binary systems.

Evidence for an asymptotic lower limit to the surface dipole magnetic field strengths of neutron stars

The discovery of a second millisecond binary radio pulsar1, PSR1855+09 (period P = 5ms), with a relatively wide circular orbit and low mass function indicates that the incidence of such systems (see also refs 2, 3) among the galactic radio pulsar population is ∼4 × 10−3. The generally accepted model for the origin of these systems is that they have descended from low-mass X-ray binaries in which a weakly magnetized neutron star3 was spun-up by the accretion of matter from an evolved low-mass (⩽1.2 M⊙) companion star, which has now ended its life as a helium white dwarf3–8. We show here that, based on the incidence of the progenitor low-mass X-ray binaries (LMXBs), the observed incidence of millisecond binary radio pulsars can be explained only if, at their present low field strength of ∼109G, the decay timescale of neutron-star surface magnetic dipole moments is 322153a0109 yr. This possibility has been advanced by Kulkarni9, who estimates, based on the optical detection of the counterpart of the weak-field binary radio pulsar PSR0655 + 64, that this pulsar is old (>5 × 108 yr) and hence that the magnetic field decay timescale becomes very large (>109 yr) for field strengths ≲1010 G. Our findings provide independent support for this possibility.

Magnetic field decay and the origin of neutron star binaries

view Abstract Citations (267) References (97) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Magnetic Field Decay and the Origin of Neutron Star Binaries Taam, R. E. ; van den Heuvel, E. P. J. Abstract The origin of magnetized neutron stars in bineries and the 1.55 ms pulsar is examined in terms of the magnetic field decay model for radio pulsars with a decay time scale of order 5 x 10 to the 6th yr over 7-10 e-foldings. Observational data of pulsing X-ray sources, nonpulsing X-ray sources, and binary radio pulsars are analyzed. Evolutionary scenarios for Her X-1, MXB 1730-335, 4U 1626-67, GX 1 + 4, 1E 2259 + 59, and long-period binary pulsars are described. The data reveal that: magnetic field strengths for accretion-powered X-ray pulsars in massive binaries and rotation-powered radio pulsars in short-period binaries support the formation of these neutron stars by core collapse following the Fe photodisintegration phase of a He-core remnant that resulted from mass transfer; however, the magnetic field strengths for neutron stars low-mass X-ray binaries and in wide radio pulsar binaries are explained if the magnetized neutron stars were formed less than 10 to the 8th years ago by accretion-induced collapse of a massive white dwarf. It is noted that with these two formation models all observations of the magnetic fields of neutron star in binaries are consistent with one single-field decay time scale consistent with one single-field decay time scale down to a surface field strength of less than or equal to 3 x 10 to the 9th G. Publication: The Astrophysical Journal Pub Date: June 1986 DOI: 10.1086/164243 Bibcode: 1986ApJ...305..235T Keywords: Binary Stars; Neutron Stars; Stellar Magnetic Fields; Stellar Physics; Decay; Field Strength; Radio Stars; Stellar Evolution; Stellar Mass Accretion; Astrophysics; STARS: BINARIES; STARS: MAGNETIC; STARS: NEUTRON full text sources ADS | data products SIMBAD (13)

Models for the formation of binary and millisecond radio pulsars

The peculiar combination of a relatively short pulse period and a relatively weak surface dipole magnetic field strength of binary radio pulsars finds a consistent explanation in terms of (i) decay of the surface dipole component of neutron-star magnetic fields on a timescale of (2–5) × 106 yr, in combination with (ii) spin-up of the rotation of the neutron star during a subsequent mass-transfer phase. The four known binary radio pulsars appear to fall into two different categories. Two of them, PSR 0655 + 64 and PSR 1913 + 16, have short orbital periods ( 0.7M⊙) white dwarf. Only in the last-mentioned case is a position of the pulsar close to the galactic plane a natural consequence. In the first-mentioned case the progenitor system most probably was a cataclysmic-variable binary in which the white dwarf collapsed by accretion.

Two types of binary radio pulsars with different evolutionary histories

The four known binary radio pulsars (Table 1) seem to fall into two different categories. Two of them, PSR0655 + 64 and PSR1913 + 16, have short orbital periods ( 0.8 M⊙ (respectively, about 1 M⊙ and 1.4 M⊙ (ref. 2)). The other two, PSR0820 + 02 and PSR1953 + 29, have long orbital periods (≳ 120 days), nearly circular orbits and low almost identical mass functions of ∼3 × 10−3 M⊙, suggesting companion masses of ∼0.2–0.4 M⊙ (refs 3–5). We point out here that these two classes of systems are expected to be formed by the later evolution of binaries consisting of a neutron star and a normal companion star, in which the companion was (considerably) more massive than the neutron star, or less massive than the neutron star, respectively. Mass transfer from an evolved companion that is more massive than the neutron star (more precisely, mass ratio ⩾0.85 (refs 6, 7)) tends to be unstable and to lead to runaway mass transfer and spiral-in resulting in a very short orbital period, whereas mass transfer from an evolved companion that is less massive than the neutron star is stable and leads to expansion of the orbit6,7. Furthermore, we point out that in the systems with a less massive companion, the neutron star most probably was formed by the accretion-induced collapse of a white dwarf. Such a model explains in a natural way why PSR1953 + 29 has a millisecond rotation period and why PSR0820 + 02 has not.

Evolutionary history of the 6.1-ms pulsar

Boriakoff et al.1 have reported the discovery of a 6.1-ms radio pulsar in a binary with an orbital period of 120 days, a1 sin i = 0.99 × 1012 cm, and e ≈ 0. This is the fourth binary radio pulsar, and the third to have a nearly circular orbit2. The origin of such systems has been discussed frequently3,4 and I now report that evolutionary history of the new millisecond pulsar is perhaps the simplest of them all. The rapid rotation of the pulsar, small mass function, circular orbit, and long binary period suggest that following the formation of a neutron star there had to be a phase of mass transfer from the low-mass secondary onto the neutron star primary. That mass transfer circularized the orbit and spun up the primary, and it required the secondary to be a red giant at that time. The present binary period of 120 days implies that the secondary has a mass of 0.3 M⊙. The observed mass function of 0.0027M⊙ implies that the primary must be less massive than 3.1M⊙, not an interesting mass limit for a neutron star. The secondary is probably a white dwarf at present. However, if the mass transfer terminated < 106 yr ago then the secondary may be still burning hydrogen at the rate of about 300L⊙, and it may be optically detectable.

Initial spin and magnetic field of the fast pulsar 4C21.53

The newly discovered pulsar 4C21.53 is the fastest pulsar known with a period1 P≃1.6 ms and a rate of change of period2 P≃1.3×10−19. If the spin down rate is due to magnetic dipole radiation from a rotating neutron star its magnetic field is B≃5×108 G. This value is substantially lower than that of all other radio pulsars whose fields lie in the range ∼1010–1013 G with the majority having fields ≳1011 G. It has been suggested3 that 4C21.53 belongs to a class of low-magnetic-field (≪1011 G) pulsars4 which are spun up by accretion in a binary3,5. After accretion ceases such stars could become isolated radio pulsars, as in the case of 4C21.53, or binary radio pulsars depending on whether the binary has disrupted or not. Here we make the alternative and, we believe, simpler suggestion that the neutron star formed in isolation and that it essentially has its original spin and magnetic field.

Interpretation of Binary Pulsar Observations

The nature, dynamics and evolution of the three known radio pulsar binaries are discussed. The system containing 1913+16 appears to comprise two ~1.4 M⊙ components, and to undergo orbital decay as predicted by general relativity. It is proposed that 1913+16 has a neutron star companion and that 0655+64 and 0820+02 have white dwarf companions which should be observable optically.

Evidence of a disrupted pulsar binary system

THIS letter demonstrates that the pulsars PSR1952 + 29 and PSR1929 + 10 may have originated in a binary system which was disrupted by a supernova explosion less than a million years ago. If further confirmed by improved observations, this result provides an evolutionary link between the separate phenomena of X-ray binary systems and radio pulsars.

Some implications of period changes in the first binary radio pulsar

view Abstract Citations (15) References (7) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Some implications of period changes in the first binary radio pulsar. Brecher, K. Abstract The absence of a large advance of the periastron of the first binary pulsar is shown to imply that the unseen companion is also collapsed. The existence of a lower limit to the mass of the observed pulsar of about 0.3 solar mass requires a minimum general relativistic periastron advance of about 2 degress per year. Other causes of apparent and true pulse period changes are also briefly considered. Publication: The Astrophysical Journal Pub Date: February 1975 DOI: 10.1086/181722 Bibcode: 1975ApJ...195L.113B Keywords: Binary Stars; Gravitational Collapse; Periodic Variations; Pulsars; Radio Stars; Relativistic Effects; Angular Velocity; Apsides; Companion Stars; Mass Ratios; Precession; Stellar Rotation; Variable Stars; Astrophysics full text sources ADS |