scholarly journals Monte Carlo Simulations of Radio Pulsars and Their Progenitors

1987 ◽  
Vol 125 ◽  
pp. 408-408
Author(s):  
Rachel J. Dewey ◽  
James M. Cordes
Keyword(s):  
Neutron Star ◽  
Velocity Distribution ◽  
Neutron Stars ◽  
Binary Systems ◽  
Stellar Population ◽  
Main Sequence ◽  
Radio Pulsar ◽  
Close Binary ◽  
Radio Pulsars ◽  
Binary Pulsars

The formation of neutron stars in binary systems is often used to explain the nature of specific radio pulsars and characteristics of the pulsar population as a whole. We have investigated the extent to which such scenarios provide a self-consistent description of the pulsar population. Using a computer simulation, we modeled the evolution of the main sequence stellar population and compared the predicted neutron star population to the observed radio pulsar population, focusing our attention on the pulsar velocity distribution and the incidence of binary pulsars. These characteristics relate very directly to the binary nature of pulsar progenitors, and are not strongly dependent on models of pulsar magentic field and luminosity evolution.The need to reproduce both the high velocities typical of pulsars and the low incidence of binary pulsars strongly constrains the formation of pulsars in binary systems. Unless one assumes that virtually all pulsars originate in close binary systems, the observed velocity distribution cannot result from the disruption of binary systems by symmetric supernova explosions; some additional acceleration process (e.g. asymmetric supernova mass ejection or asymmetries in pulsar radiation) must act during or soon after a pulsar's formation. It is possible to reproduce the velocity distribution by assuming that all pulsars are born in binary systems with initial orbital periods less than about 30 years. However, the predicted incidence of binaries is then too large by more than an order of magnitude, unless one also assumes that the process of mass transfer from the primary to the secondary is almost always non-conservative, or that the minimum mass necessary for a stripped helium core to explode as a supernova is larger (over 4 M⊙) than currently believed. Further analyses of the radio pulsar population, the X-ray binary population and the abundances of elements ejected in supernovae should help determine which of these alternatives is most reasonble. Additional studies of the main sequence stellar population, accounting more accurately for evolutionary and observational selection effects, will reduce the uncertainties in modeling the formation of the neutron star population.It has also been suggested that the observed correlation between pulsar velocities and magnetic moments (see Cordes, these Proceedings) is induced by the differing evolutionary paths by which stars in binary systems form radio pulsars. Our simulation does not reproduce this correlation, and we do not find any paths likely to produce low velocity, low magnetic field neutron stars not in binary systems.We are submitting a full description of our model and results to The Astrophysical Journal.

Do neutron stars produce jets?

1986 ◽  
Vol 64 (4) ◽  
pp. 474-478 ◽  
Author(s):  
Eric D. Feigelson
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Supernova Remnants ◽  
Binary Systems ◽  
Crab Nebula ◽  
Compact Object ◽  
Radio Pulsars ◽  
X Ray ◽  
The Crab Nebula ◽  
X Ray Binaries

The evidence for jets emanating from neutron stars is reviewed. Isolated radio pulsars do not appear to produce collimated outflows. A few supernova remnants, notably the Crab nebula, exhibit jetlike protrusions at their outer boundaries. These are probably "blowouts" of the plasma in the remnant rather than true jets from a neutron star. However, several cases of degenerate stars in X-ray binary systems do make jets. SS433 has twin precessing jets moving outward at v ~ 0.26c, and Sco X-1 has radio lobes with v ~ 0.0001c. Cyg X-3 appears to eject synchrotron plasmoids at high velocities. Other X-ray binaries associated with variable radio sources are discussed; some are interesting candidates for collimated outflow. G109.1-1.0 is an X-ray binary in a supernova remnant that may have radio or X-ray jets. It is not clear in all these cases, however, that the compact object is a neutron star and not a black hole or white dwarf.A tentative conclusion is reached that isolated neutron stars do not produce jets, but degenerate stars in accreting binary systems can. This suggests that the presence of an accretion disk, rather than the characteristics of an isolated pulsar's dipole magnetosphere, is critical in making collimated outflows.

scholarly journals Interstellar Scintillations and Neutron Star Kinematics

1987 ◽  
Vol 125 ◽  
pp. 35-46
Author(s):  
J.M. Cordes
Keyword(s):  
Monte Carlo ◽  
Neutron Star ◽  
Neutron Stars ◽  
Binary Systems ◽  
Galactic Plane ◽  
Radio Pulsars ◽  
Population Monte Carlo ◽  
Interstellar Scintillation ◽  
Supernova Explosions ◽  
The Mean

The interstellar scintillation technique for measuring neutron star speeds is described and results are given for 71 radio pulsars. The mean transverse neutron star speed is 100 km s−1 and the distribution extends to 300 km s−1. The transverse speed correlates with the z velocity derived independently using distance from the galactic plane, consistent with most neutron stars having been born near the galactic plane. A correlation of transverse speed with the quantity PP ∝ (magnetic moment)2 is a general property of the neutron star population. Monte Carlo simulations of the progenitors of neutron stars show that the velocity distribution is inconsistent with the disruption of binary systems solely by symmetric supernova explosions. Either explosions are asymmetric or there are additional accelerations of neutron stars after their formation.

scholarly journals Commission 42: Close Binary Stars: (Etoiles Doubles Serrees)

2000 ◽  
Vol 24 (1) ◽  
pp. 259-276
Author(s):  
Edward F. Guinan ◽  
P. Szkody ◽  
M. Rodono ◽  
L. Bianchi ◽  
J.V. Clausen ◽  
...  
Keyword(s):  
Black Holes ◽  
Neutron Stars ◽  
Binary Stars ◽  
Binary Systems ◽  
Main Sequence ◽  
Magellanic Clouds ◽  
Giant Planets ◽  
Close Binary ◽  
Main Sequence Stars ◽  
Close Binary Stars

This is the last triennial report of Commission 42 for this millennium. A great deal has been accomplished in the study of Close Binary Stars (CBS) since the discovery of the first close (eclipsing) binary, Algol, in 1783 by John Goodricke. Now, over 10,000 CBS (most eclipsing variables) are known. More than 5000 of these CBS were discovered over the last several years alone! And many more are expected to be detected over the next few years. Most of these stars were found as spin-offs of microlensing surveys. Interestingly, nearly half of these stars are found outside our Galaxy, primarily in the Magellanic Clouds and M31. Every type of star is represented as a member of a close binary. These include main sequence (as well as pre-main sequence) stars, giants, and supergiants, with the entire possible range of of spectral types and masses represented. Moreover, “dying” stars and “dead” stars, such as white dwarfs, neutron stars, black holes, and, more recently, even brown dwarfs and giant planets (e.g., 51 Peg) have been found as members of close binary systems.

scholarly journals Some Constraints on Neutron Star Properties from Gamma Ray Burster Observations

1987 ◽  
Vol 125 ◽  
pp. 489-500
Author(s):  
K. Hurley
Keyword(s):  
Neutron Star ◽  
Low Temperature ◽  
Neutron Stars ◽  
Binary Systems ◽  
Main Sequence ◽  
Gamma Ray ◽  
Cooling Curves ◽  
X Ray ◽  
Upper Limits ◽  
Low Mass

The results of recent soft X-ray and optical searches for quiescent gamma ray burster counterparts are used to constrain the properties of the neutron stars responsible for bursters. Ages are restricted to the range 2×105 y and above based on temperature upper limits and theoretical cooling curves, or 107 y and above if bursters have evolved from pulsars. Velocities are greater than 20 km/s if the neutron stars are unmagnetized. Practically no main sequence star could have escaped detection in the optical/IR searches, so if the neutron stars are in binary systems, the companion is most likely a degenerate, low mass, low temperature object.

scholarly journals Binary Pulsars: Observations and Implications

1987 ◽  
Vol 125 ◽  
pp. 383-392
Author(s):  
J. H. Taylor
Keyword(s):  
Neutron Stars ◽  
Binary Systems ◽  
Radio Pulsars ◽  
X Ray ◽  
Orbital Parameters ◽  
Binary Pulsars ◽  
Essential Parameter ◽  
Timing Data ◽  
The Galaxy ◽  
Pulse Timing

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.

scholarly journals Masses of Neutron Stars in X-ray Binary Systems

1981 ◽  
Vol 95 ◽  
pp. 353-356
Author(s):  
R. L. Kelley ◽  
S. Rappaport
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Binary Systems ◽  
Radio Pulsars ◽  
X Ray ◽  
The Masses

The masses of 6 neutron stars have now been established through studies of binary X-ray and radio pulsars. All of the masses are found to be consistent with, but not necessarily constrained to, the range 1.2–1.6 M⊙. In this talk we discuss the methods and assumptions used in determining the masses of neutron stars in binary X-ray pulsar systems. For other recent reviews of this subject, the reader is referred to Bahcall (1978), Rappaport and Joss (1981), and references therein. Neutron-star parameters may also be obtained from studies of X-ray bursts that result from thermonuclear flashes near the surface of an accreting neutron star (see Joss 1980 and references therein), which we will not discuss here.

scholarly journals V392 Orionis: Observations and Evolutionary State of a Low-Mass System

1998 ◽  
Vol 11 (1) ◽  
pp. 371-371
Author(s):  
S. Narusawa ◽  
A. Yamasaki ◽  
Y. Nakamura
Keyword(s):  
Binary Systems ◽  
Main Sequence ◽  
Circumstellar Matter ◽  
Small Mass ◽  
Primary Component ◽  
Close Binary ◽  
Mass System ◽  
Future Evolution ◽  
Short Period ◽  
Low Mass

Although the evolution of binary systems has been qualitatively interpreted with the evolutionary scenario, the quantitative interpretation of any observed system is still unsatisfactory due to the difficulty of the quantitative treatment of mass and angular momentum transfer/loss. To reach a true understanding of the evolution of binary systems, we have to accumulate more observational evidence. So far, we have observed several binaries that are short-period and noncontact, and found the existence of extremely small-mass systems. In the present paper, we study another short-period (P=0.659d), noncontact, eclipsing binary system, V392 Ori. We have made photometric and spectroscopic observations of V392 Ori. The light curves are found to vary, suggesting the existence of circumstellar matter around the system. Combining the photometric and spectroscopic results, we obtain parameters describing the system; we find the mass of the primary component is only 0.6Mʘ- undermassive for its spectral and luminosity class A5V, suggesting that a considerable amount of its original mass has been lost from the system during the course of evolution. The low-mass problem is very important for investigation of the evolution of close binary systems: largemass loss within and/or after the main-sequence will have a significant influence on the future evolution of binary systems.

scholarly journals Empirical Determination of the Gravity-Darkening Exponent for the Secondary Components Filling the Roche Lobe in Semi-Detached Close Binary Systems

1988 ◽  
Vol 108 ◽  
pp. 217-218
Author(s):  
Masatoshi Kitamura ◽  
Yasuhisa Nakamura
Keyword(s):  
Binary Systems ◽  
Main Sequence ◽  
Close Binary System ◽  
Roche Lobe ◽  
Close Binary ◽  
Close Binaries ◽  
Main Sequence Stars ◽  
Local Gravity ◽  
Subsurface Layers

The ordinary semi-detached close binary system consists of a main-sequence primary and subgiant (or giant) secondary component where the latter fills the Roche lobe. From a quantitative analysis of the observed ellipticity effect, Kitamura and Nakamura (1986) have deduced empirical values of the exponent of gravity-darkening for distorted main-sequence stars in detached systems and found that the empirical values of the exponent for these stars with early-type spectra are close to the unity, indicating that the subsurface layers of early-main sequence stars in close binaries are actually in radiative equilibrium. The exponent of gravity-darkening can be defined by H ∝ gα with H as the bolonetric surface brightness and g as the local gravity on the stellar surface.

scholarly journals The Galactic Pulsar Population and Neutron Star Birth

1987 ◽  
Vol 125 ◽  
pp. 67-78
Author(s):  
Ramesh Narayan
Keyword(s):  
Angular Momentum ◽  
Neutron Star ◽  
Binary Systems ◽  
Magnetic Coupling ◽  
Scale Height ◽  
High Magnetic Fields ◽  
Radio Pulsars ◽  
X Ray ◽  
The Galaxy ◽  
Low Mass

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.

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