scholarly journals Impact of accretion on the statistics of neutron star masses

2012 ◽  
Vol 8 (S290) ◽  
pp. 195-196
Author(s):  
Z. Cheng ◽  
A. Taani ◽  
Y. H. Zhao
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Neutron Star ◽  
Neutron Stars ◽  
Binary Systems ◽  
Gaussian Function ◽  
Recycling Process ◽  
Mass Distributions ◽  
Spin Period ◽  
Boot Strap

AbstractWe have collected the parameter of 38 neutron stars (NSs) in binary systems with spin periods and measured masses. By adopting the Boot-strap method, we reproduced the procedure of mass calculated for each system separately, to determine the truly mass distribution of the NS that obtained from observation. We also applied the Monte-Carlo simulation and introduce the characteristic spin period 20 ms, in order to distinguish between millisecond pulsars (MSPs) and less recycled pulsars. The mass distributions of MSPs and the less recycled pulsars could be fitted by a Gaussian function as 1.45±0.42 M⊙ and 1.31±0.17 M⊙ (with 1σ) respectively. As such, the MSP masses are heavier than those in less recycled systems by factor of ~ 0.13M⊙, since the accretion effect during the recycling process.

MONTE CARLO SIMULATION OF NEUTRON STAR MASSES

2013 ◽  
Vol 23 ◽  
pp. 157-160
Author(s):  
ZHENG CHENG ◽  
CHENGMIN ZHANG ◽  
ALI TAANI
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Neutron Star ◽  
Confidence Level ◽  
White Dwarfs ◽  
Binary Systems ◽  
The Other ◽  
Radio Pulsars ◽  
Millisecond Pulsars ◽  
Spin Period

We perform a Monte Carlo simulation to investigate the distribution and evolution of 66 mass measured pulsars. We get the best fits to the distribution at 1.35 ± 0.27M⨀ (1σ confidence level). In addition, we notice bimodal distributions in 1.34 ± 0.15M⨀ and 1.48 ± 0.53M⨀, this can be led to the idea that radio pulsars in binary systems have recycled. Thus we divide the data according to the characteristic spin period into two groups, millisecond pulsars (MSPs), P Spin ≤ 20 ms and less recycled pulsars P Spin ≥ 20 ms , respectively. We show that the distributions of MSPs at 1.42 ± 0.36M⨀, and 1.32 ± 0.18M⨀ for less recycled pulsars. As such, the mass of MSPs are heavier than those in less recycled pulsars by ~ 0.1M⨀, since they accreting material from their companions. On the other hand, the formation of heavier pulsars from the accretion induced collapse of accreting white dwarfs, must be invoked.

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 The Effects of Transition Time on the Populations of Post-AGB Stars, and on the Nebular Evolution

2003 ◽  
Vol 209 ◽  
pp. 133-134
Author(s):  
Eva Villaver ◽  
Letizia Stanghellini ◽  
Arturo Manchado ◽  
Guillermo García-Segura ◽  
Alvio Renzini
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Planetary Nebula ◽  
Time Lag ◽  
Dynamical Evolution ◽  
Transition Time ◽  
Agb Stars ◽  
Core Mass ◽  
Mass Distributions ◽  
Pn Stage

We show how the different assumptions on the transition time (the time lag between the superwind quenching at the AGB and the illumination of the Planetary Nebula [PN]) reflect into very different theoretical outcomes, both in the characteristics of the stellar remnants, and in the evolution of the nebular shells.We use a Monte Carlo simulation of post-AGB stars with a set of assumptions on the transition time, to show the effect on the resulting location of the stars on the HR diagram, and on the derived core mass distributions.We have also performed numerical simulations of the PN formation process, and investigated the effects of the transition time on the resulting PN structure. We found that the transition time determines not only the size of the PN shell, but also its dynamical evolution.We show the important implications that the transition time has on the observable parameters during the PN stage.

Monte-Carlo simulation of regular lamellar eutectic growth in binary systems

2002 ◽  
Vol 336 (1-2) ◽  
pp. 129-134
Author(s):  
Wei-Min Wang ◽  
J.-M. Liu ◽  
X.M. Pan ◽  
Zhiguo Liu
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Binary Systems ◽  
Eutectic Growth ◽  
Lamellar Eutectic

PULSAR DISTRIBUTIONS IN THE MAGNETIC AND SPIN PERIOD DIAGRAM

2013 ◽  
Vol 23 ◽  
pp. 165-169
Author(s):  
CHENGMIN ZHANG ◽  
YUANYUE PAN ◽  
ALI TAANI
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Stellar Evolution ◽  
Distribution Characteristics ◽  
Radio Pulsars ◽  
X Ray ◽  
Spin Period

The various types of pulsars are classified in the magnetic and spin period (B-P) diagram, by which one can recognize their properties there. We also investigate the relation of radio pulsars and X-ray neutron stars, and their distribution characteristics, implying their evolution links. B-P diagram is divided by the special lines, e.g. spin-up line and "death line", which indicate the evolution information of pulsars. Like Hertzsprung-Russell (H-R) diagram of showing the stellar evolution or "lives of stars", we try to develop B-P diagram as a function of representing the evolution track of neutron star.

scholarly journals Beaming Due to Comptonisation in X-ray Pulsars

2000 ◽  
Vol 177 ◽  
pp. 435-436
Author(s):  
D.K. Galloway ◽  
K. Wu
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Neutron Star ◽  
X Ray ◽  
Beam Patterns

AbstractComptonisation may play an important role in determining beam patterns and hence pulse profiles in X-ray pulsars. We describe a Monte Carlo simulation used to investigate the spectra and pulse profiles emitted by two semi-infinite homogeneous cyclindrical accretion columns diametrically located on the surface of a ‘canonical’ neutron star.

scholarly journals Orbital and superorbital periods in ULX pulsars, disc-fed HMXBs, Be/X-ray binaries, and double-periodic variables

2020 ◽  
Vol 495 (1) ◽  
pp. L139-L143
Author(s):  
L J Townsend ◽  
P A Charles
Keyword(s):  
Neutron Star ◽  
Orbital Period ◽  
Binary Systems ◽  
High Mass ◽  
Early Type ◽  
Present Evidence ◽  
X Ray ◽  
Spin Period ◽  
Simple Linear Relationship ◽  
X Ray Binaries

ABSTRACT We present evidence for a simple linear relationship between the orbital period and superorbital period in ultra-luminous X-ray (ULX) pulsars, akin to what is seen in the population of disc-fed neutron star supergiant X-ray binary and Be/X-ray binary systems. We argue that the most likely cause of this relationship is the modulation of precessing hotspots or density waves in an accretion or circumstellar disc by the binary motion of the system, implying a physical link between ULX pulsars and high-mass X-ray binary (HMXB) pulsars. This hypothesis is supported by recent studies of Galactic and Magellanic Cloud HMXBs accreting at super-Eddington rates, and the position of ULX pulsars on the spin period–orbital period diagram of HMXBs. An interesting secondary relationship discovered in this work is the apparent connection between disc-fed HMXBs, ULXs, and a seemingly unrelated group of early-type binaries showing so-called double-periodic variability. We suggest that these systems are good candidates to be the direct progenitors of Be/X-ray binaries.

GATE MODELING OF LATERAL SCATTERING OF PROTON PENCIL BEAMS

2020 ◽  
Vol 189 (1) ◽  
pp. 76-88
Author(s):  
Shiva Zarifi ◽  
Hadi Taleshi Ahangari ◽  
Sayyed Bijan Jia ◽  
Mohammad Ali Tajik-Mansoury ◽  
Milad Najafzadeh
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Energy Range ◽  
Ionization Potential ◽  
Gaussian Function ◽  
Gaussian Model ◽  
Absorbed Dose ◽  
Body Tissue ◽  
Simulation Code ◽  
Optimal Value

Abstract To validate the GATE Monte Carlo simulation code and to investigate the lateral scattering of proton pencil beams in the major body tissue elements in the therapeutic energy range. In this study, GATE Monte Carlo simulation code was used to compute absorbed dose and fluence of protons in a water cubic phantom for the clinical energy range. To apply the suitable physics model for simulation, different physics lists were investigated. The present research also investigated the optimal value of the water ionization potential as a simulation parameter. Thereafter, the lateral beam profile of proton pencil beams were simulated at different energies and depths in body tissue elements. The range results obtained using the QGSP_BIC_EMY physics showed the best compatibility with the NIST database data. Moreover, it was found that the 76 eV is the optimal value for the water ionization potential. In the next step, it was shown that the beam halo can be described by adding a supplementary Gaussian function to the standard single-Gaussian model, which currently is used by treatment planning systems (TPS).

scholarly journals The superslow pulsation X-ray pulsars in high mass X-ray binaries

2012 ◽  
Vol 8 (S291) ◽  
pp. 203-206 ◽  
Author(s):  
Wei Wang
Keyword(s):  
Neutron Star ◽  
Binary Systems ◽  
High Mass ◽  
X Ray ◽  
Origin And Evolution ◽  
Surface Magnetic Field ◽  
Spin Period ◽  
Binary Evolution ◽  
X Ray Binaries

AbstractThere exists a special class of X-ray pulsars that exhibit very slow pulsation of Pspin > 1000 s in the high mass X-ray binaries (HMXBs). We have studied the temporal and spectral properties of these superslow pulsation neutron star binaries in hard X-ray bands with INTEGRAL observations. Long-term monitoring observations find spin period evolution of two sources: spin-down trend for 4U 2206+54 (Pspin ~ 5560 s with Ṗspin ~ 4.9 × 10−7 s s−1) and long-term spin-up trend for 2S 0114+65 (Pspin ~ 9600 s with Ṗspin ~ −1 × 10−6 s s−1) in the last 20 years. A Be X-ray transient, SXP 1062 (Pspin ~ 1062 s), also showed a fast spin-down rate of Ṗspin ~ 3 × 10−6 s s−1 during an outburst. These superslow pulsation neutron stars cannot be produced in the standard X-ray binary evolution model unless the neutron star has a much stronger surface magnetic field (B > 1014 G). The physical origin of the superslow spin period is still unclear. The possible origin and evolution channels of the superslow pulsation X-ray pulsars are discussed. Superslow pulsation X-ray pulsars could be younger X-ray binary systems, still in the fast evolution phase preceding the final equilibrium state. Alternatively, they could be a new class of neutron star system – accreting magnetars.

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