scholarly journals Pulsars in Globular Clusters

2007 ◽  
Vol 3 (S246) ◽  
pp. 291-300 ◽  
Author(s):  
Scott M. Ransom
Keyword(s):  
Equation Of State ◽  
Neutron Stars ◽  
Globular Clusters ◽  
Main Sequence ◽  
Galactic Disk ◽  
Nuclear Density ◽  
Millisecond Pulsars ◽  
Eccentric Orbits ◽  
The Masses ◽  
Current Record

AbstractGlobular clusters produce orders of magnitude more millisecond pulsars per unit mass than the Galactic disk. Since the first cluster pulsar was uncovered 20 years ago, at least 138 have been identified – most of which are binary millisecond pulsars. Because their origins involve stellar encounters, many of the systems are exotic objects that would never be observed in the Galactic disk. Examples include pulsar-main sequence binaries, extremely rapid rotators (including the current record holder), and millisecond pulsars in highly eccentric orbits. These systems are allowing new probes of the interstellar medium, the equation of state of material at supra-nuclear density, the masses of neutron stars, and globular cluster dynamics.

scholarly journals Chemically Peculiar Stars Among Spectroscopic Binaries – Revisited

1993 ◽  
Vol 138 ◽  
pp. 137-142 ◽  
Author(s):  
Wilhelm Seggewiss
Keyword(s):  
Relative Frequency ◽  
Main Sequence ◽  
Statistical Investigation ◽  
Spectroscopic Binaries ◽  
Main Sequence Stars ◽  
Eccentric Orbits ◽  
Peculiar Stars ◽  
Orbital Periods ◽  
Chemically Peculiar Stars ◽  
The Masses

AbstractThis paper presents a new statistical investigation of peculiar A-type stars (Am, Ap, Hg-Mn) among spectroscopic binary (SB) stars. The relative frequency of Am (CP 1) stars is 55% in the spectral range A1 to A6 of main-sequence stars. The Ap (CP 2) stars amount to 15% in the range B9 to A2. The Hg-Mn stars are concentrated to the spectral types B8 to AO and reach a relative frequency of 23%. The Am SB stars have the shortest orbital periods and the smallest eccentricities (30% circular) whereas the Ap SB stars show a strong tendency to long periods and highly eccentric orbits (only 10% circular). The masses of the Am stars agree with the masses of non-peculiar SB stars of corresponding spectral type.

NEUTRON STARS AND THE COHERENT NUCLEAR INTERACTION

1995 ◽  
Vol 04 (04) ◽  
pp. 531-548 ◽  
Author(s):  
E. DEL GIUDICE ◽  
R. MELE ◽  
G. PREPARATA ◽  
C. GUALDI ◽  
G. MANGANO ◽  
...  
Keyword(s):  
Equation Of State ◽  
Neutron Stars ◽  
Nuclear Interaction ◽  
Central Density ◽  
Maximum Mass ◽  
Minimum Period ◽  
Novel Approach ◽  
Coherent Interaction ◽  
New Equation ◽  
The Masses

In the framework of a novel approach to the dynamics of nuclei and large collections of nucleons, which fully exploits the coherent interaction among π’s, nucleons and Δ’s, we derive a new equation of state for neutronic matter. By introducing it in the Tolman-Oppenheimer-Volkof equations we derive the masses and radii of neutron stars as a function of the central density. We obtain a maximum mass Mmax≃2.7 Mʘ and a minimum period of rotation Tmin=0.8 msec.

scholarly journals Recycled pulsars with multipolar magnetospheres from accretion-induced magnetic burial

2020 ◽  
Vol 499 (3) ◽  
pp. 3243-3254
Author(s):  
A G Suvorov ◽  
A Melatos
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Equation Of State ◽  
Neutron Stars ◽  
Field Line ◽  
Dipole Field ◽  
Multipole Moments ◽  
Millisecond Pulsars ◽  
The Magnetic Field ◽  
Field Strengths

ABSTRACT Many millisecond pulsars are thought to be old neutron stars spun up (‘recycled’) during an earlier accretion phase. They typically have relatively weak (≲109 G) dipole field strengths, consistent with accretion-induced magnetic burial. Recent data from the Neutron Star Interior Composition Explorer indicate that hotspots atop the recycled pulsar PSR J0030–0451 are not antipodal, so that the magnetic field cannot be that of a centred dipole. In this paper it is shown that multipolarity is naturally expected in the burial scenario because of equatorial field line compression. Grad–Shafranov equilibria are constructed to show how magnetic multipole moments can be calculated in terms of various properties, such as the amount of accreted mass and the crustal equation of state.

scholarly journals Coulomb Corrections and Globular Cluster Stellar Evolution

1993 ◽  
Vol 137 ◽  
pp. 451-453 ◽  
Author(s):  
Charles R. Proffitt
Keyword(s):  
Equation Of State ◽  
Stellar Evolution ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Main Sequence ◽  
Stellar Interior ◽  
Coulomb Effects

AbstractThe effects of Coulomb corrections on the evolution of globular clusters stars are discussed. Coulomb corrections alter the equation of state by about 1% in most of the stellar interior, and for stars of fixed initial parameters, this results in an 8% increase in the ZAMS luminosity and an 8% decrease in the age at the main sequence turnoff. Ages for globular clusters measured by comparing to the turnoff luminosity of theoretical isochrones are lowered by ≈ 4% when Coulomb effects are included.

scholarly journals Eight new millisecond pulsars from the first MeerKAT globular cluster census

2021 ◽  
Vol 504 (1) ◽  
pp. 1407-1426
Author(s):  
A Ridolfi ◽  
T Gautam ◽  
P C C Freire ◽  
S M Ransom ◽  
S J Buchner ◽  
...  
Keyword(s):  
Neutron Stars ◽  
Total Mass ◽  
Globular Clusters ◽  
The Other ◽  
Telescope Array ◽  
Millisecond Pulsars ◽  
The Core ◽  
Binary Pulsars ◽  
Low Mass ◽  
Large Eccentricity

ABSTRACT We have used the central 44 antennas of the new 64-dish MeerKAT radio telescope array to conduct a deep search for new pulsars in the core of nine globular clusters (GCs). This has led to the discovery of eight new millisecond pulsars in six different clusters. Two new binaries, 47 Tuc ac and 47 Tuc ad, are eclipsing ‘spiders’, featuring compact orbits (≲0.32 d), very low mass companions, and regular occultations of their pulsed emission. The other three new binary pulsars (NGC 6624G, M62G, and Ter 5 an) are in wider (>0.7 d) orbits, with companions that are likely to be white dwarfs or neutron stars. NGC 6624G has a large eccentricity of e ≃ 0.38, which enabled us to detect the rate of advance of periastron. This suggests that the system is massive, with a total mass of Mtot = 2.65 ± 0.07 M⊙. Likewise, for Ter 5 an, with e ≃ 0.0066, we obtain Mtot = 2.97 ± 0.52 M⊙. The other three new discoveries (NGC 6522D, NGC 6624H, and NGC 6752F) are faint isolated pulsars. Finally, we have used the whole MeerKAT array and synthesized 288 beams, covering an area of ∼2 arcmin in radius around the centre of NGC 6624. This has allowed us to localize many of the pulsars in the cluster, demonstrating the beamforming capabilities of the TRAPUM software backend and paving the way for the upcoming MeerKAT GC pulsar survey.

scholarly journals Neutron stars with hyperon cores: stellar radii and equation of state near nuclear density

2015 ◽  
Vol 576 ◽  
pp. A68 ◽  
Author(s):  
M. Fortin ◽  
J. L. Zdunik ◽  
P. Haensel ◽  
M. Bejger
Keyword(s):  
Equation Of State ◽  
Neutron Stars ◽  
Nuclear Density

scholarly journals The Formation and Evolution of Binaries in Globular Clusters

1989 ◽  
Vol 8 ◽  
pp. 139-142
Author(s):  
Frank Verbunt
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Galactic Disk ◽  
Main Sequence Star ◽  
Number Density ◽  
X Ray ◽  
Close Encounters ◽  
Low Mass ◽  
Formation And Evolution ◽  
X Ray Binaries

AbstractThe number density of stars in the cores of globular clusters is high enough for close encounters between stars to be frequent. These encounters may lead to the formation of binaries. Those binaries which do not easily form via the evolution of primordial main-sequence star binaries, and are therefore rare in the galactic disk, can be common in globular clusters. Examples of such binaries are the low-mass X-ray binaries. Such binaries may evolve into radiopulsars.

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