Query : 2000A&A...353..641N

2000A&A...353..641N - Astronomy and Astrophysics, volume 353, 641-645 (2000/1-2)

Stable ultracompact objects and an upper bound on neutron star masses.


Abstract (from CDS):

We have proposed a core-envelope model with stiffest equation of state [speed of sound equal to that of light] in the core and a polytropic equation with constant adiabatic index Γ1=[dlnP/dln ρ] in the envelope and obtained a stable configuration with a maximum value of u≃0.3574 when the ratio of pressure to density at the core-envelope boundary reaches about 0.014. The maximum mass of neutron star based upon this model comes out to be 7.944M, if the (average) density of the configuration is constrained by fastest rotating pulsar, with rotation period, Prot≃1.558ms, known to date. The average density of the configuration turns out to be 1.072x1014g/cm3. The model gives dynamically stable configurations with compaction parameter u [=(M/R), where M = mass and R = radius of the structure] > (1/3) which are important to study Ultra-Compact Objects [UCOs]. The theoretically obtained maximum value of u is also important regarding millisecond oscillations seen during X-Ray burst (if they are produced due to spin modulation) from a rotating neutron star, because the maximum modulation amplitude depends only upon the compaction parameter and the observed value of this amplitude provides a tool for testing theoretical models of neutron stars. The M(envelope)/M(star) ratio corresponds to a value ∼10–2 which may be relevant in explaining the rotational irregularities in pulsars known as the timing noise and glitches.

Abstract Copyright:

Journal keyword(s): dense matter - equation of state - stars: neutron

Simbad objects: 3

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Number of rows : 3
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
1 PSR B1937+21 Psr 19 39 39.6 +21 37 22           ~ 1013 2
2 HD 226868 HXB 19 58 21.6757355952 +35 12 05.784512688 9.38 9.72 8.91 8.42   O9.7Iabpvar 4092 0
3 PSR J1959+2048 Psr 19 59 36.7480 +20 48 14.599   20.4       ~ 745 2

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