Search results for "Binary pulsar"
showing 9 items of 19 documents
General relativistic effects on the evolution of binary systems.
2005
When a radio pulsar brakes down due to magnetodipole emission,its gravitational mass decreases accordingly. If the pulsar is hosted in a binary system, this mass loss will Increase the orbital period of the system. We show that this relativistic effect can be indeed observable if the neutron star is fast and magnetized enough and that, if observed, it will help to put tight constraints to the equation of state of ultradense matter. Moreover, in Low Mass X-ray Binaries that evolve towards short periods, the neutron star lights up as a radio pulsar during the "period gap". As the effect we consider contrasts the orbital period decay, the system spends a longer time in this phase. As a consequ…
Inhomogeneous Accretion Flow in X-ray Binary Pulsars
2005
We analyze the power spectrum of SAX J1808.4‐3658, the first accreting millisecond binary pulsar discovered, to look for a broadening in the wings of the harmonic line, in analogy to what had been previously found in some high mass X‐ray binaries. We indeed detect a broadening at the base of the 401 Hz peak, which is consistent with the convolution of the low frequency noise present in the power spectrum with the harmonic line. We interpret this as the result of a coupling between a fraction of the aperiodic and periodic variability, suggesting that at least part of the noise originates in a region close to the neutron star surface at the magnetic poles.
The optical counterpart of SAX J1808.4-3658 in quiescence: evidence of an active radio pulsar?
2004
Abstract The optical counterpart of the binary millisecond X-ray pulsar SAX J1808.4–3658 during quiescence was detected at V = 21.5 mag by Homer et al. [MNRAS 325 (2001) 1471]. It was proposed that the bulk of the optical emission arises from viscous dissipation in the innermost zones of a remnant disk. The serious difficulty in this scenario lies in the estimate of the irradiating luminosity required to match the observational data, that is a factor 10–50 higher than the observed quiescent X-ray luminosity of this source. To overcome this problem, we propose an alternative scenario, in which the irradiation is due to the release of rotational energy by the fast spinning neutron star, switc…
Hard X-ray emission from neutron star X-ray binaries
2004
Abstract In this paper we review our current knowledge of the hard X–ray emission properties of accreting X–ray Binary Pulsars and old accreting neutron stars in Low Mass X–ray Binaries in light of 7 years of BeppoSAX and RXTE observations. The paper is divided in two parts. In the first part we review the more recent findings on the phase-dependent broad band continua and cyclotron resonance scattering features observed in many systems of the X-ray Binary Pulsar class. In the second part we review the hard X-ray emission of LMXRB focussing on the hard X-ray components extending up to energies of a few hundred keV that have been clearly detected in sources of both the atoll and Z classes. T…
Preliminary Results on Intermittent Behaviour of Millisecond Pulsar SAX J1808.4-3658
2004
We analyzed RXTE data from the burst of the year 2000 of the X-ray millisecond binary pulsar SAX J 1808.4-3658 with the intent of determining the new orbital parameters.We used the observations of SAX J1808.4-3658 performed by the Rossi X-Ray Timing Explorer (RXTE) when the source was again detected in outburst during the period January-March 2000 (Wijnands et al. 2001). In particular we examined the data from the Proportional Counter Array (РСA) (Jahoda et al. 1996). We first applied barycentric correction to the data using the optical coordinates of the source (Roche et al. 98).
Binary evolution of PSR J1713+0747
2007
PSR J1713+0747 is a binary millisecond radio pulsar with a long orbital period (Porb ∼ 68 d) and a very low neutron star mass (M NS = 1.3 ± 0.2 M⊙). We simulate the evolution of this binary system with an accurate numerical code, which keeps into account both the evolution of the primary and of the whole binary system. We show that strong ejection of matter from the system is fundamental to obtain a mass at the end of the evolution that is within 1 - σ from the observed one, but propeller effects are almost negligible in such a system, where the accretion rate is always near to the Eddington limit. We show that there are indeed two mechanisms can account for the amount of mass loss from the…
An eclipsing millisecond pulsar in the globular cluster Terzan 5
1990
WE HAVE discovered an eclipsing binary millisecond pulsar in the globular cluster Terzan 5. This, the second known eclipsing binary pulsar after PSR1957 + 20, has a pulse period of 11.56 ms and a very short orbital period of 1.8 hours. In contrast to PSR1957 + 20, where the eclipses occupy about 10 per cent of the orbital period1, the eclipse duration in this pulsar is very variable and never less than one-third of the orbital period. The pulsar is in a circular orbit of radius 0.11 light seconds, which implies a minimum companion mass of 0.089 solar masses, about four times the companion mass of PSR1957 + 20. Timing observations suggest an identification of the pulsar with a variable conti…
The contribution of the Italian Northern Cross Radiotelescope to the Gamma-Ray Observatory Pulsar Timing Network
1992
The observation of pulsars at gamma-ray energy requires updated pulsar parameters in order to fold the gamma-ray data over time intervals of weeks. The Compton Gamma-Ray Observatory Institute has set up an international agreement including several radiotelescopes and pulsar observers in order to provide a suitable timing support at radio wavelengths. In this paper we describe the system used at the Italian Northern Cross for the pulse timing observations related to the GRO mission.
Timing an Accreting Millisecond Pulsar: Measuring the Accretion Torque in IGR J00291+5934
2006
We performed a timing analysis of the fastest accreting millisecond pulsar IGR J00291+5934 using RXTE data taken during the outburst of December 2004. We corrected the arrival times of all the events for the orbital (Doppler) effects and performed a timing analysis of the resulting phase delays. In this way we have the possibility to study, for the first time in this class of sources, the spin-up of a millisecond pulsar as a consequence of accretion torques during the X-ray outburst. The accretion torque gives us for the first time an independent estimate of the mass accretion rate onto the neutron star, which can be compared with the observed X-ray luminosity. We also report a revised valu…