Double Pulsar PSR J0737-3039A Research Articles

Stringent pulsar timing bounds on light scalar couplings to matter

Pulsar Timing constraints on scalar-tensor theories with conformal and disformal couplings to matter are discussed. Reducing the dynamics to the motion in the centre of mass frame and using the mean anomaly parametrisation, we find the first post-Newtonian corrections induced by the conformal and disformal interactions in the form of a generalized quasi-Keplerian solution. We also derive the radiation reaction force due to scalar radiation and the corresponding Post-Keplerian Parameters (PKP). We use different pulsar time of arrival (TOA) data sets to probe the scalar corrections to the PKP. In particular, we focus on systems with large orbital frequencies as the contributions to the PKP terms induced by the disformal coupling are sensitive to higher frequencies. We find that the most constraining { {pulsar timings}} are PSR B1913+16 and the double pulsar PSR J0737-3039A/B, being {{of the order of}} the Cassini bound on the conformal coupling obtained from the Shapiro effect in the solar system. { {The combined constraints using other pulsar timings give an upper bound on the conformal coupling $\beta^2 < 2.33 \cdot 10^{-5}$ and a lower bound on the disformal coupling scale of $\Lambda \geq 1.12 \ {\rm MeV}$ which is comparable to the Cassini bound and to the GW-170817 constraints respectively}}. Future measurements for pulsar timing with black hole companions are also discussed.

Constraints on Estimation of Radius of Double Pulsar PSR J0737-3039A and Its Neutron Star Nuclear Matter Composition**Supported by the National Program on Key Research and Development Project under Grant No 2016YFA0400801, the National Natural Science Foundation of China under Grant Nos 11173034, 11673023 and 11364007, the Fundamental Research Funds for the Central University, the Key Support Disciplines of Theoretical Physics

The aspect of formation and evolution of the recycled pulsar (PSR J0737-3039 A/B) is investigated, taking into account the contributions of accretion rate, radius and spin-evolution diagram (B–P diagram) in the double pulsar system. Accepting the spin-down age as a rough estimate (or often an upper limit) of the true age of the neutron star, we also impose the restrictions on the radius of this system. We calculate the radius of the recycled pulsar PSR J0737-3039 A ranges approximately from 8.14 to 25.74 km, and the composition of its neutron star nuclear matters is discussed in the mass-radius diagram.

GLOBAL PROPERTIES OF ROTATING NEUTRON STARS WITH QCD EQUATIONS OF STATE

ABSTRACT We numerically investigate global properties of rotating neutron stars (NSs) using the allowed band of QCD equations of state derived by Kurkela et al. This band is constrained by chiral effective theory at low densities and perturbative QCD at high densities, and is thus, in essence, a controlled constraint from first-principles physics. Previously, this band of equations of state was used to investigate non-rotating NSs only; in this work, we extend these results to any rotation frequency below the mass-shedding limit. We investigate mass–radius curves, allowed mass–frequency regions, radius–frequency curves for a typical star, and the values of the moment of inertia of the double pulsar PSR J0737-3039A, a pulsar for which the moment of inertia may be constrained observationally in a few years. We present limits on observational data coming from these constraints, and identify values of observationally relevant parameters that would further constrain the allowed region for the QCD equation of state. We also discuss how much this region would be constrained by a measurement of the moment of inertia of the double pulsar PSR J0737-3039A.

Testing the rotating lighthouse model with the double pulsar system PSR J0737-3039A/B

Each of the two pulsars in the double pulsar PSR J0737-3039A/B system exhibits not only the pulses emanating from itself, but also displays modulations near the pulse period of the other. Freire et al. (2009, MNRAS, 396, 1764) have put forward a technique using the modulation of B by A to determine the sense of rotation of pulsar A relative to its orbital motion, among other quantities. In this paper, we present another technique with the same purpose. While the Freire et al. approach analyzes pulse arrival times, ours instead uses periods or frequencies (their inverses), which can be experimentally determined via power spectral analysis similar to that used in pulsar searches. Our technique is based on the apparent change in spin period of a body when it is measured from an orbiting platform (the other pulsar), and is shown to be entirely analogous to the difference between the sidereal and solar spin period of the Earth (i.e., the sidereal and solar day). Two benefits of this approach are its conceptual and computational simplicity. The direct detection of spin with this technique will observationally validate the rotating lighthouse model of pulsar emission, while the detection of the relative directions of spin and orbital angular momenta has important evolutionary implications. Our technique can be used on other binary systems exhibiting mutually induced phenomena.

Revisiting the border between Newtonian mechanics and General Relativity: The periastron advance

The problem of periastron advance, which is the basis of one of the three classical tests of relativity theory, is revised with respect to both Newtonian mechanics and General Relativity and updated in the light of recent astronomical measurements of binary pulsars. We show that in Newtonian mechanics the addition of a corrective term to Newton’s law of gravitation, consistent with the principles of Newtonian mechanics, leads to the same formula of periastron advance as that used in General Relativity, which proves to be valid in all astronomical cases known, even in the cases of binary pulsars such as PSR B1913+16, PSR J1141-6545 and the so-called double pulsar PSR J0737-3039A and PSR J0737-3039B, which are considered as natural relativity laboratories. Thus, among the relativistic phenomena, the periastron advance is one that can be also understood in Newtonian terms by means of an ad hoc assumption.

Model-independent comparisons of pulsar timings to scalar–tensor gravity

Observations of pulsar timing provide strong constraints on scalar–tensor theories of gravity, but these constraints are traditionally quoted as limits on the microscopic parameters (like the Brans–Dicke coupling, for example) that govern the strength of scalar–matter couplings at the particle level in particular models. For binary pulsars whose all five post-Keplerian parameters have been measured, we present fits to timing data directly in terms of the phenomenological couplings (masses, scalar charges, moment of inertia sensitivities and so on) of the stars involved, rather than to the more microscopic parameters of a specific model. For instance, for the double pulsar PSR J0737-3039A/B, we find at the 68% confidence level that the masses are bounded by 1.28 < mA/m⊙ < 1.34 and 1.19 < mB/m⊙ < 1.25, while the scalar charge-to-mass ratios satisfy |aA| < 0.21, |aB| < 0.21 and |aB − aA| < 0.002, independent of the details of the scalar–tensor model involved, and of assumptions about the stellar equations of state. Whenever it is possible to do so, we urge observers to express their results in this more model-independent way, which potentially can then be used by theorists to constrain a great variety of specific models by computing the fit quantities as functions of the microscopic parameters in any particular model. For the Brans–Dicke and quasi-Brans–Dicke models, the constraints coming from the double pulsar obtained in this manner are consistent with, and slightly weaker than, those quoted in the literature.

THE DOUBLE PULSAR ECLIPSES. I. PHENOMENOLOGY AND MULTI-FREQUENCY ANALYSIS

The double pulsar PSR J0737-3039A/B displays short, 30 s eclipses that arise around conjunction when the radio waves emitted by pulsar A are absorbed as they propagate through the magnetosphere of its companion pulsar B. These eclipses offer a unique opportunity to probe directly the magnetospheric structure and the plasma properties of pulsar B. We have performed a comprehensive analysis of the eclipse phenomenology using multi-frequency radio observations obtained with the Green Bank Telescope. We have characterized the periodic flux modulations previously discovered at 820 MHz by McLaughlin et al., and investigated the radio frequency dependence of the duration and depth of the eclipses. Based on their weak radio frequency evolution, we conclude that the plasma in pulsar B's magnetosphere requires a large multiplicity factor (~ 10^5). We also found that, as expected, flux modulations are present at all radio frequencies in which eclipses can be detected. Their complex behavior is consistent with the confinement of the absorbing plasma in the dipolar magnetic field of pulsar B as suggested by Lyutikov & Thompson and such a geometric connection explains that the observed periodicity is harmonically related to pulsar B's spin frequency. We observe that the eclipses require a sharp transition region beyond which the plasma density drops off abruptly. Such a region defines a plasmasphere which would be well inside the magnetospheric boundary of an undisturbed pulsar. It is also two times smaller than the expected standoff radius calculated using the balance of the wind pressure from pulsar A and the nominally estimated magnetic pressure of pulsar B.

Gravitomagnetic effects in Kerr-de Sitter space-time

We explicitly worked out the orbital effects induced on thetrajectory of a test particle by the the weak-field approximationof the Kerr-de Sitter metric. It results that thenode, the pericentre and the mean anomaly undergo secularprecessions proportional to k. We used such theoretical predictions andthe latest observational determinations of the non-standardprecessions of the perihelia of the inner planets of the SolarSystem to put a bound on k getting k ⩽ 10−29 m−2. The node rate of the LAGEOS Earth's satellite yieldsk ⩽ 10−26 m−2. The periastron precession of the double pulsar PSR J0737-3039A/B allows to obtain k ⩽ 3 × 10−21 m−2.Interpreting k as a cosmological constant Λ, it turns out that such constraints are weaker than those obtained from the Schwarzschild-de Sitter metric.

Constraining the cosmological constant and the DGP gravity with the double pulsar PSR J0737-3039

We consider the double pulsar PSR J0737-3039A/B binary system as a laboratory to locally test the orbital effects induced by an uniform cosmological constant Λ in the framework of the known general relativistic laws of gravity, and the DGP braneworld model of gravity independently of the cosmological acceleration itself for which they were introduced. We, first, construct the ratio R = Δ ω ˙ / Δ P of the discrepancies between the phenomenologically determined periastron rate ω ˙ and orbital period P b and their predicted values from the 1PN ω ˙ 1 PN approximation and the third Kepler law P ( 0 ) . Then, we compare its value | R | = ( 0.3 ± 4 ) × 10 - 11 s - 2 , compatible with zero within the errors, to the ratios R Λ and R DGP of the effects induced on the apsidal rate and the orbital period by Λ and the DGP gravity; we find them neatly incompatible with R being R Λ = ( 3.4 ± 0.3 ) × 10 - 8 s - 2 and R DGP = ( 1.4 ± 0.1 ) × 10 - 7 s - 2 , respectively. Such a result, which for the case of Λ is valid also for any other Hooke-like exotic force proportional to r, is in agreement with other negative local tests recently performed in the Solar System with the ratios of the non-Newtonian/Einsteinian perihelion precessions for several pairs of planets.