System PSR J0737-3039 Research Articles

Spindown of Pulsars Interacting with Companion Winds: The Impact of Magnetospheric Compression

Pulsars in binary systems with strong companion winds can have the magnetopause separating their magnetosphere from the wind located well within their light cylinder. This bow-like enclosure effectively creates a waveguide that confines the pulsar’s electromagnetic fields and can significantly alter its spindown. In this paper, we study the spindown of compressed pulsar magnetospheres in such systems. We parameterize the confinement as the ratio between the equatorial position of the magnetopause (or standoff distance) R m and the pulsar’s light cylinder R LC. Using particle-in-cell simulations, we quantify the pulsar spindown for a range of compressions, R m/R LC = 1/3–1, and inclination angles, χ = 0°…90°, between magnetic and rotation axes. Our strongly confined models (R m/R LC = 1/3) show two distinct limits. For χ = 0°, the spindown of a compressed pulsar magnetosphere is enhanced by approximately a factor of three compared to an isolated pulsar due to the increased number of open magnetic field lines. Conversely, for χ = 90°, the compressed pulsar spins down at less than 40% of the rate of an isolated reference pulsar due to the mismatch between the pulsar wind stripe wavelength and the waveguide size. We apply our analysis to the 2.77 s oblique rotator (χ = 60°) in the double-pulsar system PSR J0737-3039. With the numerically derived spindown estimate, we constrain its surface magnetic field to B * ≈ (7.3 ± 0.2) × 1011 G. We discuss the time modulation of its period derivative, the effects of compression on its braking index, and implications for the radio eclipse in PSR J0737-3039.

Simulation of the orbit and spin period evolution of the double pulsars PSR J0737-3039 from their birth to coalescence induced by gravitational wave radiation

The complete orbital and spin period evolutions of the double neutron star (NS) system PSR J0737–3039 are simulated from birth to coalescence, which include the two observed radio pulsars classified as primary NS PSR J0737–3039A and companion NS PSR J0737–3039B. By employing the characteristic age of PSR J0737–3039B to constrain the true age of the double pulsar system, the initial orbital period and initial binary separation are obtained as 2.89 h and 1.44 × 106 km, respectively, and the coalescence age or the lifetime from the birth to merger of PSR J0737–3039 is obtained to be 1.38 × 108 yr. At the last minute of coalescence, corresponding to the gravitational wave frequency changing from 20 Hz to 1180 Hz, we present the binary separation of PSR J0737–3039 to be from 442 km to 30 km, while the spin periods of PSR J0737–3039A and PSR J0737–3039B are 27.10 ms and 4.63 s, respectively. From the standard radio pulsar emission model, before the system merged, the primary NS could still be observed by a radio telescope, but the companion NS had crossed the death line in the pulsar magnetic-field versus period (B – P) diagram at which point it is usually considered to cease life as a pulsar. This is the first time that the whole life evolutionary simulation of the orbit and spin periods for a double NS system is presented, which provides useful information for observing a primary NS at the coalescence stage.

Deconfinement of nonstrange hadronic matter with nucleons and Δ baryons to quark matter in neutron stars

We explore the possibility of formation of [Formula: see text] baryons (1232[Formula: see text]MeV) in neutron star matter in an effective chiral model within the relativistic mean-field framework. With variation in delta-meson couplings, consistent with the constraints imposed on them, the resulting equation-of-state (EoS) is obtained and the neutron star properties are calculated for static and spherical configuration. Within the framework of our model, the critical densities of formation of [Formula: see text] and the properties of neutron stars (NS) are found to be very sensitive to the iso-vector coupling compared to the scalar or vector couplings. We revisit the [Formula: see text] puzzle and look for the possibility of phase transition from nonstrange hadronic matter (including nucleons and [Formula: see text]) to deconfined quark matter, based on QCD theories. The resultant hybrid star configurations satisfy the observational constraints on mass from the most massive pulsars PSR J1614-2230 and PSR J0348+0432 in static condition obtained with the general hydrostatic equilibrium based on GTR. Our radius estimates are well within the limits imposed from observational analysis of QLMBXs. The obtained values of [Formula: see text] are in agreement with the recent bounds specified from the observation of gravitational wave (GW170817) from binary neutron star merger. The constraint on baryonic mass from the study of binary system PSR J0737-3039 is also satisfied with our hybrid EoS.

Similarity of PSR J1906+0746 to PSR J0737–3039: a Candidate of a New Double Pulsar System?

Abstract PSR J1906+0746 is a nonrecycled strong magnetic field neutron star (NS), sharing the properties of the secondary-formed NS PSR J0737–3039B in the double pulsar system PSR J0737–3039AB. By comparing the orbital parameters of PSR J1906+0746 with those of PSR J0737–3039AB, we conclude that both systems have a similar origin and evolution history, involving an e-capture process for forming the second-born NS, like in the case of PSR J0737–3039B. We expect the companion of PSR J1906+0746 to be a long-lived recycled pulsar with radio beams that currently cannot be observed from Earth. We suggest possible ways to detect its presence. To compare PSR J1906+0746 with PSR J0737–3039, we also present the mass distribution of eight pairs of double NSs and find that in double NSs the mass of the recycled pulsar is usually larger than that of the nonrecycled one, which may be the result of accretion.

The fan beam model for the pulse evolution of PSR J0737-3039B

Average radio pulse profile of a pulsar B in a double pulsar system PSR J0737−3039A/B exhibits an interesting behaviour. During the observation period between 2003 and 2009, the profile evolves from a single-peaked to a double-peaked form, following disappearance in 2008, indicating that the geodetic precession of the pulsar is a possible origin of such behaviour. The known pulsar beam models can be used to determine the geometry of PSR J0737−3039B in the context of the precession. We study how the fan-beam geometry performs in explaining the observed variations of the radio profile morphology. It is shown that the fan beam can successfully reproduce the observed evolution of the pulse width, and should be considered as a serious alternative for the conal-like models.

Verification of f(R)-gravity in binary pulsars

We develop the parameterized post-Keplerian approach for class of analytic f (R) -gravity models. Using the double binary pulsar system PSR J0737-3039 data we obtain restrictions on the parameters of this class of f (R) -models and show that f (R) -gravity is not ruled out by the observations in strong field regime.

Strong-field tests of f(R)-gravity in binary pulsars

We develop the parameterized post-Keplerian approach for class of analytic [Formula: see text]-gravity models. Using the double binary pulsar system PSR J0737-3039 data we obtain restrictions on the parameters of this class of [Formula: see text]-models and show that [Formula: see text]-gravity is not ruled out by the observations in strong field regime. The additional and more strong corresponding restriction is extracted from solar system data.

Effect of geodetic precession on the evolution of pulsar high-energy pulse profiles as derived with the striped-wind model

Geodetic precession has been observed directly in the double-pulsar system PSR J0737-3039. Its rate has even been measured and agrees with predictions of general relativity. Very recently, the double pulsar has been detected in X-rays and gamma-rays. This fuels the hope observing geodetic precession in the high-energy pulse profile of this system. Unfortunately, the geometric configuration of the binary renders any detection of such an effect unlikely. Nevertheless, this precession is probably present in other relativistic binaries or double neutron star systems containing at least one X-ray or gamma-ray pulsar.}{We compute the variation of the high-energy pulse profile expected from this geodetic motion according to the striped-wind model. We compare our results with two-pole caustic and outer gap emission patterns.}{For a sufficient misalignment between the orbital angular momentum and the spin angular momentum, a significant change in the pulse profile as a result of geodetic precession is expected in the X-ray and gamma-ray energy band.}{The essential features of the striped wind are indicated in several plots showing the evolution of the maximum of the pulsed intensity, the separation of both peaks, if present, and the variation in the width of each peak. We highlight the main differences with other competing high-energy models.}{We make some predictions about possible future detection of high-energy emission from double neutron star systems with the highest spin precession rate. Such observations will definitely favour some pulsed high-energy emission scenarios.

PSR J1756−2251: a pulsar with a low-mass neutron star companion

The pulsar PSR J1756$-$2251 resides in a relativistic double neutron star (DNS) binary system with a 7.67-hr orbit. We have conducted long-term precision timing on more than 9 years of data acquired from five telescopes, measuring five post-Keplerian parameters. This has led to several independent tests of general relativity (GR), the most constraining of which shows agreement with the prediction of GR at the 4% level. Our measurement of the orbital decay rate disagrees with that predicted by GR, likely due to systematic observational biases. We have derived the pulsar distance from parallax and orbital decay measurements to be 0.73$_{-0.24}^{+0.60}$ kpc (68%) and < 1.2 kpc (95% upper limit), respectively; these are significantly discrepant from the distance estimated using Galactic electron density models. We have found the pulsar mass to be 1.341$\pm$0.007 M$_\odot$, and a low neutron star (NS) companion mass of 1.230$\pm$0.007 M$_\odot$. We also determined an upper limit to the spin-orbit misalignment angle of 34{\deg} (95%) based on a system geometry fit to long-term profile width measurements. These and other observed properties have led us to hypothesize an evolution involving a low mass loss, symmetric supernova progenitor to the second-formed NS companion, as is thought to be the case for the double pulsar system PSR J0737$-$3039A/B. This would make PSR J1756$-$2251 the second compact binary system providing concrete evidence for this type of NS formation channel.

RADIUS CONSTRAINT OF THE RECYCLED DOUBLE PULSAR PSR J0737-3039

We investigate the radius of the recycled pulsar in double pulsar system PSR J0737-3039. In the standard accretion spin-up model, the recycled pulsar spin up continues until arriving at a minimum spin period, or so-called "equilibrium period", which is related to the stellar magnetic field, the accretion rate and radius. The generic spin-down age may give realistic estimates for normal pulsar PSR J0737-3039B, since its present spin period is much longer than the one at birth. In this paper, we estimate the radius of millisecond pulsar (MSP) PSR J0737-3039A by assuming its true age is same as the spin-down age of its companion PSR J0737-3039B. We find that the radius of recycled pulsar PSR J0737-3039A ranges approximately from 12 to 38 km, and it should be far from the composition of strange quark matters, as shown in the mass-radius diagram.

PSR J0737–3039B: A PROBE OF RADIO PULSAR EMISSION HEIGHTS

In the double pulsar system PSR J0737−3039A/B, the strong wind produced by pulsar A distorts the magnetosphere of pulsar B. The influence of these distortions on the orbital-dependent emission properties of pulsar B can be used to determine the location of the coherent radio emission generation region in the pulsar magnetosphere. Using a model of the wind-distorted magnetosphere of pulsar B and the well-defined geometrical parameters of the system, we determine the minimum emission height to be ∼20RNS in the two bright orbital longitude regions. We can determine the maximum emission height by accounting for the amount of deflection of the polar field line with respect to the magnetic axis using the analytical magnetic reconnection model of Dungey and the semi-empirical numerical model of Tsyganenko. Both of these models estimate the maximum emission height to be ∼2500RNS. The minimum and maximum emission heights we calculate are consistent with those estimated for normal isolated pulsars.

SPIN TILTS IN THE DOUBLE PULSAR REVEAL SUPERNOVA SPIN ANGULAR-MOMENTUM PRODUCTION

The system PSR J0737-3039 is the only binary pulsar known to consist of two radio pulsars (PSR J0737-3039 A and PSR J0737-3039 B). This unique configuration allows measurements of spin orientation for both pulsars: pulsar A's spin is tilted from the orbital angular momentum by no more than 14 degrees at 95% confidence; pulsar B's by 130 +/- 1 degrees at 99.7% confidence. This spin-spin misalignment requires that the origin of most of B's present-day spin is connected to the supernova that formed pulsar B. Under the simplified assumption of a single, instantaneous kick during the supernova, the spin could be thought of as originating from the off-center nature of the kick, causing pulsar B to tumble to its misaligned state. With this assumption, and using current constraints on the kick magnitude, we find that pulsar B's instantaneous kick must have been displaced from the center of mass of the exploding star by at least 1 km and probably 5--10 km. Regardless of the details of the kick mechanism and the process that produced pulsar B's current spin, the measured spin-spin misalignment in the double pulsar system provides an empirical, direct constraint on the angular momentum production in this supernova. This constraint can be used to guide core-collapse simulations and the quest for understanding the spins and kicks of compact objects.

HIGH-PRECISION ORBITAL AND PHYSICAL PARAMETERS OF DOUBLE-LINED SPECTROSCOPIC BINARY STARS—HD78418, HD123999, HD160922, HD200077, AND HD210027

We present high precision radial velocities (RVs) of double-lined spectroscopic binary stars HD78418, HD123999, HD160922, HD200077 and HD210027. They were obtained based on the high resolution echelle spectra collected with the Keck I/Hires, Shane/CAT/Hamspec and TNG/Sarge telescopes/spectrographs over the years 2003-2008 as a part of TATOOINE search for circumbinary planets. The RVs were computed using our novel iodine cell technique for double-line binary stars. The precision of the RVs is of the order of 1-10 m/s. Our RVs combined with the archival visibility measurements from the Palomar Testbed Interferometer allow us to derive very precise spectroscopic/astrometric orbital and physical parameters of the binaries. In particular, we derive the masses, the absolute K and H band magnitudes and the parallaxes. The masses together with the absolute magnitudes in the K and H bands enable us to estimate the ages of the binaries. These RVs allow us to obtain some of the most accurate mass determinations of binary stars. The fractional accuracy in m*sin(i) only and hence based on the RVs alone ranges from 0.02% to 0.42%. When combined with the PTI astrometry, the fractional accuracy in the masses ranges in the three best cases from 0.06% to 0.5%. Among them, the masses of HD210027 components rival in precision the mass determination of the components of the relativistic double pulsar system PSRJ0737-3039. In the near future, for double-lined eclipsing binary stars we expect to derive masses with a fractional accuracy of the order of up to ~0.001% with our technique. This level of precision is an order of magnitude higher than of the most accurate mass determination for a body outside the Solar System - the double neutron star system PSRB1913+16.

Nuclear Constraints on the Moments of Inertia of Neutron Stars

The properties and structure of neutron stars are determined by the equation of state (EOS) of neutron-rich stellar matter. While the collective flow and particle production in relativistic heavy-ion collisions have tightly constrained the EOS of symmetric nuclear matter up to about 5 times the normal nuclear matter density, more recent experimental data on isospin diffusion and isoscaling in heavy-ion collisions at intermediate energies have constrained considerably the density dependence of the nuclear symmetry energy at subsaturation densities. Although there are still many uncertainties and challenges to pin down completely the EOS of neutron-rich nuclear matter, heavy-ion reaction experiments in terrestrial laboratories have limited the EOS of neutron-rich nuclear matter to a range much narrower than that spanned by the various EOSs currently used in astrophysical studies in the literature. These nuclear physics constraints could thus provide more reliable information about the properties of neutron stars. Within well-established formalisms using the nuclear-constrained EOSs, we study the moments of inertia of neutron stars. We place special emphasis on component A of the extremely relativistic double neutron star system PSR J0737–3039. Its moment of inertia is found to be between 1.30 × 1045 and 1.63 × 1045 g cm2. Moreover, the transition density at the crust-core boundary is shown to lie in the narrow range ρt = 0.091-0.093 fm−3.

PSR J0737−3039: Interacting Pulsars in X‐Rays1

We present the results of a ~230 ks long X-ray observation of the relativistic double-pulsar system PSR J0737–3039 obtained with the XMM-Newton satellite in 2006 October. We confirm the detection in X-rays of pulsed emission from PSR J0737–3039A (PSR A), mostly ascribed to a soft nonthermal power-law component (Γ ~ 3.3) with a 0.2-3 keV luminosity of ~1.9 × 1030 erg s−1 (assuming a distance of 500 pc). For the first time, pulsed X-ray emission from PSR J0737–3039B (PSR B) is also detected in part of the orbit. This emission, consistent with thermal radiation with temperature kBT 30 eV and a bolometric luminosity of ~1032 erg s−1, is likely powered by heating of PSR B's surface caused by PSR A's wind. A hotter (~130 eV) and fainter (~5 × 1029 erg s−1) thermal component, probably originating from backfalling particles heating polar caps of either PSR A or PSR B, is also required by the data. No signs of X-ray emission from a bow shock between PSR A's wind and the interstellar medium or PSR B's magnetosphere are present. The upper limit on the luminosity of such a shock component (~1029 erg s−1) constrains the wind magnetization parameter σM of PSR A to values greater than 1.

Members of the double pulsar system PSR J0737-3039: Neutron stars or strange stars?

One interesting method of constraining the dense matter Equations of State is to measure the advancement of the periastron of the orbit of a binary radio pulsar (when it belongs to a double neutron star system). There is a great deal of interest on applicability of this procedure to the double pulsar system PSR J0737-3039 (A/B). Although the above method can be applied to PSR A in future within some limitations, for PSR B this method cannot be applied. On the other hand, the study of genesis of PSR B might be useful in this connection and its low mass might be an indication that it could be a strange star.

The post-Newtonian mean anomaly advance as further post-Keplerian parameter in pulsar binary systems

The post-Newtonian gravitoelectric secular rate of the mean anomaly ℳ is worked out for a two-body system in the framework of the General Theory of Relativity. The possibility of using such an effect, which is different from the well known decrease of the orbital period due to gravitational wave emission, as a further post-Keplerian parameter in binary systems including at least one pulsar is examined. The resulting effect is almost three times larger than the periastron advance $\dot{\omega}$ . E.g., for the recently discovered double pulsar system PSR J0737-3039 A+B it would amount to −47.79 deg yr−1. This implies that it could be extracted from the linear part of a quadratic fit of the orbital phase because the uncertainties both in the linear drift due to the mean motion and in the quadratic shift due to the gravitational wave are smaller. The availability of such additional post-Keplerian parameter would be helpful in further constraining the General Theory of Relativity, especially for such systems in which some of the other post-Keplerian parameters can be measured with limited accuracy. Moreover, also certain pulsar-white dwarf binary systems, characterized by circular orbits like PSR B1855+09 and a limited number of measured post-Keplerian parameters, could be used for constraining competing theories of gravity.

Exotica in rotating compact stars

The determination of mass and radius of a single neutron star EXO 0748-676 has been reported recently. Also, the estimate of radius from the measurement of moment of inertia of pulsar A in double pulsar system PSR J0737-3039 would be possible in near future. Here we construct models of static and uniformly rotating neutron stars involving exotic matter and compare our theoretical calculations with the recent findings from observations to probe dense matter in neutron stars.

Gravitational Faraday rotation in binary pulsar systems

We study the gravitational Faraday rotation, on linearly polarized light rays emitted by a pulsar, orbiting another compact object. We relate the rotation angle to the orbital phase of the emitting pulsar, as well as to other parameters describing its orbit and the orientation of the angular momentum of the binary companion. We give numerical estimates of the effect for the double-pulsar system PSR J0737-3039, and we note that the expected magnitude is exceedingly small, making the effect unlikely to be observed with present technology. It is however interesting per se, since in this phenomenon, gravito-magnetism plays a leading role, unlike what happens, for instance, when studying light bending or gravitational time delay, where it appears as a correction to the gravito-electric contribution. Also, we envisage the possibility that this effect could be relevant, at least in principle, for a pulsar orbiting a non charged black-hole.

Possible New Clues towards Understanding Pulsar Radio Emission

The origin of pulsar radio emission has been a mystery for more than 35 years. The observed extremely high brightness temperatures strongly suggest that the radio emission must be highly coherent, but the real mechanism in operation has been evading identification. Instead of trying to solve this decades long problem, here I discuss several recent new observations and the ideas to interpret them, which shed new light on understanding pulsar radio emission. The topics include (1) a recent XMM-Newton observation of the famous, old-drifting PSR B0943+10 and its physical implications; (2) models to interpret the radio flaring activity of the pulsar B in the double pulsar system PSR J0737–3099; (3) possible identification of the inward radio emission from some pulsars; and (4) the suggestion that GCRT J1745–3009 is a white dwarf pulsar. Two possible interpretations to the recently identified Rotating RAdio Transients (RRATs) are also proposed.