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Register a new userMagnetospheric Eclipses in the Binary Pulsar J0737-3039
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Authors
Maxim Lyutikov UBC
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(Abridged) In the binary radio pulsar system J0737-3039, the faster pulsar A is eclipsed once per orbit. We construct a simple geometric model which successfully reproduces the eclipse light curves, based on the idea that the radio pulses are attenuated by synchrotron absorption on the closed magnetic field lines of pulsar B. The model explains most of the properties of the eclipse: its asymmetric form, the nearly frequency-independent duration, and the modulation of the brightness of pulsar A at both once and twice the rotation frequency of pulsar B in different parts of the eclipse. This detailed agreement confirms the dipolar structure of the stars poloidal magnetic field. The model makes clear predictions for the degree of linear polarization of the transmitted radiation. The weak frequency dependence of the eclipse duration implies that the absorbing plasma is relativistic, with a density much larger than the corotation charge density. Such hot, dense plasma can be effectively stored in the outer magnetosphere, where cyclotron cooling is slow. The gradual loss of particles inward through the cooling radius is compensated by an upward flux driven by a fluctuating component of the current, and by the pumping of magnetic helicity on the closed field lines. The trapped particles are heated to relativistic energies by the damping of magnetospheric turbulence and, at a slower rate, by the absorption of the radio emission of the companion pulsar.
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We investigate the age constraints that can be placed on the double pulsar system using models for the spin-down of the first-born 22.7-ms pulsar A and the 2.77-s pulsar B with characteristic ages of 210 and 50 Myr respectively. Standard models assuming dipolar spin-down of both pulsars suggest that the time since the formation of B is ~50 Myr, i.e. close to Bs characteristic age. However, adopting models which account for the impact of As relativistic wind on Bs spin-down we find that the formation of B took place either 80 or 180 Myr ago, depending the interaction mechanism. Formation 80 Myr ago, closer to Bs characteristic age, would result in the contribution from J0737-3039 to the inferred coalescence rates for double neutron star binaries increasing by 40%. The 180 Myr age is closer to As characteristic age and would be consistent with the most recent estimates of the coalescence rate. The new age constraints do not significantly impact recent estimates of the kick velocity, tilt angle between pre and post-supernova orbital planes or pre-supernova mass of Bs progenitor.
The double pulsar J0737-3039 is the only known system in which the relativistic wind emitted by a radio pulsar demonstrably interacts with the magnetosphere of another one. We report radio interferometric observations of the J0737-3039 system with the VLA at three wavelengths, with each observation spanning a full binary orbit. We detect J0737-3039 at 1.6 and 4.8 GHz, derive a spectral index of -2.3 +/- 0.2, and place an upper limit on its flux density at 8.4 GHz. Orbital modulation is detected in the 1.6 GHz data with a significance of ~2 sigma. Both orbital phase-resolved and phase-averaged measurements at 1.6 GHz are consistent with the entire flux density arising from the pulsed emission of the two pulsars. Contrary to prior results, we find no evidence for unpulsed emission, and limit it to less than 0.5 mJy (5 sigma).
The double pulsar system J0737-3039 is not only a test bed for General Relativity and theories of gravity, but also provides a unique laboratory for probing the relativistic winds of neutron stars. Recent X-ray observations have revealed a point source at the position of the J0737-3039 system, but have failed to detect pulsations or orbital modulation. Here we report on Chandra X-ray Observatory High Resolution Camera observations of the double pulsar. We detect deeply modulated, double-peaked X-ray pulses at the period of PSR J0737-3039A, similar in appearance to the observed radio pulses. The pulsed fraction is ~70%. Purely non-thermal emission from pulsar A plausibly accounts for our observations. However, the X-ray pulse morphology of A, in combination with previously reported spectral properties of the X-ray emission, allows the existence of both non-thermal magnetospheric emission and a broad sinusoidal thermal emission component from the neutron star surface. No pulsations are detected from pulsar B, and there is no evidence for orbital modulation or extended nebular structure. The absence of orbital modulation is consistent with theoretical expectations of a Poynting-dominated relativistic wind at the termination shock between the magnetosphere of B and the wind from A, and with the small fraction of the energy outflow from A intercepted by the termination shock.
We present the first optical observations of the unique system J0737-3039 (composed of two pulsars, hereafter PSR-A and PSR-B). Ultra-deep optical observations, performed with the High Resolution Camera of the Advanced Camera for Surveys on board the Hubble Space Telescope could not detect any optical emission from the system down to m_F435W=27.0 and m_F606W=28.3. The estimated optical flux limits are used to constrain the three-component (two thermal and one non-thermal) model recently proposed to reproduce the XMM-Newton X-ray spectrum. They suggest the presence of a break at low energies in the non-thermal power law component of PSR-A and are compatible with the expected black-body emission from the PSR-B surface. The corresponding efficiency of the optical emission from PSR-As magnetosphere would be comparable to that of other Myr-old pulsars, thus suggesting that this parameter may not dramatically evolve over a time-scale of a few Myr.
The relativistic double neutron star binary PSR J0737-3039 shows clear evidence of orbital phase-dependent wind-companion interaction, both in radio and X-rays. In this paper we present the results of timing analysis of PSR J0737-3039 performed during 2006 and 2011 XMM-Newton Large Programs that collected ~20,000 X-ray counts from the system. We detected pulsations from PSR J0737-3039A (PSR A) through the most accurate timing measurement obtained by XMM-Newton so far, the spin period error being of 2x10^-13 s. PSR As pulse profile in X-rays is very stable despite significant relativistic spin precession that occurred within the time span of observations. This yields a constraint on the misalignment between the spin axis and the orbital momentum axis Delta_A ~6.6^{+1.3}_{-5.4} deg, consistent with estimates based on radio data. We confirmed pulsed emission from PSR J0737-3039B (PSR B) in X-rays even after its disappearance in radio. The unusual phenomenology of PSR Bs X-ray emission includes orbital pulsed flux and profile variations as well as a loss of pulsar phase coherence on time scales of years. We hypothesize that this is due to the interaction of PSR As wind with PSR Bs magnetosphere and orbital-dependent penetration of the wind plasma onto PSR B closed field lines. Finally, the analysis of the full XMM-Newton dataset provided evidences of orbital flux variability (~7%) for the first time, involving a bow-shock scenario between PSR As wind and PSR Bs magnetosphere.
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