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Register a new userOn the Formation and Progenitor of PSR J0737-3039: New Constraints on the Supernova Explosion Forming Pulsar B
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We revisit the formation of PSR J0737-3039, taking into account the most recent observational constraints. We show that the most likely kick velocity and progenitor parameters depend strongly on the consideration of the full five-dimensional PDF for the magnitude and direction of the kick velocity imparted to pulsar B at birth, the mass of pulsar Bs pre-supernova helium star progenitor, and the pre-supernova orbital separation, and on the adopted prior assumptions. The priors consist of the transverse systemic velocity, the age of the system, and the treatment of the unknown radial velocity. Since the latter cannot be determined from observation, we adopt a statistical approach and use theoretical radial-velocity distributions obtained from population synthesis calculations for coalescing double neutron stars. We find that the prior assumptions about the pre-supernova helium star mass affect the derived most likely parameters significantly: when the minimum helium star mass required for neutron star formation is assumed to be 2.1Msun, the most likely kick velocity ranges from 70-180km/s; when masses lower than 2.1Msun are assumed to allow neutron star formation, the most likely kick velocity can be as low as a few km/s, although the majority of the considered models still yield most likely kick velocities of 50-170km/s. We also show that the proximity of the double pulsar to the Galactic plane and the small proper motion do not pose stringent constraints on the kick velocity and progenitor mass of pulsar B. Instead, the constraints imposed by the orbital dynamics of asymmetric supernova explosions turn out to be much more restrictive. We conclude that the currently available observational constraints cannot be used to favor a specific core-collapse and neutron star formation mechanism. (abridged)
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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.
We report results from Exploratory Time observations of the double-pulsar system PSR J0737-3039 using the Green Bank Telescope (GBT). The large gain of the GBT, the diversity of the pulsar backends, and the four different frequency bands used have allowed us to make interesting measurements of a wide variety of phenomena. Here we briefly describe results from high-precision timing, polarization, eclipse, scintillation velocity, and single-pulse work.
(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.
We have investigated the eclipse of the 23-ms pulsar J0737-3039A by its 2.8-s companion PSR J0737-3039B in the recently discovered double pulsar system using data taken with the Green Bank Telescope at 820 MHz. We find that the pulsed flux density at eclipse is strongly modulated with half the periodicity of the 2.8-s pulsar. The eclipse occurs earlier and is deeper at those rotational phases of B when its magnetic axis is aligned with the line of sight than at phases when its magnetic axis is at right angles to the line of sight. This is consistent with the eclipse of A being due to synchrotron absorption by the shock-heated plasma surrounding B, the asymmetry arising from the higher plasma densities expected in the B magnetospheres polar cusps.
We present the current estimates of the Galactic merger rate of double-neutron-star (DNS) systems. Using a statistical analysis method, we calculate the probability distribution function (PDF) of the rate estimates, which allows us to assign confidence intervals to the rate estimates. We calculate the Galactic DNS merger rate based on the three known systems B1913+16, B1534+12, and J0737-3039. The discovery of J0737-3039 increases the estimated DNS merger rate by a factor ~6 than what is previously known. The most likely values of DNS merger rate lie in the range 3-190 per Myr depending on different pulsar models. Motivated by a strong correlation between the peak rate estimates and a pulsar luminosity function, we calculate a global probability distribution as a single representation of the parameter space covered by different pulsar population models. We compare the global PDF with the observed supernova Ib/c rate, which sets an upper limit on the DNS merger rate. Finally, we remark on implications of new discoveries such as of J1756-2251, the 4th DNS in the Galactic disk, and J1906+0746, a possible DNS system.
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