Reciprocating Magnetic Fields in the Pulsar Wind Observed from the Black Widow Pulsar J1720-0534

We report the radio observations of the eclipsing black widow pulsar J1720-0534, a 3.26 ms pulsar in orbit with a low mass companion of mass 0.029 to 0.034 M⊙. We obtain the phase-connected timing ephemeris and polarization profile of this millisecond pulsar(MSP) using the Five-hundred-meter Aperture Spherical radio Telescope(FAST), the Green Bank Telescope(GBT), and the Parkes Telescope. For the first time from such a system, an oscillatory polarization angle change was observed from a particular eclipse egress with partial depolarization, indicating 10-milliGauss-level reciprocating magnetic fields oscillating in a length scale of 5 ×10^(3)km(assuming an orbital inclination angle of 90°) outside the companion's magnetosphere. The dispersion measure variation observed during the ingresses and egresses shows the rapid raising of the electron density in the shock boundary between the companion's magnetosphere and the surrounding pulsar wind. We suggest that the observed oscillatory magnetic fields originate from the pulsar wind outside the companion's magnetosphere.

Luminosity of a radio pulsar and its new emission death line

We investigated the pulsar radio luminosity(L),emission efficiency(ratio of radio luminosity to its spin-down powerE),and death line in the magnetic field(B)versus spin period(P)diagram.We found that the dependence of pulsar radio luminosity on its spin-down power(L-E)is very weak,shown as L^E0.06,which deduces an equivalent inverse correlation between emission efficiency and spin-down power asξ~E-0.94.Furthermore,we examined the distributions of radio luminosity of millisecond and normal pulsars and found that for the similar spin-down powers,the radio luminosity of millisecond pulsars is about one order of magnitude lower than that of the normal pulsars.The analysis of pulsar radio flux suggests that these correlations are not due to a selective effect but are intrinsic to the pulsar radio emission physics.Their radio radiations may be dominated by the different radiation mechanisms.The cutoff phenomenon of currently observed radio pulsars in B-P diagram is usually referred as the"pulsar death line",which corresponds toE≈1030 erg s-1 and is obtained by the cut-off voltage of electron acceleration gap in the polar cap model of pulsar proposed by Ruderman and Sutherland.Observationally,this death line can be inferred by the actual observed pulsar flux S≥1 mJy and 1 kpc distance,together with the maximum radio emission efficiency of 1%.However,the observation data show that the 37 pulsars pass over the death line,including the recently observed two pulsars with long periods of 23.5 s and 12.1 s,which violate the prediction of the polar cap model.At present,the actual observed pulsar flux can reach0.01 mJy by FAST telescope.This will arise the observational limit of spin-down power of pulsars as low as E˙≈1028 erg s-1.This means that the new death line is downward shifted two orders of magnitude,which might be favorably referred as the"observational limit–line".Accordingly,the pulsar theoretical model for the cut-off voltage of gap should be heavily modified.

β^--Decay Half-Lives for Waiting Point Nuclei Around N=126

We have systematically analyzed the experimental β--decay half-lives of waiting point heavy nuclei around neutron number N = 126. A new set of parameters for the exponential formula of β^--decay half-lives is proposed. The forbidden transition effects are included in the new set of parameters self-consistently. Theoretical β^--decay half-lives of nuclei around N = 126 are compared with recent theoretical results and experimental data. It is found that the new theoretical results are in better agreement with experimental data. The unknown β^--decay half-lives of some nuclei in this region are predicted for studies on nuclear structure far from stability and the nucleosynthesis in stars.