We perform population synthesis studies of different types of neutron stars (NSs) (thermally emitting isolated NSs, normal radio pulsars, magnetars) taking into account the magnetic field decay and using results from the most recent advances in NS cooling theory. For the first time, we confront our results with observations using simultaneously the log N–log S distribution for nearby isolated NSs, the log N–log L distribution for magnetars, and the distribution of radio pulsars in the diagram. For this purpose, we fix a baseline NS model (all microphysics input), and other relevant parameters to standard values (velocity distribution, mass spectrum, birth rates, etc.), allowing us to vary the initial magnetic field strength. We find that our theoretical model is consistent with all sets of data if the initial magnetic field distribution function follows a lognormal law with 〈log (B0/G)〉∼ 13.25 and . The typical scenario includes about 10 per cent of NSs born as magnetars, significant magnetic field decay during the first million years of a NS life (only about a factor of 2 for low‐field NSs but more than an order of magnitude for magnetars), and a mass distribution function dominated by low‐mass objects. This model explains satisfactorily all known populations. Evolutionary links between different subclasses may exist, although robust conclusions are not yet possible.

We present extensive spectral and photometric observations of the recycled pulsar/white-dwarf binary containing PSR J0437−4715, which we analyzed together with archival X-ray and gammaray data, to obtain the complete mid-infrared to gamma-ray spectrum. We first fit each part of the spectrum separately, and then the whole multi-wavelength spectrum. We find that the opticalinfrared part of the spectrum is well fit by a cool white dwarf atmosphere model with pure hydrogen composition. The model atmosphere (T eff = 3950 ± 150 K, log g = 6.98 ± 0.15, R WD = (1.9 ± 0.2) × 10 9 cm) fits our spectral data remarkably well for the known mass and distance (M = 0.25 ± 0.02M ⊙ , d = 156.3 ± 1.3 pc), yielding the white dwarf age (τ WD = 6.0 ± 0.5 Gyr). In the UV, we find a spectral shape consistent with thermal emission from the bulk of the neutron star surface, with surface temperature between 1.25 × 10 5 and 3.5 × 10 5 K. The temprature of the thermal spectrum suggests that some heating mechanism operates throughout the life of the neutron star. The temperature distribution on the neutron star surface is non-uniform. In the X-rays, we confirm the presence of a high-energy tail which is consistent with a continuation of the cut-off power-law component (Γ = 1.56 ± 0.01, E cut = 1.1 ± 0.2 GeV) that is seen in gamma-rays and perhaps even extends to the near-UV. Subject headings: pulsars: individual (PSR J0437−4715); white dwarfs 7

We report on six new Chandra observations of the Geminga pulsar wind nebula (PWN). The PWN consists of three distinct elongated structures -two ≈ 0.2d 250 pc long lateral tails and a segmented axial tail of ≈ 0.05d 250 pc length, where d 250 = d/(250pc). The photon indices of the power law spectra of the lateral tails, Γ ≈ 1, are significantly harder than those of the pulsar (Γ ≈ 1.5) and the axial tail (Γ ≈ 1.6). There is no significant diffuse X-ray emission between the lateral tails -the ratio of the X-ray surface brightness between the south tail and this sky area is at least 12. The lateral tails apparently connect directly to the pulsar and show indication of moving footpoints. The axial tail comprises time-variable emission blobs. However, there is no evidence for constant or decelerated outward motion of these blobs. Different physical models are consistent with the observed morphology and spectra of the Geminga PWN. In one scenario, the lateral tails could represent an azimuthally asymmetric shell whose hard emission is caused by the Fermi acceleration mechanism of colliding winds. In another scenario, the lateral tails could be luminous, bent polar outflows, while the blobs in the axial tail could represent a crushed torus. In a resemblance to planetary magnetotails, the blobs of the axial tail might also represent short-lived plasmoids which are formed by magnetic field reconnection in the relativistic plasma of the pulsar wind tail.

To examine the previously claimed fast cooling of the Central Compact Object (CCO) in the Cas A supernova remnant (SNR), we analyzed two Chandra observations of this CCO, taken in a setup minimizing instrumental spectral distortions. We fit the two CCO X-ray spectra from 2006 and 2012 with hydrogen and carbon neutron star atmosphere models. The temperature and flux changes in the 5.5 years between the two epochs depend on the adopted constraints on the fitting parameters and the uncertainties of the effective area calibrations. If we allow a change of the equivalent emitting region size, R em , the effective temperature remains essentially the same. If R Em is held constant, the best-fit temperature change is negative, but its statistical significance ranges from 0.8σ to 2.5σ, depending on the model. If we assume that the optical depth of the ACIS filter contaminant in 2012 was ±10 % different from its default calibration value, the significance of the temperature drop becomes 0.8σ to 3.1σ, for the carbon atmospheres with constant R Em . Thus, we do not see a statistically significant temperature drop in our data, but the involved uncertainties are too large to firmly exclude the previously reported fast cooling. Our analysis indicate a decrease of 4%-6% (1.9-2.9σ significance) for the absorbed flux in the energy range 0.6 − 6 keV between 2006 and 2012, most prominent in the ≈ 1.4-1.8 keV energy range. It could be caused by unaccounted changes of the detector response or contributions from unresolved SNR material along the line of sight to the CCO.

We describe system verification tests and early science results from the pulsar processor (PTUSE) developed for the newly commissioned 64-dish SARAO MeerKAT radio telescope in South Africa. MeerKAT is a high-gain ( ${\sim}2.8\,\mbox{K Jy}^{-1}$ ) low-system temperature ( ${\sim}18\,\mbox{K at }20\,\mbox{cm}$ ) radio array that currently operates at 580–1 670 MHz and can produce tied-array beams suitable for pulsar observations. This paper presents results from the MeerTime Large Survey Project and commissioning tests with PTUSE. Highlights include observations of the double pulsar $\mbox{J}0737{-}3039\mbox{A}$ , pulse profiles from 34 millisecond pulsars (MSPs) from a single 2.5-h observation of the Globular cluster Terzan 5, the rotation measure of Ter5O, a 420-sigma giant pulse from the Large Magellanic Cloud pulsar PSR $\mbox{J}0540{-}6919$ , and nulling identified in the slow pulsar PSR J0633–2015. One of the key design specifications for MeerKAT was absolute timing errors of less than 5 ns using their novel precise time system. Our timing of two bright MSPs confirm that MeerKAT delivers exceptional timing. PSR $\mbox{J}2241{-}5236$ exhibits a jitter limit of $<4\,\mbox{ns h}^{-1}$ whilst timing of PSR $\mbox{J}1909{-}3744$ over almost 11 months yields an rms residual of 66 ns with only 4 min integrations. Our results confirm that the MeerKAT is an exceptional pulsar telescope. The array can be split into four separate sub-arrays to time over 1 000 pulsars per day and the future deployment of S-band (1 750–3 500 MHz) receivers will further enhance its capabilities.