Crab Pulsar

Abstract: This catalog summarizes 117 high-confidence > 0.1 GeV gamma-ray pulsar detections using three years of data acquired by the Large Area Telescope (LAT) on the Fermi satellite. Half are neutron stars discovered using LAT data, through periodicity searches in gamma-ray and radio data around LAT unassociated source positions. The 117 pulsars are evenly divided into three groups: millisecond pulsars, young radio-loud pulsars, and young radio-quiet pulsars. We characterize the pulse profiles and energy spectra and derive luminosities when distance information exists. Spectral analysis of the off-peak phase intervals indicates probable pulsar wind nebula emission for four pulsars, and off-peak magnetospheric emission for several young and millisecond pulsars. We compare the gamma-ray properties with those in the radio, optical, and X-ray bands. We provide flux limits for pulsars with no observed gamma-ray emission, highlighting a small number of gamma-faint, radio-loud pulsars. The large, varied gamma-ray pulsar sample constrains emission models. Fermi's selection biases complement those of radio surveys, enhancing comparisons with predicted population distributions.

Abstract: As is so often the case either the poet has an insight so far denied to the rest of us or his theory of pulsars is quite muddled. A great deal now seems under­ stood about these delightful surprising objects-except for details of how they pulse. But there are already so many clues from pulsar observations that one cannot be optimistic that continued observations of the periodic radio signals will offer crucial new evidence. In the two years since the review of Hewish (1970) the number of observed pulsars has increased modestly from 50 to 58 (November 1971), accompanied by a plethora of over three hundred theoretical papers. There have been.no novel revelations: The rotating neutron star still has no serious competitor as the pulsar clock; its spin is almost certainly coupled to its environment by a huge magnetic field for which a consensus of estimates gives a value at the stellar surface of order 1012 G; the observed variations in radio in­ tensity (and also in optical, X-ray, and ')I-ray fluxes for the pulsar in the Crab nebula) are usually assumed to be associated with nonalignment of the stellar dipole magnetic field and spin axis. Some kind of coherent emission process is necessary to account for the enormous radio intensities of pulsars. All of these entrenched ideas have become even more established. There have been activity and progress in the following areas: (1) The rich variety of pulse shapes, polarizations, and intensity variations have been further confirmed and explored. In a given pulsar there can be marked correlation over many pulses as well as remarkable differences. The main problem now is deciding which among the numerous data are fundamental and how many of them a tentative theory must fit. (2) An enormous amount of detail about the Crab pulsar (NP 0532) radia­ tion is now available: radio, optical, X-ray and ')I-ray pulses, their structure, and correlations between pulses in different regimes. Changes in the surrounding nebula have been described that may be associated with pulsar variations. Very precise timing measurements before and after period discontinuities ("glitches")

Abstract: The rotation of more than 700 pulsars has been monitored using the 76-m Lovell Telescope at Jodrell Bank. Here we report on a new search for glitches in the observations, revealing 128 new glitches in the rotation of 63 pulsars. Combining these new data with those already published, we present a data base containing 315 glitches in 102 pulsars. The data base was used to study the glitch activity among the pulsar population, finding that it peaks for pulsars with a characteristic age τ c ∼ 10 kyr and decreases for longer values of τ c, disappearing for objects with τ c > 20 Myr. The glitch activity is also smaller in the very young pulsars (τ c 1 kyr). The cumulative effect of glitches, a collection of instantaneous spin-up events, acts to reduce the regular long-term spin-down rate |u ν| of the star. The percentage of |u ν| reversed by glitch activity was found to vary between 0.5 and 1.6 per cent for pulsars with spin-down rates |u ν| between 10 −14 and 3.2 × 10 −11 Hz s −1 , decreasing to less than 0.01 per cent at both higher and lower spin-down rates. These ratios are interpreted in terms of the amount of superfluid involved in the generation of glitches. In this context, the activity of the youngest pulsar studied, the Crab pulsar, may be explained by quake-like activity within the crust. Pulsars with low spin-down rates seem to exhibit mostly small glitches, matching well the decrease of their crustal superfluid. Through the analysis of glitch sizes, it was found that the particular glitching behaviour of PSR J0537−6910 and the Vela pulsar may be shared by most Vela-like pulsars. These objects present most of their glitches with characteristic frequency and frequency derivative jumps, occurring at regular intervals of time. Their behaviour is different from other glitching pulsars of similar characteristic age.