Timing observations of 40 mostly young pulsars using the ATNF Parkes radio telescope between 1990 January and 1998 December are reported. In total, 20 previously unreported glitches and ten other glitches were detected in 11 pulsars. These included 12 glitches in PSR J1341−6220, corresponding to a glitch rate of 1.5 glitches per year. We also detected the largest known glitch, in PSR J1614−5047, with ∆ν g /ν ≈ 6.5 × 10 −6 where ν = 1/P is the pulse frequency. Glitch parameters were determined both by extrapolating timing solutions to inter-glitch intervals and by phase-coherent timing fits across the glitch(es). These fits also gave improved positions and dispersion measures for many of the pulsars. Analysis of glitch parameters, both from this work and from previously published results, shows that most glitches have a fractional amplitude ∆ν g /ν of between 10 −8 and 10 −6 . There is no consistent relationship between glitch amplitude and the time since the previous glitch or the time to the following glitch, either for the ensemble or for individual pulsars. As previously recognised, the largest glitch activity is seen in pulsars with ages of order 10 4 years, but for about 30 per cent of such pulsars, no glitches were detected in the 8-year data span. There is some evidence for a new type of timing irregularity in which there is a significant increase in pulse frequency over a few days, accompanied by a decrease in the magnitude of the slowdown rate. Fits of an exponential recovery to post-glitch data show that for most older pulsars, only a small fraction of the glitch decays. In some younger pulsars, a large fraction of the glitch decays, but in others, there is very little decay. Apart from the Crab pulsar, there is no clear dependence of recovery timescale on pulsar age.

We present results of Compton Gamma-Ray Observatory/EGRET observations of the unidentified high-energy γ-ray sources 2EG J1049−5847 (GEV J1047−5840, 3EG J1048−5840) and 2EG J1103−6106 (3EG J1102−6103). These sources are spatially coincident with the young, energetic radio pulsars PSRs B1046−58 and J1105−6107, respectively. We find evidence for an association between PSR B1046−58 and 2EG J1049−5847. The γ-ray pulse profile, obtained by folding time-tagged photons having energies above 400 MeV using contemporaneous radio ephemerides, has probability of arising by chance of 1.2 × 10 −4 according to the binning-independent H-test. A spatial analysis of the on-pulse 1 Alfred P. Sloan Research Fellow; vicky@space.mit.edu 2 jes@space.mit.edu 3 mattox@bu.edu 4 rmanches@atnf.csiro.au 5 mbailes@swin.edu.au -2photons reveals a point source of equivalent significance 10.2σ. Off-pulse, the significance drops to 5.8σ. Archival ASCA data show that the only hard X-ray point source in the 95% confidence error box of the γ-ray source is spatially coincident with the pulsar within the 1 ′ uncertainty (Pivovaroff, Kaspi, & Gotthelf 1999). The double peaked γ-ray pulse morphology and leading radio pulse are similar to those seen for other γ-ray pulsars and are well-explained in models in which the γ-ray emission is produced in charge-depleted gaps in the outer magnetosphere. The inferred pulsed γ-ray flux above 400 MeV, (2.5 ± 0.6) × 10 −10 erg cm −2 s −1 , represents 0.011±0.003 of the pulsar's spin-down luminosity, for a distance of 3 kpc and 1 sr beaming. For PSR J1105−6107, light curves obtained by folding EGRET photons using contemporaneous radio ephemerides show no significant features. We conclude that this pulsar converts less than 0.014 of its spin-down luminosity into E > 100 MeV γ-rays beaming in our direction (99% confidence), assuming a distance of 7 kpc, 1 sr beaming and a duty cycle of 0.5.

[1] We have studied the 10 mm temperature of overcast skies, as measured from the ground, in a coastal region of South Australia. The long-term aim of this work is to be able to use measurements of the sky temperature, plus other readily measured ground-based parameters, to recognize the presence, or otherwise, of clouds. Comparisons have been made between the 10 mm sky temperature and cloud height in overcast conditions, measured both with a ceilometer and radiosondes. A low-altitude cloud exhibits a wide range of emissivities, such that clouds with base heights up to 1200 m have emissivities ranging from below 0.2 to close those expected for black bodies at those wavelengths. However, higher clouds exhibit different properties, as their temperatures approach those to be expected for a clear sky with water vapor.

Timing observations of 40 mostly young pulsars using the ATNF Parkes radio telescope between 1990 January and 1998 December are reported. In total, 20 previously unreported glitches and ten other glitches were detected in 11 pulsars. These included 12 glitches in PSR J1341−6220, corresponding to a glitch rate of 1.5 glitches per year. We also detected the largest known glitch, in PSR J1614−5047, with ∆ν g /ν ≈ 6.5 × 10 −6 where ν = 1/P is the pulse frequency. Glitch parameters were determined both by extrapolating timing solutions to inter-glitch intervals and by phase-coherent timing fits across the glitch(es). These fits also gave improved positions and dispersion measures for many of the pulsars. Analysis of glitch parameters, both from this work and from previously published results, shows that most glitches have a fractional amplitude ∆ν g /ν of between 10 −8 and 10 −6 . There is no consistent relationship between glitch amplitude and the time since the previous glitch or the time to the following glitch, either for the ensemble or for individual pulsars. As previously recognised, the largest glitch activity is seen in pulsars with ages of order 10 4 years, but for about 30 per cent of such pulsars, no glitches were detected in the 8-year data span. There is some evidence for a new type of timing irregularity in which there is a significant increase in pulse frequency over a few days, accompanied by a decrease in the magnitude of the slowdown rate. Fits of an exponential recovery to post-glitch data show that for most older pulsars, only a small fraction of the glitch decays. In some younger pulsars, a large fraction of the glitch decays, but in others, there is very little decay. Apart from the Crab pulsar, there is no clear dependence of recovery timescale on pulsar age.