Maurizio Toscano

Spectra of Southern Pulsars

We compare the spectral properties of the millisecond and slow pulsars detected in the Parkes 70 cm survey. The mean spectral index for the millisecond pulsars (MSPs) is -1.9 ± 0.1, whereas the mean spectral index for the slow pulsars is a surprisingly steep: 1.72 ± 0.04. A Kolmogorov-Smirnov test indicates that there is only a 72% probability that the two distributions differ. As a class, MSPs are therefore only fractionally steeper spectrum objects than slow pulsars, as recent literature would suggest. We then model the expected distribution of MSPs in the Galaxy and find that high-frequency surveys, with sensitivities similar to the current Parkes multibeam survey, are likely to detect MSPs in large numbers. The observed distribution of MSPs will be much less isotropic than that resulting from low-frequency surveys, with 50% of detectable MSPs residing within 11° of the Galactic plane in an all-sky survey.

Parallax of PSR J1744–1134 and the Local Interstellar Medium

We present the annual trigonometric parallax of PSR J1744-1134 derived from an analysis of pulse times of arrival. The measured parallax, π = 2.8 ± 0.3 mas, ranks among the most precisely determined distances to any pulsar. The parallax distance of 357 pc is over twice that derived from the dispersion measure using the Taylor & Cordes model for the Galactic electron distribution. The mean electron density in the path to the pulsar, ne = (8.8 ± 0.9) × 10-3 cm-3, is the lowest for any disk pulsar. We have compared the ne for PSR J1744-1134 with those for another 11 nearby pulsars with independent distance estimates. We conclude that there is a striking asymmetry in the distribution of electrons in the local interstellar medium. The electron column densities for pulsars in the third Galactic quadrant are found to be systematically higher than for those in the first. The former correlate with the position of the well-known local H I cavity in quadrant 3. The excess electrons within the cavity may be in the form of H II clouds marking a region of interaction between the local hot bubble and a nearby superbubble.

The Orbital Evolution and Proper Motion of PSR J2051–0827

We have carried out high-precision timing observations of the eclipsing binary PSR J2051-0827 in the 3.3 years since its discovery. The data indicate that the orbital period is decreasing at a rate of b = (-11 ± 1) × 10-12. If secular, this orbital period derivative implies a decay time for the orbit of only 25 Myr, which is much shorter than the expected timescale for the ablation of the companion. We have also measured the proper motion of the pulsar to be 5±3 mas yr -->−1. Assuming the pulsar is at the dispersion-measure distance, this implies a very slow transverse velocity v -->t=(30±20) km s -->−1. This combination of low velocity and short orbital period argues against the formation of the system in the standard manner, and we discuss the implications for its evolutionary history.

Theory and Philosophy in Education Research: Methodological Dialogues

The issue of methodology is a fundamental concern for all who engage in educational research. Presenting a series of methodological dialogues between emi-nent education researchers including Michael Apple, Gert Biesta, Penny Enslin, John Hattie, Nel Noddings, Michael Peters, Richard Pring and Paul Smeyers, this book explores the ways in which they have chosen and developed research methods to style their investigations and frame their arguments. These dialogues address the specialized and technical aspects of conducting edu-cational research, conceptualize the relationship between methodology and the-ory, and provide in-depth discussion of concerns including falsifiability, openness, interpretation and researcher judgement. Foregrounding the researchers’ first-hand experience and knowledge, this book will provide future and current researchers with a deeper comprehension of the place of theory in education research. An illuminating resource for undergraduate and postgraduate researchers alike, Theory and Philosophy in Education Research confronts the intricate complexities of conducting education research in a highly engaging and accessible way.