Predictions of Gamma-ray Emission from Globular Cluster Millisecond Pulsars Above 100 MeV

The recent Fermi detection of the globular cluster (GC) 47 Tucanae highlighted the importance of modeling collective gamma-ray emission of millisecond pulsars (MSPs) in GCs. Steady flux from such populations is also expected in the very high energy (VHE) domain covered by ground-based Cherenkov telescopes. We present pulsed curvature radiation (CR) as well as unpulsed inverse Compton (IC) calculations for an ensemble of MSPs in the GCs 47 Tucanae and Terzan 5. We demonstrate that the CR from these GCs should be easily detectable for Fermi, while constraints on the total number of MSPs and the nebular B-field may be derived using the IC flux components.Comment: 12 pages, 2 figures, accepted for publication in ApJ

Cyber security education is as essential as “The Three R’s”

Smartphones have diffused rapidly across South African society and constitute the most dominant information and communication technologies in everyday use. That being so, it is important to ensure that all South Africans know how to secure their smart devices. This requires a high level of security awareness and knowledge. As yet, there is no formal curriculum addressing cyber security in South African schools. Indeed, it seems to be left to Universities to teach cyber security principles, and they currently only do this when students take computing-related courses. The outcome of this approach is that only a very small percentage of South Africans, i.e. those who take computing courses at University, are made aware of cyber security risks and know how to take precautions. Moreover, because this group is overwhelmingly male, this educational strategy disproportionately leaves young female South Africans vulnerable to cyber attacks. We thus contend that cyber security ought to be taught as children learn the essential “3 Rs” – delivering requisite skills at University level does not adequately prepare young South Africans for a world where cyber security is an essential skill. Starting to provide awareness and knowledge at primary school, and embedding it across the curriculum would, in addition to ensuring that people have the skills when they need them, also remove the current gender imbalance in cyber security awareness

Fermi Discovery of Gamma-ray Emission from the Globular Cluster Terzan 5

We report the discovery of gamma-ray emission from the Galactic globular cluster Terzan 5 using data taken with the Fermi Gamma-ray Space Telescope, from 2008 August 8 to 2010 January 1. Terzan 5 is clearly detected in the 0.5-20 GeV band by Fermi at ~27\sigma level. This makes Terzan 5 as the second gamma-ray emitting globular cluster seen by Fermi after 47 Tuc. The energy spectrum of Terzan 5 is best represented by an exponential cutoff power-law model, with a photon index of ~1.9 and a cutoff energy at ~3.8 GeV. By comparing to 47 Tuc, we suggest that the observed gamma-ray emission is associated with millisecond pulsars, and is either from the magnetospheres or inverse Compton scattering between the relativistic electrons/positrons in the pulsar winds and the background soft photons from the Galactic plane. Furthermore, it is suggestive that the distance to Terzan 5 is less than 10 kpc and > 10 GeV photons can be seen in the future.Comment: 4 pages, 2 figures; accepted for publication in ApJ

Constraining A General-Relativistic Frame-Dragging Model for Pulsed Radiation from a Population of Millisecond Pulsars in 47 Tucanae using GLAST/LAT

Although only 22 millisecond pulsars (MSPs) are currently known to exist in the globular cluster (GC) 47 Tucanae, this cluster may harbor 30-60 MSPs, or even up to ~200. In this Letter, we model the pulsed curvature radiation (CR) gamma-ray flux expected from a population of MSPs in 47 Tucanae. These MSPs produce gamma-rays in their magnetospheres via accelerated electron primaries which are moving along curved magnetic field lines. A GC like 47 Tucanae containing a large number of MSPs provides the opportunity to study a randomized set of pulsar geometries. Geometry-averaged spectra make the testing of the underlying pulsar model more reliable, since in this case the relative flux uncertainty is reduced by one order of magnitude relative to the variation expected for individual pulsars (if the number of visible pulsars N=100). Our predicted spectra violate the EGRET upper limit at 1 GeV, constraining the product of the number of visible pulsars N and the average integral flux above 1 GeV per pulsar. GLAST/LAT should place even more stringent constraints on this product, and may also limit the maximum average accelerating potential by probing the CR spectral tail. For N=22-200, a GLAST/LAT non-detection will lead to the constraints that the average integral flux per pulsar should be lower by factors 0.03-0.003 than current model predictions.Comment: 10 pages, 2 figures, to appear in the Astrophysical Journal Letter