John Mair

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Observational Constraints on Pulsar Wind Theories

Two-dimensional, relativistic, MHD simulations of pulsar-wind powered nebulae provide strong constraints on the properties of the winds themselves. In particular, they confirm that Poynting flux must be converted into particle energy close to or inside the termination shock front, emphasising the puzzle known as the $\sigma$ paradox. To distinguish between the different possible resolutions of this paradox, additional observational constraints are required. In this paper, I briefly discuss two recents developments in this respect: the modelling of high time-resolution optical polarimetry of the Crab pulsar, and the detection of the pulsar/Be star binary PSR 1259-63 in TeV energy gamma-rays.Comment: Paper presented at the workshop on "Stellar End Products", Granada 13-15 April 200

Catalogue of Be/X-ray binary systems in the Small Magellanic Cloud: X-ray, optical & IR properties

This is a catalogue of approximately 70 X-ray emitting binary systems in the Small Magellanic Cloud (SMC) that contain a Be star as the mass donor in the system and a clear X-ray pulse signature from a neutron star. The systems are generally referred to as Be/Xray binaries. It lists all their known binary characteristics (orbital period, eccentricity), the measured spin period of the compact object, plus the characteristics of the Be star (spectral type, size of the circumstellar disk, evidence for NRP behaviour). For the first time data from the Spitzer Observatory are combined with ground-based data to provide a view of these systems out into the far-IR. Many of the observational parameters are presented as statistical distributions and compared to other similar similar populations (eg isolated Be & B stars) in the SMC, and to other Be/X-ray systems in the Milky Way. In addition previous important results are re-investigated using this excellently homogeneous sample. In particular, the evidence for a bi-modality in the spin period distribution is shown to be even stronger than first proposed, and the correlation between orbital period and circumstellar disk size seen in galactic sources is shown to be clearly present in the SMC systems and quantised for the first time.Comment: 10 pages, 10 figures, 4 tables. Accepted for publication in MNRA

Climate change: carbon losses in the Alps

The response of the terrestrial carbon cycle to global change is one of the main uncertainties in current climate change predictions1. Most terrestrial carbon is held in soils as organic matter derived from the decay of plant material (Fig. 1). Soil organic matter accounts for roughly three times more carbon than living vegetation, and for more carbon than vegetation and the atmosphere combined. Because elevated atmospheric CO2 concentrations have a fertilizing effect on plant growth, anthropogenic CO2 emissions have triggered increases in the land carbon sink2. However, models predict that other factors — such as water and nutrients — will eventually become limiting to plant growth, and hence to the land carbon sink. In contrast, the turnover of soil organic matter producing CO2 is expected to increase as the Earth warms. As a result, simulations using coupled carbon–climate models predict that the land surface will become a net source of CO2 before the end of the century, leading to a feedback loop between climate and soil carbon losses: increased emissions of CO2 from soil organic matter will lead to enhanced warming, which may then feedback to cause further soil organic matter losses. Prietzel and colleagues3, writing in Nature Geoscience, now provide evidence that warming has already caused a decline in soil organic matter in the German Alps

An Annotated Checklist of Scarab Beetles (Coleoptera: Scarabaeidae) from Northeastern Iowa

A survey of scarab beetles (Coleoptera: Scarabaeidae) was conducted during 2009 in the geographically distinct area of Winneshiek and Allamakee counties in extreme Northeast Iowa. Four plant communities distributed among 10 locations, including tallgrass prairie, mixed grassland and forest, oak-hickory forest, and pasture were sampled during 2009 using black light traps, banana- beer traps, rodent burrow pitfalls, manure-baited pitfalls, and gleaning. Additionally, previous specimen records were examined. Forty-nine scarab species were documented for Winneshiek and Allamakee counties, including five species not previously reported in Iowa. Mixed grassland and forest habitat contained the greatest scarab species richness (n=31); black light trapping yielded the greatest number of individual beetles and collected the most species

The "sigma" problem of the Crab pulsar wind

The conversion of the Crab pulsar wind from one dominated by Poynting flux close to the star to one dominated by particle-born energy at the termination shock is considered. The idea put forward by Coroniti (1990) and criticised by Lyubarsky & Kirk (2001) that reconnection in a striped wind is responsible, is generalised to include faster prescriptions for the a priori unknown dissipation rate. Strong acceleration of the wind is confirmed, and the higher dissipation rates imply complete conversion of Poynting flux into particle-born flux within the unshocked wind.Comment: 4 pages, to appear in "Young Neutron Stars and Their Environments" (IAU Symposium 218, ASP Conference Proceedings), eds F. Camilo and B. M. Gaensle