The supernova remnant CTB 37B and its associated magnetar CXOU J171405.7-381031: evidence for a magnetar-driven remnant

We discuss in this Letter the association of the candidate magnetar CXOU J171405.7-381031 with the supernova remnant CTB 37B. The recent detection of the period derivative of the object allowed an estimation of a young characteristic age of only $\sim 1000 yr$. This value is too small to be compatible even with the minimum radius of the remnant $\geq 10 pc$, the value corresponding to the {\it lower} limit of the estimated distance of $10.2 \pm 3.5 kpc$, unless the true distance happens to be even smaller than the lower limit. We argue that a consistent scenario for the remnant origin, in which the latter is powered by the energy injected by a young magnetar, is indeed more accurate to explain the young age, and points out to its non-standard (i.e. magnetar-driven) nature.Comment: 6 pp., 1 figure, to appear in RAA Letter

Footprints of the Newly-Discovered Vela Supernova in Antarctic Ice Cores?

The recently-discovered, nearby young supernova remnant in the southeast corner of the older Vela supernova remnant may have been seen in measurements of nitrate abundances in Antarctic ice cores. Such an interpretation of this twenty-year-old ice-core data would provide a more accurate dating of this supernova than is possible purely using astrophysical techniques. It permits an inference of the supernova4s ${}^{44}$Ti yield purely on an observational basis, without reference to supernova modelling. The resulting estimates of the supernova distance and light-arrival time are 200 pc and 700 years ago, implying an expansion speed of 5,000 km/s for the supernova remnant. Such an expansion speed has been argued elsewhere to imply the explosion to have been a 15 $M_\odot$ Type II supernova. This interpretation also adds new evidence to the debate as to whether nearby supernovae can measurably affect nitrate abundances in polar ice cores.Comment: 12 pages, TeX, 2 enclosed figures. Updated references, and more detailed discussion of how inferences are made of supernova propertie

Trust in Crowds: probabilistic behaviour in anonymity protocols

The existing analysis of the Crowds anonymity protocol assumes that a participating member is either ‘honest’ or ‘corrupted’. This paper generalises this analysis so that each member is assumed to maliciously disclose the identity of other nodes with a probability determined by her vulnerability to corruption. Within this model, the trust in a principal is defined to be the probability that she behaves honestly. We investigate the effect of such a probabilistic behaviour on the anonymity of the principals participating in the protocol, and formulate the necessary conditions to achieve ‘probable innocence’. Using these conditions, we propose a generalised Crowds-Trust protocol which uses trust information to achieves ‘probable innocence’ for principals exhibiting probabilistic behaviour

Momentum Scale Expansion of Sharp Cutoff Flow Equations

We show how the exact renormalization group for the effective action with a sharp momentum cutoff, may be organised by expanding one-particle irreducible parts in terms of homogeneous functions of momenta of integer degree (Taylor expansions not being possible). A systematic series of approximations -- the $O(p^M)$ approximations -- result from discarding from these parts, all terms of higher than the $M^{\rm th}$ degree. These approximations preserve a field reparametrization invariance, ensuring that the field's anomalous dimension is unambiguously determined. The lowest order approximation coincides with the local potential approximation to the Wegner-Houghton equations. We discuss the practical difficulties with extending the approximation beyond $O(p^0)$.Comment: 31 pages including 5 eps figures, uses harvmac and epsf. Minor additions -- not worth the bandwidth if you already have a cop

Unveiling the nature of six HMXBs through IR spectroscopy

The International Gamma-Ray Astrophyiscs Laboratory (INTEGRAL) is discovering a large number of new hard X-ray sources, many of them being HMXBs. The identification and spectral characterization of their optical/infrared counterparts is a necessary step to undertake detailed study of these systems. In particular, the determination of the spectral type is crucial in the case of the new class of Supergiant Fast X-ray Transients (SFXTs), which show X-ray properties common to other objects. We used the ESO/NTT SofI spectrograph to observe proposed IR counterparts to HMXBs, obtaining Ks medium resolution spectra (R = 1320) with a S/N >= 100. We classified them through comparison with published atlases. We were able to spectrally classify the six sources. This allowed us to ascribe one of them to the new class of SFXTs and confirm the membership of two sources to this class. We confirmed the spectral classification, derived from optical spectroscopy, of a known system, 4U 1907-09, showing for the first time its infrared spectrum. The spectral classification was also used to estimate the distance of the sources. We compared the extinction as derived from X-ray data with effective interstellar extinction obtained from our data, discussing the absorption component due to the circumstellar environment, which we observed in four systems; in particular, intrinsic absorption seems to emerge as a typical feature of the entire class of SFXTs.Comment: 8 pages, 6 figures, 3 tables, accepted for publication in Astronomy & Astrophysic

Investigating the dynamics of resilience and greenhouse gas performance of pastoral cattle systems in southern Ethiopia

Context: Pastoral and agro-pastoral (PAP) systems in East Africa face a range of challenges including increased climate variability. Various measures have been proposed to improve the resilience of pastoral/agro-pastoral (PAP) systems to drought. However, identifying the most effective measure for a given system and location is complicated, and tools are required to appraise measures on a consistent basis.Objective: This paper develops a model of a PAP system and uses it to assess the effects of four measures (Index-based livestock insurance, IBLI; Commercial destocking with an early warning system, EWS; Rangeland restoration, RR; Fodder planting, FP) on the resilience of the PAP system. It also quantifies the greenhouse gas (GHG) effects of the measures, thereby identifying potential trade-offs and synergies between the policy objectives of resilience and climate smart agriculture (CSA).Methods: A dynamic model of the Borena pastoral cattle system was developed to undertake the analysis. At its core is a herd model that calculates the changes in cattle population over time. Feed availability and drought occurrence affect fertility and mortality rates, which in turn determine the population and (meat and milk) production. A suite of indicators covering the three dimensions of CSA (increasing productivity, enhancing resilience and reducing GHG emissions) were developed, and used to compare the situation with and without measures.Results and discussions: Destocking with an early warning system provides the biggest increases (relative to the no measure situation) in production and profit, due to the way it changes the herd size and structure. It maintains a larger herd than any of the other measures, and a greater proportion of the herd are adult females. Fodder planting and rangeland restoration provide moderate increases in production and profit. Index-based livestock insurance provides a moderate increase in protein production, but has no effect on profit, as it is designed to reduce risk rather than increase productivity or profit, at least in the short term.All of the measures increase the total emissions relative to the no measure scenario. In terms of the three dimensions of climate-smart agriculture, IBLI leads to some improvements in productivity and resilience but leads to large increases in total emissions, and modest increases in emissions intensity (EI). EWS leads to large increases in productivity and resilience. However, it also leads to large increases in total emissions and a mixed effect on EI. FP and RR improve productivity and increase total emissions, while having little effect on EI or resilience.Significance: This paper illustrates the way in which systems dynamic model can be used to appraise measures designed to improve resilience. The result identify potential synergies and tensions between the goals of resilience and climate smart agriculture, and raises the question of whether fully climate-smart goals are viable in these systems

The impact of health insurance on cancer care in disadvantaged communities

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136387/1/cncr30431.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136387/2/cncr30431_am.pd

Clustering between high-mass X-ray binaries and OB associations in the Milky Way

We present the first direct measurement of the spatial cross-correlation function of high-mass X-ray binaries (HMXBs) and active OB star-forming complexes in the Milky Way. This result relied on a sample containing 79 hard X-ray selected HMXBs and 458 OB associations. Clustering between the two populations is detected with a significance above 7-sigmas for distances < 1 kpc. Thus, HMXBs closely trace the underlying distribution of the massive star-forming regions that are expected to produce the progenitor stars of HMXBs. The average offset of 0.4+-0.2 kpc between HMXBs and OB associations is consistent with being due to natal kicks at velocities of the order of 100+-50 km/s. The characteristic scale of the correlation function suggests an average kinematical age (since the supernova phase) of ~4 Myr for the HMXB population. Despite being derived from a global view of our Galaxy, these signatures of HMXB evolution are consistent with theoretical expectations as well as observations of individual objects.Comment: 18 pages, 10 figures, 3 tables, accepted for publication in Ap