A common origin for cosmic explosions inferred from calorimetry of GRB030329

Past studies have suggested that long-duration gamma-ray bursts have a 'standard' energy of E(gamma) approximately 10(51) erg in the ultra-relativistic ejecta, after correcting for asymmetries in the explosion ('jets'). But a group of sub-energetic bursts, including the peculiar GRB980425 associated with the supernova SN1998bw (E(gamma) approximately 10(48) erg), has recently been identified. Here we report radio observations of GRB030329 that allow us to undertake calorimetry of the explosion. Our data require a two-component explosion: a narrow (5 degrees opening angle) ultra-relativistic component responsible for the gamma-rays and early afterglow, and a wide, mildly relativistic component that produces the radio and optical afterglow more than 1.5 days after the explosion. The total energy release, which is dominated by the wide component, is similar to that of other gamma-ray bursts, but the contribution of the gamma-rays is energetically minor. Given the firm link of GRB030329 with SN2003dh, our result indicates a common origin for cosmic explosions in which, for reasons not yet understood, the energy in the highest-velocity ejecta is extremely variable.     

Relativistic ejecta from X-ray flash XRF 060218 and the rate of cosmic explosions

Over the past decade, long-duration gamma-ray bursts (GRBs)--including the subclass of X-ray flashes (XRFs)--have been revealed to be a rare variety of type Ibc supernova. Although all these events result from the death of massive stars, the electromagnetic luminosities of GRBs and XRFs exceed those of ordinary type Ibc supernovae by many orders of magnitude. The essential physical process that causes a dying star to produce a GRB or XRF, and not just a supernova, is still unknown. Here we report radio and X-ray observations of XRF 060218 (associated with supernova SN 2006aj), the second-nearest GRB identified until now. We show that this event is a hundred times less energetic but ten times more common than cosmological GRBs. Moreover, it is distinguished from ordinary type Ibc supernovae by the presence of 10(48) erg coupled to mildly relativistic ejecta, along with a central engine (an accretion-fed, rapidly rotating compact source) that produces X-rays for weeks after the explosion. This suggests that the production of relativistic ejecta is the key physical distinction between GRBs or XRFs and ordinary supernovae, while the nature of the central engine (black hole or magnetar) may distinguish typical bursts from low-luminosity, spherical events like XRF 060218.     

Rich Pictures: Collaborative Communication Through Icons

A visual language of pictures, such as the rich picture used in the Soft System Methodology, offers a way of global communication that far exceeds the limitations of text and speech. Simple graphics can be rapidly communicated, processed and transmitted within a large and culturally diverse constituency. This paper looks at the benefits and interpretative risks when using rich pictures for system understanding. The aim of this paper is twofold: firstly to report upon an observation of a large scale collaborative diagramming workshop and compare the resulting pictures with a previous workshop study. Secondly, to develop further ongoing research which suggests rich picture construction can be aided by providing an icon legend. This paper compares 2 rich picture workshops: the diagramming workshop at the Open University eSTEeM Diagramming Colloquium in March 2012 and a workshop held in Heriot Watt University in February 2012. The comparative results are set against the ongoing empirically grounded rich picture research within Heriot-Watt University in Scotland. Preliminary results suggest there are a set of distinguishable icons and shapes that are generic across all rich pictures regardless of domain. Further analysis of the early results suggests a natural intrinsic grammar is manifested within rich pictures in terms of relationships, icons, context and connectors.     

The Price of Success: Sociologist Harry Alpert,the NSF's First Social Science Policy Architect

Harry Alpert (1912–1977), the US sociologist, is best-known for his directorship of the National Science Foundation's social science programme in the 1950s. This study extends our understanding of Alpert in two main ways: first, by examining the earlier development of his views and career. Beginning with his 1939 biography of Emile Durkheim, we explore the early development of Alpert's views about foundational questions concerning the scientific status of sociology and social science more generally, proper social science methodology, the practical value of social science, the academic institutionalisation of sociology, and the unity-of-science viewpoint. Second, this paper illuminates Alpert's complex involvement with certain tensions in mid-century US social science that were themselves linked to major transformations in national science policy, public patronage, and unequal relations between the social and natural sciences. We show that Alpert's views about the intellectual foundations, practical relevance, and institutional standing of the social sciences were, in some important respects, at odds with his NSF policy work. Although remembered as a quantitative evangelist and advocate for the unity-of-science viewpoint, Alpert was in fact an urbane critic of natural-science envy, social scientific certainty, and what he saw as excessive devotion to quantitative methods.     

Birth of a relativistic outflow in the unusual γ-ray transient Swift J164449.3+573451

Active galactic nuclei, which are powered by long-term accretion onto central supermassive black holes, produce relativistic jets with lifetimes of at least one million years, and the observation of the birth of such a jet is therefore unlikely. Transient accretion onto a supermassive black hole, for example through the tidal disruption of a stray star, thus offers a rare opportunity to study the birth of a relativistic jet. On 25 March 2011, an unusual transient source (Swift J164449.3+573451) was found, potentially representing such an accretion event. Here we report observations spanning centimetre to millimetre wavelengths and covering the first month of evolution of a luminous radio transient associated with Swift J164449.3+573451. The radio transient coincides with the nucleus of an inactive galaxy. We conclude that we are seeing a newly formed relativistic outflow, launched by transient accretion onto a million-solar-mass black hole. A relativistic outflow is not predicted in this situation, but we show that the tidal disruption of a star naturally explains the observed high-energy properties and radio luminosity and the inferred rate of such events. The weaker beaming in the radio-frequency spectrum relative to γ-rays or X-rays suggests that radio searches may uncover similar events out to redshifts of z?≈?6.