Massive stars exploding in a He-rich circumstellar medium - III. SN 2006jc: infrared echoes from new and old dust in the progenitor CSM

We present near- (NIR) and mid-infrared (MIR) photometric data of the Type Ibn supernova (SN) 2006jc obtained with the United Kingdom Infrared Telescope (UKIRT), the Gemini North Telescope and the Spitzer Space Telescope between days 86 and 493 post-explosion. We find that the IR behaviour of SN 2006jc can be explained as a combination of IR echoes from two manifestations of circumstellar material. The bulk of the NIR emission arises from an IR echo from newly condensed dust in a cool dense shell (CDs) produced by the interaction of the ejecta Outward shock with a dense shell of circumstellar material ejected by the progenitor in a luminous blue variable (LBV)-like outburst about two years prior to the SN explosion. The CDs dust mass reaches a modest 3.0 x 10(-4) M-circle dot by day 230. While dust condensation within a CDs formed behind the ejecta inward shock has been proposed before for one event (SN 1998S), SN 2006jc is the first one showing evidence for dust condensation in a CDs formed behind the ejecta outward shock in the circumstellar material. At later epochs, a substantial and growing contribution to the IR fluxes arises from an IR echo from pre-existing dust in the progenitor wind. The mass of the pre-existing circumstellar medium (CSM) dust is at least similar to 8 x 10(-3) M-circle dot. This paper therefore adds to the evidence that mass-loss from the progenitors of core-collapse SNe could be a major source of dust in the Universe. However, yet again, we see no direct evidence that the explosion of an SN produces anything other than a very modest amount of dust.

Do conflict management systems matter?

The most influential current idea in the theory of conflict management concerns the design features and supposed superior outcomes of conflict management systems combining interest-based and rights-based practices for resolving conflict in organizations. Yet much of the literature in the area is highly prescriptive and draws heavily either on exemplary case studies or descriptive data. Using focus groups of HR practitioners and experts in conflict resolution to develop a questionnaire covering the main conflict management practices associated with the theory of conflict management systems, the study analyzes data from a survey of firms in the Republic of Ireland to examine quantitatively the effects of conflict management systems on organizational outcomes. While proactive line management and supervisory engagement in conflict resolution as a key dimension of conflict management systems is found to be positively associated with a range of organizational outcomes, no evidence is found for the kind of system effects proposed in the theoretical and prescriptive literature. © 2012 Wiley Periodicals, Inc.

Why multiples matter: Reconceptualising the population referred to child and family social workers

Building on a body of previous research by the author and colleagues in relation to multiple adverse childhood experiences (MACE), this paper addresses the question of ‘why multiples matter’ in relation to issues of cumulative adversity. Illustrative evidence is drawn from three research domains, epidemiology, multiple services use and child maltreatment to demonstrate the collective weight of evidence to suggest a targeting of those children and families experiencing multiple adversities to diminish the effects of such adversities realised across the life-course. Whilst the history of previous largely unsuccessful attempts to widen the range of children prioritised for intervention by child and family social workers might lead to pessimism in relation to their ability to respond to a MACE informed public health agenda, there are clear possibilities for developing agency structures, assessment tools and social work practices directed toward meeting the needs of those sub populations already prioritised by social workers: namely Children in Need, Children in need of Protection and Looked after Children.

Chemistry in oxygen-rich circumstellar envelopes

We have considered the chemistry occuring in the circumstellar envelope surrounding an oxygen-rich AGE star and have specifically modelled 4 sources; R Dor, TX Cam, OH231.8+4.2 and IK Tau. Methane has been assumed to be a parent molecule and the resulting carbon chemistry is investigated. We find that carbon chain molecules up to C2H4 can be abundant as can CH3CN and CH3OH. Our model extends previous work by including the chemistry of silicon, chlorine and phosphorus. The presence of CH4 as a parent and hence its daughter species CH3 and CH3+ leads to other carbon-bearing species such as H2CS, SiCH2, H2CN and CCl.

Chemical evolution in the circumstellar structure of B5 IRS1

The B5 dark cloud has been identified as a site of low-mass star formation. We report a survey of a selection of the molecular species modelled by the B5 dynamical and chemical model of Charnley et al. at the positions of circumstellar HCN clumps in B5 IRS1. All of the key species observed yield either abundances or upper limits to abundances below both the standard and the predicted values, appearing to show evidence of depletion and/or destruction if the transitions observed are thermalized. Our results are not in good agreement with the model, and they bring into question the interpretation of the structure of B5 IRS1 proposed by Fuller et al. It was expected that HCN clump C might exhibit a higher excitation than HCN clump A, since it appeared to be located within the blueshifted molecular outflow. However, there is no significant difference observed between the two clumps, suggesting that the near-infrared and optical nebulosity is evidence of a reflection nebula rather than shocked material in the outflow. Finally, it is observed that our results are more consistent with gas-grain models than with those models excluding gas-grain interaction.

A NEW CHEMICAL-MODEL OF THE CIRCUMSTELLAR ENVELOPE SURROUNDING IRC+10216

A new chemical model of the circumstellar envelope surrounding the carbon-rich star IRC+10216 has been developed. This model incorporates a variety of newly measured rapid neutral-neutral reactions between carbon atoms and hydrocarbons and between the radical CN and a variety of stable neutral molecules. In addition, other neutral-neutral reactions in the above two classes or involving atoms such as N or radicals such as C(2n)H have been included with large rate coefficients although they have not yet been studied in the laboratory. Unlike the interstellar case, where the inclusion of these neutral-neutral reactions destroys molecular complexity, our model results for IRC+10216 show that sufficient abundances of large hydrocarbon radicals and cyanpolyynes can be produced to explain observations. We also discuss the formation of H2CN and NH2CN, two potentially observable molecules in IRC+10216.

FORMALDEHYDE IN OXYGEN-RICH CIRCUMSTELLAR ENVELOPES

We test the hypothesis that methane is the source of the carbon observed in carbon-bearing molecules around oxygen-rich stars, by considering the synthesis of formaldehyde which is formed in the reaction between oxygen atoms and methyl radicals. We find that, provided that the parent methane abundance is large enough, millimetre-wave emission lines of H2CO should be detectable in such stars. We also consider the formation of other species, notably H2CN and H2CS, from methyl radicals, but conclude that they will be at least one order of magnitude less abundant than H2CO and therefore not detectable with current instrumentation.

Long hours in paid and domestic work and subsequent sickness absence: does control over daily working hours matter?

Objectives: To explore the associations of working hours ( paid, domestic, commuting, and total) with sickness absence, and to examine whether these associations vary according to the level of employee control over daily working hours.

Massive stars exploding in a He-rich circumstellar medium - I. Type Ibn (SN 2006jc-like) events

We present new spectroscopic and photometric data of the Type Ibn supernovae 2006jc, 2000er and 2002ao. We discuss the general properties of this recently proposed supernova family, which also includes SN 1999cq. The early-time monitoring of SN 2000er traces the evolution of this class of objects during the first few days after the shock breakout. An overall similarity in the photometric and spectroscopic evolution is found among the members of this group, which would be unexpected if the energy in these core-collapse events was dominated by the interaction between supernova ejecta and circumstellar medium. Type Ibn supernovae appear to be rather normal Type Ib/c supernova explosions which occur within a He-rich circumstellar environment. SNe Ibn are therefore likely produced by the explosion of Wolf-Rayet progenitors still embedded in the He-rich material lost by the star in recent mass-loss episodes, which resemble known luminous blue variable eruptions. The evolved Wolf-Rayet star could either result from the evolution of a very massive star or be the more evolved member of a massive binary system. We also suggest that there are a number of arguments in favour of a Type Ibn classification for the historical SN 1885A (S-Andromedae), previously considered as an anomalous Type la event with some resemblance to SN 1991bg.