204 research outputs found

    Return of the King: time-series photometry of FO Aquarii’s initial recovery from its unprecedented 2016 low state

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    In 2016 May, the intermediate polar FO Aqr was detected in a low state for the first time in its observational history. We report time-resolved photometry of the system during its initial recovery from this faint state. Our data, which includes high-speed photometry with cadences of just 2 s, show the existence of very strong periodicities at 22.5 and 11.26 minutes, equivalent to the spin–orbit beat frequency and twice its value, respectively. A pulse at the spin frequency is also present but at a much lower amplitude than is normally observed in the bright state. By comparing our power spectra with theoretical models, we infer that a substantial amount of accretion was stream-fed during our observations, in contrast to the disk-fed accretion that dominates the bright state. In addition, we find that FO Aqr's rate of recovery has been unusually slow in comparison to rates of recovery seen in other magnetic cataclysmic variables, with an e-folding time of 115 ± 7 days. The recovery also shows irregular variations in the median brightness of as much as 0.2 mag over a 10-day span. Finally, we show that the arrival times of the spin pulses are dependent upon the system's overall brightness

    Imagining transitions in old age through the visual matrix method: thinking about what is hard to bear

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    Dominant discourses of ageing are often confined to what is less painful to think about and therefore idealise or denigrate ageing and later life. We present findings from an exploratory psychosocial study, in a Nordic context into three later-life transitions: from working life to retirement, from mental health to dementia, and from life to death. Because, for some, these topics are hard to bear, and therefore defended against and routinely excluded from everyday awareness, we used a method led by imagery and affect - the Visual Matrix - to elicit participants’ free associative personal and collective imagination. Through analysis of data extracts, on the three transitions, we illustrate oscillations between defending against the challenges of ageing and realism in facing the anxieties it can provoke. A recurring theme includes the finality of individual life and the inter-generational continuity, which together link life and death, hope and despair, separation and connectedness

    WO-Type Wolf-Rayet Stars: the Last Hurrah of Massive Star Evolution

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    Are WO-type Wolf Rayet (WR) stars in the final stage of massive star evolution before core-collapse? Although WC- and WO-type WRs have very similar spectra, WOs show a much stronger O VI λλ\lambda \lambda3811,34 emission-line feature. This has usually been interpreted to mean that WOs are more oxygen rich than WCs, and thus further evolved. However, previous studies have failed to model this line, leaving the relative abundances uncertain, and the relationship between the two types unresolved. To answer this fundamental question, we modeled six WCs and two WOs in the LMC using UV, optical, and NIR spectra with the radiative transfer code CMFGEN in order to determine their physical properties. We find that WOs are not richer in oxygen; rather, the O VI feature is insensitive to the abundance. However, the WOs have a significantly higher carbon and lower helium content than the WCs, and hence are further evolved. A comparison of our results with single-star Geneva and binary BPASS evolutionary models show that while many properties match, there is more carbon and less oxygen in the WOs than either set of evolutionary model predicts. This discrepancy may be due to the large uncertainty in the 12^{12}C+4^4He16\rightarrow^{16}O nuclear reaction rate; we show that if the Kunz et al. rate is decreased by a factor of 25-50%, then there would be a good match with the observations. It would also help explain the LIGO/VIRGO detection of black holes whose masses are in the theoretical upper mass gap.Comment: 55 pages, 22 figures, Accepted into Ap

    The willingness to pay for dusky kob (Argyrosomus japonicus) restocking: using recreational linefishing licence fees to fund stock enhancement in South Africa

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    The economic feasibility of stock enhancement of Argyrosomus japonicus in South Africa was investigated using a willingness-to-pay (WTP) survey. The pilot study provides a unique example of the use of the contingent valuation method as a valuation tool for a proposed stock enhancement programme. An increase in the cost of a recreational fishing permit is used as a potential vehicle of payment. The median value of the maximum that fishers were willing to pay for a recreational fishing permit was R155 (South African Rand) for frequent fishers and R100 for non-frequent fishers. Analysis showed that a fee of more than R100 excluded up to 50% of anglers from the fishery, but that a fee of R100 excluded only 28% of recreational anglers and would generate an additional R12 million annually from the sale of recreational fishing permits. The estimated costs of set-up and running of a stock enhancement programme are substantially lower than this, suggesting that stock enhancement may be an economically feasible management option that deserves more investigation. The WTP method itself produces robust results and is likely to be an effective tool in the management of the marine environment

    Values - reviewing the construct and drawing implications for values work in organisation and leadership. Kap. 2

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    I: H.Askeland, G. Espedal, B. Jelstad Løvaas & S. Sirris (Eds.), Understanding values work : Institutional perspectives in organizations and leadershipThis chapter outlines the trajectory of values, particularly within streams of organisational institutionalism, in order to analyse its application to values work in organisation and leadership. Conveying a frame for discussing values work, it aims at clarifying how to conceptualise the term values. Discussing classic and recent contributions, the chapter proposes seeing values as individual and collective conceptions of desirable trans-situational behaviours, objectives and ideals, serving to guide or valuate practice. Despite being an essential part of defining organisational institutionalism, and its sub-streams, values are seldom explicated. Utilising values in organisational and leadership research requires attention to their situatedness in contexts, and this chapter argues they are salient to organisations operating in pluralistic institutional environment. Studying values work, attention should be given to who and how such work is performed.publishedVersio
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