Iron Opacity and the Pulsar of Supernova 1987A

Neutron stars formed in Type II supernovae are likely to be initially obscured by late-time fallback. Although much of the late-time fallback is quickly accreted via neutrino cooling, some material remains on the neutron star, forming an atmosphere which slowly accretes through photon emission. In this paper, we derive structure equations of the fallback atmosphere and present results of one-dimensional simulations of that fallback. The atmosphere remaining after neutrino cooling becomes unimportant (less than the Compton Eddington limit) is only a fraction of the total mass accreted (10^-8 of the accreted mass or 10^-9 solar masses.) Recombined iron dominates the opacity in the outer regions leading to an opacity 1000-10,000 times higher than that of electron scattering alone. The resultant photon emission of the remnant atmosphere is limited to 1/1000th the Compton Eddington Luminosity. The late-time evolution of this system leads to the formation of a photon-driven wind from the accretion of the inner portion of the atmosphere, leaving, for most cases, a bare neutron star on timescales shorter than a year. The degenerate remnant of 1987a may not be a black hole. Instead, the fallback material may have already accreted or blown off in the accretion-driven wind. If the neutron star has either a low magnetic field or a low rotational spin frequency, we would not expect to see the neutron star remnant of 1987a.Comment: 15 pages text + 8 figures, accepted by Ap

Statistics of convective cloud turbulence from a comprehensive turbulence retrieval method for radar observations

Turbulent mixing processes are important in determining the evolution of convective clouds,and the production of convective precipitation. However, the exact nature of these impacts remains uncertain due to limited observations. Model simulations show that assumptions made in parametrizing turbulence can have a marked effect on the characteristics of simulated clouds. This leads to significant uncertainty in forecasts from convection‐permitting numerical weather prediction (NWP) models. This contribution presents a comprehensive method to retrieve turbulence using Doppler weather radar to investigate turbulence in observed clouds. This method involves isolating the turbulent component of the Doppler velocity spectrum width, expressing turbulence intensity as an eddy dissipation rate, ϵ. By applying this method throughout large datasets of observations collected over the southern United Kingdom using the (0.28° beam‐width) Chilbolton Advanced Meteorological Radar (CAMRa), statistics of convective cloud turbulence are presented. Two contrasting case days are examined: a shallow “shower” case, and a “deep convection” case, exhibiting stronger and deeper updraughts. In our observations, ϵ generally ranges from 10−3 to 10−1 m2/s3, with the largest values found within, around and above convective updraughts. Vertical profiles of ϵ suggest that turbulence is much stronger in deep convection; 95th percentile values increase with height from 0.03 to 0.1 m2/s3, compared to approximately constant values of 0.02–0.03 m2/s3 throughout the depth of shower cloud. In updraught regions on both days, the 95th percentile of ϵ has significant (p < 10−3) positive correlations with the updraught velocity, and the horizontal shear in the updraught velocity, with weaker positive correlations with updraught dimensions. The ϵ‐retrieval method presented considers a very broad range of conditions, providing a reliable framework for turbulence retrieval using high‐resolution Doppler weather radar. In applying this method across many observations, the derived turbulence statistics will form the basis for evaluating the parametrization of turbulence in NWP models

What Can the Accretion Induced Collapse of White Dwarfs Really Explain?

The accretion induced collapse (AIC) of a white dwarf into a neutron star has been invoked to explain gamma-ray bursts, Type Ia supernovae, and a number of problematic neutron star populations and specific binary systems. The ejecta from this collapse has also been claimed as a source of r-process nucleosynthesis. So far, most AIC studies have focussed on determining the event rates from binary evolution models and less attention has been directed toward understanding the collapse itself. However, the collapse of a white dwarf into a neutron star is followed by the ejection of rare neutron-rich isotopes. The observed abundance of these chemical elements may set a more reliable limit on the rate at which AICs have taken place over the history of the galaxy. In this paper, we present a thorough study of the collapse of a massive white dwarf in 1- and 2-dimensions and determine the amount and composition of the ejected material. We discuss the importance of the input physics (equation of state, neutrino transport, rotation) in determining these quantities. These simulations affirm that AICs are too baryon rich to produce gamm-ray bursts and do not eject enough nickel to explain Type Ia supernovae (with the possible exception of a small subclass of extremely low-luminosity Type Ias). Although nucleosynthesis constraints limit the number of neutron stars formed via AICs to <0.1% of the total galactic neutron star population, AICs remain a viable scenario for forming systems of neutron stars which are difficult to explain with Type II core-collapse supernovae.Comment: Latex File, aaspp4 style, 18 pages total (5 figures), accepted by Ap

Professional resilience in GPs working in areas of socio-economic deprivation: a qualitative study

Background GPs working in areas of high socioeconomic deprivation face particular challenges, and are at increased risk of professional burnout. Understanding how GPs working in such areas perceive professional resilience is important in order to recruit and retain a GP workforce in these areas. Aim To understand how GPs working in areas of high socioeconomic deprivation consider professional resilience. Design and setting A qualitative study of GPs practising in deprived areas within one primary care region of England. Method In total, 14 individual interviews and one focus group of eight participants were undertaken, with sampling to data saturation. A framework approach was used for data analysis. Results Participants described three key themes relating to resilience. First, resilience was seen as involving flexibility and adaptability. This involved making trade-offs in order to keep going, even if this was imperfect. Second, resilience was enacted through teams rather than through individual strength. Third, resilience required the integration of personal and professional values rather than keeping the two separate. This dynamic adaptive view, with an emphasis on the importance of individuals within teams rather than in isolation, contrasts with the discourse of resilience as a personal characteristic, which should be strengthened at the individual level. Conclusion Professional resilience is about more than individual strength. Policies to promote professional resilience, particularly in settings such as areas of high socioeconomic deprivation, must recognise the importance of flexibility, adaptability, working as teams, and successful integration between work and personal values

The First New Zealanders: Patterns of Diet and Mobility Revealed through Isotope Analysis

Direct evidence of the environmental impact of human colonization and subsequent human adaptational responses to new environments is extremely rare anywhere in the world. New Zealand was the last Polynesian island group to be settled by humans, who arrived around the end of the 13th century AD. Little is known about the nature of human adaptation and mobility during the initial phase of colonization. We report the results of the isotopic analysis (carbon, nitrogen and strontium) of the oldest prehistoric skeletons discovered in New Zealand to assess diet and migration patterns. The isotope data show that the culturally distinctive burials, Group 1, had similar diets and childhood origins, supporting the assertion that this group was distinct from Group 2/3 and may have been part of the initial colonizing population at the site. The Group 2/3 individuals displayed highly variable diets and likely lived in different regions of the country before their burial at Wairau Bar, supporting the archaeological evidence that people were highly mobile in New Zealand since the initial phase of human settlement.: University of Otago Research Grant (http://www.otago.ac.nz/research/otago004140.html); A grant-in-aid by the School of Medical Sciences, University of Otago (http://osms.otago.ac.nz/); The Mason Foundation (http://research-hub.griffith.edu.au/display/fosc_MASONG); Royal Society of New Zealand Marsden Fund (http://www.royalsociety.org.nz/programmes/funds/marsden/) grant number UOO0711. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Differential diagnosis of autism, attachment disorders, complex post-traumatic stress disorder and emotionally unstable personality disorder: A Delphi study

Individuals diagnosed with autism, attachment disorders, emotionally unstable personality disorder (EUPD) or complex post-traumatic stress disorder (CPTSD) can present with similar features. This renders differential and accurate diagnosis of these conditions difficult, leading to diagnostic overshadowing and misdiagnosis. The purpose of this study was to explore professionals' perspectives on the differential diagnosis of autism, attachment disorders and CPTSD in young people; and of autism, CPTSD and EUPD in adults. A co-produced three-round Delphi study gathered information through a series of questionnaires from 106 international professionals with expertise in assessing and/or diagnosing at least one of these conditions. To provide specialist guidance and data triangulation, working groups of experts by experience, clinicians and researchers were consulted. Delphi statements were considered to have reached consensus if at least 80% of participants were in agreement. Two hundred and seventy-five Delphi statements reached consensus. Overlapping and differentiating features, methods of assessment, difficulties encountered during differential diagnosis and suggestions for improvements were identified. The findings highlight current practices for differential diagnosis of autism, attachment disorders, CPTSD and EUPD in young people and adults. Areas for future research, clinical and service provision implications, were also identified