| 1. |
- Thomas, HS, et al.
(författare)
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- 2019
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swepub:Mat__t
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| 4. |
- Smartt, S. J., et al.
(författare)
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A kilonova as the electromagnetic counterpart to a gravitational-wave source
- 2017
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 551:7678, s. 75-
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Tidskriftsartikel (refereegranskat)abstract
- Gravitational waves were discovered with the detection of binary black-hole mergers(1) and they should also be detectable from lower-mass neutron-star mergers. These are predicted to eject material rich in heavy radioactive isotopes that can power an electromagnetic signal. This signal is luminous at optical and infrared wavelengths and is called a kilonova(2-5). The gravitational-wave source GW170817 arose from a binary neutron-star merger in the nearby Universe with a relatively well confined sky position and distance estimate(6). Here we report observations and physical modelling of a rapidly fading electromagnetic transient in the galaxy NGC 4993, which is spatially coincident with GW170817 and with a weak, short.-ray burst(7,8). The transient has physical parameters that broadly match the theoretical predictions of blue kilonovae from neutron-star mergers. The emitted electromagnetic radiation can be explained with an ejected mass of 0.04 +/- 0.01 solar masses, with an opacity of less than 0.5 square centimetres per gram, at a velocity of 0.2 +/- 0.1 times light speed. The power source is constrained to have a power-law slope of -1.2 +/- 0.3, consistent with radioactive powering from r-process nuclides. (The r-process is a series of neutron capture reactions that synthesise many of the elements heavier than iron.) We identify line features in the spectra that are consistent with light r-process elements (atomic masses of 90-140). As it fades, the transient rapidly becomes red, and a higher-opacity, lanthanide-rich ejecta component may contribute to the emission. This indicates that neutron-star mergers produce gravitational waves and radioactively powered kilonovae, and are a nucleosynthetic source of the r-process elements.
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| 5. |
- Ademuyiwa, Adesoji O., et al.
(författare)
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Determinants of morbidity and mortality following emergency abdominal surgery in children in low-income and middle-income countries
- 2016
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Ingår i: BMJ Global Health. - : BMJ Publishing Group Ltd. - 2059-7908. ; 1:4
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Tidskriftsartikel (refereegranskat)abstract
- Background: Child health is a key priority on the global health agenda, yet the provision of essential and emergency surgery in children is patchy in resource-poor regions. This study was aimed to determine the mortality risk for emergency abdominal paediatric surgery in low-income countries globally.Methods: Multicentre, international, prospective, cohort study. Self-selected surgical units performing emergency abdominal surgery submitted prespecified data for consecutive children aged <16 years during a 2-week period between July and December 2014. The United Nation's Human Development Index (HDI) was used to stratify countries. The main outcome measure was 30-day postoperative mortality, analysed by multilevel logistic regression.Results: This study included 1409 patients from 253 centres in 43 countries; 282 children were under 2 years of age. Among them, 265 (18.8%) were from low-HDI, 450 (31.9%) from middle-HDI and 694 (49.3%) from high-HDI countries. The most common operations performed were appendectomy, small bowel resection, pyloromyotomy and correction of intussusception. After adjustment for patient and hospital risk factors, child mortality at 30 days was significantly higher in low-HDI (adjusted OR 7.14 (95% CI 2.52 to 20.23), p<0.001) and middle-HDI (4.42 (1.44 to 13.56), p=0.009) countries compared with high-HDI countries, translating to 40 excess deaths per 1000 procedures performed.Conclusions: Adjusted mortality in children following emergency abdominal surgery may be as high as 7 times greater in low-HDI and middle-HDI countries compared with high-HDI countries. Effective provision of emergency essential surgery should be a key priority for global child health agendas.
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| 6. |
- Leloudas, G., et al.
(författare)
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The superluminous transient ASASSN-15lh as a tidal disruption event from a Kerr black hole
- 2016
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Ingår i: Nature Astronomy. - : Springer Science and Business Media LLC. - 2397-3366. ; 1:1
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Tidskriftsartikel (refereegranskat)abstract
- When a star passes within the tidal radius of a supermassive black hole, it will be torn apart1. For a star with the mass of the Sun (M-circle dot) and a non-spinning black hole with a mass <10(8)M(circle dot), the tidal radius lies outside the black hole event horizon2 and the disruption results in a luminous flare(3-6). Here we report observations over a period of ten months of a transient, hitherto interpreted(7) as a superluminous supernova(8). Our data show that the transient rebrightened substantially in the ultraviolet and that the spectrum went through three different spectroscopic phases without ever becoming nebular. Our observations are more consistent with a tidal disruption event than a superluminous supernova because of the temperature evolution(6), the presence of highly ionized CNO gas in the line of sight(9) and our improved localization of the transient in the nucleus of a passive galaxy, where the presence of massive stars is highly unlikely(10,11). While the supermassive black hole has a mass >10(8)M(circle dot)(12,13), a star with the same mass as the Sun could be disrupted outside the event horizon if the black hole were spinning rapidly(14). The rapid spin and high black hole mass can explain the high luminosity of this event.
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| 7. |
- McKnight, J. A., et al.
(författare)
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Glycaemic control of Type1 diabetes in clinical practice early in the 21st century: an international comparison
- 2015
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Ingår i: Diabetic Medicine. - : Wiley. - 0742-3071. ; 32:8, s. 1036-1050
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Tidskriftsartikel (refereegranskat)abstract
- AimsImproving glycaemic control in people with Type1 diabetes is known to reduce complications. Our aim was to compare glycaemic control among people with Type1 diabetes using data gathered in regional or national registries. MethodsData were obtained for children and/or adults with Type1 diabetes from the following countries (or regions): Western Australia, Austria, Denmark, England, Champagne-Ardenne (France), Germany, Epirus, Thessaly and Thessaloniki (Greece), Galway (Ireland), several Italian regions, Latvia, Rotterdam (The Netherlands), Otago (New Zealand), Norway, Northern Ireland, Scotland, Sweden, Volyn (Ukraine), USA and Wales) from population or clinic-based registries. The sample size with available data varied from 355 to 173880. Proportions with HbA(1c) <58mmol/mol (<7.5%) and 75mmol/mol (9.0%) were compared by age and sex. ResultsData were available for 324501 people. The proportions with HbA(1c) 58mmol/mol (<7.5%) varied from 15.7% to 46.4% among 44058 people aged <15years, from 8.9% to 49.5% among 50766 people aged 15-24years and from 20.5% to 53.6% among 229677 people aged 25years. Sex differences in glycaemic control were small. Proportions of people using insulin pumps varied between the 12 sources with data available. ConclusionThese results suggest that there are substantial variations in glycaemic control among people with Type1 diabetes between the data sources and that there is room for improvement in all populations, especially in young adults. We present HbA(1c) data from registries in 19 different countries describing control in 324501 people with Type1 diabetes, across all age groups. These data are the best representation of diabetes care available and therefore describe the state of the art'. We show clearly that Type1 diabetes control is not as good as suggested in guidelines, but that some healthcare systems appear to result in better control than others. These data present a challenge to diabetes services. Leaders in diabetes units/service can compare their local data to our data and encourage improvement.
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| 8. |
- Kankare, E., et al.
(författare)
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On the triple peaks of SNHunt248 in NGC 5806
- 2015
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 581
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Tidskriftsartikel (refereegranskat)abstract
- We present our findings on a supernova (SN) impostor, SNHunt248, based on optical and near-IR data spanning similar to 15 yr before discovery, to similar to 1 yr post-discovery. The light curve displays three distinct peaks, the brightest of which is at MR similar to -15.0 mag. The post-discovery evolution is consistent with the ejecta from the outburst interacting with two distinct regions of circumstellar material. The 0.5-2.2 mu m spectral energy distribution at -740 d is well-matched by a single 6700 K blackbody with log(L/L-circle dot) similar to 6.1. This temperature and luminosity support previous suggestions of a yellow hypergiant progenitor; however, we find it to be brighter than the brightest and most massive Galactic late-F to early-G spectral type hypergiants. Overall the historical light curve displays variability of up to similar to +/- 1 mag. At current epochs (similar to 1 yr post-outburst), the absolute magnitude (MR similar to -9 mag) is just below the faintest observed historical absolute magnitude similar to 10 yr before discovery.
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| 9. |
- Magee, M. R., et al.
(författare)
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The type Iax supernova, SN 2015H A white dwarf deflagration candidate
- 2016
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 589
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Tidskriftsartikel (refereegranskat)abstract
- We present results based on observations of SN 2015H which belongs to the small group of objects similar to SN 2002cx, otherwise known as type Iax supernovae. The availability of deep pre-explosion imaging allowed us to place tight constraints on the explosion epoch. Our observational campaign began approximately one day post-explosion, and extended over a period of about 150 days post maximum light, making it one of the best observed objects of this class to date. We find a peak magnitude of M-r = 17.27 +/- 0.07, and a (Delta m(15))(r) = 0.69 +/- 0.04. Comparing our observations to synthetic spectra generated from simulations of deflagrations of Chandrasekhar mass carbon-oxygen white dwarfs, we find reasonable agreement with models of weak deflagrations that result in the ejection of similar to 0.2 M-circle dot of material containing similar to 0.07 M-circle dot of Ni-56. The model light curve however, evolves more rapidly than observations, suggesting that a higher ejecta mass is to be favoured. Nevertheless, empirical modelling of the pseudo-bolometric light curve suggests that less than or similar to 0.6 M-circle dot of material was ejected, implying that the white dwarf is not completely disrupted, and that a bound remnant is a likely outcome.
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| 10. |
- Richard, M. S., et al.
(författare)
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An empirical approach to modeling ion production rates in Titan's ionosphere I : Ion production rates on the dayside and globally
- 2015
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Ingår i: Journal of Geophysical Research - Space Physics. - 2169-9380 .- 2169-9402. ; 120:2, s. 1264-1280
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Tidskriftsartikel (refereegranskat)abstract
- Titan's ionosphere is created when solar photons, energetic magnetospheric electrons or ions, and cosmic rays ionize the neutral atmosphere. Electron densities generated by current theoretical models are much larger than densities measured by instruments on board the Cassini orbiter. This model density overabundance must result either from overproduction or from insufficient loss of ions. This is the first of two papers that examines ion production rates in Titan's ionosphere, for the dayside and nightside ionosphere, respectively. The first (current) paper focuses on dayside ion production rates which are computed using solar ionization sources (photoionization and electron impact ionization by photoelectrons) between 1000 and 1400km. In addition to theoretical ion production rates, empirical ion production rates are derived from CH4, CH3+, and CH4+ densities measured by the INMS (Ion Neutral Mass Spectrometer) for many Titan passes. The modeled and empirical production rate profiles from measured densities of N-2(+) and CH4+ are found to be in good agreement (to within 20%) for solar zenith angles between 15 and 90 degrees. This suggests that the overabundance of electrons in theoretical models of Titan's dayside ionosphere is not due to overproduction but to insufficient ion losses.
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