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- Cunha, M. S., et al.
(författare)
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Rotation and pulsation in Ap stars : first light results from TESS sectors 1 and 2
- 2019
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Ingår i: Monthly notices of the Royal Astronomical Society. - : OXFORD UNIV PRESS. - 0035-8711 .- 1365-2966. ; 487:3, s. 3523-3549
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Tidskriftsartikel (refereegranskat)abstract
- We present the first results from the Transiting Exoplanet Survey Satellite (TESS) on the rotational and pulsational variability of magnetic chemically peculiar A-type stars. We analyse TESS 2-min cadence data from sectors 1 and 2 on a sample of 83 stars. Five new rapidly oscillating Ap (roAp) stars are announced. One of these pulsates with periods around 4.7 min, making it the shortest period roAp star known to date. Four out of the five new roAp stars are multiperiodic. Three of these and the singly periodic one show the presence of rotational mode splitting. Individual frequencies are provided in all cases. In addition, seven previously known roAp stars are analysed. Additional modes of oscillation are found in some stars, while in others we are able to distinguish the true pulsations from possible aliases present in the ground-based data. We find that the pulsation amplitude in the TESS filter is typically a factor of 6 smaller than that in the B filter, which is usually used for ground-based observations. For four roAp stars we set constraints on the inclination angle and magnetic obliquity, through the application of the oblique pulsator model. We also confirm the absence of roAp-type pulsations down to amplitude limits of 6 and 13 mu mag, respectively, in two of the best characterized non-oscillating Ap (noAp) stars. We announce 27 new rotational variables along with their rotation periods, and provide different rotation periods for seven other stars. Finally, we discuss how these results challenge state-of-the-art pulsation models for roAp stars.
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- Holdsworth, D. L., et al.
(författare)
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TESS cycle 1 observations of roAp stars with 2-min cadence data
- 2021
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966. ; 506:1, s. 1073-1110
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Tidskriftsartikel (refereegranskat)abstract
- We present the results of a systematic search for new rapidly oscillating Ap (roAp) stars using the 2-min cadence data collected by the Transiting Exoplanet Survey Satellite (TESS) during its Cycle 1 observations. We identify 12 new roAp stars. Amongst these stars we discover the roAp star with the longest pulsation period, another with the shortest rotation period, and six with multiperiodic variability. In addition to these new roAp stars, we present an analysis of 44 known roAp stars observed by TESS during Cycle 1, providing the first high-precision and homogeneous sample of a significant fraction of the known roAp stars. The TESS observations have shown that almost 60 percent (33) of our sample of stars are multiperiodic, providing excellent cases to test models of roAp pulsations, and from which the most rewarding asteroseismic results can be gleaned. We report four cases of the occurrence of rotationally split frequency multiplets that imply different mode geometries for the same degree modes in the same star. This provides a conundrum in applying the oblique pulsator model to the roAp stars. Finally, we report the discovery of non-linear mode interactions in alpha Cir (TIC402546736, HD128898) around the harmonic of the principal mode - this is only the second case of such a phenomenon.
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- Rose, K, et al.
(författare)
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Responses of paediatric emergency departments to the first wave of the COVID-19 pandemic in Europe: a cross-sectional survey study
- 2021
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Ingår i: BMJ paediatrics open. - : BMJ. - 2399-9772. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- Understanding how paediatric emergency departments (PEDs) across Europe adapted their healthcare pathways in response to COVID-19 will help guide responses to ongoing waves of COVID-19 and potential future pandemics. This study aimed to evaluate service reconfiguration across European PEDs during the initial COVID-19 wave.DesignThis cross-sectional survey included 39 PEDs in 17 countries. The online questionnaire captured (1) study site characteristics, (2) departmental changes and (3) pathways for children with acute illness pre and during the first wave of COVID-19 pandemic (January–May 2020). Number of changes to health services, as a percentage of total possible changes encompassed by the survey, was compared with peak national SARS-CoV-2 incidence rates, and for both mixed and standalone paediatric centres.ResultsOverall, 97% (n=38) of centres remained open as usual during the pandemic. The capacity of 18 out of 28 (68%) short-stay units decreased; in contrast, 2 units (7%) increased their capacity. In 12 (31%) PEDs, they reported acting as receiving centres for diverted children during the pandemic.There was minimal change to the availability of paediatric consultant telephone advice services, consultant supervision of juniors or presence of responsible specialists within the PEDs.There was no relationship between percentage of possible change at each site and the peak national SARS-CoV-2 incidence rate. Mixed paediatric and adult hospitals made 8% of possible changes and standalone paediatric centres made 6% of possible changes (p=0.086).ConclusionOverall, there was limited change to the organisation or delivery of services across surveyed PEDs during the first wave of the COVID-19 pandemic.
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