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- Miglio, A., et al.
(author)
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PLATO as it is : A legacy mission for Galactic archaeology
- 2017
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In: Astronomical Notes - Astronomische Nachrichten. - : WILEY-V C H VERLAG GMBH. - 0004-6337 .- 1521-3994. ; 338:6, s. 644-661
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Journal article (peer-reviewed)abstract
- Deciphering the assembly history of the Milky Way is a formidable task, which becomes possible only if one can produce high-resolution chrono-chemo-kinematical maps of the Galaxy. Data from large-scale astrometric and spectroscopic surveys will soon provide us with a well-defined view of the current chemo-kinematical structure of the Milky Way, but it will only enable a blurred view on the temporal sequence that led to the present-day Galaxy. As demonstrated by the (ongoing) exploitation of data from the pioneering photometric missions CoRoT, Kepler, and K2, asteroseismology provides the way forward: solar-like oscillating giants are excellent evolutionary clocks thanks to the availability of seismic constraints on their mass and to the tight age-initial mass relation they adhere to. In this paper we identify five key outstanding questions relating to the formation and evolution of the Milky Way that will need precise and accurate ages for large samples of stars to be addressed, and we identify the requirements in terms of number of targets and the precision on the stellar properties that are needed to tackle such questions. By quantifying the asteroseismic yields expected from PLATO for red giant stars, we demonstrate that these requirements are within the capabilities of the current instrument design, provided that observations are sufficiently long to identify the evolutionary state and allow robust and precise determination of acoustic-mode frequencies. This will allow us to harvest data of sufficient quality to reach a 10% precision in age. This is a fundamental prerequisite to then reach the more ambitious goal of a similar level of accuracy, which will be possible only if we have at hand a careful appraisal of systematic uncertainties on age deriving from our limited understanding of stellar physics, a goal that conveniently falls within the main aims of PLATO's core science. We therefore strongly endorse PLATO's current design and proposed observational strategy, and conclude that PLATO, as it is, will be a legacy mission for Galactic archaeology.
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- Holdsworth, D. L., et al.
(author)
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TESS Cycle 2 observations of roAp stars with 2-min cadence data
- 2024
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966. ; 527:4, s. 9548-9580
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Journal article (peer-reviewed)abstract
- We present the results of a systematic search of the Transiting Exoplanet Survey Satellite (TESS) 2-min cadence data for new rapidly oscillating Ap (roAp) stars observed during the Cycle 2 phase of its mission. We find seven new roAp stars previously unreported as such and present the analysis of a further 25 roAp stars that are already known. Three of the new stars show multiperiodic pulsations, while all new members are rotationally variable stars, leading to almost 70 per cent (22) of the roAp stars presented being α2 CVn-type variable stars. We show that targeted observations of known chemically peculiar stars are likely to overlook many new roAp stars, and demonstrate that multiepoch observations are necessary to see pulsational behaviour changes. We find a lack of roAp stars close to the blue edge of the theoretical roAp instability strip, and reaffirm that mode instability is observed more frequently with precise, space-based observations. In addition to the Cycle 2 observations, we analyse TESS data for all-known roAp stars. This amounts to 18 further roAp stars observed by TESS. Finally, we list six known roAp stars that TESS is yet to observe. We deduce that the incidence of roAp stars amongst the Ap star population is just 5.5 per cent, raising fundamental questions about the conditions required to excite pulsations in Ap stars. This work, coupled with our previous work on roAp stars in Cycle 1 observations, presents the most comprehensive, homogeneous study of the roAp stars in the TESS nominal mission, with a collection of 112 confirmed roAp stars in total.
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- Holdsworth, D. L., et al.
(author)
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TESS cycle 1 observations of roAp stars with 2-min cadence data
- 2021
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966. ; 506:1, s. 1073-1110
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Journal article (peer-reviewed)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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- Mattsson, Niklas, 1979, et al.
(author)
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The Alzheimer's Association external quality control program for cerebrospinal fluid biomarkers.
- 2011
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In: Alzheimer's & dementia : the journal of the Alzheimer's Association. - : Wiley. - 1552-5279. ; 7:4
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Journal article (peer-reviewed)abstract
- The cerebrospinal fluid (CSF) biomarkers amyloid β (Aβ)-42, total-tau (T-tau), and phosphorylated-tau (P-tau) demonstrate good diagnostic accuracy for Alzheimer's disease (AD). However, there are large variations in biomarker measurements between studies, and between and within laboratories. The Alzheimer's Association has initiated a global quality control program to estimate and monitor variability of measurements, quantify batch-to-batch assay variations, and identify sources of variability. In this article, we present the results from the first two rounds of the program.
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- Handberg, A, et al.
(author)
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Soluble CD36 (sCD36) clusters with markers of insulin resistance, and high sCD36 is associated with increased type 2 diabetes risk
- 2010
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In: Journal of Clinical Endocrinology and Metabolism. - : The Endocrine Society. - 0021-972X .- 1945-7197. ; 95:4, s. 1939-1946
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Journal article (peer-reviewed)abstract
- CONTEXT AND OBJECTIVE:Soluble CD36 (sCD36) may be an early marker of insulin resistance and atherosclerosis. The objective of this prospective study was to evaluate sCD36 as a predictor of type 2 diabetes and to study its relationship with components of the metabolic syndrome (MetSy).DESIGN, SETTING, PARTICIPANTS, AND OUTCOME MEASURES:We conducted a case-referent study nested within a population-based health survey. Baseline variables included sCD36, body mass index, blood pressure, blood lipids, adipokines, inflammatory markers, and beta-cell function. A total of 173 initially nondiabetic cohort members who developed type 2 diabetes during 10 yr of follow-up were matched (1:2) with referents. Exploratory factor analysis was applied to hypothesize affiliation of sCD36 to the MetSy components.RESULTS:Doubling of baseline sCD36 increases the odds ratio for diabetes development by 1.24 in the general study population and by 1.45 in the female population (P < 0.025). Comparing upper sCD36 quartiles with lower, odds ratio for diabetes was 4.6 in women (P = 0.001), 3.15 in men (P = 0.011), and 2.6 in obese individuals (P < 0.025). Multivariate analysis shows that sCD36 does not predict diabetes independent of fasting plasma glucose and insulin. Factor analysis of 15 variables generates a six-factor model explaining 66-69% of total variance, where sCD36, body mass index, insulin, proinsulin, and leptin were assigned to the obesity/insulin resistance cluster.CONCLUSIONS:Upper quartile sCD36 is associated with elevated diabetes risk independent of age, gender, and obesity. Baseline sCD36 does not, however, predict diabetes independent of fasting glucose and insulin. sCD36 clusters with important markers of insulin resistance and MetSy that are key predictors of type 2 diabetes.
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