Automated extraction of oscillation parameters for Kepler observations of solar-type stars

The recent launch of the Kepler space telescope brings the opportunity to study oscillations systematically in large numbers of solar-like stars. In the framework of the asteroFLAG project, we have developed an automated pipeline to estimate global oscillation parameters, such as the frequency of maximum power (nu_max) and the large frequency spacing (Delta_nu), for a large number of time series. We present an effective method based on the autocorrelation function to find excess power and use a scaling relation to estimate granulation timescales as initial conditions for background modelling. We derive reliable uncertainties for nu_max and Delta_nu through extensive simulations. We have tested the pipeline on about 2000 simulated Kepler stars with magnitudes of V~7-12 and were able to correctly determine nu_max and Delta_nu for about half of the sample. For about 20%, the returned large frequency spacing is accurate enough to determine stellar radii to a 1% precision. We conclude that the methods presented here are a promising approach to process the large amount of data expected from Kepler.Comment: 14 pages, 9 figures, accepted for publication in Communications in Asteroseismolog

Évaluation des compétences en réanimation en séance de simulation et en milieu de travail : analyse descriptive et comparative de trois spécialités

Background: Simulation-based assessment can complement workplace-based assessment of rare or difficult to assess Entrustable Professional Activities (EPAs). We aimed to compare the use of simulation-based assessment for resuscitation-focused EPAs in three postgraduate medical training programs and describe faculty perceptions of simulation-based assessment. Methods: EPA assessment scores and setting (simulation or workplace) were extracted from 2017-2020 for internal medicine, emergency medicine, and surgical foundations residents at the transition to discipline and foundations of discipline stages. A questionnaire was distributed to clinical competency committee members. Results: Eleven percent of EPA assessments were simulation-based. The proportion of simulation-based assessment did not differ between programs but differed between transition (38%) and foundations (4%) stages within surgical foundations only. Entrustment scores differed between settings in emergency medicine at the transition level only (simulation: 4.82 ± 0.60 workplace: 3.74 ± 0.93). 70% of committee members (n=20) completed the questionnaire. Of those that use simulation-based assessment, 45% interpret them differently than workplace-based assessments. 73% and 100% trust simulation for high-stakes and low-stakes assessment, respectively. Conclusions: The proportion of simulation-based assessment for resuscitation focused EPAs did not differ between three postgraduate medical training programs. Interpretation of simulation-based assessment data between committee members was inconsistent. All respondents trust simulation-based assessment for low-stakes, and the majority for high-stakes assessment. These findings have practical implications for the integration simulation into programs of assessment.Contexte : Pour les activités professionnelles confiables (APC) qui sont rarement observées ou difficiles à évaluer, l’évaluation dans les séances de simulation peut compléter l’évaluation en milieu de travail. Nous avons comparé l’utilisation de l’évaluation lors de simulations pour les APC axées sur la réanimation dans trois programmes de formation médicale postdoctorale et décrit les perceptions de membres du corps professoral concernant cette modalité d’évaluation. Méthodes : Nous avons extrait les scores et le cadre (simulation ou lieu de travail) d’évaluation des APC de 2017 à 2020 pour les résidents en médecine interne, en médecine d’urgence et en fondements chirurgicaux aux étapes de transition vers la discipline et de fondements de la discipline. Un questionnaire a été distribué aux membres du comité des compétences cliniques. Résultats : Onze pour cent des évaluations d’APC étaient faites lors de séances de simulation. Cette proportion était la même pour tous les programmes, mais dans le cadre des fondements chirurgicaux, elle était différente selon qu’il s’agissait de l’étape de transition (38 %) ou de l’étape des fondements (4 %). Les scores de confiance différaient selon le cadre de l’évaluation uniquement pour les résidents en médecine d’urgence à l’étape de la transition (simulation : 4,82 ± 0,60; lieu de travail : 3,74 ± 0,93). Le questionnaire a été rempli par 70 % des membres du comité (n=20). Parmi ceux qui avaient utilisé l’évaluation en séance de simulation, 45 % avaient interprété les données de l’évaluation différemment de la façon dont ils interprètent les données d’évaluation en milieu de travail. Soixante-treize pour cent et 100 % d’entre eux font confiance à la simulation pour les évaluations à enjeux élevés et à faibles enjeux, respectivement. Conclusions : La proportion d’évaluations en séance de simulation pour les APC axées sur la réanimation était la même pour trois programmes de formation médicale postdoctorale. Les membres du comité n’ont pas interprété les données de ce type d’évaluation de manière uniforme. Tous les répondants font confiance à l’évaluation en séance de simulation pour les évaluations à faible enjeu, et la plupart d’entre eux pour les évaluations à enjeu élevé. Ces résultats ont des incidences pratiques sur l’intégration de la simulation dans les programmes d’évaluation

Rétroaction multisources à la suite d’une simulation en réanimation : une étude qualitative

Background: The direct observation and assessment of learners’ resuscitation skills by an attending physician is challenging due to the unpredictable and time-sensitive nature of these events. Multisource feedback (MSF) may address this challenge and improve the quality of assessments provided to learners. We aimed to describe the similarities and differences in the assessment rationale of attending physicians, registered nurses, and resident peers in the context of a simulation-based resuscitation curriculum. Methods: We conducted a qualitative content analysis of narrative MSF of medical residents in their first postgraduate year of training who were participating in a simulation-based resuscitation course at two Canadian institutions. Assessments included an entrustment score and narrative comments from attending physicians, registered nurses, and resident peers in addition to self-assessment. Narrative comments were transcribed and analyzed thematically using a constant comparative method. Results: All 87 residents (100%) participating in the 2017-2018 course provided consent. A total of 223 assessments were included in our analysis. Four themes emerged from the narrative data: 1) Communication, 2) Leadership, 3) Demeanor, and 4) Medical Expert. Relative to other assessor groups, feedback from nurses focused on patient-centred care and communication while attending physicians focused on the medical expert theme. Peer feedback was the most positive. Self-assessments included comments within each of the four themes. Conclusions: In the context of a simulation-based resuscitation curriculum, MSF provided learners with different perspectives in their narrative assessment rationale and may offer a more holistic assessment of resuscitation skills within a competency-based medical education (CBME) program of assessment.Contexte : Le contexte imprévisible et contraignant au niveau du temps lors de l’observation directe et de la rétroaction associée sur les compétences en réanimation des apprenants constituent un défi pour un médecin superviseur. La rétroaction multisources (RMS) peut être un moyen de relever ce défi et d'améliorer la qualité des rétroactions fournies aux apprenants. Nous visons à décrire les similitudes et les différences quant à la démarche évaluative auprès de médecins traitants, d’infirmières cliniciennes et de pairs résidents dans le cadre d'un cours de réanimation offert par simulation. Méthodes : Nous avons réalisé une analyse de contenu à partir des rétroactions narratives offertes aux résidents en première année de formation postdoctorale dans deux universités canadiennes dans le cadre d’un cours de réanimation offert par simulation. En plus de l’auto-évaluation, la rétroaction comportait un score de confiance et des commentaires narratifs de la part de médecins superviseurs, d’infirmières cliniciennes et des pairs. Les commentaires ont été transcrits et analysés par thèmes en appliquant la méthode générale de comparaison constante. Résultats : Un consentement pour participer à l’étude a été obtenu auprès des 87 résidents (100 %) qui ont suivi le cours en 2017-2018. Nous avons analysé un total de 223 rétroactions. Quatre thèmes ont émergé à partir des données narratives soit : 1) la communication, 2) le leadership, 3) le comportement, et 4) l’expertise médicale. Alors que les infirmières ont ciblé leurs commentaires sur les soins centrés sur le patient et la communication, les médecins superviseurs ont les ont ciblés sur l’expertise médicale. Les commentaires des pairs étaient les plus positifs. Les auto-évaluations comportaient des commentaires sur chacun des quatre thèmes. Conclusions : Dans le contexte d’un cours de réanimation offert par simulation, la RMS a permis aux apprenants d’obtenir des évaluations narratives selon différentes perspectives. Permettant ainsi une approche plus holistique de rétroaction sur les habiletés en réanimation dans le cadre d’un programme d’évaluation axé sur les compétences

The amplitude of solar oscillations using stellar techniques

The amplitudes of solar-like oscillations depend on the excitation and damping, both of which are controlled by convection. Comparing observations with theory should therefore improve our understanding of the underlying physics. However, theoretical models invariably compute oscillation amplitudes relative to the Sun, and it is therefore vital to have a good calibration of the solar amplitude using stellar techniques. We have used daytime spectra of the Sun, obtained with HARPS and UCLES, to measure the solar oscillations and made a detailed comparison with observations using the BiSON helioseismology instrument. We find that the mean solar amplitude measured using stellar techniques, averaged over one full solar cycle, is 18.7 +/- 0.7 cm/s for the strongest radial modes (l=0) and 25.2 +/- 0.9 cm/s for l=1. In addition, we use simulations to establish an equation that estimates the uncertainty of amplitude measurements that are made of other stars, given that the mode lifetime is known. Finally, we also give amplitudes of solar-like oscillations for three stars that we measured from a series of short observations with HARPS (gamma Ser, beta Aql and alpha For), together with revised amplitudes for five other stars for which we have previously published results (alpha Cen A, alpha Cen B, beta Hyi, nu Ind and delta Pav).Comment: 8 pages, accepted by ApJ. Minor wording changes and added a referenc

Déstabilisés et agités : état émotionnel, charge cognitive et performance des résidents juniors lors d’une réanimation simulée

Background: Patient resuscitation can be overwhelming for junior postgraduate medical residents due to its inherent complexity and high-stakes environment. Emotional states of unpleasant hyperarousal burden cognitive resources, contributing to cognitive overload and performance decline. Our objective is to characterize the associations between pre-scenario emotional state and junior residents’ cognitive load and performance in a simulated-resuscitation, to provide evidence for informed curricular development. Methods: PGY-1 residents self-rated their emotional state before four simulated-resuscitation scenarios, and their cognitive load after. Faculty assessed performance with entrustment scores. Factor analysis identified the principal components of emotional state data. Linear regression models examined the relationship between pre-scenario emotional components, cognitive load, and performance scores.  Results: 47/47 medical and surgical residents (100%) participated and completed Emotional State (99.5%) and Cognitive Load (98.9%) surveys. Positive invigoration and negative tranquility were the principal components. Pre-scenario tranquility was negatively associated with cognitive load (b= -0.23, p < 0.0001), and cognitive load was negatively associated with performance scores (b= -0.27, p < 0.0001). Pre-scenario invigoration was negatively associated with cognitive load (b=-0.18,p = 0.0001), and positively associated with performance scores (b= 0.08, p = 0.0193).  Conclusion: Amongst junior residents participating in simulated resuscitation scenarios, pre-scenario agitation (negative tranquility) is associated with increased cognitive load, which itself is associated with lower performance scores. These findings suggest residency programs should consider developing curriculum aimed at modulating residents’ emotional agitation and reducing residents’ cognitive burden to improve resuscitation performance.Contexte : La réanimation de patients peut être éprouvante pour les stagiaires postdoctoraux juniors en raison de la complexité qui y est inhérente et de la gravité de l’enjeu. Les états émotionnels désagréables d’hyperexcitation épuisent les ressources cognitives, contribuant ainsi à la surcharge cognitive et à la baisse de la performance. Notre objectif était de mettre en évidence le rapport entre l’état émotionnel des résidents juniors avant une simulation de réanimation d’un côté et leur charge cognitive et leur performance lors de celle-ci de l’autre, pour produire des données probantes pouvant servir à la conception éclairée de programmes d’enseignement. Méthodes : Des résidents de première année ont autoévalué leur état émotionnel avant chacun des quatre scénarios de réanimation simulée, ainsi que leur charge cognitive après les simulations. Des membres du corps professoral ont évalué leur performance par l’attribution de scores de confiance. Les principales composantes des données sur l’état émotionnel ont été déterminées par le biais d’une analyse factorielle. On s’est servi de modèles de régression linéaire pour établir la relation entre les composantes émotionnelles avant la simulation, la charge cognitive et les scores de performance. Résultats : Les 47 résidents en médecine et en chirurgie qui ont participé à l’étude (100 %) ont rempli les questionnaires sur l’état émotionnel (99,5 %) et la charge cognitive (98,9 %). La stimulation positive et la tranquillité négative sont les principales composantes dégagées. La tranquillité avant la simulation était négativement corrélée avec la charge cognitive (b= -0,23, p<0,0001), et la charge cognitive était négativement liée aux scores de performance (b= -0,27, p<0,0001). La stimulation avant la simulation était négativement corrélée avec la charge cognitive (b=-0.18, p=0.0001), et positivement corrélée avec les scores de performance (b= 0.08, p=0.0193). Conclusion : Chez les résidents juniors qui ont participé à des scénarios de réanimation simulée, l’agitation précédant cette dernière (tranquillité négative) était liée à une charge cognitive accrue, qui elle-même a donné lieu à des scores de performance plus faibles. Ces résultats montrent la pertinence de concevoir des programmes qui visent à réduire l’agitation émotionnelle et la charge cognitive des résidents afin d’améliorer leurs performances en réanimation

Testing asteroseismology with Gaia DR2: Hierarchical models of the Red Clump

Asteroseismology provides fundamental stellar parameters independent of distance, but subject to systematics under calibration. Gaia DR2 has provided parallaxes for a billion stars, which are offset by a parallax zero-point. Red Clump (RC) stars have a narrow spread in luminosity, thus functioning as standard candles to calibrate these systematics. This work measures how the magnitude and spread of the RC in the Kepler field are affected by changes to temperature and scaling relations for seismology, and changes to the parallax zero-point for Gaia. We use a sample of 5576 RC stars classified through asteroseismology. We apply hierarchical Bayesian latent variable models, finding the population level properties of the RC with seismology, and use those as priors on Gaia parallaxes to find the parallax zero-point offset. We then find the position of the RC using published values for the zero-point. We find a seismic temperature insensitive spread of the RC of ~0.03 mag in the 2MASS K band and a larger and slightly temperature-dependent spread of ~0.13 mag in the Gaia G band. This intrinsic dispersion in the K band provides a distance precision of ~1% for RC stars. Using Gaia data alone, we find a mean zero-point of -41 $\pm$ 10 $\mu$as. This offset yields RC absolute magnitudes of -1.634 $\pm$ 0.018 in K and 0.546 $\pm$ 0.016 in G. Obtaining these same values through seismology would require a global temperature shift of ~-70 K, which is compatible with known systematics in spectroscopy.Comment: Accepted for publication in MNRA

Kepler Input Catalog: Photometric Calibration and Stellar Classification

We describe the photometric calibration and stellar classification methods used to produce the Kepler Input Catalog (KIC). The KIC is a catalog containing photometric and physical data for sources in the Kepler Mission field of view; it is used by the mission to select optimal targets. We derived atmospheric extinction corrections from hourly observations of secondary standard fields within the Kepler field of view. Repeatability of absolute photometry for stars brighter than magnitude 15 is typically 2%. We estimated stellar parameters Teff, log(g), log (Z), E_{B-V} using Bayesian posterior probability maximization to match observed colors to Castelli stellar atmosphere models. We applied Bayesian priors describing the distribution of solar-neighborhood stars in the color-magnitude diagram (CMD), in log (Z)$, and in height above the galactic plane. Comparisons with samples of stars classified by other means indicate that in most regions of the CMD, our classifications are reliable within about +/- 200 K and +/- 0.4 dex in log (g). It is difficult to assess the reliability of our log(Z) estimates, but there is reason to suspect that it is poor, particularly at extreme Teff. Of great importance for the Kepler Mission, for Teff <= 5400 K, the distinction between main-sequence stars and giants has proved to be reliable with better than 98% confidence. The KIC is available through the MAST data archive.Comment: 77 pages, 12 figures, 1 Table. Accepted by Astronomical Journal 24 July 201

Oscillation frequencies and mode lifetimes in alpha Centauri A

We analyse our recently-published velocity measurements of alpha Cen A (Butler et al. 2004). After adjusting the weights on a night-by-night basis in order to optimize the window function to minimize sidelobes, we extract 42 oscillation frequencies with l=0 to 3 and measure the large and small frequency separations. We give fitted relations to these frequencies that can be compared with theoretical models and conclude that the observed scatter about these fits is due to the finite lifetimes of the oscillation modes. We estimate the mode lifetimes to be 1-2 d, substantially shorter than in the Sun.Comment: Accepted by Ap

Asteroseismic properties of solar-type stars observed with the NASA K2 mission: results from Campaigns 1-3 and prospects for future observations

We present an asteroseismic analysis of 33 solar-type stars observed in short cadence during Campaigns (C) 1-3 of the NASA K2 mission. We were able to extract both average seismic parameters and individual mode frequencies for stars with dominant frequencies up to ~3300{\mu}Hz, and we find that data for some targets are good enough to allow for a measurement of the rotational splitting. Modelling of the extracted parameters is performed by using grid-based methods using average parameters and individual frequencies together with spectroscopic parameters. For the target selection in C3, stars were chosen as in C1 and C2 to cover a wide range in parameter space to better understand the performance and noise characteristics. For C3 we still detected oscillations in 73% of the observed stars that we proposed. Future K2 campaigns hold great promise for the study of nearby clusters and the chemical evolution and age-metallicity relation of nearby field stars in the solar neighbourhood. We expect oscillations to be detected in ~388 short-cadence targets if the K2 mission continues until C18, which will greatly complement the ~500 detections of solar-like oscillations made for short-cadence targets during the nominal Kepler mission. For ~30-40 of these, including several members of the Hyades open cluster, we furthermore expect that inference from interferometry should be possible.Comment: 17 pages, 15 figures, 4 tables; accepted for publication in PAS

Asteroseismology of the Transiting Exoplanet Host HD 17156 with HST FGS

Observations conducted with the Fine Guidance Sensor on Hubble Space Telescope (HST) providing high cadence and precision time-series photometry were obtained over 10 consecutive days in December 2008 on the host star of the transiting exoplanet HD 17156b. During this time 10^12 photons (corrected for detector deadtime) were collected in which a noise level of 163 parts per million per 30 second sum resulted, thus providing excellent sensitivity to detection of the analog of the solar 5-minute p-mode oscillations. For HD 17156 robust detection of p-modes supports determination of the stellar mean density of 0.5301 +/- 0.0044 g/cm^3 from a detailed fit to the observed frequencies of modes of degree l = 0, 1, and 2. This is the first star for which direct determination of the mean stellar density has been possible using both asteroseismology and detailed analysis of a transiting planet light curve. Using the density constraint from asteroseismology, and stellar evolution modeling results in M_star = 1.285 +/- 0.026 solar, R_star = 1.507 +/- 0.012 solar, and a stellar age of 3.2 +/- 0.3 Gyr.Comment: Accepted by ApJ; 16 pages, 18 figure