Aims.
Both components of the bright eclipsing binary
α
Dra have been resolved using long baseline interferometry and the secondary component has been shown to contribute approximately 15% of the ...total flux; however, a spectroscopic detection of the companion star has so far been unsuccessful. We aim for a firm spectroscopic detection of the secondary component of
α
Dra using state-of-the-art spectroscopic analysis methods for very high-quality spectroscopic observations. This will allow the determination of fundamental and atmospheric properties of the components in the system with high precision and accuracy.
Methods.
To achieve our goals, we use a combined data set from interferometry with the Navy Precision Optical Interferometer (NPOI), photometry with the TESS space observatory, and high-resolution spectroscopy with the H
ERMES
fibre-fed spectrograph at the La Palma observatory. We use the method of spectral disentangling to search for the contribution of a companion star in the observed composite H
ERMES
spectra, to separate the spectral contributions of both components, and to determine orbital elements of the
α
Dra system. TESS light curves are analysed in an iterative fashion with spectroscopic inference of stellar atmospheric parameters to determine fundamental stellar properties and their uncertainties. Finally, NPOI interferometric measurements are used for determination of the orbital parameters of the system and angular diameters of both binary components.
Results.
We report the first firm spectroscopic detection of the secondary component in
α
Dra and deliver disentangled spectra of both binary components. The components’ masses and radii are inferred with high precision and accuracy, and are
M
A
= 3.186 ± 0.044
M
⊙
,
R
A
= 4.932 ± 0.036
R
⊙
, and
M
B
= 2.431 ± 0.019
M
⊙
,
R
B
= 2.326 ± 0.052
R
⊙
for the primary and secondary components, respectively. Combined astrometric and spectroscopic analysis yields the semi-major axis of the system, which is ultimately used to derive the dynamical parallax of
π
= 11.48 ± 0.13 mas, and the distance
d
= 87.07 ± 1.03 pc to the
α
Dra system. Evolutionary analysis of both binary components with M
ESA
stellar structure and evolution models suggests the primary is an evolved post-TAMS A-type star, while the companion is a main-sequence A-type star with a convective core mass of
M
cc
= 0.337 ± 0.011
M
⊙
. Positions of both binary components in the Kiel- and HR-diagrams suggest a value of the convective core overshooting parameter
f
ov
well below 0.010
H
p
, and we infer the age of the system to be 310 ± 25 Myr.
Conclusions.
The inferred near-core mixing properties of both components do not support a dependence of the convective core overshooting on the stellar mass. At the same time, the
α
Dra system provides extra support to hypothesise that the mass discrepancy in eclipsing spectroscopic double-lined binaries is associated with inferior atmospheric modelling of intermediate- and high-mass stars, and less so with the predictive powerof stellar structure and evolution models as to the amount of near-core mixing and mass of the convective core.
ABSTRACT
By combining ground-based spectrographic observations of variability in the chromospheric emission from Sun-like stars with the variability seen in their eigenmode frequencies, it is ...possible to relate the changes observed at the surfaces of these stars to the changes taking place in the interior. By further comparing this variability to changes in the relative flux from the stars, one can obtain an expression for how these activity indicators relate to the energy output from the stars. Such studies become very pertinent when the variability can be related to stellar cycles as they can then be used to improve our understanding of the solar cycle and its effect on the energy output from the Sun. Here, we present observations of chromospheric emission in 20 Sun-like stars obtained over the course of the nominal 4 yr Kepler mission. Even though 4 yr is too short to detect stellar equivalents of the 11 yr solar cycle, observations from the Kepler mission can still be used to analyse the variability of the different activity indicators thereby obtaining information of the physical mechanism generating the variability. The analysis reveals no strong correlation between the different activity indicators, except in very few cases. We suggest that this is due to the sparse sampling of our ground-based observations on the one hand and that we are likely not tracing cyclic variability on the other hand. We also discuss how to improve the situation.
Altough both components of the bright eclipsing binary \(\alpha\) Dra having been resolved using long baseline interferometry and the secondary component shown to contribute some 15\% of the total ...flux, a spectroscopic detection of the companion star was so far unsuccessful. To achieve our goals, we use a combined data set from interferometry with the Navy Precision Optical Interferometer (NPOI), photometry with the TESS space observatory, and high-resolution spectroscopy with the HERMES fibre-fed spectrograph at the La Palma observatory. We use the method of spectral disentangling to search for the contribution of a companion star in the observed composite HERMES spectra, to separate the spectral contributions of both components, and to determine orbital elements of the \(\alpha\) Dra system. TESS light curves are analysed in an iterative fashion with spectroscopic inference of stellar atmospheric parameters to determine fundamental stellar properties and their uncertainties. Finally, NPOI interferometric measurements are used for determination of the orbital parameters of the system and angular diameters of both binary components. We report the first firm spectroscopic detection of the secondary component in \(\alpha\) Dra and deliver disentangled spectra of both binary components. The inferred near-core mixing properties of both components do not support a dependence of the convective core overshooting on the stellar mass. At the same time, the \(\alpha\) Dra system provides extra support to hypothesise that the mass discrepancy in eclipsing spectroscopic double-lined binaries is associated with inferior atmospheric modelling of intermediate- and high-mass stars, and less so with the predictive power of stellar structure and evolution models as to the amount of near-core mixing and mass of the convective core. (abridged abstract)
Context. PLAnetary Transits and Oscillations of stars (PLATO) is the ESA M3 space mission dedicated to detect and characterise transiting exoplanets including information from the asteroseismic ...properties of their stellar hosts. The uninterrupted and high-precision photometry provided by space-borne instruments such as PLATO require long preparatory phases. An exhaustive list of tests are paramount to design a mission that meets the performance requirements and, as such, simulations are an indispensable tool in the mission preparation. Aims. To accommodate PLATO’s need of versatile simulations prior to mission launch that at the same time describe innovative yet complex multi-telescope design accurately, in this work we present the end-to-end PLATO simulator specifically developed for that purpose, namely PlatoSim . We show, step-by-step, the algorithms embedded into the software architecture of PlatoSim that allow the user to simulate photometric time series of charge-coupled device (CCD) images and light curves in accordance to the expected observations of PLATO. Methods. In the context of the PLATO payload, a general formalism of modelling, end-to-end, incoming photons from the sky to the final measurement in digital units is discussed. According to the light path through the instrument, we present an overview of the stellar field and sky background, the short- and long-term barycentric pixel displacement of the stellar sources, the cameras and their optics, the modelling of the CCDs and their electronics, and all main random and systematic noise sources. Results. We show the strong predictive power of PlatoSim through its diverse applicability and contribution to numerous working groups within the PLATO mission consortium. This involves the ongoing mechanical integration and alignment, performance studies of the payload, the pipeline development, and assessments of the scientific goals. Conclusions. PlatoSim is a state-of-the-art simulator that is able to produce the expected photometric observations of PLATO to a high level of accuracy. We demonstrate that PlatoSim is a key software tool for the PLATO mission in the preparatory phases until mission launch and prospectively beyond.
By combining ground-based spectrographic observations of variability in the chromospheric emission from Sun-like stars with the variability seen in their eigenmode frequencies, it is possible to ...relate the changes observed at the surfaces of these stars to the changes taking place in the interior. By further comparing this variability to changes in the relative flux from the stars, one can obtain an expression for how these activity indicators relate to the energy output from the stars. Such studies become very pertinent when the variability can be related to stellar cycles as they can then be used to improve our understanding of the solar cycle and its effect on the energy output from the Sun. Here we present observations of chromospheric emission in 20 Sun-like stars obtained over the course of the nominal 4-year Kepler mission. Even though 4 years is too short to detect stellar equivalents of the 11-year solar cycle, observations from the Kepler mission can still be used to analyse the variability of the different activity indicators thereby obtaining information of the physical mechanism generating the variability. The analysis reveals no strong correlation between the different activity indicators, except in very few cases. We suggest that this is due to the sparse sampling of our ground-based observations on the one hand and that we are likely not tracing cyclic variability on the other hand. We also discuss how to improve the situation.
•High antibiotic use in hospitalized children Sanandaj, Iran 75% and South-East Asia 57%.•High use of Watch antibiotics (83%) and absence of laboratory diagnostic capacity in Sanandaj, Iran.•Training ...on appropriate antibiotic prescribing needs to be strengthened.
Point prevalence surveys (PPS) provide valuable data on patterns of hospital antimicrobial administration. To identify quality improvement indicators, we evaluated antimicrobial prescribing patterns in children and neonates admitted to three referral centres in Sanandaj, Western Iran, and compared these with Southeast Asian and European paediatric benchmark data.
The standardised Global-PPS was performed to assess antimicrobial use in Southeast Asia, including Sanandaj and European hospitals, in 2019.
Of the 4118, 2915, and 443 paediatric patients enrolled in Southeast Asian, European and Sanandaj hospitals, 2342 (56.9%), 833 (28.6%) and 332 (74.9%), respectively, received at least one antimicrobial in 2019. The most administered antibiotics in neonates were ampicillin in Southeast Asia (30.3%) and Sanandaj (41.5%, often in combination with cefotaxime (29.0%)), compared with amoxicillin in Europe (20.0%). In children, ceftriaxone was most prescribed in Sanandaj (62.4%) and Southeast Asia (20.5%) as opposed to amoxicillin (11.8%) in Europe. Twice as many Watch antibiotics (83.0%) were prescribed on paediatric wards in Sanandaj compared with European paediatric wards (41.1%). All antimicrobials in Sanandaj hospitals were prescribed empirically, and prolonged surgical prophylaxis was common (75.5%).
The high prevalence of antibiotic prescribing, high empirical therapies, and poor outcomes for antibiotic quality indicators strongly suggest the urgent need for an antibiotic stewardship program in Sanandaj hospitals, where improved diagnostic laboratory capacity and reconsideration of training may be good targets for intervention in their hospitals.
PLAnetary Transits and Oscillations of stars (PLATO) is the ESA M3 space mission dedicated to detect and characterise transiting exoplanets including information from the asteroseismic properties of ...their stellar hosts. The uninterrupted and high-precision photometry provided by space-borne instruments such as PLATO require long preparatory phases. An exhaustive list of tests are paramount to design a mission that meets the performance requirements, and as such, simulations are an indispensable tool in the mission preparation. To accommodate PLATO's need of versatile simulations prior to mission launch - that at the same time describe accurately the innovative but complex multi-telescope design - we here present the end-to-end PLATO simulator specifically developed for the purpose, namely PlatoSim. We show step-by-step the algorithms embedded into the software architecture of PlatoSim that allow the user to simulate photometric time series of CCD images and light curves in accordance to the expected observations of PLATO. In the context of the PLATO payload, a general formalism of modelling, end-to-end, incoming photons from the sky to the final measurement in digital units is discussed. We show the strong predictive power of PlatoSim through its diverse applicability and contribution to numerous working groups within the PLATO Mission Consortium. This involves the on-going mechanical integration and alignment, performance studies of the payload, the pipeline development and assessments of the scientific goals. PlatoSim is a state-of-the-art simulator that is able to produce the expected photometric observations of PLATO to a high level of accuracy. We demonstrate that PlatoSim is a key software tool for the PLATO mission in the preparatory phases until mission launch and prospectively beyond.
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