Abstract
The NASA Transiting Exoplanet Survey Satellite (TESS) is observing tens of millions of stars with time spans ranging from ∼27 days to about 1 yr of continuous observations. This vast amount ...of data contains a wealth of information for variability, exoplanet, and stellar astrophysics studies but requires a number of processing steps before it can be fully utilized. In order to efficiently process all the TESS data and make it available to the wider scientific community, the TESS Data for Asteroseismology working group, as part of the TESS Asteroseismic Science Consortium, has created an automated open-source processing pipeline to produce light curves corrected for systematics from the short- and long-cadence raw photometry data and to classify these according to stellar variability type. We will process all stars down to a TESS magnitude of 15. This paper is the next in a series detailing how the pipeline works. Here, we present our methodology for the automatic variability classification of TESS photometry using an ensemble of supervised learners that are combined into a metaclassifier. We successfully validate our method using a carefully constructed labeled sample of Kepler Q9 light curves with a 27.4 days time span mimicking single-sector TESS observations, on which we obtain an overall accuracy of 94.9%. We demonstrate that our methodology can successfully classify stars outside of our labeled sample by applying it to all ∼167,000 stars observed in Q9 of the Kepler space mission.
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.
The near-field - far-field disparity of light sources leads to discussion within the lighting community. In the far-field, light sources are approximated by a point source with a luminous intensity ...distribution from which other photometric quantities can be computed. In the near-field, light sources must be considered as extended sources and no closed-loop analytical solutions can be found for the illuminance in off-axis directions. The illuminance allows to compute the apparent intensity used for the assessment of the limiting photometric distance (LPD), that is, the threshold between near- and far-field regions. Numerically, the illuminance can be determined through a discretisation of the luminous surface. This approach is verified for on- and off-axis directions through direct comparison with ray tracing simulations based on near-field goniophotometric measurements. A good match is observed for Lambertian and narrow beam light sources. Using the numerical approach, the LPD in all directions is assessed. For light sources of which the luminous intensity strictly decreases while moving away from the optical axis, the LPD decreases as well until a minimal value is reached. After this, the LPD increases again, in certain scenarios up to values resulting in the invalidity of the inverse square law.
Context.
The multiscale entropy assesses the complexity of a signal across different timescales. It originates from the biomedical domain and was recently successfully used to characterize light ...curves as part of a supervised machine learning framework to classify stellar variability.
Aims.
We aim to explore the behavior of the multiscale entropy in detail by studying its algorithmic properties in a stellar variability context and by linking it with traditional astronomical time series analysis methods and metrics such as the Lomb-Scargle periodogram. We subsequently use the multiscale entropy as the basis for an interpretable clustering framework that can distinguish hybrid pulsators with both
p
- and g-modes from stars with only
p
-mode pulsations, such as
δ
Scuti (
δ
Sct) stars, or from stars with only
g
-mode pulsations, such as
γ
Doradus (
γ
Dor) stars.
Methods.
We calculate the multiscale entropy for a set of
Kepler
light curves and simulated sine waves. We link the multiscale entropy to the type of stellar variability and to the frequency content of a signal through a correlation analysis and a set of simulations. The dimensionality of the multiscale entropy is reduced to two dimensions and is subsequently used as input to the HDBSCAN density-based clustering algorithm in order to find the hybrid pulsators within sets of
δ
Sct and
γ
Dor stars that were observed by
Kepler
.
Results.
We find that the multiscale entropy is a powerful tool for capturing variability patterns in stellar light curves. The multiscale entropy provides insights into the pulsation structure of a star and reveals how short- and long-term variability interact with each other based on time-domain information only. We also show that the multiscale entropy is correlated to the frequency content of a stellar signal and in particular to the near-core rotation rates of
g
-mode pulsators. We find that our new clustering framework can successfully identify the hybrid pulsators with both
p
- and
g
-modes in sets of
δ
Sct and
γ
Dor stars, respectively. The benefit of our clustering framework is that it is unsupervised. It therefore does not require previously labeled data and hence is not biased by previous knowledge.
Remote phosphor light-emitting diode (LED) modules could offer advantages over intimate white phosphor converted LEDs in terms of phosphor operation temperature, light extraction efficiency, and ...angular color uniformity. Existing commercial devices show a large variety with respect to the dimensions of the mixing cavity, which raises a question about the optimization of the topology. A simplified simulation model applying a two-wavelength approach and considering the remote phosphor as one virtual surface to which three bidirectional scattering distribution functions are attributed (respectively, describing the blue-blue, blue-yellow, and yellow-yellow interactions) is developed and validated. This model has been used to analyze the impact of the cylindrical mixing cavity parameters such as the absolute reflectance, the diffuse-to-specular reflectance ratio, and the height of the mixing cavity, as well as the pitch and angular full-width at half-maximum of the LEDs on the extraction efficiency, the yellow-to-blue ratio, and the irradiance uniformity. It can be concluded that in order to increase the efficacy substantially, the recuperation of the backward emission of the converted light can only be increased by avoiding further interaction with the phosphor plate. To this extent, topologies other than cylindrical mixing cavities must be considered.
Contact.
MWC 656 was reported to be the first known Be star with a black-hole (BH) companion on a 60 d period. The mass of the proposed BH companion is estimated to be between 4 and 7
M
⊙
. This ...estimate is based on radial velocity (RV) measurements derived from the Fe
II
λ
4583 emission line of the Be star disc and from the He
II
λ
4686 emission line, assumed to be formed in a disc around the putative BH.
Aims.
Using new high-resolution spectroscopic data, we investigate whether MWC 656 truly contains a BH.
Methods.
We used the cross-correlation method to calculate the RVs of both the Be star and the He
II
λ
4686 emission line to derive a new orbital solution. We also used a spectral disentangling method to look for the spectral signature of a companion.
Results.
We derived an orbital period of 59.028 ± 0.011 d and a mass ratio of
q
=
M
He
II
/
M
Be
= 0.12 ± 0.03, much lower than the previously reported value of
q
= 0.41 ± 0.07. By adopting a mass for the Be star of
M
Be
= 7.8 ± 2.0
M
⊙
, the mass of the companion is 0.94 ± 0.34
M
⊙
. For the upper limit of
M
Be
= 16
M
⊙
and
q
= 0.15, the mass of the companion is 2.4
M
⊙
. Performing the disentangling on mock spectra shows that the spectral signature of a non-degenerate stellar companion with such a low mass cannot be retrieved using our data.
Conclusions.
Our measurements do not support the presence of a BH companion in MWC 656. Rather, the derived upper limit on the mass of the companion indicates that it is either a neutron star, a white dwarf, or a hot helium star. Far-UV data will aid in rejecting or confirming a hot helium-star companion.
If a grower uses predatory mites, and should use chemical compounds, he needs to be very careful in his choice of products. The selected products have to be efficient against the target pest and at ...the same time compatible with the present beneficial's. Useful tools for such product selection under greenhouse circumstances are side effects lists. These lists are freely available on the websites of producing companies of biological control agents. But not all products (e.g. newly developed ones) have been tested for side effects. Moreover the information already available in these tables is not based on field tests. For this reason, we have developed a protocol for quick screening of side effects of chemical plant protection products under field conditions. For these experiments we have chosen the predatory mite Amblyseius swirskii as test organism, because this is an often used phytoseiid mite, which is very sensitive to pesticides. Hibiscus rosa sinensis is the standard reference plant in our side effects trials because the chosen predatory mite has shown very good control of pests on this plant species. The experimental design consists of eight test objects in 4 replications. Test object 1 is a positive reference (water spray) and test object 2 a negative reference (deltamethrin spray, a product with long residual activity against beneficial organisms). The plot size is 0,68 m2 and each plot contains 32 Hibiscus plants. The greenhouse temperature is set at 20±2°C. The test strategy has the following sequence: introduction of an overdose of Amblyseius swirskii mites 14 days before spraying the pesticides > precount of predatory mites 4 days before application (4DBA) > spray application (A) for the 6 test products and for the 2 references > counting's after application (1, 2, 4, 8 en 12 weeks after application = 1 till 12WAA). The counting's of the number of predatory mites are performed on 20 Hibiscus leaves/plot under a binocular. Because of the absence of any food sources for the A. swirskii mites, it's necessary to re-introduce a high dose of predatory mites in the Hibiscus crop every 4 weeks, especially 2 weeks before the counting's 4, 8 and 12WAA; these introductions are carried out by hanging out 7 sachets with predatory mites (250 mites/sachet or 2500 mites/m2) on each test plot and after 10 days they are removed. In our first experiments the following commercial products have been tested: Pyrethro Pur (rapeseed oil + pyrethrins), Actara (thiamethoxam), Rizolex 500 SC (tolclofos-methyl), Topsin 500 SC (thiophanate-methyl), Floramite 240 SC (bifenazate), Cycocel 75 (chlorrmequat chloride), Vertimec (abamectin), Match (lufenuron), Nocturn (pyridalyl), Neemazal-T/S (azadirachtin), Tracer (spinosad), Envidor (spirodiclofen), Carex 10SC (pyridaben), Nissorun (hexythiazox) and Scelta (cyflumetofen). As expected the water treatment was safest for A. swirskii and deltamethrin killed most of the mites, even if they were re-introduced after 8 or 12 weeks. Also pyrethrins and spinosad showed very negative effects. Abamectin and bifenazate showed intermediate negative effects and should be used with caution. The other products were safe to use in combination with predatory mites. These screening tests will be repeated yearly with new and popular products of which the side effects in practice are currently uncertain.
Outbreaks of the broad mite Polyphagotarsonemus latus cause serious economic damage in ornamental horticulture. Control of broad mites proves to be a serious challenge for growers. Good control ...throughout the crop cycle requires optimization and integration of chemical and non-chemical strategies. In this paper we describe results of trials testing the efficacy and applicability of 3 complementary control strategies: chemical, biological and physical. Field trials on two sensitive woody ornamental plants: Hedera and Azalea (Rhododendron simsii cultivars) show the value of these strategies. We test the strength of these independent strategies and suggest how these could be alternated to control broad mites throughout the production cycle.
Predatory mites like Phytoseiulus persimilis Athias-Henriot, Neoseiulus californicus McGregor and N. fallacis (Garman) (Acari: Phytoseiidae) are essential in sustainable control strategies of the ...two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae) in warm greenhouse cultures to complement imited available pesticides and to tackle emerging resistance. However, in response to high energy prices, greenhouse plant breeders have recently changed their greenhouse steering strategies, allowing more variation in temperature and humidity. The impact of these variations on biological control agents is poorly understood. Therefore, we constructed functional response models to demonstrate the impact of realistic climate variations on predation efficiency. First, two temperature regimes were compared at constant humidity (70%) and photoperiod (16L:8D): DIF0 (constant temperature) and DIF15 (variable temperature with day-night difference of 15°C). At mean temperatures of 25°C, DIF15 had a negative influence on the predation efficiency of P. persimilis and N. californicus, as compared to DIF0. At low mean temperatures of 15°C, however, DIF15 showed a higher predation efficiency for P. persimilis and N. californicus. For N. fallacis no difference was observed at both 15°C and 25°C. Secondly, two humidity regimes were compared, at a mean temperature of 25°C (DIFO) and constant photoperiod (16L:8D): RHCTE (constant 70% humidity) and RHALT (alternating 40% L:70%D humidity). For P. persimilis and N. fallacis RHCTE resulted in a higher predation efficiency than RHALT, for N. californicus this effect was opposite. This shows that N. californicus is more adapted to dry climates as compared to the other predatory mites. We conclude that variable greenhouse climates clearly affect predation efficiency of P. persimilis, N. californicus and N. fallacis. To obtain optimal control efficiency, the choice of predatory mites (including dose and application frequency) should be adapted to the actual greenhouse climate.
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