51 research outputs found
Period and period change measurements for 143 SuperWASP eclipsing binary candidates near the short-period limit and discovery of a doubly eclipsing quadruple system
Building on previous work, a new search of the SuperWASP archive was carried out to identify eclipsing binary systems near the short-period limit. 143 candidate objects were detected with orbital periods between 16 000 and 20 000 s, of which 97 are new discoveries. Period changes significant at 1σ or more were detected in 74 of these objects, and in 38 the changes were significant at 3σ or more. The significant period changes observed followed an approximately normal distribution with a half-width at half-maximum of ~0.1 s yr-1. There was no apparent relationship between period length and magnitude or direction of period change. Amongst several interesting individual objects studied, 1SWASP J093010.78+533859.5 is presented as a new doubly eclipsing quadruple system, consisting of a contact binary with a 19 674.575 s period and an Algol-type binary with a 112 799.109 s period, separated by 66.1 AU, being the sixth known system of this type
A dominant magnetic dipole for the evolved Ap star candidate EK Eridani
EK Eri is one of the most slowly rotating active giants known, and has been
proposed to be the descendant of a strongly magnetic Ap star. We have performed
a spectropolarimetric study of EK Eri over 4 photometric periods with the aim
of inferring the topology of its magnetic field. We used the NARVAL
spectropolarimeter at the Bernard Lyot telescope at the Pic du Midi
Observatory, along with the least-squares deconvolution method, to extract high
signal-to-noise ratio Stokes V profiles from a timeseries of 28 polarisation
spectra. We have derived the surface-averaged longitudinal magnetic field Bl.
We fit the Stokes V profiles with a model of the large-scale magnetic field and
obtained Zeeman Doppler images of the surface magnetic strength and geometry.
Bl variations of up to about 80 G are observed without any reversal of its
sign, and which are in phase with photometric ephemeris. The activity
indicators are shown to vary smoothly on a timescale compatible with the
rotational period inferred from photometry (308.8 d.), however large deviations
can occur from one rotation to another. The surface magnetic field variations
of EK Eri appear to be dominated by a strong magnetic spot (of negative
polarity) which is phased with the dark (cool) photometric spot. Our modeling
shows that the large-scale magnetic field of EK Eri is strongly poloidal. For a
rotational axis inclination of i = 60{\deg}, we obtain a model that is almost
purely dipolar. In the dipolar model, the strong magnetic/photometric spot
corresponds to the negative pole of the dipole, which could be the remnant of
that of an Ap star progenitor of EK Eri. Our observations and modeling
conceptually support this hypothesis, suggesting an explanation of the
outstanding magnetic properties of EK Eri as the result of interaction between
deep convection and the remnant of an Ap star magnetic dipole.Comment: 8 pages, 6 figures, accepted for publication in Astronomy &
Astrophysic
Improved pulsating models of magnetic Ap stars I: exploring different magnetic field configurations
Magnetic perturbations to the frequencies of low degree, high radial order,
axisymmetric pulsations in stellar models permeated by large scale magnetic
fields are presented. Magnetic fields with dipolar, quadrupolar and a
superposition of aligned dipolar and quadrupolar components are considered.
The results confirm that the magnetic field may produce strong anomalies in
the power spectra of roAp stars. It is shown for the first time that anomalies
may result both from a sudden decrease or a sudden increase of a mode
frequency. Moreover, the results indicate that the anomalies depend essentially
on the geometry of the problem, i.e., on the configuration of the magnetic
field and on the degree of the modes. This dependence opens the possibility of
using these anomalies as a tool to learn about the magnetic field configuration
in the magnetic boundary layer of pulsating stars permeated by large scale
magnetic fields
Orbital period changes and the higher-order multiplicity fraction amongst SuperWASP eclipsing binaries
Orbital period changes of binary stars may be caused by the presence of a third massive body in the system. Here we have searched the archive of the Wide Angle Search for Planets (SuperWASP) project for evidence of period variations in 13 927 eclipsing binary candidates. Sinusoidal period changes, strongly suggestive of third bodies, were detected in 2% of cases; however, linear period changes were observed in a further 22% of systems. We argue on distributional grounds that the majority of these apparently linear changes are likely to reflect longer-term sinusoidal period variations caused by third bodies, and thus estimate a higher-order multiplicity fraction of 24% for SuperWASP binaries, in good agreement with other recent figures for the fraction of triple systems amongst binary stars in general
Elastic properties prediction of nano-clay reinforced polymer using multi-scale modeling based on a multi-scale characterization
International audienc
Wybrane aspekty organizacji procesów logistyki zwrotnej odpadów opakowaniowych w przedsiębiorstwie produkcyjnym
The paper discusses the problems of the efficiency of selected aspects of the organization of the processes of reverse logistics of packaging waste in manufacturing enterprises. On the basis of the analysis of background literature, current legal standards and strategic documents, benefits resulting from its application are shown, and legal obligations of entrepreneurs are presented.W artykule omówiono problematykę skuteczności wybranych aspektów organizacji procesów logistyki zwrotnej odpadów opakowaniowych, w przedsiębiorstwie produkcyjnym. Na podstawie analizy piśmiennictwa, aktualnych norm prawnych i dokumentów strategicznych wykazano korzyści wynikające z jej stosowania oraz przedstawiono prawne obowiązki przedsiębiorców
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