69 research outputs found
Fourier analysis of gapped time series: Improved estimates of solar and stellar oscillation parameters
No full textQuantitative helioseismology and asteroseismology require very precise measurements of the frequencies, amplitudes, and lifetimes of the global modes of stellar oscillation. The precision of these measurements depends on the total length (T), quality, and completeness of the observations. Except in a few simple cases, the effect of gaps in the data on measurement precision is poorly understood, in particular in Fourier space where the convolution of the observable with the observation window introduces correlations between different frequencies. Here we describe and implement a rather general method to retrieve maximum likelihood estimates of the oscillation parameters, taking into account the proper statistics of the observations. Our fitting method applies in complex Fourier space and exploits the phase information. We consider both solar-like stochastic oscillations and long-lived harmonic oscillations, plus random noise. Using numerical simulations, we demonstrate the existence of cases for which our improved fitting method is less biased and has a greater precision than when the frequency correlations are ignored. This is especially true of low signal-to-noise solar-like oscillations. For example, we discuss a case where the precision of the mode frequency estimate is increased by a factor of five, for a duty cycle of 15%. In the case of long-lived sinusoidal oscillations, a proper treatment of the frequency correlations does not provide any significant improvement; nevertheless, we confirm that the mode frequency can be measured from gapped data with a much better precision than the 1/T Rayleigh resolution
Pengembangan Media Pada Mata Pelajaran IPA Materi Tumbuhan Untuk Siswa
No full textThe purpose of this research is to produce products from the development of plant material media for elementary/MI students. This research uses research and development methods which use the development model procedure developed by Borg & Gall. In this research, the author limits it to the product development process. The dissemination process and large-scale testing will be written separately in another article. From this development, a product was produced in the form of media that uses the Articulate Storyline 3 application which can combine graphics and animation so it is very suitable for elementary school students. The use of computer-based technology is a way to produce or convey material using technology-based sources, where the information or material presented is stored in digital form. The author is here to provide a solution through the development of media related to plant material that can overcome problems for elementary school students
SDSS J212531.92–010745.9 : the first definite PG 1159 close binary system
No full textAims. The archival spectrum of SDSS J212531.92−010745.9 shows not only the typical signature of a PG 1159 star, but also indicates the presence of a companion. Our aim was the proof of the binary nature of this object and the determination of its orbital period.
Methods. We performed time-series photometry of SDSS J212531.92−010745.9. We observed the object during 10 nights, spread over one month, with the Tübingen 80 cm and the Göttingen 50 cm telescopes. We fitted the observed light curve with a sine and simulated the light curve of this system with the nightfall program. Furthermore, we compared the spectrum of SDSS J212531.92−010745.9 with
NLTE models, the results of which also constrain the light curve solution.
Results. An orbital period of 6.95616(33) h with an amplitude of 0.354(3) mag is derived from our observations. A pulsation period could not be detected. For the PG 1159 star we found, as preliminary results from comparison with our NLTE models, T eff ∼ 90 000 K, log g ∼ 7.60, and the abundance ratio C/He ∼ 0.05 by number fraction. For the companion we obtained with a mean radius of 0.4 ± 0.1 R, a mass of 0.4 ± 0.1 M, and a temperature of 8200 K on the irradiated side, good agreement between the observed light curve and the nightfall simulation, but we do not regard those values as final
Zeitreihenanalyse sonnenähnlicher Oszillationen Anwendung auf Beobachtungen der Sonne und HD52265
No full textDie Untersuchung von Schwingungen in Sternen erlaubt es, den inneren Aufbau und die Dynamik der Sterne mit einer Genauigkeit zu bestimmen, die mit keiner anderen Methode erreicht werden kann. Den Schwerpunkt der vorliegenden Dissertation bildet die Messung der Parameter (Frequenzen, Amplituden, Linienbreiten und rotationsbedingte Frequenzaufspaltung) der globalen Moden sonnenähnlicher Schwingungen, die in der Sonne und dem sonnenähnlichen Stern HD52265 beobachtet wurden. Die Arbeit ist in drei Hauptteile gegliedert: (i) Die Implementierung und Validierung eines globalen Fits stellarer Schwingungsspektren anhand von Sonnenbeobachtungen, (ii) die Anwendung dieser Methode auf eine viermonatige CoRoT-Beobachtung des sonnenähnlichen Sterns HD52265, der außerdem von einem Planeten umkreist wird, sowie (iii) die Erweiterung der Auswertungsmethode auf Zeitreihen mit Unterbrechungen. Die Hauptergebnisse meiner Arbeit betreffen HD52265: Die Schwingungsfrequenzen der Radial-, Dipol- und Quadrupolmoden wurden mit der höchsten, jemals für einen sonnenähnlichen Stern erreichten Genauigkeit gemessen. Zum ersten Mal konnte der Effekt der stellaren Rotation auf die Schwingungsmoden zweifelsfrei für einen sonnenähnlichen Stern nachgewiesen werden. Außerdem erlaubte uns die seismologische Messung der Neigung der Rotationsachse des Sterns, die absolute Masse des Begleiters abzuschätzen. Demzufolge legt die asteroseismologische Untersuchung nahe, dass es sich bei dem Begleiter um einen Planeten und nicht um einen Braunen Zwerg handelt.The study of stellar oscillations allows one to constrain the structure and dynamics of stellar interiors to a precision that cannot be achieved with other methods. This dissertation focusses on the measurements of the parameters (frequencies, amplitudes, linewidths, and rotational splitting) of the global modes of solar-like oscillations observed in the Sun and in the Sun-like star HD52265. The thesis is organized in three main parts: (i)~an implementation and validation of a global fit of stellar oscillation power spectra using solar observations, (ii) an application of this method to original 4-month-long CoRoT observations of the planet-hosting, solar-like star HD52265, and (iii) an extension of the fitting method to time series with gaps. The main results concern HD52265: the mode frequencies of the radial, dipole and quadrupole modes are measured with the highest precision achieved so far for a solar-type star and, for the first time, the effect of rotation on oscillations in a solar-type star are measured without a doubt. Furthermore, the seismic constraint on the inclination angle of the stellar rotation axis allows us to estimate the absolute mass of the companion. Accordingly the seismic analysis strongly suggests that the companion is a planet and not a brown dwarf
Media Ekopedagik Dalam Pembelajaran (TPS) Think Pair Share Untuk Menunjang Hasil Belajar Peserta Didik
No full textIn this paper, the author tries to relate the literature study related to the comparison of Eco pedagogic media with TPS (Think Pair Share) learning in supporting student learning outcomes. From several studies such as relevant studies coupled with supporting theories, it is stated that Eco pedagogic media and TPS (Think Pair Share) models will provide broad opportunities for students to be able to think and train their reasoning so that students can then work together in groups. and can explain and provide information to other students. Of course, the information obtained is sourced from Eco pedagogic media in the form of the surrounding environment. The hope is that this Eco pedagogic media in TPS (Think Pair Share) learning can be used as a reference for every educator in creating an optimal learning atmosphere
Fourier Analysis of Gapped Time Series: Improved Estimates of Solar and Stellar Oscillation Parameters
No full textParameters of Sustainable Peace:UN Frameworks and Practice
No full textThis chapter examines normative principles for peacemakers and peacebuilding that define the parameters for just and sustainable peace in the UN system. It argues that an ‘imperfect’ peace is better than ‘just war’. It shows that UN notions of peace have been developed through practice. It explores how just peace approaches intersect with the UN peacebuilding architecture and Sustainable Development Goal 16. The author identifies core principles which shape UN post-conflict transitions, such as national ownership, inclusivity, rule of law, effective leadership, coordination, and accountability.<br/
Interview Transcripts on Conditions For Study Success (WiSe 2022/23)
No full textThis dataset contains raw interview data (transcripts) from a seminar on study success requirements ("Lernerfolgsbedingungen im Hochschulstudium", Universität Stuttgart) in winter 2022/23. Students are narrating their experiences with a wide range of topics regarding their learning and study conditions, and their impact on study success.The interviews are best characterized as problem-centered interviews with strong narrative elements
Den Wald ihr sollet lassen stahn! (Essay)
No full textThe author gives his reflections on the changes in the Swiss landscape in answer to questions posed by the editor. But beforehand he establishes the fact that there are two relationships to the forest, the sentimental and the practical, and that these two correspond in no respect. The change in the landscape has two causes: the intensification of use and our prosperity. Approximately two million more inhabitants plus double the surface required for habitation equals urban sprawl. The laws governing land use planning are helpless to prevent this. They are nothing but an attempt to carry out urban sprawl in an orderly fashion. Only a consistent levy on the added value and cost transparency could stop urban sprawl. This is however prevented by the political coalition of the promoters of urban sprawl. The clearance ban must continue to be in force. Only projects tied up with a given location can be permitted. This must be understood as places offering locational advantages. Should forest be cleared for urban development then, in addition to reforestation, the same surface area of building land won by the clearance must be rezoned as non-building land in the agglomeration. We have too much money, that is what does most damage to the forest.</jats:p
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