Pulsation of EE Cam

EE Cam is a previously little studied Delta Scuti pulsator with amplitudes between those of the HADS (High-Amplitude Delta Scuti stars) group and the average low-amplitude pulsators. Since the size of stellar rotation determines both which pulsation modes are selected by the star as well as their amplitudes, the star offers a great opportunity to examine the astrophysical connections. Extensive photometric measurements covering several months were carried out. 15 significant pulsation frequencies were extracted. The dominant mode at 4.934 cd$^{-1}$ was identified as a radial mode by examining the phase shifts at different wavelengths. Medium-dispersion spectra yielded a $v\sin i$ value of $40 \pm 3$ km s$^{-1}$. This shows that EE Cam belongs to the important transition region between the HADS and normal Delta Scuti stars.Comment: 13 pages, 3 figures, 3 table

Deus não pode ser conhecido. A incognoscibilidade divina no Livro dos XXIV Filósofos (XVI e XVII) e suas raízes na tradição filosófica ocidental

O Livro dos XXIV Filósofos apresenta nos enunciados XVI e XVII a inefabilidade de Deus, por causa de sua excelência e pelo fato de Deus ser pensamento de Si mesmo. Qual a dimensão e a fundamentação desta afirmação? Neste estudo tenta-se fazer ver que ela não é, na filosofia antiga e medieval, um fato isolado, mas que faz parte de uma longa tradição da qual faz parte o Neoplatonismo, tanto nos seus autores clássicos, como também no Livro das Causas.The Liber XXIV Philosophorum in its XVIth e XVIIth thesis tells us about the ineffability of God as a consequence of His excellence and also in view of the fact that God can only think Himself. In this paper we will try to examine the base and dimensions of this statement, studying it as a part of a long tradition in ancient and medieval philosophy, i.e. Neoplatonism, and especially in the Liber de Causis

God Can not be Understood. God's Incomprehensibility in the Liber XXIV philosophorum (Chapters XVI & XVII) and its Roots in the Western Philosophical Tradition.

The Liber XXIV Philosophorum in its XVIth e XVIIth thesis tells us about the ineffability of God as a consequence of His excellence and also in view of the fact that God can only think Himself. In this paper we will try to examine the base and dimensions of this statement, studying it as a part of a long tradition in ancient and medieval philosophy, i. e. Neoplatonism, and especially in the Liber de Causis

A heuristic derivation of the uncertainty of the frequency determination in time series data

Context: Several approaches to estimate frequency, phase and amplitude errors in time series analyses were reported in the literature, but they are either time consuming to compute, grossly overestimating the error, or are based on empirically determined criteria. Aims: A simple, but realistic estimate of the frequency uncertainty in time series analyses. Methods: Synthetic data sets with mono- and multi-periodic harmonic signals and with randomly distributed amplitude, frequency and phase were generated and white noise added. We tried to recover the input parameters with classical Fourier techniques and investigated the error as a function of the relative level of noise, signal and frequency difference. Results: We present simple formulas for the upper limit of the amplitude, frequency and phase uncertainties in time-series analyses. We also demonstrate the possibility to detect frequencies which are separated by less than the classical frequency resolution and that the realistic frequency error is at least 4 times smaller than the classical frequency resolution

Unevenly-sampled signals: a general formalism of the Lomb-Scargle periodogram

The periodogram is a popular tool that tests whether a signal consists only of noise or if it also includes other components. The main issue of this method is to define a critical detection threshold that allows identification of a component other than noise, when a peak in the periodogram exceeds it. In the case of signals sampled on a regular time grid, determination of such a threshold is relatively simple. When the sampling is uneven, however, things are more complicated. The most popular solution in this case is to use the "Lomb-Scargle" periodogram, but this method can be used only when the noise is the realization of a zero-mean, white (i.e. flat-spectrum) random process. In this paper, we present a general formalism based on matrix algebra, which permits analysis of the statistical properties of a periodogram independently of the characteristics of noise (e.g. colored and/or non-stationary), as well as the characteristics of sampling.Comment: 10 pages, 11 figures, Astronomy and Astrophysics, in pres