# Browsing by Subject "spectrum analysis"

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Item Discovery Of Binarity, Spectroscopic Frequency Analysis, And Mode Identification Of The Delta Scuti Star 4 CVn(2014-10) Schmid, V. S.; Themessl, N.; Breger, M.; Degroote, P.; Aerts, C.; Beck, P. G.; Tkachenko, A.; Van Reeth, T.; Bloemen, S.; Debosscher, J.; Castanheira, B. G.; McArthur, B. E.; Papics, P. I.; Fritz, V.; Falcon, R. E.; Castanheira, B. G.; McArthur, B. E.; Falcon, R. E.Show more More than 40 years of ground-based photometric observations of the delta Sct star 4 CVn has revealed 18 independent oscillation frequencies, including radial as well as non-radial p-modes of low spherical degree l <= 2. From 2008 to 2011, more than 2000 spectra were obtained at the 2.1m Otto-Struve telescope at the McDonald Observatory. We present the analysis of the line-profile variations, based on the Fourier-parameter fit method, detected in the absorption lines of 4 CVn, which carry clear signatures of the pulsations. From a non-sinusoidal, periodic variation of the radial velocities, we discover that 4 CVn is an eccentric binary system with an orbital period P-orb = 124.44 +/- 0.03 d and an eccentricity e = 0.311 +/- 0.003. We detect 20 oscillation frequencies, 9 of which previously unseen in photometric data; attempt mode identification for the two dominant modes, f(1) = 7.3764 d(-1) and f(2) = 5.8496 d(-1); and determine the prograde or retrograde nature of 7 of the modes. The projected rotational velocity of the star, v(eq) sin i similar or equal to 106.7 km s(-1), translates to a rotation rate of v(eq)/v(crit) >= 33%. This relatively high rotation rate hampers unique mode identification, since higher order effects of rotation are not included in the current methodology. We conclude that, in order to achieve unambiguous mode identification for 4CVn, a complete description of rotation and the use of blended lines have to be included in mode-identification techniques.Show more Item Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: are there Cosmic Microwave Background Anomalies?(2011-02) Bennett, C. L.; Hill, R. S.; Hinshaw, G.; Larson, D.; Smith, K. M.; Dunkley, J.; Gold, B.; Halpern, M.; Jarosik, N.; Kogut, A.; Komatsu, Eiichiro; Limon, M.; Meyer, S. S.; Nolta, M. R.; Odegard, N.; Page, L.; Spergel, D. N.; Tucker, G. S.; Weiland, J. L.; Wollack, E.; Wright, E. L.; Komatsu, EiichiroShow more A simple six-parameter Lambda CDM model provides a successful fit to WMAP data. This holds both when the WMAP data are analyzed alone or in combination with other cosmological data. Even so, it is appropriate to examine the data carefully to search for hints of deviations from the now standard model of cosmology, which includes inflation, dark energy, dark matter, baryons, and neutrinos. The cosmological community has subjected the WMAP data to extensive and varied analyses. While there is widespread agreement as to the overall success of the six-parameter Lambda CDM model, various "anomalies" have been reported relative to that model. In this paper we examine potential anomalies and present analyses and assessments of their significance. In most cases we find that claimed anomalies depend on posterior selection of some aspect or subset of the data. Compared with sky simulations based on the best-fit model, one can select for low probability features of the WMAP data. Low probability features are expected, but it is not usually straightforward to determine whether any particular low probability feature is the result of the a posteriori selection or non-standard cosmology. Hypothesis testing could, of course, always reveal an alternative model that is statistically favored, but there is currently no model that is more compelling. We find that two cold spots in the map are statistically consistent with random cosmic microwave background (CMB) fluctuations. We also find that the amplitude of the quadrupole is well within the expected 95% confidence range and therefore is not anomalously low. We find no significant anomaly with a lack of large angular scale CMB power for the best-fit Lambda CDM model. We examine in detail the properties of the power spectrum data with respect to the Lambda CDM model and find no significant anomalies. The quadrupole and octupole components of the CMB sky are remarkably aligned, but we find that this is not due to any single map feature; it results from the statistical combination of the full-sky anisotropy fluctuations. It may be due, in part, to chance alignments between the primary and secondary anisotropy, but this only shifts the coincidence from within the last scattering surface to between it and the local matter density distribution. While this alignment appears to be remarkable, there was no model that predicted it, nor has there been a model that provides a compelling retrodiction. We examine claims of a hemispherical or dipole power asymmetry across the sky and find that the evidence for these claims is not statistically significant. We confirm the claim of a strong quadrupolar power asymmetry effect, but there is considerable evidence that the effect is not cosmological. The likely explanation is an insufficient handling of beam asymmetries. We conclude that there is no compelling evidence for deviations from the Lambda CDM model, which is generally an acceptable statistical fit to WMAP and other cosmological data.Show more