Further development and properties of the spectral analysis by least-squares

Vaníček, Petr

doi:10.1007/bf00656134

Cited by 290 publications

(171 citation statements)

References 2 publications

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“…Fortunately, Lomb (1976) developed a method of spectral analysis without such shortcomings. This method was based in part on earlier works by Barning (1963) and Vaníček (1971) and was elaborated further by Scargle (1982). They evaluate the spectra with the use of data that are actually measured, and, moreover, the measurements can be unevenly sampled.…”

Section: Data Selection and Analysis Proceduresmentioning

confidence: 99%

On nonstationarity and rippling of the quasiperpendicular zone of the Earth bow shock: Cluster observations

et al. 2008

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Abstract. A new method for remote sensing of the quasiperpendicular part of the bow shock surface is presented. The method is based on analysis of high frequency electric field fluctuations corresponding to Langmuir, upshifted, and downshifted oscillations in the electron foreshock. Langmuir waves usually have maximum intensity at the upstream boundary of this region. All these waves are generated by energetic electrons accelerated by quasiperpendicular zone of the shock front. Nonstationary behavior of the shock, in particular due to rippling, should result in modulation of energetic electron fluxes, thereby giving rise to variations of Langmuir waves intensity. For upshifted and downshifted oscillations, the variations of both intensity and central frequency can be observed. For the present study, WHISPER measurements of electric field spectra obtained aboard Cluster spacecraft are used to choose 48 crossings of the electron foreshock boundary with dominating Langmuir waves and to perform for the first time a statistical analysis of nonstationary behavior of quasiperpendicular zone of the Earth's bow shock. Analysis of hidden periodicities in plasma wave energy reveals shock front nonstationarity in the frequency range 0.33 f Bi

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Section: Data Selection and Analysis Proceduresmentioning

confidence: 99%

On nonstationarity and rippling of the quasiperpendicular zone of the Earth bow shock: Cluster observations

et al. 2008

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“…The resulting time series was then frequency analyzed by means of the successive least-squares power spectrum technique for multiperiodic signals (Vaniĉek 1971;Antonello et al 1986). Due to the limited resolution of our data, at each iteration of our frequency analysis we replaced the frequencies of the deteced modes with the corresponding more accurate photometric values by Breger et al (1998).…”

Section: Radial Velocitiesmentioning

confidence: 99%

Line profile variations in the δ Scuti star FG Virginis: A high number of axisymmetric modes

Mantegazza

Poretti

2002

A&A

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Abstract. Five consecutive nights of high resolution spectroscopic observations of the δ Scuti star FG Vir allowed us to analyze the radial velocity and line profile variations induced by non-radial multi-mode pulsations. Ten modes were detected. All of them have a photometric counterpart (Breger et al. 1998). Preliminary identifications have been performed by means of the simultaneous fit of line-profile and light variations. Most of these modes have an axisymmetric character (m = 0), one is retrograde (9.20 cd −1 , m = 1) and one is prograde with a relatively high order (21.55 cd −1 , = 3, m = −1). The more accurate results regard the dominant mode (12.72 cd −1 ) which is axisymmetric with = 1. In this case we were able to obtain reliable estimates of its physical characteristics. The analysis of our data tends to support the idea that the stellar rotation axis probably has a rather low inclination (about 15 • ): this is probably the reason for the high number of observed axisymmetric modes. Hence, since the measured v sin i is 20.7 km s −1 , we deduce that the rotation velocity should be around 80 km s −1 and the rotational period about 1.5 d.

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“…Four different methods, adapted to unequally spaced data, were used to perform the frequency analysis: Fourier, CLEAN (Roberts et al 1987), Vanicek (1971) and PDM algorithms (Stellingwerf 1978). A recurrent problem is the choice between the real frequency and its aliases.…”

Section: Frequency Analysismentioning

confidence: 99%

“…We thank Dr. G. Guerrero for the permission to use his code based on Vanicek's (1971) algorithm. We are grateful to Dr. Prof. C. Aerts and Dr. R. Garrido who helped us to improve this paper as well as to the anonymous referee.…”

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confidence: 99%

Activity in the SPB star 53 Piscium

Contel

Mathias

Chapellier

et al. 2001

A&A

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Abstract. New spectroscopic observations of the star 53 Psc are presented. A correlation technique has been used to derive the radial velocity curves with a high accuracy. Four frequencies have been detected in the radial velocity variations using four frequency analysis algorithms. Three frequencies (1.81, 1.22 and 1.57 cd −1 ) are typical SPB star frequencies, the last one being close to our detection threshold. They are associated to low amplitude velocities, of the order of 1-2 km s −1 . So we classify 53 Psc in the SPBs class in agreement with its position in the HR diagram. Line equivalent width and central depth variations are also observed. Two phenomena appear: first, a smooth variation, present in all lines with a time scale of 10 days, could be related to the stellar rotation and a magnetic field. Second, on two consecutive nights, a sudden and important increase (20%) of equivalent widths and central depths of Hδ and He i lines could be due to an outburst similar to the ones present in some Be stars. The variation in the equivalent widths is mainly due to the increase of the central depth of the quoted lines. This suggests the existence of NLTE effects due to a hot low density plasma in the upper layers of the atmosphere of 53 Psc. An additional frequency is pointed out around 0.11 cd −1 . The best interpretation is an SPB frequency shifted by rotation.

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Further development and properties of the spectral analysis by least-squares

Cited by 290 publications

References 2 publications

On nonstationarity and rippling of the quasiperpendicular zone of the Earth bow shock: Cluster observations

On nonstationarity and rippling of the quasiperpendicular zone of the Earth bow shock: Cluster observations

Line profile variations in the δ Scuti star FG Virginis: A high number of axisymmetric modes

Activity in the SPB star 53 Piscium

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