Abréviations

Walraven, Klaas van

doi:10.4000/books.pur.42986

Cited by 2 publications

(3 citation statements)

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“…As an example, the upper panel of Fig. 1 shows the B -band light curve of the old nova V603 Aql observed in the Walraven photometric system on 1983, July 18 (see Walraven &Walraven, 1960, andPel, 1977, for the peculiarities of the Walraven system). In addition to flickering, it shows another feature frequently observed in CVs, that is, variations on longer time scales that may not be immediately associated with flickering (at least not in the light curve discussed here; see Bruch 1991).…”

Section: Reduction Methodsmentioning

confidence: 99%

“…V BLUW (Walraven) light curves: They were obtained by various observers at the Dutch telescope at ESO/La Silla, equipped with the Walraven photometer (Walraven & Walraven, 1960). The instrument permits only a limited choice of configurations, resulting in a time resolution of about 21 s of the present data, which may be at the limit of usefulness for the current purpose.…”

Section: Datamentioning

confidence: 99%

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Time lags of the flickering in cataclysmic variables as a function of wavelength

Bruch

2015

A&A

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Context. Flickering is a ubiquitous phenomenon in cataclysmic variables (CVs). Although the underlying light source is one of the main contributors to the optical radiation, the mechanism leading to flickering is not understood as yet. Aims. The present study aims to contribute to the set of boundary conditions, defined by observations, which must be met by physical models that describe the flickering. In particular, time lags in the occurrence of flickering events at different wavelengths over the optical range are examined. Methods. To this end, the cross-correlation functions (CCFs) of numerous light curves of a sample of CVs are analysed that were observed simultaneously or quasi-simultaneously in different bands of various photometric systems. Results. Deviations of the maxima of the CCFs from zero time-shift indicate a dependence of the flickering activity on the wavelength in the sense that flickering flares reach their maxima slightly earlier in the blue range than in the red. While the available observational material does not permit detecting this individually in all observed systems, the ensemble of all data clearly shows this effect. Particularly instructive are the cases of V603 Aql and TT Ari, where time lags of 15. s 1 and 4. s 3, respectively, are observed between the U and R bands. In principle this can be understood if during the development of a flickering flare the radiation characteristics of the light source responsible for flickering change such that in the early phases of a flare more short-wavelength radiation is emitted, and later on, the peak of the emission shifts to the red. Respective scenarios are discussed and shown to be in qualitative and quantitative agreement with observations.

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Section: Reduction Methodsmentioning

confidence: 99%

Section: Datamentioning

confidence: 99%

Time lags of the flickering in cataclysmic variables as a function of wavelength

Bruch

2015

A&A

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“…Moreover, the light curve folded on the adopted period sup-ports the presence of consistent variations on this period. Its amplitude, listed in Table 3 refers to the B band and was transformed from flux units as provided by the Walraven photometer (Walraven & Walraven 1960;Rijf, Tinbergen & Walraven 1969) into magnitudes. 1990: Six light curves observed in the Stiening system, kindly provided by E. Robinson are available.…”

Section: Smaller Data Sets Observed Between 1977 and 2004mentioning

confidence: 99%

TT Arietis: 40 yr of photometry

Bruch

2019

Monthly Notices of the Royal Astronomical Society

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In an effort to characterize variations on the time scale of hours and smaller during the high and low states of the novalike variable TT Ari, light curves taken over the course of more than 40 yr are analyzed. It is found that the well known negative superhump observed during the high state persists until the present day at an average period of 0.13295 d which is slightly variable from year to year and exhibits substantial amplitude changes. The beat period between superhump and orbital period is also seen. QPOs occur at a preferred quasi-period of 18 -25 min and undergo a systematic frequency evolution during a night. The available data permit for the first time a detailed investigation of the low state which is highly structured on time-scales of tens of days. On hourly time scales the light curve exhibits strong variations which are mostly irregular. However, during an interval of several days at the start of the low state, coherent 1.2 mag oscillations with a period of 8.90 h are seen. During the deep low state quiet phases and strong (1.5 -3 mag), highly structured flares alternate in irregular intervals of roughly 1 day. The quiet phases are modulated on the orbital period of TT Ari, suggesting reflection of the light of the primary component off the secondary. This is the first time that the orbital period is seen in photometric data.

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Abréviations

Cited by 2 publications

References 0 publications

Time lags of the flickering in cataclysmic variables as a function of wavelength

Time lags of the flickering in cataclysmic variables as a function of wavelength

TT Arietis: 40 yr of photometry

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