Discovery of Fourier-dependent time lags in cataclysmic variables

S. Scaringi, E. Koerding, P. J. Groot, P. Uttley, T. Marsh, C. Knigge, Thomas Maccarone, V. S. Dhillon

Research output: Contribution to journalArticlepeer-review


We report the first study of Fourier-frequency-dependent coherence and phase/time lags at optical wavelengths of cataclysmic variables (MV Lyr and LU Cam) displaying typical flickering variability in white light. Observations were performed on the William Herschel Telescope using ULTRACAM. Light curves for both systems have been obtained with the SDSS filters u', g' and r' simultaneously with cadences in the range ≈0.5-2 s, and allow us to probe temporal frequencies between ≈10-3 and ≈1 Hz. We find high levels of coherence between the u', g' and r' light curves up to at least ≈10-2 Hz. Furthermore, we detect red/negative lags where the redder bands lag the bluer ones at the lowest observed frequencies. For MV Lyr time lags up to ≈3 s are observed, whilst LU Cam displays larger time lags of ≈10 s. Mechanisms which seek to explain red/negative lags observed in X-ray binaries and active galactic nuclei involve reflection of photons generated close to the compact object on to the surface
Original languageEnglish
Pages (from-to)2535
JournalMonthly Notices of the Royal Astronomical Society
StatePublished - May 2013


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