Abstract

The analysis of 14 periodograms of EZ Lyn for data spaced over 565 d in 2012–2014 (2–3.5 yr after the 2010 outburst) yielded the existence of a stable signal around 100 cycles/day (c/d) and three signals around 310 c/d, 338 c/d, and 368 c/d (the corresponding periods are 864 s, 279 s, 256 s, and 235 s). We interpret them as independent nonradial pulsations of the white dwarf in EZ Lyn, but the possibility that a linear combination of a frequency of 100 c/d and a harmonic of the orbital period might produce a frequency of 368 c/d also cannot be excluded. The signal at 100 c/d was detected as a transient during the first stay in the instability strip. The period at 338 c/d has been a known nonradial pulsation since EZ Lyn entered the instability strip after the 2010 outburst. We detected the signals around 310 c/d and 368 c/d for the first time. We applied the two-dimensional least absolute shrinkage and selection operator (Lasso) analysis for the first time to explore the behavior of these signals on a time scale of hours in nightly runs of observations having a duration of 6–12 hr. The Lasso analysis revealed the simultaneous existence of all three frequencies (310 c/d, 338 c/d, and 368 c/d) on a majority of nights of observations, but with variable amplitudes and variable drifts of frequencies by 2%–6% on a time scale of ∼ 5–7 hr. The largest drift we detected corresponded to 17.5 s in period in ∼ 5 hr.

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