Least-squares Spectral and Wavelet Analyses of V455 Andromedae Time Series: The Life After the Super-outburst

Abstract

An extensive spectral analysis is performed on the light curve of dwarf nova V455 Andromedae (V455 And = HS 2331+3905) using the Least-squares WAVElet software (LSWAVE) to highlight its robustness for analyzing astronomical time series. The V455 And properties are briefly reviewed, and the recent results are compared with the results obtained herein. It is shown that the new analytical tools are superior to the traditional ones in that they consider observational uncertainties, do not require any interpolation and/or gap-filling, and can estimate the spectral peaks at a higher time–frequency resolution. First, the Anti-leakage Least-squares Spectral Analysis (ALLSSA) is applied to analyze a V455 And unequally spaced time series since 2008. ALLSSA has estimated spectral peaks at 80.40, 40.54, 1.12, and 0.56 minutes that correspond to the orbital period, its first harmonic, the white dwarf spin period, and its harmonic, respectively, confirming the earlier results. ALLSSA is then applied to all sufficiently large-size segments of the light curve to estimate the periodic components and demonstrate the double-humped orbital variations. Next, the Least-squares Wavelet Analysis (LSWA) is applied to four light curve segments each with a sufficient number of observations to study the periodic and aperiodic components. LSWA also detects the spectral peaks corresponding to the orbital period and non-radial white dwarf pulsations at a period of 4–5 minutes in 2010 October which gradually shifts toward 5–6 minutes in 2015 and 2018.