Multicolour photometry of EO Ceti (PB 8783)

Abstract

We present the first-look analysis of the high-speed multicolour photometry of the bright V361 Hya-type star EO Ceti (m V=12.3). The observations were gathered with the three-channel ULTRACAM instrument attached to the 4.2-m William Herschel Telescope. The data set has a total time span of 6.2 d and consists of 31 h simultaneous three colour photometry. The main power regions in all three colours are the same as previously reported in the white light photometric campaigns on EO Ceti. We calculate the frequencies, amplitudes and phases of the significant modes in three colours of the SDSS system, r′, g′ and u′. The amplitudes of the detected modes are the highest in the u′ lightcurve, and the phases are the same in all three colours within the measurement accuracy. The amplitudes of the highest signal-to-noise modes show time variability in all three colours. We analyse the amplitude and phase variations of the five highest signal-to-noise modes in different colours. Even though the amplitudes show variations from night to night, the amplitude ratios are found to be constant to within 2σ level. This result is promising as it allows us to compare the observed amplitude ratios with theoretically calculated amplitude ratios. This may further constrain the mode identification of the highest amplitude modes in EO Ceti and let us test the proposed seismic and binary evolution models.