| Time-series spectroscopy of the rapidly oscillating Ap star HR 3831 (2007) | |||||||||||||
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| We present time-series spectroscopy of the rapidly oscillating Ap star HR 3831. This star has a dominant pulsation period of 11.7 minutes and a rotation period of 2.85 d. We have analysed 1400 intermediate-resolution spectra of the wavelength region 6100-- 7100 A obtained over one week, using techniques similar to those we applied to another roAp star, ff Cir. We confirm that the Hff velocity amplitude of HR 3831 is modulated with rotation phase. Such a modulation was predicted by the oblique pulsator model, and rules out the spotted pulsator model. However, further analysis of Hff and other lines reveal rotational modulations that cannot easily be explained using the oblique pulsator model. In particular, the phase of the pulsation as measured by the width of the Hff line varies with height in the line. The variation of the Hff bisector shows a very similar pattern to that observed in ff Cir, which we have previously attributed to a radial node in the stellar atmosphere. However, th... | |||||||||||||
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