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A photometric and spectroscopic study of the hottest pulsating extreme helium star, V2076 Oph (HD 160641)
We present results from a three-site photometric and high-resolutionspectroscopic campaign on the hottest known extreme helium star V2076Oph (HD 160641). A core programme of intensive observations covered twoweeks and a much lower sampling rate extended over another two months.Despite the fact that the data seem to indicate periodicity near half aday (though the light curves are clearly not formed by a singleperiodicity), conventional Fourier analysis of the data fails to revealcoherent frequencies. Furthermore, we are unable to recover frequencieswhich were apparently clear in an earlier campaign on the star. Evidenceof monotonic pulsation amplitude changes is seen at the higherfrequencies from a wavelet analysis, but more data are needed beforethis study can be extended to lower frequencies. The application oflinear stochastic differential equation (LSDE) methods indicates thatthe observed light variations could be a result of random variationsgiving the appearance of intermittent periodicity. High-resolutionspectroscopic observations were obtained during the campaign andadditional observations were made three years later. Complex lineprofile variations were observed. It is proposed that the differentbehaviour of the emission line studied may indicate it is associatedwith a stellar wind or resident circumstellar material. The frequenciesthat are extracted from the velocity data do not conform to thoseidentified in the current or previous photometric campaigns.
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