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Ongoing projects and examples

With a high-resolution spectrograph (resolution up to 120.000), it is possible to measure more than just precise radial velocities. A number of small projects are ongoing that are using this instrument for other purpose: measuring line-bisectors and performing spectroscopy of eclipsing binaries during eclipses so that the spectra of the individual stars can be disentangled. The main projects involve performing asteroseismology of bright stars, as illustrated by the adjoining figure, which depicts the observed radial-velocity curve during one for γ Cephei for which the oscillations are clearly visible. 

Figure: The oscillations of  γ Cephei observed in September 2014 with SONG. A measurement precision of  ~1.5m/s per point is obtained for 120s integrations on this V=3.22 star.

By observing targets for many nights, we can obtain the oscillation power-spectrum as illustrated for γ Cephei below. The power-spectrum is based on 2200 spectra obtained during a 2-week period in September 2014.  The effect of the 1-day aliasing is clearly seen, which arises from having gaps in the observations during the daytime. Such observations would benefit from having the entire network; continuous observations woul  greatly reduce the amplitude of the sidebands in the spectral window function thus providing much cleaner oscillation spectra.


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