Henriette Schwarz

The video is an example of a cross-correlation function between a noisy observed spectrum of a directly imaged sub-stellar companion and a model CO spectrum.

The substellar companion is HIP 78530 b and was observed with CRIRES. The spectrum has a SNR = 2 and shown here is only a single detector. At the end of the video we show the final cross-correlation function from a weighted average of three detectors.   

Although the CO lines are almost invisible in the noisy observed spectrum, the cross-correlation picks out the signal when it matches the correct radial velocity of the substellar companion (the systemic velocity). The shape of the cross-correlation signal is closely related to the the line profile of the CO lines in the observed companion spectrum.