Disentangling planetary and stellar activity signals in M-dwarf RVs through template matching

The analysis of radial velocity periodograms has proven a fruitful technique for the detection of exoplanets. However, not every strong signal in a periodogram is necessarily of planetary origin; stellar activity can create quasi-periodic signals which may mimic a true planet. This is particularly the case for M-dwarfs, which tend to show higher levels of activity than more massive stars. Therefore, it is important to be able to distinguish between these signals.

While a true planetary signal will affect the whole stellar spectrum equally, the effect of stellar activity, e.g. spots and plages, will be stronger in specific regions (dependent on the temperature contrast). This can be exploited to distinguish between signals, by the use of different RV extraction techniques which weight the spectral regions differently. In this contribution, we apply both CCF and template-matching to a sample of M-dwarfs spectra obtained with the SOPHIE spectrograph, and analyse the resulting datasets. We examine how suspected activity signals vary according to the technique applied, and where possible confirm their provenance using activity indicators such as the calcium RhK  and H-alpha indices. This approach will also be tested on SPIRou data in the near future.

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