Understanding stellar activity-induced radial velocity jitter using simultaneous K2 photometry and HARPS RV measurements
arXiv:1707.01827 · doi:10.1051/0004-6361/201731139
Abstract
One of the best ways to improve our understanding of the stellar activity-induced signal in radial velocity (RV) measurements is through simultaneous high-precision photometric and RV observations. This is of prime importance to mitigate the RV signal induced by stellar activity and therefore unveil the presence of low-mass exoplanets. The K2 Campaign 7 and 8 field-of-views were located in the southern hemisphere, and provided a unique opportunity to gather unprecedented simultaneous high precision photometric observation with K2 and high-precision RV measurements with the HARPS spectrograph to study the relationship between photometric variability and RV jitter. We observed nine stars with different levels of activity; from quiet to very active. We probe the presence of any meaningful relation between measured RV jitter and the simultaneous photometric variation, and also other activity indicators (e.g. BIS, FWHM, , and F8), by evaluating the strength and significance of the correlation between RVs and each indicator. We found that for the case of very active stars, strong and significant correlations exist between almost all the observables and measured RVs; however, for lower activity levels the correlations become random. Except for the F8 which its strong correlation with RV jitter persists over a wide range of stellar activity level, and thus our result suggests that F8 might be a powerful proxy for activity induced RV jitter. Moreover, we examine the capability of two state-of-the-art modeling techniques, namely the FF' method and SOAP2.0, in accurately predicting the RV jitter amplitude using the simultaneous photometric observation. We found that for the very active stars both techniques can reasonably well predict the amplitude of the RV jitter, however, at lower activity levels the FF' method underpredicts the RV jitter amplitude.
13 pages, 7 figures, 2 tables, accepted for publication in A&A
References in corpus (11)
- The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
- The K2 Mission: Characterization and Early results
- A new list of thorium and argon spectral lines in the visible
- Stellar Activity Masquerading as Planets in the Habitable Zone of the M dwarf Gliese 581
- SOAP 2.0: A tool to estimate the photometric and radial velocity variations induced by stellar spots and plages
- TW Hydrae: evidence of stellar spots instead of a Hot Jupiter
- Stellar activity of planetary host star HD 189733
- Impact of occultations of stellar active regions on transmission spectra: Can occultation of a plage mimic the signature of a blue sky?
- The HARPS search for southern extra-solar planets XXXV. The interesting case of HD41248: stellar activity, no planets?
- New planetary and EB candidates from Campaigns 1-6 of the K2 mission
- Revisiting the transits of CoRoT-7b at a lower activity level