Spectroscopic transit search: a self-calibrating method for detecting planets around bright stars

Aims: We aim to search for transiting exoplanets around the starβ Pictoris using high-resolution spectroscopy and Doppler imagingthat removes the need for standard star observations. These data wereobtained on the VLT with UVES during the course of an observing campaignthroughout 2017 that monitored the Hill sphere transit of the exoplanetβ Pictoris b. Methods: We utilized line profile tomographyas a method for the discovery of transiting exoplanets. By measuring theexoplanet distortion of the stellar line profile, we removed the needfor reference star measurements. We demonstrated the method with whitenoise simulations, and then looked at the case of β Pictoris, whichis a δ Scuti pulsator. We describe a method to remove the stellarpulsations and perform a search for any transiting exoplanets in theresultant data set. We injected fake planet transits with varyingorbital periods and planet radii into the spectra and determined therecovery fraction. Results: In the photon noise limited case wecan recover planets down to a Neptune radius with an 80% success rate,using an 8 m telescope with a R 100 000 spectrograph and 20 min ofobservations per night. The pulsations of β Pictoris limit oursensitivity to Jupiter-sized planets, but a pulsation removal algorithmimproves this limit to Saturn-sized planets. We present two planetcandidates, but argue that their signals are most likely caused by otherphenomena. Conclusions: We have demonstrated a method forsearching for transiting exoplanets that (i) does not require ancillarycalibration observations, (ii) can work on any star whose rotationalbroadening can be resolved with a high spectral dispersion spectrograph,and (iii) provides the lowest limits so far on the radii of transitingJupiter-sized exoplanets around β Pictoris with orbital periodsfrom 15 days to 200 days with >50% coverage.