• DOI:10.1051/0004-6361/202037745
• Corpus ID: 218869742

Revisiting Proxima with ESPRESSO

@article{SurezMascareo2020RevisitingPW,
  title={Revisiting Proxima with ESPRESSO},
  author={A. Su{\'a}rez Mascare{\~n}o and J. P. Faria and Pedro Figueira and Christophe Lovis and Mario Damasso and Jonay I. Gonz{\'a}lez Hern{\'a}ndez and Rafael Rebolo and Stefano Cristiani and Francesco Pepe and N. C. Santos and Mar{\'i}a Rosa Zapatero Osorio and Vardan Adibekyan and S. Hojjatpanah and Alessandro Sozzetti and Felipe Murgas and Margarida Abreu and Matthew Affolter and Yann Alibert and Matteo Aliverti and Romain Allart and Carlos Allende Prieto and David Castro Alves and Manuel Amate and G. Avila and Veronica Baldini and Tobias Bandi and Susana C. C. Barros and A. Bianco and W. Benz and Fr{\'e}d{\'e}ric Bouchy and C. Broeng and A. Cabral and Giorgio Calderone and Roberto Cirami and Jo{\~a}o M. P. Coelho and Paolo Conconi and Igor Coretti and Claudio Cumani and Guido Cupani and Valentina D’Odorico and Sebastian Deiries and Bernhard Delabre and Paolo Di Marcantonio and Xavier Dumusque and David Ehrenreich and A. B. Fragoso and Ludovic Genolet and Matteo Genoni and Ricardo G{\'e}nova Santos and Ian Hughes and Olaf Iwert and Florian Kerber and J. Knusdstrup and Marco Landoni and Baptiste Lavie and Jorge Lillo-Box and Jean Louis Lizon and G. Lo Curto and Charles Maire and Antonio Manescau and Carlos J. A. P. Martins and D. Megevand and A. Mehner and Giusi Micela and Andr{\'e}a Modigliani and Paolo Molaro and Manuel Monteiro and Mario Monteiro and Manuele Moschetti and Eric Mueller and Nelson J. Nunes and Luca Oggioni and A. Oliveira and Enric Pall{\'e} and Gina M. Pariani and Luca Pasquini and Ennio Poretti and Jos{\'e} Luis Rasilla and Edoardo Maria Alberto Redaelli and M. Riva and Samuel Santana Tschudi and Paolo Santin and P. Santos and Alex Segovia and Danuta Sosnowska and S{\'e}rgio G. Sousa and P. Span{\'o} and Fabio Tenegi and Susan M Udry and Antonio Zanutta and F. Zerbi},
  journal={Astronomy \& Astrophysics},
  year={2020}
}

• A. Suárez Mascareño, J. Faria, +88 authors F. Zerbi
• Published 25 May 2020
• Physics, Geology
• Astronomy & Astrophysics

Context.The discovery of Proxima b marked one of the most important milestones in exoplanetary science in recent years. Yet the limited precision of the available radial velocity data and the difficulty in modelling the stellar activity calls for a confirmation of the Earth-mass planet.Aims.We aim to confirm the presence of Proxima b using independent measurements obtained with the new ESPRESSO spectrograph, and refine the planetary parameters taking advantage of its improved precision.Methods.We analysed 63 spectroscopic ESPRESSO observations of Proxima (Gl 551) taken during 2019. We obtained radial velocity measurements with a typical radial velocity photon noise of 26 cm s−1. We combined these data with archival spectroscopic observations and newly obtained photometric measurements to model the stellar activity signals and disentangle them from planetary signals in the radial velocity (RV) data. We ran a joint Markov chain Monte Carlo analysis on the time series of the RV and full width half maximum of the cross-correlation function to model the planetary and stellar signals present in the data, applying Gaussian process regression to deal with the stellar activity signals.Results.We confirm the presence of Proxima b independently in the ESPRESSO data and in the combined ESPRESSO+ HARPS+UVES dataset. The ESPRESSO data on its own shows Proxima b at a period of 11.218 ± 0.029 days, with a minimum mass of 1.29 ± 0.13M⊕. In the combined dataset we measure a period of 11.18427 ± 0.00070 days with a minimum mass of 1.173 ± 0.086M⊕. We get a clear measurement of the stellar rotation period (87 ± 12 d) and its induced RV signal, but no evidence of stellar activity as a potential cause for the 11.2 days signal. We find some evidence for the presence of a second short-period signal, at 5.15 days with a semi-amplitude of only 40 cm s−1. If caused by a planetary companion, it would correspond to a minimum mass of 0.29 ± 0.08M⊕. We find that forthe case of Proxima, the full width half maximum of the cross-correlation function can be used as a proxy for the brightness changes and that its gradient with time can be used to successfully detrend the RV data from part of the influence of stellar activity. The activity-induced RV signal in the ESPRESSO data shows a trend in amplitude towards redder wavelengths. Velocities measured using the red end of the spectrograph are less affected by activity, suggesting that the stellar activity is spot dominated. This could be used to create differential RVs that are activity dominated and can be used to disentangle activity-induced and planetary-induced signals. The data collected excludes the presence of extra companions with masses above 0.6M⊕at periods shorter than 50 days.