arXiv · 2507.21262
Blind search for activity-sensitive lines in the near-infrared using HARPS and NIRPS observations of Proxima and Gl 581
Abstract
Stellar activity variability is one of the main obstacles to the detection of Earth-like planets using the RV method. The aim of this work is to measure the effect of activity in the spectra of M dwarfs and detect activity-sensitive lines in the NIR. We took advantage of the simultaneous observations of HARPS and the newly commissioned NIRPS spectrograph to carry out a blind search of the most activity-sensitive spectral lines in the NIR using NIRPS spectra and known activity indicators in the optical from HARPS as a reference. We analysed the spectra of Proxima (M5.5V) and Gl 581 (M3V), two M dwarfs with different activity levels and internal structures. Spectral lines were identified for both stars and their profiles were fitted using different models. We found hundreds of lines sensitive to activity for both stars; the Proxima spectra were more affected. For Proxima, 32% of the identified lines can be used to measure the rotation period of the star, while for Gl 581 the numbers drops to 1%. The fraction of lines sensitive to activity increases with increasing line depth. A list of 17 lines with rotation period detection for both stars is provided. Stellar activity is able to affect a significant number of spectral lines in the NIR, and methods should be developed to mitigate those effects at the spectral level. The line distortions detected here are expected to come mainly from the flux effect due to temperature contrasts between active regions and the quiet photosphere; however, we cannot rule out the possibility that core-emission from chromospheric activity or Zeeman splitting are also affecting some lines. The new line lists presented here can be used to improve the RV extraction and the detection of RV variability due to stellar activity signals, and to help false positive detection and the modelling of activity variability, thereby enhancing exoplanet detection in the NIR.
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João Gomes da Silva, Elisa Delgado-Mena, Nuno C. Santos, Telmo Monteiro, Pierre Larue, Alejandro Suárez Mascareño, Xavier Delfosse, Lucile Mignon, Étienne Artigau, Nicola Nari, Manuel Abreu, José L. A. Aguiar, Khaled Al Moulla, Guillaume Allain, Romain Allart, Tomy Arial, Hugues Auger, Frédérique Baron, Susana C. C. Barros, Luc Bazinet, Björn Benneke, Nicolas Blind, David Bohlender, Isabelle Boisse, Xavier Bonfils, Anne Boucher, François Bouchy, Vincent Bourrier, Sébastien Bovay, Pedro Branco, Christopher Broeg, Denis Brousseau, Vincent Bruniquel, Marta Bryan, Alexandre Cabral, Charles Cadieux, Bruno L. Canto Martins, Andres Carmona, Yann Carteret, Zalpha Challita, Bruno Chazelas, Ryan Cloutier, João Coelho, Marion Cointepas, Uriel Conod, Neil J. Cook, Ana Rita Costa Silva, Nicolas B. Cowan, Eduardo Cristo, Antoine Darveau-Bernier, Laurie Dauplaise, Roseane de Lima Gomes, José Renan De Medeiros, Jean-Baptiste Delisle, Dhvani Doshi, René Doyon, Xavier Dumusque, David Ehrenreich, Pedro Figueira, Dasaev O. Fontinele, Thierry Forveille, Yolanda G. C. Frensch, Jonathan Gagné, Frédéric Genest, Ludovic Genolet, Jonay I. González Hernández, Jennifer Glover, Félix Gracia Témich, Nolan Grieves, Nicole Gromek, Olivier Hernandez, Melissa J. Hobson, H. Jens Hoeijmakers, Norbert Hubin, Farbod Jahandar, Ray Jayawardhana, Hans-Ulrich Käufl, Dan Kerley, Johann Kolb, Vigneshwaran Krishnamurthy, Benjamin Kung, Alexandrine L'Heureux, David Lafrenière, Pierrot Lamontagne, Izan de Castro Leão, Henry Leath, Olivia Lim, Justin Lipper, Gaspare Lo Curto, Christophe Lovis, Lison Malo, Allan M. Martins, Jaymie Matthews, Jean-Sébastien Mayer, Claudio Melo, Lina Messamah, Yuri S. Messias, Stan Metchev, Leslie Moranta, Christoph Mordasini. 2025-07-28. Blind search for activity-sensitive lines in the near-infrared using HARPS and NIRPS observations of Proxima and Gl 581. https://arxiv.org/abs/2507.21262
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