Diving into the planetary system of Proxima with NIRPS

Breaking the metre per second barrier in the infrared^★

¹ Instituto de Astrofísica de Canarias (IAC), Calle Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain
² Departamento de Astrofísica, Universidad de La Laguna (ULL), 38206 La Laguna, Tenerife, Spain
³ Institut Trottier de recherche sur les exoplanètes, Département de Physique, Université de Montréal, Montréal, Québec, Canada
⁴ Observatoire du Mont-Mégantic, Québec, Canada
⁵ Observatoire de Genève, Département d’Astronomie, Université de Genève, Chemin Pegasi 51, 1290 Versoix, Switzerland
⁶ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
⁷ Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, Campus Universitário, Natal, RN 59072-970, Brazil
⁸ Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, 4150-762 Porto, Portugal
⁹ Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal
¹⁰ Department of Physics, University of Toronto, Toronto, ON M5S 3H4, Canada
¹¹ Department of Physics & Astronomy, McMaster University, 1280 Main St W, Hamilton, ON L8S 4L8, Canada
¹² Department of Physics, McGill University, 3600 rue University, Montréal, QC H3A 2T8, Canada
¹³ Department of Earth & Planetary Sciences, McGill University, 3450 rue University, Montréal, QC H3A 0E8, Canada
¹⁴ Departamento de Física, Universidade Federal do Ceará, Caixa Postal 6030, Campus do Pici, Fortaleza, Brazil
¹⁵ Centro de Astrobiología (CAB), CSIC-INTA, ESAC campus, Camino Bajo del Castillo s/n, 28692, Villanueva de la Cañada (Madrid), Spain
¹⁶ Centre Vie dans l’Univers, Faculté des sciences de l’Université de Genève, Quai Ernest-Ansermet 30, 1205 Geneva, Switzerland
¹⁷ European Southern Observatory (ESO), Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
¹⁸ Space Research and Planetary Sciences, Physics Institute, University of Bern, Gesellschaftsstrasse 6, 3012 Bern, Switzerland
¹⁹ Consejo Superior de Investigaciones Científicas (CSIC), 28006 Madrid, Spain
²⁰ Bishop’s Univeristy, Dept of Physics and Astronomy, Johnson-104E, 2600 College Street, Sherbrooke, QC J1M 1Z7, Canada
²¹ Department of Physics and Space Science, Royal Military College of Canada, PO Box 17000, Station Forces, Kingston, ON, Canada
²² Instituto de Astrofísica e Ciências do Espaço, Faculdade de Ciên-cias da Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal
²³ Departamento de Física da Faculdade de Ciências da Universidade de Lisboa, Edifício C8, 1749-016 Lisboa, Portugal
²⁴ Centre of Optics, Photonics and Lasers, Université Laval, Québec, Canada
²⁵ Herzberg Astronomy and Astrophysics Research Centre, National Research Council of Canada, Canada
²⁶ Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France
²⁷ Center for Space and Habitability, University of Bern, Gesellschaftsstrasse 6, 3012 Bern, Switzerland
²⁸ European Southern Observatory (ESO), Av. Alonso de Cordova 3107, Casilla 19001, Santiago de Chile, Chile
²⁹ Planétarium de Montréal, Espace pour la Vie, 4801 av. Pierre-de Coubertin, Montréal, Québec, Canada
³⁰ Lund Observatory, Division of Astrophysics, Department of Physics, Lund University, Box 118, 221 00 Lund, Sweden
³¹ York University, 4700 Keele St, North York, ON M3J 1P3, Canada
³² University of British Columbia, 2329 West Mall, Vancouver, BC V6T 1Z4, Canada
³³ Western University, Department of Physics & Astronomy and Institute for Earth and Space Exploration, 1151 Richmond Street, London, ON N6A 3K7, Canada
³⁴ Light Bridges S.L., Observatorio del Teide, Carretera del Observatorio, s/n Guimar, 38500 Tenerife, Canarias, Spain
³⁵ University Observatory, Faculty of Physics, Ludwig-Maximilians-Universität München, Scheinerstr. 1, 81679 Munich, Germany
³⁶ Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany
³⁷ Subaru Telescope, National Astronomical Observatory of Japan (NAOJ), 650 N Aohoku Place, Hilo, HI 96720, USA
³⁸ Department of Astronomy & Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA
³⁹ Laboratoire Lagrange, Observatoire de la Côte d’Azur, CNRS, Université Côte d’Azur, Nice, France

^★★ Corresponding author: asm@iac.es

Received: 11 January 2025
Accepted: 19 March 2025

Abstract

We obtained 420 high-resolution spectra of Proxima, over 159 nights, using the Near Infra Red Planet Searcher (NIRPS). We derived 149 nightly binned radial velocity measurements with a standard deviation of 1.69 ms⁻¹ and a median uncertainty of 55 cms⁻¹, and performed a joint analysis combining radial velocities, spectroscopic activity indicators, and ground-based photometry, to model the planetary and stellar signals present in the data, applying multi-dimensional Gaussian process regression to model the activity signals. We detect the radial velocity signal of Proxima b in the NIRPS data. All planetary characteristics are consistent with those previously derived using visible light spectrographs. In addition, we find evidence of the presence of the sub-Earth Proxima d in the NIRPS data. When combining the data with the HARPS observations taken simultaneous to NIRPS, we obtain a tentative detection of Proxima d and parameters consistent with those measured with ESPRESSO. By combining the NIRPS data with simultaneously obtained HARPS observations and archival data, we confirm the existence of Proxima d, and demonstrate that its parameters are stable over time and against change of instrument. We refine the planetary parameters of Proxima b and d, and find inconclusive evidence of the signal attributed to Proxima c (P = 1900 d) being present in the data. We measure Proxima b and d to have minimum masses of 1.055 ± 0.055 M_⊕, and 0.260 ± 0.038 M_⊕, respectively. Our results show that, in the case of Proxima, NIRPS provides more precise radial velocity data than HARPS, and a more significant detection of the planetary signals. The standard deviation of the residuals of NIRPS after the fit is ~80 cm s⁻¹, showcasing the potential of NIRPS to measure precise radial velocities in the near-infrared.