Improving radial velocity precision with CARMENES-PLUS

Abstract Context: CARMENES is a dual-channel high-resolution spectrograph at the 3.5 m Calar Alto telescope designed to detect low-mass planets around late-type dwarfs by measuring their radial velocities (RVs). High thermal stability in both the visible (VIS) and near-infrared (NIR) channels is essential to achieve the precision required for these measurements. In particular, stabilising the NIR channel to the millikelvin level, which operates at cryogenic temperatures ( $$\sim$$ 140 K), poses significant engineering challenges. Purpose: The CARMENES-PLUS project was initiated to improve the instrument’s intrinsic RV precision. In this article, we focus on the thermal stability improvements made to the NIR channel’s cooling system. Methods: The NIR cooling system was originally conceived to operate with a discontinuous flow of cryogenic nitrogen gas. As part of CARMENES-PLUS, this was upgraded to a continuous flow configuration. Additional changes included the installation of an automatic vacuum system, a proportional control valve, and a pressure regulation system. These upgrades were designed to reduce thermal fluctuations and enhance long-term stability. Results: The implemented upgrades significantly improved the intrinsic RV precision of the NIR channel. We quantified this improvement using Fabry-Pérot calibration spectra, obtaining an intrinsic RV precision of 0.67 m s $$^{-1}$$ after the interventions, an improvement of nearly 2 m s $$^{-1}$$ . We also assessed the stability of the nightly zero points, finding a reduced scatter of 3.9 m s $$^{-1}$$ post-upgrade, compared to 6.1 m s $$^{-1}$$ before. For a sample of slowly rotating stars ( $$v \sin i_\star \le$$ 2 km s $$^{-1}$$ ), the median scatter decreased from 8.8 m s $$^{-1}$$ to 6.7 m s $$^{-1}$$ after the upgrades. Conclusions : These results demonstrate that the thermal control upgrades introduced in CARMENES-PLUS have enhanced the NIR channel’s RV performance, bringing it closer to the VIS channel’s stability and reinforcing CARMENES’s capabilities for exoplanet detection around M dwarfs.

Authors

Institutions

Publication Details

Journal
Experimental Astronomy
Published
2025-09-01
DOI
https://doi.org/10.1007/s10686-025-10020-0
Citations
1
Primary Topic
Astronomical Observations and Instrumentation
Type
article
Field-Weighted Citation Impact
1.33

Funders

Controls
|||
ALL TIME
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
article

Improving radial velocity precision with CARMENES-PLUS

H. Magán Madinabeitia, A. Reiners, R. Calvo-Ortega, S. Reinhart et al.
1 citations
Experimental Astronomy
Astronomical Observations and Instrumentation
1.33
article

Improving radial velocity precision with CARMENES-PLUS

H. Magán Madinabeitia, A. Reiners, R. Calvo-Ortega, S. Reinhart, Richard J. Mathar, H. L. Ruh, J. A. Caballero, José A. Lobato García, P. J. Amado, Manuel Pineda, J. Aceituno, J. Duato, M. Azzaro, A. Kaminski, I. Ribas, S. Becerril, F Hernández, R. Varas, D. Benítez, Luis Hernández, Á. L. Huelmo, J. Helmling, M. Zechmeister, J. García de la Fuente, W. Seifert, A. Quirrenbach, José F. López, D. Maroto-Fernández
article en
1 citations

Abstract

Abstract Context: CARMENES is a dual-channel high-resolution spectrograph at the 3.5 m Calar Alto telescope designed to detect low-mass planets around late-type dwarfs by measuring their radial velocities (RVs). High thermal stability in both the visible (VIS) and near-infrared (NIR) channels is essential to achieve the precision required for these measurements. In particular, stabilising the NIR channel to the millikelvin level, which operates at cryogenic temperatures ( $$\sim$$ 140 K), poses significant engineering challenges. Purpose: The CARMENES-PLUS project was initiated to improve the instrument’s intrinsic RV precision. In this article, we focus on the thermal stability improvements made to the NIR channel’s cooling system. Methods: The NIR cooling system was originally conceived to operate with a discontinuous flow of cryogenic nitrogen gas. As part of CARMENES-PLUS, this was upgraded to a continuous flow configuration. Additional changes included the installation of an automatic vacuum system, a proportional control valve, and a pressure regulation system. These upgrades were designed to reduce thermal fluctuations and enhance long-term stability. Results: The implemented upgrades significantly improved the intrinsic RV precision of the NIR channel. We quantified this improvement using Fabry-Pérot calibration spectra, obtaining an intrinsic RV precision of 0.67 m s $$^{-1}$$ after the interventions, an improvement of nearly 2 m s $$^{-1}$$ . We also assessed the stability of the nightly zero points, finding a reduced scatter of 3.9 m s $$^{-1}$$ post-upgrade, compared to 6.1 m s $$^{-1}$$ before. For a sample of slowly rotating stars ( $$v \sin i_\star \le$$ 2 km s $$^{-1}$$ ), the median scatter decreased from 8.8 m s $$^{-1}$$ to 6.7 m s $$^{-1}$$ after the upgrades. Conclusions : These results demonstrate that the thermal control upgrades introduced in CARMENES-PLUS have enhanced the NIR channel’s RV performance, bringing it closer to the VIS channel’s stability and reinforcing CARMENES’s capabilities for exoplanet detection around M dwarfs.

Experimental AstronomyVol. 60(2)
Universidad de Granada (ES), Heidelberg University (DE), Calar Alto Observatory (ES), Institut d'Estudis Espacials de Catalunya (ES), Max Planck Institute for Astronomy (DE), Institute of Space Sciences (ES), Centro de Astrobiología (ES), Institut de Ciència de Materials de Barcelona (ES), Instituto de Astrofísica de Andalucía (ES), University of Göttingen (DE), Junta de Andalucía (ES)
Ministerio de Ciencia, Innovación y Universidades, Deutsche Forschungsgemeinschaft, Universidad Complutense de Madrid, Ministerio de Economía y Competitividad, Max-Planck-Gesellschaft, Ministerio de Ciencia e Innovación, Klaus Tschira Stiftung, Junta de Andalucía, Instituto de Astrofísica de Andalucía, Max-Planck-Institut für Astronomie, Instituto de Astrofísica de Canarias, Consejo Superior de Investigaciones Científicas, European Regional Development Fund, Agencia Estatal de Investigación
Openalex Percentile: Top 19%
Astronomical Observations and Instrumentation
1.33
DOIOpen Access PDFOpenAlex
AI Navigator

Ask Laika to Summarize, Analyze, and Connect papers live on the map.

Summarize Papers & Methodologies

Extract key findings, datasets, and comparative methods across publications.

Benchmark Rankings & Visual Analytics

Rank top research institutions, authors, funders, topics, and journals by Field-Weighted Citation Impact (FWCI) and paper volume with instant charts.

Connect Distant Disciplines

Bridge topological clusters on the map to find hidden collaborative intersections.