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Improving radial velocity precision with CARMENES-PLUS

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...

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Main Authors: Varas, Roberto (Author) , Calvo-Ortega, R. (Author) , Amado, P. J. (Author) , Becerril, S. (Author) , Ruh, H. (Author) , Azzaro, M. (Author) , Hernández, L. (Author) , Magán-Madinabeitia, H. (Author) , Reinhart, S. (Author) , Maroto-Fernández, D. (Author) , Helmling, J. (Author) , Huelmo, Á. L. (Author) , Benítez, D. (Author) , López, J. F. (Author) , Pineda, M. (Author) , García, J. A. (Author) , García de la Fuente, J. (Author) , Marín, J. (Author) , Hernández, F. (Author) , Aceituno, J. (Author) , Caballero, J. A. (Author) , Kaminski, Adrian (Author) , Mathar, R. J. (Author) , Quirrenbach, Andreas (Author) , Reiners, Ansgar (Author) , Ribas, Ignasi (Author) , Seifert, Walter (Author) , Zechmeister, Mathias (Author)
Format: Article (Journal)
Language:English
Published: 01 September 2025
In: Experimental astronomy
Year: 2025, Volume: 60, Issue: 2, Pages: 1-35
ISSN:1572-9508
DOI:10.1007/s10686-025-10020-0
Online Access:Resolving-System, kostenfrei, Volltext: https://doi.org/10.1007/s10686-025-10020-0
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Author Notes:R. Varas, R. Calvo-Ortega, P. J. Amado, S. Becerril, H. Ruh, M. Azzaro, L. Hernández, H. Magán-Madinabeitia, S. Reinhart, D. Maroto-Fernández, J. Helmling, Á. L. Huelmo, D. Benítez, J. F. López, M. Pineda, J. A. García, J. García de la Fuente, J. Marín, F. Hernández, J. Aceituno, J. A. Caballero, A. Kaminski, R. J. Mathar, A. Quirrenbach, A. Reiners, I. Ribas, W. Seifert, M. Zechmeister
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Summary: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 (~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_{*} <= 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.
Item Description:Gesehen am 09.04.2026
Physical Description:Online Resource
ISSN:1572-9508
DOI:10.1007/s10686-025-10020-0

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