J/A+A/705/A190 55 Cnc A and 55 Cnc B Spirou RV and Bl (Moutou+, 2026)
Characterizing planetary systems with SPIRou: Questions about the magnetic
cycle of 55 Cnc A and two new planets around B.
Moutou C., Petit P., Charpentier P., Cristofari P., Baruteau C.,
Thebault P., Arnold L., Artigau E., Carmona A., Cook N.J., Debras F.,
Delfosse X., Donati J.-F., Malo L., Ould-Elhkim M.
<Astron. Astrophys. 705, A190 (2026)>
=2026A&A...705A.190M 2026A&A...705A.190M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Optical ;
Radial velocities ; Magnetic fields
Keywords: planets and satellites: detection - stars: low-mass -
stars: magnetic field - star: individual: 55 Cnc A and B
Abstract:
One of the first exoplanet hosts, discovered about thirty years ago,
the star 55 Cnc has been continuously observed ever since. It is now
known to host at least five planets with orbital periods ranging from
17 hours to 15 years. It is also one of the most extreme metal-rich
stars in the neighbourhood, and it has a low-mass secondary star. In
this article, we present data obtained at the Canada-France-Hawaii
Telescope with the SPIRou spectropolarimeter on both components of the
55 Cnc stellar system. We revisit the long-period radial-velocity
signals of 55 Cnc A, with a focus on the role of the magnetic cycle,
and propose the existence of a sixth planet candidate, whose period
falls close to that of the magnetic cycle, or half of it. The other
massive outer planet has a revised period of 13.15 years and a minimum
mass of 3.8MJup. Although some uncertainty remains about these outer
planets, the characterisation of the four inner planets is very robust
through the combination of many different datasets, and all signals
are consistent in the near-infrared (nIR) and optical domains. In
addition, the magnetic topology of the solar-type primary component of
the system was observed by SPIRou at the minimum of its activity
cycle, characterised by an amplitude ten times smaller than observed
that during its maximum in 2017. For the low-mass component 55 Cnc B,
we report the discovery of two exoplanets in the system, with a period
of 6.799±0.0014 and 33.75±0.04 days and a minimum mass of
3.5±0.8 and 5.3±1.4M⊕, respectively. The secondary
magnetic field is very weak, and the current dataset does not allow
its precise characterisation, setting an upper limit of 10 G. The
system 55 Cnc stands out as the sixth binary system with planetary
systems around both components and the first one with non-equal-mass
stellar components.
Description:
This study describe SPIRou data on the A and B star of the stellar
system 55 Cnc, looking at both the radial velocity content and the
spectropolarimetric parameters.
The new data used in this study is compiled here: SPIRou data of 55
Cnc A (Table A1) and 55 Cnc B (Table A2), and archival
spectropolarimetric optical data of 55 Cnc A (Table A3).
Objects:
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RA (2000) DE Designation(s)
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08 52 35.81 +28 19 50.9 55 Cnc A = * 55 Cnc A
08 52 40.86 +28 18 58.8 55 Cnc B = * 55 Cnc B
--------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 48 141 SPIRou data of 55 Cnc A
tablea2.dat 48 69 SPIRou data of 55 Cnc B
tablea3.dat 36 62 Archival spectropolarimetric optical data of 55 Cnc
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See also:
J/A+A/533/A114 : Transit of super-Earth 55 Cnc e (Demory+, 2011)
J/ApJ/778/132 : C and O abundances in 55 Cnc (Teske+, 2013)
J/A+A/539/A28 : New transit photometry for super-Earth 55 Cnc e (Gillon+, 2012
J/A+A/545/A97 : 0.8-6µm calibrated spectrum of 55 Cnc (Crossfield, 2012)
J/ApJ/792/L31 : HARPS & HARPS-N 55 Cnc radial velocities (Lopez-Morales+ 2014)
J/A+A/615/A117 : 55 Cnc geocoronal emission lines template (Bourrier+, 2018)
J/A+A/619/A1 : 55 Cnc radial velocities and photometry (Bourrier+, 2018)
J/A+A/653/A173 : CHEOPS 55 Cnc light curve (Morris+, 2021)
J/A+A/677/A112 : CHEOPS observations of 55 Cnc e (Meier Valdes+, 2023)
J/A+A/690/A159 : 55 Cnc e JWST light curves and spectra (Patel+, 2024)
Byte-by-byte Description of file: tablea1.dat tablea2.dat
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Bytes Format Units Label Explanations
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1- 12 F12.6 d BJD Barycentric Julian Day (BJD-2400000)
16- 23 F8.2 m/s RV Radial velocity
30- 34 F5.2 m/s e_RV Radial velocity error
38- 41 F4.1 gauss Bl ?=- Longitudinal magnetic field
46- 48 F3.1 gauss e_Bl ?=- Longitudinal magnetic field error
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Byte-by-byte Description of file: tablea3.dat
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Bytes Format Units Label Explanations
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1- 12 F12.6 d BJD Barycentric Julian Day (BJD-2400000)
20- 24 F5.2 gauss Bl Longitudinal magnetic field
33- 36 F4.2 gauss e_Bl Longitudinal magnetic field
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Acknowledgements:
Claire Moutou, claire.moutou(at)irap.omp.eu
(End) Patricia Vannier [CDS] 13-Oct-2025