J/MNRAS/545/F1934 HARPS-N and CHEOPS data of HD 85426 (Lienhard+, 2026)
HARPS-N, TESS, and CHEOPS discover a transiting sub-Neptune and two outer
companions around the bright solar analogue HD 85426.
Lienhard F., Mortier A., Collier Cameron A., Cretignier M., Borsato L.,
Anna John A., Egger J.A., Stalport M., Wilson T.G., Deline A., Fortier A.,
Latham D.W., Malavolta L., Maxted P.F.L., Sousa S.G., Grimm S.L.,
Buchhave L., Alibert Y., Lakeland B.S., Dumusque X., Cabrera J.,
Naponiello L., Correia A.C.M., Rescigno F., Fossati L., Sozzetti A.,
Alonso R., Barczy T., Barrado D., Barros S.C.C., Baumjohann W., Benz W.,
Billot N., Brandeker A., Broeg C., Collins K., Csizmadia Sz., Cubillos P.E.,
Davies M.B., Deleuil M., Demangeon O.D.S., Demory B.-O., Derekas A.,
Edwards B., Ehrenreich D., Erikson A., Fridlund M., Gandolfi D.,
Gazeas K., Gillon M., Guedel M., Guenther M.N., Haywood R., Heitzmann A.,
Helling C., Isaak K.G., Jenkins J.M., Kiss L.L., Korth J., Lam K.W.F.,
Laskar J., Lecavelier des Etangs A., Leleu A., Lendl M., Magrin D.,
Martinez Fiorenzano A.F., Merin B., Mordasini C., Nascimbeni V.,
Olofsson G., Osborn H.P., Ottensamer R., Pagano I., Palethorpe L.,
Palle E., Peter G., Piazza D., Piotto G., Pollacco D., Queloz D.,
Ragazzoni R., Rando N., Rauer H., Ribas I., Rice K., Santos N.C.,
Scandariato G., Segransan D., Simon A.E., Smith A.M.S., Sulis S.,
Szabo Gy.M., Udry S., Ulmer-Moll S., Van Grootel V., Venturini J.,
Villaver E., Walton N.A., Zingales T.
<Mon. Not. R. Astron. Soc. 545, staf1934 (2026)>
=2026MNRAS.545f1934L 2026MNRAS.545f1934L (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Stars, G-type ; Exoplanets ;
Radial velocities ; Optical
Keywords: techniques: photometric - techniques: radial velocities -
techniques: spectroscopic - planets and satellites: composition -
planets and satellites: fundamental parameters -
stars: individual (HD 85426)
Abstract:
We provide a detailed characterisation of the planetary system
orbiting HD 85426 (TOI-1774). This bright G-type star (M*:
0.99M☉; R*: 1.13R☉; age: 7.4Gyr; Vmag: 8.25) hosts a
transiting sub-Neptune, HD 85426 b, with an orbital period of
16.71-days and a blackbody equilibrium temperature of 824±11K. By
jointly analysing HARPS-N RVs, TESS, and CHEOPS photometric data and
using two different stellar activity mitigation techniques, we
constrain planet b's mass to 6.0±1.6M☉ and 8.5±1.4M☉,
depending on the mitigation technique. We investigate the dependence
of these results on the priors, data selection, and inclusion of other
Keplerians in the modelling. Using this approach, we identify the
presence of two non-transiting planetary companions with minimum
masses near 10 M_Earth and orbital periods of 35.7 and 89 days.
Additionally, we reject the initial hypothesis that the 35.7-day
periodic signal was due to stellar activity. We also determine HD
85426 b's radius to 2.78±0.05REarth and compute a transmission
spectroscopy metric in the range of 82 to 115, making this planet a
highly valuable target for atmospheric characterisation.
Description:
Radial velocity (RV) measurements and stellar activity indicators from
HARPS-N as well as photometric data from CHEOPS for HD 85426
(TOI-1774). The spectra from HARPS-N were processed with the HARPS-N
Data Reduction System 3.0.1 and, separately, with YARARA (Cretignier
et al., 2021A&A...653A..43C 2021A&A...653A..43C).
Objects:
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RA (2000) DE Designation(s)
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09 52 38.52 +35 06 41.9 HD 85426 = TOI-1774
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 30 4357 CHEOPS photometric data
table2.dat 163 127 HARPS-N DRS RVs
table3.dat 160 127 YARARA post-processed RVs
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 F12.6 d Time Barycentric Julian Date (BJD-2400000)
14- 21 F8.6 --- Flux Normalised flux
23- 30 F8.6 --- e_Flux Flux uncertainty
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 F12.6 d Time Barycentric Julian Date(BJD-2400000)
14- 26 F13.6 m/s RV Radial velocity
28- 35 F8.6 m/s e_RV Radial velocity uncertainty
37- 47 F11.6 m/s FWHM CCF FWHM
49- 56 F8.6 m/s e_FWHM CCF FWHM uncertainty
58- 67 F10.6 m/s BIS CCF bisector span
69- 76 F8.6 m/s e_BIS CCF bisector span uncertainty
78- 86 F9.6 % Contrast CCF contrast (in percent)
88- 95 F8.6 % e_Contrast CCF contrast uncertainty
97-104 F8.6 --- S-index S-index
106-113 F8.6 --- e_S-index S-index uncertainty
115-122 F8.6 --- Ha H-alpha index
124-131 F8.6 --- e_Ha H-alpha index uncertainty
133-140 F8.6 --- Na Sodium index
142-149 F8.6 --- e_Na Sodium index uncertainty
151-163 F13.6 m/s BERV Barycentric Earth radial velocity
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 F12.6 d Time Barycentric Julian Date (BJD-2400000)
14- 22 F9.6 m/s RV Radial velocity
24- 31 F8.6 m/s e_RV Radial velocity uncertainty
33- 43 F11.6 m/s FWHM CCF FWHM
45- 52 F8.6 m/s e_FWHM CCF FWHM uncertainty
54- 63 F10.6 m/s BIS CCF bisector span
65- 72 F8.6 m/s e_BIS CCF bisector span uncertainty
74- 82 F9.6 % Contrast CCF contrast (in percent)
84- 91 F8.6 % e_Contrast CCF contrast uncertainty
93-101 F9.6 --- S-index S-index
103-110 F8.6 --- e_S-index S-index uncertainty
112-119 F8.6 --- Ha H-alpha index
121-128 F8.6 --- e_Ha H-alpha index uncertainty
130-137 F8.6 --- Na Sodium index
139-146 F8.6 --- e_Na Sodium index uncertainty
148-160 F13.6 km/s BERV Barycentric Earth radial velocity
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Acknowledgements:
Florian Lienhard, lflorian (at) ethz.ch
(End) Patricia Vannier [CDS] 18-Feb-2026