HARPS-N, TESS, and CHEOPS∗ discover a transiting sub-Neptune and two outer companions around the bright solar analogue HD 85426

F. Lienhard; A. Mortier; A. Collier Cameron; M. Cretignier; L. Borsato; A. Anna John; J. A. Egger; M. Stalport; T. G. Wilson; A. Deline; A. Fortier; D. W. Latham; L. Malavolta; P. F.L. Maxted; S. G. Sousa; S. L. Grimm; L. Buchhave; Y. Alibert; B. S. Lakeland; X. Dumusque; J. Cabrera; L. Naponiello; A. C.M. Correia; F. Rescigno; L. Fossati; A. Sozzetti; R. Alonso; T. Bárczy; D. Barrado; S. C.C. Barros; W. Baumjohann; W. Benz; N. Billot; A. Brandeker; C. Broeg; K. Collins; Sz Csizmadia; P. E. Cubillos; M. B. Davies; M. Deleuil; O. D.S. Demangeon; B. O. Demory; A. Derekas; B. Edwards; D. Ehrenreich; A. Erikson; M. Fridlund; D. Gandolfi; K. Gazeas; M. Gillon; M. Güdel; M. N. Günther; R. Haywood; A. Heitzmann; Ch Helling; K. G. Isaak; J. M. Jenkins; L. L. Kiss; J. Korth; K. W.F. Lam; J. Laskar; A. Lecavelier Des Etangs; A. Leleu; M. Lendl; D. Magrin; A. F.Martínez Fiorenzano; B. Merín; C. Mordasini; V. Nascimbeni; G. Olofsson; H. P. Osborn; R. Ottensamer; I. Pagano; L. Palethorpe; E. Pallé; G. Peter; D. Piazza; G. Piotto; D. Pollacco; D. Queloz; R. Ragazzoni; N. Rando; H. Rauer; I. Ribas; K. Rice; N. C. Santos; G. Scandariato; D. Ségransan; A. E. Simon; A. M.S. Smith; S. Sulis; Gy M. Szabó; S. Udry; S. Ulmer-Moll; V. Van Grootel; J. Venturini; E. Villaver; N. A. Walton; T. Zingales

doi:10.1093/mnras/staf1934

HARPS-N, TESS, and CHEOPS∗ discover a transiting sub-Neptune and two outer companions around the bright solar analogue HD 85426

F. Lienhard
, A. Mortier
, A. Collier Cameron
, M. Cretignier
, L. Borsato
, A. Anna John
, J. A. Egger
, M. Stalport
, T. G. Wilson
, A. Deline
, A. Fortier
, D. W. Latham
, L. Malavolta
, P. F.L. Maxted
, S. G. Sousa
, S. L. Grimm
, L. Buchhave
, Y. Alibert
, B. S. Lakeland
, X. Dumusque

J. Cabrera, L. Naponiello, A. C.M. Correia, F. Rescigno, L. Fossati, A. Sozzetti, R. Alonso, T. Bárczy, D. Barrado, S. C.C. Barros, W. Baumjohann, W. Benz, N. Billot, A. Brandeker, C. Broeg, K. Collins, Sz Csizmadia, P. E. Cubillos, M. B. Davies, M. Deleuil, O. D.S. Demangeon, B. O. Demory, A. Derekas, B. Edwards, D. Ehrenreich, A. Erikson, M. Fridlund, D. Gandolfi, K. Gazeas, M. Gillon, M. Güdel, M. N. Günther, R. Haywood, A. Heitzmann, Ch Helling, K. G. Isaak, J. M. Jenkins, L. L. Kiss, J. Korth, K. W.F. Lam, J. Laskar, A. Lecavelier Des Etangs, A. Leleu, M. Lendl, D. Magrin, A. F.Martínez Fiorenzano, B. Merín, C. Mordasini, V. Nascimbeni, G. Olofsson, H. P. Osborn, R. Ottensamer, I. Pagano, L. Palethorpe, E. Pallé, G. Peter, D. Piazza, G. Piotto, D. Pollacco, D. Queloz, R. Ragazzoni, N. Rando, H. Rauer, I. Ribas, K. Rice, N. C. Santos, G. Scandariato, D. Ségransan, A. E. Simon, A. M.S. Smith, S. Sulis, Gy M. Szabó, S. Udry, S. Ulmer-Moll, V. Van Grootel, J. Venturini, E. Villaver, N. A. Walton, T. Zingales

ETH Zurich
University of Birmingham
University of St Andrews
University of Oxford
INAF Osservatorio Astronomico di Padova
University of Bern, Institute of Applied Physics
University of Liège
University of Warwick
Université de Genève
University of Bern
Center for Astrophysics | Harvard & Smithsonian
University of Padova
Keele University
Ipatimup Diagnósticos
University of Zurich
Technical University of Denmark
University of Exeter
DLR
Istituto di Astrofisica e Planetologia Spaziali (IAPS)
University of Coimbra
Space Research Institute
Instituto de Astrofisica de Canarias
Research Unit; CIBERNED and Universidad de La Laguna
Admatis Ltd.
ESAC campus
Stockholm University
Lund University
LAM
University of Bern, Faculty of Medicine
Eötvös Loránd University
SRON - Netherlands Institute for Space Research
University of Geneva
University of Leiden
Onsala Space Observatory
University of Turin
University of Athens
University of Vienna
ESTEC - European Space Research and Technology Centre
Graz University of Technology
NASA Ames Research Center
Konkoly Observatory
Sorbonne Univ.
Institut d’Astrophysique de Paris
Inaf - Fund. Galileo Galilei
INAF Osservatorio Astrofisico di Catania
University of Edinburgh, Institute for Astronomy
University of Edinburgh
University of Cambridge
Free University of Berlin
Campus UAB
Institut d’Estudis Espacials de Catalunya (IEEC)
HUN-REN–ELTE Exoplanet Research Group
Institute of Astronomy

Research output: Contribution to journal › Article › peer-review

Abstract

We provide a detailed characterization of the planetary system orbiting HD 85426 (TOI-1774). This bright G-type star (: 0.99;: 1.13; age: 7.4 Gyr; V mag: 8.25) hosts a transiting sub-Neptune, HD 85426 b, with an orbital period of 16.71 d and a blackbody equilibrium temperature of K. 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 and, 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 and orbital periods of 35.7 and 89 d. Additionally, we reject the initial hypothesis that the 35.7-d periodic signal was due to stellar activity. We also determine HD 85426 b's radius to be and compute a transmission spectroscopy metric in the range of 82 to 115, making this planet a highly valuable target for atmospheric characterization.

Original language	English
Article number	staf1934
Journal	Monthly Notices of the Royal Astronomical Society
Volume	545
Issue number	3
DOIs	https://doi.org/10.1093/mnras/staf1934
Publication status	Published - 1 Jan 2026
Externally published	Yes

Keywords

planets and satellites: composition
planets and satellites: fundamental parameters
stars: individual (HD 85426)
techniques: photometric
techniques: radial velocities
techniques: spectroscopic

Access to Document

10.1093/mnras/staf1934

Cite this

Lienhard, F., Mortier, A., Cameron, A. C., Cretignier, M., Borsato, L., John, A. 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., ... Zingales, T. (2026). HARPS-N, TESS, and CHEOPS∗ discover a transiting sub-Neptune and two outer companions around the bright solar analogue HD 85426. Monthly Notices of the Royal Astronomical Society, 545(3), Article staf1934. https://doi.org/10.1093/mnras/staf1934

@article{6a123eeae64c4af7814d200574578324,

title = "HARPS-N, TESS, and CHEOPS∗ discover a transiting sub-Neptune and two outer companions around the bright solar analogue HD 85426",

abstract = "We provide a detailed characterization of the planetary system orbiting HD 85426 (TOI-1774). This bright G-type star (: 0.99;: 1.13; age: 7.4 Gyr; V mag: 8.25) hosts a transiting sub-Neptune, HD 85426 b, with an orbital period of 16.71 d and a blackbody equilibrium temperature of K. 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 and, 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 and orbital periods of 35.7 and 89 d. Additionally, we reject the initial hypothesis that the 35.7-d periodic signal was due to stellar activity. We also determine HD 85426 b's radius to be and compute a transmission spectroscopy metric in the range of 82 to 115, making this planet a highly valuable target for atmospheric characterization.",

keywords = "planets and satellites: composition, planets and satellites: fundamental parameters, stars: individual (HD 85426), techniques: photometric, techniques: radial velocities, techniques: spectroscopic",

author = "F. Lienhard and A. Mortier and Cameron, \{A. Collier\} and M. Cretignier and L. Borsato and John, \{A. Anna\} and Egger, \{J. A.\} and M. Stalport and Wilson, \{T. G.\} and A. Deline and A. Fortier and Latham, \{D. W.\} and L. Malavolta and Maxted, \{P. F.L.\} and Sousa, \{S. G.\} and Grimm, \{S. L.\} and L. Buchhave and Y. Alibert and Lakeland, \{B. S.\} and X. Dumusque and J. Cabrera and L. Naponiello and Correia, \{A. C.M.\} and F. Rescigno and L. Fossati and A. Sozzetti and R. Alonso and T. B{\'a}rczy and D. Barrado and Barros, \{S. C.C.\} and W. Baumjohann and W. Benz and N. Billot and A. Brandeker and C. Broeg and K. Collins and Sz Csizmadia and Cubillos, \{P. E.\} and Davies, \{M. B.\} and M. Deleuil and Demangeon, \{O. D.S.\} and Demory, \{B. O.\} and A. Derekas and B. Edwards and D. Ehrenreich and A. Erikson and M. Fridlund and D. Gandolfi and K. Gazeas and M. Gillon and M. G{\"u}del and G{\"u}nther, \{M. N.\} and R. Haywood and A. Heitzmann and Ch Helling and Isaak, \{K. G.\} and Jenkins, \{J. M.\} and Kiss, \{L. L.\} and J. Korth and Lam, \{K. W.F.\} and J. Laskar and \{Lecavelier Des Etangs\}, A. and A. Leleu and M. Lendl and D. Magrin and Fiorenzano, \{A. F.Mart{\'i}nez\} and B. Mer{\'i}n and C. Mordasini and V. Nascimbeni and G. Olofsson and Osborn, \{H. P.\} and R. Ottensamer and I. Pagano and L. Palethorpe and E. Pall{\'e} and G. Peter and D. Piazza and G. Piotto and D. Pollacco and D. Queloz and R. Ragazzoni and N. Rando and H. Rauer and I. Ribas and K. Rice and Santos, \{N. C.\} and G. Scandariato and D. S{\'e}gransan and Simon, \{A. E.\} and Smith, \{A. M.S.\} and S. Sulis and Szab{\'o}, \{Gy M.\} and S. Udry and S. Ulmer-Moll and \{Van Grootel\}, V. and J. Venturini and E. Villaver and Walton, \{N. A.\} and T. Zingales",

note = "Publisher Copyright: {\textcopyright} 2025 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society.",

year = "2026",

month = jan,

day = "1",

doi = "10.1093/mnras/staf1934",

language = "English",

volume = "545",

journal = "Monthly Notices of the Royal Astronomical Society",

issn = "0035-8711",

number = "3",

}

Lienhard, F, Mortier, A, Cameron, AC, Cretignier, M, Borsato, L, John, AA, Egger, JA, Stalport, M, Wilson, TG, Deline, A, Fortier, A, Latham, DW, Malavolta, L, Maxted, PFL, Sousa, SG, Grimm, SL, Buchhave, L, Alibert, Y, Lakeland, BS, Dumusque, X, Cabrera, J, Naponiello, L, Correia, ACM, Rescigno, F, Fossati, L, Sozzetti, A, Alonso, R, Bárczy, T, Barrado, D, Barros, SCC, Baumjohann, W, Benz, W, Billot, N, Brandeker, A, Broeg, C, Collins, K, Csizmadia, S, Cubillos, PE, Davies, MB, Deleuil, M, Demangeon, ODS, Demory, BO, Derekas, A, Edwards, B, Ehrenreich, D, Erikson, A, Fridlund, M, Gandolfi, D, Gazeas, K, Gillon, M, Güdel, M, Günther, MN, Haywood, R, Heitzmann, A, Helling, C, Isaak, KG, Jenkins, JM, Kiss, LL, Korth, J, Lam, KWF, Laskar, J, Lecavelier Des Etangs, A, Leleu, A, Lendl, M, Magrin, D, Fiorenzano, AFM, Merín, B, Mordasini, C, Nascimbeni, V, Olofsson, G, Osborn, HP, Ottensamer, R, Pagano, I, Palethorpe, L, Pallé, E, Peter, G, Piazza, D, Piotto, G, Pollacco, D, Queloz, D, Ragazzoni, R, Rando, N, Rauer, H, Ribas, I, Rice, K, Santos, NC, Scandariato, G, Ségransan, D, Simon, AE, Smith, AMS, Sulis, S, Szabó, GM, Udry, S, Ulmer-Moll, S, Van Grootel, V, Venturini, J, Villaver, E, Walton, NA & Zingales, T 2026, 'HARPS-N, TESS, and CHEOPS∗ discover a transiting sub-Neptune and two outer companions around the bright solar analogue HD 85426', Monthly Notices of the Royal Astronomical Society, vol. 545, no. 3, staf1934. https://doi.org/10.1093/mnras/staf1934

TY - JOUR

T1 - HARPS-N, TESS, and CHEOPS∗ discover a transiting sub-Neptune and two outer companions around the bright solar analogue HD 85426

AU - Lienhard, F.

AU - Mortier, A.

AU - Cameron, A. Collier

AU - Cretignier, M.

AU - Borsato, L.

AU - John, A. Anna

AU - Egger, J. A.

AU - Stalport, M.

AU - Wilson, T. G.

AU - Deline, A.

AU - Fortier, A.

AU - Latham, D. W.

AU - Malavolta, L.

AU - Maxted, P. F.L.

AU - Sousa, S. G.

AU - Grimm, S. L.

AU - Buchhave, L.

AU - Alibert, Y.

AU - Lakeland, B. S.

AU - Dumusque, X.

AU - Cabrera, J.

AU - Naponiello, L.

AU - Correia, A. C.M.

AU - Rescigno, F.

AU - Fossati, L.

AU - Sozzetti, A.

AU - Alonso, R.

AU - Bárczy, T.

AU - Barrado, D.

AU - Barros, S. C.C.

AU - Baumjohann, W.

AU - Benz, W.

AU - Billot, N.

AU - Brandeker, A.

AU - Broeg, C.

AU - Collins, K.

AU - Csizmadia, Sz

AU - Cubillos, P. E.

AU - Davies, M. B.

AU - Deleuil, M.

AU - Demangeon, O. D.S.

AU - Demory, B. O.

AU - Derekas, A.

AU - Edwards, B.

AU - Ehrenreich, D.

AU - Erikson, A.

AU - Fridlund, M.

AU - Gandolfi, D.

AU - Gazeas, K.

AU - Gillon, M.

AU - Güdel, M.

AU - Günther, M. N.

AU - Haywood, R.

AU - Heitzmann, A.

AU - Helling, Ch

AU - Isaak, K. G.

AU - Jenkins, J. M.

AU - Kiss, L. L.

AU - Korth, J.

AU - Lam, K. W.F.

AU - Laskar, J.

AU - Lecavelier Des Etangs, A.

AU - Leleu, A.

AU - Lendl, M.

AU - Magrin, D.

AU - Fiorenzano, A. F.Martínez

AU - Merín, B.

AU - Mordasini, C.

AU - Nascimbeni, V.

AU - Olofsson, G.

AU - Osborn, H. P.

AU - Ottensamer, R.

AU - Pagano, I.

AU - Palethorpe, L.

AU - Pallé, E.

AU - Peter, G.

AU - Piazza, D.

AU - Piotto, G.

AU - Pollacco, D.

AU - Queloz, D.

AU - Ragazzoni, R.

AU - Rando, N.

AU - Rauer, H.

AU - Ribas, I.

AU - Rice, K.

AU - Santos, N. C.

AU - Scandariato, G.

AU - Ségransan, D.

AU - Simon, A. E.

AU - Smith, A. M.S.

AU - Sulis, S.

AU - Szabó, Gy M.

AU - Udry, S.

AU - Ulmer-Moll, S.

AU - Van Grootel, V.

AU - Venturini, J.

AU - Villaver, E.

AU - Walton, N. A.

AU - Zingales, T.

PY - 2026/1/1

Y1 - 2026/1/1

N2 - We provide a detailed characterization of the planetary system orbiting HD 85426 (TOI-1774). This bright G-type star (: 0.99;: 1.13; age: 7.4 Gyr; V mag: 8.25) hosts a transiting sub-Neptune, HD 85426 b, with an orbital period of 16.71 d and a blackbody equilibrium temperature of K. 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 and, 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 and orbital periods of 35.7 and 89 d. Additionally, we reject the initial hypothesis that the 35.7-d periodic signal was due to stellar activity. We also determine HD 85426 b's radius to be and compute a transmission spectroscopy metric in the range of 82 to 115, making this planet a highly valuable target for atmospheric characterization.

AB - We provide a detailed characterization of the planetary system orbiting HD 85426 (TOI-1774). This bright G-type star (: 0.99;: 1.13; age: 7.4 Gyr; V mag: 8.25) hosts a transiting sub-Neptune, HD 85426 b, with an orbital period of 16.71 d and a blackbody equilibrium temperature of K. 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 and, 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 and orbital periods of 35.7 and 89 d. Additionally, we reject the initial hypothesis that the 35.7-d periodic signal was due to stellar activity. We also determine HD 85426 b's radius to be and compute a transmission spectroscopy metric in the range of 82 to 115, making this planet a highly valuable target for atmospheric characterization.

KW - planets and satellites: composition

KW - planets and satellites: fundamental parameters

KW - stars: individual (HD 85426)

KW - techniques: photometric

KW - techniques: radial velocities

KW - techniques: spectroscopic

UR - https://www.scopus.com/pages/publications/105026662182

U2 - 10.1093/mnras/staf1934

DO - 10.1093/mnras/staf1934

M3 - Article

AN - SCOPUS:105026662182

SN - 0035-8711

VL - 545

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

IS - 3

M1 - staf1934

ER -

HARPS-N, TESS, and CHEOPS∗ discover a transiting sub-Neptune and two outer companions around the bright solar analogue HD 85426

Abstract

Keywords

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