Refined parameters, formation, and dynamical stability of the wild exoplanet system K2-312≡HD 80653

L. Naponiello; E. Poretti; K. Rice; A. S. Bonomo; L. Malavolta; M. Stalport; A. Vanderburg; C. Ziegler; L. Affer; M. Cecconi; A. Collier Cameron; R. Cosentino; M. Damasso; X. Dumusque; Y. N. E. Eschen; A. Ghedina; D. W. Latham; M. López-Morales; T. Lu; A. Massa; A. Mortier; B. A. Nicholson; L. Palethorpe; F. A. Pepe; A. Sozzetti; S. Udry; T. G. Wilson

doi:10.1051/0004-6361/202661259

Refined parameters, formation, and dynamical stability of the wild exoplanet system K2-312≡HD 80653

L. Naponiello^*
, E. Poretti
, K. Rice
, A. S. Bonomo
, L. Malavolta
, M. Stalport
, A. Vanderburg
, C. Ziegler
, L. Affer
, M. Cecconi
, A. Collier Cameron
, R. Cosentino
, M. Damasso
, X. Dumusque
, Y. N. E. Eschen
, A. Ghedina
, D. W. Latham
, M. López-Morales
, T. Lu
, A. Massa

A. Mortier, B. A. Nicholson, L. Palethorpe, F. A. Pepe, A. Sozzetti, S. Udry, T. G. Wilson

^*Corresponding author for this work

Physics and Astronomy

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

Abstract

Context: The architecture of planetary systems hosting ultra-short-period (USP) planets is a key diagnostic for understanding formation and migration scenarios. The presence of outer giant companions in these systems is of particular interest to test theories regarding dynamical effects and pebble accretion.

Aims: We present an extended radial velocity (RV) monitoring of the bright star K2-312≡HD80653, known to host a rocky USP super-Earth (P_b = 0.720 d). Previous studies identified a long-term trend and subsequently a Keplerian signal due to an outer highly eccentric giant planet, K2-312c. We aim to refine the orbital parameters of K2-312c by precisely monitoring its periastron passage and to model the formation and dynamical evolution of the system.

Methods: We analyzed a set of 237 HARPS-N high-resolution spectra, extending the observation baseline of previous literature by almost 4 years. We performed a joint analysis of the RVs together with K2 and TESS photometry to refine the ephemerides and properties of the two planets. To account for stellar activity, we coupled the Keplerian models with a Gaussian processes regression.

Results: K2-312c is a cold Jupiter on a wide orbit (orbital period refined to P_c = 871.32 d), with a minimum mass of M_c sin i ∼ 5 M_Jup and a refined eccentricity of e_c ∼ 0.85. It is among the most eccentric cold Jupiters known in multi-planet systems, and the only one that is highly eccentric and has a USP planet companion. Our simulations suggest that planet-planet scattering between two giant planets could have driven K2-312c to its current high eccentricity, ejected the other giant, and still allowed for the survival of K2-312b. The extended observation baseline further allowed us to identify the stellar rotation period and a long activity cycle, while a new K2 reduction improved the significance of the secondary eclipse detection for K2-312b.

Original language	English
Number of pages	14
Journal	Astronomy and Astrophysics
Early online date	21 Jul 2026
DOIs	https://doi.org/10.1051/0004-6361/202661259
Publication status	E-pub ahead of print - 21 Jul 2026

Keywords

astro-ph.EP

Access to Document

10.1051/0004-6361/202661259Licence: Creative Commons: Attribution (CC BY)

Finding a second Earth through stellar understanding
Mortier, A. (Principal Investigator)
Medical Research Council
1/06/24 → 31/05/28
Project: Research Councils
From oscillations to rotation: Detecting exoplanets through BiSON
Mortier, A. (Principal Investigator)
SCIENCE & TECHNOLOGY FACILITIES COUNCIL
1/04/24 → 31/03/27
Project: Research Councils

Cite this

Naponiello, L., Poretti, E., Rice, K., Bonomo, A. S., Malavolta, L., Stalport, M., Vanderburg, A., Ziegler, C., Affer, L., Cecconi, M., Cameron, A. C., Cosentino, R., Damasso, M., Dumusque, X., Eschen, Y. N. E., Ghedina, A., Latham, D. W., López-Morales, M., Lu, T., ... Wilson, T. G. (2026). Refined parameters, formation, and dynamical stability of the wild exoplanet system K2-312≡HD 80653. Astronomy and Astrophysics. Advance online publication. https://doi.org/10.1051/0004-6361/202661259

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title = "Refined parameters, formation, and dynamical stability of the wild exoplanet system K2-312≡HD 80653",

abstract = "Context: The architecture of planetary systems hosting ultra-short-period (USP) planets is a key diagnostic for understanding formation and migration scenarios. The presence of outer giant companions in these systems is of particular interest to test theories regarding dynamical effects and pebble accretion. Aims: We present an extended radial velocity (RV) monitoring of the bright star K2-312≡HD80653, known to host a rocky USP super-Earth (Pb = 0.720 d). Previous studies identified a long-term trend and subsequently a Keplerian signal due to an outer highly eccentric giant planet, K2-312c. We aim to refine the orbital parameters of K2-312c by precisely monitoring its periastron passage and to model the formation and dynamical evolution of the system. Methods: We analyzed a set of 237 HARPS-N high-resolution spectra, extending the observation baseline of previous literature by almost 4 years. We performed a joint analysis of the RVs together with K2 and TESS photometry to refine the ephemerides and properties of the two planets. To account for stellar activity, we coupled the Keplerian models with a Gaussian processes regression. Results: K2-312c is a cold Jupiter on a wide orbit (orbital period refined to Pc = 871.32 d), with a minimum mass of Mc sin i ∼ 5 MJup and a refined eccentricity of ec ∼ 0.85. It is among the most eccentric cold Jupiters known in multi-planet systems, and the only one that is highly eccentric and has a USP planet companion. Our simulations suggest that planet-planet scattering between two giant planets could have driven K2-312c to its current high eccentricity, ejected the other giant, and still allowed for the survival of K2-312b. The extended observation baseline further allowed us to identify the stellar rotation period and a long activity cycle, while a new K2 reduction improved the significance of the secondary eclipse detection for K2-312b.",

keywords = "astro-ph.EP",

author = "L. Naponiello and E. Poretti and K. Rice and Bonomo, \{A. S.\} and L. Malavolta and M. Stalport and A. Vanderburg and C. Ziegler and L. Affer and M. Cecconi and Cameron, \{A. Collier\} and R. Cosentino and M. Damasso and X. Dumusque and Eschen, \{Y. N. E.\} and A. Ghedina and Latham, \{D. W.\} and M. L{\'o}pez-Morales and T. Lu and A. Massa and A. Mortier and Nicholson, \{B. A.\} and L. Palethorpe and Pepe, \{F. A.\} and A. Sozzetti and S. Udry and Wilson, \{T. G.\}",

year = "2026",

month = jul,

day = "21",

doi = "10.1051/0004-6361/202661259",

language = "English",

journal = "Astronomy and Astrophysics",

issn = "0004-6361",

publisher = "EDP Sciences",

}

Naponiello, L, Poretti, E, Rice, K, Bonomo, AS, Malavolta, L, Stalport, M, Vanderburg, A, Ziegler, C, Affer, L, Cecconi, M, Cameron, AC, Cosentino, R, Damasso, M, Dumusque, X, Eschen, YNE, Ghedina, A, Latham, DW, López-Morales, M, Lu, T, Massa, A, Mortier, A, Nicholson, BA, Palethorpe, L, Pepe, FA, Sozzetti, A, Udry, S & Wilson, TG 2026, 'Refined parameters, formation, and dynamical stability of the wild exoplanet system K2-312≡HD 80653', Astronomy and Astrophysics. https://doi.org/10.1051/0004-6361/202661259

TY - JOUR

T1 - Refined parameters, formation, and dynamical stability of the wild exoplanet system K2-312≡HD 80653

AU - Naponiello, L.

AU - Poretti, E.

AU - Rice, K.

AU - Bonomo, A. S.

AU - Malavolta, L.

AU - Stalport, M.

AU - Vanderburg, A.

AU - Ziegler, C.

AU - Affer, L.

AU - Cecconi, M.

AU - Cameron, A. Collier

AU - Cosentino, R.

AU - Damasso, M.

AU - Dumusque, X.

AU - Eschen, Y. N. E.

AU - Ghedina, A.

AU - Latham, D. W.

AU - López-Morales, M.

AU - Lu, T.

AU - Massa, A.

AU - Mortier, A.

AU - Nicholson, B. A.

AU - Palethorpe, L.

AU - Pepe, F. A.

AU - Sozzetti, A.

AU - Udry, S.

AU - Wilson, T. G.

PY - 2026/7/21

Y1 - 2026/7/21

N2 - Context: The architecture of planetary systems hosting ultra-short-period (USP) planets is a key diagnostic for understanding formation and migration scenarios. The presence of outer giant companions in these systems is of particular interest to test theories regarding dynamical effects and pebble accretion. Aims: We present an extended radial velocity (RV) monitoring of the bright star K2-312≡HD80653, known to host a rocky USP super-Earth (Pb = 0.720 d). Previous studies identified a long-term trend and subsequently a Keplerian signal due to an outer highly eccentric giant planet, K2-312c. We aim to refine the orbital parameters of K2-312c by precisely monitoring its periastron passage and to model the formation and dynamical evolution of the system. Methods: We analyzed a set of 237 HARPS-N high-resolution spectra, extending the observation baseline of previous literature by almost 4 years. We performed a joint analysis of the RVs together with K2 and TESS photometry to refine the ephemerides and properties of the two planets. To account for stellar activity, we coupled the Keplerian models with a Gaussian processes regression. Results: K2-312c is a cold Jupiter on a wide orbit (orbital period refined to Pc = 871.32 d), with a minimum mass of Mc sin i ∼ 5 MJup and a refined eccentricity of ec ∼ 0.85. It is among the most eccentric cold Jupiters known in multi-planet systems, and the only one that is highly eccentric and has a USP planet companion. Our simulations suggest that planet-planet scattering between two giant planets could have driven K2-312c to its current high eccentricity, ejected the other giant, and still allowed for the survival of K2-312b. The extended observation baseline further allowed us to identify the stellar rotation period and a long activity cycle, while a new K2 reduction improved the significance of the secondary eclipse detection for K2-312b.

AB - Context: The architecture of planetary systems hosting ultra-short-period (USP) planets is a key diagnostic for understanding formation and migration scenarios. The presence of outer giant companions in these systems is of particular interest to test theories regarding dynamical effects and pebble accretion. Aims: We present an extended radial velocity (RV) monitoring of the bright star K2-312≡HD80653, known to host a rocky USP super-Earth (Pb = 0.720 d). Previous studies identified a long-term trend and subsequently a Keplerian signal due to an outer highly eccentric giant planet, K2-312c. We aim to refine the orbital parameters of K2-312c by precisely monitoring its periastron passage and to model the formation and dynamical evolution of the system. Methods: We analyzed a set of 237 HARPS-N high-resolution spectra, extending the observation baseline of previous literature by almost 4 years. We performed a joint analysis of the RVs together with K2 and TESS photometry to refine the ephemerides and properties of the two planets. To account for stellar activity, we coupled the Keplerian models with a Gaussian processes regression. Results: K2-312c is a cold Jupiter on a wide orbit (orbital period refined to Pc = 871.32 d), with a minimum mass of Mc sin i ∼ 5 MJup and a refined eccentricity of ec ∼ 0.85. It is among the most eccentric cold Jupiters known in multi-planet systems, and the only one that is highly eccentric and has a USP planet companion. Our simulations suggest that planet-planet scattering between two giant planets could have driven K2-312c to its current high eccentricity, ejected the other giant, and still allowed for the survival of K2-312b. The extended observation baseline further allowed us to identify the stellar rotation period and a long activity cycle, while a new K2 reduction improved the significance of the secondary eclipse detection for K2-312b.

KW - astro-ph.EP

U2 - 10.1051/0004-6361/202661259

DO - 10.1051/0004-6361/202661259

M3 - Article

SN - 0004-6361

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

ER -

Refined parameters, formation, and dynamical stability of the wild exoplanet system K2-312≡HD 80653

Abstract

Keywords

Access to Document

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Projects

Finding a second Earth through stellar understanding

From oscillations to rotation: Detecting exoplanets through BiSON

Cite this