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An ultra-short period super-Earth and sub-Neptune spanning the Radius Valley orbiting the kinematic thick disc star TOI-2345

Eschen, Yoshi Nike Emilia ; Ziegler, Carl ; Mustill, Alexander James LU orcid and Davies, Melvyn B. LU (2025) In Monthly Notices of the Royal Astronomical Society 544(2). p.2614-2636
Abstract
A crucial chemical link between stars and their orbiting exoplanets is thought to exist. If universal, this connection could affect the formation and evolution of all planets. Therefore, this potential vital link needs testing by characterizing exoplanets around chemically-diverse stars. We present the discovery of two planets orbiting the metal-poor, kinematic thick-disc K-dwarf TOI2345. TOI-2345 b is a super-Earth with a period of 1.05 d and TOI-2345 c is a sub-Neptune with a period of 21 d. In addition to the target being observed in four TESS sectors, we obtained five CHEOPS visits and 26 radial velocities from HARPS. By conducting a joint analysis of all the data, we find TOI-2345 b to have a radius of 1.504+0.047−0.044R⊕ and a mass... (More)
A crucial chemical link between stars and their orbiting exoplanets is thought to exist. If universal, this connection could affect the formation and evolution of all planets. Therefore, this potential vital link needs testing by characterizing exoplanets around chemically-diverse stars. We present the discovery of two planets orbiting the metal-poor, kinematic thick-disc K-dwarf TOI2345. TOI-2345 b is a super-Earth with a period of 1.05 d and TOI-2345 c is a sub-Neptune with a period of 21 d. In addition to the target being observed in four TESS sectors, we obtained five CHEOPS visits and 26 radial velocities from HARPS. By conducting a joint analysis of all the data, we find TOI-2345 b to have a radius of 1.504+0.047−0.044R⊕ and a mass of 3.49 ± 0.85 M⊕; and TOI-2345 c to have a radius of 2.451+0.045−0.046R⊕ and a mass of 7.27+2.27−2.45 M⊕. To explore chemical links between these planets and their host star, we model their interior structures newly accounting for devolatized stellar abundances. TOI-2345 adds to the limited sample of well-characterized planetary systems around thick disc stars. This system challenges theories of formation and populations of planets around thick disc stars with its Ultra-Short Period super-Earth and the wide period distribution of these two planets spanning the radius valley (Less)
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; ; and
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Contribution to journal
publication status
published
subject
keywords
techniques: photometric - techniques: radial velocities, planets and satellites: detection, planets and satellites: interiors, planets and satellites: individual: TOI-2345 b c, stars: individual: TOI-2345
in
Monthly Notices of the Royal Astronomical Society
volume
544
issue
2
pages
23 pages
publisher
Oxford University Press
ISSN
1365-2966
DOI
10.1093/mnras/staf1806
language
English
LU publication?
yes
id
45e5a508-452a-4002-8502-b6540c47b765
date added to LUP
2025-11-24 09:37:48
date last changed
2025-11-24 10:02:42
@article{45e5a508-452a-4002-8502-b6540c47b765,
  abstract     = {{A crucial chemical link between stars and their orbiting exoplanets is thought to exist. If universal, this connection could affect the formation and evolution of all planets. Therefore, this potential vital link needs testing by characterizing exoplanets around chemically-diverse stars. We present the discovery of two planets orbiting the metal-poor, kinematic thick-disc K-dwarf TOI2345. TOI-2345 b is a super-Earth with a period of 1.05 d and TOI-2345 c is a sub-Neptune with a period of 21 d. In addition to the target being observed in four TESS sectors, we obtained five CHEOPS visits and 26 radial velocities from HARPS. By conducting a joint analysis of all the data, we find TOI-2345 b to have a radius of 1.504+0.047−0.044R⊕ and a mass of 3.49 ± 0.85 M⊕; and TOI-2345 c to have a radius of 2.451+0.045−0.046R⊕ and a mass of 7.27+2.27−2.45 M⊕. To explore chemical links between these planets and their host star, we model their interior structures newly accounting for devolatized stellar abundances. TOI-2345 adds to the limited sample of well-characterized planetary systems around thick disc stars. This system challenges theories of formation and populations of planets around thick disc stars with its Ultra-Short Period super-Earth and the wide period distribution of these two planets spanning the radius valley}},
  author       = {{Eschen, Yoshi Nike Emilia and Ziegler, Carl and Mustill, Alexander James and Davies, Melvyn B.}},
  issn         = {{1365-2966}},
  keywords     = {{techniques: photometric - techniques: radial velocities; planets and satellites: detection; planets and satellites: interiors; planets and satellites: individual: TOI-2345 b  c; stars: individual: TOI-2345}},
  language     = {{eng}},
  month        = {{12}},
  number       = {{2}},
  pages        = {{2614--2636}},
  publisher    = {{Oxford University Press}},
  series       = {{Monthly Notices of the Royal Astronomical Society}},
  title        = {{An ultra-short period super-Earth and sub-Neptune spanning the Radius Valley orbiting the kinematic thick disc star TOI-2345}},
  url          = {{http://dx.doi.org/10.1093/mnras/staf1806}},
  doi          = {{10.1093/mnras/staf1806}},
  volume       = {{544}},
  year         = {{2025}},
}