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Two warm Neptunes transiting HIP 9618 revealed by TESS and Cheops

Osborn, H.P. ; Davies, M.B. LU ; Korth, J. LU and Winn, J.N. (2023) In Monthly Notices of the Royal Astronomical Society 523(2). p.3069-3089
Abstract
HIP 9618 (HD 12572, TOI-1471, TIC 306263608) is a bright (G = 9.0 mag) solar analogue. TESS photometry revealed the star to have two candidate planets with radii of 3.9 ± 0.044 R (HIP 9618 b) and 3.343 ± 0.039 R (HIP 9618 c). While the 20.77291 d period of HIP 9618 b was measured unambiguously, HIP 9618 c showed only two transits separated by a 680-d gap in the time series, leaving many possibilities for the period. To solve this issue, CHEOPS performed targeted photometry of period aliases to attempt to recover the true period of planet c, and successfully determined the true period to be 52.56349 d. High-resolution spectroscopy with HARPS-N, SOPHIE, and CAFE revealed a mass of 10.0 ± 3.1M for HIP 9618 b, which, according to our interior... (More)
HIP 9618 (HD 12572, TOI-1471, TIC 306263608) is a bright (G = 9.0 mag) solar analogue. TESS photometry revealed the star to have two candidate planets with radii of 3.9 ± 0.044 R (HIP 9618 b) and 3.343 ± 0.039 R (HIP 9618 c). While the 20.77291 d period of HIP 9618 b was measured unambiguously, HIP 9618 c showed only two transits separated by a 680-d gap in the time series, leaving many possibilities for the period. To solve this issue, CHEOPS performed targeted photometry of period aliases to attempt to recover the true period of planet c, and successfully determined the true period to be 52.56349 d. High-resolution spectroscopy with HARPS-N, SOPHIE, and CAFE revealed a mass of 10.0 ± 3.1M for HIP 9618 b, which, according to our interior structure models, corresponds to a 6.8 ± 1.4 per cent gas fraction. HIP 9618 c appears to have a lower mass than HIP 9618 b, with a 3-sigma upper limit of 50 d, opening the door for the atmospheric characterization of warm (Teq < 750 K) sub-Neptunes. © 2023 The Author(s). (Less)
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Contribution to journal
publication status
published
subject
keywords
binaries: spectroscopic, eclipses, occultations, planets and satellites: detection, surveys, Giant stars, Orbits, Photometry, Planets, Satellites, Binaries: spectroscopic, Eclipse, High-resolution spectroscopy, Interior structure, Low-mass, Neptune, Occultation, Planet-C, Planets and satellites: detections, Times series, Spectroscopic analysis
in
Monthly Notices of the Royal Astronomical Society
volume
523
issue
2
pages
21 pages
publisher
Oxford University Press
external identifiers
  • scopus:85162768259
ISSN
0035-8711
DOI
10.1093/mnras/stad1319
language
English
LU publication?
yes
id
e6e1dfb5-e918-4ecb-9a37-7b1594c1d3cb
date added to LUP
2023-11-15 10:17:08
date last changed
2024-04-13 00:49:19
@article{e6e1dfb5-e918-4ecb-9a37-7b1594c1d3cb,
  abstract     = {{HIP 9618 (HD 12572, TOI-1471, TIC 306263608) is a bright (G = 9.0 mag) solar analogue. TESS photometry revealed the star to have two candidate planets with radii of 3.9 ± 0.044 R (HIP 9618 b) and 3.343 ± 0.039 R (HIP 9618 c). While the 20.77291 d period of HIP 9618 b was measured unambiguously, HIP 9618 c showed only two transits separated by a 680-d gap in the time series, leaving many possibilities for the period. To solve this issue, CHEOPS performed targeted photometry of period aliases to attempt to recover the true period of planet c, and successfully determined the true period to be 52.56349 d. High-resolution spectroscopy with HARPS-N, SOPHIE, and CAFE revealed a mass of 10.0 ± 3.1M for HIP 9618 b, which, according to our interior structure models, corresponds to a 6.8 ± 1.4 per cent gas fraction. HIP 9618 c appears to have a lower mass than HIP 9618 b, with a 3-sigma upper limit of  50 d, opening the door for the atmospheric characterization of warm (Teq &lt; 750 K) sub-Neptunes. © 2023 The Author(s).}},
  author       = {{Osborn, H.P. and Davies, M.B. and Korth, J. and Winn, J.N.}},
  issn         = {{0035-8711}},
  keywords     = {{binaries: spectroscopic; eclipses; occultations; planets and satellites: detection; surveys; Giant stars; Orbits; Photometry; Planets; Satellites; Binaries: spectroscopic; Eclipse; High-resolution spectroscopy; Interior structure; Low-mass; Neptune; Occultation; Planet-C; Planets and satellites: detections; Times series; Spectroscopic analysis}},
  language     = {{eng}},
  number       = {{2}},
  pages        = {{3069--3089}},
  publisher    = {{Oxford University Press}},
  series       = {{Monthly Notices of the Royal Astronomical Society}},
  title        = {{Two warm Neptunes transiting HIP 9618 revealed by TESS and Cheops}},
  url          = {{http://dx.doi.org/10.1093/mnras/stad1319}},
  doi          = {{10.1093/mnras/stad1319}},
  volume       = {{523}},
  year         = {{2023}},
}