WASP-23b: a transiting hot Jupiter around a K dwarf and its Rossiter-McLaughlin effect
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We report the discovery of a new transiting planet in the southern hemisphere. It was found by the WASP-south transit survey and confirmed photometrically and spectroscopically by the 1.2 m Swiss Euler telescope, LCOGT 2m Faulkes South Telescope, the 60 cm TRAPPIST telescope, and the ESO 3.6 m telescope. The orbital period of the planet is 2.94 days. We find that it is a gas giant with a mass of 0.88 ± 0.10 MJ and an estimated radius of 0.96 ± 0.05 RJ. We obtained spectra during transit with the HARPS spectrograph and detect the Rossiter-McLaughlin effect despite its small amplitude. Because of the low signal-to-noise ratio of the effect and a small impact parameter, we cannot place a strong constraint on the projected spin-orbit angle. We find two conflicting values for the stellar rotation. We find, via spectral line broadening, that v sin I = 2.2 ± 0.3 km s-1, while applying another method, based on the activity level using the index , gives an equatorial rotation velocity of only v = 1.35 ± 0.20 km s-1. Using these as priors in our analysis, the planet might be either misaligned or aligned. This result raises doubts about the use of such priors. There is evidence of neither eccentricity nor any radial velocity drift with time.
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Self-citationTESS Transit Timing of Hundreds of Hot Jupiters
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“The references in Table 4 are: Fukui et al. (2016); Morvan et al. (2020); Bouchy et al. (2010); Barbieri et al. (2007); Ricci et al. (2015); Delrez et al. (2018); Oberst et al. (2017); Burke et al. (2010); Gillon et al. (2006); Sozzetti et al. (2009); Casasayas-Barris et al. (2019); Sada & Ramón-Fox (2016); Murgas et…”
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Self-citationObservational constraints on tidal effects using orbital eccentricities
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“…estimated from Quinn et al. 2012), c© 0000 RAS, MNRAS 000, 000–000 HAT-P-30b (e < 0.074, estimated from Johnson et al. 2011), WASP-23b (e < 0.062 at 3-σ, Triaud et al. 2011), WASP-34b (e < 0.058, estimated from Smalley et al. 2011), WASP-43b (e < 0.04 at 3-σ, Hellier et al. 2011), WASP-45b (e <…”
InfluentialSelf-citationWASP-80b has a dayside within the T-dwarf range ?
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“In the discovery paper, we were unable to distinguish the impact parameter from zero, which led the fitting procedure of the Rossiter– McLaughlin effect to produce degenerate solutions for the projected spin–orbit angle β (e.g. Albrecht et al. 2011; Triaud et al. 2011).”
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“…al. 2010; (60) Pál et al. 2010; (61) Collier Cameron et al. 2010; (62) Maxted et al. 2010a; (63) Barros et al. 2011a; (64) Smalley et al. 2011; (65) Triaud et al. 2011; (66) Faedi et al. 2011; (67) Anderson et al. 2011c; (68) Gillon et al. 2011; (69) Anderson et al. 2011a; (70) Hellier et al.…”
Self-citationTIDAL DISSIPATION AND OBLIQUITY EVOLUTION IN HOT JUPITER SYSTEMS
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“Finally, as in A12, we excluded WASP-23 b because the misalignment is not well constrained (Triaud et al. 2011).”
BackgroundExoClock Project. II. A Large-scale Integrated Study with 180 Updated Exoplanet Ephemerides
Kokori, A., Tsiaras, A., Edwards, B., Rocchetto, M., Tinetti, G., Bewersdorff, L., Jongen, Y., Lekkas, G., Pantelidou, G., Poultourtzidis, E., et al. (2021) · Astrophysical Journal Supplement Series · doi:10.3847/1538-4365/ac3a10 · Cited by 42 · see citing works
“Triaud et al. (2011); Nikolov et al. (2013) 2.”
InfluentialAnderson, D., Cameron, A., Hellier, C., Lendl, M., Lister, T., Maxted, P., Queloz, D., Smalley, B., Smith, A. M. S., Triaud, A., et al. (2014) · Astronomy and Astrophysics · doi:10.1051/0004-6361/201423591 · Cited by 38 · see citing works
“Due to the low impact parameter of WASP-28b determinations of v sinI∗ and λ are degenerate (Triaud et al. 2011; Albrecht et al. 2011; Anderson et al. 2011a).”
BackgroundSelf-citationRossiter–McLaughlin effect measurements for WASP-16, WASP-25 and WASP-31★
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“2 from their paper, with the addition of all complete RM measurements made since its publication (except WASP-23 (Triaud et al. 2011), for which the result is still highly uncertain, and WASP-26 (Anderson et al. 2011), which showed only a very low amplitude and was classed as a non-detection); we…”
BackgroundResultSelf-citationMass and period limits on the ringed companion transiting the young star J1407
Kenworthy, M. A., Lacour, S., Kraus, A., Triaud, A. H. M. J., Mamajek, E. E., Scott, E. L., Ségransan, D., Ireland, M., Hambsch, F.-J., Reichart, D. E., et al. (2015) · Monthly Notices of the Royal Astronomical Society · doi:10.1093/mnras/stu2067 · Cited by 36 · see citing works
“Over seven years, it has detected over 100 transiting exoplanets (Wilson et al. 2008; Triaud et al. 2011; Hellier et al. 2014).”
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“The reasons to use √ e cos ω and √ e sin ω as jump parameters instead of the more traditional e cos ω and e sin ω are detailed in Triaud et al. (2011).”
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“…CoRoT-19 (Guenther et al. 2012), HATS-14 (Zhou et al. 2015), HAT-P-27 (Brown et al. 2012), WASP-1 (Simpson et al. 2011; Albrecht et al. 2011), WASP-2 (Triaud et al. 2010; Albrecht et al. 2011), WASP-23 (Triaud et al. 2011), WASP-49 (Wyttenbach et al. 2017), and WASP-134 (Anderson et al. 2018).”
ROSSITER–MCLAUGHLIN OBSERVATIONS OF 55 Cnc e
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“The impossibility of constraining the spin–orbit angle of the system is illustrated in Figure 2, which shows the typical crescent shape expected when there is degeneracy between fast rotation and polar orbits and slow rotation and alignment (Triaud et al. 2011; Albrecht et al. 2011).”
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“In the second step we complemented the GROND photometry with the radial velocity (RV) measurements of WASP-23, reported by Triaud et al. (2011) and performed a joint photometry plus RV MCMC analysis using exofast (Eastman et al. 2013).”
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Revisiting the correlation between stellar activity and planetary surface gravity
Figueira, P., Oshagh, M., Adibekyan, V., & Santos, N. (2014) · doi:10.1051/0004-6361/201424902 · Cited by 25
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Self-citationThe atmospheric parameters of FGK stars using wavelet analysis of CORALIE spectra
Gill, S., Maxted, P., & Smalley, B. (2018) · Astronomy and Astrophysics · doi:10.1051/0004-6361/201731954 · Cited by 13 · see citing works
“Measurements of [Fe/H] for the M-dwarf can be adopted from the FGK companion with the assumption that they both formed from the same parent molecular cloud (Triaud et al. 2011).”
BackgroundSelf-citationMon-735: a new low-mass pre-main-sequence eclipsing binary in NGC 2264
Gillen, E., Hillenbrand, L., Stauffer, J., Aigrain, S., Rebull, L., & Cody, A. (2020) · Monthly notices of the Royal Astronomical Society · doi:10.1093/mnras/staa1016 · Cited by 9 · see citing works
“GP-EBOP further parametrizes the eccentricity and longitude of periastron terms using their combinations √ e cos ω and √ e sin ω, rather than e cos ω and e sin ω, to avoid inducing a prior on the orbital eccentricity proportional to e (Ford 2006; Triaud et al. 2011).”
MethodWang, X.-Y., Wang, S.-H., & Ong, J. M. J. (2025) · Astrophysical Journal Letters · doi:10.3847/2041-8213/ae21c5 · Cited by 7 · see citing works
“…a weak signal of a prograde orbit was detected with ∼ 2 σ confidence), WASP-2 (Triaud et al. 2010; Albrecht et al. 2011, no RM signal was detected), WASP-23 (Triaud et al. 2011, the λ constraint is sensitive to the v sin i prior due to the low transit impact parameter), WASP-49 (Wyttenbach et…”
The EBLM Project—From False Positives to Benchmark Stars and Circumbinary Exoplanets
Maxted, P., Triaud, A., & Martin, D. V. (2023) · Universe · doi:10.3390/universe9120498 · Cited by 6 · see citing works
Self-citationExoClock Project. IV. A Homogeneous Catalog of 620 Updated Exoplanet Ephemerides
Kokori, A., Tsiaras, A., Pantelidou, G., Jones, A., Siakas, A., Edwards, B., Tinetti, G., Wünsche, A., Jongen, Y., Libotte, F., et al. (2026) · Astrophysical Journal Supplement Series · doi:10.3847/1538-4365/ae3238 · Cited by 1 · see citing works
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Distinct e–λ Trends in Three Gas-giant Mass Regimes
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“To mitigate the well-known eccentricity bias toward large values ( L. B. Lucy & M. A. Sweeney 1971 ) , we fitted the parameters * e and * e sin instead of eccentricity and argument of periastron separately ( A. H. M. J. Triaud et al. 2011; J. Eastman et al. 2013 ) .”
- Authors
- Triaud, A. H. M. J., Queloz, D., Hellier, C., Gillon, M., Smalley, B., Hebb, L., Collier Cameron, A., Anderson, D., Boisse, I., Hébrard, G., Jehin, E., Lister, T., Lovis, C., Maxted, P. F. L., Pepe, F., Pollacco, D., Ségransan, D., Simpson, E., Udry, S., & West, R.
- Affiliations
- University of Geneva (CH)
- Keele University (GB)
- University of Liège (BE)
- Vanderbilt University (US)
- Centre National de la Recherche Scientifique (FR)
- Las Cumbres Observatory Global Telescope Network (US)
- Queen's University Belfast (GB)
- University of Leicester (GB)
- ORCID
- Venue
- Astronomy & Astrophysics
- Publisher
- EDP Sciences
- Published
- 2011-06-06
- Volume
- 531
- Pages
- A24
- ISSN
- 0004-6361 (ISSN-L)
- 1432-0746
- OpenAlex
- W2137520028
- Cited by
- 52
- References
- 68
- Citations by year
- 2026: 6 · 2025: 2 · 2024: 3 · 2023: 5 · 2022: 3 · 2020: 1 · 2019: 2 · 2018: 3 · 2017: 4 · 2016: 3 · 2015: 3 · 2014: 6 · 2013: 5 · 2012: 6
- FWCI
- 2.89
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Astronomy and Astrophysics (publishedVersion)
- University of Birmingham Research Portal (University of Birmingham) (publishedVersion)
- Archive ouverte UNIGE (University of Geneva) (publishedVersion)
- arXiv (Cornell University) (submittedVersion)
- Springer Link (Chiba Institute of Technology) (submittedVersion)
- HAL (submittedVersion, other-oa)
- Leicester Research Archive (University of Leicester) (submittedVersion)
- ORBi (University of Liège) (submittedVersion, other-oa)
- Research Portal (Queen's University Belfast) (submittedVersion)
- Archive ouverte UNIGE (University of Geneva) (submittedVersion, cc-by)
- arXiv (Cornell University)
- Funders
- Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
- Fonds De La Recherche Scientifique - FNRS
- Science and Technology Facilities Council (PP/F000081/1, ST/J000035/1, PP/F000065/1, PP/F000057/1, PP/F000073/1, PP/D000955/1, ST/G002355/1, ST/I001719/1)
- Topics
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Stellar, planetary, and galactic studies
- Physical Sciences › Physics and Astronomy › Instrumentation › Astronomy and Astrophysical Research
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › History and Developments in Astronomy
- Keywords
- hot Jupiters, transiting exoplanets, Rossiter-McLaughlin effect, K dwarfs, spin-orbit misalignment, stellar rotation velocity, stellar activity, impact parameter, orbital eccentricity
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