TOI-2458 b: A mini-Neptune consistent with in situ hot Jupiter formation

We report on the discovery and spectroscopic confirmation of TOI-2458 b, a transiting mini-Neptune around an F-type star leaving the main-sequence with a mass of M ★ = 1.05 ± 0.03 M ⊙ , a radius of R ★ = 1.31 ± 0.03 R ⊙ , an effective temperature of T eff = 6005 ± 50 K, and a metallicity of −0.10 ± 0.05 dex. By combining TESS photometry with high-resolution spectra acquired with the HARPS spectrograph, we found that the transiting planet has an orbital period of −3.74 days, a mass of M p = 13.31 ± 0.99 M ⊕ and a radius of R p = 2.83 ± 0.20 R ⊕ . The host star TOI-2458 shows a short activity cycle of ~54 days revealed in the HARPS S-index and Ha times series. We took the opportunity to investigate other F stars showing activity cycle periods comparable to that of TOI-2458 and found that they have shorter rotation periods than would be expected based on the gyrochronology predictions. In addition, we determined TOI-2458’s stellar inclination angle to be i * = 10.6 −10.6 +13.3 degrees. We discuss that both phenomena (fast stellar rotation and planet orbit inclination) could be explained by in situ formation of a hot Jupiter interior to TOI-2458 b. It is plausible that this hot Jupiter was recently engulfed by the star. Analysis of HARPS spectra has identified the presence of another planet with a period of P = 16.55 ± 0.06 days and a minimum mass of M p sin i = 10.22 ± 1.90 M ⊕ . Using dynamical stability analysis, we constrained the mass of this planet to the range M c ≃ (10, 25) M ⊕ .

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Publication Details

Journal
Astronomy and Astrophysics
Published
2024-12-12
DOI
https://doi.org/10.1051/0004-6361/202451057
Citations
2
Primary Topic
Stellar, planetary, and galactic studies
Type
article
Field-Weighted Citation Impact
0.66

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article

TOI-2458 b: A mini-Neptune consistent with in situ hot Jupiter formation

H. J. Deeg, S. Mathur, Ε. Πάλλη, D. Gandolfi et al.
2 citations
Astronomy and Astrophysics
Stellar, planetary, and galactic studies
0.66
article

TOI-2458 b: A mini-Neptune consistent with in situ hot Jupiter formation

H. J. Deeg, S. Mathur, Ε. Πάλλη, D. Gandolfi, Michael B. Lund, J. Šubjak, E. W. Guenther, Karen A. Collins, J. Korth, P. Kábath, Seth Redfield, Richard P. Schwarz, John H. Livingston, J. Orell-Miquel, David Rapetti, David Watanabe, Dawid Jankowski, Toshiyuki Mizuki, Elisa Goffo, David R. Ciardi, Krzysztof Goździewski, Norio Narita, L. M. Serrano, William D. Cochran, T. G. Wilson, G. Nowak, Allyson Bieryla, R. A. García, Joseph D. Twicken, Carina M. Persson, A. P. Hatzes, Fei Dai, Jon M. Jenkins, Carl Ziegler, David W. Latham, Joshua N. Winn
article en
2 citations

Abstract

We report on the discovery and spectroscopic confirmation of TOI-2458 b, a transiting mini-Neptune around an F-type star leaving the main-sequence with a mass of M ★ = 1.05 ± 0.03 M ⊙ , a radius of R ★ = 1.31 ± 0.03 R ⊙ , an effective temperature of T eff = 6005 ± 50 K, and a metallicity of −0.10 ± 0.05 dex. By combining TESS photometry with high-resolution spectra acquired with the HARPS spectrograph, we found that the transiting planet has an orbital period of −3.74 days, a mass of M p = 13.31 ± 0.99 M ⊕ and a radius of R p = 2.83 ± 0.20 R ⊕ . The host star TOI-2458 shows a short activity cycle of ~54 days revealed in the HARPS S-index and Ha times series. We took the opportunity to investigate other F stars showing activity cycle periods comparable to that of TOI-2458 and found that they have shorter rotation periods than would be expected based on the gyrochronology predictions. In addition, we determined TOI-2458’s stellar inclination angle to be i * = 10.6 −10.6 +13.3 degrees. We discuss that both phenomena (fast stellar rotation and planet orbit inclination) could be explained by in situ formation of a hot Jupiter interior to TOI-2458 b. It is plausible that this hot Jupiter was recently engulfed by the star. Analysis of HARPS spectra has identified the presence of another planet with a period of P = 16.55 ± 0.06 days and a minimum mass of M p sin i = 10.22 ± 1.90 M ⊕ . Using dynamical stability analysis, we constrained the mass of this planet to the range M c ≃ (10, 25) M ⊕ .

Astronomy and AstrophysicsVol. 693
National Aeronautics and Space Administration, UK Space Agency, University of Warwick, Grantová Agentura České Republiky, Swedish National Space Agency, Vetenskapsrådet, Ministerstwo Edukacji i Nauki, Ministerio de Ciencia e Innovación, Japan Society for the Promotion of Science
Openalex Percentile: Top 27%
Stellar, planetary, and galactic studies
0.66
DOIOpen Access PDFOpenAlex
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