TOI-6884b: A low-mass brown dwarf transiting a slightly evolved star

Abstract We report the discovery of a low-mass transiting brown dwarf orbiting TOI-6884 (TIC 156514476, Tmag = 11.4) from NASA’s Transiting Exoplanet Survey Satellite (TESS) mission. The TESS light curves initially suggested an orbital period of ~14.42 days; however, our high-precision ground-based radial velocity measurements and multi-epoch time-series photometry reveal this to be a harmonic alias. We determine the true orbital period to be $4.808264^{+0.000015}_{-0.000014}$ days and confirm the substellar nature of the companion. TOI-6884b has a mass of $26.32^{+0.98}_{-0.93}M_{\rm J}$, a radius of $0.927^{+0.51}_{-0.52} R_{\rm J}$, and resides on a nearly circular orbit ($e=0.067^{+0.010}_{-0.012}$). Its host star is a late F-type slightly evolved star with $M_\star = 1.410^{+0.075}_{-0.069} M_\odot$, $R_\star = 1.840^{+0.072}_{-0.073} R_\odot$, $\log {g} = 4.057^{+0.045}_{-0.039}$, $[{\rm Fe/H}] = 0.094^{+0.073}_{-0.068}$ dex, and $T_{\rm eff}=6330^{+180}_{-160}$ K. TOI-6884b is a key addition to the small population of well-characterized transiting brown dwarfs orbiting host stars that have left the main sequence. The detection of such systems will contribute to our understanding of dynamical histories and structural evolution of short-period substellar companions around evolved stars.

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Journal
Monthly Notices of the Royal Astronomical Society
Published
2026-05-29
DOI
https://doi.org/10.1093/mnras/stag988
Primary Topic
Stellar, planetary, and galactic studies
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article
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article

TOI-6884b: A low-mass brown dwarf transiting a slightly evolved star

Noriharu Watanabe, Bob Massey, F. Murgas, A. Chakraborty et al.
Monthly Notices of the Royal Astronomical Society
Stellar, planetary, and galactic studies
article

TOI-6884b: A low-mass brown dwarf transiting a slightly evolved star

Noriharu Watanabe, Bob Massey, F. Murgas, A. Chakraborty, Manuel Pichardo Marcano, Rishikesh Sharma, Howard M. Relles, Akanksha Khandelwal, Sanjay Baliwal, Mark E. Everett, Catherine A. Clark, Jason D. Eastman, C. Dwivedi, Ashirbad Nayak, Santiago Paez, Polina A. Budnikova, Nikitha Jithendran, Sam Quinn, Kapil Bharadwaj, Gregor Srdoč, Shubhendra Nath Das, I Bonilla-Mariana, I Fukuda, Jerome de Leon, Toshi Suganuma, S B Howell, Richard P Schwarz, Boris Safonov, Kendra Nguyen, Cristilyn N Watkins, Karen A Collins, Enric Pallé, David W Latham, Allyson Bieryla, Jesus Higuera, Norio Narita, Florence Libotte, David Ciardi, Keith Horne, Francis P Wilkin, Neelam JSSV Prasad, Micaela Magno, Kevikumar Lad, Akihiko Fukui, Y Gómez Maqueo Chew
article en

Abstract

Abstract We report the discovery of a low-mass transiting brown dwarf orbiting TOI-6884 (TIC 156514476, Tmag = 11.4) from NASA’s Transiting Exoplanet Survey Satellite (TESS) mission. The TESS light curves initially suggested an orbital period of ~14.42 days; however, our high-precision ground-based radial velocity measurements and multi-epoch time-series photometry reveal this to be a harmonic alias. We determine the true orbital period to be $4.808264^{+0.000015}_{-0.000014}$ days and confirm the substellar nature of the companion. TOI-6884b has a mass of $26.32^{+0.98}_{-0.93}M_{\rm J}$, a radius of $0.927^{+0.51}_{-0.52} R_{\rm J}$, and resides on a nearly circular orbit ($e=0.067^{+0.010}_{-0.012}$). Its host star is a late F-type slightly evolved star with $M_\star = 1.410^{+0.075}_{-0.069} M_\odot$, $R_\star = 1.840^{+0.072}_{-0.073} R_\odot$, $\log {g} = 4.057^{+0.045}_{-0.039}$, $[{\rm Fe/H}] = 0.094^{+0.073}_{-0.068}$ dex, and $T_{\rm eff}=6330^{+180}_{-160}$ K. TOI-6884b is a key addition to the small population of well-characterized transiting brown dwarfs orbiting host stars that have left the main sequence. The detection of such systems will contribute to our understanding of dynamical histories and structural evolution of short-period substellar companions around evolved stars.

Monthly Notices of the Royal Astronomical Society
Andrews University (US), Physical Research Laboratory (IN), Ames Research Center (US), Universidad de La Laguna (ES), Universidad Autónoma de la Ciudad de México (MX), University of St Andrews (GB), Union College (US), Indian Institute of Technology Gandhinagar (IN), NASA Exoplanet Science Institute (US), Pulkovo Observatory (RU), Yale University (US), TMT Observatory (US), Astrobiology Center (JP), Center for Astrophysics Harvard & Smithsonian (US), Hospital de Sabadell (ES), Instituto de Astrofísica de Canarias (ES), Astronomical Institute of the Slovak Academy of Sciences (SK), NSF NOIRLab (US), Tokyo Metropolitan Komaba High School (JP), Moscow State University (TJ), The University of Tokyo (JP), Universidad Nacional Autónoma de México (MX)
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Stellar, planetary, and galactic studies
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