TOI-7154b: A Close-in Massive Brown Dwarf in an Eccentric Orbit
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2026
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| author | Das, Rohan Ch. Dwivedi, Churchil Sharma, Rishikesh Bhaskar, Hareesh G. Nikitha, K. J. Bieryla, Allyson Safonov, Boris S. Das, Shubhendra N. Chakraborty, Abhijit Zadeng, Lalthakimi Latham, David W. Prasad, Neelam J. S. S. V. Bharadwaj, Kapil K. Lad, Kevikumar A. Nayak, Ashirbad |
| author_facet | Das, Rohan Ch. Dwivedi, Churchil Sharma, Rishikesh Bhaskar, Hareesh G. Nikitha, K. J. Bieryla, Allyson Safonov, Boris S. Das, Shubhendra N. Chakraborty, Abhijit Zadeng, Lalthakimi Latham, David W. Prasad, Neelam J. S. S. V. Bharadwaj, Kapil K. Lad, Kevikumar A. Nayak, Ashirbad |
| contents | We report here the discovery and characterization of a high-mass transiting brown dwarf in a close-in orbit around its host star, TOI-7154. Initially, the host star was identified as an exoplanetary candidate from the TESS photometry data. Later, with the mass measurements from the RV follow-up using the PARAS-2 and TRES spectrographs, the companion is found to be sub-stellar in nature. TOI-7154, is a G-type main-sequence metal-rich star metallicity $\mathrm{[Fe/H]} = 0.154^{+0.077}_{-0.075}\,\text{dex}$, effective temperature $T_{\mathrm{eff}} = 5564^{+100}_{-110}\,\text{K}$, mass $M_\star = 0.939^{+0.047}_{-0.043}\,M_{\odot}$, radius $R_\star = 0.949^{+0.032}_{-0.030}\,R_{\odot}$, and surface gravity $\log g = 4.456^{+0.036}_{-0.036}$. With the joint analysis of the TESS photometry and the PARAS-2 and TRES radial velocities we found that TOI-7154b orbits its host star in $P = 8.860073\pm 0.000029\,\text{d}$, eccentric ($e = 0.2482 \pm 0.0024$) orbit and its radius is smaller than that of Jupiter ($R_{b} = 0.827^{+0.040}_{-0.037}\,R_{\mathrm{J}}$). With a mass near the hydrogen-burning boundary ($M_{b} = 71.7^{+2.4}_{-2.2}\,M_{\mathrm{J}}$) which separates brown dwarfs from very low-mass stars, TOI-7154b occupies a critical position in the regime for probing the transition between sub-stellar and stellar objects. The system is very old, with its age estimated to be $7.2^{+3.9}_{-3.6}\,\text{Gyr}$ by MIST isochrones, while Galactic kinematics indicate an age of $\sim4-5\,\text{Gyr}$. {Our tidal evolution simulations indicate a stellar dissipation factor of $Q_\star'\lesssim10^6$. Since the presence of any companion is currently ruled out by observations, the presence of eccentricity in this old system is, therefore, indicative of it having stellar-like fragmentation origins. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_23469 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | TOI-7154b: A Close-in Massive Brown Dwarf in an Eccentric Orbit Das, Rohan Ch. Dwivedi, Churchil Sharma, Rishikesh Bhaskar, Hareesh G. Nikitha, K. J. Bieryla, Allyson Safonov, Boris S. Das, Shubhendra N. Chakraborty, Abhijit Zadeng, Lalthakimi Latham, David W. Prasad, Neelam J. S. S. V. Bharadwaj, Kapil K. Lad, Kevikumar A. Nayak, Ashirbad Earth and Planetary Astrophysics Solar and Stellar Astrophysics We report here the discovery and characterization of a high-mass transiting brown dwarf in a close-in orbit around its host star, TOI-7154. Initially, the host star was identified as an exoplanetary candidate from the TESS photometry data. Later, with the mass measurements from the RV follow-up using the PARAS-2 and TRES spectrographs, the companion is found to be sub-stellar in nature. TOI-7154, is a G-type main-sequence metal-rich star metallicity $\mathrm{[Fe/H]} = 0.154^{+0.077}_{-0.075}\,\text{dex}$, effective temperature $T_{\mathrm{eff}} = 5564^{+100}_{-110}\,\text{K}$, mass $M_\star = 0.939^{+0.047}_{-0.043}\,M_{\odot}$, radius $R_\star = 0.949^{+0.032}_{-0.030}\,R_{\odot}$, and surface gravity $\log g = 4.456^{+0.036}_{-0.036}$. With the joint analysis of the TESS photometry and the PARAS-2 and TRES radial velocities we found that TOI-7154b orbits its host star in $P = 8.860073\pm 0.000029\,\text{d}$, eccentric ($e = 0.2482 \pm 0.0024$) orbit and its radius is smaller than that of Jupiter ($R_{b} = 0.827^{+0.040}_{-0.037}\,R_{\mathrm{J}}$). With a mass near the hydrogen-burning boundary ($M_{b} = 71.7^{+2.4}_{-2.2}\,M_{\mathrm{J}}$) which separates brown dwarfs from very low-mass stars, TOI-7154b occupies a critical position in the regime for probing the transition between sub-stellar and stellar objects. The system is very old, with its age estimated to be $7.2^{+3.9}_{-3.6}\,\text{Gyr}$ by MIST isochrones, while Galactic kinematics indicate an age of $\sim4-5\,\text{Gyr}$. {Our tidal evolution simulations indicate a stellar dissipation factor of $Q_\star'\lesssim10^6$. Since the presence of any companion is currently ruled out by observations, the presence of eccentricity in this old system is, therefore, indicative of it having stellar-like fragmentation origins. |
| title | TOI-7154b: A Close-in Massive Brown Dwarf in an Eccentric Orbit |
| topic | Earth and Planetary Astrophysics Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2605.23469 |