The McDonald Accelerating Stars Survey (MASS): Discovery of a Long-period Substellar Companion Orbiting the Old Solar Analog HD 47127
Abstract
Brown dwarfs with well-determined ages, luminosities, and masses provide rare but valuable tests of low-temperature atmospheric and evolutionary models. We present the discovery and dynamical mass measurement of a substellar companion to HD 47127, an old (≈7-10 Gyr) G5 main-sequence star with a mass similar to the Sun. Radial velocities of the host star with the Harlan J. Smith Telescope uncovered a low-amplitude acceleration of 1.93 ± 0.08 m s-1 yr-1 based on 20 years of monitoring. We subsequently recovered a faint (ΔH = 13.14 ± 0.15 mag) comoving companion at 1"95 (52 au) with follow-up Keck/NIRC2 adaptive optics imaging. The radial acceleration of HD 47127 together with its tangential acceleration from Hipparcos and Gaia EDR3 astrometry provide a direct measurement of the three-dimensional acceleration vector of the host star, enabling a dynamical mass constraint for HD 47127 B (67.5-177 MJup at 95% confidence) despite the small fractional orbital coverage of the observations. The absolute H-band magnitude of HD 47127 B is fainter than the benchmark T dwarfs HD 19467 B and Gl 229 B but brighter than Gl 758 B and HD 4113 C, suggesting a late-T spectral type. Altogether the mass limits for HD 47127 B from its dynamical mass and the substellar boundary imply a range of 67-78 MJup assuming it is single, although a preference for high masses of ≈100 MJup from dynamical constraints hints at the possibility that HD 47127 B could itself be a binary pair of brown dwarfs or that another massive companion resides closer in. Regardless, HD 47127 B will be an excellent target for more refined orbital and atmospheric characterization in the future.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 2021
- DOI:
- arXiv:
- arXiv:2105.01255
- Bibcode:
- 2021ApJ...913L..26B
- Keywords:
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- Brown dwarfs;
- T dwarfs;
- Companion stars;
- Substellar companion stars;
- 185;
- 1679;
- 291;
- 1648;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- Accepted to ApJ Letters