The Astronomical Journal (Jan 2024)
Direct-imaging Discovery of a Substellar Companion Orbiting the Accelerating Variable Star HIP 39017
- Taylor L. Tobin,
- Thayne Currie,
- Yiting Li,
- Jeffrey Chilcote,
- Timothy D. Brandt,
- Brianna Lacy,
- Masayuki Kuzuhara,
- Maria Vincent,
- Mona El Morsy,
- Vincent Deo,
- Jonathan P. Williams,
- Olivier Guyon,
- Julien Lozi,
- Sebastien Vievard,
- Nour Skaf,
- Kyohoon Ahn,
- Tyler Groff,
- N. Jeremy Kasdin,
- Taichi Uyama,
- Motohide Tamura,
- Aidan Gibbs,
- Briley L. Lewis,
- Rachel Bowens-Rubin,
- Maïssa Salama,
- Qier An,
- Minghan Chen
Affiliations
- Taylor L. Tobin
- ORCiD
- Department of Astronomy, University of Michigan , 1085 S. University, Ann Arbor, MI 48109, USA ; [email protected]; Department of Physics and Astronomy, University of Notre Dame , Nieuwland Science Hall, Notre Dame, IN 46556, USA
- Thayne Currie
- ORCiD
- Subaru Telescope, National Astronomical Observatory of Japan , 650 North A‘ohōkū Place, Hilo, HI 96720, USA; Department of Physics and Astronomy, University of Texas at San Antonio , San Antonio, TX 78249, USA
- Yiting Li
- ORCiD
- Department of Astronomy, University of Michigan , 1085 S. University, Ann Arbor, MI 48109, USA ; [email protected]; Department of Physics, University of California, Santa Barbara, CA 93106-9530, USA
- Jeffrey Chilcote
- ORCiD
- Department of Physics and Astronomy, University of Notre Dame , Nieuwland Science Hall, Notre Dame, IN 46556, USA
- Timothy D. Brandt
- ORCiD
- Department of Physics, University of California, Santa Barbara, CA 93106-9530, USA
- Brianna Lacy
- ORCiD
- Department of Astronomy & Astrophysics, University of California , Santa Cruz, CA 95064, USA
- Masayuki Kuzuhara
- ORCiD
- Astrobiology Center , NINS, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; National Astronomical Observatory of Japan , 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
- Maria Vincent
- ORCiD
- Institute for Astronomy, University of Hawai’i at Mānoa , 2680 Woodlawn Drive, Honolulu, HI 96822, USA
- Mona El Morsy
- ORCiD
- Department of Physics and Astronomy, University of Texas at San Antonio , San Antonio, TX 78249, USA
- Vincent Deo
- ORCiD
- Subaru Telescope, National Astronomical Observatory of Japan , 650 North A‘ohōkū Place, Hilo, HI 96720, USA
- Jonathan P. Williams
- ORCiD
- Institute for Astronomy, University of Hawai’i at Mānoa , 2680 Woodlawn Drive, Honolulu, HI 96822, USA
- Olivier Guyon
- ORCiD
- Subaru Telescope, National Astronomical Observatory of Japan , 650 North A‘ohōkū Place, Hilo, HI 96720, USA
- Julien Lozi
- ORCiD
- Subaru Telescope, National Astronomical Observatory of Japan , 650 North A‘ohōkū Place, Hilo, HI 96720, USA
- Sebastien Vievard
- ORCiD
- Subaru Telescope, National Astronomical Observatory of Japan , 650 North A‘ohōkū Place, Hilo, HI 96720, USA
- Nour Skaf
- ORCiD
- Department of Astronomy & Astrophysics, University of California , Santa Cruz, CA 95064, USA
- Kyohoon Ahn
- ORCiD
- Subaru Telescope, National Astronomical Observatory of Japan , 650 North A‘ohōkū Place, Hilo, HI 96720, USA
- Tyler Groff
- ORCiD
- NASA Goddard Space Flight Center , Greenbelt, MD 20770, USA
- N. Jeremy Kasdin
- ORCiD
- Department of Mechanical Engineering, Princeton University , Princeton, NJ 08544, USA
- Taichi Uyama
- ORCiD
- Department of Physics and Astronomy, California State University, Northridge , Northridge, CA 91330 USA
- Motohide Tamura
- ORCiD
- Astrobiology Center , NINS, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; National Astronomical Observatory of Japan , 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; Department of Astronomy, Graduate School of Science, The University of Tokyo , 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
- Aidan Gibbs
- ORCiD
- Department of Physics & Astronomy, University of California , Los Angeles, CA 90095, USA
- Briley L. Lewis
- ORCiD
- Department of Physics & Astronomy, University of California , Los Angeles, CA 90095, USA
- Rachel Bowens-Rubin
- ORCiD
- Department of Astronomy & Astrophysics, University of California , Santa Cruz, CA 95064, USA
- Maïssa Salama
- ORCiD
- Department of Astronomy & Astrophysics, University of California , Santa Cruz, CA 95064, USA
- Qier An
- ORCiD
- Department of Physics, University of California, Santa Barbara, CA 93106-9530, USA
- Minghan Chen
- ORCiD
- Department of Physics, University of California, Santa Barbara, CA 93106-9530, USA
- DOI
- https://doi.org/10.3847/1538-3881/ad3077
- Journal volume & issue
-
Vol. 167,
no. 5
p. 205
Abstract
We present the direct-imaging discovery of a substellar companion (a massive planet or low-mass brown dwarf) to the young, γ Doradus ( γ Dor)-type variable star HIP 39017 (HD 65526). The companion’s SCExAO/CHARIS JHK (1.1–2.4 μ m) spectrum and Keck/NIRC2 $L^{\prime} $ photometry indicate that it is an L/T transition object. A comparison of the JHK + L $^{\prime} $ spectrum to several atmospheric model grids finds a significantly better fit to cloudy models than cloudless models. Orbit modeling with relative astrometry and precision stellar astrometry from Hipparcos and Gaia yields a semimajor axis of ${23.8}_{-6.1}^{+8.7}$ au, a dynamical companion mass of ${30}_{-12}^{+31}$ M _J , and a mass ratio of ∼1.9%, properties most consistent with low-mass brown dwarfs. However, its mass estimated from luminosity models is a lower ∼13.8 M _J due to an estimated young age (≲115 Myr); using a weighted posterior distribution informed by conservative mass constraints from luminosity evolutionary models yields a lower dynamical mass of ${23.6}_{-7.4}^{+9.1}$ M _J and a mass ratio of ∼1.4%. Analysis of the host star’s multifrequency γ Dor-type pulsations, astrometric monitoring of HIP 39017 b, and Gaia Data Release 4 astrometry of the star will clarify the system age and better constrain the mass and orbit of the companion. This discovery further reinforces the improved efficiency of targeted direct-imaging campaigns informed by long-baseline, precision stellar astrometry.
Keywords
