학술논문
Direct-imaging Discovery of a Substellar Companion Orbiting the Accelerating Variable Star, HIP 39017
Document Type
Working Paper
Author
Tobin, Taylor L.; Currie, Thayne; Li, Yiting; Chilcote, Jeffrey; Brandt, Timothy D.; Lacy, Brianna; Kuzuhara, Masayuki; Vincent, Maria; Morsy, Mona El; Deo, Vincent; Williams, Jonathan P.; Guyon, Olivier; Lozi, Julien; Vievard, Sebastien; Skaf, Nour; Ahn, Kyohoon; Groff, Tyler; Kasdin, N. Jeremy; Uyama, Taichi; Tamura, Motohide; Gibbs, Aidan; Lewis, Briley L.; Bowens-Rubin, Rachel; Salama, Maïssa; An, Qier; Chen, Minghan
Source
2024, AJ, 167, 205
Subject
Language
Abstract
We present the direct-imaging discovery of a substellar companion (a massive planet or low-mass brown dwarf) to the young, $\gamma$ Doradus-type variable star, HIP 39017 (HD 65526). The companion's SCExAO/CHARIS JHK ($1.1-2.4\mu$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 semi-major axis of $23.8^{+8.7}_{-6.1}$ au, a dynamical companion mass of $30^{+31}_{-12}$~M$_J$, and a mass ratio of $\sim$1.9\%, properties most consistent with low-mass brown dwarfs. However, its mass estimated from luminosity models is a lower $\sim$13.8 $M_{\rm J}$ due to an estimated young age ($\lesssim$ 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 $\sim$1.4\%. Analysis of the host star's multi-frequency $\gamma$ Dor-type pulsations, astrometric monitoring of HIP 39017b, 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.
Comment: Published in AJ: April 9, 2024
Comment: Published in AJ: April 9, 2024