Author ORCID Identifier
Kimberly Ward-Duong: 0000-0002-4479-8291
Document Type
Article
Publication Date
10-1-2023
Publication Title
Astrophysical Journal
Abstract
Tension remains between the observed and modeled properties of substellar objects, but objects in binary orbits, with known dynamical masses, can provide a way forward. HD 72946 B is a recently imaged brown dwarf companion to a nearby, solar-type star. We achieve ∼100 μas relative astrometry of HD 72946 B in the K band using VLTI/GRAVITY, unprecedented for a benchmark brown dwarf. We fit an ensemble of measurements of the orbit using orbitize! and derive a strong dynamical mass constraint M B = 69.5 ± 0.5 M Jup assuming a strong prior on the host star mass M A = 0.97 ± 0.01 M ⊙ from an updated stellar analysis. We fit the spectrum of the companion to a grid of self-consistent BT-Settl-CIFIST model atmospheres, and perform atmospheric retrievals using petitRADTRANS. A dynamical mass prior only marginally influences the sampled distribution of effective temperature, but has a large influence on the surface gravity and radius, as expected. The dynamical mass alone does not strongly influence retrieved pressure-temperature or cloud parameters within our current retrieval setup. Independently of the cloud prescription and prior assumptions, we find agreement within ±2σ between the C/O of the host (0.52 ± 0.05) and brown dwarf (0.43-0.63), as expected from a molecular cloud collapse formation scenario, but our retrieved metallicities are implausibly high (0.6-0.8) in light of the excellent agreement of the data with the solar-abundance model grid. Future work on our retrieval framework will seek to resolve this tension. Additional study of low surface gravity objects is necessary to assess the influence of a dynamical mass prior on atmospheric analysis.
Volume
956
Issue
2
DOI
10.3847/1538-4357/acf761
ISSN
0004637X
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Rights
© 2023 The Authors
Recommended Citation
Balmer, William O.; Pueyo, Laurent; Stolker, Tomas; Reggiani, Henrique; Maire, A. L.; Lacour, S.; Mollière, P.; Nowak, M.; Sing, D.; Pourré, N.; Blunt, S.; Wang, J. J.; Rickman, E.; Kammerer, J.; Henning, Th; Ward-Duong, K.; Abuter, R.; Amorim, A.; Asensio-Torres, R.; Benisty, M.; Berger, J. P.; Beust, H.; Boccaletti, A.; Bohn, A.; Bonnefoy, M.; Bonnet, H.; Bourdarot, G.; Brandner, W.; Cantalloube, F.; Caselli, P.; Charnay, B.; and Chauvin, G., "VLTI/GRAVITY Observations and Characterization of the Brown Dwarf Companion HD 72946 B" (2023). Astronomy: Faculty Publications, Smith College, Northampton, MA.
https://scholarworks.smith.edu/ast_facpubs/148
Comments
Archived as published.