- The paper presents an astrometric study of the Luhman 16AB binary brown dwarf system using VLT/FORS2 data, which refined its distance to 2.020 ± 0.019 parsecs.
- Astrometric analysis revealed perturbations in the binary's motion, strongly suggesting the presence of a substellar companion with a mass potentially between a few and 30 Jupiter masses.
- This potential discovery highlights the capability of ground-based astrometry for finding companions to nearby brown dwarfs and warrants further observations to confirm and characterize the object.
Astrometric Discovery of a Substellar Companion to WISE J104915.57-531906.1
The paper presents an astrometric paper conducted using the FORS2 instrument on the Very Large Telescope, focusing on the closest binary brown dwarf system known as WISE J104915.57-531906.1, or Luhman 16AB. Through detailed astrometric monitoring over a two-month period, the authors have made precise measurements of the binary's orbital motion and parallax, leading to a more accurate determination of its distance at 2.020 ± 0.019 parsecs. Notably, the astrometric data reveals perturbations in the relative orbital motion of the binary components, suggesting the presence of a substellar companion around one of them.
Methods and Observations
The astrometric monitoring utilized FORS2 with high spatial resolution, achieving relative precision at the milli-arcsecond scale. Over the course of 12 observational epochs, the team gathered data that allowed them to detect not only the orbital motion but also an anomaly suggesting gravitational perturbation. The astrometric data were combined with existing archival data spanning 23 years, refining the parameters such as parallax and proper motion.
Photometric observations in the VRIz bands were conducted, confirming a flux reversal in the T dwarf, a phenomenon consistent with previous findings. The photometric data were also cross-referenced with theoretical models, yielding insights into the system's composition and age. The spectral types of the brown dwarfs were affirmed as L8 and T1, with observational magnitudes supporting the existing theoretical frameworks.
Astrometric Analysis and Implications
Two primary models were employed for astrometric analysis. Firstly, a comprehensive two-body orbital model described the motion of the two brown dwarfs around their barycentre. Additionally, a quadratic approximation was utilized to fit the short-term orbital data, allowing for a simplified representation that still accounted for the observed perturbations. The latter model indicated residuals that correlated highly, positing that a substellar companion, perhaps a planetary-mass object, induces this perturbation.
The detected perturbations suggest a companion with a mass possibly between a few and 30 Jupiter masses. The companion's influence on the system suggests it may significantly affect the orbital dynamics given its proximity, warranting further observational efforts to characterize it fully.
Future Directions and Conclusions
The paper's findings imply substantial advancements in the paper of substellar companions to brown dwarfs, indicating that such systems may host companions even at close distances. Confirming the presence of a substellar companion around Luhman 16AB would represent a significant addition to the sparse set of known exoplanets around brown dwarfs. Future high-precision radial velocity measurements and adaptive optics imaging could help characterize the companion further, providing insights into its mass and orbital characteristics.
In summary, the astrometric and photometric techniques demonstrated in this paper showcase the potential of ground-based telescopes in contributing to our understanding of nearby systems and their potential for harboring substellar companions. The implications for the formation and evolutionary modeling of brown dwarfs and their companions are profound, potentially challenging existing paradigms about substellar system dynamics.