CASSA Colloquium 12: Between Stars and Planets

Title: Between Stars and Planets: Unveiling the Hidden World of Transiting Brown Dwarfs

Speaker: Md Redyan Ahmed, PhD candidate, Sydney Institute for Astronomy (SIfA), University of Sydney, Australia.

Abstract

Transiting brown dwarfs occupy the mass range between stars and planets, placing them in a unique regime where the physics of both worlds begin to overlap. Wide-field surveys have identified more than 1,000 isolated brown dwarfs in the Solar neighbourhood, yet only about 50 systems are known to transit their host stars. With the arrival of the TESS mission, this picture has begun to change: the sample of transiting brown dwarfs is growing steadily, providing more systems with precisely measured masses and radii and opening new opportunities to study how these objects form and evolve. In this talk, I will give a short introduction to transiting brown dwarfs, how they are detected, and how their known population has been expanding over time. I will then present TOI-2155 b, a newly characterised transiting brown dwarf lying right at the hydrogen-burning mass limit. With a mass of 81 (Jupiter mass), it contributes an important new data point to the growing population of transiting brown dwarfs and helps us probe the structure, cooling, and formation pathways of objects near the low-mass star boundary.