Herschel/SPIRE observations of the TWA brown dwarf disc 2MASSW J1207334−393254


Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

E-mail: b.riaz@herts.ac.uk


We present Herschel/SPIRE observations for the 2MASS 1207334−393254 (2M1207) system. Based on radiative transfer modelling of near-infrared to submillimetre data, we estimate a disc mass of 3 ± 2 MJup and an outer disc radius of 50–100 au for the 2M1207A disc. The relative disc mass for 2M1207A is similar to the T Tauri star TW Hya, which indicates that massive discs are not underabundant around substellar objects. In probing the various formation mechanisms for this system, we find that core accretion is highly uncertain mainly due to the large separation between the primary and the companion. Disc fragmentation could be a likely scenario based on analytical models, and if the disc initially was more massive than its current estimate. Considering that the TW Hydrae Association (TWA) is sparsely populated, this system could have formed via one of the known binary formation mechanisms (e.g. turbulent fragmentation of a core) and survived disruption at an early stage.