2007/09/04 by Eric E. Mamajek, Michael R. Meyer · 1 citation
Physics and Astronomy · #Astro and Planetary Science #Astrophysics and Star Formation Studies #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/522957
ApJ Letters, in press (11 pages)
arxiv created 2007/09/04 · openalex publication_date 2007/10/04 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
We introduce an alternative hypothesis to explain the very low luminosity of the cool (L-type) companion to the ~25 MJup ~8 Myr-old brown dwarf 2M1207A. Recently, Mohanty et al. (2007) found that effective temperature estimates for 2M1207B (1600 +- 100 K) are grossly inconsistent with its lying on the same isochrone as the primary, being a factor of ~10 underluminous at all bands between I (0.8 um) and L' (3.6 um). Mohanty et al. explain this discrepency by suggesting that 2M1207B is an 8 MJup object surrounded by an edge-on disk comprised of large dust grains producing 2.5m of achromatic extinction. We offer an alternative explanation: the apparent flux reflects the actual source luminosity. Given the temperature, we infer a small radius (~49,000 km), and for a range of plausible densities, we estimate a mass < MJup. We suggest that 2M1207B is a hot protoplanet collision afterglow and show that the radiative timescale for such an object is >~1% the age of the system. If our hypothesis is correct, the surface gravity of 2M1207B should be an order of magnitude lower than predicted by Mohanty et al. (2007).