New Extinction and Mass Estimates of the Low-mass Companion 1RXS 1609 B with the Magellan AO System: Evidence of an Inclined Dust Disk

We used the Magellan adaptive optics system to image the 11 Myr substellar companion 1RXS 1609 B at the bluest wavelengths to date (z' and Y-s). Comparison with synthetic spectra yields a higher temperature than previous studies of T-eff = 2000 +/- 100 K and significant dust extinction of A(V) = 4.5(-0.7)(+0.5) mag. Mass estimates based on the DUSTY tracks gives 0.012-0.015 M-circle dot, making the companion likely a low-mass brown dwarf surrounded by a dusty disk. Our study suggests that 1RXS 1609 B is one of the similar to 25% of Upper Scorpius low-mass members harboring disks, and it may have formed like a star and not a planet out at similar to 320 AU.