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

Abstract

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<SUB>s</SUB>). Comparison with synthetic spectra yields a higher temperature than previous studies of {T}<SUB>{eff</SUB>}=2000+/- 100 {{K}} and significant dust extinction of {A}<SUB>V</SUB>={4.5}<SUB>-0.7</SUB><SUP>+0.5</SUP> mag. Mass estimates based on the DUSTY tracks gives 0.012-0.015 {M}<SUB>☉ </SUB>, 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 ̃25% of Upper Scorpius low-mass members harboring disks, and it may have formed like a star and not a planet out at ̃320 AU. <P />This paper includes data gathered with the 6.5 m Magellan Clay Telescope at Las Campanas Observatory, Chile.