L-BAND SPECTROSCOPY WITH MAGELLAN-AO/Clio2: FIRST RESULTS ON YOUNG LOW-MASS COMPANIONS

• Main Authors: Stone, Jordan M., Eisner, Josh, Skemer, Andy, Morzinski, Katie M., Close, Laird, Males, Jared, Rodigas, Timothy J., Hinz, Phil, Puglisi, Alfio
• Other Authors: Univ Arizona, Steward Observ
• Language: en
• Published: IOP PUBLISHING LTD 2016
• Subjects: binaries: close; stars: atmospheres; stars: low-mass
• Online Access: http://hdl.handle.net/10150/621975; http://arizona.openrepository.com/arizona/handle/10150/621975

L-band spectroscopy is a powerful probe of cool low-gravity atmospheres: the P, Q, and R branch fundamental transitions of methane near 3.3 mu m provide a sensitive probe of carbon chemistry; cloud thickness modifies the spectral slope across the band; and H-3(+) opacity can be used to detect aurorae. Many directly imaged gas-giant companions to nearby young stars exhibit L-band fluxes distinct from the field population of brown dwarfs at the same effective temperature. Here we describe commissioning the L-band spectroscopic mode of Clio2, the 1-5 mu m instrument behind the Magellan adaptive-optics system. We use this system to measure L-band spectra of directly imaged companions. Our spectra are generally consistent with the parameters derived from previous near-infrared spectra for these late M to early L type objects. Therefore, deviations from the field sequence are constrained to occur below 1500 K. This range includes the L-T transition for field objects and suggests that observed discrepancies are due to differences in cloud structure and CO/CH4 chemistry.