Clouds On A Cold Planet: FIRE Spectroscopy Of Ross 458C
Abstract
Ross 458C is a widely-separated (1100 AU), faint companion to the nearby M0.5 Ve + M7 Ross 458AB binary, identified in the UKIDSS survey by Goldman et al. and Scholz and suspected by both of being a young brown dwarf. We obtained near-infrared spectroscopy of this source with the newly-commissioned Folded-Port Infrared Echellette (FIRE) at the Magellan Telescopes, which revealed the presence of strong methane and water absorption consistent with a T8 dwarf. The age of this system (150-800 Myr) and the low luminosity of the companion (log Lbol/Lsun = -5.62±0.03) indicate a mass at or below the deuterium burning limit. This is verified through atmospheric model fits to the spectral data, which indicate a low temperature (635 [+25,-35] K), a low surface gravity (log g 4 cgs) and a model-dependent mass of <=6 Jupiter masses. The spectral models further indicate that condensate clouds are present in the atmosphere of Ross 458C, in contrast to results for other cold T dwarfs. These results provide further evidence that clouds are an important opacity source in the spectra of young substellar objects, from planetary-mass brown dwarfs in young clusters to directly-imaged exoplanets. Moreover, its low mass, cool atmosphere and physical association with a stellar system give Ross 458C all of the trappings of a planet, albeit one whose cosmogony may not conform with current planet formation theories.
This result includes data gathered with the 6.5-m Magellan Telescopes located at Las Campanas Observatory, Chile. Support for the modeling work of D.S. was provided by NASA through the Spitzer Science Center.- Publication:
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American Astronomical Society Meeting Abstracts #217
- Pub Date:
- January 2011
- Bibcode:
- 2011AAS...21734314B