Time-resolved High Spectral Resolution Observation of 2MASSW J0746425+200032AB

Creators: Wang, Ji; Prato, Lisa; Mawet, Dimitri

Abstract

Many brown dwarfs (BDs) exhibit photometric variability at levels from tenths to tens of percents. The photometric variability is related to magnetic activity or patchy cloud coverage, characteristic of BDs near the L–T transition. Time-resolved spectral monitoring of BDs provides diagnostics of cloud distribution and condensate properties. However, current time-resolved spectral studies of BDs are limited to low spectral resolution (R ~ 100) with the exception of the study of Luhman 16 AB at a resolution of 100,000 using the VLT+CRIRES. This work yielded the first map of BD surface inhomogeneity, highlighting the importance and unique contribution of high spectral resolution observations. Here, we report on the time-resolved high spectral resolution observations of a nearby BD binary, 2MASSW J0746425+200032AB. We find no coherent spectral variability that is modulated with rotation. Based on simulations, we conclude that the coverage of a single spot on 2MASSW J0746425+200032AB is smaller than 1% or 6.25% if spot contrast is 50% or 80% of its surrounding flux, respectively. Future high spectral resolution observations aided by adaptive optics systems can put tighter constraints on the spectral variability of 2MASSW J0746425+200032AB and other nearby BDs.

Additional Information

© 2017 The American Astronomical Society. Received 2017 January 25; revised 2017 February 23; accepted 2017 February 24; published 2017 March 21. We would like to thank Ian Crossfield for sharing the VLT CRIRES data for Luhman 16 AB and for constructive discussions on BD spectral variability and Doppoler imaging. We would also like to thank Courtney Dressing for her suggestion of binning CRIRES data to investigate the impact of reduced spectral resolution on Keck NIRSPEC data. The authors would like to acknowledge the financial support of the Heising-Simons foundation. The data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Facility: Keck:II (NIRSPEC).

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Published - Wang_2017_ApJ_838_35.pdf

Submitted - 1702.07769.pdf

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