Cloud Atlas: Rotational Modulations in the L/T Transition Brown Dwarf Companion HN Peg B
Abstract
Time-resolved observations of brown dwarfs' rotational modulations provide powerful insights into the properties of condensate clouds in ultra-cool atmospheres. Multi-wavelength light curves reveal cloud vertical structures, condensate particle sizes, and cloud morphology, which directly constrain condensate cloud and atmospheric circulation models. We report results from Hubble Space Telescope/Wide Field Camera 3 near-infrared G141 taken in six consecutive orbits observations of HN Peg B, an L/T transition brown dwarf companion to a G0V type star. The best-fit sine wave to the 1.1–1.7 μm broadband light curve has an amplitude of 1.206% ± 0.025% and period of 15.4 ± 0.5 hr. The modulation amplitude has no detectable wavelength dependence except in the 1.4 μm water absorption band, indicating that the characteristic condensate particle sizes are large (>1 μm). We detect significantly (4.4σ) lower modulation amplitude in the 1.4 μm water absorption band and find that HN Peg B's spectral modulation resembles those of early T type brown dwarfs. We also describe a new empirical interpolation method to remove spectral contamination from the bright host star. This method may be applied in other high-contrast time-resolved observations with WFC3.
Additional Information
© 2018 American Astronomical Society. Received 2017 November 6. Accepted 2018 January 25. Published 2018 February 28. We acknowledge the anonymous referee for a constructive report that improves the manuscript. We acknowledge Dr. Sandy Leggett for valuable discussion on HN Peg B's spectral fitting and Dr. Peter McCullough for helpful discussion on the cause of the image contamination. Y.Z. acknowledges support in part by the NASA Earth and Space Science Fellowship Program—grant "NNX16AP54H." D.A. acknowledges support by NASA under agreement No. NNX15AD94G for the program Earths in Other Solar Systems. Support for Program number 14241 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained in GO program 14241 at the Space Telescope Science Institute.Attached Files
Published - Zhou_2018_AJ_155_132.pdf
Accepted Version - 1801.09757.pdf
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Additional details
- Eprint ID
- 85012
- Resolver ID
- CaltechAUTHORS:20180228-131454852
- NNX16AP54H
- NASA Earth and Space Science Fellowship
- NNX15AD94G
- NASA
- NAS5-26555
- NASA
- Created
-
2018-02-28Created from EPrint's datestamp field
- Updated
-
2021-11-15Created from EPrint's last_modified field
- Caltech groups
- Infrared Processing and Analysis Center (IPAC)