Maps of Evolving Cloud Structures in Luhman 16ab From HST Time-Resolved Spectroscopy

Karalidi, Theodora; Apai, Dániel; Marley, Mark S.; Buenzli, E.

doi:10.3847/0004-637x/825/2/90

Cited by 47 publications

(65 citation statements)

References 31 publications

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“…Modeling approaches that combine multiple 1D models (such as the one presented herein and Artigau et al 2009;Apai et al 2013;Karalidi et al 2015Karalidi et al , 2016 can reproduce correlated variability or 180°anticorrelated variability, but not other phase shifts. As demonstrated above, where the "top-ofatmosphere" occurs varies depending on wavelength and the specific opacity sources that dominate at different atmospheric levels.…”

Section: Theoretical Consideration Of Observed Amplitudes and Phase Smentioning

confidence: 95%

Simultaneous Multiwavelength Variability Characterization of the Free-floating Planetary-mass Object PSO J318.5−22

Biller

Vos

Buenzli

et al. 2018

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109

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We present simultaneous Hubble Space Telescope (HST) WFC3+Spitzer IRAC variability monitoring for the highly variable young (∼20 Myr) planetary-mass object PSO J318.5−22. Our simultaneous HST + Spitzer observations covered approximately two rotation periods with Spitzer and most of a rotation period with the HST. We derive a period of 8.6±0.1 hr from the Spitzer light curve. Combining this period with the measured v i sin for this object, we find an inclination of 56°.2±8°. 1. We measure peak-to-trough variability amplitudes of 3.4%±0.1% for Spitzer Channel 2 and 4.4%-5.8% (typical 68% confidence errors of ∼0.3%) in the near-IR bands (1.07-1.67 μm) covered by the WFC3 G141 prism-the mid-IR variability amplitude for PSO J318.5−22 is one of the highest variability amplitudes measured in the mid-IR for any brown dwarf or planetary-mass object. Additionally, we detect phase offsets ranging from 200°to 210°(typical error of ∼4°) between synthesized near-IR light curves and the Spitzer mid-IR light curve, likely indicating depth-dependent longitudinal atmospheric structure in this atmosphere. The detection of similar variability amplitudes in wide spectral bands relative to absorption features suggests that the driver of the variability may be inhomogeneous clouds (perhaps a patchy haze layer over thick clouds), as opposed to hot spots or compositional inhomogeneities at the top-of-atmosphere level.

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Section: Theoretical Consideration Of Observed Amplitudes and Phase Smentioning

confidence: 95%

Simultaneous Multiwavelength Variability Characterization of the Free-floating Planetary-mass Object PSO J318.5−22

Biller

Vos

Buenzli

et al. 2018

Self Cite

109

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“…The radiative-cloud-driven variability provides a theoretical foundation to understand the rapidly evolving light curves found for many L and T dwarfs (e.g., Artigau et al 2009;Metchev et al 2015;Apai et al 2017). These observations are difficult to explain by rotational modulation caused by temporally steady or slowly evolving surface inhomogeneity (Karalidi et al 2016), for example, phenomena analogous to the Great Red Spot or 5-µm hot spots in Jupiter's atmosphere. Light curves of many brown dwarfs can only be explained when the surface features evolve over timescales comparable to the rotation period.…”

Section: Implications For Observationsmentioning

confidence: 99%

“…The inhomogeneous brightness likely results from surface patchiness comprised of horizontally varying cloud and temperature structure (e.g., Radigan et al 2012;Apai et al 2013;Buenzli et al 2015;Karalidi et al 2016), but the mechanisms driving the surface patchiness and controlling its evolution remain elusive. Since clouds are tracers advected by atmospheric flows, and the clouds themselves result from dynamics, the patchiness also likely has a dynamical origin.…”

Section: Introductionmentioning

confidence: 99%

Atmospheric Variability Driven by Radiative Cloud Feedback in Brown Dwarfs and Directly Imaged Extrasolar Giant Planets

Tan

Showman

2019

ApJ

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Growing observational evidence has suggested active meteorology in the atmospheres of brown dwarfs (BDs) and directly imaged extrasolar giant planets (EGPs). In particular, a number of surveys have shown that near-IR brightness variability is common among L and T dwarfs. Despite the likelihood from previous studies that atmospheric dynamics is the major cause of the variability, the detailed mechanism of the variability remains elusive, and we need to seek a natural, self-consistent mechanism. Clouds are important in shaping the thermal structure and spectral properties of these atmospheres via their opacity, and we expect the same for inducing atmospheric variability. In this work, using a time-dependent one-dimensional model that incorporates a self-consistent coupling between the thermal structure, convective mixing, cloud radiative heating/cooling and condensation/evaporation of clouds, we show that radiative cloud feedback can drive spontaneous atmospheric variability in both temperature and cloud structure under conditions appropriate for BDs and directly imaged EGPs. The typical periods of variability are one to tens of hours with typical amplitude of the variability up to hundreds of Kelvins in effective temperature. The existence of variability is robust over a wide range of parameter space, but the detailed evolution of the variability is sensitive to model parameters. Our novel, self-consistent mechanism has important implications for the observed flux variability of BDs and directly imaged EGPs, especially for objects whose variability evolves on short timescales. It is also a promising mechanism for cloud breaking, which has been proposed to explain the L/T transition of brown dwarfs. Subject headings: brown dwarfs -planets and satellites: gaseous planets -planets and satellites:atmospheres -radiative transfer -methods: numerical arXiv:1809.06467v2 [astro-ph.SR]

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“…The spectra of L dwarfs (1300-2200 K; Stephens et al 2009) are best fit by models that include a thick cloud layer of iron, silicates, and corundum (Saumon & Marley 2008). Those clouds break up non-uniformly and disappear as brown dwarfs grow cooler and enter the T dwarf sequence (500-1300 K; Stephens et al 2009), as indicated by the near-infrared (IR) colors (Burgasser et al 2002), photometric and spectral variability (Buenzli et al 2014;Burgasser et al 2014;Radigan et al 2014;Wilson et al 2014;Yang et al 2016), and surface maps Karalidi et al 2016) of objects near the L/T transition. Clouds may appear again below 900 K based on the colors of late T dwarfs, this time in the form of sulfides (Morley et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Photometric Monitoring of the Coldest Known Brown Dwarf With the Spitzer Space Telescope*

Esplin

Luhman

Cushing

et al. 2016

ApJ

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Because WISE J085510.83−071442.5 (hereafter WISE 0855-0714) is the coldest known brown dwarf (∼ 250 K) and one of the Sun's closest neighbors (2.2 pc), it offers a unique opportunity for studying a planet-like atmosphere in an unexplored regime of temperature. To detect and characterize inhomogeneities in its atmosphere (e.g., patchy clouds, hot spots), we have performed time-series photometric monitoring of WISE 0855-0714 at 3.6 and 4.5 µm with the Spitzer Space Telescope during two 23 hr periods that were separated by several months. For both bands, we have detected variability with peak-to-peak amplitudes of 4-5% and 3-4% in the first and second epochs, respectively. The light curves are semi-periodic in the first epoch for both bands, but are more irregular in the second epoch. Models of patchy clouds have predicted a large increase in mid-IR variability amplitudes (for a given cloud covering fraction) with the appearance of water ice clouds at T eff <375 K, so if such clouds are responsible for the variability of WISE 0855-0714, then its small amplitudes of variability indicate a very small deviation in cloud coverage between hemispheres. Alternatively, the similarity in mid-IR variability amplitudes between WISE 0855-0714 and somewhat warmer T and Y dwarfs may suggest that they share a common origin for their variability (i.e., not water clouds). In addition to our variability data, we have examined other constraints on the presence of water ice clouds in the atmosphere of WISE 0855-0714, including the recent mid-IR spectrum from Skemer et al. (2016). We find that robust evidence of such clouds is not yet available.

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Maps of Evolving Cloud Structures in Luhman 16ab From HST Time-Resolved Spectroscopy

Cited by 47 publications

References 31 publications

Simultaneous Multiwavelength Variability Characterization of the Free-floating Planetary-mass Object PSO J318.5−22

Simultaneous Multiwavelength Variability Characterization of the Free-floating Planetary-mass Object PSO J318.5−22

Atmospheric Variability Driven by Radiative Cloud Feedback in Brown Dwarfs and Directly Imaged Extrasolar Giant Planets

Photometric Monitoring of the Coldest Known Brown Dwarf With the Spitzer Space Telescope*

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