TY - JOUR
T1 - Directly imaged L-T transition exoplanets in the mid-infrared
AU - Skemer, Andrew J.
AU - Marley, Mark S.
AU - Hinz, Philip M.
AU - Morzinski, Katie M.
AU - Skrutskie, Michael F.
AU - Leisenring, Jarron M.
AU - Close, Laird M.
AU - Saumon, Didier
AU - Bailey, Vanessa P.
AU - Briguglio, Runa
AU - Defrere, Denis
AU - Esposito, Simone
AU - Follette, Katherine B.
AU - Hill, John M.
AU - Males, Jared R.
AU - Puglisi, Alfio
AU - Rodigas, Timothy J.
AU - Xompero, Marco
PY - 2014/9/1
Y1 - 2014/9/1
N2 - Gas-giant planets emit a large fraction of their light in the mid-infrared (≳3 μm), where photometry and spectroscopy are critical to our understanding of the bulk properties of extrasolar planets. Of particular importance are the L- and M-band atmospheric windows (3-5 μm), which are the longest wavelengths currently accessible to ground-based, high-contrast imagers. We present binocular LBT adaptive optics (AO) images of the HR 8799 planetary system in six narrow-band filters from 3 to 4 μm, and a Magellan AO image of the 2M1207 planetary system in a broader 3.3 μm band. These systems encompass the five known exoplanets with luminosities consistent with L → T transition brown dwarfs. Our results show that the exoplanets are brighter and have shallower spectral slopes than equivalent temperature brown dwarfs in a wavelength range that contains the methane fundamental absorption feature (spanned by the narrow-band filters and encompassed by the broader 3.3 μm filter). For 2M1207 b, we find that thick clouds and non-equilibrium chemistry caused by vertical mixing can explain the object's appearance. For the HR 8799 planets, we present new models that suggest the atmospheres must have patchy clouds, along with non-equilibrium chemistry. Together, the presence of a heterogeneous surface and vertical mixing presents a picture of dynamic planetary atmospheres in which both horizontal and vertical motions influence the chemical and condensate profiles.
AB - Gas-giant planets emit a large fraction of their light in the mid-infrared (≳3 μm), where photometry and spectroscopy are critical to our understanding of the bulk properties of extrasolar planets. Of particular importance are the L- and M-band atmospheric windows (3-5 μm), which are the longest wavelengths currently accessible to ground-based, high-contrast imagers. We present binocular LBT adaptive optics (AO) images of the HR 8799 planetary system in six narrow-band filters from 3 to 4 μm, and a Magellan AO image of the 2M1207 planetary system in a broader 3.3 μm band. These systems encompass the five known exoplanets with luminosities consistent with L → T transition brown dwarfs. Our results show that the exoplanets are brighter and have shallower spectral slopes than equivalent temperature brown dwarfs in a wavelength range that contains the methane fundamental absorption feature (spanned by the narrow-band filters and encompassed by the broader 3.3 μm filter). For 2M1207 b, we find that thick clouds and non-equilibrium chemistry caused by vertical mixing can explain the object's appearance. For the HR 8799 planets, we present new models that suggest the atmospheres must have patchy clouds, along with non-equilibrium chemistry. Together, the presence of a heterogeneous surface and vertical mixing presents a picture of dynamic planetary atmospheres in which both horizontal and vertical motions influence the chemical and condensate profiles.
KW - brown dwarfs
KW - infrared: planetary systems
KW - instrumentation: adaptive optics
KW - planets and satellites: atmospheres
KW - planets and satellites: gaseous planets
KW - stars: individual (HR 8799, 2M1207 b)
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U2 - 10.1088/0004-637X/792/1/17
DO - 10.1088/0004-637X/792/1/17
M3 - Article
AN - SCOPUS:84906279700
SN - 0004-637X
VL - 792
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
M1 - 17
ER -