HST rotational spectral mapping of two L-type brown dwarfs: Variability in and out of water bands indicates high-altitude haze layers

Hao Yang, Daniel Apai, Mark S. Marley, Didier Saumon, Caroline V. Morley, Esther Buenzli, Étienne Artigau, Jacqueline Radigan, Stanimir Metchev, Adam J. Burgasser, Subhanjoy Mohanty, Patrick J. Lowrance, Adam Showman, Theodora Karalidi, Davin Flateau, Aren N. Heinze

Research output: Contribution to journalArticle

26 Citations (Scopus)

Abstract

We present time-resolved near-infrared spectroscopy of two L5 dwarfs, 2MASS J18212815+1414010 and 2MASS J15074759-1627386, observed with the Wide Field Camera 3 instrument on the Hubble Space Telescope (HST). We study the wavelength dependence of rotation-modulated flux variations between 1.1 innodatamum and 1.7 innodatamum. We find that the water absorption bands of the two L5 dwarfs at 1.15 μm and 1.4 μm vary at similar amplitudes as the adjacent continuum. This differs from the results of previous HST observations of L/T transition dwarfs, in which the water absorption at 1.4 μm displays variations of about half of the amplitude at other wavelengths. We find that the relative amplitude of flux variability out of the water band with respect to that in the water band shows a increasing trend from the L5 dwarfs toward the early T dwarfs.We utilize the models of Saumon & Marley and find that the observed variability of the L5 dwarfs can be explained by the presence of spatially varying high-altitude haze layers above the condensate clouds. Therefore, our observations show that the heterogeneity of haze layers - the driver of the variability - must be located at very low pressures, where even the water opacity is negligible. In the near future, the rotational spectral mapping technique could be utilized for other atomic and molecular species to probe different pressure levels in the atmospheres of brown dwarfs and exoplanets and uncover both horizontal and vertical cloud structures.

Original languageEnglish (US)
Article numberL13
JournalAstrophysical Journal Letters
Volume798
Issue number1
DOIs
StatePublished - Jan 1 2015

Fingerprint

haze
high altitude
Hubble Space Telescope
water
wavelength
extrasolar planets
pressure sensors
condensate
opacity
infrared spectroscopy
wavelengths
condensates
low pressure
near infrared
cameras
probe
continuums
absorption spectra
trends
atmospheres

Keywords

  • Brown dwarfs
  • Stars: atmospheres
  • Stars: individual (2MASS J18212815+1414010, 2MASSJ15074769-1627386, 2MASS J01365662+0933473)
  • Stars: low-mass

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

HST rotational spectral mapping of two L-type brown dwarfs : Variability in and out of water bands indicates high-altitude haze layers. / Yang, Hao; Apai, Daniel; Marley, Mark S.; Saumon, Didier; Morley, Caroline V.; Buenzli, Esther; Artigau, Étienne; Radigan, Jacqueline; Metchev, Stanimir; Burgasser, Adam J.; Mohanty, Subhanjoy; Lowrance, Patrick J.; Showman, Adam; Karalidi, Theodora; Flateau, Davin; Heinze, Aren N.

In: Astrophysical Journal Letters, Vol. 798, No. 1, L13, 01.01.2015.

Research output: Contribution to journalArticle

Yang, H, Apai, D, Marley, MS, Saumon, D, Morley, CV, Buenzli, E, Artigau, É, Radigan, J, Metchev, S, Burgasser, AJ, Mohanty, S, Lowrance, PJ, Showman, A, Karalidi, T, Flateau, D & Heinze, AN 2015, 'HST rotational spectral mapping of two L-type brown dwarfs: Variability in and out of water bands indicates high-altitude haze layers', Astrophysical Journal Letters, vol. 798, no. 1, L13. https://doi.org/10.1088/2041-8205/798/1/L13
Yang, Hao ; Apai, Daniel ; Marley, Mark S. ; Saumon, Didier ; Morley, Caroline V. ; Buenzli, Esther ; Artigau, Étienne ; Radigan, Jacqueline ; Metchev, Stanimir ; Burgasser, Adam J. ; Mohanty, Subhanjoy ; Lowrance, Patrick J. ; Showman, Adam ; Karalidi, Theodora ; Flateau, Davin ; Heinze, Aren N. / HST rotational spectral mapping of two L-type brown dwarfs : Variability in and out of water bands indicates high-altitude haze layers. In: Astrophysical Journal Letters. 2015 ; Vol. 798, No. 1.
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abstract = "We present time-resolved near-infrared spectroscopy of two L5 dwarfs, 2MASS J18212815+1414010 and 2MASS J15074759-1627386, observed with the Wide Field Camera 3 instrument on the Hubble Space Telescope (HST). We study the wavelength dependence of rotation-modulated flux variations between 1.1 innodatamum and 1.7 innodatamum. We find that the water absorption bands of the two L5 dwarfs at 1.15 μm and 1.4 μm vary at similar amplitudes as the adjacent continuum. This differs from the results of previous HST observations of L/T transition dwarfs, in which the water absorption at 1.4 μm displays variations of about half of the amplitude at other wavelengths. We find that the relative amplitude of flux variability out of the water band with respect to that in the water band shows a increasing trend from the L5 dwarfs toward the early T dwarfs.We utilize the models of Saumon & Marley and find that the observed variability of the L5 dwarfs can be explained by the presence of spatially varying high-altitude haze layers above the condensate clouds. Therefore, our observations show that the heterogeneity of haze layers - the driver of the variability - must be located at very low pressures, where even the water opacity is negligible. In the near future, the rotational spectral mapping technique could be utilized for other atomic and molecular species to probe different pressure levels in the atmospheres of brown dwarfs and exoplanets and uncover both horizontal and vertical cloud structures.",
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T1 - HST rotational spectral mapping of two L-type brown dwarfs

T2 - Variability in and out of water bands indicates high-altitude haze layers

AU - Yang, Hao

AU - Apai, Daniel

AU - Marley, Mark S.

AU - Saumon, Didier

AU - Morley, Caroline V.

AU - Buenzli, Esther

AU - Artigau, Étienne

AU - Radigan, Jacqueline

AU - Metchev, Stanimir

AU - Burgasser, Adam J.

AU - Mohanty, Subhanjoy

AU - Lowrance, Patrick J.

AU - Showman, Adam

AU - Karalidi, Theodora

AU - Flateau, Davin

AU - Heinze, Aren N.

PY - 2015/1/1

Y1 - 2015/1/1

N2 - We present time-resolved near-infrared spectroscopy of two L5 dwarfs, 2MASS J18212815+1414010 and 2MASS J15074759-1627386, observed with the Wide Field Camera 3 instrument on the Hubble Space Telescope (HST). We study the wavelength dependence of rotation-modulated flux variations between 1.1 innodatamum and 1.7 innodatamum. We find that the water absorption bands of the two L5 dwarfs at 1.15 μm and 1.4 μm vary at similar amplitudes as the adjacent continuum. This differs from the results of previous HST observations of L/T transition dwarfs, in which the water absorption at 1.4 μm displays variations of about half of the amplitude at other wavelengths. We find that the relative amplitude of flux variability out of the water band with respect to that in the water band shows a increasing trend from the L5 dwarfs toward the early T dwarfs.We utilize the models of Saumon & Marley and find that the observed variability of the L5 dwarfs can be explained by the presence of spatially varying high-altitude haze layers above the condensate clouds. Therefore, our observations show that the heterogeneity of haze layers - the driver of the variability - must be located at very low pressures, where even the water opacity is negligible. In the near future, the rotational spectral mapping technique could be utilized for other atomic and molecular species to probe different pressure levels in the atmospheres of brown dwarfs and exoplanets and uncover both horizontal and vertical cloud structures.

AB - We present time-resolved near-infrared spectroscopy of two L5 dwarfs, 2MASS J18212815+1414010 and 2MASS J15074759-1627386, observed with the Wide Field Camera 3 instrument on the Hubble Space Telescope (HST). We study the wavelength dependence of rotation-modulated flux variations between 1.1 innodatamum and 1.7 innodatamum. We find that the water absorption bands of the two L5 dwarfs at 1.15 μm and 1.4 μm vary at similar amplitudes as the adjacent continuum. This differs from the results of previous HST observations of L/T transition dwarfs, in which the water absorption at 1.4 μm displays variations of about half of the amplitude at other wavelengths. We find that the relative amplitude of flux variability out of the water band with respect to that in the water band shows a increasing trend from the L5 dwarfs toward the early T dwarfs.We utilize the models of Saumon & Marley and find that the observed variability of the L5 dwarfs can be explained by the presence of spatially varying high-altitude haze layers above the condensate clouds. Therefore, our observations show that the heterogeneity of haze layers - the driver of the variability - must be located at very low pressures, where even the water opacity is negligible. In the near future, the rotational spectral mapping technique could be utilized for other atomic and molecular species to probe different pressure levels in the atmospheres of brown dwarfs and exoplanets and uncover both horizontal and vertical cloud structures.

KW - Brown dwarfs

KW - Stars: atmospheres

KW - Stars: individual (2MASS J18212815+1414010, 2MASSJ15074769-1627386, 2MASS J01365662+0933473)

KW - Stars: low-mass

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U2 - 10.1088/2041-8205/798/1/L13

DO - 10.1088/2041-8205/798/1/L13

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