Cloud Atlas: Discovery of Rotational Spectral Modulations in a Low-mass, L-type Brown Dwarf Companion to a Star

Elena Manjavacas, Dániel Apai, Yifan Zhou, Theodora Karalidi, Ben W.P. Lew, Glenn Schneider, Nicolas Cowan, Stan Metchev, Paulo A. Miles-Páez, Adam J. Burgasser, Jacqueline Radigan, Luigi R. Bedin, Patrick J. Lowrance, Mark S. Marley

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


Observations of rotational modulations of brown dwarfs and giant exoplanets allow the characterization of condensate cloud properties. As of now, rotational spectral modulations have only been seen in three L-type brown dwarfs. We report here the discovery of rotational spectral modulations in LP261-75B, an L6-type intermediate surface gravity companion to an M4.5 star. As a part of the Cloud Atlas Treasury program, we acquired time-resolved Wide Field Camera 3 grism spectroscopy (1.1-1.69 μm) of LP261-75B. We find gray spectral variations with the relative amplitude displaying only a weak wavelength dependence and no evidence for lower-amplitude modulations in the 1.4 μm water band than in the adjacent continuum. The likely rotational modulation period is 4.78 ± 0.95 hr, although the rotational phase is not well sampled. The minimum relative amplitude in the white light curve measured over the whole wavelength range is 2.41% ± 0.14%. We report an unusual light curve, which seems to have three peaks approximately evenly distributed in rotational phase. The spectral modulations suggests that the upper atmosphere cloud properties in LP261-75B are similar to two other mid-L dwarfs of typical infrared colors, but differ from that of the extremely red L-dwarf WISE0047.

Original languageEnglish (US)
Article number11
JournalAstronomical Journal
Issue number1
StatePublished - Jan 2018

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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