Cloud Atlas: Rotational Spectral Modulations and Potential Sulfide Clouds in the Planetary-mass, Late T-type Companion Ross 458C

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

Research output: Contribution to journalArticle

6 Scopus citations

Abstract

Measurements of photometric variability at different wavelengths provide insights into the vertical cloud structure of brown dwarfs and planetary-mass objects. In seven Hubble Space Telescope consecutive orbits, spanning ∼10 hr of observing time, we obtained time-resolved spectroscopy of the planetary-mass T8 dwarf Ross 458 C using the near-infrared Wide Field Camera 3. We found spectrophotometric variability with a peak-to-peak signal of 2.62 ± 0.02% (in the 1.10-1.60 μm white light curve). Using three different methods, we estimated a rotational period of 6.75 ± 1.58 hr for the white light curve, and similar periods for narrow J- and H-band light curves. Sine wave fits to the narrow J- and H-band light curves suggest a tentative phase shift between the light curves with wavelength when we allow different periods between both light curves. If confirmed, this phase shift may be similar to the phase shift detected earlier for the T6.5 spectral type 2MASS J22282889-310262. We find that, in contrast with 2M2228, the variability of Ross 458C shows evidence for a color trend within the narrow J-band, but gray variations in the narrow H-band. The spectral time-resolved variability of Ross 458C might be potentially due to heterogeneous sulfide clouds in the atmosphere of the object. Our discovery extends the study of spectral modulations of condensate clouds to the coolest T-dwarf, planetary-mass companions.

Original languageEnglish (US)
Article numberL15
JournalAstrophysical Journal Letters
Volume875
Issue number2
DOIs
StatePublished - Apr 20 2019

Keywords

  • brown dwarfs
  • stars: atmospheres

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Manjavacas, E., Apai, D., Lew, B. W. P., Zhou, Y., Schneider, G., Burgasser, A. J., Karalidi, T., Miles-Páez, P. A., Lowrance, P. J., Cowan, N., Bedin, L. R., Marley, M. S., Metchev, S., & Radigan, J. (2019). Cloud Atlas: Rotational Spectral Modulations and Potential Sulfide Clouds in the Planetary-mass, Late T-type Companion Ross 458C. Astrophysical Journal Letters, 875(2), [L15]. https://doi.org/10.3847/2041-8213/ab13b9