Published October 31, 2019 | Version v1
Presentation Open

Rotational modulations of a rare planetary-mass object at the end of the L/T transition

  • 1. University of Arizona
  • 2. Utah Valley University
  • 3. NASA Ames Research Center
  • 4. McGill University
  • 5. European Southern Observatory
  • 6. W.M. Keck Observatory
  • 7. University of Central Florida
  • 8. INAF-Osservatorio Astronomico di Padova
  • 9. IPAC-Spitzer
  • 10. University of California San Diego


Among the greatest challenges in understanding ultra-cool brown dwarf and exoplanet atmospheres is the evolution of cloud structure as a function of temperature and gravity. In the narrow effective temperature range across the L/T spectral-type transition, the drastic color (J-H, J-Ks) change across the L/T transition objects demonstrates the key role of cloud structure evolution for the near-infrared spectra of ultra-cool atmospheres. One of the most powerful methods to study the cloud structure is time-resolved spectrophotometry. Based on the rotation-modulated flux variation, we can constrain the rotational asymmetric features in a heterogeneous atmosphere. Understanding the atmospheric heterogeneity of L/T transition objects with different gravities and temperatures allows us to test different possible mechanisms to explain the L/T transition. In my talk, I will present the HST high-precision time-resolved spectra of a rare mid-T planetary-mass object at the end of the L/T transition. With this object, we now have collected a small sample of valuable low-gravity objects with detected rotation-modulated spectral modulation across the L/T transition. Based on the sample with detected spectral variability, I will also present a tentative trend across the L/T transition on the color-magnitude diagram.



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