Weather on Other Worlds. V. The Three Most Rapidly Rotating Ultra-cool Dwarfs

Megan E. Tannock, Stanimir Metchev, Aren Heinze, Paulo A. Miles-Páez, Jonathan Gagné, Adam Burgasser, Mark S. Marley, Dániel Apai, Genaro Suárez, Peter Plavchan

Research output: Contribution to journalArticlepeer-review

35 Scopus citations


We present the discovery of rapid photometric variability in three ultra-cool dwarfs from long-duration monitoring with the Spitzer Space Telescope. The T7, L3.5, and L8 dwarfs have the shortest photometric periods known to date: 1.080-0.005+0.004 hr, 1.14-0.01+0.03 hr, and 1.23-0.01+0.01 hr, respectively. We confirm the rapid rotation through moderate-resolution infrared spectroscopy, which reveals projected rotational velocities between 79 and 104 km s-1. We compare the near-infrared spectra to photospheric models to determine the objects' fundamental parameters and radial velocities. We find that the equatorial rotational velocities for all three objects are ⪆100 km s-1. The three L and T dwarfs reported here are the most rapidly spinning and likely the most oblate field ultra-cool dwarfs known to date. Correspondingly, all three are excellent candidates for seeking auroral radio emission and net optical/infrared polarization. As of this writing, 78 L-, T-, and Y-dwarf rotation periods have now been measured. The clustering of the shortest rotation periods near 1 hr suggests that brown dwarfs are unlikely to spin much faster.

Original languageEnglish (US)
Article number224
JournalAstronomical Journal
Issue number5
StatePublished - May 2021

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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