Poster Open Access
Tannock, Megan E.;
Metchev, Stanimir;
Heinze, Aren;
Miles-Páez, Paulo;
Gagné, Jonathan;
Burgasser, Adam;
Marley, Mark S.;
Apai, Dániel;
Suarez, Genaro;
Plavchan, Peter
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: \({1.080}^{+0.004}_{-0.005}\) h, \({1.14}^{+0.03}_{-0.01}\) h, and \({1.23}^{+0.01}_{-0.01}\) h, respectively. We confirm the rapid rotation through moderate-resolution infrared spectroscopy that 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 \(\gtrsim\)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 h suggests that brown dwarfs are unlikely to spin much faster.
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