Weather on Other Worlds. V. The Three Most Rapidly Rotating Ultra-Cool Dwarfs. (arXiv:2103.01990v2 [astro-ph.SR] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Tannock_M/0/1/0/all/0/1">Megan E. Tannock</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Metchev_S/0/1/0/all/0/1">Stanimir Metchev</a> (2 and 3), <a href="http://arxiv.org/find/astro-ph/1/au:+Heinze_A/0/1/0/all/0/1">Aren Heinze</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Miles_Paez_P/0/1/0/all/0/1">Paulo A. Miles-Páez</a> (5), <a href="http://arxiv.org/find/astro-ph/1/au:+Gagne_J/0/1/0/all/0/1">Jonathan Gagné</a> (6 and 7), <a href="http://arxiv.org/find/astro-ph/1/au:+Burgasser_A/0/1/0/all/0/1">Adam Burgasser</a> (8), <a href="http://arxiv.org/find/astro-ph/1/au:+Marley_M/0/1/0/all/0/1">Mark S. Marley</a> (9), <a href="http://arxiv.org/find/astro-ph/1/au:+Apai_D/0/1/0/all/0/1">Dániel Apai</a> (10 and 11), <a href="http://arxiv.org/find/astro-ph/1/au:+Suarez_G/0/1/0/all/0/1">Genaro Suárez</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Plavchan_P/0/1/0/all/0/1">Peter Plavchan</a> (12) ((1) University of Western Ontario, (2) Institute for Earth and Space Exploration, The University of Western Ontario, (3) American Museum of Natural History, (4) Institute for Astronomy, University of Hawaii, (5) European Southern Observatory, (6) Planétarium Rio Tinto Alcan, Espace pour la Vie, (7) Institute for Research on Exoplanets, Université de Montréal, (8) University of California, San Diego, (9) NASA Ames Research Center, (10) Steward Observatory, The University of Arizona, (11) Lunar and Planetary Laboratory, The University of Arizona, (12) George Mason University)
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, 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 $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.
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, 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 $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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