Is WISEP J060738.65+242953.4 Really a Magnetically Active, Pole-on L Dwarf?

Abstract

Abstract The interplay of rotation and manifested magnetic activity on ultracool dwarfs (UCDs) is of key importance for gathering clues regarding the operation of the dynamos within these objects. A number of magnetized UCDs host kG-strength magnetic fields. It was recently reported that the L8 dwarf WISEP J060738.65+242953.4 is a radio-emitting UCD that is likely observed pole-on, due to its lack of photometric variability and narrow spectral lines. Follow-up radio observations at Arecibo Observatory, together with a careful analysis of previously published details, however, suggest that the scientific and statistical significance of the radio and spectroscopic data has been overstated. If the UCD is observed along its aligned spin/magnetic axis, the absence of observed Hα activity may present challenges to the auroral model of UCD magnetism, although short-term or long-term cyclic magnetic activity may explain this behavior. The Monte Carlo simulations presented here suggest that the source probably rotates with km s−1, indicating that its inclination angle and rotational velocity are unexceptional and that its angular momentum has evolved as expected for brown dwarfs observed in ∼1 Myr old clusters. The discovery and verification of the most rapidly and slowest rotating brown dwarfs places valuable constraints on the angular momentum evolution and magnetic activity histories of these objects.