VLA Discovers Brown Dwarf Exo-aurora
Aurorae are detected from all the magnetized planets in our Solar System. They are powered by magnetospheric current systems that lead to the precipitation of energetic electrons into the high-latitude regions of the upper atmosphere. In the case of the gas-giant planets, these aurorae include highly polarized radio emission at kilohertz and megahertz frequencies produced by the precipitating electrons, as well as continuum and line emission in the infrared, optical, ultraviolet and X-ray parts of the spectrum, associated with the collisional excitation and heating of the hydrogen-dominated atmosphere.
Using the VLA, Keck, and Palomar, Hallinan et al have discovered auroral emission from the M8.5 brown dwarf J1835+3259, located 5.7pc from Earth. VLA dynamic spectra show circularly polarized cyclotron emission 104 stronger than Jovian auroral emission, with B ~ 2000G. The aurora may indicate a star-planet interaction, and certainly is one of the root causes of exo-space weather, thereby dictating exo-planet environments.
View Paper: Magnetospherically Driven Optical and Radio Aurorae at the end of the Stellar Main Sequence, G. Hallinan (Caltech), S. P. Littlefair (Sheffield), G. Cotter (Oxford), S. Bourke (Caltech), L. K. Harding (JPL), J. S. Pineda (Caltech), R. P. Butler (Ireland-Galway), A. Golden (Yeshiva), G. Basri (UC, Berkeley), J.G. Doyle (Armagh), M. M. Kao (Caltech), S. V. Berdyugina (Kiepenheuer), A. Kuznetsov (Institute of Solar-Terrestial Physics), M. P. Rupen (NRAO) and A. Antonova (Sofia), 2015 Nature, 523, 568 (Published online 30 July 2015).
