2007/09/07 by C. Lane, G. Hallinan, R. T. Zavala +7 · 2 citations
Physics and Astronomy · #Amplitude #Astrophysics and Star Formation Studies #Magnetic field #Modulation (music) #Pulsars and Gravitational Waves Research #RADIUS #Rotation (mathematics) #Rotation period #Stellar, planetary, and galactic studies #Wavelength #astro-ph
paper · pdf · doi:10.1086/523041
11 pages, 2 figures, accepted for publication in ApJ Letters
arxiv created 2007/09/07 · openalex publication_date 2007/10/02 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
We find periodic I -band variability in two ultracool dwarfs, TVLM 513-46546 and 2MASS J00361617+1821104, on either side of the M/L dwarf boundary. Both of these targets are short-period radio transients, with the detected I -band periods matching those found at radio wavelengths ( P = 1.96 hr for TVLM 513-46546 and P = 3 hr for 2MASS J00361617+1821104). We attribute the detected I -band periodicities to the periods of rotation of the dwarfs, supported by radius estimates and measured v sin i values for the objects. Based on the detected period of rotation of TVLM 513-46546 (M9) in the I band, along with confirmation of strong magnetic fields from recent radio observations, we argue for magnetically induced spots as the cause of this periodic variability. The I -band rotational modulation of the L3.5 dwarf 2MASS J00361617+1821104 appeared to vary in amplitude with time. We conclude that the most likely cause of the I -band variability for this object is magnetic spots, possibly coupled with time-evolving features such as dust clouds.