Optical linear polarization in ultra cool dwarfs A tool to probe dust in the ultra cool dwarf atmospheres
Abbreviated Journal Title
polarization; atmospheric effects; stars: low-mass, brown dwarfs; LOW-MASS STARS; BROWN DWARFS; T-DWARFS; MODEL ATMOSPHERES; PHOTOMETRY; CLOUDS; EVOLUTIONARY; TEMPERATURE; TRANSITION; SCATTERING; Astronomy & Astrophysics
Aims. Recent studies have detected linear polarization in L dwarfs in the optical I band. Theoretical models have been developed to explain this polarization. These models predict higher polarization at shorter wavelengths. We discuss the polarization in the R and I band of 4 ultra cool dwarfs. Methods. We report linear polarization measurements of 4 ultra cool dwarfs in the R and I bands using the Intermediate dispersion Spectrograph and Imaging System ( ISIS) mounted on the 4.2 m William Herschel Telescope (WHT). Results. As predicted by theoretical models, we find a higher degree of polarization in the R band when compared to polarization in the I band for 3/4 of these ultra cool dwarfs. This suggests that dust scattering asymmetry is caused by oblateness. We also show how these measurements fit the theoretical models. A case for variability of linear polarization is found, which suggests the presence of randomly distributed dust clouds. We also discuss one case for the presence of a cold debris disk.
Astronomy & Astrophysics
"Optical linear polarization in ultra cool dwarfs A tool to probe dust in the ultra cool dwarf atmospheres" (2009). Faculty Bibliography 2000s. 2218.