NEAR-INFRARED LINEAR POLARIZATION OF ULTRACOOL DWARFS

M. R. Zapatero Osorio, V. J. S. Béjar, B. Goldman, J. A. Caballero, R. Rebolo, J. A. Acosta-Pulido, A. Manchado, K. Peña Ramírez
2011 Astrophysical Journal  
We report on near-infrared J- and H-band linear polarimetric photometry of eight ultracool dwarfs (two late-M, five L0-L7.5, and one T2.5) with known evidence for photometric variability due to dust clouds, anomalous red infrared colors, or low-gravity atmospheres. The polarimetric data were acquired with the LIRIS instrument on the William Herschel Telescope. We also provide mid-infrared photometry in the interval 3.4-24 micron for some targets obtained with Spitzer and WISE, which has allowed
more » ... us to confirm the peculiar red colors of five sources in the sample. We can impose modest upper limits of 0.9% and 1.8% on the linear polarization degree for seven targets with a confidence of 99%. Only one source, 2MAS, J02411151-0326587 (L0), appears to be strongly polarized (P ~ 3%) in the J-band with a significance level of P/sigma_P ~ 10. The likely origin of its linearly polarized light and rather red infrared colors may reside in a surrounding disk with an asymmetric distribution of grains. Given its proximity (66 +/- 8 pc), this object becomes an excellent target for the direct detection of the disk.
doi:10.1088/0004-637x/740/1/4 fatcat:5porfrqk5ncfpntu7ri4en3j3y