Title

Optical linear polarization in ultra cool dwarfs A tool to probe dust in the ultra cool dwarf atmospheres

Authors

Authors

R. Tata; E. L. Martin; S. Sengupta; N. Phan-Bao; M. R. Z. Osorio;H. Bouy

Comments

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Abbreviated Journal Title

Astron. Astrophys.

Keywords

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

Abstract

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.

Journal Title

Astronomy & Astrophysics

Volume

508

Issue/Number

3

Publication Date

1-1-2009

Document Type

Article

Language

English

First Page

1423

Last Page

1427

WOS Identifier

WOS:000273057300031

ISSN

0004-6361

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