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http://hdl.handle.net/2248/7096
Title: | Polarimetric detection of exoplanets transiting T and L brown dwarfs |
Authors: | Sengupta, S |
Keywords: | Polarization Radiative transfer Scattering |
Issue Date: | Oct-2016 |
Publisher: | IOP Publishing |
Citation: | The Astronomical Journal, Vol. 152, No. 4, 98 |
Abstract: | While scattering of light by atoms and molecules yields large amounts of polarization at the B-band of both T and L dwarfs, scattering by dust grains in the cloudy atmosphere of L dwarfs gives rise to significant polarization at the far-optical and infrared wavelengths where these objects are much brighter. However, the observable disk-averaged polarization should be zero if the clouds are uniformly distributed and the object is spherically symmetric. Therefore, in order to explain the observed large polarization of several L dwarfs, rotation-induced oblateness or horizontally inhomogeneous cloud distribution in the atmosphere is invoked. On the other hand, when an extra-solar planet of Earth-size or larger transits the brown dwarf along the line of sight, the asymmetry induced during the transit gives rise to a net non-zero, time-dependent polarization. Employing atmospheric models for a range of effective temperature and surface gravity appropriate for T and L dwarfs, I derive the time-dependent polarization profiles of these objects during the transit phase and estimate the peak amplitude of polarization that occurs during the inner contact points of the transit ingress/egress phase. It is found that peak polarization in the range of 0.2%–1.0% at I and J band may arise of cloudy L dwarfs occulted by Earth-size or larger exoplanets. Such an amount of polarization is higher than what can be produced by rotation-induced oblateness of even rapidly rotating L dwarfs. Hence, I suggest that time-resolved imaging polarization could be a potential technique for detecting transiting exoplanets around L dwarfs. |
Description: | Restricted Access © The American Astronomical Society http://dx.doi.org/10.3847/0004-6256/152/4/98 |
URI: | http://prints.iiap.res.in/handle/2248/7096 |
ISSN: | 1538-4357 |
Appears in Collections: | IIAP Publications |
Files in This Item:
File | Description | Size | Format | |
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Polarimetric Detection of Exoplanets Transiting T and L Brown Dwarfs.pdf | 400.91 kB | Adobe PDF | View/Open |
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