The Polarization Signature of Extrasolar Planet Transiting Cool Dwarfs

• Published in: The Astrophysical journal Vol. 635; no. 1; pp. 570 - 577
• Main Authors: Carciofi, A. C, Magalhães, A. M
• Format: Journal Article
• Language: English
• Published: Chicago, IL IOP Publishing 10.12.2005; University of Chicago Press
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; Occultations; Polarization; Extrasolar planets; Sun: général; planetary Systems; Sun; Planetary system
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/497064

We investigate the linear polarization in the light of extrasolar planetary systems that may arise as a result of an occultation of the star by a transiting planet. Such an occultation breaks any spherical symmetry over the projected stellar disk and thus results in a nonvanishing linear polarization. This polarization will furthermore vary as the occultation progresses. We present both analytical and numerical results for the occultation of G, K, M, and T dwarf stars by planets with sizes ranging from that of Earth to 2 times the size of Jupiter. We find that the occultation polarization may result in an observable signal and provide additional means to characterize various parameters of the system. A particularly interesting result is that, for the later spectral types (i.e., smaller stellar radii), this polarization signature may be observable even for Earth-like planets. This suggests polarization as a possible tool to detect such planets. Departures from symmetry around midtransit in the time dependence of the polarization signature may provide an estimate of the orbital eccentricity.