Journal Article

Polarization in microlensing events towards the Galactic bulge

G. Ingrosso, S. Calchi Novati, F. De Paolis, Ph. Jetzer, A. A. Nucita, F. Strafella and A. F. Zakharov

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 426, issue 2, pages 1496-1506
Published in print October 2012 | ISSN: 0035-8711
Published online October 2012 | e-ISSN: 1365-2966 | DOI:
Polarization in microlensing events towards the Galactic bulge

Show Summary Details


Gravitational microlensing, when finite size source effects are relevant, provides a unique tool for the study of source star stellar atmospheres through an enhancement of a characteristic polarization signal. This is due to the differential magnification induced during the crossing of the source star. In this paper, we consider a specific set of reported highly magnified, both single and binary exoplanetary systems, microlensing events towards the Galactic bulge and evaluate the expected polarization signal. For this purpose, we consider several polarization models which apply to different types of source stars: hot, late type main sequence and cool giants. As a result we compute the polarization signal P, which goes up to P = 0.04 per cent for late-type stars and up to a few per cent for cool giants, depending on the underlying physical polarization processes and atmosphere model parameters. Given an I-band magnitude at a maximum magnification of about 12 and a typical duration of the polarization signal up to 1 d, we conclude that the currently available technology, in particular the polarimeter in FOcal Reducer and low dispersion Spectrograph 2 (FORS2) on the Very Large Telescope (VLT), potentially may allow the detection of such signals. This observational programme may take advantage of the currently available surveys plus follow-up strategy already routinely used for microlensing monitoring towards the Galactic bulge (aimed at the detection of exoplanets). In particular, this allows one to predict in advance for which events and at which exact time the observing resources may be focused to make intensive polarization measurements.

Keywords: Physical data and processes: polarization; The Galaxy: bulge

Journal Article.  8339 words.  Illustrated.

Subjects: Astronomy and Astrophysics

Full text: subscription required

How to subscribe Recommend to my Librarian

Users without a subscription are not able to see the full content. Please, subscribe or login to access all content.