Journal Article

Diffractive microlensing – II. Substellar disc and halo objects

Jeremy S. Heyl

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 411, issue 3, pages 1780-1786
Published in print March 2011 | ISSN: 0035-8711
Published online February 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.17806.x
Diffractive microlensing – II. Substellar disc and halo objects

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Microlensing is generally studied in the geometric optics limit. However, diffraction may be important when nearby substellar objects' lens occult distant stars. In particular the effects of diffraction become more important as the wavelength of the observation increases. Typically if the wavelength of the observation is comparable to the Schwarzschild radius of lensing object, diffraction leaves an observable imprint on the lensing signature. The commissioning of the Square Kilometre Array (SKA) over the next decade begs the question of whether it will become possible to follow up lensing events with radio observations because the SKA may have sufficient sensitivity to detect the typical sources, giant stars in the bulge. The detection of diffractive lensing in a lensing event would place unique constraints on the mass of the lens and its distance. In particular it would distinguish rapidly moving stellar mass lenses (e.g. neutron stars) from slowly moving substellar objects such as freely floating planets. An analysis of the sensitivity of the SKA along with new simple closed-form estimates of the expected signal applied to local exemplars for stellar radio emission reveals that this effect can nearly be detected with the SKA. If the radio emission from bulge giants is stronger than expected, the SKA could detect the diffractive microlensing signature from Earth-like interstellar planets in the solar neighbourhood.

Keywords: gravitational lensing: micro; planets and satellites: general; radio continuum: stars

Journal Article.  4707 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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