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A note on the overall magnification of a gravitational point-source-point-lens system
journal contribution
posted on 2023-05-18, 17:07 authored by Stephen WaltersStephen Walters, Lawrence ForbesLawrence ForbesThe total magnification due to a point lens has been of particular interest as the theorem that gravitational lensing results in light amplification for all observers appears to contradict the conservation of photon number. This has been discussed several times, and various resolutions have been offered. In this note, we use a kinematic approach to provide a formula for the magnification factor for the primary image accurate to first order and valid for rays leaving the source at any trajectory. We thus determine the magnification over a sphere surrounding the system. A new result found is that while the magnification dips below unity far from the optical axis as noted by others, it returns to unity directly behind the source.
Funding
Australian Research Council
History
Publication title
Publications of the Astronomical Society of AustraliaVolume
32Article number
e044Number
e044Pagination
1-5ISSN
1323-3580Department/School
School of Natural SciencesPublisher
CSIRO PublishingPlace of publication
150 Oxford St, Po Box 1139, Collingwood, Australia, Victoria, 3066Rights statement
Copyright 2015 Astronomical Society of AustraliaRepository Status
- Restricted