Microlensing and photon bunching: the impact of decoherence. Issue 4 (9th December 2019)

• Record Type: Journal Article
• Authors: Lewis, Geraint F; Tuthill, Peter
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 491:Issue 4(2020)
• Page Start: 5789
• Page End: 5792
• Publication Date: 2019-12-09
• Subjects: gravitational lensing: micro -- techniques: interferometric; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stz3443
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: Gravitational microlensing within the Galaxy offers the prospect of probing the details of distant stellar sources, as well as revealing the distribution of compact (and potentially non-luminous) masses along the line of sight. Recently, it has been suggested that additional constraints on the lensing properties can be determined through the measurement of the time delay between images through the correlation of the bunching of photon arrival times; an application of the Hanbury–Brown Twiss effect. In this paper, we revisit this analysis, examining the impact of decoherence of the radiation from a spatially extended source along the multiple paths to an observer. The result is that, for physically reasonable situations, such decoherence completely erases any correlation that could otherwise be used to measure the gravitational lensing time delay. Indeed, the divergent light paths traverse extremely long effective baselines at the lens plane, corresponding to extremes of angular resolving power well beyond those attainable with any terrestrial technologies; the drawback being that few conceivable celestial objects would be sufficiently compact with high enough surface brightness to yield usable signals.