Microlensing modulation by quadrupole variation

Abstract

We investigate microlensing in the case where the lens is considered as an extended object. We use a multipolar expansion of the lens potential and show that the time-varying nature of the quadrupole contribution allows to separate it from the mass and spin contributions and leads to specific modulations of the amplification signal. As example we study the case of binary system lenses in our galaxy. The modulation is observable if the rotation period of the system is smaller than the time over which the amplification is significant and if the impact parameter of the passing light ray is sufficiently close to the Einstein radius so that the amplification is large. Observations of this modulation can reveal important information on the quadrupole and thus on the gravitational radiation emitted by the binary lens. Even if not observed directly, because of their importance the quadrupole modulation has to be included in the error budget for high magnification ($\mu \le 7$) microlensing events.

Matches publicated version

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Cited by in corpus (3)

• Rapidly Rotating Lenses: Repeating features in the lightcurves of short period binary microlenses
• The Erez-Rosen metric and the role of the quadrupole on light propagation
• Detecting binarity of GW150914-like lenses in gravitational microlensing events