On the detection of caustic crossing events associated with dark matter in the form of primordial black holes

Fuente: arXiv
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Autore principale: Hawkins, M. R. S.
Natura: Preprint
Pubblicazione: 2025
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author Hawkins, M. R. S.
author_facet Hawkins, M. R. S.
contents The possibility that stellar mass primordial black holes may make up at least a significant fraction of dark matter has recently received much attention, partly as a result of gravitational wave observations, but more specifically from observations of microlensing in the Galactic halo and in quasar gravitational lens systems. If this is the case then a number of observable consequences are to be expected. This paper focusses on the prediction that dark matter in the form of primordial black holes will result in a web of caustics which when traversed by quasars will result in a complex but characteristic amplification of the accretion disc light source. Caustic crossings produce features in quasar light curves which are relatively straightforward to identify, and are hard to associate with any intrinsic mode of variation. Microlensing simulations are used to clarify the nature of the expected light curve features, and compared with observed light curves to demonstrate that caustic crossing features can be present. A further test of microlensing is based on the expected statistical symmetry of the light curves, which is not predicted for most models of intrinsic quasar variability, but is found in large samples of quasar light curves. The conclusion of the paper is that observations of quasar light curves are consistent with the expected microlensing amplifications from dark matter made up of stellar mass primordial black holes, but cannot easily be explained by intrinsic variations of the quasar accretion disc.
format Preprint
id arxiv_https___arxiv_org_abs_2505_20179
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle On the detection of caustic crossing events associated with dark matter in the form of primordial black holes
Hawkins, M. R. S.
Cosmology and Nongalactic Astrophysics
The possibility that stellar mass primordial black holes may make up at least a significant fraction of dark matter has recently received much attention, partly as a result of gravitational wave observations, but more specifically from observations of microlensing in the Galactic halo and in quasar gravitational lens systems. If this is the case then a number of observable consequences are to be expected. This paper focusses on the prediction that dark matter in the form of primordial black holes will result in a web of caustics which when traversed by quasars will result in a complex but characteristic amplification of the accretion disc light source. Caustic crossings produce features in quasar light curves which are relatively straightforward to identify, and are hard to associate with any intrinsic mode of variation. Microlensing simulations are used to clarify the nature of the expected light curve features, and compared with observed light curves to demonstrate that caustic crossing features can be present. A further test of microlensing is based on the expected statistical symmetry of the light curves, which is not predicted for most models of intrinsic quasar variability, but is found in large samples of quasar light curves. The conclusion of the paper is that observations of quasar light curves are consistent with the expected microlensing amplifications from dark matter made up of stellar mass primordial black holes, but cannot easily be explained by intrinsic variations of the quasar accretion disc.
title On the detection of caustic crossing events associated with dark matter in the form of primordial black holes
topic Cosmology and Nongalactic Astrophysics
url https://arxiv.org/abs/2505.20179