A critical analysis of the recent OGLE limits on stellar mass primordial black holes in the halo of the Milky Way

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Main Authors: Hawkins, M. R. S., García-Bellido, J.
Format: Preprint
Published: 2025
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author Hawkins, M. R. S.
García-Bellido, J.
author_facet Hawkins, M. R. S.
García-Bellido, J.
contents This paper is a response to recent claims that a population of primordial black holes in the Galactic halo has been ruled out by the OGLE collaboration. This claim was based on the latest results from the OGLE microlensing survey towards the Large Magellanic Cloud which failed to detect even the number of events expected from known stellar populations. In particular, their results are completely inconsistent with the results of the MACHO survey which detected a population of compact bodies in the Galactic halo which could not be accounted for by any known stellar population. The discrepancy between the results of these two groups has a long history, and includes problems such as different choice of photometric passbands, quality of light curves, microlensing event selection, detection efficiency, self lensing and halo models. In this paper it is demonstrated that these issues not only account for the discrepancy between the OGLE and MACHO results, but imply that the OGLE observations can put no meaningful constraints on a population of primordial black holes in the Galactic halo.
format Preprint
id arxiv_https___arxiv_org_abs_2509_05400
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle A critical analysis of the recent OGLE limits on stellar mass primordial black holes in the halo of the Milky Way
Hawkins, M. R. S.
García-Bellido, J.
Astrophysics of Galaxies
Cosmology and Nongalactic Astrophysics
This paper is a response to recent claims that a population of primordial black holes in the Galactic halo has been ruled out by the OGLE collaboration. This claim was based on the latest results from the OGLE microlensing survey towards the Large Magellanic Cloud which failed to detect even the number of events expected from known stellar populations. In particular, their results are completely inconsistent with the results of the MACHO survey which detected a population of compact bodies in the Galactic halo which could not be accounted for by any known stellar population. The discrepancy between the results of these two groups has a long history, and includes problems such as different choice of photometric passbands, quality of light curves, microlensing event selection, detection efficiency, self lensing and halo models. In this paper it is demonstrated that these issues not only account for the discrepancy between the OGLE and MACHO results, but imply that the OGLE observations can put no meaningful constraints on a population of primordial black holes in the Galactic halo.
title A critical analysis of the recent OGLE limits on stellar mass primordial black holes in the halo of the Milky Way
topic Astrophysics of Galaxies
Cosmology and Nongalactic Astrophysics
url https://arxiv.org/abs/2509.05400