No observational constraints from hypothetical collisions of hypothetical dark halo primordial black holes with galactic objects

TL;DR

This paper investigates the potential observational signatures of hypothetical primordial black holes in the mass range 10^{16}g to 10^{26}g colliding with galactic objects, concluding such events are either too rare or too faint to detect.

Contribution

It explores the unexamined mass range of primordial black holes and assesses their collision signatures with various stars, providing constraints on their detectability.

Findings

Collisions are too rare for PBHs > 1e20g to be observed.

Collisions produce too little power for PBHs < 1e20g to be detected.

The study narrows the observational window for primordial black holes in the galaxy.

Abstract

It was suggested by several authors that hypothetical primordial black holes (PBHs) may contribute to the dark matter in our Galaxy. There are strong constraints based on the Hawking evaporation that practically exclude PBHs with masses m~1e15-1e16g and smaller as significant contributors to the Galactic dark matter. Similarly, PBHs with masses greater than about 1e26g are practically excluded by the gravitational lensing observation. The mass range between 10e16g<m<10e26g is unconstrained. In this paper, we examine possible observational signatures in the unexplored mass range, investigating hypothetical collisions of PBHs with main sequence stars, red giants, white dwarfs, and neutron stars in our Galaxy. This has previously been discussed as possibly leading to an observable photon eruption due to shock production during the encounter. We find that such collisions are either too rare to be observed (if the PBH masses are typically larger than about 1e20g), or produce too little power to be detected (if the masses are smaller than about 1e20g).