Dark black holes in the mass gap

Abstract

In the standard picture of stellar evolution, pair-instability — the energy loss in stellar cores due to electron-positron pair production — is predicted to prevent the collapse of massive stars into black holes with mass in the range between approximately 50 and 130 solar masses — a range known as the “black hole mass gap”. LIGO and Virgo detection of black hole binary mergers containing one or both black holes with masses in this mass gap thus challenges the standard picture, possibly pointing to an unexpected merger history, unanticipated or poorly understood astrophysical mechanisms, or new physics. Here, we entertain the possibility that a “dark sector” exists, consisting of dark electrons, dark protons, and electromagnetic-like interactions, but no nuclear forces. Dark stars would inevitably form given such dark sector constituents, possibly collapsing into black holes with masses within the mass gap. We study in detail the cooling processes necessary for successful stellar collapse in the dark sector and show that for suitable choices of the particle masses, we indeed predict populating the mass gap with dark sector black holes. In particular, we numerically find that the heavier of the two dark sector massive particles cannot be lighter than, approximately, the visible sector proton for the resulting dark sector black holes to have masses within the mass gap. We discuss constraints on this scenario and how to test it with future, larger black hole merger statistics.

Electromagnetic Signatures of Mirror Stars

“…We focus on electromagnetic signals of mirror stars, but microlensing surveys will also be highly sensitive in the near future; see Winch et al (2022). Furthermore, mirror stellar relics are expected to give rise to distinctive gravitationalwave signals from merger events, including mirror white dwarfs (Ryan & Radice 2022), mirror neutron stars (Hippert et al 2022(Hippert et al , 2023, and black holes with unusual masses sourced by ADM collapse (Pollack et al 2015;Shandera et al 2018;Singh et al 2021;Gurian et al 2022b;Fernandez et al 2024). simulated in Roy et al (2023) We now briefly summarize the most important points of the analyzes by Curtin & Setford (2020a, 2020b, which demonstrated the existence of observable optical and X-ray signatures of mirror stars.…”