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ABSTRACT Supermassive black hole binaries (SMBHBs) are natural by-products of galaxy mergers and are expected to be powerful multimessenger sources. They can be powered by the accretion of matter and then radiate across the electromagnetic spectrum, much like normal active galactic nuclei (AGNs). Current electromagnetic observatories have a good chance of detecting and identifying these systems in the near future. However, precise observational indicators are needed to distinguish individual AGNs from SMBHBs. In this paper, we propose a novel electromagnetic signature from SMBHBs: non-thermal emission produced by the interaction between the jets ejected by the black holes. We study close SMBHBs, which accrete matter from a circumbinary disc and the mini-discs formed around each hole. Each black hole ejects a magnetically dominated jet in the direction of its spin through the Blandford–Znajek mechanism. We argue that in such a situation, the interaction between the jets can trigger strong magnetic reconnection events, where particles are accelerated and emit non-thermal radiation. Depending on whether the jets are aligned or misaligned, this radiation can have different periodicities. We model the evolution of the particles accelerated during the dual jet interaction and calculate their radiative output, obtaining spectra and providing estimates for the variability time-scales. We finally discuss how this emission compares with that of normal AGNs.
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Primordial Black Holes as Dark Matter
We investigate models in which a spectrum of black holes with Hawking temperature of order the radiation temperature at the beginning of the radiation dominated era can survive long enough to produce a matter dominated era at the observed crossover between matter and radiation in our universe. We nd that a suciently dense population of such black holes can indeed do so. The stronger observational constraint, that the black holes have lifetimes at least as long as the current age of the universe is harder to assess, because of black hole mergers during the matter dominated era. We then investigate whether the required densities and masses are consistent with the Holographic Space-time (HST) model of in ation. We nd that they are, but put mild constraints on the slow roll parameter = _H H2 in that model to be small. The bound is no stronger than the observational bound on the model's prediction for tensor uctuations. The required black hole density, at the reheat temperature, in a model with a single species of black hole, must be viewed as a quantum mechanical accident. In such a model, our universe exists because of a low probability quantum uctuation.
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- Award ID(s):
- 1914679
- PAR ID:
- 10185557
- Date Published:
- Journal Name:
- Letters in high energy physics
- ISSN:
- 2632-2714
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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