# Accretion Disk Parameters determined from the great 2015 flare of OJ 287

## TL;DR

This paper refines the accretion disk parameters of OJ 287 based on the 2015 flare, predicts a 2019 superflare, and analyzes the emission mechanisms involved.

## Contribution

It updates the disk viscosity and accretion rate parameters and provides detailed predictions and analysis of flare emission regions.

## Key findings

- Viscosity parameter α = 0.26 ± 0.1
- Mass accretion rate ṁ = 0.08 ± 0.04 in Eddington units
- 2019 superflare expected to be observed simultaneously in infrared and optical

## Abstract

In the binary black hole model of OJ 287 the secondary black hole orbits a much more massive primary, and impacts on the primary accretion disk at predictable times. We update the parameters of the disk, the viscosity $\alpha$ and the mass accretion rate $\dot m$. We find $\alpha=0.26 \pm 0.1$ and $\dot m = 0.08 \pm 0.04$ in Eddington units. The former value is consistent with Coroniti (1981) and the latter with Marscher and Jorstad (2011). Predictions are made for the 2019 July 30 superflare in OJ 287. We expect that it will take place simultaneously at the Spitzer infrared channels as well as in the optical and that therefore the timing of the flare in optical can be accurately determined from Spitzer observations. We also discuss in detail the light curve of the 2015 flare and find that the radiating volume has regions where bremsstrahlung dominates as well as regions that radiate primarily in synchrotron radiation. The former region produces the unpolarised first flare while the latter region gives rise to a highly polarized second flare.