A helical jet model for OJ287

Abstract

Context. The quasar OJ287 has been under observation for over 120 years. The quasi-periodic nature of its optical light curve has led to a binary black hole model as a common explanation of the quasar. The radio jet of OJ287 has been under investigation for a shorter time, about 30 years. It has a complicated structure that varies dramatically over a time scale of a few years. Aims. Here we propose that this structure arises from a helical jet being observed from a small and varying viewing angle. The viewing angle variation is taken to be in tune with the binary orbital motion. Methods. We calculated the effect of the secondary black hole on the inner edge of the accretion disk of the primary using particle simulations. We presumed that the axis of the helix is perpendicular to the disk. We then followed the jet motion on its helical path and projected the jet to the sky plane. This projection was compared with observations both at mm waves and cm waves. Results. We find that this model reproduces the observations well if the changes in the axis of the conical helix propagate outwards with a relativistic speed of about 0.85c. In particular, this model explains at the same time the long-term optical brightness variations as varying Doppler beaming in a component close to the core, i.e., at parsec scale in real linear distance, while the mm and cm radio jet observations are explained as being due to jet wobble at much larger (100 parsec scale) distances from the core.

The Unique Blazar OJ 287 and Its Massive Binary Black Hole Central Engine

“…In contrast, the BBH impact model of Lehto & Valtonen [8] explains most of the features present in the optical LC of OJ 287 like, sharp rise of flares, decrease in degree of polarisation during flares, the long term periodic variations etc. This model can also explain the features present in high frequency radio observations of the jet of OJ 287 [31][32][33].…”

“…In this model, the secondary influences the orientation of the accretion disk, which is presumably connected to the jet in a way that causes a jet wobble in tune with the disk variations. This provides a good description for the background level variation in the time scale of decades [32]. However, attempts to connect this mechanism with flares have failed.…”

“…Additional investigations are also being pursued to substantiate the presence of a 1.8 billion solar mass BH in OJ 287. This includes an effort to verify from observations whether the host galaxy of OJ 287 follows the established BH mass-bulge luminosity correlation [30] and employing BH binary scenario to model temporal variations of the jet position angle using high-frequency radio data sets [31][32][33].…”

The Study of Radio Flux Density Variations of the Quasar OJ 287 by the Wavelet and the Singular Spectrum Methods

“…The mass of the central supermassive black hole is 18×10 9 solar masses (Valtonen et al 2008). A precessing jet model that assumes the existence of helical Kelvin-Helmholtz instability in the jet flow may explain the variability of the object (Hardee 2000;Mignone et al 2010;Valtonen & Pihajoki 2013).…”

Radio evidence for binary super massive black holes

“…For example, OJ287 has shown quasi periodic variability with a 12 year cycle which was modelled by Valtonen et al (2008) as a precessing binary black hole. Further observations, including observations of the changes in the resolved jet structure (Valtonen & Pihajoki 2013), have not directly confirmed initial predictions but have resulted in more complex models involving black hole spin and helical jets.…”