Abstract
Our project MOMO (Multiwavelength observations and modeling of OJ 287) consists of dedicated, dense, long-term flux and spectroscopic monitoring, and deep follow-up observations of the blazar OJ 287 at >13 frequencies from the radio to the X-ray band since late 2015. In particular, we are using Swift to obtain optical-UV-X-ray spectral energy distributions (SEDs) and the Effelsberg telescope to obtain radio measurements between 2 and 40 GHz. MOMO is the densest long-term monitoring of OJ 287 involving X-rays and broad-band SEDs. The theoretical part of the project aims at understanding jet and accretion physics of the blazar central engine in general and the supermassive binary black hole scenario in particular. Results are presented in a sequence of publications and so far included: detection and detailed analysis of the bright 2016/17 and 2020 outbursts and the long-term light curve; Swift, XMM, and NuSTAR spectroscopy of the 2020 outburst around maximum; and interpretation of selected events in the context of the binary black hole scenario of OJ 287 (papers I–IV). Here, we provide a description of the project MOMO, a summary of previous results, the latest results, and we discuss future prospects.
Highlights
We have presented a description of the project MOMO that aims at understanding blazar physics and binary black hole physics of OJ 287 during its recent evolution
Swift and the Effelsberg radio telescope play a central role in this project and we have used both to obtain measurements of OJ 287 at >13 frequencies, along with deeper follow-up spectroscopy from the optical to X-rays in outburst or deep minima states
Ib, [31]); the bright, super-soft, non-thermal 2020 outburst—interpreted as possible binary after-flare—with its exceptional spectral components measured with Swift, XMM-Newton, and NuSTAR; two decades of XMM-Newton spectroscopy establishing OJ
Summary
Blazars are characterized by their powerful jets of relativistic particles that are launched in the immediate vicinity of the supermassive black holes (SMBHs) at their centers [1]. The one at lower energies peaks between the sub-mm and EUV band and sometimes extends into the soft X-ray regime It is explained as synchrotron radiation from a population of relativistic electrons that form the jet. The second hump peaks in the hard X-ray and/or γ-ray regime It is usually explained as inverse Compton (IC) radiation from a population of photons that scatter off the jet electrons. Coalescing supermassive binary black holes (SMBBHs), formed in galaxy mergers, are expected to be the loudest sources of low-frequency gravitational waves (GWs) in the Universe [5] They play a key role in galaxy/SMBH formation and evolution scenarios. Given their well-covered light curves and large-scale jets, blazars are well suited for a search of small-seperation SMBBHs, and many of the spatially unresolved candidates have been found in blazars [6]
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