Intensive monitoring of OJ 287

Astronomy and Astrophysics, 2008

Aims. The blazar OJ 287 had its biggest optical outburst in over 20 years. It occurred in October/November 2005 and was somewhat expected since similar outbursts had occurred at approximately 12 yr intervals since the early 1900s. However, a strict periodicity would have put the event nearly a year later. Here we ask whether the October/November 2005 outburst was indeed the expected 2006 outburst of OJ287. Did it follow the typical light curve behaviour of such events: a rapid initial rise in just over a week and a slower decay in the following months? Methods. In this study we use the extensive observations of The British Astronomical Association Variable Star Section, complemented by the data from The American Association of Variable Star Observers. We compare the 2005 outburst with the previous season's first peak of 1983. Results. We find that the beginning of the 2005 outburst occurred at 2005.76, a few weeks earlier than was reported previously. The timing of the outburst is consistent with the binary black hole model of Lehto and Valtonen. In accordance with this model, we find that the outburst's structural time scale is slower in 2005 than in 1983, while the 2005 outburst was fainter than the 1983 outburst, making the two outbursts about equal in energy. Thus it is quite reasonable to argue that the 2005 outburst was the expected first of the season in the optical light curve of OJ287.

The Astrophysical Journal, 2006

We report observations of the largest optical outburst in 20 years in the quasar OJ 287. In some ways it was expected, due to the well-known quasi-periodic 12 yr outburst cycle of OJ 287. In other ways the timing of the outburst was surprising, since calculations based on the periodicity were predicting such an outburst in late 2006. Here we point out that, in the precessing binary black hole model, first proposed by Sillanpää et al., and later refined by Lehto & Valtonen and Sundelius et al., the precession shifts the first outburst of each outburst season progressively to earlier times relative to the mean period. Thus, in this model, the timing of the outburst is quite acceptable, even if it was not predicted. The next test of the model comes in 2007 September when the second brightness peak is due. It may then be possible to detect the shortening of the binary period due to emission of gravitational waves from the system.

The Astrophysical Journal, 2009

The blazar OJ 287 has produced two major optical outburst events during the years [2005][2006][2007][2008]. These are the latest in a series of outbursts that have occurred repeatedly at 12 year intervals since early 1900s. It has been possible to explain the historical light curve fairly well by using a binary black hole model where the secondary black hole impacts the accretion disk of the primary twice during the 12 year orbital cycle. We will ask here how well does the latest light-curve fit with this model. We use a 10 million particle disk to model the accretion disk of the primary black hole. The rate of transfer of particles through the 10 Schwarzschild radius cylinder around the primary is followed. The secondary induces an inward flow through this surface. The inward flow rate is compared with the historical light curve as well as with the most recent observations reported in this paper. The observations have been carried out by using a number of small and medium size telescopes in different locations in order to ensure a dense light-curve coverage. The "inflow light curve" and the optical light curve of OJ 287 have a close resemblance to each other. It suggests that the tidally induced accretion flow is responsible for the main features of the optical light curve, with the exception of the quasi-periodic double peaks. It implies a close connection between the accretion disk and the jet where the optical synchrotron emission is presumably generated.

Galaxies

We report optical photometric and polarimetric observations of the blazar OJ 287 gathered during 2016/17. The high level of activity, noticed after the General Relativity Centenary flare, is argued to be part of the follow-up flares that exhibited high levels of polarization and originated in the primary black hole jet. We propose that the follow-up flares were induced as a result of accretion disk perturbations, travelling from the site of impact towards the primary SMBH. The timings inferred from our observations allowed us to estimate the propagation speed of these perturbations. Additionally, we make predictions for the future brightness of OJ 287.

Digitally scanned photographic plates from the Sonneberg Observatory, plate archives were used to obtain both V magnitudes and flux values of the blazar OJ 287, for the interval 1957-1978. These data were used to investigate the optical variability of OJ 287, by comparing it to the outburst times of three distinct binary black hole models given by Valtonen (2007). It was found that during this period OJ 287 was very optically active, with four sharp impact outbursts and one long tidal outburst. Evidence for outbursts beginning at 1957.07 and 1964.09 (which have previously not been observed), were obtained from this study, which are very close to the predicted times (1957.09 and 1964.10) of the 39.1 degree precession model by Valtonen (2007). Although this study does not prove or disprove any of the models, the optical variability during this period is best explained by the precessing binary black hole model. Keywords: Blazars: Specific: OJ 287; Binary Black Holes; Photographic Plates: Digitally Scanned.

Monthly Notices of the Royal Astronomical Society, 2016

We present recent optical photometric observations of the blazar OJ 287 taken during September 2015 -May 2016. Our intense observations of the blazar started in November 2015 and continued until May 2016 and included detection of the large optical outburst in December 2016 that was predicted using the binary black hole model for OJ 287. For our observing campaign, we used a total of 9 ground based optical telescopes of which one is in Japan, one is in India, three are in Bulgaria, one is in Serbia, one is in Georgia, and two are in the USA. These observations were carried out in 102 nights with a total of ∼ 1000 image frames in BVRI bands, though the majority were in the R band. We detected a second comparably strong flare in March 2016. In addition, we investigated multi-band flux variations, colour variations, and spectral changes in the blazar on diverse timescales as they are useful in understanding the emission mechanisms. We briefly discuss the possible physical mechanisms most likely responsible for the observed flux, colour and spectral variability.

Astrophysical Journal, 2000

The BL LacÈtype active galaxy OJ 287 exhibits a 12 year periodicity with a double-peaked maxima in its optical Ñux variations. Several models sought to explain this periodicity, the Ðrst one Ðrmly established in any active galactic nucleus (AGN), as a result of the orbital motion of a pair of supermassive black holes. In one class of models the orientation of the jets changes in a regular manner, and the optical Ñaring is due to a consequent increase in the Doppler boosting factor. In another class of models the optical Ñaring reÑects a true increase in luminosity, either due to an enhanced accretion during the pericenter passage or due to a collision between the secondary black hole and the accretion disk of the primary black hole. However, these models have been based solely on the optical data. Here we consider the full radio Ñux density monitoring data between 8 and 90 GHz from the Michigan, and Metsa hovi, Swedish-ESO Submillimeter Telescope AGN monitoring programs. We Ðnd that the radio Ñux density and polarization data, as well as the optical polarization data, indicate that the Ðrst of the two optical peaks is a thermal Ñare occurring in the vicinity of the black hole and the accretion disk, while the second one is a synchrotron Ñare originating in a shocked region down the jet. None of the proposed binary black hole models for OJ 287 o †ers satisfactory explanations for these observations. We suggest a new scenario, in which a secondary black hole penetrates the accretion disk of the primary during the pericenter passage, causing a thermal Ñare visible only in the optical regime. The pericenter passage enhances accretion into the primary black hole, leading to increased jet Ñow and formation of shocks down the jet. These become visible as standard radio and optical synchrotron Ñares roughly a year after the pericenter passage and are identiÐed with the second optical peaks. In addition to explaining the radio and the optical data, our model eliminates the need for a strong precession of the binary and for an ultramassive (º1010 primary black hole. If our interpretation is correct, the next periodic M _ ) optical Ñare, a thermal one, should occur around 2006 September 25. Nonthermal, simultaneous optical and radio Ñares should follow about a year later.

Workshop on Two …, 1996

During the OJ-94 campaign we have been concentrating mainly on two objects, OJ 287 an 3C 66A but we have a lot of data also on the BL Lac objects S5 0716+714 and AO 0235+164. In OJ 287 we observed the predicted outburst in the fall 1994. 3C 66A has been in the strong outburst all the time. On the other hand, AO 0235+164 has been very faint in all of our observations. S5 0716+174 has been very variable, like normally, but we can also see a huge outburst at the beginning of the year 1995. In this paper we will present the V-band (AO 0235+164 in R-band) light curves of these four objects as observed during our project.

Publications of the Astronomical Society of Japan, 2009

Suzaku observations of the blazar OJ 287 were performed in 2007 April 10 -13 and November 7 -9. They correspond to a quiescent and a flaring state, respectively. The X-ray spectra of the source can be well described with single power-law models in both exposures. The derived X-ray photon index and the flux density at 1 keV were found to be Γ = 1.65 ± 0.02 and S 1keV = 215 ± 5 nJy, in the quiescent state. In the flaring state, the source exhibited a harder X-ray spectrum (Γ = 1.50 ± 0.01) with a nearly doubled X-ray flux density S 1keV = 404 +6 −5 nJy. Moreover, significant hard X-ray signals were detected up to ∼ 27 keV. In cooperation with the Suzaku, simultaneous radio, optical, and very-high-energy γ-ray observations of OJ 287 were performed with the Nobeyama Millimeter Array, the KANATA telescope, and the MAGIC telescope, respectively. The radio and optical fluxes in the flaring state (3.04 ± 0.46 Jy and 8.93 ± 0.05 mJy at 86.75 Hz and in the V -band, respectively) were found to be higher by a factor of 2 -3 than those in the quiescent state (1.73 ±0.26 Jy and 3.03 ± 0.01 mJy at 86.75 Hz and in the V -band, respectively) . No notable γ-ray events were detected in either observation. The spectral energy distribution of OJ 287 indicated that the X-ray spectrum was dominated by inverse Compton radiation in both observations, while synchrotron radiation exhibited a spectral cutoff around the optical frequency. Furthermore, no significant difference in the synchrotron cutoff frequency was found between the quiescent and flaring states. According to a simple synchrotron self-Compton model, the change of the spectral energy distribution is due to an increase in the energy density of electrons with small changes of both the magnetic field strength and the maximum Lorentz factor of electrons.

Monthly Notices of the Royal Astronomical Society, 2017

We present a multiwavelength spectral and temporal analysis of the blazar OJ 287 during its recent activity between 2015 December and 2016 May, showing strong variability in the nearinfrared (NIR) to X-ray energies with detection at γ-ray energies as well. Most of the optical flux variations exhibit strong changes in polarization angle and degree. All the interband time lags are consistent with simultaneous emissions. Interestingly, on days with excellent data coverage in the NIR-UV bands, the spectral energy distributions (SEDs) show signatures of bumps in the visible-UV bands, never seen before in this source. The optical bump can be explained as accretion-disc emission associated with the primary black hole of mass ∼1.8 × 10 10 M while the little bump feature in the optical-UV appears consistent with line emission. Further, the broad-band SEDs extracted during the first flare and during a quiescent period during this span show very different γ-ray spectra compared to previously observed flare or quiescent spectra. The probable thermal bump in the visible seems to have been clearly present since 2013 May, as found by examining all available NIR-optical observations, and favours the binary supermassive black hole model. The simultaneous multiwavelength variability and relatively weak γ-ray emission that shows a shift in the SED peak is consistent with γ-ray emission originating from inverse Compton scattering of photons from the line emission that apparently contributes to the little blue bump.