Tests of Einstein's general theory of relativity have mostly been carried out in weak gravitational fields where the space-time curvature effects are first-order deviations from Newton's theory. ...Binary pulsars provide a means of probing the strong gravitational field around a neutron star, but strong-field effects may be best tested in systems containing black holes. Here we report such a test in a close binary system of two candidate black holes in the quasar OJ 287. This quasar shows quasi-periodic optical outbursts at 12-year intervals, with two outburst peaks per interval. The latest outburst occurred in September 2007, within a day of the time predicted by the binary black-hole model and general relativity. The observations confirm the binary nature of the system and also provide evidence for the loss of orbital energy in agreement (within 10 per cent) with the emission of gravitational waves from the system. In the absence of gravitational wave emission the outburst would have happened 20 days later.
ABSTRACT
We present a comprehensive analysis of all XMM–Newton spectra of OJ 287 spanning 15 yr of X-ray spectroscopy of this bright blazar. We also report the latest results from our dedicated Swift ...UVOT and XRT monitoring of OJ 287, which started in 2015, along with all earlier public Swift data since 2005. During this time interval, OJ 287 was caught in extreme minima and outburst states. Its X-ray spectrum is highly variable and encompasses all states seen in blazars from very flat to exceptionally steep. The spectrum can be decomposed into three spectral components: Inverse Compton (IC) emission dominant at low-state, supersoft synchrotron emission that becomes increasingly dominant as OJ 287 brightens, and an intermediately-soft (Γx = 2.2) additional component seen at outburst. This last component extends beyond 10 keV and plausibly represents either a second synchrotron/IC component and/or a temporary disc corona of the primary supermassive black hole (SMBH). Our 2018 XMM–Newton observation, quasi-simultaneous with the Event Horizon Telescope observation of OJ 287, is well described by a two-component model with a hard IC component of Γx = 1.5 and a soft synchrotron component. Low-state spectra limit any long-lived accretion disc/corona contribution in X-rays to a very low value of Lx/LEdd < 5.6 × 10−4 (for MBH, primary = 1.8 × 1010 M⊙). Some implications for the binary SMBH model of OJ 287 are discussed.
On the masses of OJ287 black holes Valtonen, M. J; Ciprini, S; Lehto, H. J
Monthly notices of the Royal Astronomical Society,
21 November 2012, Letnik:
427, Številka:
1
Journal Article
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Abstract
Two multifrequency campaigns were carried out on OJ287 in 2005: in April when it was in its pre-outburst state, and in November during the main 12 yr cycle outburst. The wavelength coverage ...was from radio to X-rays. In the optical-to-ultraviolet range, the differential spectrum between the observations has a bremsstrahlung spectral shape, consistent with gas at 3 × 105 K temperature. Our result supports the hydrogen column density of the OJ287 host galaxy of ∼9.3 × 1020 cm−2, the average value found by Ghosh & Soundararajaperumal. The 3 × 105 K bremsstrahlung radiation was predicted in the binary black hole model of OJ287, and it arises from a hot bubble of gas which is torn off the accretion disc by the impact of the secondary. As this radiation is not Doppler boosted, the brightness of the outburst provides an estimate for the mass of the secondary black hole, ∼1.4 × 108 M⊙. In order to estimate the mass of the primary black hole, we ask what is the minimum mass ratio in a binary system which allows the stability of the accretion disc. By using particle simulations, we find that the ratio is ∼1.3 × 102. This makes the minimum mass of the primary ∼1.8 × 1010 M⊙, in agreement with the mass determined from the orbit solution, 1.84 × 1010 M⊙. With this mass value and the measured K magnitude of the bulge of the host galaxy of OJ287, the system lies almost exactly on the previously established correlation in the black hole mass versus K-magnitude diagram. It supports the extension of this correlation to brighter magnitudes and to more massive black holes than has been done previously.
ABSTRACT
We report detection of a very bright X-ray–UV–optical outburst of OJ 287 in 2020 April–June, the second brightest since the beginning of our Swift multiyear monitoring in late 2015. It is ...shown that the outburst is predominantly powered by jet emission. Optical–UV–X-rays are closely correlated, and the low-energy part of the XMM–Newton spectrum displays an exceptionally soft emission component consistent with a synchrotron origin. A much harder X-ray power-law component (Γx = 2.4, still relatively steep when compared to expectations from inverse Compton models) is detected out to 70 keV by NuSTAR. We find evidence for reprocessing around the Fe region, consistent with an absorption line. If confirmed, it implies matter in outflow at ∼0.1c. The multiyear Swift light curve shows multiple episodes of flaring or dipping with a total amplitude of variability of a factor of 10 in X-rays, and 15 in the optical–UV. The 2020 outburst observations are consistent with an after-flare predicted by the binary black hole model of OJ 287, where the disc impact of the secondary black hole triggers time-delayed accretion and jet activity of the primary black hole.
In its nearly regular cycle of outbursts the quasar OJ 287 is due for another outburst season in 2006-2010. The prediction for the exact timing depends on the adopted model. In the processing binary ...model of Lehto and Valtonen the timing depends on the time delay between the impact on the primary disk and the time when the impacted gas becomes optically thin. The time delay in turn depends on the properties of the accretion disk, the accretion rate, and the viscosity parameter a, which are not exactly known. We study the flexibility in timing provided by the uncertainties. In order to fix the model, two methods are used: the wobble of the jet, induced by the secondary, and the timing of the 1956 outburst, which has not been previously used. As a result, rather definite dates for the outbursts are obtained, which are different from a straightforward extrapolation of the past light curve. A new optical light curve with many new historical as well as recent points of observation have been put together and has been analyzed in order to reach these conclusions. Also, the high-frequency radio observations are found to agree with the jet wobble picture.
We identify a sample of 14 planetary nebulae in the nearby starburst disc galaxy NGC 253, using broad- and narrow-band imaging. A simple model of the stellar and dust layers in the galaxy shows that ...planetary nebula magnitudes are not statistically affected much by extinction. The luminosity function of the planetary nebulae is fitted with models accounting for dust, which leads to a distance to NGC 253 of μ0= 27.62+0.16−0.26 mag (d= 3.34+0.26−0.38 Mpc). This new estimate is found to be in agreement with the few existing distance estimates for this galaxy when they are all set to a common Large Magellanic Cloud distance of 18.50 mag. A weighted average of the most reliable distance estimates yields a distance of μ0= 27.7 ± 0.2 mag (d= 3.5 ± 0.2 Mpc).
In 1995, a binary black hole model was proposed for the quasar OJ287, where the smaller secondary black hole impacts the accretion disk of the primary black hole twice during its 12 yr orbit and ...causes a double peak of optical outbursts. The model predicted four major outbursts and one minor outburst during the period 1996-2010. All five have now been observed. In this paper, we ask how accurate the predictions were. We use the latest optical observations from Tuorla Observatory and the KVA telescope at La Palma together with previously published data to construct a light curve for this period. We average the data in 0.04 yr bins, and subtract the observed flux from the 1995 model flux at each bin. We find that the residuals are small: they are well described by random noise of amplitude 1.4 mJy. This level is small compared with the amplitudes of the major outbursts, 5-7 mJy. Ignoring the noise, the binary model explains the optical data remarkably well.
We derive new solutions for the binary black hole model of OJ 287, using the 2005 November outburst as one of the fixed points. Previous models have used the 1994 September outburst, which is in many ...ways ill defined and leads to considerable uncertainty in the orbit. In addition, the inherent asymmetry in the double outburst structure, due to the vantage point of the observer lying to one side of the accretion disk, has been included in the models for the first time. The disk bending is calculated using a million-particle disk as a model for the accretion disk. In addition, allowance is made for the possibility of different values of disk thickness. The parameters of the system to be determined are the orbital period, fixed by the separation of the 1947.30 and 1983.00 outbursts; the orientation of the major axis of the orbit at a given time, fixed by the 1972.99 outburst; the time delay factor, which is a function of the disk thickness, fixed by the 2005.82 outburst; and the precession rate of the binary, fixed by the 1913.02 outburst. A unique solution is found for both the case of gravitational radiation and that of no gravitational radiation. The 2007 September outburst begins 2007 September 9-16 in the former models and 2007 October 8 in the latter model. The 3 week difference will be easily resolved in future observations, and thus the emission of gravitational radiation can be indirectly measured.
ABSTRACT
We report results from our ongoing project MOMO (Multiwavelength Observations and Modelling of OJ 287). In this latest publication of a sequence, we combine our Swift UVOT–XRT and Effelsberg ...radio data (2.6–44 GHz) between 2019 and 2022.04 with public SMA data and gamma-ray data from the Fermi satellite. The observational epoch covers OJ 287 in a high state of activity from radio to X-rays. The epoch also covers two major events predicted by the binary supermassive black hole (SMBH) model of OJ 287. Spectral and timing analyses clearly establish: a new UV–optical minimum state in 2021 December at an epoch where the secondary SMBH is predicted to cross the disc surrounding the primary SMBH; an overall low level of gamma-ray activity in comparison to pre-2017 epochs; the presence of a remarkable, long-lasting UV–optical flare event of intermediate amplitude in 2020–2021; a high level of activity in the radio band with multiple flares; and particularly a bright, ongoing radio flare peaking in 2021 November that may be associated with a gamma-ray flare, the strongest in 6 yr. Several explanations for the UV–optical minimum state are explored, including the possibility that a secondary SMBH launches a temporary jet, but the observations are best explained by variability associated with the main jet.
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