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ATel 9489: The OJ287 blazar in a flaring state



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ATel 8667: A new optical flare in the OJ287 blazar 

 



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Title: Black hole binary OJ287 as a testing platform for general relativity
Authors: M. J. Valtonen, A. Gopakumar, S. Mikkola, K. Wiik, H. J. Lehto

The blazar OJ287 is the most promising (and the only) case for an extragalactic binary black hole system in-spiralling under the action of gravitational radiation reaction. At present, though it is not possible to directly observe the binary components, it is possible to observe the jet emanating form the primary black hole. We argue that the orbital motion of the secondary black hole is reflected in the wobble of the jet and demonstrate that the wobble is orbital position dependent. The erratic wobble of the jet, reported in Agudo et al. (2012), is analysed by taking into account the binary nature of the system and we find that the erratic component of jet wobble is very small.

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Title: On the masses of OJ287 black holes
Authors: M.J. Valtonen, S. Ciprini, H.J. Lehto

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-UV range the differential spectrum between the observations has a bremsstrahlung spectral shape, consistent with gas at 3 x 10^{5}K temperature. Our result supports the hydrogen column density of the OJ287 host galaxy of \sim9.3 x 10^{20} cm^{-2}, the average value found by Gosh & Soundararajaperumal. The 3 x 10^{5}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, \sim1.4 x 10^{8} solar mass. 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 \sim1.3 x 10^{2}. This makes the minimum mass of the primary \sim1.8 x 10^{10} solar mass, in agreement with the mass determined from the orbit solution, 1.84 x 10^{10} solar mass. 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 vs. K-magnitude diagramme. It supports the extension of this correlation to brighter magnitudes and to more massive black holes than has been done previously.

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BL Lacertae Object OJ287
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Title: Erratic Jet Wobbling in the BL Lacertae Object OJ287 Revealed by Sixteen Years of 7mm VLBA Observations
Authors: Ivan Agudo, Alan P. Marscher, Svetlana G. Jorstad, Jose L. Gomez, Manel Perucho, B. Glenn Piner, Maria Rioja, Richard Dodson

We present the results from an ultra-high-resolution 7mm Very Long Baseline Array (VLBA) study of the relativistic jet in the BL Lacertae object OJ287 from 1995 to 2011 containing 136 total intensity images. Analysis of the image sequence reveals a sharp jet-position-angle swing by >100 deg. during [2004,2006], as viewed in the plane of the sky, that we interpret as the crossing of the jet from one side of the line of sight to the other during a softer and longer term swing of the inner jet. Modulating such long term swing, our images also show for the first time a prominent erratic wobbling behaviour of the innermost ~0.4mas of the jet with fluctuations in position angle of up to ~40 deg. over time scales ~2yr. This is accompanied by highly superluminal motions along non-radial trajectories, which reflect the remarkable non-ballistic nature of the jet plasma on these scales. The erratic nature and short time scales of the observed behaviour rules out scenarios such as binary black hole systems, accretion disk precession, and interaction with the ambient medium as possible origins of the phenomenon on the scales probed by our observations, although such processes may cause longer-term modulation of the jet direction. We propose that variable asymmetric injection of the jet flow; perhaps related to turbulence in the accretion disk; coupled with hydrodynamic instabilities, leads to the non-ballistic dynamics that cause the observed non-periodic changes in the direction of the inner jet.

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Title: A massive binary black-hole system in OJ287 and a test of general relativity
Authors: M. J. Valtonen, H. J. Lehto, K. Nilsson, J. Heidt, L. O. Takalo, A. Sillanpää, C. Villforth, M. Kidger, G. Poyner, T. Pursimo, S. Zola, J. H. Wu, X. Zhou, K. Sadakane, M. Drozdz, D. Koziel, D. Marchev, W. Ogloza, C. Porowski, M. Siwak, G. Stachowski, M. Winiarski, V. P. Hentunen, M. Nissinen, A. Liakos, S. Dogru

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 OJ287. This quasar shows quasi-periodic optical outbursts at 12 yr 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 twenty days later.

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Astronomers have weighed the biggest known black hole in the Universe.
The monster celestial object is 18 billion times more massive than our own Sun, says a team from Finland - six times larger than the previous record.
The object, called OJ287, is orbited by a smaller black hole, which allowed its mass to be measured very accurately.

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Most massive known black hole
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The most massive known black hole in the universe has been discovered, weighing in with the mass of 18 billion Suns. Observing the orbit of a smaller black hole around this monster has allowed astronomers to test Einstein's theory of general relativity with stronger gravitational fields than ever before.
The black hole is about six times as massive as the previous record holder and in fact weighs as much as a small galaxy. It lurks 3.5 billion light years away, and forms the heart of a quasar called OJ287. A quasar is an extremely bright object in which matter spiralling into a giant black hole emits copious amounts of radiation.

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Quasar OJ287
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Quasar OJ287.kmz
Google Sky file (1kb, kmz)

Position(2000): RA 08:54:48.8 Dec +20:06:31



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The most massive black hole in the universe has been measured at being 18 billion solar masses.
The binary black hole at the centre of quasar OJ287, which is located 3.5 billion light-years away in the constellation Cancer, has a regular pulsing light signal with two major pulses every 12 years.
The last two pulses were observed in the year 1994-1995, and the first one of the next pulses was observed in 2005. The astronomers predicted the next pulse would come on Sept. 13, 2007.
The details were revealed by astronomers at a meeting of the American Astronomical Society.

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Position(2000): RA 08:54:48.8 Dec +20:06:31

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