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Dingding Yang - One of the best experts on this subject based on the ideXlab platform.
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experimental research into the relationship between initial gas release and coal gas Outbursts
Journal of Natural Gas Science and Engineering, 2018Co-Authors: Dingding Yang, Chaojie Wang, Yujia Chen, Jun Tang, Xiaowei Li, Chenglin Jiang, Chaojie ZhangAbstract:Abstract Coal and gas Outbursts are a rapid and powerful energy-releasing process. The damage to coal and the release of gas in the initial stage play key roles in the occurrence of Outbursts. Existing studies have mainly focused on the gas desorption processes in coal under specific conditions such as particle size, specified mass and exposure time of pulverized coal. However, these studies have focused less on the gas release during the initial stage, and the quantitative relationship between the Outburst risk level and the test results. Seven coal samples with different metamorphic degrees were chosen for use in Outburst simulation experiments to investigate trends in gas release from pulverized coal in the presence of N 2 and CO 2 . The results demonstrate a strong correlation between the gas release capacity during the first 10 s and natural desorption gas content of the onset of coal exposure during the first 120 min. In general, the higher the gas content, the larger the released gas volume, and thus the larger the limiting amount of desorptive gas. The gas release from an Outburst coal sample is larger than that from a non-Outburst coal sample within the first 10 s. There is a good linear relationship between the initial volume of released gas (in the first 10 s) and the initial expansion energy of released gas (IEERG), which can reflect the risk of coal Outburst. Thus, according to the Outburst critical value (42.98 mJ/g) of IEERG, the critical value of initial volume of released gas could be calculated to be 1.113 cm 3 /g. The results can provide a reference for further study of the effect of gas on Outbursts and the investigation of coal and gas Outbursts disasters.
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The correlation between dynamic phenomena of boreholes for Outburst prediction and Outburst risks during coal roadways driving
Fuel, 2018Co-Authors: Chaojie Wang, Shengqiang Yang, Dingding Yang, Jiang ChenglinAbstract:Abstract Coal and gas Outburst accidents occurring in underground coal mines generally cause great casualties and economic losses, especially in construction areas of coal seams where the Outburst risks are not accurately evaluated. Therefore, accurately identifying the Outburst risks of coal seams is necessary and critical to prevent and control Outbursts. In order to improve the prediction accuracy for Outbursts in working faces of coal roadways, a self-designed drilling device that can simulate the in-situ Outburst prediction of coal roadways was used in this study. We used the coal samples with different coal ranks to adsorb CO 2 and N 2 with different pressures in the laboratory, so as to simulate the coal seams with different Outburst risks. Finally, boreholes for predicting the Outburst risk were drilled in the simulated coal seams to study the correlation between common dynamic phenomena (e.g. gas and coal being ejected from the borehole (GCEB) and drill pipe being stuck by coal mass in the borehole (DPSC)) and Outburst risks. The results show that the greater the Outburst risks of coal seams, the more frequent the occurrence of GCEB and DPSC is. The GCEB phenomenon for Outburst prediction is attributed to small-sized coal and gas Outbursts in boreholes, while the occurrence of DPSC phenomenon does not affirm that there definitely are Outburst risks on working faces. The DPSC phenomenon indicating Outburst risks is generally accompanied with GCEB, which form a linkage system and are triggered successively.
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line prediction technology for forecasting coal and gas Outbursts during coal roadway tunneling
Journal of Natural Gas Science and Engineering, 2016Co-Authors: Jun Tang, Yujia Chen, Xiaowei Li, Chenglin Jiang, Gongda Wang, Dingding YangAbstract:Abstract The advantages and disadvantages of existing methods for predicting coal and gas Outbursts in coal roadways were analyzed, and the primary factors influencing coal and gas Outbursts, including the expansion energy of the initially released gases, were studied. To this end, a theoretical formula for calculating the amount of gas released from boreholes during drilling was deduced. In addition, it was determined that the gas emission per unit borehole length was related to the ground stress, gas pressure, and coal strength around the borehole during drilling. By collecting these continuously released gases from boreholes during drilling, that is, by adopting line prediction technology, the influence of those parameters (ground stress, gas pressure, coal strength) on the Outburst process can be determined, and the Outburst hazard can be predicted. To test this approach, a specially developed line prediction device was applied to the No. 3 coal seam of the Xinyuan coal mine, Shanxi Province, China. The test results demonstrate that the gas emissions per meter of borehole, QLm, measured by the line prediction technique differed between Outburst and non-Outburst samples. Additionally, compared with existing indices used for predicting coal and gas Outbursts in coal roadways, including K1 and Smax, the line prediction technique was more sensitive and could reflect the Outburst hazard in front of working faces more accurately.
D Gotz - One of the best experts on this subject based on the ideXlab platform.
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an alternative hypothesis for the Outburst mechanism in supergiant fast x ray transients the case of igr j11215 5952
Astronomy and Astrophysics, 2007Co-Authors: L Sidoli, P Romano, S Mereghetti, A Paizis, S Vercellone, V Mangano, D GotzAbstract:Context. The physical mechanism responsible for the short Outbursts in a recently recognised class of high mass X-ray binaries, the supergiant fast X-ray transients (SFXTs), is still unknown. Two main hypotheses have been proposed to date: the sudden accretion by the compact object of small ejections originating in a clumpy wind from the supergiant donor, or Outbursts produced at (or near) the periastron passage in wide and eccentric orbits, to explain the low (∼10 32 erg s −1 ) quiescent emission. Neither proposed mechanisms explain the whole phenomenology of these sources. IGR J11215-5952, discovered in April 2005 by the INTEGRAL satellite, is a SFXT which undergoes an Outburst every 329 days, a periodicity likely associated with the orbital period of the binary system. Aims. We propose a new explanation for the Outburst mechanism, based on the X-ray observations of the unique SFXT known to display periodic Outbursts, IGR J11215-5952. Methods. We performed three Target of Opportunity (ToO) observations with Swift, XMM-Newton and INTEGRAL at the time of the fifth Outburst, expected on 2007 February 9. Swift observations of the February 2007 Outburst have been reported elsewhere. Another ToO with Swift was performed in July 2007, to monitor the supposed “apastron” passage. Results. XMM-Newton observed the source on 2007 February 9, for 23 ks, at the peak of the Outburst, while INTEGRAL started the observation two days later, failing to detect the source, which had already undergone the decaying phase of the fast Outburst. XMM-Newton data show large variability, with a bright flare at the beginning of the observation (lasting about 1 h), followed by a lower intensity phase (about one order of magnitude fainter) with a large variability as well as low level flaring activity. The spin periodicity discovered by RXTE is confirmed, and a spin-phase spectral variability is observed and studied in detail. The Swift campaign performed in July 2007 reveals a second Outburst on 2007 July 24, as bright as that observed about 165 days before. Conclusions. The new X-ray observations allow us to propose an alternative hypothesis for the Outburst mechanism in SFXTs, linked to the possible presence of a second wind component, in the form of an equatorial disc from the supergiant donor. We discuss the applicability of the model to the short Outburst durations of all other SFXTs, where a clear periodicity in the Outbursts has not been found yet. The new Outburst from IGR J11215–5952 observed in July suggests that the true orbital period is ∼165 days, instead of 329 days, as previously thought.
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an alternative hypothesis for the Outburst mechanism in supergiant fast x ray transients the case of igr j11215 5952
arXiv: Astrophysics, 2007Co-Authors: L Sidoli, P Romano, S Mereghetti, A Paizis, S Vercellone, V Mangano, D GotzAbstract:(ABRIDGED)- The physical mechanism responsible for the short Outbursts in a recently recognized class of High Mass X-ray Binaries, the Supergiant Fast X-ray Transients (SFXTs), is still unknown. Two main hypotheses have been proposed to date: the sudden accretion by the compact object of small ejections originating in a clumpy wind from the supergiant donor, or Outbursts produced at (or near) the periastron passage in wide and eccentric orbits, in order to explain the low (1E32 erg/s) quiescent emission.Neither proposed mechanisms seem to explain the whole phenomenology of these sources. Here we propose a new explanation for the Outburst mechanism, based on new X-ray observations of the unique SFXT known to display periodic Outbursts, IGRJ11215-5952. We performed three Target of Opportunity observations with Swift, XMM-Newton and INTEGRAL at the time of the fifth Outburst, expected on 2007 February 9. Swift observations of the February 2007 Outburst have been reported elsewhere. Another ToO with Swift was performed in July 2007, in order to monitor the supposed ``apastron'' passage. A second unexpected Outburst was discovered on 2007 July 24, after about 165 days from the February 2007 Outburst. The new X-ray observations allow us to propose an alternative hypothesis for the Outburst mechanism in SFXTs, linked to the possible presence of a second wind component,in the form of an equatorial disk from the supergiant donor. We discuss the applicability of the model to the short Outburst durations of all other SFXTs, where a clear periodicity in the Outbursts has not been found yet. The new Outburst from IGRJ11215-5952 observed in July suggests that the true orbital period is ~165days, instead of 329days, as previously thought.
K Nilsson - One of the best experts on this subject based on the ideXlab platform.
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Measuring black hole spin in OJ287
Celestial Mechanics and Dynamical Astronomy, 2010Co-Authors: M. J. Valtonen, K Nilsson, H J Lehto, S. Mikkola, T. Hyvönen, D. Merritt, A. Gopakumar, H. Rampadarath, R. Hudec, M. BastaAbstract:We model the binary black hole system OJ287 as a spinning primary and a non-spinning secondary. It is assumed that the primary has an accretion disk which is impacted by the secondary at specific times. These times are identified as major Outbursts in the light curve of OJ287. This identification allows an exact solution of the orbit, with very tight error limits. Nine Outbursts from both the historical photographic records as well as from recent photometric measurements have been used as fixed points of the solution: 1913, 1947, 1957, 1973, 1983, 1984, 1995, 2005 and 2007 Outbursts. This allows the determination of eight parameters of the orbit. Most interesting of these are the primary mass of $${1.84\cdot 10^{10}M_\odot}$$ , the secondary mass $${1.40\cdot 10^{8} M_\odot}$$ , major axis precession rate 39°.1 per period, and the eccentricity of the orbit 0.70. The dimensionless spin parameter is 0.28 ± 0.01 (1 sigma). The last parameter will be more tightly constrained in 2015 when the next Outburst is due. The Outburst should begin on 15 December 2015 if the spin value is in the middle of this range, on 3 January 2016 if the spin is 0.25, and on 26 November 2015 if the spin is 0.31. We have also tested the possibility that the quadrupole term in the post-Newtonian equations of motion does not exactly follow Einstein’s theory: a parameter q is introduced as one of the 8 parameters. Its value is within 30% (1 sigma) of the Einstein’s value q = 1. This supports the no-hair theorem of black holes within the achievable precision. We have also measured the loss of orbital energy due to gravitational waves. The loss rate is found to agree with Einstein’s value with the accuracy of 2% (1 sigma). There is a possibility of improving the accuracy of both quantities using the exact timing of the Outburst on 21 July 2019. Because of closeness of OJ287 to the Sun (8–12°), the observations would be best carried out by a telescope in space.
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Measuring black hole spin in OJ287
Celestial Mechanics and Dynamical Astronomy, 2010Co-Authors: M. J. Valtonen, K Nilsson, H J Lehto, S. Mikkola, T. Hyvönen, D. Merritt, A. Gopakumar, H. Rampadarath, R. Hudec, M. BastaAbstract:We model the binary black hole system OJ287 as a spinning primary and a non-spinning secondary. It is assumed that the primary has an accretion disk which is impacted by the secondary at specific times. These times are identified as major Outbursts in the light curve of OJ287. This identification allows an exact solution of the orbit, with very tight error limits. Nine Outbursts from both the historical photographic records as well as from recent photometric measurements have been used as fixed points of the solution: 1913, 1947, 1957, 1973, 1983, 1984, 1995, 2005 and 2007 Outbursts. This allows the determination of eight parameters of the orbit. Most interesting of these are the primary mass of , the secondary mass , major axis precession rate 39°.1 per period, and the eccentricity of the orbit 0.70. The dimensionless spin parameter is 0.28 ± 0.01 (1 sigma). The last parameter will be more tightly constrained in 2015 when the next Outburst is due. The Outburst should begin on 15 December 2015 if the spin value is in the middle of this range, on 3 January 2016 if the spin is 0.25, and on 26 November 2015 if the spin is 0.31. We have also tested the possibility that the quadrupole term in the post-Newtonian equations of motion does not exactly follow Einstein's theory: a parameter is introduced as one of the 8 parameters. Its value is within 30% (1 sigma) of the Einstein's value = 1. This supports the of black holes within the achievable precision. We have also measured the loss of orbital energy due to gravitational waves. The loss rate is found to agree with Einstein's value with the accuracy of 2% (1 sigma). There is a possibility of improving the accuracy of both quantities using the exact timing of the Outburst on 21 July 2019. Because of closeness of OJ287 to the Sun (8–12°), the observations would be best carried out by a telescope in space.
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a massive binary black hole system in oj 287 and a test of general relativity
Nature, 2008Co-Authors: Mauri Valtonen, Mark R. Kidger, L. O. Takalo, A. Sillanpää, K Nilsson, H J Lehto, J Heidt, C Villforth, G Poyner, Tapio PursimoAbstract:Black holes are firmly established in astronomy and in the public imagination. Yet the concept still depends on the assumption that Einstein's general theory of relativity is the correct theory of gravitation. Tests of general relativity in a strong gravitational field are best conducted in systems containing black holes. Valtonen et al. report such a test in a close binary system of two proposed black holes in the quasar OJ 287. This quasar shows quasiperiodic optical Outbursts at 12-year intervals, with two Outburst peaks per interval. The latest Outburst in September 2007 was within a day of the time predicted by the binary black hole model and general relativity. Tests of Einstein's general theory of relativity in a strong gravitational field may be best conducted in systems containing black holes. Such a test in a close binary system of two proposed black holes in the quasar OJ287 is reported. 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 the general relativity. 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 theory1,2,3,4,5,6. Binary pulsars4 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 holes7,8. 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 interval9,10. The latest Outburst occurred in September 2007, within a day of the time predicted by the binary black-hole model and general relativity11. 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 system12. In the absence of gravitational wave emission the Outburst would have happened 20 days later13.
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The light curve of OJ 287
1999Co-Authors: A. Sillanpää, Jose Antonio De Diego, J. N. González-pérez, T. Mahoney, Harry Lehto, Jose Miguel Rodriguez-espinosa, Mark R. Kidger, L. O. Takalo, K Nilsson, P. BoltwoodAbstract:During the OJ-94 campaign for blazar OJ 287 we have obtained the best ever ohserved optical light curve for any extragalactic object. We have monitored this blazar since fall 1993 and have collected over 2000 optical photometric observations. The light curve shows continuous activity down to timescales of tens of minutes, with amplitudes ranging from 0.1 to 2 magnitudes. The fastest observed activity was a 1.2 magnitude drop in less than a day and a 0.5 magnitude brightening in five hours. 1.) Introduction OJ 287 is one of the best observed blazars. Its historical light curve goes back about 100 years; this historical light curve shows several Outbursts, occurring at a period of 11.6 years (Sillanpaa et al. 1988). This periodicity has been confirmed later by Kidger et al. (1992) and Babadzhanyants et al. (1992) (see also Takalo (1994) and references therein). The last, Outburst occured during the winter of 1982/83. Sillanpaa et al. (1988) modelled these periodic Outbursts using a binary black hole model and predicted that the next should occur during summer/fall 1994. A large international monitoring campaign has been organized to check if this Outburst really happens and, at the same time, to collect a large data base for a few blazars, in order to get a better understanding of the physics of these objects. 2.) Observations The main idea and strategy of all the observations has been to get as good time coverage as possible so as not to lose any important Outburst of OJ 287 during our campaign. Table 1 shows the basic information for the telescopes and instruments used in the optical monitoring.
P Romano - One of the best experts on this subject based on the ideXlab platform.
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an alternative hypothesis for the Outburst mechanism in supergiant fast x ray transients the case of igr j11215 5952
Astronomy and Astrophysics, 2007Co-Authors: L Sidoli, P Romano, S Mereghetti, A Paizis, S Vercellone, V Mangano, D GotzAbstract:Context. The physical mechanism responsible for the short Outbursts in a recently recognised class of high mass X-ray binaries, the supergiant fast X-ray transients (SFXTs), is still unknown. Two main hypotheses have been proposed to date: the sudden accretion by the compact object of small ejections originating in a clumpy wind from the supergiant donor, or Outbursts produced at (or near) the periastron passage in wide and eccentric orbits, to explain the low (∼10 32 erg s −1 ) quiescent emission. Neither proposed mechanisms explain the whole phenomenology of these sources. IGR J11215-5952, discovered in April 2005 by the INTEGRAL satellite, is a SFXT which undergoes an Outburst every 329 days, a periodicity likely associated with the orbital period of the binary system. Aims. We propose a new explanation for the Outburst mechanism, based on the X-ray observations of the unique SFXT known to display periodic Outbursts, IGR J11215-5952. Methods. We performed three Target of Opportunity (ToO) observations with Swift, XMM-Newton and INTEGRAL at the time of the fifth Outburst, expected on 2007 February 9. Swift observations of the February 2007 Outburst have been reported elsewhere. Another ToO with Swift was performed in July 2007, to monitor the supposed “apastron” passage. Results. XMM-Newton observed the source on 2007 February 9, for 23 ks, at the peak of the Outburst, while INTEGRAL started the observation two days later, failing to detect the source, which had already undergone the decaying phase of the fast Outburst. XMM-Newton data show large variability, with a bright flare at the beginning of the observation (lasting about 1 h), followed by a lower intensity phase (about one order of magnitude fainter) with a large variability as well as low level flaring activity. The spin periodicity discovered by RXTE is confirmed, and a spin-phase spectral variability is observed and studied in detail. The Swift campaign performed in July 2007 reveals a second Outburst on 2007 July 24, as bright as that observed about 165 days before. Conclusions. The new X-ray observations allow us to propose an alternative hypothesis for the Outburst mechanism in SFXTs, linked to the possible presence of a second wind component, in the form of an equatorial disc from the supergiant donor. We discuss the applicability of the model to the short Outburst durations of all other SFXTs, where a clear periodicity in the Outbursts has not been found yet. The new Outburst from IGR J11215–5952 observed in July suggests that the true orbital period is ∼165 days, instead of 329 days, as previously thought.
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an alternative hypothesis for the Outburst mechanism in supergiant fast x ray transients the case of igr j11215 5952
arXiv: Astrophysics, 2007Co-Authors: L Sidoli, P Romano, S Mereghetti, A Paizis, S Vercellone, V Mangano, D GotzAbstract:(ABRIDGED)- The physical mechanism responsible for the short Outbursts in a recently recognized class of High Mass X-ray Binaries, the Supergiant Fast X-ray Transients (SFXTs), is still unknown. Two main hypotheses have been proposed to date: the sudden accretion by the compact object of small ejections originating in a clumpy wind from the supergiant donor, or Outbursts produced at (or near) the periastron passage in wide and eccentric orbits, in order to explain the low (1E32 erg/s) quiescent emission.Neither proposed mechanisms seem to explain the whole phenomenology of these sources. Here we propose a new explanation for the Outburst mechanism, based on new X-ray observations of the unique SFXT known to display periodic Outbursts, IGRJ11215-5952. We performed three Target of Opportunity observations with Swift, XMM-Newton and INTEGRAL at the time of the fifth Outburst, expected on 2007 February 9. Swift observations of the February 2007 Outburst have been reported elsewhere. Another ToO with Swift was performed in July 2007, in order to monitor the supposed ``apastron'' passage. A second unexpected Outburst was discovered on 2007 July 24, after about 165 days from the February 2007 Outburst. The new X-ray observations allow us to propose an alternative hypothesis for the Outburst mechanism in SFXTs, linked to the possible presence of a second wind component,in the form of an equatorial disk from the supergiant donor. We discuss the applicability of the model to the short Outburst durations of all other SFXTs, where a clear periodicity in the Outbursts has not been found yet. The new Outburst from IGRJ11215-5952 observed in July suggests that the true orbital period is ~165days, instead of 329days, as previously thought.
Mauri Valtonen - One of the best experts on this subject based on the ideXlab platform.
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OJ 287 binary black hole system
arXiv: High Energy Astrophysical Phenomena, 2011Co-Authors: Mauri Valtonen, Stefano CipriniAbstract:The light curve of the quasar OJ 287 extends from 1891 up today without major gaps. Here we summarize the results of the 2005 - 2010 observing campaign. The main results are the following: (1) The 2005 October optical Outburst came at the expected time, thus confirming the general relativistic precession in the binary black hole system. This result disproved the model of a single black hole system with accretion disk oscillations, as well as several toy models of binaries without relativistic precession. In the latter models the main Outburst would have been a year later. (2) The nature of the radiation of the 2005 October Outburst was expected to be bremsstrahlung from hot gas at the temperature of $3\times 10^{5}$ $^{\circ}$K. This was confirmed by combined ground based and ultraviolet observations using the XMM-Newton X-ray telescope. (3) A secondary Outburst of the same nature was expected at 2007 September 13. Within the accuracy of observations (about 6 hours), it started at the correct time. Thus the prediction was accurate at the same level as the prediction of the return of Halley's comet in 1986. (4) Further synchrotron Outbursts were expected following the two bremsstrahlung Outbursts. They came as scheduled between 2007 October and 2009 December. (5) Due to the effect of the secondary on the overall direction of the jet, the parsec scale jet was expected to rotate in the sky by a large angle around and after 2009. This rotation may have been seen at high frequency radio observations. OJ 287 binary black hole system is currently our best laboratory for testing theories of gravitation. Using OJ 287, the correctness of General Relativity has now been demonstrated at higher order than has been possible using the binary pulsars.
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a massive binary black hole system in oj 287 and a test of general relativity
Nature, 2008Co-Authors: Mauri Valtonen, Mark R. Kidger, L. O. Takalo, A. Sillanpää, K Nilsson, H J Lehto, J Heidt, C Villforth, G Poyner, Tapio PursimoAbstract:Black holes are firmly established in astronomy and in the public imagination. Yet the concept still depends on the assumption that Einstein's general theory of relativity is the correct theory of gravitation. Tests of general relativity in a strong gravitational field are best conducted in systems containing black holes. Valtonen et al. report such a test in a close binary system of two proposed black holes in the quasar OJ 287. This quasar shows quasiperiodic optical Outbursts at 12-year intervals, with two Outburst peaks per interval. The latest Outburst in September 2007 was within a day of the time predicted by the binary black hole model and general relativity. Tests of Einstein's general theory of relativity in a strong gravitational field may be best conducted in systems containing black holes. Such a test in a close binary system of two proposed black holes in the quasar OJ287 is reported. 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 the general relativity. 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 theory1,2,3,4,5,6. Binary pulsars4 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 holes7,8. 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 interval9,10. The latest Outburst occurred in September 2007, within a day of the time predicted by the binary black-hole model and general relativity11. 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 system12. In the absence of gravitational wave emission the Outburst would have happened 20 days later13.
