Abstract Details
| Name: Lankeswar Dey Affiliation: Tata Institute of Fundamental Research Conference ID: ASI2018_1617 Title : Constraining higher order gravitational wave back-reaction in blazar OJ287 black hole binary Authors and Co-Authors : Mauri Valtonen, University of Turku. A. Gopakumar, Tata Institute of Fundamental Research. Abstract Type : Contributed Talk Abstract Category : General Relativity and Cosmology Abstract : The binary black hole (BBH) central engine of OJ287 exhibits large thermal flares at least twice in every 12 years. The times of these flares have been predicted successfully using the simple rule that they are generated at a constant phase angle of a quasi-Keplerian eccentric orbit. In this model a secondary black hole goes around a primary black hole, impacting the accretion disk of the latter twice per orbital period, creating above thermal flares. New measurements of the historical light curve have been combined with the observations of the 2015/2017 season. The 2015 November/December flare went into the phase of rapid flux rise on the centenary of Einstein's General Relativity, namely on November 25, and peaked on December 5. At that time OJ287 was the brightest in over 30 years in optical wavelengths. Using the light curve of this flare and subsequent synchrotron flares, and comparing it with the points in the historical light curve, we are able to identify the impact record since the year 1886, altogether 25 impacts. Out of these, 10 are timed accurately enough to constrain the orbit of the black hole binary. The set of flare timings determines uniquely the 8 parameters of our BBH central engine model: the two masses, the primary spin, the major axis, eccentricity and the phase of the orbit, plus the two parameters of the standard accretion disk. Since the orbit solution is strongly over-determined, its parameters are known very accurately, at better than one percent level for the BH masses and primary BH spin. The orbit solution shows that the period of the orbit, now 12.055 yr, has decreased at the rate of 38 days per century. This corresponds an energy loss to gravitational waves that is 4.4 +/- 1 % greater than the rate predicted by the standard quadrupolar GW emission. We show that the difference is due to the influence of higher order gravitational radiation reaction contributions to the BBH dynamics that includes the dominant order tail contributions and the orbital shrinkage rate agrees within error limits with the rate calculated by Damour, Gopakumar and Iyer (2004). At present, we are using the system to test General Relativity in certain yet to be explored strong field regime. This involves constraining a hypothetical fifth force that arises as a modification of General Relativity in some models of dark matter, dark energy and unification theory. |