Yazar "Valtonen, M. J." seçeneğine göre listele

Listeleniyor 1 - 4 / 4
  • [ X ]
    Öğe
    A massive binary black-hole system in OJ 287 and a test of general relativity
    (Nature Publishing Group, 2008) Valtonen, M. J.; Lehto, H. J.; Nilsson, K.; Heidt, J.; Takalo, L. O.; Sillanpaa, A.; Villforth, C.
    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(1-6). Binary pulsars(4) 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(7,8). 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 interval(9,10). The latest outburst occurred in September 2007, within a day of the time predicted by the binary black- hole model and general relativity(11). 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(12). In the absence of gravitational wave emission the outburst would have happened 20 days later(13).
  • [ X ]
    Öğe
    Authenticating the Presence of a Relativistic Massive Black Hole Binary in OJ 287 Using Its General Relativity Centenary Flare: Improved Orbital Parameters
    (Iop Publishing Ltd, 2018) Dey, Lankeswar; Valtonen, M. J.; Gopakumar, A.; Zola, S.; Hudec, R.; Pihajoki, P.; Ciprini, S.
    Results from regular monitoring of relativistic compact binaries like PSR 1913+16 are consistent with the dominant (quadrupole) order emission of gravitational waves (GWs). We show that observations associated with the binary black hole (BBH) central engine of blazar OJ 287 demand the inclusion of gravitational radiation reaction effects beyond the quadrupolar order. It turns out that even the effects of certain hereditary contributions to GW emission are required to predict impact flare timings of OJ 287. We develop an approach that incorporates this effect into the BBH model for OJ 287. This allows us to demonstrate an excellent agreement between the observed impact flare timings and those predicted from ten orbital cycles of the BBH central engine model. The deduced rate of orbital period decay is nine orders of magnitude higher than the observed rate in PSR 1913+16, demonstrating again the relativistic nature of OJ 287's central engine. Finally, we argue that precise timing of the predicted 2019 impact flare should allow a test of the celebrated black hole no-hair theorem at the 10% level.
  • [ X ]
    Öğe
    PRIMARY BLACK HOLE SPIN IN OJ 287 AS DETERMINED BY THE GENERAL RELATIVITY CENTENARY FLARE
    (Iop Publishing Ltd, 2016) Valtonen, M. J.; Zola, S.; Ciprini, S.; Gopakumar, A.; Matsumoto, K.; Sadakane, K.; Kidger, M.
    OJ 287 is a quasi-periodic quasar with roughly 12 year optical cycles. It displays prominent outbursts that are predictable in a binary black hole model. The model predicted a major optical outburst in 2015 December. We found that the outburst did occur within the expected time range, peaking on 2015 December 5 at magnitude 12.9 in the optical R-band. Based on Swift/XRT satellite measurements and optical polarization data, we find that it included a major thermal component. Its timing provides an accurate estimate for the spin of the primary black hole, chi = 0.313 +/- 0.01. The present outburst also confirms the established general relativistic properties of the system such as the loss of orbital energy to gravitational radiation at the 2% accuracy level, and it opens up the possibility of testing the black hole no-hair theorem with 10% accuracy during the present decade.
  • [ X ]
    Öğe
    TIDALLY INDUCED OUTBURSTS IN OJ 287 DURING 2005-2008
    (Iop Publishing Ltd, 2009) Valtonen, M. J.; Nilsson, K.; Villforth, C.; Lehto, H. J.; Takalo, L. O.; Lindfors, E.; Sillanpaa, A.
    The blazar OJ 287 has produced two major optical outburst events during the years 2005-2008. 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.