1,228 research outputs found
Testing black hole no-hair theorem with OJ287
We examine the ability to test the black hole no-hair theorem at the 10%
level in this decade using the binary black hole in OJ287. In the test we
constrain the value of the dimensionless parameter q that relates the scaled
quadrupole moment and spin of the primary black hole: q2 = -q 2 . At the
present we can say that q = 1 \pm 0.3 (one), in agreement with General
Relativity and the no-hair theorems. We demonstrate that this result can be
improved if more observational data is found in historical plate archives for
the 1959 and 1971 outbursts. We also show that the predicted 2015 and 2019
outbursts will be crucial in improving the accuracy of the test. Space-based
photometry is required in 2019 July due the proximity of OJ287 to the Sun at
the time of the outburst. The best situation would be to carry out the
photometry far from the Earth, from quite a different vantage point, in order
to avoid the influence of the nearby Sun. We have considered in particular the
STEREO space mission which would be ideal if it has a continuation in 2019 or
LORRI on board the New Horizons mission to Pluto.Comment: 14 pages, 14 figure
Measuring the spin of the primary black hole in OJ287
The compact binary system in OJ287 is modelled to contain a spinning primary
black hole with an accretion disk and a non-spinning secondary black hole.
Using Post Newtonian (PN) accurate equations that include 2.5PN accurate
non-spinning contributions, the leading order general relativistic and
classical spin-orbit terms, the orbit of the binary black hole in OJ287 is
calculated and as expected it depends on the spin of the primary black hole.
Using the orbital solution, the specific times when the orbit of the secondary
crosses the accretion disk of the primary are evaluated such that the record of
observed outbursts from 1913 up to 2007 is reproduced. The timings of the
outbursts are quite sensitive to the spin value. In order to reproduce all the
known outbursts, including a newly discovered one in 1957, the Kerr parameter
of the primary has to be . The quadrupole-moment contributions
to the equations of motion allow us to constrain the `no-hair' parameter to be
where 0.3 is the one sigma error. This supports the `black hole
no-hair theorem' within the achievable precision.
It should be possible to test the present estimate in 2015 when the next
outburst is due. The timing of the 2015 outburst is a strong function of the
spin: if the spin is 0.36 of the maximal value allowed in general relativity,
the outburst begins in early November 2015, while the same event starts in the
end of January 2016 if the spin is 0.2Comment: 12 pages, 6 figure
Long Term Evolution of Massive Black Hole Binaries
The long-term evolution of massive black hole binaries at the centers of
galaxies is studied in a variety of physical regimes, with the aim of resolving
the ``final parsec problem,'' i.e., how black hole binaries manage to shrink to
separations at which emission of gravity waves becomes efficient. A binary
ejects stars by the gravitational slingshot and carves out a loss cone in the
host galaxy. Continued decay of the binary requires a refilling of the loss
cone. We show that the standard treatment of loss cone refilling, derived for
collisionally relaxed systems like globular clusters, can substantially
underestimate the refilling rates in galactic nuclei. We derive expressions for
non-equilibrium loss-cone dynamics and calculate time scales for the decay of
massive black hole binaries following galaxy mergers, obtaining significantly
higher decay rates than heretofore. Even in the absence of two-body relaxation,
decay of binaries can persist due to repeated ejection of stars returning to
the nucleus on eccentric orbits. We show that this recycling of stars leads to
a gradual, approximately logarithmic dependence of the binary binding energy on
time. We derive an expression for the loss cone refilling induced by the
Brownian motion of a black hole binary. We also show that numerical N-body
experiments are not well suited to probe these mechanisms over long times due
to spurious relaxation.Comment: Replaced to match the accepted version, ApJ, 596 (2003
GRB011211: An alternative interpretation of the optical and X-ray spectra in terms of blueshifts
The redshifts of the gamma ray burst (GRB) GRB 011211 has been determined as
2.14 from several absorption lines seen in the spectrum of its optical
afterglow. The spectrum of its X-ray afterglow exhibited several emission
lines,and their identification led to a mean redshift 1.862. A supernova model
has been proposed based on the redshift of the GRB as 2.141. It is shown here
that the redshift interpretation cannot explain the observed spectra, as some
serious inconsistencies exist in the process of redshift determinations in
spectra of both optical and X-ray afterglows. In view of that, an alternative
interpretation of the spectra is presented in terms of blueshifts. Ejection
mechanism is proposed as a possible scenario to explain the blueshifted
spectrum.Comment: 26 pages, one table; in Canadian Journal of Physics, June 200
Measuring Black Hole Spin in OJ287
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 per period, and the
eccentricity of the orbit 0.70. The dimensionless spin parameter is
(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 . 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).Comment: 12 pages, 4 figures, IAU26
Mapping the three-body system - decay time and reversibility
In this paper we carry out a quantitative analysis of the three-body systems
and map them as a function of decaying time and intial conguration, look at
this problem as an example of a simple deterministic system, and ask to what
extent the orbits are really predictable. We have investigated the behavior of
about 200 000 general Newtonian three body systems using the simplest initial
conditions. Within our resolution these cover all the possible states where the
objects are initially at rest and have no angular momentum. We have determined
the decay time-scales of the triple systems and show that the distribution of
this parameter is fractal in appearance. Some areas that appear stable on large
scales exhibit very narrow strips of instability and the overall pattern,
dominated by resonances, reminds us of a traditional Maasai warrior shield.
Also an attempt is made to recover the original starting conguration of the
three bodies by backward integration. We find there are instances where the
evolution to the future and to the past lead to different orbits, in spite of
time symmetric initial conditions. This implies that even in simple
deterministic systems there exists an Arrow of Time.Comment: 8 pages, 9 figures. Accepted for publication in MNRAS. Includes
low-resolution figures. High-resolution figures are available as PNG
Time-domain behavior of blazar OJ 287 and the binary supermassive black hole conjecture
The proper understanding of blazar variability at the various electromagnetic spectral bands is one goal of multifrequency astrophysics. In this frame a peculiar and controversial phenomenology is the periodicity, postulated for long-term radio or optical flux light curves of about a dozen of blazars. The well-known BL Lac object OJ 287 (PKS 0851+202, S3 0851+20, PG 0851+202, z = 0.306) is not only a high-variable, peculiar, extragalactic source with hints for approximatively cyclical optical outbursts, but it also represents a case of substantial intensive and extensive (long-term) multifrequency observations. This rich database allow us a deeper analysis based on a wide range of variability timescales with some recent results that are highlighted here. © Copyright owned by the author(s).Peer reviewe
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