The spin of the near-extreme Kerr black hole GRS 1915+105

The Astrophysical Journal (Impact Factor: 6.28). 06/2006; 652(1). DOI: 10.1086/508457
Source: arXiv

ABSTRACT Based on a spectral analysis of the X-ray continuum that employs a fully
relativistic accretion-disk model, we conclude that the compact primary of the
binary X-ray source GRS 1915+105 is a rapidly-rotating Kerr black hole. We find
a lower limit on the dimensionless spin parameter of a* greater than 0.98. Our
result is robust in the sense that it is independent of the details of the data
analysis and insensitive to the uncertainties in the mass and distance of the
black hole. Furthermore, our accretion-disk model includes an advanced
treatment of spectral hardening. Our data selection relies on a rigorous and
quantitative definition of the thermal state of black hole binaries, which we
used to screen all of the available RXTE and ASCA data for the thermal state of
GRS 1915+105. In addition, we focus on those data for which the accretion disk
luminosity is less than 30% of the Eddington luminosity. We argue that these
low-luminosity data are most appropriate for the thin alpha-disk model that we
employ. We assume that there is zero torque at the inner edge of the disk, as
is likely when the disk is thin, although we show that the presence of a
significant torque does not affect our results. Our model and the model of the
relativistic jets observed for this source constrain the distance and black
hole mass and could thus be tested by determining a VLBA parallax distance and
improving the measurement of the mass function. Finally, we comment on the
significance of our results for relativistic-jet and core-collapse models, and
for the detection of gravitational waves.

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    • "In considering non-BPS configurations, it is natural to seek a construction of gravitational solutions describing microstates of extremal, non-BPS black holes such as the extremal Kerr [9] and Myers-Perry [10] solutions. There is strong observational evidence of the existence of near-extremal black holes in our galaxy [11]. There has also been much interest in a recent conjecture that quantum gravity in the near-horizon region of an extremal Kerr black hole may be described by a chiral 2D CFT [12]. "
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    Journal of High Energy Physics 10/2013; 2014(4). DOI:10.1007/JHEP04(2014)072 · 6.22 Impact Factor
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    • "For completeness, the velocity profile is given also for extreme black hole, demonstrating velocity jump at r = 1. by the humpy frequency, the radial (and vertical) epicyclic frequencies and their simple combinations taken at the common " humpy " radius, implying the black hole parameters of the source M = 14.8 M ⊙ , a=0.9998 [22], in good agreement with estimates given by different methods [6] [20]. This model can give interesting results also in the case of the X-ray binary system XTE J1650-500 [24], and an ULX candidate system NGC 5408 X-1. "
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    Classical and Quantum Gravity 07/2011; 28(17). DOI:10.1088/0264-9381/28/17/175002 · 3.10 Impact Factor
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    • "This correspondence has been extended to various exotic black holes in string theory, higher dimensional theories and gauged supergravities to name a few [48] [47] [49]. One of the main arguments of the Kerr/CFT correspondence is to apply the rich ideas of holographic duality to more astrophysical objects/black-holes, such as the nearly extremal GRS 1915+105, a binary black hole system 11000pc away in Aquila [50]. In [44] the authors show that GRS 1915+105 is holographically dual to a 2-dimensional chiral CFT with c L = (2±1)×10 79 and in the extremal limit the inner most stable circular orbit corresponds to the horizon. "
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