416 research outputs found
Three-Body Dynamics with Gravitational Wave Emission
We present numerical three-body experiments that include the effects of
gravitational radiation reaction by using equations of motion that include the
2.5-order post-Newtonian force terms, which are the leading order terms of
energy loss from gravitational waves. We simulate binary-single interactions
and show that close approach cross sections for three 1 solar mass objects are
unchanged from the purely Newtonian dynamics except for close approaches
smaller than 1.0e-5 times the initial semimajor axis of the binary. We also
present cross sections for mergers resulting from gravitational radiation
during three-body encounters for a range of binary semimajor axes and mass
ratios including those of interest for intermediate-mass black holes (IMBHs).
Building on previous work, we simulate sequences of high-mass-ratio three-body
encounters that include the effects of gravitational radiation. The simulations
show that the binaries merge with extremely high eccentricity such that when
the gravitational waves are detectable by LISA, most of the binaries will have
eccentricities e > 0.9 though all will have circularized by the time they are
detectable by LIGO. We also investigate the implications for the formation and
growth of IMBHs and find that the inclusion of gravitational waves during the
encounter results in roughly half as many black holes ejected from the host
cluster for each black hole accreted onto the growing IMBH.Comment: 34 pages, 14 figures, minor corrections to match version accepted by
Ap
Study of multi black hole and ring singularity apparent horizons
We study critical black hole separations for the formation of a common
apparent horizon in systems of - black holes in a time symmetric
configuration. We study in detail the aligned equal mass cases for ,
and relate them to the unequal mass binary black hole case. We then study the
apparent horizon of the time symmetric initial geometry of a ring singularity
of different radii. The apparent horizon is used as indicative of the location
of the event horizon in an effort to predict a critical ring radius that would
generate an event horizon of toroidal topology. We found that a good estimate
for this ring critical radius is . We briefly discuss the
connection of this two cases through a discrete black hole 'necklace'
configuration.Comment: 31 pages, 21 figure
Revisiting the black hole mass of M87* using VLT/MUSE Adaptive Optics Integral Field Unit data I: Ionized gas kinematics
The stellar dynamic-based black hole mass measurements of M87 are twice that
determined via ionized gas kinematics; the former is closer to the estimation
from the diameter of the gravitationally-lensed ring around the black hole.
Using deeper and more comprehensive ionized gas kinematic data, we aim to
better constrain the morphology and kinematics of the nuclear ionized gas, thus
gaining insights into the reasons behind the disagreement of the measurements.
We use both Narrow and Wide Field Mode integral field spectroscopic data from
the Multi Unit Spectroscopic Explorer instrument, to model the morphology and
kinematics of multiple ionized gas emission lines in the nucleus of M87. The
new deep dataset reveals complexities in the nuclear ionized gas kinematics.
Several ionized gas filaments can be traced down into the projected sphere of
influence. We also found evidence of a partially-filled biconical outflow. The
velocity isophotes of the ionized gas disk are twisted and the position angle
of the innermost gas disk tends toward a value perpendicular to the radio jet
axis. The complexity of the nuclear morphology and kinematics precludes the
measurement of an accurate black hole mass. The results support a 6.0 black hole in a 25\deg disk, rather than a 3.5 black hole in a 42\deg disk. The specific RIAF model
earlier proposed to reconcile the mass measurement discrepancy was also tested.
In general, Keplerian disk models perform better than the RIAF model when
fitting the sub-arcsec ionized gas disk. A disk inclination close to 25\deg for
the nuclear gas disk, and the warp in the sub-arcsec ionized gas disk, help to
reconcile the contradictory nature of the mass discrepancy between stellar and
ionized gas black hole masses, and the mis-orientation between the axes of the
ionized gas disk and the jet.Comment: 21 pages, 22 figures (5 of them in the appendix). Accepted in
Astronomy & Astrophysic
A Single Circumbinary Disk in the HD 98800 Quadruple System
We present sub-arcsecond thermal infrared imaging of HD 98800, a young
quadruple system composed of a pair of low-mass spectroscopic binaries
separated by 0.8'' (38 AU), each with a K-dwarf primary. Images at wavelengths
ranging from 5 to 24.5 microns show unequivocally that the optically fainter
binary, HD 98800B, is the sole source of a comparatively large infrared excess
upon which a silicate emission feature is superposed. The excess is detected
only at wavelengths of 7.9 microns and longer, peaks at 25 microns, and has a
best-fit black-body temperature of 150 K, indicating that most of the dust lies
at distances greater than the orbital separation of the spectroscopic binary.
We estimate the radial extent of the dust with a disk model that approximates
radiation from the spectroscopic binary as a single source of equivalent
luminosity. Given the data, the most-likely values of disk properties in the
ranges considered are R_in = 5.0 +/- 2.5 AU, DeltaR = 13+/-8 AU, lambda_0 =
2(+4/-1.5) microns, gamma = 0+/-2.5, and sigma_total = 16+/-3 AU^2, where R_in
is the inner radius, DeltaR is the radial extent of the disk, lambda_0 is the
effective grain size, gamma is the radial power-law exponent of the optical
depth, tau, and sigma_total is the total cross-section of the grains. The range
of implied disk masses is 0.001--0.1 times that of the moon. These results show
that, for a wide range of possible disk properties, a circumbinary disk is far
more likely than a narrow ring.Comment: 11 page Latex manuscript with 3 postscript figures. Accepted for
publication in Astrophysical Journal Letters. Postscript version of complete
paper also available at
http://www.hep.upenn.edu/PORG/web/papers/koerner00a.p
Multi-Wavelength Coverage of State Transitions in the New Black Hole X-Ray Binary Swift J1910.2-0546
Understanding how black holes accrete and supply feedback to their
environment is one of the outstanding challenges of modern astrophysics. Swift
J1910.2-0546 is a candidate black hole low-mass X-ray binary that was
discovered in 2012 when it entered an accretion outburst. To investigate the
binary configuration and the accretion morphology we monitored the evolution of
the outburst for ~3 months at X-ray, UV, optical (B,V,R,I), and near-infrared
(J,H,K) wavelengths using Swift and SMARTS. The source evolved from a hard to a
soft X-ray spectral state with a relatively cold accretion disk that peaked at
~0.5 keV. A Chandra/HETG spectrum obtained during this soft state did not
reveal signatures of an ionized disk wind. Both the low disk temperature and
the absence of a detectable wind could indicate that the system is viewed at
relatively low inclination. The multi-wavelength light curves revealed two
notable features that appear to be related to X-ray state changes. Firstly, a
prominent flux decrease was observed in all wavebands ~1-2 weeks before the
source entered the soft state. This dip occurred in (0.6-10 keV) X-rays ~6 days
later than at longer wavelengths, which could possibly reflect the viscous time
scale of the disk. Secondly, about two weeks after the source transitioned back
into the hard state, the UV emission significantly increased while the X-rays
steadily decayed. We discuss how these observations may reflect changes in the
accretion flow morphology, perhaps related to the quenching/launch of a jet or
the collapse/recovery of a hot flow.Comment: 8 pages, 5 figures, 1 table. To be published in Ap
A Swift survey of accretion onto stellar-mass black holes
We present a systemic analysis of all of the stellar mass black hole binaries
(confirmed & candidate) observed by the Swift observatory up to June 2010. The
broad Swift bandpass enables a trace of disk evolution over an unprecedented
range in flux and temperature. The final data sample consists of 476 X-ray
spectra containing greater than 100 counts, in the 0.6 -- 10 keV band. This is
the largest sample of high quality CCD spectra of accreting black holes
published to date. In addition, strictly simultaneous data at optical/UV
wavelengths are available for 255 (54%) of these observations.
The data are modelled with a combination of an accretion disk and a hard
spectral component. For the hard component we consider both a simple power-law
and a thermal Comptonization model. An accretion disk is detected at greater
than the 5sigma confidence level in 61% of the observations. Lightcurves and
color-color diagrams are constructed for each system. Hardness luminosity and
disk fraction luminosity diagrams are constructed and are observed to be
consistent with those typically observed by RXTE, noting the sensitivity below
2 keV provided by Swift. The observed spectra have an average luminosity of ~
1% Eddington, though we are sensitive to accretion disks down to a luminosity
of 10^{-3} L_Edd. Thus this is also the largest sample of such cool accretion
disks studied to date. (abridged)Comment: 28 pages, 5 tables, 21 figures, Accepted for publication in ApJ. This
is the final revised versio
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