1,980 research outputs found
Final spin of a coalescing black-hole binary: an Effective-One-Body approach
We update the analytical estimate of the final spin of a coalescing
black-hole binary derived within the Effective-One-Body (EOB) approach. We
consider unequal-mass non-spinning black-hole binaries. It is found that a more
complete account of relevant physical effects (higher post-Newtonian accuracy,
ringdown losses) allows the {\it analytical} EOB estimate to `converge towards'
the recently obtained {\it numerical} results within 2%. This agreement
illustrates the ability of the EOB approach to capture the essential physics of
coalescing black-hole binaries. Our analytical approach allows one to estimate
the final spin of the black hole formed by coalescing binaries in a mass range
() which is not presently covered by numerical
simulations.Comment: 8 pages, two figures. To appear in Phys. Rev.
Gravitational waves from inspiraling binary black holes
Binary black holes are the most promising candidate sources for the first
generation of earth-based interferometric gravitational-wave detectors. We
summarize and discuss the state-of-the-art analytic techniques developed during
the last years to better describe the late dynamical evolution of binary black
holes of comparable masses.Comment: References added and updated; few typos correcte
Higher-order spin effects in the dynamics of compact binaries II. Radiation field
Motivated by the search for gravitational waves emitted by binary black
holes, we investigate the gravitational radiation field of point particles with
spins within the framework of the multipolar-post-Newtonian wave generation
formalism. We compute: (i) the spin-orbit (SO) coupling effects in the binary's
mass and current quadrupole moments one post-Newtonian (1PN) order beyond the
dominant effect, (ii) the SO contributions in the gravitational-wave energy
flux and (iii) the secular evolution of the binary's orbital phase up to 2.5PN
order. Crucial ingredients for obtaining the 2.5PN contribution in the orbital
phase are the binary's energy and the spin precession equations, derived in
paper I of this series. These results provide more accurate gravitational-wave
templates to be used in the data analysis of rapidly rotating Kerr-type
black-hole binaries with the ground-based detectors LIGO, Virgo, GEO 600 and
TAMA300, and the space-based detector LISA.Comment: includes the correction of an erratum to be published in Phys. Rev.
Post-Newtonian factorized multipolar waveforms for spinning, non-precessing black-hole binaries
We generalize the factorized resummation of multipolar waveforms introduced
by Damour, Iyer and Nagar to spinning black holes. For a nonspinning
test-particle spiraling a Kerr black hole in the equatorial plane, we find that
factorized multipolar amplitudes which replace the residual relativistic
amplitude f_{l m} with its l-th root, \rho_{l m} = f_{l m}^{1/l}, agree quite
well with the numerical amplitudes up to the Kerr-spin value q \leq 0.95 for
orbital velocities v \leq 0.4. The numerical amplitudes are computed solving
the Teukolsky equation with a spectral code. The agreement for prograde orbits
and large spin values of the Kerr black hole can be further improved at high
velocities by properly factoring out the lower-order post-Newtonian
contributions in \rho_{l m}. The resummation procedure results in a better and
systematic agreement between numerical and analytical amplitudes (and energy
fluxes) than standard Taylor-expanded post-Newtonian approximants. This is
particularly true for higher-order modes, such as (2,1), (3,3), (3,2), and
(4,4) for which less spin post-Newtonian terms are known. We also extend the
factorized resummation of multipolar amplitudes to generic mass-ratio,
non-precessing, spinning black holes. Lastly, in our study we employ new,
recently computed, higher-order post-Newtonian terms in several subdominant
modes, and compute explicit expressions for the half and one-and-half
post-Newtonian contributions to the odd-parity (current) and even-parity (odd)
multipoles, respectively. Those results can be used to build more accurate
templates for ground-based and space-based gravitational-wave detectors.Comment: 37 pages, 11 figures; Typos in Sec.IV Eqs.(38-42) fixe
Globular Clusters in the Magellanic Clouds.I:BV CCD-Photometry for 11 Clusters
We present BV CCD-data for 11 intermediate-age LMC clusters; the main
conclusions are: 1. in the (V_to, V_cl,m) and (V-to, (V_to-V_cl,m)) planes the
models yield a good overall description of the data; 2. with the current
sample, it is impossible to firmly choose between "classical" and
"overshooting" models; 3. the separation in colour between the MS band and the
Red He-burning Clump is smaller than predicted by theoretical tracks; 4. the
existence of the so-called "RGB phase-transition (Renzini and Buzzoni 1986)
seems to be confirmed.Comment: 62 pages, 37 figures and tables 6 to 16 available on request,
uuencoded compressed postscript file with tables 1-5 and 17-18 included, BAP
08-1994-020-OA
Higher-order spin effects in the amplitude and phase of gravitational waveforms emitted by inspiraling compact binaries: Ready-to-use gravitational waveforms
We provide ready-to-use time-domain gravitational waveforms for spinning
compact binaries with precession effects through 1.5PN order in amplitude and
compute their mode decomposition using spin-weighted -2 spherical harmonics. In
the presence of precession, the gravitational-wave modes (l,m) contain
harmonics originating from combinations of the orbital frequency and precession
frequencies. We find that the gravitational radiation from binary systems with
large mass asymmetry and large inclination angle can be distributed among
several modes. For example, during the last stages of inspiral, for some
maximally spinning configurations, the amplitude of the (2,0) and (2,1) modes
can be comparable to the amplitude of the (2,2) mode. If the mass ratio is not
too extreme, the l=3 and l=4 modes are generally one or two orders of magnitude
smaller than the l = 2 modes. Restricting ourselves to spinning, non-precessing
compact binaries, we apply the stationary-phase approximation and derive the
frequency-domain gravitational waveforms including spin-orbit and spin(1)-
spin(2) effects through 1.5PN and 2PN order respectively in amplitude, and
2.5PN order in phase. Since spin effects in the amplitude through 2PN order
affect only the first and second harmonics of the orbital phase, they do not
extend the mass reach of gravitational-wave detectors. However, they can
interfere with other harmonics and lower or raise the signal-to-noise ratio
depending on the spin orientation. These ready-to-use waveforms could be
employed in the data-analysis of the spinning, inspiraling binaries as well as
in comparison studies at the interface between analytical and numerical
relativity.Comment: 43 pages, 10 Postscript figures. submitted to Physical Review D.
Includes corrections due to errat
Transition from inspiral to plunge for eccentric equatorial Kerr orbits
Ori and Thorne have discussed the duration and observability (with LISA) of
the transition from circular, equatorial inspiral to plunge for stellar-mass
objects into supermassive () Kerr black holes. We
extend their computation to eccentric Kerr equatorial orbits. Even with orbital
parameters near-exactly determined, we find that there is no universal length
for the transition; rather, the length of the transition depends sensitively --
essentially randomly -- on initial conditions. Still, Ori and Thorne's
zero-eccentricity results are essentially an upper bound on the length of
eccentric transitions involving similar bodies (e.g., fixed). Hence the
implications for observations are no better: if the massive body is
, the captured body has mass , and the process occurs at
distance from LISA, then , with the precise constant depending on
the black hole spin. For low-mass bodies () for which the
event rate is at least vaguely understood, we expect little chance (probably
[much] less than 10%, depending strongly on the astrophysical assumptions) of
LISA detecting a transition event with during its run; however, even a
small infusion of higher-mass bodies or a slight improvement in LISA's noise
curve could potentially produce transition events during LISA's
lifetime.Comment: Submitted to PR
Multiple stellar populations in Magellanic Cloud clusters. II. Evidence also in the young NGC1844?
We use HST observations to study the LMC's young cluster NGC1844. We estimate
the fraction and the mass-ratio distribution of photometric binaries and report
that the main sequence presents an intrinsic breadth which can not be explained
in terms of photometric errors only, and is unlikely due to differential
reddening. We attempt some interpretation of this feature, including stellar
rotation, binary stars, and the presence of multiple stellar populations with
different age, metallicity, helium, or C+N+O abundance. Although we exclude
age, helium, and C+N+O variations to be responsible of the main-sequence spread
none of the other interpretations is conclusive.Comment: 9 Pages, 11 figures, accepted for publication in A&A
- …