Spin-dominated waveforms for unequal mass compact binaries

We derive spin-dominated waveforms (SDW) for binary systems composed of spinning black holes with unequal masses (less than 1:30). Such systems could be formed by an astrophysical black hole with a smaller black hole or a neutron star companion; and typically arise for supermassive black hole encounters. SDW characterize the last stages of the inspiral, when the larger spin dominates over the orbital angular momentum (while the spin of the smaller companion can be neglected). They emerge as a double expansion in the post-Newtonian parameter $\varepsilon$ and the ratio $\xi$ of the orbital angular momentum and dominant spin. The SDW amplitudes are presented to ($\varepsilon^{3/2},\xi$) orders, while the phase of the gravitational waves to ($\varepsilon^{2},\xi$) orders (omitting the highest order mixed terms). To this accuracy the amplitude includes the (leading order) spin-orbit contributions, while the phase the (leading order) spin-orbit, self-spin and mass quadrupole-monopole contributions. While the SDW hold for any mass ratio smaller than 1:30, lower bounds for the mass ratios are derived from the best sensitivity frequency range expected for Advanced LIGO (giving 1:140), the Einstein Telescope ($7\times 10^{-4}$), the LAGRANGE ($7\times 10^{-7}$) and LISA missions ($7\times 10^{-9}$), respectively.Comment: 14 pages, 2 figures, 5 tables, published versio

Investigating the Poor Match among Different Precessing Gravitational Waveforms

The sixfold direct detection of gravitational waves opened the era of gravitational wave astronomy. All of these gravitational waves were emitted by black hole or neutron star binaries. The determination of the parameters characterizing compact binaries requires the accurate knowledge of waveforms. Three different waveforms (Spin Dominated, SpinTaylorT4 and Spinning Effective One Body fitted to Numerical Relativity, SEOBNR) are considered in the spin-aligned and precessing cases, in the parameter ranges where the larger spin dominates over the orbital angular momentum. The degeneracy in the parameter space of each waveform is analyzed, then the matches among the waveforms are investigated. Our results show that in the spin-aligned case only the inspiral Spin-dominated and SpinTaylorT4 waveforms agree well with each other. The highest matches of these with SEOBNR are at different parameters as compared to where SEOBNR shows the best match with itself, reflecting SEOBNR being full inspiral-merger-ringdown waveform, with coefficients fitted to numerical relativity, rather than arising from post-Newtonian (PN) calculations. In the precessing case, the matches between the pairs of all waveforms are significantly lower. We identify possible causes of this in (1) the implementation of the angular dynamics carried out at different levels of accuracy for different waveforms; (2) differences in the inclusiveness of the merger process and in the PN coefficients of the inspiral waveforms (Spin-Dominated, SpinTaylorT4) and the full SEOBNR waveform

Gravitáció és asztro-részecske fizika = Gravitation and astro-particle physics

Kutatási pályázatunk 3,5 éves futamideje alatt gravitációelméleti kutatásokat végeztünk. Eredményeinket a következő főbb területeken értük el: • gravitációs sugárzás és pályamozgás vizsgálata kompakt kettősöknél • akkréciós folyamatok, mágneses terek és részecskenyalábok fekete lyukak környezetében • brán-világok kovariáns analízise (alkalmazásokkal), változó brán-feszültség, brán-kozmológia • árapály-töltésű fekete lyukak fényelhajlása, gravitációs lencsézése, termodinamikai elemzése • hamiltoni dinamika brán-elméletben • sötét energia modellek A pályázat 3,5 éve alatt összesen 42 publikáció született. Ebből 26 SCI folyóiratcikk (össz-impakt faktoruk 108,06), 2 beküldött cikk, 2 disszertáció, 9 egyéb folyóiratcikk, 2 könyvben publikálandó konferenciacikk és 1 konferenciakiadvány. A pályázat résztvevői összesen 38 (plenáris / meghívott / konferencia / szemináriumi) előadást és posztert mutattak be. Eredményeink közül kiemelnénk a következőket: (i) az X-alakú rádiógalaxisok kialakulásának magyarázata spin-pálya precesszió és gravitációs sugárzás hatására (ii) változó brán feszültségű modellek kidolgozása, az Eötvös-brán bevezetése (iii) gyorsuló kozmológiai tágulással kompatibilis, de exponenciális tágulás helyett Big Brake gyenge szingularitáson át Big Crunch-hoz vezető kozmológiai modell kidolgozása. | During the 3.5 year span of the proposal we carried on research related to gravitation. We achieved results in the following fields • gravitational radiation and compact binary orbital dynamics • accretion processes, magnetic fields, particle jets in the neighbourhood of black holes • covariant brane-world dynamics (with applications), variable brane tension models, brane cosmology • light deflection and gravitational lensing by tidal charged black holes; thermodynamic analysis • Hamiltonian dynamics in brane-worlds • dark energy models During the 3.5 years of the proposal we authored 42 publications. 26 of them are SCI journal papers (total impact factor of 108.06), 2 submitted papers, 2 PhD theses, 9 other journal papers, 2 conference papers to be published in books and one other conference material. The participants of the proposal have delivered a total of 38 lectures (plenary / invited / conference / seminar) and posters. From among our results we highlight the following: (i) the explanation of formation of X-shaped radio galaxies by spin-orbit precession and gravitational radiation (ii) developing variable tension brane-world models, introducing the Eötvös-brane (iii) the introduction of a cosmological model compatible with the late-time acceleration, evolving instead of an exponential expansion into a Big Brake soft singularity followed by a Big Crunch

Upper Limits on the Rates of Binary Neutron Star and Neutron Star-Black Hole Mergers from Advanced Ligo's First Observing Run

We report here the non-detection of gravitational waves from the merger of binary neutron star systems and neutron-star–black-hole systems during the first observing run of Advanced LIGO. In particular we searched for gravitational wave signals from binary neutron star systems with component masses ∈ [1, 3]M and component dimensionless spins < 0.05. We also searched for neutron-star–black-hole systems with the same neutron star parameters, black hole mass ∈ [2, 99]M and no restriction on the black hole spin magnitude. We assess the sensitivity of the two LIGO detectors to these systems, and find that they could have detected the merger of binary neutron star systems with component mass distributions of 1.35±0.13M at a volume-weighted average distance of ∼ 70 Mpc, and for neutron-star–black-hole systems with neutron star masses of 1.4M and black hole masses of at least 5M , a volume-weighted average distance of at least ∼ 110 Mpc. From this we constrain with 90% confidence the merger rate to be less than 12,600 Gpc−3 yr−1 for binary-neutron star systems and less than 3,600 Gpc−3 yr−1 for neutron-star–black-hole systems. We discuss the astrophysical implications of these results, which we find to be in tension with only the most optimistic predictions. However, we find that if no detection of neutron-star binary mergers is made in the next two Advanced LIGO and Advanced Virgo observing runs we would place significant constraints on the merger rates

Search for gravitational waves from Scorpius X-1 in the first Advanced LIGO observing run with a hidden Markov model

Results are presented from a semicoherent search for continuous gravitational waves from the brightest low-mass X-ray binary, Scorpius X-1, using data collected during the first Advanced LIGO observing run. The search combines a frequency domain matched filter (Bessel-weighted F-statistic) with a hidden Markov model to track wandering of the neutron star spin frequency. No evidence of gravitational waves is found in the frequency range 60-650 Hz. Frequentist 95% confidence strain upper limits, h(0)(95%) = 4.0 x 10(-25), 8.3 x 10(-25), and 3.0 x 10(-25) for electromagnetically restricted source orientation, unknown polarization, and circular polarization, respectively, are reported at 106 Hz. They are <= 10 times higher than the theoretical torque-balance limit at 106 Hz