IRIS Università degli Studi di Urbinohttps://ora.uniurb.itIl sistema di repository digitale IRIS acquisisce, archivia, indicizza, conserva e rende accessibili prodotti digitali della ricerca.Sat, 31 Jul 2021 22:07:03 GMT2021-07-31T22:07:03Z103611Open data from the first and second observing runs of Advanced LIGO and Advanced Virgohttp://hdl.handle.net/11576/2689180Titolo: Open data from the first and second observing runs of Advanced LIGO and Advanced Virgo
Abstract: Advanced LIGO and Advanced Virgo are monitoring the sky and collecting gravitational-wave strain data with sufficient sensitivity to detect signals routinely. In this paper we describe the data recorded by these instruments during their first and second observing runs. The main data products are gravitational-wave strain time series sampled at 16384 Hz. The datasets that include this strain measurement can be freely accessed through the Gravitational Wave Open Science Center at http://gw-openscience.org, together with data-quality information essential for the analysis of LIGO and Virgo data, documentation, tutorials, and supporting software.
Fri, 01 Jan 2021 00:00:00 GMThttp://hdl.handle.net/11576/26891802021-01-01T00:00:00ZGWTC-2: Compact Binary Coalescences Observed by LIGO and Virgo during the First Half of the Third Observing Runhttp://hdl.handle.net/11576/2689176Titolo: GWTC-2: Compact Binary Coalescences Observed by LIGO and Virgo during the First Half of the Third Observing Run
Abstract: We report on gravitational-wave discoveries from compact binary coalescences detected by Advanced LIGO and Advanced Virgo in the first half of the third observing run (O3a) between 1 April 2019
15
∶
00
UTC and 1 October 2019
15
∶
00
UTC. By imposing a false-alarm-rate threshold of two per year in each of the four search pipelines that constitute our search, we present 39 candidate gravitational-wave events. At this threshold, we expect a contamination fraction of less than 10%. Of these, 26 candidate events were reported previously in near-real time through gamma-ray coordinates network notices and circulars; 13 are reported here for the first time. The catalog contains events whose sources are black hole binary mergers up to a redshift of approximately 0.8, as well as events whose components cannot be unambiguously identified as black holes or neutron stars. For the latter group, we are unable to determine the nature based on estimates of the component masses and spins from gravitational-wave data alone. The range of candidate event masses which are unambiguously identified as binary black holes (both objects
≥
3
M
⊙
) is increased compared to GWTC-1, with total masses from approximately
14
M
⊙
for GW190924_021846 to approximately
150
M
⊙
for GW190521. For the first time, this catalog includes binary systems with significantly asymmetric mass ratios, which had not been observed in data taken before April 2019. We also find that 11 of the 39 events detected since April 2019 have positive effective inspiral spins under our default prior (at 90% credibility), while none exhibit negative effective inspiral spin. Given the increased sensitivity of Advanced LIGO and Advanced Virgo, the detection of 39 candidate events in approximately 26 weeks of data (approximately 1.5 per week) is consistent with GWTC-1.
Fri, 01 Jan 2021 00:00:00 GMThttp://hdl.handle.net/11576/26891762021-01-01T00:00:00ZTests of general relativity with binary black holes from the second LIGO-Virgo gravitational-wave transient cataloghttp://hdl.handle.net/11576/2689241Titolo: Tests of general relativity with binary black holes from the second LIGO-Virgo gravitational-wave transient catalog
Abstract: Gravitational waves enable tests of general relativity in the highly dynamical and strong-field regime. Using events detected by LIGO-Virgo up to 1 October 2019, we evaluate the consistency of the data with predictions from the theory. We first establish that residuals from the best-fit waveform are consistent with detector noise, and that the low- and high-frequency parts of the signals are in agreement. We then consider parametrized modifications to the waveform by varying post-Newtonian and phenomenological coefficients, improving past constraints by factors of ∼2; we also find consistency with Kerr black holes when we specifically target signatures of the spin-induced quadrupole moment. Looking for gravitational-wave dispersion, we tighten constraints on Lorentz-violating coefficients by a factor of ∼2.6 and bound the mass of the graviton to mg ≤ 1.76×10−23 eV/c2 with 90% credibility. We also analyze the properties of the merger remnants by measuring ringdown frequencies and damping times, constraining fractional deviations away from the Kerr frequency to δ^f 220 = 0.03 +0.38 −0.35 for the fundamental quadrupolar mode, and δ^f221 = 0.04 +0.27 −0.32 for the first overtone; additionally, we find no evidence for postmerger echoes. Finally, we determine that our data are consistent with tensorial polarizations through a template-independent method. When possible, we assess the validity of general relativity based on collections of events analyzed jointly. We find no evidence for new physics beyond general relativity, for black hole mimickers, or for any unaccounted systematics.
Fri, 01 Jan 2021 00:00:00 GMThttp://hdl.handle.net/11576/26892412021-01-01T00:00:00ZSearch for anisotropic gravitational-wave backgrounds using data from Advanced LIGO and Advanced Virgo’s first three observing runshttp://hdl.handle.net/11576/2689884Titolo: Search for anisotropic gravitational-wave backgrounds using data from Advanced LIGO and Advanced Virgo’s first three observing runs
Abstract: We report results from searches for anisotropic stochastic gravitational-wave backgrounds using data from the first three observing runs of the Advanced LIGO and Advanced Virgo detectors. For the first time, we include Virgo data in our analysis and run our search with a new efficient pipeline called pystoch on data folded over one sidereal day. We use gravitational-wave radiometry (broadband and narrow band) to produce sky maps of stochastic gravitational-wave backgrounds and to search for gravitational waves from point sources. A spherical harmonic decomposition method is employed to look for gravitational-wave emission from spatially-extended sources. Neither technique found evidence of gravitational-wave signals. Hence we derive 95% confidence-level upper limit sky maps on the gravitational-wave energy flux from broadband point sources, ranging from
F_α,Θ < (0.013–7.6)×10−8 erg cm−2 s−1 Hz−1, and on the (normalized) gravitational-wave energy density spectrum from extended sources, ranging from Ω_α,Θ < (0.57–9.3)×10−9 sr−1, depending on direction (Θ) and spectral index (α). These limits improve upon previous limits by factors of 2.9–3.5. We also set 95% confidence level upper limits on the frequency-dependent strain amplitudes of quasimonochromatic gravitational waves coming from three interesting targets, Scorpius X-1, SN 1987A and the Galactic Center, with best upper limits range from h0 < (1.7–2.1)×10−25, a factor of ≥ 2.0 improvement compared to previous stochastic radiometer searches.
Fri, 01 Jan 2021 00:00:00 GMThttp://hdl.handle.net/11576/26898842021-01-01T00:00:00ZA Gravitational-wave Measurement of the Hubble Constant Following the Second Observing Run of Advanced LIGO and Virgohttp://hdl.handle.net/11576/2689186Titolo: A Gravitational-wave Measurement of the Hubble Constant Following the Second Observing Run of Advanced LIGO and Virgo
Abstract: This paper presents the gravitational-wave measurement of the Hubble constant (H0) using the detections from the first and second observing runs of the Advanced LIGO and Virgo detector network. The presence of the transient electromagnetic counterpart of the binary neutron star GW170817 led to the first standard-siren measurement of H0. Here we additionally use binary black hole detections in conjunction with galaxy catalogs and report a joint measurement. Our updated measurement is H0 = ${69}_{-8}^{+16}$ km s−1 Mpc−1 (68.3% of the highest density posterior interval with a flat-in-log prior) which is an improvement by a factor of 1.04 (about 4%) over the GW170817-only value of ${69}_{-8}^{+17}$ km s−1 Mpc−1. A significant additional contribution currently comes from GW170814, a loud and well-localized detection from a part of the sky thoroughly covered by the Dark Energy Survey. With numerous detections anticipated over the upcoming years, an exhaustive understanding of other systematic effects are also going to become increasingly important. These results establish the path to cosmology using gravitational-wave observations with and without transient electromagnetic counterparts.
Fri, 01 Jan 2021 00:00:00 GMThttp://hdl.handle.net/11576/26891862021-01-01T00:00:00ZSearch for Gravitational Waves Associated with Gamma-Ray Bursts Detected by Fermi and Swift during the LIGO–Virgo Run O3ahttp://hdl.handle.net/11576/2689690Titolo: Search for Gravitational Waves Associated with Gamma-Ray Bursts Detected by Fermi and Swift during the LIGO–Virgo Run O3a
Abstract: We search for gravitational-wave transients associated with gamma-ray bursts (GRBs) detected by the Fermi and Swift satellites during the first part of the third observing run of Advanced LIGO and Advanced Virgo (2019 April 1 15:00 UTC–2019 October 1 15:00 UTC). A total of 105 GRBs were analyzed using a search for generic gravitational-wave transients; 32 GRBs were analyzed with a search that specifically targets neutron star binary mergers as short GRB progenitors. We find no significant evidence for gravitational-wave signals associated with the GRBs that we followed up, nor for a population of unidentified subthreshold signals. We consider several source types and signal morphologies, and report for these lower bounds on the distance to each GRB.
Fri, 01 Jan 2021 00:00:00 GMThttp://hdl.handle.net/11576/26896902021-01-01T00:00:00ZObservation of Gravitational Waves from Two Neutron Star–Black Hole Coalescenceshttp://hdl.handle.net/11576/2689481Titolo: Observation of Gravitational Waves from Two Neutron Star–Black Hole Coalescences
Abstract: We report the observation of gravitational waves from two compact binary coalescences in LIGO's and Virgo's third observing run with properties consistent with neutron star–black hole (NSBH) binaries. The two events are named GW200105_162426 and GW200115_042309, abbreviated as GW200105 and GW200115; the first was observed by LIGO Livingston and Virgo and the second by all three LIGO–Virgo detectors. The source of GW200105 has component masses $8.{9}_{-1.5}^{+1.2}$ and $1.{9}_{-0.2}^{+0.3},{M}_{odot }$, whereas the source of GW200115 has component masses $5.{7}_{-2.1}^{+1.8}$ and $1.{5}_{-0.3}^{+0.7},{M}_{odot }$ (all measurements quoted at the 90% credible level). The probability that the secondary's mass is below the maximal mass of a neutron star is 89%–96% and 87%–98%, respectively, for GW200105 and GW200115, with the ranges arising from different astrophysical assumptions. The source luminosity distances are ${280}_{-110}^{+110}$ and ${300}_{-100}^{+150},mathrm{Mpc}$, respectively. The magnitude of the primary spin of GW200105 is less than 0.23 at the 90% credible level, and its orientation is unconstrained. For GW200115, the primary spin has a negative spin projection onto the orbital angular momentum at 88% probability. We are unable to constrain the spin or tidal deformation of the secondary component for either event. We infer an NSBH merger rate density of ${45}_{-33}^{+75},{mathrm{Gpc}}^{-3},{mathrm{yr}}^{-1}$ when assuming that GW200105 and GW200115 are representative of the NSBH population or ${130}_{-69}^{+112},{mathrm{Gpc}}^{-3},{mathrm{yr}}^{-1}$ under the assumption of a broader distribution of component masses.
Fri, 01 Jan 2021 00:00:00 GMThttp://hdl.handle.net/11576/26894812021-01-01T00:00:00ZPopulation Properties of Compact Objects from the Second LIGO–Virgo Gravitational-Wave Transient Cataloghttp://hdl.handle.net/11576/2688781Titolo: Population Properties of Compact Objects from the Second LIGO–Virgo Gravitational-Wave Transient Catalog
Abstract: We report on the population of 47 compact binary mergers detected with a false-alarm rate of <$1,{mathrm{yr}}^{-1}$ in the second LIGO–Virgo Gravitational-Wave Transient Catalog. We observe several characteristics of the merging binary black hole (BBH) population not discernible until now. First, the primary mass spectrum contains structure beyond a power law with a sharp high-mass cutoff; it is more consistent with a broken power law with a break at ${39.7}_{-9.1}^{+20.3},,{M}_{odot }$ or a power law with a Gaussian feature peaking at ${33.1}_{-5.6}^{+4.0},,{M}_{odot }$ (90% credible interval). While the primary mass distribution must extend to $sim 65,{M}_{odot }$ or beyond, only ${2.9}_{-1.7}^{+3.5} % $ of systems have primary masses greater than $45,{M}_{odot }$. Second, we find that a fraction of BBH systems have component spins misaligned with the orbital angular momentum, giving rise to precession of the orbital plane. Moreover, $12$%–$44$% of BBH systems have spins tilted by more than 90°, giving rise to a negative effective inspiral spin parameter, ${chi }_{mathrm{eff}}$. Under the assumption that such systems can only be formed by dynamical interactions, we infer that between 25% and 93% of BBHs with nonvanishing $| {chi }_{mathrm{eff}}| gt 0.01$ are dynamically assembled. Third, we estimate merger rates, finding ${{ mathcal R }}_{mathrm{BBH}}={23.9}_{-8.6}^{+14.3},,{mathrm{Gpc}}^{-3},{mathrm{yr}}^{-1}$ for BBHs and ${{ mathcal R }}_{mathrm{BNS}}={320}_{-240}^{+490},,{mathrm{Gpc}}^{-3},{mathrm{yr}}^{-1}$ for binary neutron stars. We find that the BBH rate likely increases with redshift ($85 % $ credibility) but not faster than the star formation rate ($86 % $ credibility). Additionally, we examine recent exceptional events in the context of our population models, finding that the asymmetric masses of GW190412 and the high component masses of GW190521 are consistent with our models, but the low secondary mass of GW190814 makes it an outlier.
Fri, 01 Jan 2021 00:00:00 GMThttp://hdl.handle.net/11576/26887812021-01-01T00:00:00ZConstraints on Cosmic Strings Using Data from the Third Advanced LIGO–Virgo Observing Runhttp://hdl.handle.net/11576/2689276Titolo: Constraints on Cosmic Strings Using Data from the Third Advanced LIGO–Virgo Observing Run
Abstract: We search for gravitational-wave signals produced by cosmic strings in the Advanced LIGO and Virgo full O3 dataset. Search results are presented for gravitational waves produced by cosmic string loop features such as cusps, kinks, and, for the first time, kink-kink collisions. A template-based search for short-duration transient signals does not yield a detection. We also use the stochastic gravitational-wave background energy density upper limits derived from the O3 data to constrain the cosmic string tension
Gμ as a function of the number of kinks, or the number of cusps, for two cosmic string loop distribution models. Additionally, we develop and test a third model that interpolates between these two models. Our results improve upon the previous LIGO–Virgo constraints on Gμ by 1 to 2 orders of magnitude depending on the model that is tested. In particular, for the one-loop distribution model, we set the most competitive constraints to date: Gμ ≲ 4×10−15. In the case of cosmic strings formed at the end of inflation in the context of grand unified theories, these results challenge simple inflationary models.
Fri, 01 Jan 2021 00:00:00 GMThttp://hdl.handle.net/11576/26892762021-01-01T00:00:00ZDiving below the Spin-down Limit: Constraints on Gravitational Waves from the Energetic Young Pulsar PSR J0537-6910http://hdl.handle.net/11576/2688996Titolo: Diving below the Spin-down Limit: Constraints on Gravitational Waves from the Energetic Young Pulsar PSR J0537-6910
Abstract: We present a search for quasi-monochromatic gravitational-wave signals from the young, energetic X-ray pulsar PSR J0537−6910 using data from the second and third observing runs of LIGO and Virgo. The search is enabled by a contemporaneous timing ephemeris obtained using Neutron star Interior Composition Explorer (NICER) data. The NICER ephemeris has also been extended through 2020 October and includes three new glitches. PSR J0537−6910 has the largest spin-down luminosity of any pulsar and exhibits fRequent and strong glitches. Analyses of its long-term and interglitch braking indices provide intriguing evidence that its spin-down energy budget may include gravitational-wave emission from a time-varying mass quadrupole moment. Its 62 Hz rotation frequency also puts its possible gravitational-wave emission in the most sensitive band of the LIGO/Virgo detectors. Motivated by these considerations, we search for gravitational-wave emission at both once and twice the rotation frequency from PSR J0537−6910. We find no signal, however, and report upper limits. Assuming a rigidly rotating triaxial star, our constraints reach below the gravitational-wave spin-down limit for this star for the first time by more than a factor of 2 and limit gravitational waves from the l = m = 2 mode to account for less than 14% of the spin-down energy budget. The fiducial equatorial ellipticity is constrained to less than about 3 ×10−5, which is the third best constraint for any young pulsar.
Fri, 01 Jan 2021 00:00:00 GMThttp://hdl.handle.net/11576/26889962021-01-01T00:00:00Z