321 research outputs found
An Early-warning System for Electromagnetic Follow-up of Gravitational-wave Events
Binary neutron stars (BNSs) will spend ≃10–15 minutes in the band of Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo detectors at design sensitivity. Matched-filtering of gravitational-wave (GW) data could in principle accumulate enough signal-to-noise ratio (S/N) to identify a forthcoming event tens of seconds before the companions collide and merge. Here we report on the design and testing of an early-warning GW detection pipeline. Early-warning alerts can be produced for sources that are at low enough redshift so that a large enough S/N accumulates ~10–60 s before merger. We find that about 7% (49%) of the total detectable BNS mergers will be detected 60 s (10 s) before the merger. About 2% of the total detectable BNS mergers will be detected before merger and localized to within 100 deg² (90% credible interval). Coordinated observing by several wide-field telescopes could capture the event seconds before or after the merger. LIGO–Virgo detectors at design sensitivity could facilitate observing at least one event at the onset of merger
Structural and Histone Binding Ability Characterizations of Human PWWP Domains
The PWWP domain was first identified as a structural motif of 100-130 amino acids in the WHSC1 protein and predicted to be a protein-protein interaction domain. It belongs to the Tudor domain 'Royal Family', which consists of Tudor, chromodomain, MBT and PWWP domains. While Tudor, chromodomain and MBT domains have long been known to bind methylated histones, PWWP was shown to exhibit histone binding ability only until recently.The PWWP domain has been shown to be a DNA binding domain, but sequence analysis and previous structural studies show that the PWWP domain exhibits significant similarity to other 'Royal Family' members, implying that the PWWP domain has the potential to bind histones. In order to further explore the function of the PWWP domain, we used the protein family approach to determine the crystal structures of the PWWP domains from seven different human proteins. Our fluorescence polarization binding studies show that PWWP domains have weak histone binding ability, which is also confirmed by our NMR titration experiments. Furthermore, we determined the crystal structures of the BRPF1 PWWP domain in complex with H3K36me3, and HDGF2 PWWP domain in complex with H3K79me3 and H4K20me3.PWWP proteins constitute a new family of methyl lysine histone binders. The PWWP domain consists of three motifs: a canonical β-barrel core, an insertion motif between the second and third β-strands and a C-terminal α-helix bundle. Both the canonical β-barrel core and the insertion motif are directly involved in histone binding. The PWWP domain has been previously shown to be a DNA binding domain. Therefore, the PWWP domain exhibits dual functions: binding both DNA and methyllysine histones.This article can also be viewed as an enhanced version in which the text of the article is integrated with interactive 3D representations and animated transitions. Please note that a web plugin is required to access this enhanced functionality. Instructions for the installation and use of the web plugin are available in Text S1
An early warning system for electromagnetic follow-up of gravitational-wave events
Binary neutron stars (BNSs) will spend -- 15 minutes in the band
of Advanced LIGO and Virgo detectors at design sensitivity. Matched-filtering
of gravitational-wave (GW) data could in principle accumulate enough
signal-to-noise ratio (SNR) to identify a forthcoming event tens of seconds
before the companions collide and merge. Here we report on the design and
testing of an early warning gravitational-wave detection pipeline. Early
warning alerts can be produced for sources that are at low enough redshift so
that a large enough SNR accumulates before merger. We
find that about 7% (respectively, 49%) of the total detectable BNS mergers will
be detected () before the merger. About 2% of the
total detectable BNS mergers will be detected before merger and localized to
within (90% credible interval). Coordinated observing
by several wide-field telescopes could capture the event seconds before or
after the merger. LIGO-Virgo detectors at design sensitivity could facilitate
observing at least one event at the onset of merger.Comment: small update in numbers caused by using a more updated local BNS rate
estimat
Population of Merging Compact Binaries Inferred Using Gravitational Waves through GWTC-3
We report on the population properties of compact binary mergers inferred from gravitational-wave observations of these systems during the first three LIGO-Virgo observing runs. The Gravitational-Wave Transient Catalog 3 (GWTC-3) contains signals consistent with three classes of binary mergers: binary black hole, binary neutron star, and neutron star-black hole mergers. We infer the binary neutron star merger rate to be between 10 and 1700 Gpc-3 yr-1 and the neutron star-black hole merger rate to be between 7.8 and 140 Gpc-3 yr-1, assuming a constant rate density in the comoving frame and taking the union of 90% credible intervals for methods used in this work. We infer the binary black hole merger rate, allowing for evolution with redshift, to be between 17.9 and 44 Gpc-3 yr-1 at a fiducial redshift (z=0.2). The rate of binary black hole mergers is observed to increase with redshift at a rate proportional to (1+z)κ with κ=2.9-1.8+1.7 for z≲1. Using both binary neutron star and neutron star-black hole binaries, we obtain a broad, relatively flat neutron star mass distribution extending from 1.2-0.2+0.1 to 2.0-0.3+0.3M⊙. We confidently determine that the merger rate as a function of mass sharply declines after the expected maximum neutron star mass, but cannot yet confirm or rule out the existence of a lower mass gap between neutron stars and black holes. We also find the binary black hole mass distribution has localized over- and underdensities relative to a power-law distribution, with peaks emerging at chirp masses of 8.3-0.5+0.3 and 27.9-1.8+1.9M⊙. While we continue to find that the mass distribution of a binary's more massive component strongly decreases as a function of primary mass, we observe no evidence of a strongly suppressed merger rate above approximately 60M⊙, which would indicate the presence of a upper mass gap. Observed black hole spins are small, with half of spin magnitudes below χi≈0.25. While the majority of spins are preferentially aligned with the orbital angular momentum, we infer evidence of antialigned spins among the binary population. We observe an increase in spin magnitude for systems with more unequal-mass ratio. We also observe evidence of misalignment of spins relative to the orbital angular momentum
The population of merging compact binaries inferred using gravitational waves through GWTC-3
We report on the population properties of 76 compact binary mergers detected with gravitational waves below a false alarm rate of 1 per year through GWTC-3. The catalog contains three classes of binary mergers: BBH, BNS, and NSBH mergers. We infer the BNS merger rate to be between 10 and 1700 and the NSBH merger rate to be between 7.8 and 140 , assuming a constant rate density versus comoving volume and taking the union of 90% credible intervals for methods used in this work. Accounting for the BBH merger rate to evolve with redshift, we find the BBH merger rate to be between 17.9 and 44 at a fiducial redshift (z=0.2). We obtain a broad neutron star mass distribution extending from to . We can confidently identify a rapid decrease in merger rate versus component mass between neutron star-like masses and black-hole-like masses, but there is no evidence that the merger rate increases again before 10 . We also find the BBH mass distribution has localized over- and under-densities relative to a power law distribution. While we continue to find the mass distribution of a binary's more massive component strongly decreases as a function of primary mass, we observe no evidence of a strongly suppressed merger rate above . The rate of BBH mergers is observed to increase with redshift at a rate proportional to with for . Observed black hole spins are small, with half of spin magnitudes below . We observe evidence of negative aligned spins in the population, and an increase in spin magnitude for systems with more unequal mass ratio
All-sky search for long-duration gravitational-wave bursts in the third Advanced LIGO and Advanced Virgo run
After the detection of gravitational waves from compact binary coalescences, the search for transient gravitational-wave signals with less well-defined waveforms for which matched filtering is not well suited is one of the frontiers for gravitational-wave astronomy. Broadly classified into “short” ≲1 s and “long” ≳1 s duration signals, these signals are expected from a variety of astrophysical processes, including non-axisymmetric deformations in magnetars or eccentric binary black hole coalescences. In this work, we present a search for long-duration gravitational-wave transients from Advanced LIGO and Advanced Virgo’s third observing run from April 2019 to March 2020. For this search, we use minimal assumptions for the sky location, event time, waveform morphology, and duration of the source. The search covers the range of 2–500 s in duration and a frequency band of 24–2048 Hz. We find no significant triggers within this parameter space; we report sensitivity limits on the signal strength of gravitational waves characterized by the root-sum-square amplitude hrss as a function of waveform morphology. These hrss limits improve upon the results from the second observing run by an average factor of 1.8
Constraints on dark photon dark matter using data from LIGO's and Virgo's third observing run
We present a search for dark photon dark matter that could couple to
gravitational-wave interferometers using data from Advanced LIGO and Virgo's
third observing run. To perform this analysis, we use two methods, one based on
cross-correlation of the strain channels in the two nearly aligned LIGO
detectors, and one that looks for excess power in the strain channels of the
LIGO and Virgo detectors. The excess power method optimizes the Fourier
Transform coherence time as a function of frequency, to account for the
expected signal width due to Doppler modulations. We do not find any evidence
of dark photon dark matter with a mass between eV/, which corresponds to frequencies between 10-2000
Hz, and therefore provide upper limits on the square of the minimum coupling of
dark photons to baryons, i.e. dark matter. For the
cross-correlation method, the best median constraint on the squared coupling is
at eV/; for the
other analysis, the best constraint is at eV/. These limits improve upon those obtained
in direct dark matter detection experiments by a factor of for
eV/, and are, in absolute terms, the
most stringent constraint so far in a large mass range eV/.Comment: 20 pages, 7 figure
Search for anisotropic gravitational-wave backgrounds using data from Advanced LIGO and Advanced Virgo's first three observing runs
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 {\tt 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 and on the
(normalized) gravitational-wave energy density spectrum from extended sources,
ranging from , depending on direction () and spectral index
(). These limits improve upon previous limits by factors of . 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 a factor of
improvement compared to previous stochastic radiometer searches.Comment: 23 Pages, 9 Figure
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