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Register a new userGW190425: Observation of a Compact Binary Coalescence with Total Mass $sim 3.4 M_{odot}$
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On 2019 April 25, the LIGO Livingston detector observed a compact binary coalescence with signal-to-noise ratio 12.9. The Virgo detector was also taking data that did not contribute to detection due to a low signal-to-noise ratio, but were used for subsequent parameter estimation. The 90% credible intervals for the component masses range from 1.12 to 2.52 $M_{odot}$ (1.45 to 1.88 $M_{odot}$ if we restrict the dimensionless component spin magnitudes to be smaller than 0.05). These mass parameters are consistent with the individual binary components being neutron stars. However, both the source-frame chirp mass $1.44^{+0.02}_{-0.02} M_{odot}$ and the total mass $3.4^{+0.3}_{-0.1},M_{odot}$ of this system are significantly larger than those of any other known binary neutron star system. The possibility that one or both binary components of the system are black holes cannot be ruled out from gravitational-wave data. We discuss possible origins of the system based on its inconsistency with the known Galactic binary neutron star population. Under the assumption that the signal was produced by a binary neutron star coalescence, the local rate of neutron star mergers is updated to $250-2810 text{Gpc}^{-3}text{yr}^{-1}$.
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In the case of zero-metal (population III or Pop III) stars, we show that the total mass of binary black holes from binary Pop III star evolution can be $sim 150 ,M_{odot}$, which agrees with the mass of the binary black hole GW190521 recently discovered by LIGO/Virgo. The event rate of such binary black hole mergers is estimated as 0.13--0.66$~(rho_{rm SFR}/(6times10^5~M_{odot}/{rm Mpc}^3))~Err_{rm sys}~{rm yr^{-1}~Gpc^{-3}}$, where $rho_{rm SFR}$ and $Err_{rm sys}$ are the cumulative comoving mass density of Pop III stars depending on star formation rate and the systematic errors depending on uncertainties in the Pop III binary parameters, respectively. The event rate in our fiducial model with $rho_{rm SFR}=6times10^5~M_{odot}/{rm Mpc}^3$ and $ Err_{rm sys}=1$ is 0.13--0.66$~{rm yr^{-1}~Gpc^{-3}}$, which is consistent with the observed value of 0.02--0.43$~{rm yr^{-1}~Gpc^{-3}}$.
On June 8, 2017 at 02:01:16.49 UTC, a gravitational-wave signal from the merger of two stellar-mass black holes was observed by the two Advanced LIGO detectors with a network signal-to-noise ratio of 13. This system is the lightest black hole binary so far observed, with component masses $12^{+7}_{-2},M_odot$ and $7^{+2}_{-2},M_odot$ (90% credible intervals). These lie in the range of measured black hole masses in low-mass X-ray binaries, thus allowing us to compare black holes detected through gravitational waves with electromagnetic observations. The sources luminosity distance is $340^{+140}_{-140}$ Mpc, corresponding to redshift $0.07^{+0.03}_{-0.03}$. We verify that the signal waveform is consistent with the predictions of general relativity.
On May 21, 2019 at 03:02:29 UTC Advanced LIGO and Advanced Virgo observed a short duration gravitational-wave signal, GW190521, with a three-detector network signal-to-noise ratio of 14.7, and an estimated false-alarm rate of 1 in 4900 yr using a search sensitive to generic transients. If GW190521 is from a quasicircular binary inspiral, then the detected signal is consistent with the merger of two black holes with masses of $85^{+21}_{-14} M_{odot}$ and $66^{+17}_{-18} M_{odot}$ (90 % credible intervals). We infer that the primary black hole mass lies within the gap produced by (pulsational) pair-instability supernova processes, and has only a 0.32 % probability of being below $65 M_{odot}$. We calculate the mass of the remnant to be $142^{+28}_{-16} M_{odot}$, which can be considered an intermediate mass black hole (IMBH). The luminosity distance of the source is $5.3^{+2.4}_{-2.6}$ Gpc, corresponding to a redshift of $0.82^{+0.28}_{-0.34}$. The inferred rate of mergers similar to GW190521 is $0.13^{+0.30}_{-0.11},mathrm{Gpc}^{-3},mathrm{yr}^{-1}$.
We report the observation of gravitational waves from a binary-black-hole coalescence during the first two weeks of LIGOs and Virgos third observing run. The signal was recorded on April 12, 2019 at 05:30:44 UTC with a network signal-to-noise ratio of 19. The binary is different from observations during the first two observing runs most notably due to its asymmetric masses: a ~30 solar mass black hole merged with a ~8 solar mass black hole companion. The more massive black hole rotated with a dimensionless spin magnitude between 0.22 and 0.60 (90% probability). Asymmetric systems are predicted to emit gravitational waves with stronger contributions from higher multipoles, and indeed we find strong evidence for gravitational radiation beyond the leading quadrupolar order in the observed signal. A suite of tests performed on GW190412 indicates consistency with Einsteins general theory of relativity. While the mass ratio of this system differs from all previous detections, we show that it is consistent with the population model of stellar binary black holes inferred from the first two observing runs.
The detection of an unexpected $sim 2.5 M_{odot}$ component in the gravitational wave event GW190814 has puzzled the community of High-Energy astrophysicists, since in the absence of further information it is not clear whether this is the heaviest neutron star ever detected or either the lightest black hole known, of a kind absent in the local neighbourhood. We show in this work a few possibilities for a model of the former, in the framework of three different quark matter models with and without anisotropy in the interior pressure. As representatives of classes of exotic solutions, we show that even though the stellar sequences may reach this ballpark, it is difficult to fulfill simultaneously the constraint of the radius as measured by the NICER team for the pulsar PSR J0030+0451. Thus, and assuming both measurements stand, compact neutron stars can not be all made of self-bound quark matter, even within anisotropic solutions which boost the maximum mass well above the $sim 2.5 M_{odot}$ figure. We also point out that a very massive compact star will limit the absolute maximum matter density in the present Universe to be less than 6 times the nuclear saturation value.
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