Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userThe Rate of Binary Black Hole Mergers Inferred from Advanced LIGO Observations Surrounding GW150914
105
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
A transient gravitational-wave signal, GW150914, was identified in the twin Advanced LIGO detectors on September 14, 2015 at 09:50:45 UTC. To assess the implications of this discovery, the detectors remained in operation with unchanged configurations over a period of 39 d around the time of the signal. At the detection statistic threshold corresponding to that observed for GW150914, our search of the 16 days of simultaneous two-detector observational data is estimated to have a false alarm rate (FAR) of $< 4.9 times 10^{-6} , mathrm{yr}^{-1}$, yielding a $p$-value for GW150914 of $< 2 times 10^{-7}$. Parameter estimation followup on this trigger identifies its source as a binary black hole (BBH) merger with component masses $(m_1, m_2) = left(36^{+5}_{-4},29^{+4}_{-4}right) , M_odot$ at redshift $z = 0.09^{+0.03}_{-0.04}$ (median and 90% credible range). Here we report on the constraints these observations place on the rate of BBH coalescences. Considering only GW150914, assuming that all BBHs in the Universe have the same masses and spins as this event, imposing a search FAR threshold of 1 per 100 years, and assuming that the BBH merger rate is constant in the comoving frame, we infer a 90% credible range of merger rates between $2$--$53 , mathrm{Gpc}^{-3} mathrm{yr}^{-1}$ (comoving frame). Incorporating all search triggers that pass a much lower threshold while accounting for the uncertainty in the astrophysical origin of each trigger, we estimate a higher rate, ranging from $13$--$600 , mathrm{Gpc}^{-3} mathrm{yr}^{-1}$ depending on assumptions about the BBH mass distribution. All together, our various rate estimates fall in the conservative range $2$--$600 , mathrm{Gpc}^{-3} mathrm{yr}^{-1}$.
rate research
Read More
Supplemental information for a Letter reporting the rate of binary black hole (BBH) coalescences inferred from 16 days of coincident Advanced LIGO observations surrounding the transient gravitational wave signal GW150914. In that work we reported various rate estimates whose 90% credible intervals fell in the range $2$--$600 , mathrm{Gpc}^{-3} mathrm{yr}^{-1}$. Here we give details of our method and computations, including information about our search pipelines, a derivation of our likelihood function for the analysis, a description of the astrophysical search trigger distribution expected from merging BBHs, details on our computational methods, a description of the effects and our model for calibration uncertainty, and an analytic method of estimating our detector sensitivity that is calibrated to our measurements.
We present results on the mass, spin, and redshift distributions with phenomenological population models using the ten binary black hole mergers detected in the first and second observing runs completed by Advanced LIGO and Advanced Virgo. We constrain properties of the binary black hole (BBH) mass spectrum using models with a range of parameterizations of the BBH mass and spin distributions. We find that the mass distribution of the more massive black hole in such binaries is well approximated by models with no more than 1% of black holes more massive than $45,M_odot$, and a power law index of $alpha = {1.3}^{+1.4}_{-1.7}$ (90% credibility). We also show that BBHs are unlikely to be composed of black holes with large spins aligned to the orbital angular momentum. Modelling the evolution of the BBH merger rate with redshift, we show that it is at or increasing with redshift with 93% probability. Marginalizing over uncertainties in the BBH population, we find robust estimates of the BBH merger rate density of $R = {53.2}^{+55.8}_{-28.2}$ Gpc$^{-3}$ yr$^{-1}$ (90% credibility). As the BBH catalog grows in future observing runs, we expect that uncertainties in the population model parameters will shrink, potentially providing insights into the formation of black holes via supernovae, binary interactions of massive stars, stellar cluster dynamics, and the formation history of black holes across cosmic time.
Fermi-Gamma-ray Burst Monitor observed a 1 s long gamma-ray signal (GW150914-GBM) starting 0.4 s after the first gravitational wave detection from the binary black hole merger GW150914. GW150914-GBM is consistent with a short gamma-ray burst origin; however, no unambiguous claims can be made as to the physical association of the two signals due to a combination of low gamma-ray flux and unfavorable location for Fermi-GBM. Here we answer the following question: if GW150914 and GW150914-GBM were associated, how many LIGO-Virgo binary black hole mergers would Fermi-GBM have to follow up to detect a second source? To answer this question, we perform simulated observations of binary black hole mergers with LIGO-Virgo and adopt different scenarios for gamma-ray emission from the literature. We calculate the ratio of simulated binary black hole mergers detected by LIGO-Virgo to the number of gamma-ray counterpart detections by Fermi-GBM, BBH-to-GRB ratio. A large majority of the models considered here predict a BBH-to-GRB ratio in the range of 5 to 20, but for optimistic cases can be as low as 2 or for pessimistic assumptions as high as 700. Hence we expect that the third observing run, with its high rate of binary black hole detections and assuming the absence of a joint detection, will provide strong constraints on the presented models.
We study the evolution of the binary black hole (BBH) mass distribution across cosmic time. The second gravitational-wave transient catalog (GWTC-2) from LIGO/Virgo contains BBH events out to redshifts $z sim 1$, with component masses in the range $sim5$--$80,M_odot$. In this catalog, the biggest black holes, with $m_1 gtrsim 45,M_odot$, are only found at the highest redshifts, $z gtrsim 0.4$. We ask whether the absence of high-mass BBH observations at low redshift indicates that the astrophysical BBH mass distribution evolves: the biggest BBHs only merge at high redshift, and cease merging at low redshift. Alternatively, this feature might be explained by gravitational-wave selection effects. Modeling the BBH primary mass spectrum as a power law with a sharp maximum mass cutoff (Truncated model), we find that the cutoff increases with redshift ($> 99.9%$ credibility). An abrupt cutoff in the mass spectrum is expected from (pulsational) pair instability supernova simulations; however, GWTC-2 is only consistent with a Truncated mass model if the location of the cutoff increases from $45^{+13}_{-5},M_odot$ at $z < 0.4$ to $80^{+16}_{-13},M_odot$ at $z > 0.4$. Alternatively, if the primary mass spectrum has a break in the power law (Broken power law) at ${38^{+15}_{-8},M_odot}$, rather than a sharp cutoff, the data are consistent with a non-evolving mass distribution. In this case, the overall rate of mergers, at all masses, increases with increasing redshift. Future observations will confidently distinguish between a sharp maximum mass cutoff that evolves with redshift and a non-evolving mass distribution with a gradual taper, such as a Broken power law. After $sim 100$ BBH merger observations, a continued absence of high-mass, low-redshift events would provide a clear signature that the mass distribution evolves with redshift.
We present results from a controlled numerical experiment investigating the effect of stellar density gas on the coalescence of binary black holes (BBHs) and the resulting gravitational waves (GWs). This investigation is motivated by the proposed stellar core fragmentation scenario for BBH formation and the associated possibility of an electromagnetic counterpart to a BBH GW event. We employ full numerical relativity coupled with general-relativistic hydrodynamics and set up a $30 + 30 M_odot$ BBH (motivated by GW150914) inside gas with realistic stellar densities. Our results show that at densities $rho gtrsim 10^6 - 10^7 , mathrm{g , cm}^{-3}$ dynamical friction between the BHs and gas changes the coalescence dynamics and the GW signal in an unmistakable way. We show that for GW150914, LIGO observations conclusively rule out BBH coalescence inside stellar gas of $rho gtrsim 10^7 , mathrm{g,cm}^{-3}$. Typical densities in the collapsing cores of massive stars are in excess of this density. This excludes the fragmentation scenario for the formation of GW150914.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
