Parameter estimation on gravitational waves from neutron-star binaries with spinning components (1508.05336v3)

Abstract: Inspiraling binary neutron stars are expected to be one of the most significant sources of gravitational-wave signals for the new generation of advanced ground-based detectors. We investigate how well we could hope to measure properties of these binaries using the Advanced LIGO detectors, which began operation in September 2015. We study an astrophysically motivated population of sources (binary components with masses $1.2~\mathrm{M}\odot$--$1.6~\mathrm{M}\odot$ and spins of less than $0.05$) using the full LIGO analysis pipeline. While this simulated population covers the observed range of potential binary neutron-star sources, we do not exclude the possibility of sources with parameters outside these ranges; given the existing uncertainty in distributions of mass and spin, it is critical that analyses account for the full range of possible mass and spin configurations. We find that conservative prior assumptions on neutron-star mass and spin lead to average fractional uncertainties in component masses of $\sim 16\%$, with little constraint on spins (the median $90\%$ upper limit on the spin of the more massive component is $\sim 0.7$). Stronger prior constraints on neutron-star spins can further constrain mass estimates, but only marginally. However, we find that the sky position and luminosity distance for these sources are not influenced by the inclusion of spin; therefore, if LIGO detects a low-spin population of BNS sources, less computationally expensive results calculated neglecting spin will be sufficient for guiding electromagnetic follow-up.

Parameter Estimation on Gravitational Waves from Neutron-Star Binaries with Spinning Components

In this paper, the authors address the challenges associated with precise parameter estimation of gravitational waves (GWs) emanating from inspiraling binary neutron stars (BNS) possessing spinning components. The focus is on analyses conducted with the Advanced LIGO detectors during their initial phase of operation in 2015. A key contribution is the investigation into how well component masses and spin parameters of BNS can be measured under real observational conditions, considering prior constraints and uncertainties.

Methodological Framework

The paper utilizes a simulated population of binary neutron stars, with component masses ranging between 1.2 solar masses to 1.6 solar masses and spins less than 0.05. The authors employ LALI NFERENCE, a Bayesian inference library, alongside specific sampling algorithms such as LALI NFERENCE_NEST and LALI NFERENCE_MCMC, to evaluate posterior probability density functions concerning source parameters. A significant aspect of this work is the analysis using waveforms that incorporate the effects of neutron-star spin, thereby addressing parameter estimation using models that account for spin-specific physical phenomena.

Results

The researchers reveal that conservative priors on neutron-star mass and spin lead to average uncertainties in mass measurements at around 16%, with a 90% upper limit on the spin of the more massive component at approximately 0.7. They demonstrate that spin has negligible influence on extrinsic parameters like sky position and luminosity distance of BNS events. Importantly, this finding suggests that if LIGO observes a population of low-spin BNS, less computationally intensive analyses that neglect spin might suffice for certain applications, such as directing electromagnetic follow-up.

Implications

The implications of this research touch on both computational aspects and astrophysical observations. On the computational side, the paper underscores the increased computational demand of incorporating spin in detailed GW waveform models, which affects the latency and feasibility of real-time analyses. Astrophysically, the findings highlight the challenges in accurately resolving neutron-star spins and their effects due to the inherent degeneracies with mass parameters. This becomes crucial when characterizing the nature of compact-object binaries or when distinguishing between neutron-star and neutron-star-black-hole systems.

Future Directions

In future developments, enhancing the computational efficiency of waveform generation and data analysis remains a priority. Techniques such as reduced-order modeling and efficient sampling algorithms could significantly mitigate computation costs. Moreover, with advancements in detector sensitivity, the prospect of observing more diverse spin magnitudes and orientations remains a stimulating avenue for ongoing research. Continued improvements in parameter estimation will be vital for the broader agenda of multimessenger astronomy and for deeper insights into the physics governing binary neutron-star coalescences.

The authors provide a pivotal platform for ongoing exploration in the parameter estimation of GW sources, paving the way for more precise modeling frameworks and methodologies in the field of gravitational-wave astronomy.