Observing Double White Dwarfs with the Lunar GW Antenna

TL;DR

The paper assesses the Lunar Gravitational-Wave Antenna (LGWA), a Moon-based detector designed to observe decihertz gravitational waves from short-period double white dwarfs. It combines SeBa-based population synthesis, SFH convolved populations, and Fisher-matrix analyses with GWFish and Legwork to forecast detection and localization capabilities for both Galactic inspirals and extragalactic mergers. The study finds that over a 10-year mission LGWA could detect roughly 30 Galactic inspiraling DWDs and about 10 extragalactic mergers under a realistic (contact) merger scenario, with localization precision enabling host identification in many cases. These results demonstrate the unique potential of decihertz GW detectors to study SN Ia progenitors, calibrate cosmic distances via standard sirens, and probe dense-matter physics in the late-stage evolution of DWDs.

Abstract

The Lunar Gravitational Wave Antenna (LGWA) is a proposed gravitational-wave detector that will observe in the decihertz (dHz) frequency region. In this band, binary white dwarf systems are expected to merge, emitting gravitational waves. Detecting this emission opens new perspectives for understanding the Type Ia supernova progenitors and for investigating dense matter physics. In this paper, we present the capabilities of LGWA to detect and localize short-period double white dwarfs in terms of sky locations and distances. The analysis employs realistic spatial distributions and merger rates, as well as binary-mass distributions informed by population-synthesis models. The simulated population of double white dwarfs is generated using the SeBa stellar-evolution code, coupled with dedicated sampling algorithms. The performance of the LGWA detector, both in terms of signal detectability and parameter estimation, is assessed using standard gravitational-wave data analysis techniques, including Fisher matrix methods, as implemented in the GWFish and Legwork codes. The analysis indicates that, over 10 years of observation, LGWA could detect approximately 30 monochromatic Galactic sources and 10 extragalactic mergers, demonstrating the unique potential of decihertz gravitational-wave detectors to access and characterize extragalactic DWD populations. This will open new avenues for understanding Type Ia supernova progenitors and the physics of DWDs.

Figures (12)

• Figure 1: Dependence of the merging frequency with respect to the component masses for the Roche scenario (upper semiplane) and contact scenario (lower semiplane). The reported population (red for $m_1+m_2>M_\text{Ch}$ and gray for $m_1+m_2<M_\text{Ch}$) is presented in Sect. \ref{['sec:population']}, and corresponds to the simulated Milky Way DWD population.
• Figure 2: Star formation history of the two Galaxy disks, with data from SFH_disks for comparison. The normalization of the SFH is not used for the convolution procedure, but the ratio between normalizations is a byproduct of the entire simulation of the DWD population.
• Figure 3: Extragalactic population: the plot shows the position of the galaxies from the HyperLeda catalog; the colorbar indicates the luminosity distance, and the size of every dot represents the rate associated with the relative galaxy. For graphical clarity, the size $s$ of the markers are related to the SN Ia rate $r$ through the relation $s\propto \log(r+1)$. Note the incompleteness of the population along the Galactic plane (green line, the green dot represents the Galactic center).
• Figure 4: Cumulative distribution of the S/N for the three MW components (colored) and total (black) over ten years of LGWA observation. The plot indicates the cumulative distribution, namely for each S/N threshold $\rho$ (x-axis) the counts (y-axis) provide the number of objects with the S/N larger than the threshold $\rho$. The power-law fits are also reported explicitly.
• Figure 5: Analysis of the super-Chandrasekhar merging MW population under Roche scenario. The three main plots represent the distribution of S/N, error on sky localization and relative error on luminosity distance for every MW component. Lower left plots: the left column represents the binaries elaborated with GWFish; the colored dots correspond to the elaborated objects with corresponding S/N, gray dots to rejected super-Chandrasekhar binaries and light-gray dots to rejected sub-Chandrasekhar binaries. The right column represents the $1\sigma$ fiducial volume of the elaborated population. The S/N colorscale is common for all the plots.