GPS constellation search for exotic physics messengers coincident with the binary neutron star merger GW170817

Abstract

The Global Positioning System (GPS) includes a continuously operating, planet-scale network of atomic clocks that, beyond navigation and time dissemination, enables precision tests of fundamental physics. Here we use GPS carrier phase archival data to perform a retrospective search for exotic low-mass fields (ELFs) that might be emitted by the binary neutron-star merger GW170817, complementing gravitational wave and electromagnetic modalitiesnin multi-messenger astronomy. Such ultra-relativistic fields would imprint a dispersive, anti-chirp signature in clock-frequency time series, delayed with respect to the LIGO-Virgo gravitational wave detection. We construct network-median pseudo-frequency data from eighteen Rb satellite clocks referenced to a terrestrial hydrogen maser and conduct a template-bank search spanning ELF pulse duration, arrival delay, and characteristic frequency. No statistically significant signal is observed after accounting for noise statistics and template-bank trials. We derive 95\% confidence-level lower bounds on the interaction energy scale $Λ_α$ of quadratic couplings driving variations in electromagnetic fine-structure constant. These limits improve upon existing astrophysical and gravity-test constraints across the ELF-energy range $\approx10^{-18}$--$10^{-14}\,\mathrm{eV}$. This demonstrates that mature global satellite-clock networks provide an observational capability for retrospective, multi-messenger searches for new physics using decades of archival timing data.

Figures (7)

• Figure 1: A burst of exotic low-mass fields (ELFs) propagates with the group velocity $v_g \lesssim c$ lagging behind the gravitational wave burst traveling at speed of light, $c$. The arriving ELF wave-packet exhibits a characteristic frequency anti-chirp dailey2020ELF.Concept, because of the faster propagation of the more energetic ELF components. GPS constellation atomic clocks serve as a distributed quantum sensor. The GPS constellation image is adapted from the GPS.gov public domain image.
• Figure 2: GPS network median clock pseudo-frequency (PF) for Aug. 17, 2017. LIGO-Virgo gravitational wave (GW) trigger Abbott_multimessenger_2017 (black vertical line) is at $45,682\,\mathrm{s}$ from the start of the GPS day of Aug. 17, 2017. Network median is taken over $18$ Rb clocks of the GPS network. The difference between GPS and UTC time scales here was $18\,\mathrm{s}$. Visually there is no obvious change in noise behavior after the GW trigger.
• Figure 3: Standard deviations $\sigma_w$ of GPS network median pseudo-frequencies for Aug. 16 and 17, 2017. GW trigger on Aug. 17, 2017, is shown with the black vertical line. Standard deviations were computed over 173-s wide windows. The GW-event day shows variance behavior consistent with the previous day control period, with no structure indicative of an ELF signal.
• Figure 4: Representative GPS constraints on ultralight scalar fields from GW170817. Shown are 95% confidence-level (CL) lower bounds on the energy scale $\Lambda_\alpha$ governing quadratic couplings of ultralight scalar fields causing variations in fine-structure constant. These are derived from the non-observation of an exotic-field signal temporally correlated with the binary neutron star merger GW170817. Bounds are presented as a function of the scalar-field energy $\varepsilon_0$ for a representative GW--ELF time delay $\delta t = 15{,}000~\mathrm{s}$ and initial pulse durations $\tau_0$ spanning $500$--$7{,}000\,\mathrm{s}$. The blue hatched region is excluded by our work. Existing constraints from stellar emissivity and precision tests of gravity are shown for comparison (pink shaded region). The GPS-based limits extend well beyond all previous terrestrial and astrophysical bounds across much of the accessible parameter space, establishing global satellite atomic-clock networks as the most sensitive probes of relativistic ultralight scalar transients in this energy range.
• Figure 5: Standard deviation in a window, $\sigma_w$, of the network-median pseudo-frequency data \ref{['Eq:Net_Med_Data']} for the GPS network of $^{87}\mathrm{Rb}$ clocks on August 15, 16, and 17, 2017. The GW trigger at $45{,}682~\mathrm{s}$ from the start of August 17, 2017 (GPST), is indicated by the black vertical line. For each day, the data set is partitioned into $W = 498$ windows, each containing $N_p = 173$ data points, and $\sigma_w$ is computed within each window.