Test of the Weak Equivalence Principle using LIGO observations of GW150914 and Fermi observations of GBM transient 150914

Understand

About 0.4s after the Laser Interferometer Gravitational-Wave Observatory (LIGO) detected a transient gravitational-wave (GW) signal GW150914, the Fermi Gamma-ray Burst Monitor (GBM) also found a weak electromagnetic transient (GBM transient 150914).

• Time and location coincidences favor a possible association between GW150904 and GBM transient 150914.
• Under this possible association, we adopt Fermi's electromagnetic (EM) localization and derive constraints on possible violations of the Weak Equivalence Principle (WEP) from the observations of two events.
• Our calculations are based on four comparisons: (1)The first is the comparison of the initial GWs detected at the two LIGO sites.