Bounding the photon mass with the dedispersed pulses of the Crab pulsar and FRB 180916B

Abstract

Tight limits on the photon mass have been set through analyzing the arrival time differences of photons with differentfrequencies originating from the same astrophysical source. However, all these constraints have relied on usingthe first-order Taylor expansion of the dispersion due to a nonzero photon mass. In this work, we present an analysisof the nonzero photon mass dispersion with the second-order derivative of Taylor series. If the arrival time delay correctedfor all known effects (including the first-order delay time due to the plasma and photon mass effects) is assumed to bedominated by the second-order term of the nonzero photon mass dispersion, a conservative upper limit on the photon mass can be estimated. Here we show that the dedispersed pulses with the second-order time delays from the Crab pulsar andthe fast radio burst FRB 180916B pose strict limits on the photon mass, i.e.,mγ,2 ≤ 5.7 × 10-46 kg ≃ 3.2 × 10-10 eV/c 2and mγ,2 ≤ 6.0 × 10-47 kg ≃ 3.4 × 10-11 eV/c 2, respectively.This is the first time to study the possible second-order photon mass effect.