Ultra-low-frequency electromagnetic waves as signals and special counterparts of gravitational waves (from binary mergers) having tensorial and possible nontensorial polarizations

Abstract

Gravitational waves (GWs, from binary merger) interacting with super-strong magnetic fields of the neutron star (in the same binary system), would lead to perturbed electromagnetic waves [EMWs, in the same frequencies of these GWs, partially in the ultra-low-frequency (ULF) band for the EMWs]. Such perturbed ULF-EMWs are not only the signals, but also a new type of special EM counterparts of the GWs. Here, generation of the perturbed ULF-EMWs is investigated for the first time, and the strengths of their magnetic components are estimated to be around 10^{-12}Tesla to 10^{-17}Tesla (in fISCO) at the Earth for various cases [not including the influence of interstellar medium (ISM)].The components with higher frequencies of the ULF-EMWs (e.g., especially produced by the GWs of the post-merger stage) above 1.8kHz (typical plasma frequency around solar system in the Milky way), could propagate through the ISM from the source until the Earth, and the perturbed ULF-EMWs will be reprocessed before they arrived at the Earth due to the ISM. Also, the waveforms of the perturbed ULF-EMWs will be modified into shapes different but related to the waveforms of the GWs, by the amplification process during the binary mergers which could amplify the magnetic fields into 10^{12}Tesla or even higher. Specific connection relationships between the polarizations of the perturbed ULF-EMWs and the polarizations (tensorial and possible nontensorial) of the GWs of binary mergers, are also addressed here. Characteristic properties of the perturbed ULF-EMWs (which would bring us some different new information of fundamental properties of the gravity and Universe) will be very helpful for extracting the signals from background noise for possible observations in the future.